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Linux/mm/memory.c

  1 /*
  2  *  linux/mm/memory.c
  3  *
  4  *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
  5  */
  6 
  7 /*
  8  * demand-loading started 01.12.91 - seems it is high on the list of
  9  * things wanted, and it should be easy to implement. - Linus
 10  */
 11 
 12 /*
 13  * Ok, demand-loading was easy, shared pages a little bit tricker. Shared
 14  * pages started 02.12.91, seems to work. - Linus.
 15  *
 16  * Tested sharing by executing about 30 /bin/sh: under the old kernel it
 17  * would have taken more than the 6M I have free, but it worked well as
 18  * far as I could see.
 19  *
 20  * Also corrected some "invalidate()"s - I wasn't doing enough of them.
 21  */
 22 
 23 /*
 24  * Real VM (paging to/from disk) started 18.12.91. Much more work and
 25  * thought has to go into this. Oh, well..
 26  * 19.12.91  -  works, somewhat. Sometimes I get faults, don't know why.
 27  *              Found it. Everything seems to work now.
 28  * 20.12.91  -  Ok, making the swap-device changeable like the root.
 29  */
 30 
 31 /*
 32  * 05.04.94  -  Multi-page memory management added for v1.1.
 33  *              Idea by Alex Bligh (alex@cconcepts.co.uk)
 34  *
 35  * 16.07.99  -  Support of BIGMEM added by Gerhard Wichert, Siemens AG
 36  *              (Gerhard.Wichert@pdb.siemens.de)
 37  *
 38  * Aug/Sep 2004 Changed to four level page tables (Andi Kleen)
 39  */
 40 
 41 #include <linux/kernel_stat.h>
 42 #include <linux/mm.h>
 43 #include <linux/hugetlb.h>
 44 #include <linux/mman.h>
 45 #include <linux/swap.h>
 46 #include <linux/highmem.h>
 47 #include <linux/pagemap.h>
 48 #include <linux/ksm.h>
 49 #include <linux/rmap.h>
 50 #include <linux/export.h>
 51 #include <linux/delayacct.h>
 52 #include <linux/init.h>
 53 #include <linux/writeback.h>
 54 #include <linux/memcontrol.h>
 55 #include <linux/mmu_notifier.h>
 56 #include <linux/kallsyms.h>
 57 #include <linux/swapops.h>
 58 #include <linux/elf.h>
 59 #include <linux/gfp.h>
 60 #include <linux/migrate.h>
 61 #include <linux/string.h>
 62 #include <linux/dma-debug.h>
 63 #include <linux/debugfs.h>
 64 
 65 #include <asm/io.h>
 66 #include <asm/pgalloc.h>
 67 #include <asm/uaccess.h>
 68 #include <asm/tlb.h>
 69 #include <asm/tlbflush.h>
 70 #include <asm/pgtable.h>
 71 
 72 #include "internal.h"
 73 
 74 #ifdef LAST_CPUPID_NOT_IN_PAGE_FLAGS
 75 #warning Unfortunate NUMA and NUMA Balancing config, growing page-frame for last_cpupid.
 76 #endif
 77 
 78 #ifndef CONFIG_NEED_MULTIPLE_NODES
 79 /* use the per-pgdat data instead for discontigmem - mbligh */
 80 unsigned long max_mapnr;
 81 struct page *mem_map;
 82 
 83 EXPORT_SYMBOL(max_mapnr);
 84 EXPORT_SYMBOL(mem_map);
 85 #endif
 86 
 87 /*
 88  * A number of key systems in x86 including ioremap() rely on the assumption
 89  * that high_memory defines the upper bound on direct map memory, then end
 90  * of ZONE_NORMAL.  Under CONFIG_DISCONTIG this means that max_low_pfn and
 91  * highstart_pfn must be the same; there must be no gap between ZONE_NORMAL
 92  * and ZONE_HIGHMEM.
 93  */
 94 void * high_memory;
 95 
 96 EXPORT_SYMBOL(high_memory);
 97 
 98 /*
 99  * Randomize the address space (stacks, mmaps, brk, etc.).
100  *
101  * ( When CONFIG_COMPAT_BRK=y we exclude brk from randomization,
102  *   as ancient (libc5 based) binaries can segfault. )
103  */
104 int randomize_va_space __read_mostly =
105 #ifdef CONFIG_COMPAT_BRK
106                                         1;
107 #else
108                                         2;
109 #endif
110 
111 static int __init disable_randmaps(char *s)
112 {
113         randomize_va_space = 0;
114         return 1;
115 }
116 __setup("norandmaps", disable_randmaps);
117 
118 unsigned long zero_pfn __read_mostly;
119 unsigned long highest_memmap_pfn __read_mostly;
120 
121 /*
122  * CONFIG_MMU architectures set up ZERO_PAGE in their paging_init()
123  */
124 static int __init init_zero_pfn(void)
125 {
126         zero_pfn = page_to_pfn(ZERO_PAGE(0));
127         return 0;
128 }
129 core_initcall(init_zero_pfn);
130 
131 
132 #if defined(SPLIT_RSS_COUNTING)
133 
134 void sync_mm_rss(struct mm_struct *mm)
135 {
136         int i;
137 
138         for (i = 0; i < NR_MM_COUNTERS; i++) {
139                 if (current->rss_stat.count[i]) {
140                         add_mm_counter(mm, i, current->rss_stat.count[i]);
141                         current->rss_stat.count[i] = 0;
142                 }
143         }
144         current->rss_stat.events = 0;
145 }
146 
147 static void add_mm_counter_fast(struct mm_struct *mm, int member, int val)
148 {
149         struct task_struct *task = current;
150 
151         if (likely(task->mm == mm))
152                 task->rss_stat.count[member] += val;
153         else
154                 add_mm_counter(mm, member, val);
155 }
156 #define inc_mm_counter_fast(mm, member) add_mm_counter_fast(mm, member, 1)
157 #define dec_mm_counter_fast(mm, member) add_mm_counter_fast(mm, member, -1)
158 
159 /* sync counter once per 64 page faults */
160 #define TASK_RSS_EVENTS_THRESH  (64)
161 static void check_sync_rss_stat(struct task_struct *task)
162 {
163         if (unlikely(task != current))
164                 return;
165         if (unlikely(task->rss_stat.events++ > TASK_RSS_EVENTS_THRESH))
166                 sync_mm_rss(task->mm);
167 }
168 #else /* SPLIT_RSS_COUNTING */
169 
170 #define inc_mm_counter_fast(mm, member) inc_mm_counter(mm, member)
171 #define dec_mm_counter_fast(mm, member) dec_mm_counter(mm, member)
172 
173 static void check_sync_rss_stat(struct task_struct *task)
174 {
175 }
176 
177 #endif /* SPLIT_RSS_COUNTING */
178 
179 #ifdef HAVE_GENERIC_MMU_GATHER
180 
181 static int tlb_next_batch(struct mmu_gather *tlb)
182 {
183         struct mmu_gather_batch *batch;
184 
185         batch = tlb->active;
186         if (batch->next) {
187                 tlb->active = batch->next;
188                 return 1;
189         }
190 
191         if (tlb->batch_count == MAX_GATHER_BATCH_COUNT)
192                 return 0;
193 
194         batch = (void *)__get_free_pages(GFP_NOWAIT | __GFP_NOWARN, 0);
195         if (!batch)
196                 return 0;
197 
198         tlb->batch_count++;
199         batch->next = NULL;
200         batch->nr   = 0;
201         batch->max  = MAX_GATHER_BATCH;
202 
203         tlb->active->next = batch;
204         tlb->active = batch;
205 
206         return 1;
207 }
208 
209 /* tlb_gather_mmu
210  *      Called to initialize an (on-stack) mmu_gather structure for page-table
211  *      tear-down from @mm. The @fullmm argument is used when @mm is without
212  *      users and we're going to destroy the full address space (exit/execve).
213  */
214 void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, unsigned long start, unsigned long end)
215 {
216         tlb->mm = mm;
217 
218         /* Is it from 0 to ~0? */
219         tlb->fullmm     = !(start | (end+1));
220         tlb->need_flush_all = 0;
221         tlb->start      = start;
222         tlb->end        = end;
223         tlb->need_flush = 0;
224         tlb->local.next = NULL;
225         tlb->local.nr   = 0;
226         tlb->local.max  = ARRAY_SIZE(tlb->__pages);
227         tlb->active     = &tlb->local;
228         tlb->batch_count = 0;
229 
230 #ifdef CONFIG_HAVE_RCU_TABLE_FREE
231         tlb->batch = NULL;
232 #endif
233 }
234 
235 static void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb)
236 {
237         tlb->need_flush = 0;
238         tlb_flush(tlb);
239 #ifdef CONFIG_HAVE_RCU_TABLE_FREE
240         tlb_table_flush(tlb);
241 #endif
242 }
243 
244 static void tlb_flush_mmu_free(struct mmu_gather *tlb)
245 {
246         struct mmu_gather_batch *batch;
247 
248         for (batch = &tlb->local; batch; batch = batch->next) {
249                 free_pages_and_swap_cache(batch->pages, batch->nr);
250                 batch->nr = 0;
251         }
252         tlb->active = &tlb->local;
253 }
254 
255 void tlb_flush_mmu(struct mmu_gather *tlb)
256 {
257         if (!tlb->need_flush)
258                 return;
259         tlb_flush_mmu_tlbonly(tlb);
260         tlb_flush_mmu_free(tlb);
261 }
262 
263 /* tlb_finish_mmu
264  *      Called at the end of the shootdown operation to free up any resources
265  *      that were required.
266  */
267 void tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
268 {
269         struct mmu_gather_batch *batch, *next;
270 
271         tlb_flush_mmu(tlb);
272 
273         /* keep the page table cache within bounds */
274         check_pgt_cache();
275 
276         for (batch = tlb->local.next; batch; batch = next) {
277                 next = batch->next;
278                 free_pages((unsigned long)batch, 0);
279         }
280         tlb->local.next = NULL;
281 }
282 
283 /* __tlb_remove_page
284  *      Must perform the equivalent to __free_pte(pte_get_and_clear(ptep)), while
285  *      handling the additional races in SMP caused by other CPUs caching valid
286  *      mappings in their TLBs. Returns the number of free page slots left.
287  *      When out of page slots we must call tlb_flush_mmu().
288  */
289 int __tlb_remove_page(struct mmu_gather *tlb, struct page *page)
290 {
291         struct mmu_gather_batch *batch;
292 
293         VM_BUG_ON(!tlb->need_flush);
294 
295         batch = tlb->active;
296         batch->pages[batch->nr++] = page;
297         if (batch->nr == batch->max) {
298                 if (!tlb_next_batch(tlb))
299                         return 0;
300                 batch = tlb->active;
301         }
302         VM_BUG_ON_PAGE(batch->nr > batch->max, page);
303 
304         return batch->max - batch->nr;
305 }
306 
307 #endif /* HAVE_GENERIC_MMU_GATHER */
308 
309 #ifdef CONFIG_HAVE_RCU_TABLE_FREE
310 
311 /*
312  * See the comment near struct mmu_table_batch.
313  */
314 
315 static void tlb_remove_table_smp_sync(void *arg)
316 {
317         /* Simply deliver the interrupt */
318 }
319 
320 static void tlb_remove_table_one(void *table)
321 {
322         /*
323          * This isn't an RCU grace period and hence the page-tables cannot be
324          * assumed to be actually RCU-freed.
325          *
326          * It is however sufficient for software page-table walkers that rely on
327          * IRQ disabling. See the comment near struct mmu_table_batch.
328          */
329         smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
330         __tlb_remove_table(table);
331 }
332 
333 static void tlb_remove_table_rcu(struct rcu_head *head)
334 {
335         struct mmu_table_batch *batch;
336         int i;
337 
338         batch = container_of(head, struct mmu_table_batch, rcu);
339 
340         for (i = 0; i < batch->nr; i++)
341                 __tlb_remove_table(batch->tables[i]);
342 
343         free_page((unsigned long)batch);
344 }
345 
346 void tlb_table_flush(struct mmu_gather *tlb)
347 {
348         struct mmu_table_batch **batch = &tlb->batch;
349 
350         if (*batch) {
351                 call_rcu_sched(&(*batch)->rcu, tlb_remove_table_rcu);
352                 *batch = NULL;
353         }
354 }
355 
356 void tlb_remove_table(struct mmu_gather *tlb, void *table)
357 {
358         struct mmu_table_batch **batch = &tlb->batch;
359 
360         tlb->need_flush = 1;
361 
362         /*
363          * When there's less then two users of this mm there cannot be a
364          * concurrent page-table walk.
365          */
366         if (atomic_read(&tlb->mm->mm_users) < 2) {
367                 __tlb_remove_table(table);
368                 return;
369         }
370 
371         if (*batch == NULL) {
372                 *batch = (struct mmu_table_batch *)__get_free_page(GFP_NOWAIT | __GFP_NOWARN);
373                 if (*batch == NULL) {
374                         tlb_remove_table_one(table);
375                         return;
376                 }
377                 (*batch)->nr = 0;
378         }
379         (*batch)->tables[(*batch)->nr++] = table;
380         if ((*batch)->nr == MAX_TABLE_BATCH)
381                 tlb_table_flush(tlb);
382 }
383 
384 #endif /* CONFIG_HAVE_RCU_TABLE_FREE */
385 
386 /*
387  * Note: this doesn't free the actual pages themselves. That
388  * has been handled earlier when unmapping all the memory regions.
389  */
390 static void free_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
391                            unsigned long addr)
392 {
393         pgtable_t token = pmd_pgtable(*pmd);
394         pmd_clear(pmd);
395         pte_free_tlb(tlb, token, addr);
396         atomic_long_dec(&tlb->mm->nr_ptes);
397 }
398 
399 static inline void free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
400                                 unsigned long addr, unsigned long end,
401                                 unsigned long floor, unsigned long ceiling)
402 {
403         pmd_t *pmd;
404         unsigned long next;
405         unsigned long start;
406 
407         start = addr;
408         pmd = pmd_offset(pud, addr);
409         do {
410                 next = pmd_addr_end(addr, end);
411                 if (pmd_none_or_clear_bad(pmd))
412                         continue;
413                 free_pte_range(tlb, pmd, addr);
414         } while (pmd++, addr = next, addr != end);
415 
416         start &= PUD_MASK;
417         if (start < floor)
418                 return;
419         if (ceiling) {
420                 ceiling &= PUD_MASK;
421                 if (!ceiling)
422                         return;
423         }
424         if (end - 1 > ceiling - 1)
425                 return;
426 
427         pmd = pmd_offset(pud, start);
428         pud_clear(pud);
429         pmd_free_tlb(tlb, pmd, start);
430 }
431 
432 static inline void free_pud_range(struct mmu_gather *tlb, pgd_t *pgd,
433                                 unsigned long addr, unsigned long end,
434                                 unsigned long floor, unsigned long ceiling)
435 {
436         pud_t *pud;
437         unsigned long next;
438         unsigned long start;
439 
440         start = addr;
441         pud = pud_offset(pgd, addr);
442         do {
443                 next = pud_addr_end(addr, end);
444                 if (pud_none_or_clear_bad(pud))
445                         continue;
446                 free_pmd_range(tlb, pud, addr, next, floor, ceiling);
447         } while (pud++, addr = next, addr != end);
448 
449         start &= PGDIR_MASK;
450         if (start < floor)
451                 return;
452         if (ceiling) {
453                 ceiling &= PGDIR_MASK;
454                 if (!ceiling)
455                         return;
456         }
457         if (end - 1 > ceiling - 1)
458                 return;
459 
460         pud = pud_offset(pgd, start);
461         pgd_clear(pgd);
462         pud_free_tlb(tlb, pud, start);
463 }
464 
465 /*
466  * This function frees user-level page tables of a process.
467  */
468 void free_pgd_range(struct mmu_gather *tlb,
469                         unsigned long addr, unsigned long end,
470                         unsigned long floor, unsigned long ceiling)
471 {
472         pgd_t *pgd;
473         unsigned long next;
474 
475         /*
476          * The next few lines have given us lots of grief...
477          *
478          * Why are we testing PMD* at this top level?  Because often
479          * there will be no work to do at all, and we'd prefer not to
480          * go all the way down to the bottom just to discover that.
481          *
482          * Why all these "- 1"s?  Because 0 represents both the bottom
483          * of the address space and the top of it (using -1 for the
484          * top wouldn't help much: the masks would do the wrong thing).
485          * The rule is that addr 0 and floor 0 refer to the bottom of
486          * the address space, but end 0 and ceiling 0 refer to the top
487          * Comparisons need to use "end - 1" and "ceiling - 1" (though
488          * that end 0 case should be mythical).
489          *
490          * Wherever addr is brought up or ceiling brought down, we must
491          * be careful to reject "the opposite 0" before it confuses the
492          * subsequent tests.  But what about where end is brought down
493          * by PMD_SIZE below? no, end can't go down to 0 there.
494          *
495          * Whereas we round start (addr) and ceiling down, by different
496          * masks at different levels, in order to test whether a table
497          * now has no other vmas using it, so can be freed, we don't
498          * bother to round floor or end up - the tests don't need that.
499          */
500 
501         addr &= PMD_MASK;
502         if (addr < floor) {
503                 addr += PMD_SIZE;
504                 if (!addr)
505                         return;
506         }
507         if (ceiling) {
508                 ceiling &= PMD_MASK;
509                 if (!ceiling)
510                         return;
511         }
512         if (end - 1 > ceiling - 1)
513                 end -= PMD_SIZE;
514         if (addr > end - 1)
515                 return;
516 
517         pgd = pgd_offset(tlb->mm, addr);
518         do {
519                 next = pgd_addr_end(addr, end);
520                 if (pgd_none_or_clear_bad(pgd))
521                         continue;
522                 free_pud_range(tlb, pgd, addr, next, floor, ceiling);
523         } while (pgd++, addr = next, addr != end);
524 }
525 
526 void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *vma,
527                 unsigned long floor, unsigned long ceiling)
528 {
529         while (vma) {
530                 struct vm_area_struct *next = vma->vm_next;
531                 unsigned long addr = vma->vm_start;
532 
533                 /*
534                  * Hide vma from rmap and truncate_pagecache before freeing
535                  * pgtables
536                  */
537                 unlink_anon_vmas(vma);
538                 unlink_file_vma(vma);
539 
540                 if (is_vm_hugetlb_page(vma)) {
541                         hugetlb_free_pgd_range(tlb, addr, vma->vm_end,
542                                 floor, next? next->vm_start: ceiling);
543                 } else {
544                         /*
545                          * Optimization: gather nearby vmas into one call down
546                          */
547                         while (next && next->vm_start <= vma->vm_end + PMD_SIZE
548                                && !is_vm_hugetlb_page(next)) {
549                                 vma = next;
550                                 next = vma->vm_next;
551                                 unlink_anon_vmas(vma);
552                                 unlink_file_vma(vma);
553                         }
554                         free_pgd_range(tlb, addr, vma->vm_end,
555                                 floor, next? next->vm_start: ceiling);
556                 }
557                 vma = next;
558         }
559 }
560 
561 int __pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma,
562                 pmd_t *pmd, unsigned long address)
563 {
564         spinlock_t *ptl;
565         pgtable_t new = pte_alloc_one(mm, address);
566         int wait_split_huge_page;
567         if (!new)
568                 return -ENOMEM;
569 
570         /*
571          * Ensure all pte setup (eg. pte page lock and page clearing) are
572          * visible before the pte is made visible to other CPUs by being
573          * put into page tables.
574          *
575          * The other side of the story is the pointer chasing in the page
576          * table walking code (when walking the page table without locking;
577          * ie. most of the time). Fortunately, these data accesses consist
578          * of a chain of data-dependent loads, meaning most CPUs (alpha
579          * being the notable exception) will already guarantee loads are
580          * seen in-order. See the alpha page table accessors for the
581          * smp_read_barrier_depends() barriers in page table walking code.
582          */
583         smp_wmb(); /* Could be smp_wmb__xxx(before|after)_spin_lock */
584 
585         ptl = pmd_lock(mm, pmd);
586         wait_split_huge_page = 0;
587         if (likely(pmd_none(*pmd))) {   /* Has another populated it ? */
588                 atomic_long_inc(&mm->nr_ptes);
589                 pmd_populate(mm, pmd, new);
590                 new = NULL;
591         } else if (unlikely(pmd_trans_splitting(*pmd)))
592                 wait_split_huge_page = 1;
593         spin_unlock(ptl);
594         if (new)
595                 pte_free(mm, new);
596         if (wait_split_huge_page)
597                 wait_split_huge_page(vma->anon_vma, pmd);
598         return 0;
599 }
600 
601 int __pte_alloc_kernel(pmd_t *pmd, unsigned long address)
602 {
603         pte_t *new = pte_alloc_one_kernel(&init_mm, address);
604         if (!new)
605                 return -ENOMEM;
606 
607         smp_wmb(); /* See comment in __pte_alloc */
608 
609         spin_lock(&init_mm.page_table_lock);
610         if (likely(pmd_none(*pmd))) {   /* Has another populated it ? */
611                 pmd_populate_kernel(&init_mm, pmd, new);
612                 new = NULL;
613         } else
614                 VM_BUG_ON(pmd_trans_splitting(*pmd));
615         spin_unlock(&init_mm.page_table_lock);
616         if (new)
617                 pte_free_kernel(&init_mm, new);
618         return 0;
619 }
620 
621 static inline void init_rss_vec(int *rss)
622 {
623         memset(rss, 0, sizeof(int) * NR_MM_COUNTERS);
624 }
625 
626 static inline void add_mm_rss_vec(struct mm_struct *mm, int *rss)
627 {
628         int i;
629 
630         if (current->mm == mm)
631                 sync_mm_rss(mm);
632         for (i = 0; i < NR_MM_COUNTERS; i++)
633                 if (rss[i])
634                         add_mm_counter(mm, i, rss[i]);
635 }
636 
637 /*
638  * This function is called to print an error when a bad pte
639  * is found. For example, we might have a PFN-mapped pte in
640  * a region that doesn't allow it.
641  *
642  * The calling function must still handle the error.
643  */
644 static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
645                           pte_t pte, struct page *page)
646 {
647         pgd_t *pgd = pgd_offset(vma->vm_mm, addr);
648         pud_t *pud = pud_offset(pgd, addr);
649         pmd_t *pmd = pmd_offset(pud, addr);
650         struct address_space *mapping;
651         pgoff_t index;
652         static unsigned long resume;
653         static unsigned long nr_shown;
654         static unsigned long nr_unshown;
655 
656         /*
657          * Allow a burst of 60 reports, then keep quiet for that minute;
658          * or allow a steady drip of one report per second.
659          */
660         if (nr_shown == 60) {
661                 if (time_before(jiffies, resume)) {
662                         nr_unshown++;
663                         return;
664                 }
665                 if (nr_unshown) {
666                         printk(KERN_ALERT
667                                 "BUG: Bad page map: %lu messages suppressed\n",
668                                 nr_unshown);
669                         nr_unshown = 0;
670                 }
671                 nr_shown = 0;
672         }
673         if (nr_shown++ == 0)
674                 resume = jiffies + 60 * HZ;
675 
676         mapping = vma->vm_file ? vma->vm_file->f_mapping : NULL;
677         index = linear_page_index(vma, addr);
678 
679         printk(KERN_ALERT
680                 "BUG: Bad page map in process %s  pte:%08llx pmd:%08llx\n",
681                 current->comm,
682                 (long long)pte_val(pte), (long long)pmd_val(*pmd));
683         if (page)
684                 dump_page(page, "bad pte");
685         printk(KERN_ALERT
686                 "addr:%p vm_flags:%08lx anon_vma:%p mapping:%p index:%lx\n",
687                 (void *)addr, vma->vm_flags, vma->anon_vma, mapping, index);
688         /*
689          * Choose text because data symbols depend on CONFIG_KALLSYMS_ALL=y
690          */
691         if (vma->vm_ops)
692                 printk(KERN_ALERT "vma->vm_ops->fault: %pSR\n",
693                        vma->vm_ops->fault);
694         if (vma->vm_file)
695                 printk(KERN_ALERT "vma->vm_file->f_op->mmap: %pSR\n",
696                        vma->vm_file->f_op->mmap);
697         dump_stack();
698         add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
699 }
700 
701 static inline bool is_cow_mapping(vm_flags_t flags)
702 {
703         return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
704 }
705 
706 /*
707  * vm_normal_page -- This function gets the "struct page" associated with a pte.
708  *
709  * "Special" mappings do not wish to be associated with a "struct page" (either
710  * it doesn't exist, or it exists but they don't want to touch it). In this
711  * case, NULL is returned here. "Normal" mappings do have a struct page.
712  *
713  * There are 2 broad cases. Firstly, an architecture may define a pte_special()
714  * pte bit, in which case this function is trivial. Secondly, an architecture
715  * may not have a spare pte bit, which requires a more complicated scheme,
716  * described below.
717  *
718  * A raw VM_PFNMAP mapping (ie. one that is not COWed) is always considered a
719  * special mapping (even if there are underlying and valid "struct pages").
720  * COWed pages of a VM_PFNMAP are always normal.
721  *
722  * The way we recognize COWed pages within VM_PFNMAP mappings is through the
723  * rules set up by "remap_pfn_range()": the vma will have the VM_PFNMAP bit
724  * set, and the vm_pgoff will point to the first PFN mapped: thus every special
725  * mapping will always honor the rule
726  *
727  *      pfn_of_page == vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT)
728  *
729  * And for normal mappings this is false.
730  *
731  * This restricts such mappings to be a linear translation from virtual address
732  * to pfn. To get around this restriction, we allow arbitrary mappings so long
733  * as the vma is not a COW mapping; in that case, we know that all ptes are
734  * special (because none can have been COWed).
735  *
736  *
737  * In order to support COW of arbitrary special mappings, we have VM_MIXEDMAP.
738  *
739  * VM_MIXEDMAP mappings can likewise contain memory with or without "struct
740  * page" backing, however the difference is that _all_ pages with a struct
741  * page (that is, those where pfn_valid is true) are refcounted and considered
742  * normal pages by the VM. The disadvantage is that pages are refcounted
743  * (which can be slower and simply not an option for some PFNMAP users). The
744  * advantage is that we don't have to follow the strict linearity rule of
745  * PFNMAP mappings in order to support COWable mappings.
746  *
747  */
748 #ifdef __HAVE_ARCH_PTE_SPECIAL
749 # define HAVE_PTE_SPECIAL 1
750 #else
751 # define HAVE_PTE_SPECIAL 0
752 #endif
753 struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
754                                 pte_t pte)
755 {
756         unsigned long pfn = pte_pfn(pte);
757 
758         if (HAVE_PTE_SPECIAL) {
759                 if (likely(!pte_special(pte)))
760                         goto check_pfn;
761                 if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
762                         return NULL;
763                 if (!is_zero_pfn(pfn))
764                         print_bad_pte(vma, addr, pte, NULL);
765                 return NULL;
766         }
767 
768         /* !HAVE_PTE_SPECIAL case follows: */
769 
770         if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
771                 if (vma->vm_flags & VM_MIXEDMAP) {
772                         if (!pfn_valid(pfn))
773                                 return NULL;
774                         goto out;
775                 } else {
776                         unsigned long off;
777                         off = (addr - vma->vm_start) >> PAGE_SHIFT;
778                         if (pfn == vma->vm_pgoff + off)
779                                 return NULL;
780                         if (!is_cow_mapping(vma->vm_flags))
781                                 return NULL;
782                 }
783         }
784 
785         if (is_zero_pfn(pfn))
786                 return NULL;
787 check_pfn:
788         if (unlikely(pfn > highest_memmap_pfn)) {
789                 print_bad_pte(vma, addr, pte, NULL);
790                 return NULL;
791         }
792 
793         /*
794          * NOTE! We still have PageReserved() pages in the page tables.
795          * eg. VDSO mappings can cause them to exist.
796          */
797 out:
798         return pfn_to_page(pfn);
799 }
800 
801 /*
802  * copy one vm_area from one task to the other. Assumes the page tables
803  * already present in the new task to be cleared in the whole range
804  * covered by this vma.
805  */
806 
807 static inline unsigned long
808 copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
809                 pte_t *dst_pte, pte_t *src_pte, struct vm_area_struct *vma,
810                 unsigned long addr, int *rss)
811 {
812         unsigned long vm_flags = vma->vm_flags;
813         pte_t pte = *src_pte;
814         struct page *page;
815 
816         /* pte contains position in swap or file, so copy. */
817         if (unlikely(!pte_present(pte))) {
818                 if (!pte_file(pte)) {
819                         swp_entry_t entry = pte_to_swp_entry(pte);
820 
821                         if (swap_duplicate(entry) < 0)
822                                 return entry.val;
823 
824                         /* make sure dst_mm is on swapoff's mmlist. */
825                         if (unlikely(list_empty(&dst_mm->mmlist))) {
826                                 spin_lock(&mmlist_lock);
827                                 if (list_empty(&dst_mm->mmlist))
828                                         list_add(&dst_mm->mmlist,
829                                                  &src_mm->mmlist);
830                                 spin_unlock(&mmlist_lock);
831                         }
832                         if (likely(!non_swap_entry(entry)))
833                                 rss[MM_SWAPENTS]++;
834                         else if (is_migration_entry(entry)) {
835                                 page = migration_entry_to_page(entry);
836 
837                                 if (PageAnon(page))
838                                         rss[MM_ANONPAGES]++;
839                                 else
840                                         rss[MM_FILEPAGES]++;
841 
842                                 if (is_write_migration_entry(entry) &&
843                                     is_cow_mapping(vm_flags)) {
844                                         /*
845                                          * COW mappings require pages in both
846                                          * parent and child to be set to read.
847                                          */
848                                         make_migration_entry_read(&entry);
849                                         pte = swp_entry_to_pte(entry);
850                                         if (pte_swp_soft_dirty(*src_pte))
851                                                 pte = pte_swp_mksoft_dirty(pte);
852                                         set_pte_at(src_mm, addr, src_pte, pte);
853                                 }
854                         }
855                 }
856                 goto out_set_pte;
857         }
858 
859         /*
860          * If it's a COW mapping, write protect it both
861          * in the parent and the child
862          */
863         if (is_cow_mapping(vm_flags)) {
864                 ptep_set_wrprotect(src_mm, addr, src_pte);
865                 pte = pte_wrprotect(pte);
866         }
867 
868         /*
869          * If it's a shared mapping, mark it clean in
870          * the child
871          */
872         if (vm_flags & VM_SHARED)
873                 pte = pte_mkclean(pte);
874         pte = pte_mkold(pte);
875 
876         page = vm_normal_page(vma, addr, pte);
877         if (page) {
878                 get_page(page);
879                 page_dup_rmap(page);
880                 if (PageAnon(page))
881                         rss[MM_ANONPAGES]++;
882                 else
883                         rss[MM_FILEPAGES]++;
884         }
885 
886 out_set_pte:
887         set_pte_at(dst_mm, addr, dst_pte, pte);
888         return 0;
889 }
890 
891 int copy_pte_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
892                    pmd_t *dst_pmd, pmd_t *src_pmd, struct vm_area_struct *vma,
893                    unsigned long addr, unsigned long end)
894 {
895         pte_t *orig_src_pte, *orig_dst_pte;
896         pte_t *src_pte, *dst_pte;
897         spinlock_t *src_ptl, *dst_ptl;
898         int progress = 0;
899         int rss[NR_MM_COUNTERS];
900         swp_entry_t entry = (swp_entry_t){0};
901 
902 again:
903         init_rss_vec(rss);
904 
905         dst_pte = pte_alloc_map_lock(dst_mm, dst_pmd, addr, &dst_ptl);
906         if (!dst_pte)
907                 return -ENOMEM;
908         src_pte = pte_offset_map(src_pmd, addr);
909         src_ptl = pte_lockptr(src_mm, src_pmd);
910         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
911         orig_src_pte = src_pte;
912         orig_dst_pte = dst_pte;
913         arch_enter_lazy_mmu_mode();
914 
915         do {
916                 /*
917                  * We are holding two locks at this point - either of them
918                  * could generate latencies in another task on another CPU.
919                  */
920                 if (progress >= 32) {
921                         progress = 0;
922                         if (need_resched() ||
923                             spin_needbreak(src_ptl) || spin_needbreak(dst_ptl))
924                                 break;
925                 }
926                 if (pte_none(*src_pte)) {
927                         progress++;
928                         continue;
929                 }
930                 entry.val = copy_one_pte(dst_mm, src_mm, dst_pte, src_pte,
931                                                         vma, addr, rss);
932                 if (entry.val)
933                         break;
934                 progress += 8;
935         } while (dst_pte++, src_pte++, addr += PAGE_SIZE, addr != end);
936 
937         arch_leave_lazy_mmu_mode();
938         spin_unlock(src_ptl);
939         pte_unmap(orig_src_pte);
940         add_mm_rss_vec(dst_mm, rss);
941         pte_unmap_unlock(orig_dst_pte, dst_ptl);
942         cond_resched();
943 
944         if (entry.val) {
945                 if (add_swap_count_continuation(entry, GFP_KERNEL) < 0)
946                         return -ENOMEM;
947                 progress = 0;
948         }
949         if (addr != end)
950                 goto again;
951         return 0;
952 }
953 
954 static inline int copy_pmd_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
955                 pud_t *dst_pud, pud_t *src_pud, struct vm_area_struct *vma,
956                 unsigned long addr, unsigned long end)
957 {
958         pmd_t *src_pmd, *dst_pmd;
959         unsigned long next;
960 
961         dst_pmd = pmd_alloc(dst_mm, dst_pud, addr);
962         if (!dst_pmd)
963                 return -ENOMEM;
964         src_pmd = pmd_offset(src_pud, addr);
965         do {
966                 next = pmd_addr_end(addr, end);
967                 if (pmd_trans_huge(*src_pmd)) {
968                         int err;
969                         VM_BUG_ON(next-addr != HPAGE_PMD_SIZE);
970                         err = copy_huge_pmd(dst_mm, src_mm,
971                                             dst_pmd, src_pmd, addr, vma);
972                         if (err == -ENOMEM)
973                                 return -ENOMEM;
974                         if (!err)
975                                 continue;
976                         /* fall through */
977                 }
978                 if (pmd_none_or_clear_bad(src_pmd))
979                         continue;
980                 if (copy_pte_range(dst_mm, src_mm, dst_pmd, src_pmd,
981                                                 vma, addr, next))
982                         return -ENOMEM;
983         } while (dst_pmd++, src_pmd++, addr = next, addr != end);
984         return 0;
985 }
986 
987 static inline int copy_pud_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
988                 pgd_t *dst_pgd, pgd_t *src_pgd, struct vm_area_struct *vma,
989                 unsigned long addr, unsigned long end)
990 {
991         pud_t *src_pud, *dst_pud;
992         unsigned long next;
993 
994         dst_pud = pud_alloc(dst_mm, dst_pgd, addr);
995         if (!dst_pud)
996                 return -ENOMEM;
997         src_pud = pud_offset(src_pgd, addr);
998         do {
999                 next = pud_addr_end(addr, end);
1000                 if (pud_none_or_clear_bad(src_pud))
1001                         continue;
1002                 if (copy_pmd_range(dst_mm, src_mm, dst_pud, src_pud,
1003                                                 vma, addr, next))
1004                         return -ENOMEM;
1005         } while (dst_pud++, src_pud++, addr = next, addr != end);
1006         return 0;
1007 }
1008 
1009 int copy_page_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1010                 struct vm_area_struct *vma)
1011 {
1012         pgd_t *src_pgd, *dst_pgd;
1013         unsigned long next;
1014         unsigned long addr = vma->vm_start;
1015         unsigned long end = vma->vm_end;
1016         unsigned long mmun_start;       /* For mmu_notifiers */
1017         unsigned long mmun_end;         /* For mmu_notifiers */
1018         bool is_cow;
1019         int ret;
1020 
1021         /*
1022          * Don't copy ptes where a page fault will fill them correctly.
1023          * Fork becomes much lighter when there are big shared or private
1024          * readonly mappings. The tradeoff is that copy_page_range is more
1025          * efficient than faulting.
1026          */
1027         if (!(vma->vm_flags & (VM_HUGETLB | VM_NONLINEAR |
1028                                VM_PFNMAP | VM_MIXEDMAP))) {
1029                 if (!vma->anon_vma)
1030                         return 0;
1031         }
1032 
1033         if (is_vm_hugetlb_page(vma))
1034                 return copy_hugetlb_page_range(dst_mm, src_mm, vma);
1035 
1036         if (unlikely(vma->vm_flags & VM_PFNMAP)) {
1037                 /*
1038                  * We do not free on error cases below as remove_vma
1039                  * gets called on error from higher level routine
1040                  */
1041                 ret = track_pfn_copy(vma);
1042                 if (ret)
1043                         return ret;
1044         }
1045 
1046         /*
1047          * We need to invalidate the secondary MMU mappings only when
1048          * there could be a permission downgrade on the ptes of the
1049          * parent mm. And a permission downgrade will only happen if
1050          * is_cow_mapping() returns true.
1051          */
1052         is_cow = is_cow_mapping(vma->vm_flags);
1053         mmun_start = addr;
1054         mmun_end   = end;
1055         if (is_cow)
1056                 mmu_notifier_invalidate_range_start(src_mm, mmun_start,
1057                                                     mmun_end);
1058 
1059         ret = 0;
1060         dst_pgd = pgd_offset(dst_mm, addr);
1061         src_pgd = pgd_offset(src_mm, addr);
1062         do {
1063                 next = pgd_addr_end(addr, end);
1064                 if (pgd_none_or_clear_bad(src_pgd))
1065                         continue;
1066                 if (unlikely(copy_pud_range(dst_mm, src_mm, dst_pgd, src_pgd,
1067                                             vma, addr, next))) {
1068                         ret = -ENOMEM;
1069                         break;
1070                 }
1071         } while (dst_pgd++, src_pgd++, addr = next, addr != end);
1072 
1073         if (is_cow)
1074                 mmu_notifier_invalidate_range_end(src_mm, mmun_start, mmun_end);
1075         return ret;
1076 }
1077 
1078 static unsigned long zap_pte_range(struct mmu_gather *tlb,
1079                                 struct vm_area_struct *vma, pmd_t *pmd,
1080                                 unsigned long addr, unsigned long end,
1081                                 struct zap_details *details)
1082 {
1083         struct mm_struct *mm = tlb->mm;
1084         int force_flush = 0;
1085         int rss[NR_MM_COUNTERS];
1086         spinlock_t *ptl;
1087         pte_t *start_pte;
1088         pte_t *pte;
1089 
1090 again:
1091         init_rss_vec(rss);
1092         start_pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
1093         pte = start_pte;
1094         arch_enter_lazy_mmu_mode();
1095         do {
1096                 pte_t ptent = *pte;
1097                 if (pte_none(ptent)) {
1098                         continue;
1099                 }
1100 
1101                 if (pte_present(ptent)) {
1102                         struct page *page;
1103 
1104                         page = vm_normal_page(vma, addr, ptent);
1105                         if (unlikely(details) && page) {
1106                                 /*
1107                                  * unmap_shared_mapping_pages() wants to
1108                                  * invalidate cache without truncating:
1109                                  * unmap shared but keep private pages.
1110                                  */
1111                                 if (details->check_mapping &&
1112                                     details->check_mapping != page->mapping)
1113                                         continue;
1114                                 /*
1115                                  * Each page->index must be checked when
1116                                  * invalidating or truncating nonlinear.
1117                                  */
1118                                 if (details->nonlinear_vma &&
1119                                     (page->index < details->first_index ||
1120                                      page->index > details->last_index))
1121                                         continue;
1122                         }
1123                         ptent = ptep_get_and_clear_full(mm, addr, pte,
1124                                                         tlb->fullmm);
1125                         tlb_remove_tlb_entry(tlb, pte, addr);
1126                         if (unlikely(!page))
1127                                 continue;
1128                         if (unlikely(details) && details->nonlinear_vma
1129                             && linear_page_index(details->nonlinear_vma,
1130                                                 addr) != page->index) {
1131                                 pte_t ptfile = pgoff_to_pte(page->index);
1132                                 if (pte_soft_dirty(ptent))
1133                                         pte_file_mksoft_dirty(ptfile);
1134                                 set_pte_at(mm, addr, pte, ptfile);
1135                         }
1136                         if (PageAnon(page))
1137                                 rss[MM_ANONPAGES]--;
1138                         else {
1139                                 if (pte_dirty(ptent)) {
1140                                         force_flush = 1;
1141                                         set_page_dirty(page);
1142                                 }
1143                                 if (pte_young(ptent) &&
1144                                     likely(!(vma->vm_flags & VM_SEQ_READ)))
1145                                         mark_page_accessed(page);
1146                                 rss[MM_FILEPAGES]--;
1147                         }
1148                         page_remove_rmap(page);
1149                         if (unlikely(page_mapcount(page) < 0))
1150                                 print_bad_pte(vma, addr, ptent, page);
1151                         if (unlikely(!__tlb_remove_page(tlb, page))) {
1152                                 force_flush = 1;
1153                                 break;
1154                         }
1155                         continue;
1156                 }
1157                 /*
1158                  * If details->check_mapping, we leave swap entries;
1159                  * if details->nonlinear_vma, we leave file entries.
1160                  */
1161                 if (unlikely(details))
1162                         continue;
1163                 if (pte_file(ptent)) {
1164                         if (unlikely(!(vma->vm_flags & VM_NONLINEAR)))
1165                                 print_bad_pte(vma, addr, ptent, NULL);
1166                 } else {
1167                         swp_entry_t entry = pte_to_swp_entry(ptent);
1168 
1169                         if (!non_swap_entry(entry))
1170                                 rss[MM_SWAPENTS]--;
1171                         else if (is_migration_entry(entry)) {
1172                                 struct page *page;
1173 
1174                                 page = migration_entry_to_page(entry);
1175 
1176                                 if (PageAnon(page))
1177                                         rss[MM_ANONPAGES]--;
1178                                 else
1179                                         rss[MM_FILEPAGES]--;
1180                         }
1181                         if (unlikely(!free_swap_and_cache(entry)))
1182                                 print_bad_pte(vma, addr, ptent, NULL);
1183                 }
1184                 pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
1185         } while (pte++, addr += PAGE_SIZE, addr != end);
1186 
1187         add_mm_rss_vec(mm, rss);
1188         arch_leave_lazy_mmu_mode();
1189 
1190         /* Do the actual TLB flush before dropping ptl */
1191         if (force_flush) {
1192                 unsigned long old_end;
1193 
1194                 /*
1195                  * Flush the TLB just for the previous segment,
1196                  * then update the range to be the remaining
1197                  * TLB range.
1198                  */
1199                 old_end = tlb->end;
1200                 tlb->end = addr;
1201                 tlb_flush_mmu_tlbonly(tlb);
1202                 tlb->start = addr;
1203                 tlb->end = old_end;
1204         }
1205         pte_unmap_unlock(start_pte, ptl);
1206 
1207         /*
1208          * If we forced a TLB flush (either due to running out of
1209          * batch buffers or because we needed to flush dirty TLB
1210          * entries before releasing the ptl), free the batched
1211          * memory too. Restart if we didn't do everything.
1212          */
1213         if (force_flush) {
1214                 force_flush = 0;
1215                 tlb_flush_mmu_free(tlb);
1216 
1217                 if (addr != end)
1218                         goto again;
1219         }
1220 
1221         return addr;
1222 }
1223 
1224 static inline unsigned long zap_pmd_range(struct mmu_gather *tlb,
1225                                 struct vm_area_struct *vma, pud_t *pud,
1226                                 unsigned long addr, unsigned long end,
1227                                 struct zap_details *details)
1228 {
1229         pmd_t *pmd;
1230         unsigned long next;
1231 
1232         pmd = pmd_offset(pud, addr);
1233         do {
1234                 next = pmd_addr_end(addr, end);
1235                 if (pmd_trans_huge(*pmd)) {
1236                         if (next - addr != HPAGE_PMD_SIZE) {
1237 #ifdef CONFIG_DEBUG_VM
1238                                 if (!rwsem_is_locked(&tlb->mm->mmap_sem)) {
1239                                         pr_err("%s: mmap_sem is unlocked! addr=0x%lx end=0x%lx vma->vm_start=0x%lx vma->vm_end=0x%lx\n",
1240                                                 __func__, addr, end,
1241                                                 vma->vm_start,
1242                                                 vma->vm_end);
1243                                         BUG();
1244                                 }
1245 #endif
1246                                 split_huge_page_pmd(vma, addr, pmd);
1247                         } else if (zap_huge_pmd(tlb, vma, pmd, addr))
1248                                 goto next;
1249                         /* fall through */
1250                 }
1251                 /*
1252                  * Here there can be other concurrent MADV_DONTNEED or
1253                  * trans huge page faults running, and if the pmd is
1254                  * none or trans huge it can change under us. This is
1255                  * because MADV_DONTNEED holds the mmap_sem in read
1256                  * mode.
1257                  */
1258                 if (pmd_none_or_trans_huge_or_clear_bad(pmd))
1259                         goto next;
1260                 next = zap_pte_range(tlb, vma, pmd, addr, next, details);
1261 next:
1262                 cond_resched();
1263         } while (pmd++, addr = next, addr != end);
1264 
1265         return addr;
1266 }
1267 
1268 static inline unsigned long zap_pud_range(struct mmu_gather *tlb,
1269                                 struct vm_area_struct *vma, pgd_t *pgd,
1270                                 unsigned long addr, unsigned long end,
1271                                 struct zap_details *details)
1272 {
1273         pud_t *pud;
1274         unsigned long next;
1275 
1276         pud = pud_offset(pgd, addr);
1277         do {
1278                 next = pud_addr_end(addr, end);
1279                 if (pud_none_or_clear_bad(pud))
1280                         continue;
1281                 next = zap_pmd_range(tlb, vma, pud, addr, next, details);
1282         } while (pud++, addr = next, addr != end);
1283 
1284         return addr;
1285 }
1286 
1287 static void unmap_page_range(struct mmu_gather *tlb,
1288                              struct vm_area_struct *vma,
1289                              unsigned long addr, unsigned long end,
1290                              struct zap_details *details)
1291 {
1292         pgd_t *pgd;
1293         unsigned long next;
1294 
1295         if (details && !details->check_mapping && !details->nonlinear_vma)
1296                 details = NULL;
1297 
1298         BUG_ON(addr >= end);
1299         mem_cgroup_uncharge_start();
1300         tlb_start_vma(tlb, vma);
1301         pgd = pgd_offset(vma->vm_mm, addr);
1302         do {
1303                 next = pgd_addr_end(addr, end);
1304                 if (pgd_none_or_clear_bad(pgd))
1305                         continue;
1306                 next = zap_pud_range(tlb, vma, pgd, addr, next, details);
1307         } while (pgd++, addr = next, addr != end);
1308         tlb_end_vma(tlb, vma);
1309         mem_cgroup_uncharge_end();
1310 }
1311 
1312 
1313 static void unmap_single_vma(struct mmu_gather *tlb,
1314                 struct vm_area_struct *vma, unsigned long start_addr,
1315                 unsigned long end_addr,
1316                 struct zap_details *details)
1317 {
1318         unsigned long start = max(vma->vm_start, start_addr);
1319         unsigned long end;
1320 
1321         if (start >= vma->vm_end)
1322                 return;
1323         end = min(vma->vm_end, end_addr);
1324         if (end <= vma->vm_start)
1325                 return;
1326 
1327         if (vma->vm_file)
1328                 uprobe_munmap(vma, start, end);
1329 
1330         if (unlikely(vma->vm_flags & VM_PFNMAP))
1331                 untrack_pfn(vma, 0, 0);
1332 
1333         if (start != end) {
1334                 if (unlikely(is_vm_hugetlb_page(vma))) {
1335                         /*
1336                          * It is undesirable to test vma->vm_file as it
1337                          * should be non-null for valid hugetlb area.
1338                          * However, vm_file will be NULL in the error
1339                          * cleanup path of mmap_region. When
1340                          * hugetlbfs ->mmap method fails,
1341                          * mmap_region() nullifies vma->vm_file
1342                          * before calling this function to clean up.
1343                          * Since no pte has actually been setup, it is
1344                          * safe to do nothing in this case.
1345                          */
1346                         if (vma->vm_file) {
1347                                 mutex_lock(&vma->vm_file->f_mapping->i_mmap_mutex);
1348                                 __unmap_hugepage_range_final(tlb, vma, start, end, NULL);
1349                                 mutex_unlock(&vma->vm_file->f_mapping->i_mmap_mutex);
1350                         }
1351                 } else
1352                         unmap_page_range(tlb, vma, start, end, details);
1353         }
1354 }
1355 
1356 /**
1357  * unmap_vmas - unmap a range of memory covered by a list of vma's
1358  * @tlb: address of the caller's struct mmu_gather
1359  * @vma: the starting vma
1360  * @start_addr: virtual address at which to start unmapping
1361  * @end_addr: virtual address at which to end unmapping
1362  *
1363  * Unmap all pages in the vma list.
1364  *
1365  * Only addresses between `start' and `end' will be unmapped.
1366  *
1367  * The VMA list must be sorted in ascending virtual address order.
1368  *
1369  * unmap_vmas() assumes that the caller will flush the whole unmapped address
1370  * range after unmap_vmas() returns.  So the only responsibility here is to
1371  * ensure that any thus-far unmapped pages are flushed before unmap_vmas()
1372  * drops the lock and schedules.
1373  */
1374 void unmap_vmas(struct mmu_gather *tlb,
1375                 struct vm_area_struct *vma, unsigned long start_addr,
1376                 unsigned long end_addr)
1377 {
1378         struct mm_struct *mm = vma->vm_mm;
1379 
1380         mmu_notifier_invalidate_range_start(mm, start_addr, end_addr);
1381         for ( ; vma && vma->vm_start < end_addr; vma = vma->vm_next)
1382                 unmap_single_vma(tlb, vma, start_addr, end_addr, NULL);
1383         mmu_notifier_invalidate_range_end(mm, start_addr, end_addr);
1384 }
1385 
1386 /**
1387  * zap_page_range - remove user pages in a given range
1388  * @vma: vm_area_struct holding the applicable pages
1389  * @start: starting address of pages to zap
1390  * @size: number of bytes to zap
1391  * @details: details of nonlinear truncation or shared cache invalidation
1392  *
1393  * Caller must protect the VMA list
1394  */
1395 void zap_page_range(struct vm_area_struct *vma, unsigned long start,
1396                 unsigned long size, struct zap_details *details)
1397 {
1398         struct mm_struct *mm = vma->vm_mm;
1399         struct mmu_gather tlb;
1400         unsigned long end = start + size;
1401 
1402         lru_add_drain();
1403         tlb_gather_mmu(&tlb, mm, start, end);
1404         update_hiwater_rss(mm);
1405         mmu_notifier_invalidate_range_start(mm, start, end);
1406         for ( ; vma && vma->vm_start < end; vma = vma->vm_next)
1407                 unmap_single_vma(&tlb, vma, start, end, details);
1408         mmu_notifier_invalidate_range_end(mm, start, end);
1409         tlb_finish_mmu(&tlb, start, end);
1410 }
1411 
1412 /**
1413  * zap_page_range_single - remove user pages in a given range
1414  * @vma: vm_area_struct holding the applicable pages
1415  * @address: starting address of pages to zap
1416  * @size: number of bytes to zap
1417  * @details: details of nonlinear truncation or shared cache invalidation
1418  *
1419  * The range must fit into one VMA.
1420  */
1421 static void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
1422                 unsigned long size, struct zap_details *details)
1423 {
1424         struct mm_struct *mm = vma->vm_mm;
1425         struct mmu_gather tlb;
1426         unsigned long end = address + size;
1427 
1428         lru_add_drain();
1429         tlb_gather_mmu(&tlb, mm, address, end);
1430         update_hiwater_rss(mm);
1431         mmu_notifier_invalidate_range_start(mm, address, end);
1432         unmap_single_vma(&tlb, vma, address, end, details);
1433         mmu_notifier_invalidate_range_end(mm, address, end);
1434         tlb_finish_mmu(&tlb, address, end);
1435 }
1436 
1437 /**
1438  * zap_vma_ptes - remove ptes mapping the vma
1439  * @vma: vm_area_struct holding ptes to be zapped
1440  * @address: starting address of pages to zap
1441  * @size: number of bytes to zap
1442  *
1443  * This function only unmaps ptes assigned to VM_PFNMAP vmas.
1444  *
1445  * The entire address range must be fully contained within the vma.
1446  *
1447  * Returns 0 if successful.
1448  */
1449 int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
1450                 unsigned long size)
1451 {
1452         if (address < vma->vm_start || address + size > vma->vm_end ||
1453                         !(vma->vm_flags & VM_PFNMAP))
1454                 return -1;
1455         zap_page_range_single(vma, address, size, NULL);
1456         return 0;
1457 }
1458 EXPORT_SYMBOL_GPL(zap_vma_ptes);
1459 
1460 /**
1461  * follow_page_mask - look up a page descriptor from a user-virtual address
1462  * @vma: vm_area_struct mapping @address
1463  * @address: virtual address to look up
1464  * @flags: flags modifying lookup behaviour
1465  * @page_mask: on output, *page_mask is set according to the size of the page
1466  *
1467  * @flags can have FOLL_ flags set, defined in <linux/mm.h>
1468  *
1469  * Returns the mapped (struct page *), %NULL if no mapping exists, or
1470  * an error pointer if there is a mapping to something not represented
1471  * by a page descriptor (see also vm_normal_page()).
1472  */
1473 struct page *follow_page_mask(struct vm_area_struct *vma,
1474                               unsigned long address, unsigned int flags,
1475                               unsigned int *page_mask)
1476 {
1477         pgd_t *pgd;
1478         pud_t *pud;
1479         pmd_t *pmd;
1480         pte_t *ptep, pte;
1481         spinlock_t *ptl;
1482         struct page *page;
1483         struct mm_struct *mm = vma->vm_mm;
1484 
1485         *page_mask = 0;
1486 
1487         page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
1488         if (!IS_ERR(page)) {
1489                 BUG_ON(flags & FOLL_GET);
1490                 goto out;
1491         }
1492 
1493         page = NULL;
1494         pgd = pgd_offset(mm, address);
1495         if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
1496                 goto no_page_table;
1497 
1498         pud = pud_offset(pgd, address);
1499         if (pud_none(*pud))
1500                 goto no_page_table;
1501         if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
1502                 if (flags & FOLL_GET)
1503                         goto out;
1504                 page = follow_huge_pud(mm, address, pud, flags & FOLL_WRITE);
1505                 goto out;
1506         }
1507         if (unlikely(pud_bad(*pud)))
1508                 goto no_page_table;
1509 
1510         pmd = pmd_offset(pud, address);
1511         if (pmd_none(*pmd))
1512                 goto no_page_table;
1513         if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
1514                 page = follow_huge_pmd(mm, address, pmd, flags & FOLL_WRITE);
1515                 if (flags & FOLL_GET) {
1516                         /*
1517                          * Refcount on tail pages are not well-defined and
1518                          * shouldn't be taken. The caller should handle a NULL
1519                          * return when trying to follow tail pages.
1520                          */
1521                         if (PageHead(page))
1522                                 get_page(page);
1523                         else {
1524                                 page = NULL;
1525                                 goto out;
1526                         }
1527                 }
1528                 goto out;
1529         }
1530         if ((flags & FOLL_NUMA) && pmd_numa(*pmd))
1531                 goto no_page_table;
1532         if (pmd_trans_huge(*pmd)) {
1533                 if (flags & FOLL_SPLIT) {
1534                         split_huge_page_pmd(vma, address, pmd);
1535                         goto split_fallthrough;
1536                 }
1537                 ptl = pmd_lock(mm, pmd);
1538                 if (likely(pmd_trans_huge(*pmd))) {
1539                         if (unlikely(pmd_trans_splitting(*pmd))) {
1540                                 spin_unlock(ptl);
1541                                 wait_split_huge_page(vma->anon_vma, pmd);
1542                         } else {
1543                                 page = follow_trans_huge_pmd(vma, address,
1544                                                              pmd, flags);
1545                                 spin_unlock(ptl);
1546                                 *page_mask = HPAGE_PMD_NR - 1;
1547                                 goto out;
1548                         }
1549                 } else
1550                         spin_unlock(ptl);
1551                 /* fall through */
1552         }
1553 split_fallthrough:
1554         if (unlikely(pmd_bad(*pmd)))
1555                 goto no_page_table;
1556 
1557         ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
1558 
1559         pte = *ptep;
1560         if (!pte_present(pte)) {
1561                 swp_entry_t entry;
1562                 /*
1563                  * KSM's break_ksm() relies upon recognizing a ksm page
1564                  * even while it is being migrated, so for that case we
1565                  * need migration_entry_wait().
1566                  */
1567                 if (likely(!(flags & FOLL_MIGRATION)))
1568                         goto no_page;
1569                 if (pte_none(pte) || pte_file(pte))
1570                         goto no_page;
1571                 entry = pte_to_swp_entry(pte);
1572                 if (!is_migration_entry(entry))
1573                         goto no_page;
1574                 pte_unmap_unlock(ptep, ptl);
1575                 migration_entry_wait(mm, pmd, address);
1576                 goto split_fallthrough;
1577         }
1578         if ((flags & FOLL_NUMA) && pte_numa(pte))
1579                 goto no_page;
1580         if ((flags & FOLL_WRITE) && !pte_write(pte))
1581                 goto unlock;
1582 
1583         page = vm_normal_page(vma, address, pte);
1584         if (unlikely(!page)) {
1585                 if ((flags & FOLL_DUMP) ||
1586                     !is_zero_pfn(pte_pfn(pte)))
1587                         goto bad_page;
1588                 page = pte_page(pte);
1589         }
1590 
1591         if (flags & FOLL_GET)
1592                 get_page_foll(page);
1593         if (flags & FOLL_TOUCH) {
1594                 if ((flags & FOLL_WRITE) &&
1595                     !pte_dirty(pte) && !PageDirty(page))
1596                         set_page_dirty(page);
1597                 /*
1598                  * pte_mkyoung() would be more correct here, but atomic care
1599                  * is needed to avoid losing the dirty bit: it is easier to use
1600                  * mark_page_accessed().
1601                  */
1602                 mark_page_accessed(page);
1603         }
1604         if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1605                 /*
1606                  * The preliminary mapping check is mainly to avoid the
1607                  * pointless overhead of lock_page on the ZERO_PAGE
1608                  * which might bounce very badly if there is contention.
1609                  *
1610                  * If the page is already locked, we don't need to
1611                  * handle it now - vmscan will handle it later if and
1612                  * when it attempts to reclaim the page.
1613                  */
1614                 if (page->mapping && trylock_page(page)) {
1615                         lru_add_drain();  /* push cached pages to LRU */
1616                         /*
1617                          * Because we lock page here, and migration is
1618                          * blocked by the pte's page reference, and we
1619                          * know the page is still mapped, we don't even
1620                          * need to check for file-cache page truncation.
1621                          */
1622                         mlock_vma_page(page);
1623                         unlock_page(page);
1624                 }
1625         }
1626 unlock:
1627         pte_unmap_unlock(ptep, ptl);
1628 out:
1629         return page;
1630 
1631 bad_page:
1632         pte_unmap_unlock(ptep, ptl);
1633         return ERR_PTR(-EFAULT);
1634 
1635 no_page:
1636         pte_unmap_unlock(ptep, ptl);
1637         if (!pte_none(pte))
1638                 return page;
1639 
1640 no_page_table:
1641         /*
1642          * When core dumping an enormous anonymous area that nobody
1643          * has touched so far, we don't want to allocate unnecessary pages or
1644          * page tables.  Return error instead of NULL to skip handle_mm_fault,
1645          * then get_dump_page() will return NULL to leave a hole in the dump.
1646          * But we can only make this optimization where a hole would surely
1647          * be zero-filled if handle_mm_fault() actually did handle it.
1648          */
1649         if ((flags & FOLL_DUMP) &&
1650             (!vma->vm_ops || !vma->vm_ops->fault))
1651                 return ERR_PTR(-EFAULT);
1652         return page;
1653 }
1654 
1655 static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr)
1656 {
1657         return stack_guard_page_start(vma, addr) ||
1658                stack_guard_page_end(vma, addr+PAGE_SIZE);
1659 }
1660 
1661 /**
1662  * __get_user_pages() - pin user pages in memory
1663  * @tsk:        task_struct of target task
1664  * @mm:         mm_struct of target mm
1665  * @start:      starting user address
1666  * @nr_pages:   number of pages from start to pin
1667  * @gup_flags:  flags modifying pin behaviour
1668  * @pages:      array that receives pointers to the pages pinned.
1669  *              Should be at least nr_pages long. Or NULL, if caller
1670  *              only intends to ensure the pages are faulted in.
1671  * @vmas:       array of pointers to vmas corresponding to each page.
1672  *              Or NULL if the caller does not require them.
1673  * @nonblocking: whether waiting for disk IO or mmap_sem contention
1674  *
1675  * Returns number of pages pinned. This may be fewer than the number
1676  * requested. If nr_pages is 0 or negative, returns 0. If no pages
1677  * were pinned, returns -errno. Each page returned must be released
1678  * with a put_page() call when it is finished with. vmas will only
1679  * remain valid while mmap_sem is held.
1680  *
1681  * Must be called with mmap_sem held for read or write.
1682  *
1683  * __get_user_pages walks a process's page tables and takes a reference to
1684  * each struct page that each user address corresponds to at a given
1685  * instant. That is, it takes the page that would be accessed if a user
1686  * thread accesses the given user virtual address at that instant.
1687  *
1688  * This does not guarantee that the page exists in the user mappings when
1689  * __get_user_pages returns, and there may even be a completely different
1690  * page there in some cases (eg. if mmapped pagecache has been invalidated
1691  * and subsequently re faulted). However it does guarantee that the page
1692  * won't be freed completely. And mostly callers simply care that the page
1693  * contains data that was valid *at some point in time*. Typically, an IO
1694  * or similar operation cannot guarantee anything stronger anyway because
1695  * locks can't be held over the syscall boundary.
1696  *
1697  * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
1698  * the page is written to, set_page_dirty (or set_page_dirty_lock, as
1699  * appropriate) must be called after the page is finished with, and
1700  * before put_page is called.
1701  *
1702  * If @nonblocking != NULL, __get_user_pages will not wait for disk IO
1703  * or mmap_sem contention, and if waiting is needed to pin all pages,
1704  * *@nonblocking will be set to 0.
1705  *
1706  * In most cases, get_user_pages or get_user_pages_fast should be used
1707  * instead of __get_user_pages. __get_user_pages should be used only if
1708  * you need some special @gup_flags.
1709  */
1710 long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
1711                 unsigned long start, unsigned long nr_pages,
1712                 unsigned int gup_flags, struct page **pages,
1713                 struct vm_area_struct **vmas, int *nonblocking)
1714 {
1715         long i;
1716         unsigned long vm_flags;
1717         unsigned int page_mask;
1718 
1719         if (!nr_pages)
1720                 return 0;
1721 
1722         VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
1723 
1724         /*
1725          * If FOLL_FORCE and FOLL_NUMA are both set, handle_mm_fault
1726          * would be called on PROT_NONE ranges. We must never invoke
1727          * handle_mm_fault on PROT_NONE ranges or the NUMA hinting
1728          * page faults would unprotect the PROT_NONE ranges if
1729          * _PAGE_NUMA and _PAGE_PROTNONE are sharing the same pte/pmd
1730          * bitflag. So to avoid that, don't set FOLL_NUMA if
1731          * FOLL_FORCE is set.
1732          */
1733         if (!(gup_flags & FOLL_FORCE))
1734                 gup_flags |= FOLL_NUMA;
1735 
1736         i = 0;
1737 
1738         do {
1739                 struct vm_area_struct *vma;
1740 
1741                 vma = find_extend_vma(mm, start);
1742                 if (!vma && in_gate_area(mm, start)) {
1743                         unsigned long pg = start & PAGE_MASK;
1744                         pgd_t *pgd;
1745                         pud_t *pud;
1746                         pmd_t *pmd;
1747                         pte_t *pte;
1748 
1749                         /* user gate pages are read-only */
1750                         if (gup_flags & FOLL_WRITE)
1751                                 goto efault;
1752                         if (pg > TASK_SIZE)
1753                                 pgd = pgd_offset_k(pg);
1754                         else
1755                                 pgd = pgd_offset_gate(mm, pg);
1756                         BUG_ON(pgd_none(*pgd));
1757                         pud = pud_offset(pgd, pg);
1758                         BUG_ON(pud_none(*pud));
1759                         pmd = pmd_offset(pud, pg);
1760                         if (pmd_none(*pmd))
1761                                 goto efault;
1762                         VM_BUG_ON(pmd_trans_huge(*pmd));
1763                         pte = pte_offset_map(pmd, pg);
1764                         if (pte_none(*pte)) {
1765                                 pte_unmap(pte);
1766                                 goto efault;
1767                         }
1768                         vma = get_gate_vma(mm);
1769                         if (pages) {
1770                                 struct page *page;
1771 
1772                                 page = vm_normal_page(vma, start, *pte);
1773                                 if (!page) {
1774                                         if (!(gup_flags & FOLL_DUMP) &&
1775                                              is_zero_pfn(pte_pfn(*pte)))
1776                                                 page = pte_page(*pte);
1777                                         else {
1778                                                 pte_unmap(pte);
1779                                                 goto efault;
1780                                         }
1781                                 }
1782                                 pages[i] = page;
1783                                 get_page(page);
1784                         }
1785                         pte_unmap(pte);
1786                         page_mask = 0;
1787                         goto next_page;
1788                 }
1789 
1790                 if (!vma)
1791                         goto efault;
1792                 vm_flags = vma->vm_flags;
1793                 if (vm_flags & (VM_IO | VM_PFNMAP))
1794                         goto efault;
1795 
1796                 if (gup_flags & FOLL_WRITE) {
1797                         if (!(vm_flags & VM_WRITE)) {
1798                                 if (!(gup_flags & FOLL_FORCE))
1799                                         goto efault;
1800                                 /*
1801                                  * We used to let the write,force case do COW
1802                                  * in a VM_MAYWRITE VM_SHARED !VM_WRITE vma, so
1803                                  * ptrace could set a breakpoint in a read-only
1804                                  * mapping of an executable, without corrupting
1805                                  * the file (yet only when that file had been
1806                                  * opened for writing!).  Anon pages in shared
1807                                  * mappings are surprising: now just reject it.
1808                                  */
1809                                 if (!is_cow_mapping(vm_flags)) {
1810                                         WARN_ON_ONCE(vm_flags & VM_MAYWRITE);
1811                                         goto efault;
1812                                 }
1813                         }
1814                 } else {
1815                         if (!(vm_flags & VM_READ)) {
1816                                 if (!(gup_flags & FOLL_FORCE))
1817                                         goto efault;
1818                                 /*
1819                                  * Is there actually any vma we can reach here
1820                                  * which does not have VM_MAYREAD set?
1821                                  */
1822                                 if (!(vm_flags & VM_MAYREAD))
1823                                         goto efault;
1824                         }
1825                 }
1826 
1827                 if (is_vm_hugetlb_page(vma)) {
1828                         i = follow_hugetlb_page(mm, vma, pages, vmas,
1829                                         &start, &nr_pages, i, gup_flags);
1830                         continue;
1831                 }
1832 
1833                 do {
1834                         struct page *page;
1835                         unsigned int foll_flags = gup_flags;
1836                         unsigned int page_increm;
1837 
1838                         /*
1839                          * If we have a pending SIGKILL, don't keep faulting
1840                          * pages and potentially allocating memory.
1841                          */
1842                         if (unlikely(fatal_signal_pending(current)))
1843                                 return i ? i : -ERESTARTSYS;
1844 
1845                         cond_resched();
1846                         while (!(page = follow_page_mask(vma, start,
1847                                                 foll_flags, &page_mask))) {
1848                                 int ret;
1849                                 unsigned int fault_flags = 0;
1850 
1851                                 /* For mlock, just skip the stack guard page. */
1852                                 if (foll_flags & FOLL_MLOCK) {
1853                                         if (stack_guard_page(vma, start))
1854                                                 goto next_page;
1855                                 }
1856                                 if (foll_flags & FOLL_WRITE)
1857                                         fault_flags |= FAULT_FLAG_WRITE;
1858                                 if (nonblocking)
1859                                         fault_flags |= FAULT_FLAG_ALLOW_RETRY;
1860                                 if (foll_flags & FOLL_NOWAIT)
1861                                         fault_flags |= (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT);
1862 
1863                                 ret = handle_mm_fault(mm, vma, start,
1864                                                         fault_flags);
1865 
1866                                 if (ret & VM_FAULT_ERROR) {
1867                                         if (ret & VM_FAULT_OOM)
1868                                                 return i ? i : -ENOMEM;
1869                                         if (ret & (VM_FAULT_HWPOISON |
1870                                                    VM_FAULT_HWPOISON_LARGE)) {
1871                                                 if (i)
1872                                                         return i;
1873                                                 else if (gup_flags & FOLL_HWPOISON)
1874                                                         return -EHWPOISON;
1875                                                 else
1876                                                         return -EFAULT;
1877                                         }
1878                                         if (ret & VM_FAULT_SIGBUS)
1879                                                 goto efault;
1880                                         BUG();
1881                                 }
1882 
1883                                 if (tsk) {
1884                                         if (ret & VM_FAULT_MAJOR)
1885                                                 tsk->maj_flt++;
1886                                         else
1887                                                 tsk->min_flt++;
1888                                 }
1889 
1890                                 if (ret & VM_FAULT_RETRY) {
1891                                         if (nonblocking)
1892                                                 *nonblocking = 0;
1893                                         return i;
1894                                 }
1895 
1896                                 /*
1897                                  * The VM_FAULT_WRITE bit tells us that
1898                                  * do_wp_page has broken COW when necessary,
1899                                  * even if maybe_mkwrite decided not to set
1900                                  * pte_write. We can thus safely do subsequent
1901                                  * page lookups as if they were reads. But only
1902                                  * do so when looping for pte_write is futile:
1903                                  * in some cases userspace may also be wanting
1904                                  * to write to the gotten user page, which a
1905                                  * read fault here might prevent (a readonly
1906                                  * page might get reCOWed by userspace write).
1907                                  */
1908                                 if ((ret & VM_FAULT_WRITE) &&
1909                                     !(vma->vm_flags & VM_WRITE))
1910                                         foll_flags &= ~FOLL_WRITE;
1911 
1912                                 cond_resched();
1913                         }
1914                         if (IS_ERR(page))
1915                                 return i ? i : PTR_ERR(page);
1916                         if (pages) {
1917                                 pages[i] = page;
1918 
1919                                 flush_anon_page(vma, page, start);
1920                                 flush_dcache_page(page);
1921                                 page_mask = 0;
1922                         }
1923 next_page:
1924                         if (vmas) {
1925                                 vmas[i] = vma;
1926                                 page_mask = 0;
1927                         }
1928                         page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
1929                         if (page_increm > nr_pages)
1930                                 page_increm = nr_pages;
1931                         i += page_increm;
1932                         start += page_increm * PAGE_SIZE;
1933                         nr_pages -= page_increm;
1934                 } while (nr_pages && start < vma->vm_end);
1935         } while (nr_pages);
1936         return i;
1937 efault:
1938         return i ? : -EFAULT;
1939 }
1940 EXPORT_SYMBOL(__get_user_pages);
1941 
1942 /*
1943  * fixup_user_fault() - manually resolve a user page fault
1944  * @tsk:        the task_struct to use for page fault accounting, or
1945  *              NULL if faults are not to be recorded.
1946  * @mm:         mm_struct of target mm
1947  * @address:    user address
1948  * @fault_flags:flags to pass down to handle_mm_fault()
1949  *
1950  * This is meant to be called in the specific scenario where for locking reasons
1951  * we try to access user memory in atomic context (within a pagefault_disable()
1952  * section), this returns -EFAULT, and we want to resolve the user fault before
1953  * trying again.
1954  *
1955  * Typically this is meant to be used by the futex code.
1956  *
1957  * The main difference with get_user_pages() is that this function will
1958  * unconditionally call handle_mm_fault() which will in turn perform all the
1959  * necessary SW fixup of the dirty and young bits in the PTE, while
1960  * handle_mm_fault() only guarantees to update these in the struct page.
1961  *
1962  * This is important for some architectures where those bits also gate the
1963  * access permission to the page because they are maintained in software.  On
1964  * such architectures, gup() will not be enough to make a subsequent access
1965  * succeed.
1966  *
1967  * This should be called with the mm_sem held for read.
1968  */
1969 int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
1970                      unsigned long address, unsigned int fault_flags)
1971 {
1972         struct vm_area_struct *vma;
1973         vm_flags_t vm_flags;
1974         int ret;
1975 
1976         vma = find_extend_vma(mm, address);
1977         if (!vma || address < vma->vm_start)
1978                 return -EFAULT;
1979 
1980         vm_flags = (fault_flags & FAULT_FLAG_WRITE) ? VM_WRITE : VM_READ;
1981         if (!(vm_flags & vma->vm_flags))
1982                 return -EFAULT;
1983 
1984         ret = handle_mm_fault(mm, vma, address, fault_flags);
1985         if (ret & VM_FAULT_ERROR) {
1986                 if (ret & VM_FAULT_OOM)
1987                         return -ENOMEM;
1988                 if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
1989                         return -EHWPOISON;
1990                 if (ret & VM_FAULT_SIGBUS)
1991                         return -EFAULT;
1992                 BUG();
1993         }
1994         if (tsk) {
1995                 if (ret & VM_FAULT_MAJOR)
1996                         tsk->maj_flt++;
1997                 else
1998                         tsk->min_flt++;
1999         }
2000         return 0;
2001 }
2002 
2003 /*
2004  * get_user_pages() - pin user pages in memory
2005  * @tsk:        the task_struct to use for page fault accounting, or
2006  *              NULL if faults are not to be recorded.
2007  * @mm:         mm_struct of target mm
2008  * @start:      starting user address
2009  * @nr_pages:   number of pages from start to pin
2010  * @write:      whether pages will be written to by the caller
2011  * @force:      whether to force access even when user mapping is currently
2012  *              protected (but never forces write access to shared mapping).
2013  * @pages:      array that receives pointers to the pages pinned.
2014  *              Should be at least nr_pages long. Or NULL, if caller
2015  *              only intends to ensure the pages are faulted in.
2016  * @vmas:       array of pointers to vmas corresponding to each page.
2017  *              Or NULL if the caller does not require them.
2018  *
2019  * Returns number of pages pinned. This may be fewer than the number
2020  * requested. If nr_pages is 0 or negative, returns 0. If no pages
2021  * were pinned, returns -errno. Each page returned must be released
2022  * with a put_page() call when it is finished with. vmas will only
2023  * remain valid while mmap_sem is held.
2024  *
2025  * Must be called with mmap_sem held for read or write.
2026  *
2027  * get_user_pages walks a process's page tables and takes a reference to
2028  * each struct page that each user address corresponds to at a given
2029  * instant. That is, it takes the page that would be accessed if a user
2030  * thread accesses the given user virtual address at that instant.
2031  *
2032  * This does not guarantee that the page exists in the user mappings when
2033  * get_user_pages returns, and there may even be a completely different
2034  * page there in some cases (eg. if mmapped pagecache has been invalidated
2035  * and subsequently re faulted). However it does guarantee that the page
2036  * won't be freed completely. And mostly callers simply care that the page
2037  * contains data that was valid *at some point in time*. Typically, an IO
2038  * or similar operation cannot guarantee anything stronger anyway because
2039  * locks can't be held over the syscall boundary.
2040  *
2041  * If write=0, the page must not be written to. If the page is written to,
2042  * set_page_dirty (or set_page_dirty_lock, as appropriate) must be called
2043  * after the page is finished with, and before put_page is called.
2044  *
2045  * get_user_pages is typically used for fewer-copy IO operations, to get a
2046  * handle on the memory by some means other than accesses via the user virtual
2047  * addresses. The pages may be submitted for DMA to devices or accessed via
2048  * their kernel linear mapping (via the kmap APIs). Care should be taken to
2049  * use the correct cache flushing APIs.
2050  *
2051  * See also get_user_pages_fast, for performance critical applications.
2052  */
2053 long get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
2054                 unsigned long start, unsigned long nr_pages, int write,
2055                 int force, struct page **pages, struct vm_area_struct **vmas)
2056 {
2057         int flags = FOLL_TOUCH;
2058 
2059         if (pages)
2060                 flags |= FOLL_GET;
2061         if (write)
2062                 flags |= FOLL_WRITE;
2063         if (force)
2064                 flags |= FOLL_FORCE;
2065 
2066         return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas,
2067                                 NULL);
2068 }
2069 EXPORT_SYMBOL(get_user_pages);
2070 
2071 /**
2072  * get_dump_page() - pin user page in memory while writing it to core dump
2073  * @addr: user address
2074  *
2075  * Returns struct page pointer of user page pinned for dump,
2076  * to be freed afterwards by page_cache_release() or put_page().
2077  *
2078  * Returns NULL on any kind of failure - a hole must then be inserted into
2079  * the corefile, to preserve alignment with its headers; and also returns
2080  * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
2081  * allowing a hole to be left in the corefile to save diskspace.
2082  *
2083  * Called without mmap_sem, but after all other threads have been killed.
2084  */
2085 #ifdef CONFIG_ELF_CORE
2086 struct page *get_dump_page(unsigned long addr)
2087 {
2088         struct vm_area_struct *vma;
2089         struct page *page;
2090 
2091         if (__get_user_pages(current, current->mm, addr, 1,
2092                              FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma,
2093                              NULL) < 1)
2094                 return NULL;
2095         flush_cache_page(vma, addr, page_to_pfn(page));
2096         return page;
2097 }
2098 #endif /* CONFIG_ELF_CORE */
2099 
2100 pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr,
2101                         spinlock_t **ptl)
2102 {
2103         pgd_t * pgd = pgd_offset(mm, addr);
2104         pud_t * pud = pud_alloc(mm, pgd, addr);
2105         if (pud) {
2106                 pmd_t * pmd = pmd_alloc(mm, pud, addr);
2107                 if (pmd) {
2108                         VM_BUG_ON(pmd_trans_huge(*pmd));
2109                         return pte_alloc_map_lock(mm, pmd, addr, ptl);
2110                 }
2111         }
2112         return NULL;
2113 }
2114 
2115 /*
2116  * This is the old fallback for page remapping.
2117  *
2118  * For historical reasons, it only allows reserved pages. Only
2119  * old drivers should use this, and they needed to mark their
2120  * pages reserved for the old functions anyway.
2121  */
2122 static int insert_page(struct vm_area_struct *vma, unsigned long addr,
2123                         struct page *page, pgprot_t prot)
2124 {
2125         struct mm_struct *mm = vma->vm_mm;
2126         int retval;
2127         pte_t *pte;
2128         spinlock_t *ptl;
2129 
2130         retval = -EINVAL;
2131         if (PageAnon(page))
2132                 goto out;
2133         retval = -ENOMEM;
2134         flush_dcache_page(page);
2135         pte = get_locked_pte(mm, addr, &ptl);
2136         if (!pte)
2137                 goto out;
2138         retval = -EBUSY;
2139         if (!pte_none(*pte))
2140                 goto out_unlock;
2141 
2142         /* Ok, finally just insert the thing.. */
2143         get_page(page);
2144         inc_mm_counter_fast(mm, MM_FILEPAGES);
2145         page_add_file_rmap(page);
2146         set_pte_at(mm, addr, pte, mk_pte(page, prot));
2147 
2148         retval = 0;
2149         pte_unmap_unlock(pte, ptl);
2150         return retval;
2151 out_unlock:
2152         pte_unmap_unlock(pte, ptl);
2153 out:
2154         return retval;
2155 }
2156 
2157 /**
2158  * vm_insert_page - insert single page into user vma
2159  * @vma: user vma to map to
2160  * @addr: target user address of this page
2161  * @page: source kernel page
2162  *
2163  * This allows drivers to insert individual pages they've allocated
2164  * into a user vma.
2165  *
2166  * The page has to be a nice clean _individual_ kernel allocation.
2167  * If you allocate a compound page, you need to have marked it as
2168  * such (__GFP_COMP), or manually just split the page up yourself
2169  * (see split_page()).
2170  *
2171  * NOTE! Traditionally this was done with "remap_pfn_range()" which
2172  * took an arbitrary page protection parameter. This doesn't allow
2173  * that. Your vma protection will have to be set up correctly, which
2174  * means that if you want a shared writable mapping, you'd better
2175  * ask for a shared writable mapping!
2176  *
2177  * The page does not need to be reserved.
2178  *
2179  * Usually this function is called from f_op->mmap() handler
2180  * under mm->mmap_sem write-lock, so it can change vma->vm_flags.
2181  * Caller must set VM_MIXEDMAP on vma if it wants to call this
2182  * function from other places, for example from page-fault handler.
2183  */
2184 int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
2185                         struct page *page)
2186 {
2187         if (addr < vma->vm_start || addr >= vma->vm_end)
2188                 return -EFAULT;
2189         if (!page_count(page))
2190                 return -EINVAL;
2191         if (!(vma->vm_flags & VM_MIXEDMAP)) {
2192                 BUG_ON(down_read_trylock(&vma->vm_mm->mmap_sem));
2193                 BUG_ON(vma->vm_flags & VM_PFNMAP);
2194                 vma->vm_flags |= VM_MIXEDMAP;
2195         }
2196         return insert_page(vma, addr, page, vma->vm_page_prot);
2197 }
2198 EXPORT_SYMBOL(vm_insert_page);
2199 
2200 static int insert_pfn(struct vm_area_struct *vma, unsigned long addr,
2201                         unsigned long pfn, pgprot_t prot)
2202 {
2203         struct mm_struct *mm = vma->vm_mm;
2204         int retval;
2205         pte_t *pte, entry;
2206         spinlock_t *ptl;
2207 
2208         retval = -ENOMEM;
2209         pte = get_locked_pte(mm, addr, &ptl);
2210         if (!pte)
2211                 goto out;
2212         retval = -EBUSY;
2213         if (!pte_none(*pte))
2214                 goto out_unlock;
2215 
2216         /* Ok, finally just insert the thing.. */
2217         entry = pte_mkspecial(pfn_pte(pfn, prot));
2218         set_pte_at(mm, addr, pte, entry);
2219         update_mmu_cache(vma, addr, pte); /* XXX: why not for insert_page? */
2220 
2221         retval = 0;
2222 out_unlock:
2223         pte_unmap_unlock(pte, ptl);
2224 out:
2225         return retval;
2226 }
2227 
2228 /**
2229  * vm_insert_pfn - insert single pfn into user vma
2230  * @vma: user vma to map to
2231  * @addr: target user address of this page
2232  * @pfn: source kernel pfn
2233  *
2234  * Similar to vm_insert_page, this allows drivers to insert individual pages
2235  * they've allocated into a user vma. Same comments apply.
2236  *
2237  * This function should only be called from a vm_ops->fault handler, and
2238  * in that case the handler should return NULL.
2239  *
2240  * vma cannot be a COW mapping.
2241  *
2242  * As this is called only for pages that do not currently exist, we
2243  * do not need to flush old virtual caches or the TLB.
2244  */
2245 int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
2246                         unsigned long pfn)
2247 {
2248         int ret;
2249         pgprot_t pgprot = vma->vm_page_prot;
2250         /*
2251          * Technically, architectures with pte_special can avoid all these
2252          * restrictions (same for remap_pfn_range).  However we would like
2253          * consistency in testing and feature parity among all, so we should
2254          * try to keep these invariants in place for everybody.
2255          */
2256         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
2257         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
2258                                                 (VM_PFNMAP|VM_MIXEDMAP));
2259         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
2260         BUG_ON((vma->vm_flags & VM_MIXEDMAP) && pfn_valid(pfn));
2261 
2262         if (addr < vma->vm_start || addr >= vma->vm_end)
2263                 return -EFAULT;
2264         if (track_pfn_insert(vma, &pgprot, pfn))
2265                 return -EINVAL;
2266 
2267         ret = insert_pfn(vma, addr, pfn, pgprot);
2268 
2269         return ret;
2270 }
2271 EXPORT_SYMBOL(vm_insert_pfn);
2272 
2273 int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
2274                         unsigned long pfn)
2275 {
2276         BUG_ON(!(vma->vm_flags & VM_MIXEDMAP));
2277 
2278         if (addr < vma->vm_start || addr >= vma->vm_end)
2279                 return -EFAULT;
2280 
2281         /*
2282          * If we don't have pte special, then we have to use the pfn_valid()
2283          * based VM_MIXEDMAP scheme (see vm_normal_page), and thus we *must*
2284          * refcount the page if pfn_valid is true (hence insert_page rather
2285          * than insert_pfn).  If a zero_pfn were inserted into a VM_MIXEDMAP
2286          * without pte special, it would there be refcounted as a normal page.
2287          */
2288         if (!HAVE_PTE_SPECIAL && pfn_valid(pfn)) {
2289                 struct page *page;
2290 
2291                 page = pfn_to_page(pfn);
2292                 return insert_page(vma, addr, page, vma->vm_page_prot);
2293         }
2294         return insert_pfn(vma, addr, pfn, vma->vm_page_prot);
2295 }
2296 EXPORT_SYMBOL(vm_insert_mixed);
2297 
2298 /*
2299  * maps a range of physical memory into the requested pages. the old
2300  * mappings are removed. any references to nonexistent pages results
2301  * in null mappings (currently treated as "copy-on-access")
2302  */
2303 static int remap_pte_range(struct mm_struct *mm, pmd_t *pmd,
2304                         unsigned long addr, unsigned long end,
2305                         unsigned long pfn, pgprot_t prot)
2306 {
2307         pte_t *pte;
2308         spinlock_t *ptl;
2309 
2310         pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
2311         if (!pte)
2312                 return -ENOMEM;
2313         arch_enter_lazy_mmu_mode();
2314         do {
2315                 BUG_ON(!pte_none(*pte));
2316                 set_pte_at(mm, addr, pte, pte_mkspecial(pfn_pte(pfn, prot)));
2317                 pfn++;
2318         } while (pte++, addr += PAGE_SIZE, addr != end);
2319         arch_leave_lazy_mmu_mode();
2320         pte_unmap_unlock(pte - 1, ptl);
2321         return 0;
2322 }
2323 
2324 static inline int remap_pmd_range(struct mm_struct *mm, pud_t *pud,
2325                         unsigned long addr, unsigned long end,
2326                         unsigned long pfn, pgprot_t prot)
2327 {
2328         pmd_t *pmd;
2329         unsigned long next;
2330 
2331         pfn -= addr >> PAGE_SHIFT;
2332         pmd = pmd_alloc(mm, pud, addr);
2333         if (!pmd)
2334                 return -ENOMEM;
2335         VM_BUG_ON(pmd_trans_huge(*pmd));
2336         do {
2337                 next = pmd_addr_end(addr, end);
2338                 if (remap_pte_range(mm, pmd, addr, next,
2339                                 pfn + (addr >> PAGE_SHIFT), prot))
2340                         return -ENOMEM;
2341         } while (pmd++, addr = next, addr != end);
2342         return 0;
2343 }
2344 
2345 static inline int remap_pud_range(struct mm_struct *mm, pgd_t *pgd,
2346                         unsigned long addr, unsigned long end,
2347                         unsigned long pfn, pgprot_t prot)
2348 {
2349         pud_t *pud;
2350         unsigned long next;
2351 
2352         pfn -= addr >> PAGE_SHIFT;
2353         pud = pud_alloc(mm, pgd, addr);
2354         if (!pud)
2355                 return -ENOMEM;
2356         do {
2357                 next = pud_addr_end(addr, end);
2358                 if (remap_pmd_range(mm, pud, addr, next,
2359                                 pfn + (addr >> PAGE_SHIFT), prot))
2360                         return -ENOMEM;
2361         } while (pud++, addr = next, addr != end);
2362         return 0;
2363 }
2364 
2365 /**
2366  * remap_pfn_range - remap kernel memory to userspace
2367  * @vma: user vma to map to
2368  * @addr: target user address to start at
2369  * @pfn: physical address of kernel memory
2370  * @size: size of map area
2371  * @prot: page protection flags for this mapping
2372  *
2373  *  Note: this is only safe if the mm semaphore is held when called.
2374  */
2375 int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
2376                     unsigned long pfn, unsigned long size, pgprot_t prot)
2377 {
2378         pgd_t *pgd;
2379         unsigned long next;
2380         unsigned long end = addr + PAGE_ALIGN(size);
2381         struct mm_struct *mm = vma->vm_mm;
2382         int err;
2383 
2384         /*
2385          * Physically remapped pages are special. Tell the
2386          * rest of the world about it:
2387          *   VM_IO tells people not to look at these pages
2388          *      (accesses can have side effects).
2389          *   VM_PFNMAP tells the core MM that the base pages are just
2390          *      raw PFN mappings, and do not have a "struct page" associated
2391          *      with them.
2392          *   VM_DONTEXPAND
2393          *      Disable vma merging and expanding with mremap().
2394          *   VM_DONTDUMP
2395          *      Omit vma from core dump, even when VM_IO turned off.
2396          *
2397          * There's a horrible special case to handle copy-on-write
2398          * behaviour that some programs depend on. We mark the "original"
2399          * un-COW'ed pages by matching them up with "vma->vm_pgoff".
2400          * See vm_normal_page() for details.
2401          */
2402         if (is_cow_mapping(vma->vm_flags)) {
2403                 if (addr != vma->vm_start || end != vma->vm_end)
2404                         return -EINVAL;
2405                 vma->vm_pgoff = pfn;
2406         }
2407 
2408         err = track_pfn_remap(vma, &prot, pfn, addr, PAGE_ALIGN(size));
2409         if (err)
2410                 return -EINVAL;
2411 
2412         vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
2413 
2414         BUG_ON(addr >= end);
2415         pfn -= addr >> PAGE_SHIFT;
2416         pgd = pgd_offset(mm, addr);
2417         flush_cache_range(vma, addr, end);
2418         do {
2419                 next = pgd_addr_end(addr, end);
2420                 err = remap_pud_range(mm, pgd, addr, next,
2421                                 pfn + (addr >> PAGE_SHIFT), prot);
2422                 if (err)
2423                         break;
2424         } while (pgd++, addr = next, addr != end);
2425 
2426         if (err)
2427                 untrack_pfn(vma, pfn, PAGE_ALIGN(size));
2428 
2429         return err;
2430 }
2431 EXPORT_SYMBOL(remap_pfn_range);
2432 
2433 /**
2434  * vm_iomap_memory - remap memory to userspace
2435  * @vma: user vma to map to
2436  * @start: start of area
2437  * @len: size of area
2438  *
2439  * This is a simplified io_remap_pfn_range() for common driver use. The
2440  * driver just needs to give us the physical memory range to be mapped,
2441  * we'll figure out the rest from the vma information.
2442  *
2443  * NOTE! Some drivers might want to tweak vma->vm_page_prot first to get
2444  * whatever write-combining details or similar.
2445  */
2446 int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len)
2447 {
2448         unsigned long vm_len, pfn, pages;
2449 
2450         /* Check that the physical memory area passed in looks valid */
2451         if (start + len < start)
2452                 return -EINVAL;
2453         /*
2454          * You *really* shouldn't map things that aren't page-aligned,
2455          * but we've historically allowed it because IO memory might
2456          * just have smaller alignment.
2457          */
2458         len += start & ~PAGE_MASK;
2459         pfn = start >> PAGE_SHIFT;
2460         pages = (len + ~PAGE_MASK) >> PAGE_SHIFT;
2461         if (pfn + pages < pfn)
2462                 return -EINVAL;
2463 
2464         /* We start the mapping 'vm_pgoff' pages into the area */
2465         if (vma->vm_pgoff > pages)
2466                 return -EINVAL;
2467         pfn += vma->vm_pgoff;
2468         pages -= vma->vm_pgoff;
2469 
2470         /* Can we fit all of the mapping? */
2471         vm_len = vma->vm_end - vma->vm_start;
2472         if (vm_len >> PAGE_SHIFT > pages)
2473                 return -EINVAL;
2474 
2475         /* Ok, let it rip */
2476         return io_remap_pfn_range(vma, vma->vm_start, pfn, vm_len, vma->vm_page_prot);
2477 }
2478 EXPORT_SYMBOL(vm_iomap_memory);
2479 
2480 static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
2481                                      unsigned long addr, unsigned long end,
2482                                      pte_fn_t fn, void *data)
2483 {
2484         pte_t *pte;
2485         int err;
2486         pgtable_t token;
2487         spinlock_t *uninitialized_var(ptl);
2488 
2489         pte = (mm == &init_mm) ?
2490                 pte_alloc_kernel(pmd, addr) :
2491                 pte_alloc_map_lock(mm, pmd, addr, &ptl);
2492         if (!pte)
2493                 return -ENOMEM;
2494 
2495         BUG_ON(pmd_huge(*pmd));
2496 
2497         arch_enter_lazy_mmu_mode();
2498 
2499         token = pmd_pgtable(*pmd);
2500 
2501         do {
2502                 err = fn(pte++, token, addr, data);
2503                 if (err)
2504                         break;
2505         } while (addr += PAGE_SIZE, addr != end);
2506 
2507         arch_leave_lazy_mmu_mode();
2508 
2509         if (mm != &init_mm)
2510                 pte_unmap_unlock(pte-1, ptl);
2511         return err;
2512 }
2513 
2514 static int apply_to_pmd_range(struct mm_struct *mm, pud_t *pud,
2515                                      unsigned long addr, unsigned long end,
2516                                      pte_fn_t fn, void *data)
2517 {
2518         pmd_t *pmd;
2519         unsigned long next;
2520         int err;
2521 
2522         BUG_ON(pud_huge(*pud));
2523 
2524         pmd = pmd_alloc(mm, pud, addr);
2525         if (!pmd)
2526                 return -ENOMEM;
2527         do {
2528                 next = pmd_addr_end(addr, end);
2529                 err = apply_to_pte_range(mm, pmd, addr, next, fn, data);
2530                 if (err)
2531                         break;
2532         } while (pmd++, addr = next, addr != end);
2533         return err;
2534 }
2535 
2536 static int apply_to_pud_range(struct mm_struct *mm, pgd_t *pgd,
2537                                      unsigned long addr, unsigned long end,
2538                                      pte_fn_t fn, void *data)
2539 {
2540         pud_t *pud;
2541         unsigned long next;
2542         int err;
2543 
2544         pud = pud_alloc(mm, pgd, addr);
2545         if (!pud)
2546                 return -ENOMEM;
2547         do {
2548                 next = pud_addr_end(addr, end);
2549                 err = apply_to_pmd_range(mm, pud, addr, next, fn, data);
2550                 if (err)
2551                         break;
2552         } while (pud++, addr = next, addr != end);
2553         return err;
2554 }
2555 
2556 /*
2557  * Scan a region of virtual memory, filling in page tables as necessary
2558  * and calling a provided function on each leaf page table.
2559  */
2560 int apply_to_page_range(struct mm_struct *mm, unsigned long addr,
2561                         unsigned long size, pte_fn_t fn, void *data)
2562 {
2563         pgd_t *pgd;
2564         unsigned long next;
2565         unsigned long end = addr + size;
2566         int err;
2567 
2568         BUG_ON(addr >= end);
2569         pgd = pgd_offset(mm, addr);
2570         do {
2571                 next = pgd_addr_end(addr, end);
2572                 err = apply_to_pud_range(mm, pgd, addr, next, fn, data);
2573                 if (err)
2574                         break;
2575         } while (pgd++, addr = next, addr != end);
2576 
2577         return err;
2578 }
2579 EXPORT_SYMBOL_GPL(apply_to_page_range);
2580 
2581 /*
2582  * handle_pte_fault chooses page fault handler according to an entry
2583  * which was read non-atomically.  Before making any commitment, on
2584  * those architectures or configurations (e.g. i386 with PAE) which
2585  * might give a mix of unmatched parts, do_swap_page and do_nonlinear_fault
2586  * must check under lock before unmapping the pte and proceeding
2587  * (but do_wp_page is only called after already making such a check;
2588  * and do_anonymous_page can safely check later on).
2589  */
2590 static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd,
2591                                 pte_t *page_table, pte_t orig_pte)
2592 {
2593         int same = 1;
2594 #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
2595         if (sizeof(pte_t) > sizeof(unsigned long)) {
2596                 spinlock_t *ptl = pte_lockptr(mm, pmd);
2597                 spin_lock(ptl);
2598                 same = pte_same(*page_table, orig_pte);
2599                 spin_unlock(ptl);
2600         }
2601 #endif
2602         pte_unmap(page_table);
2603         return same;
2604 }
2605 
2606 static inline void cow_user_page(struct page *dst, struct page *src, unsigned long va, struct vm_area_struct *vma)
2607 {
2608         debug_dma_assert_idle(src);
2609 
2610         /*
2611          * If the source page was a PFN mapping, we don't have
2612          * a "struct page" for it. We do a best-effort copy by
2613          * just copying from the original user address. If that
2614          * fails, we just zero-fill it. Live with it.
2615          */
2616         if (unlikely(!src)) {
2617                 void *kaddr = kmap_atomic(dst);
2618                 void __user *uaddr = (void __user *)(va & PAGE_MASK);
2619 
2620                 /*
2621                  * This really shouldn't fail, because the page is there
2622                  * in the page tables. But it might just be unreadable,
2623                  * in which case we just give up and fill the result with
2624                  * zeroes.
2625                  */
2626                 if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE))
2627                         clear_page(kaddr);
2628                 kunmap_atomic(kaddr);
2629                 flush_dcache_page(dst);
2630         } else
2631                 copy_user_highpage(dst, src, va, vma);
2632 }
2633 
2634 /*
2635  * Notify the address space that the page is about to become writable so that
2636  * it can prohibit this or wait for the page to get into an appropriate state.
2637  *
2638  * We do this without the lock held, so that it can sleep if it needs to.
2639  */
2640 static int do_page_mkwrite(struct vm_area_struct *vma, struct page *page,
2641                unsigned long address)
2642 {
2643         struct vm_fault vmf;
2644         int ret;
2645 
2646         vmf.virtual_address = (void __user *)(address & PAGE_MASK);
2647         vmf.pgoff = page->index;
2648         vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
2649         vmf.page = page;
2650 
2651         ret = vma->vm_ops->page_mkwrite(vma, &vmf);
2652         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))
2653                 return ret;
2654         if (unlikely(!(ret & VM_FAULT_LOCKED))) {
2655                 lock_page(page);
2656                 if (!page->mapping) {
2657                         unlock_page(page);
2658                         return 0; /* retry */
2659                 }
2660                 ret |= VM_FAULT_LOCKED;
2661         } else
2662                 VM_BUG_ON_PAGE(!PageLocked(page), page);
2663         return ret;
2664 }
2665 
2666 /*
2667  * This routine handles present pages, when users try to write
2668  * to a shared page. It is done by copying the page to a new address
2669  * and decrementing the shared-page counter for the old page.
2670  *
2671  * Note that this routine assumes that the protection checks have been
2672  * done by the caller (the low-level page fault routine in most cases).
2673  * Thus we can safely just mark it writable once we've done any necessary
2674  * COW.
2675  *
2676  * We also mark the page dirty at this point even though the page will
2677  * change only once the write actually happens. This avoids a few races,
2678  * and potentially makes it more efficient.
2679  *
2680  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2681  * but allow concurrent faults), with pte both mapped and locked.
2682  * We return with mmap_sem still held, but pte unmapped and unlocked.
2683  */
2684 static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
2685                 unsigned long address, pte_t *page_table, pmd_t *pmd,
2686                 spinlock_t *ptl, pte_t orig_pte)
2687         __releases(ptl)
2688 {
2689         struct page *old_page, *new_page = NULL;
2690         pte_t entry;
2691         int ret = 0;
2692         int page_mkwrite = 0;
2693         struct page *dirty_page = NULL;
2694         unsigned long mmun_start = 0;   /* For mmu_notifiers */
2695         unsigned long mmun_end = 0;     /* For mmu_notifiers */
2696 
2697         old_page = vm_normal_page(vma, address, orig_pte);
2698         if (!old_page) {
2699                 /*
2700                  * VM_MIXEDMAP !pfn_valid() case
2701                  *
2702                  * We should not cow pages in a shared writeable mapping.
2703                  * Just mark the pages writable as we can't do any dirty
2704                  * accounting on raw pfn maps.
2705                  */
2706                 if ((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
2707                                      (VM_WRITE|VM_SHARED))
2708                         goto reuse;
2709                 goto gotten;
2710         }
2711 
2712         /*
2713          * Take out anonymous pages first, anonymous shared vmas are
2714          * not dirty accountable.
2715          */
2716         if (PageAnon(old_page) && !PageKsm(old_page)) {
2717                 if (!trylock_page(old_page)) {
2718                         page_cache_get(old_page);
2719                         pte_unmap_unlock(page_table, ptl);
2720                         lock_page(old_page);
2721                         page_table = pte_offset_map_lock(mm, pmd, address,
2722                                                          &ptl);
2723                         if (!pte_same(*page_table, orig_pte)) {
2724                                 unlock_page(old_page);
2725                                 goto unlock;
2726                         }
2727                         page_cache_release(old_page);
2728                 }
2729                 if (reuse_swap_page(old_page)) {
2730                         /*
2731                          * The page is all ours.  Move it to our anon_vma so
2732                          * the rmap code will not search our parent or siblings.
2733                          * Protected against the rmap code by the page lock.
2734                          */
2735                         page_move_anon_rmap(old_page, vma, address);
2736                         unlock_page(old_page);
2737                         goto reuse;
2738                 }
2739                 unlock_page(old_page);
2740         } else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
2741                                         (VM_WRITE|VM_SHARED))) {
2742                 /*
2743                  * Only catch write-faults on shared writable pages,
2744                  * read-only shared pages can get COWed by
2745                  * get_user_pages(.write=1, .force=1).
2746                  */
2747                 if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
2748                         int tmp;
2749                         page_cache_get(old_page);
2750                         pte_unmap_unlock(page_table, ptl);
2751                         tmp = do_page_mkwrite(vma, old_page, address);
2752                         if (unlikely(!tmp || (tmp &
2753                                         (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
2754                                 page_cache_release(old_page);
2755                                 return tmp;
2756                         }
2757                         /*
2758                          * Since we dropped the lock we need to revalidate
2759                          * the PTE as someone else may have changed it.  If
2760                          * they did, we just return, as we can count on the
2761                          * MMU to tell us if they didn't also make it writable.
2762                          */
2763                         page_table = pte_offset_map_lock(mm, pmd, address,
2764                                                          &ptl);
2765                         if (!pte_same(*page_table, orig_pte)) {
2766                                 unlock_page(old_page);
2767                                 goto unlock;
2768                         }
2769 
2770                         page_mkwrite = 1;
2771                 }
2772                 dirty_page = old_page;
2773                 get_page(dirty_page);
2774 
2775 reuse:
2776                 /*
2777                  * Clear the pages cpupid information as the existing
2778                  * information potentially belongs to a now completely
2779                  * unrelated process.
2780                  */
2781                 if (old_page)
2782                         page_cpupid_xchg_last(old_page, (1 << LAST_CPUPID_SHIFT) - 1);
2783 
2784                 flush_cache_page(vma, address, pte_pfn(orig_pte));
2785                 entry = pte_mkyoung(orig_pte);
2786                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2787                 if (ptep_set_access_flags(vma, address, page_table, entry,1))
2788                         update_mmu_cache(vma, address, page_table);
2789                 pte_unmap_unlock(page_table, ptl);
2790                 ret |= VM_FAULT_WRITE;
2791 
2792                 if (!dirty_page)
2793                         return ret;
2794 
2795                 /*
2796                  * Yes, Virginia, this is actually required to prevent a race
2797                  * with clear_page_dirty_for_io() from clearing the page dirty
2798                  * bit after it clear all dirty ptes, but before a racing
2799                  * do_wp_page installs a dirty pte.
2800                  *
2801                  * do_shared_fault is protected similarly.
2802                  */
2803                 if (!page_mkwrite) {
2804                         wait_on_page_locked(dirty_page);
2805                         set_page_dirty_balance(dirty_page);
2806                         /* file_update_time outside page_lock */
2807                         if (vma->vm_file)
2808                                 file_update_time(vma->vm_file);
2809                 }
2810                 put_page(dirty_page);
2811                 if (page_mkwrite) {
2812                         struct address_space *mapping = dirty_page->mapping;
2813 
2814                         set_page_dirty(dirty_page);
2815                         unlock_page(dirty_page);
2816                         page_cache_release(dirty_page);
2817                         if (mapping)    {
2818                                 /*
2819                                  * Some device drivers do not set page.mapping
2820                                  * but still dirty their pages
2821                                  */
2822                                 balance_dirty_pages_ratelimited(mapping);
2823                         }
2824                 }
2825 
2826                 return ret;
2827         }
2828 
2829         /*
2830          * Ok, we need to copy. Oh, well..
2831          */
2832         page_cache_get(old_page);
2833 gotten:
2834         pte_unmap_unlock(page_table, ptl);
2835 
2836         if (unlikely(anon_vma_prepare(vma)))
2837                 goto oom;
2838 
2839         if (is_zero_pfn(pte_pfn(orig_pte))) {
2840                 new_page = alloc_zeroed_user_highpage_movable(vma, address);
2841                 if (!new_page)
2842                         goto oom;
2843         } else {
2844                 new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
2845                 if (!new_page)
2846                         goto oom;
2847                 cow_user_page(new_page, old_page, address, vma);
2848         }
2849         __SetPageUptodate(new_page);
2850 
2851         if (mem_cgroup_charge_anon(new_page, mm, GFP_KERNEL))
2852                 goto oom_free_new;
2853 
2854         mmun_start  = address & PAGE_MASK;
2855         mmun_end    = mmun_start + PAGE_SIZE;
2856         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2857 
2858         /*
2859          * Re-check the pte - we dropped the lock
2860          */
2861         page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2862         if (likely(pte_same(*page_table, orig_pte))) {
2863                 if (old_page) {
2864                         if (!PageAnon(old_page)) {
2865                                 dec_mm_counter_fast(mm, MM_FILEPAGES);
2866                                 inc_mm_counter_fast(mm, MM_ANONPAGES);
2867                         }
2868                 } else
2869                         inc_mm_counter_fast(mm, MM_ANONPAGES);
2870                 flush_cache_page(vma, address, pte_pfn(orig_pte));
2871                 entry = mk_pte(new_page, vma->vm_page_prot);
2872                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2873                 /*
2874                  * Clear the pte entry and flush it first, before updating the
2875                  * pte with the new entry. This will avoid a race condition
2876                  * seen in the presence of one thread doing SMC and another
2877                  * thread doing COW.
2878                  */
2879                 ptep_clear_flush(vma, address, page_table);
2880                 page_add_new_anon_rmap(new_page, vma, address);
2881                 /*
2882                  * We call the notify macro here because, when using secondary
2883                  * mmu page tables (such as kvm shadow page tables), we want the
2884                  * new page to be mapped directly into the secondary page table.
2885                  */
2886                 set_pte_at_notify(mm, address, page_table, entry);
2887                 update_mmu_cache(vma, address, page_table);
2888                 if (old_page) {
2889                         /*
2890                          * Only after switching the pte to the new page may
2891                          * we remove the mapcount here. Otherwise another
2892                          * process may come and find the rmap count decremented
2893                          * before the pte is switched to the new page, and
2894                          * "reuse" the old page writing into it while our pte
2895                          * here still points into it and can be read by other
2896                          * threads.
2897                          *
2898                          * The critical issue is to order this
2899                          * page_remove_rmap with the ptp_clear_flush above.
2900                          * Those stores are ordered by (if nothing else,)
2901                          * the barrier present in the atomic_add_negative
2902                          * in page_remove_rmap.
2903                          *
2904                          * Then the TLB flush in ptep_clear_flush ensures that
2905                          * no process can access the old page before the
2906                          * decremented mapcount is visible. And the old page
2907                          * cannot be reused until after the decremented
2908                          * mapcount is visible. So transitively, TLBs to
2909                          * old page will be flushed before it can be reused.
2910                          */
2911                         page_remove_rmap(old_page);
2912                 }
2913 
2914                 /* Free the old page.. */
2915                 new_page = old_page;
2916                 ret |= VM_FAULT_WRITE;
2917         } else
2918                 mem_cgroup_uncharge_page(new_page);
2919 
2920         if (new_page)
2921                 page_cache_release(new_page);
2922 unlock:
2923         pte_unmap_unlock(page_table, ptl);
2924         if (mmun_end > mmun_start)
2925                 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2926         if (old_page) {
2927                 /*
2928                  * Don't let another task, with possibly unlocked vma,
2929                  * keep the mlocked page.
2930                  */
2931                 if ((ret & VM_FAULT_WRITE) && (vma->vm_flags & VM_LOCKED)) {
2932                         lock_page(old_page);    /* LRU manipulation */
2933                         munlock_vma_page(old_page);
2934                         unlock_page(old_page);
2935                 }
2936                 page_cache_release(old_page);
2937         }
2938         return ret;
2939 oom_free_new:
2940         page_cache_release(new_page);
2941 oom:
2942         if (old_page)
2943                 page_cache_release(old_page);
2944         return VM_FAULT_OOM;
2945 }
2946 
2947 static void unmap_mapping_range_vma(struct vm_area_struct *vma,
2948                 unsigned long start_addr, unsigned long end_addr,
2949                 struct zap_details *details)
2950 {
2951         zap_page_range_single(vma, start_addr, end_addr - start_addr, details);
2952 }
2953 
2954 static inline void unmap_mapping_range_tree(struct rb_root *root,
2955                                             struct zap_details *details)
2956 {
2957         struct vm_area_struct *vma;
2958         pgoff_t vba, vea, zba, zea;
2959 
2960         vma_interval_tree_foreach(vma, root,
2961                         details->first_index, details->last_index) {
2962 
2963                 vba = vma->vm_pgoff;
2964                 vea = vba + vma_pages(vma) - 1;
2965                 /* Assume for now that PAGE_CACHE_SHIFT == PAGE_SHIFT */
2966                 zba = details->first_index;
2967                 if (zba < vba)
2968                         zba = vba;
2969                 zea = details->last_index;
2970                 if (zea > vea)
2971                         zea = vea;
2972 
2973                 unmap_mapping_range_vma(vma,
2974                         ((zba - vba) << PAGE_SHIFT) + vma->vm_start,
2975                         ((zea - vba + 1) << PAGE_SHIFT) + vma->vm_start,
2976                                 details);
2977         }
2978 }
2979 
2980 static inline void unmap_mapping_range_list(struct list_head *head,
2981                                             struct zap_details *details)
2982 {
2983         struct vm_area_struct *vma;
2984 
2985         /*
2986          * In nonlinear VMAs there is no correspondence between virtual address
2987          * offset and file offset.  So we must perform an exhaustive search
2988          * across *all* the pages in each nonlinear VMA, not just the pages
2989          * whose virtual address lies outside the file truncation point.
2990          */
2991         list_for_each_entry(vma, head, shared.nonlinear) {
2992                 details->nonlinear_vma = vma;
2993                 unmap_mapping_range_vma(vma, vma->vm_start, vma->vm_end, details);
2994         }
2995 }
2996 
2997 /**
2998  * unmap_mapping_range - unmap the portion of all mmaps in the specified address_space corresponding to the specified page range in the underlying file.
2999  * @mapping: the address space containing mmaps to be unmapped.
3000  * @holebegin: byte in first page to unmap, relative to the start of
3001  * the underlying file.  This will be rounded down to a PAGE_SIZE
3002  * boundary.  Note that this is different from truncate_pagecache(), which
3003  * must keep the partial page.  In contrast, we must get rid of
3004  * partial pages.
3005  * @holelen: size of prospective hole in bytes.  This will be rounded
3006  * up to a PAGE_SIZE boundary.  A holelen of zero truncates to the
3007  * end of the file.
3008  * @even_cows: 1 when truncating a file, unmap even private COWed pages;
3009  * but 0 when invalidating pagecache, don't throw away private data.
3010  */
3011 void unmap_mapping_range(struct address_space *mapping,
3012                 loff_t const holebegin, loff_t const holelen, int even_cows)
3013 {
3014         struct zap_details details;
3015         pgoff_t hba = holebegin >> PAGE_SHIFT;
3016         pgoff_t hlen = (holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
3017 
3018         /* Check for overflow. */
3019         if (sizeof(holelen) > sizeof(hlen)) {
3020                 long long holeend =
3021                         (holebegin + holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
3022                 if (holeend & ~(long long)ULONG_MAX)
3023                         hlen = ULONG_MAX - hba + 1;
3024         }
3025 
3026         details.check_mapping = even_cows? NULL: mapping;
3027         details.nonlinear_vma = NULL;
3028         details.first_index = hba;
3029         details.last_index = hba + hlen - 1;
3030         if (details.last_index < details.first_index)
3031                 details.last_index = ULONG_MAX;
3032 
3033 
3034         mutex_lock(&mapping->i_mmap_mutex);
3035         if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap)))
3036                 unmap_mapping_range_tree(&mapping->i_mmap, &details);
3037         if (unlikely(!list_empty(&mapping->i_mmap_nonlinear)))
3038                 unmap_mapping_range_list(&mapping->i_mmap_nonlinear, &details);
3039         mutex_unlock(&mapping->i_mmap_mutex);
3040 }
3041 EXPORT_SYMBOL(unmap_mapping_range);
3042 
3043 /*
3044  * We enter with non-exclusive mmap_sem (to exclude vma changes,
3045  * but allow concurrent faults), and pte mapped but not yet locked.
3046  * We return with mmap_sem still held, but pte unmapped and unlocked.
3047  */
3048 static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
3049                 unsigned long address, pte_t *page_table, pmd_t *pmd,
3050                 unsigned int flags, pte_t orig_pte)
3051 {
3052         spinlock_t *ptl;
3053         struct page *page, *swapcache;
3054         swp_entry_t entry;
3055         pte_t pte;
3056         int locked;
3057         struct mem_cgroup *ptr;
3058         int exclusive = 0;
3059         int ret = 0;
3060 
3061         if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
3062                 goto out;
3063 
3064         entry = pte_to_swp_entry(orig_pte);
3065         if (unlikely(non_swap_entry(entry))) {
3066                 if (is_migration_entry(entry)) {
3067                         migration_entry_wait(mm, pmd, address);
3068                 } else if (is_hwpoison_entry(entry)) {
3069                         ret = VM_FAULT_HWPOISON;
3070                 } else {
3071                         print_bad_pte(vma, address, orig_pte, NULL);
3072                         ret = VM_FAULT_SIGBUS;
3073                 }
3074                 goto out;
3075         }
3076         delayacct_set_flag(DELAYACCT_PF_SWAPIN);
3077         page = lookup_swap_cache(entry);
3078         if (!page) {
3079                 page = swapin_readahead(entry,
3080                                         GFP_HIGHUSER_MOVABLE, vma, address);
3081                 if (!page) {
3082                         /*
3083                          * Back out if somebody else faulted in this pte
3084                          * while we released the pte lock.
3085                          */
3086                         page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
3087                         if (likely(pte_same(*page_table, orig_pte)))
3088                                 ret = VM_FAULT_OOM;
3089                         delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
3090                         goto unlock;
3091                 }
3092 
3093                 /* Had to read the page from swap area: Major fault */
3094                 ret = VM_FAULT_MAJOR;
3095                 count_vm_event(PGMAJFAULT);
3096                 mem_cgroup_count_vm_event(mm, PGMAJFAULT);
3097         } else if (PageHWPoison(page)) {
3098                 /*
3099                  * hwpoisoned dirty swapcache pages are kept for killing
3100                  * owner processes (which may be unknown at hwpoison time)
3101                  */
3102                 ret = VM_FAULT_HWPOISON;
3103                 delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
3104                 swapcache = page;
3105                 goto out_release;
3106         }
3107 
3108         swapcache = page;
3109         locked = lock_page_or_retry(page, mm, flags);
3110 
3111         delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
3112         if (!locked) {
3113                 ret |= VM_FAULT_RETRY;
3114                 goto out_release;
3115         }
3116 
3117         /*
3118          * Make sure try_to_free_swap or reuse_swap_page or swapoff did not
3119          * release the swapcache from under us.  The page pin, and pte_same
3120          * test below, are not enough to exclude that.  Even if it is still
3121          * swapcache, we need to check that the page's swap has not changed.
3122          */
3123         if (unlikely(!PageSwapCache(page) || page_private(page) != entry.val))
3124                 goto out_page;
3125 
3126         page = ksm_might_need_to_copy(page, vma, address);
3127         if (unlikely(!page)) {
3128                 ret = VM_FAULT_OOM;
3129                 page = swapcache;
3130                 goto out_page;
3131         }
3132 
3133         if (mem_cgroup_try_charge_swapin(mm, page, GFP_KERNEL, &ptr)) {
3134                 ret = VM_FAULT_OOM;
3135                 goto out_page;
3136         }
3137 
3138         /*
3139          * Back out if somebody else already faulted in this pte.
3140          */
3141         page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
3142         if (unlikely(!pte_same(*page_table, orig_pte)))
3143                 goto out_nomap;
3144 
3145         if (unlikely(!PageUptodate(page))) {
3146                 ret = VM_FAULT_SIGBUS;
3147                 goto out_nomap;
3148         }
3149 
3150         /*
3151          * The page isn't present yet, go ahead with the fault.
3152          *
3153          * Be careful about the sequence of operations here.
3154          * To get its accounting right, reuse_swap_page() must be called
3155          * while the page is counted on swap but not yet in mapcount i.e.
3156          * before page_add_anon_rmap() and swap_free(); try_to_free_swap()
3157          * must be called after the swap_free(), or it will never succeed.
3158          * Because delete_from_swap_page() may be called by reuse_swap_page(),
3159          * mem_cgroup_commit_charge_swapin() may not be able to find swp_entry
3160          * in page->private. In this case, a record in swap_cgroup  is silently
3161          * discarded at swap_free().
3162          */
3163 
3164         inc_mm_counter_fast(mm, MM_ANONPAGES);
3165         dec_mm_counter_fast(mm, MM_SWAPENTS);
3166         pte = mk_pte(page, vma->vm_page_prot);
3167         if ((flags & FAULT_FLAG_WRITE) && reuse_swap_page(page)) {
3168                 pte = maybe_mkwrite(pte_mkdirty(pte), vma);
3169                 flags &= ~FAULT_FLAG_WRITE;
3170                 ret |= VM_FAULT_WRITE;
3171                 exclusive = 1;
3172         }
3173         flush_icache_page(vma, page);
3174         if (pte_swp_soft_dirty(orig_pte))
3175                 pte = pte_mksoft_dirty(pte);
3176         set_pte_at(mm, address, page_table, pte);
3177         if (page == swapcache)
3178                 do_page_add_anon_rmap(page, vma, address, exclusive);
3179         else /* ksm created a completely new copy */
3180                 page_add_new_anon_rmap(page, vma, address);
3181         /* It's better to call commit-charge after rmap is established */
3182         mem_cgroup_commit_charge_swapin(page, ptr);
3183 
3184         swap_free(entry);
3185         if (vm_swap_full() || (vma->vm_flags & VM_LOCKED) || PageMlocked(page))
3186                 try_to_free_swap(page);
3187         unlock_page(page);
3188         if (page != swapcache) {
3189                 /*
3190                  * Hold the lock to avoid the swap entry to be reused
3191                  * until we take the PT lock for the pte_same() check
3192                  * (to avoid false positives from pte_same). For
3193                  * further safety release the lock after the swap_free
3194                  * so that the swap count won't change under a
3195                  * parallel locked swapcache.
3196                  */
3197                 unlock_page(swapcache);
3198                 page_cache_release(swapcache);
3199         }
3200 
3201         if (flags & FAULT_FLAG_WRITE) {
3202                 ret |= do_wp_page(mm, vma, address, page_table, pmd, ptl, pte);
3203                 if (ret & VM_FAULT_ERROR)
3204                         ret &= VM_FAULT_ERROR;
3205                 goto out;
3206         }
3207 
3208         /* No need to invalidate - it was non-present before */
3209         update_mmu_cache(vma, address, page_table);
3210 unlock:
3211         pte_unmap_unlock(page_table, ptl);
3212 out:
3213         return ret;
3214 out_nomap:
3215         mem_cgroup_cancel_charge_swapin(ptr);
3216         pte_unmap_unlock(page_table, ptl);
3217 out_page:
3218         unlock_page(page);
3219 out_release:
3220         page_cache_release(page);
3221         if (page != swapcache) {
3222                 unlock_page(swapcache);
3223                 page_cache_release(swapcache);
3224         }
3225         return ret;
3226 }
3227 
3228 /*
3229  * This is like a special single-page "expand_{down|up}wards()",
3230  * except we must first make sure that 'address{-|+}PAGE_SIZE'
3231  * doesn't hit another vma.
3232  */
3233 static inline int check_stack_guard_page(struct vm_area_struct *vma, unsigned long address)
3234 {
3235         address &= PAGE_MASK;
3236         if ((vma->vm_flags & VM_GROWSDOWN) && address == vma->vm_start) {
3237                 struct vm_area_struct *prev = vma->vm_prev;
3238 
3239                 /*
3240                  * Is there a mapping abutting this one below?
3241                  *
3242                  * That's only ok if it's the same stack mapping
3243                  * that has gotten split..
3244                  */
3245                 if (prev && prev->vm_end == address)
3246                         return prev->vm_flags & VM_GROWSDOWN ? 0 : -ENOMEM;
3247 
3248                 expand_downwards(vma, address - PAGE_SIZE);
3249         }
3250         if ((vma->vm_flags & VM_GROWSUP) && address + PAGE_SIZE == vma->vm_end) {
3251                 struct vm_area_struct *next = vma->vm_next;
3252 
3253                 /* As VM_GROWSDOWN but s/below/above/ */
3254                 if (next && next->vm_start == address + PAGE_SIZE)
3255                         return next->vm_flags & VM_GROWSUP ? 0 : -ENOMEM;
3256 
3257                 expand_upwards(vma, address + PAGE_SIZE);
3258         }
3259         return 0;
3260 }
3261 
3262 /*
3263  * We enter with non-exclusive mmap_sem (to exclude vma changes,
3264  * but allow concurrent faults), and pte mapped but not yet locked.
3265  * We return with mmap_sem still held, but pte unmapped and unlocked.
3266  */
3267 static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
3268                 unsigned long address, pte_t *page_table, pmd_t *pmd,
3269                 unsigned int flags)
3270 {
3271         struct page *page;
3272         spinlock_t *ptl;
3273         pte_t entry;
3274 
3275         pte_unmap(page_table);
3276 
3277         /* Check if we need to add a guard page to the stack */
3278         if (check_stack_guard_page(vma, address) < 0)
3279                 return VM_FAULT_SIGBUS;
3280 
3281         /* Use the zero-page for reads */
3282         if (!(flags & FAULT_FLAG_WRITE)) {
3283                 entry = pte_mkspecial(pfn_pte(my_zero_pfn(address),
3284                                                 vma->vm_page_prot));
3285                 page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
3286                 if (!pte_none(*page_table))
3287                         goto unlock;
3288                 goto setpte;
3289         }
3290 
3291         /* Allocate our own private page. */
3292         if (unlikely(anon_vma_prepare(vma)))
3293                 goto oom;
3294         page = alloc_zeroed_user_highpage_movable(vma, address);
3295         if (!page)
3296                 goto oom;
3297         /*
3298          * The memory barrier inside __SetPageUptodate makes sure that
3299          * preceeding stores to the page contents become visible before
3300          * the set_pte_at() write.
3301          */
3302         __SetPageUptodate(page);
3303 
3304         if (mem_cgroup_charge_anon(page, mm, GFP_KERNEL))
3305                 goto oom_free_page;
3306 
3307         entry = mk_pte(page, vma->vm_page_prot);
3308         if (vma->vm_flags & VM_WRITE)
3309                 entry = pte_mkwrite(pte_mkdirty(entry));
3310 
3311         page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
3312         if (!pte_none(*page_table))
3313                 goto release;
3314 
3315         inc_mm_counter_fast(mm, MM_ANONPAGES);
3316         page_add_new_anon_rmap(page, vma, address);
3317 setpte:
3318         set_pte_at(mm, address, page_table, entry);
3319 
3320         /* No need to invalidate - it was non-present before */
3321         update_mmu_cache(vma, address, page_table);
3322 unlock:
3323         pte_unmap_unlock(page_table, ptl);
3324         return 0;
3325 release:
3326         mem_cgroup_uncharge_page(page);
3327         page_cache_release(page);
3328         goto unlock;
3329 oom_free_page:
3330         page_cache_release(page);
3331 oom:
3332         return VM_FAULT_OOM;
3333 }
3334 
3335 static int __do_fault(struct vm_area_struct *vma, unsigned long address,
3336                 pgoff_t pgoff, unsigned int flags, struct page **page)
3337 {
3338         struct vm_fault vmf;
3339         int ret;
3340 
3341         vmf.virtual_address = (void __user *)(address & PAGE_MASK);
3342         vmf.pgoff = pgoff;
3343         vmf.flags = flags;
3344         vmf.page = NULL;
3345 
3346         ret = vma->vm_ops->fault(vma, &vmf);
3347         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
3348                 return ret;
3349 
3350         if (unlikely(PageHWPoison(vmf.page))) {
3351                 if (ret & VM_FAULT_LOCKED)
3352                         unlock_page(vmf.page);
3353                 page_cache_release(vmf.page);
3354                 return VM_FAULT_HWPOISON;
3355         }
3356 
3357         if (unlikely(!(ret & VM_FAULT_LOCKED)))
3358                 lock_page(vmf.page);
3359         else
3360                 VM_BUG_ON_PAGE(!PageLocked(vmf.page), vmf.page);
3361 
3362         *page = vmf.page;
3363         return ret;
3364 }
3365 
3366 /**
3367  * do_set_pte - setup new PTE entry for given page and add reverse page mapping.
3368  *
3369  * @vma: virtual memory area
3370  * @address: user virtual address
3371  * @page: page to map
3372  * @pte: pointer to target page table entry
3373  * @write: true, if new entry is writable
3374  * @anon: true, if it's anonymous page
3375  *
3376  * Caller must hold page table lock relevant for @pte.
3377  *
3378  * Target users are page handler itself and implementations of
3379  * vm_ops->map_pages.
3380  */
3381 void do_set_pte(struct vm_area_struct *vma, unsigned long address,
3382                 struct page *page, pte_t *pte, bool write, bool anon)
3383 {
3384         pte_t entry;
3385 
3386         flush_icache_page(vma, page);
3387         entry = mk_pte(page, vma->vm_page_prot);
3388         if (write)
3389                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
3390         else if (pte_file(*pte) && pte_file_soft_dirty(*pte))
3391                 pte_mksoft_dirty(entry);
3392         if (anon) {
3393                 inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
3394                 page_add_new_anon_rmap(page, vma, address);
3395         } else {
3396                 inc_mm_counter_fast(vma->vm_mm, MM_FILEPAGES);
3397                 page_add_file_rmap(page);
3398         }
3399         set_pte_at(vma->vm_mm, address, pte, entry);
3400 
3401         /* no need to invalidate: a not-present page won't be cached */
3402         update_mmu_cache(vma, address, pte);
3403 }
3404 
3405 #define FAULT_AROUND_ORDER 4
3406 
3407 #ifdef CONFIG_DEBUG_FS
3408 static unsigned int fault_around_order = FAULT_AROUND_ORDER;
3409 
3410 static int fault_around_order_get(void *data, u64 *val)
3411 {
3412         *val = fault_around_order;
3413         return 0;
3414 }
3415 
3416 static int fault_around_order_set(void *data, u64 val)
3417 {
3418         BUILD_BUG_ON((1UL << FAULT_AROUND_ORDER) > PTRS_PER_PTE);
3419         if (1UL << val > PTRS_PER_PTE)
3420                 return -EINVAL;
3421         fault_around_order = val;
3422         return 0;
3423 }
3424 DEFINE_SIMPLE_ATTRIBUTE(fault_around_order_fops,
3425                 fault_around_order_get, fault_around_order_set, "%llu\n");
3426 
3427 static int __init fault_around_debugfs(void)
3428 {
3429         void *ret;
3430 
3431         ret = debugfs_create_file("fault_around_order", 0644, NULL, NULL,
3432                         &fault_around_order_fops);
3433         if (!ret)
3434                 pr_warn("Failed to create fault_around_order in debugfs");
3435         return 0;
3436 }
3437 late_initcall(fault_around_debugfs);
3438 
3439 static inline unsigned long fault_around_pages(void)
3440 {
3441         return 1UL << fault_around_order;
3442 }
3443 
3444 static inline unsigned long fault_around_mask(void)
3445 {
3446         return ~((1UL << (PAGE_SHIFT + fault_around_order)) - 1);
3447 }
3448 #else
3449 static inline unsigned long fault_around_pages(void)
3450 {
3451         unsigned long nr_pages;
3452 
3453         nr_pages = 1UL << FAULT_AROUND_ORDER;
3454         BUILD_BUG_ON(nr_pages > PTRS_PER_PTE);
3455         return nr_pages;
3456 }
3457 
3458 static inline unsigned long fault_around_mask(void)
3459 {
3460         return ~((1UL << (PAGE_SHIFT + FAULT_AROUND_ORDER)) - 1);
3461 }
3462 #endif
3463 
3464 static void do_fault_around(struct vm_area_struct *vma, unsigned long address,
3465                 pte_t *pte, pgoff_t pgoff, unsigned int flags)
3466 {
3467         unsigned long start_addr;
3468         pgoff_t max_pgoff;
3469         struct vm_fault vmf;
3470         int off;
3471 
3472         start_addr = max(address & fault_around_mask(), vma->vm_start);
3473         off = ((address - start_addr) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
3474         pte -= off;
3475         pgoff -= off;
3476 
3477         /*
3478          *  max_pgoff is either end of page table or end of vma
3479          *  or fault_around_pages() from pgoff, depending what is neast.
3480          */
3481         max_pgoff = pgoff - ((start_addr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1)) +
3482                 PTRS_PER_PTE - 1;
3483         max_pgoff = min3(max_pgoff, vma_pages(vma) + vma->vm_pgoff - 1,
3484                         pgoff + fault_around_pages() - 1);
3485 
3486         /* Check if it makes any sense to call ->map_pages */
3487         while (!pte_none(*pte)) {
3488                 if (++pgoff > max_pgoff)
3489                         return;
3490                 start_addr += PAGE_SIZE;
3491                 if (start_addr >= vma->vm_end)
3492                         return;
3493                 pte++;
3494         }
3495 
3496         vmf.virtual_address = (void __user *) start_addr;
3497         vmf.pte = pte;
3498         vmf.pgoff = pgoff;
3499         vmf.max_pgoff = max_pgoff;
3500         vmf.flags = flags;
3501         vma->vm_ops->map_pages(vma, &vmf);
3502 }
3503 
3504 static int do_read_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3505                 unsigned long address, pmd_t *pmd,
3506                 pgoff_t pgoff, unsigned int flags, pte_t orig_pte)
3507 {
3508         struct page *fault_page;
3509         spinlock_t *ptl;
3510         pte_t *pte;
3511         int ret = 0;
3512 
3513         /*
3514          * Let's call ->map_pages() first and use ->fault() as fallback
3515          * if page by the offset is not ready to be mapped (cold cache or
3516          * something).
3517          */
3518         if (vma->vm_ops->map_pages) {
3519                 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
3520                 do_fault_around(vma, address, pte, pgoff, flags);
3521                 if (!pte_same(*pte, orig_pte))
3522                         goto unlock_out;
3523                 pte_unmap_unlock(pte, ptl);
3524         }
3525 
3526         ret = __do_fault(vma, address, pgoff, flags, &fault_page);
3527         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
3528                 return ret;
3529 
3530         pte = pte_offset_map_lock(mm, pmd, address, &ptl);
3531         if (unlikely(!pte_same(*pte, orig_pte))) {
3532                 pte_unmap_unlock(pte, ptl);
3533                 unlock_page(fault_page);
3534                 page_cache_release(fault_page);
3535                 return ret;
3536         }
3537         do_set_pte(vma, address, fault_page, pte, false, false);
3538         unlock_page(fault_page);
3539 unlock_out:
3540         pte_unmap_unlock(pte, ptl);
3541         return ret;
3542 }
3543 
3544 static int do_cow_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3545                 unsigned long address, pmd_t *pmd,
3546                 pgoff_t pgoff, unsigned int flags, pte_t orig_pte)
3547 {
3548         struct page *fault_page, *new_page;
3549         spinlock_t *ptl;
3550         pte_t *pte;
3551         int ret;
3552 
3553         if (unlikely(anon_vma_prepare(vma)))
3554                 return VM_FAULT_OOM;
3555 
3556         new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
3557         if (!new_page)
3558                 return VM_FAULT_OOM;
3559 
3560         if (mem_cgroup_charge_anon(new_page, mm, GFP_KERNEL)) {
3561                 page_cache_release(new_page);
3562                 return VM_FAULT_OOM;
3563         }
3564 
3565         ret = __do_fault(vma, address, pgoff, flags, &fault_page);
3566         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
3567                 goto uncharge_out;
3568 
3569         copy_user_highpage(new_page, fault_page, address, vma);
3570         __SetPageUptodate(new_page);
3571 
3572         pte = pte_offset_map_lock(mm, pmd, address, &ptl);
3573         if (unlikely(!pte_same(*pte, orig_pte))) {
3574                 pte_unmap_unlock(pte, ptl);
3575                 unlock_page(fault_page);
3576                 page_cache_release(fault_page);
3577                 goto uncharge_out;
3578         }
3579         do_set_pte(vma, address, new_page, pte, true, true);
3580         pte_unmap_unlock(pte, ptl);
3581         unlock_page(fault_page);
3582         page_cache_release(fault_page);
3583         return ret;
3584 uncharge_out:
3585         mem_cgroup_uncharge_page(new_page);
3586         page_cache_release(new_page);
3587         return ret;
3588 }
3589 
3590 static int do_shared_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3591                 unsigned long address, pmd_t *pmd,
3592                 pgoff_t pgoff, unsigned int flags, pte_t orig_pte)
3593 {
3594         struct page *fault_page;
3595         struct address_space *mapping;
3596         spinlock_t *ptl;
3597         pte_t *pte;
3598         int dirtied = 0;
3599         int ret, tmp;
3600 
3601         ret = __do_fault(vma, address, pgoff, flags, &fault_page);
3602         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
3603                 return ret;
3604 
3605         /*
3606          * Check if the backing address space wants to know that the page is
3607          * about to become writable
3608          */
3609         if (vma->vm_ops->page_mkwrite) {
3610                 unlock_page(fault_page);
3611                 tmp = do_page_mkwrite(vma, fault_page, address);
3612                 if (unlikely(!tmp ||
3613                                 (tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
3614                         page_cache_release(fault_page);
3615                         return tmp;
3616                 }
3617         }
3618 
3619         pte = pte_offset_map_lock(mm, pmd, address, &ptl);
3620         if (unlikely(!pte_same(*pte, orig_pte))) {
3621                 pte_unmap_unlock(pte, ptl);
3622                 unlock_page(fault_page);
3623                 page_cache_release(fault_page);
3624                 return ret;
3625         }
3626         do_set_pte(vma, address, fault_page, pte, true, false);
3627         pte_unmap_unlock(pte, ptl);
3628 
3629         if (set_page_dirty(fault_page))
3630                 dirtied = 1;
3631         mapping = fault_page->mapping;
3632         unlock_page(fault_page);
3633         if ((dirtied || vma->vm_ops->page_mkwrite) && mapping) {
3634                 /*
3635                  * Some device drivers do not set page.mapping but still
3636                  * dirty their pages
3637                  */
3638                 balance_dirty_pages_ratelimited(mapping);
3639         }
3640 
3641         /* file_update_time outside page_lock */
3642         if (vma->vm_file && !vma->vm_ops->page_mkwrite)
3643                 file_update_time(vma->vm_file);
3644 
3645         return ret;
3646 }
3647 
3648 static int do_linear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3649                 unsigned long address, pte_t *page_table, pmd_t *pmd,
3650                 unsigned int flags, pte_t orig_pte)
3651 {
3652         pgoff_t pgoff = (((address & PAGE_MASK)
3653                         - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
3654 
3655         pte_unmap(page_table);
3656         if (!(flags & FAULT_FLAG_WRITE))
3657                 return do_read_fault(mm, vma, address, pmd, pgoff, flags,
3658                                 orig_pte);
3659         if (!(vma->vm_flags & VM_SHARED))
3660                 return do_cow_fault(mm, vma, address, pmd, pgoff, flags,
3661                                 orig_pte);
3662         return do_shared_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
3663 }
3664 
3665 /*
3666  * Fault of a previously existing named mapping. Repopulate the pte
3667  * from the encoded file_pte if possible. This enables swappable
3668  * nonlinear vmas.
3669  *
3670  * We enter with non-exclusive mmap_sem (to exclude vma changes,
3671  * but allow concurrent faults), and pte mapped but not yet locked.
3672  * We return with mmap_sem still held, but pte unmapped and unlocked.
3673  */
3674 static int do_nonlinear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3675                 unsigned long address, pte_t *page_table, pmd_t *pmd,
3676                 unsigned int flags, pte_t orig_pte)
3677 {
3678         pgoff_t pgoff;
3679 
3680         flags |= FAULT_FLAG_NONLINEAR;
3681 
3682         if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
3683                 return 0;
3684 
3685         if (unlikely(!(vma->vm_flags & VM_NONLINEAR))) {
3686                 /*
3687                  * Page table corrupted: show pte and kill process.
3688                  */
3689                 print_bad_pte(vma, address, orig_pte, NULL);
3690                 return VM_FAULT_SIGBUS;
3691         }
3692 
3693         pgoff = pte_to_pgoff(orig_pte);
3694         if (!(flags & FAULT_FLAG_WRITE))
3695                 return do_read_fault(mm, vma, address, pmd, pgoff, flags,
3696                                 orig_pte);
3697         if (!(vma->vm_flags & VM_SHARED))
3698                 return do_cow_fault(mm, vma, address, pmd, pgoff, flags,
3699                                 orig_pte);
3700         return do_shared_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
3701 }
3702 
3703 static int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,
3704                                 unsigned long addr, int page_nid,
3705                                 int *flags)
3706 {
3707         get_page(page);
3708 
3709         count_vm_numa_event(NUMA_HINT_FAULTS);
3710         if (page_nid == numa_node_id()) {
3711                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
3712                 *flags |= TNF_FAULT_LOCAL;
3713         }
3714 
3715         return mpol_misplaced(page, vma, addr);
3716 }
3717 
3718 static int do_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
3719                    unsigned long addr, pte_t pte, pte_t *ptep, pmd_t *pmd)
3720 {
3721         struct page *page = NULL;
3722         spinlock_t *ptl;
3723         int page_nid = -1;
3724         int last_cpupid;
3725         int target_nid;
3726         bool migrated = false;
3727         int flags = 0;
3728 
3729         /*
3730         * The "pte" at this point cannot be used safely without
3731         * validation through pte_unmap_same(). It's of NUMA type but
3732         * the pfn may be screwed if the read is non atomic.
3733         *
3734         * ptep_modify_prot_start is not called as this is clearing
3735         * the _PAGE_NUMA bit and it is not really expected that there
3736         * would be concurrent hardware modifications to the PTE.
3737         */
3738         ptl = pte_lockptr(mm, pmd);
3739         spin_lock(ptl);
3740         if (unlikely(!pte_same(*ptep, pte))) {
3741                 pte_unmap_unlock(ptep, ptl);
3742                 goto out;
3743         }
3744 
3745         pte = pte_mknonnuma(pte);
3746         set_pte_at(mm, addr, ptep, pte);
3747         update_mmu_cache(vma, addr, ptep);
3748 
3749         page = vm_normal_page(vma, addr, pte);
3750         if (!page) {
3751                 pte_unmap_unlock(ptep, ptl);
3752                 return 0;
3753         }
3754         BUG_ON(is_zero_pfn(page_to_pfn(page)));
3755 
3756         /*
3757          * Avoid grouping on DSO/COW pages in specific and RO pages
3758          * in general, RO pages shouldn't hurt as much anyway since
3759          * they can be in shared cache state.
3760          */
3761         if (!pte_write(pte))
3762                 flags |= TNF_NO_GROUP;
3763 
3764         /*
3765          * Flag if the page is shared between multiple address spaces. This
3766          * is later used when determining whether to group tasks together
3767          */
3768         if (page_mapcount(page) > 1 && (vma->vm_flags & VM_SHARED))
3769                 flags |= TNF_SHARED;
3770 
3771         last_cpupid = page_cpupid_last(page);
3772         page_nid = page_to_nid(page);
3773         target_nid = numa_migrate_prep(page, vma, addr, page_nid, &flags);
3774         pte_unmap_unlock(ptep, ptl);
3775         if (target_nid == -1) {
3776                 put_page(page);
3777                 goto out;
3778         }
3779 
3780         /* Migrate to the requested node */
3781         migrated = migrate_misplaced_page(page, vma, target_nid);
3782         if (migrated) {
3783                 page_nid = target_nid;
3784                 flags |= TNF_MIGRATED;
3785         }
3786 
3787 out:
3788         if (page_nid != -1)
3789                 task_numa_fault(last_cpupid, page_nid, 1, flags);
3790         return 0;
3791 }
3792 
3793 /*
3794  * These routines also need to handle stuff like marking pages dirty
3795  * and/or accessed for architectures that don't do it in hardware (most
3796  * RISC architectures).  The early dirtying is also good on the i386.
3797  *
3798  * There is also a hook called "update_mmu_cache()" that architectures
3799  * with external mmu caches can use to update those (ie the Sparc or
3800  * PowerPC hashed page tables that act as extended TLBs).
3801  *
3802  * We enter with non-exclusive mmap_sem (to exclude vma changes,
3803  * but allow concurrent faults), and pte mapped but not yet locked.
3804  * We return with mmap_sem still held, but pte unmapped and unlocked.
3805  */
3806 static int handle_pte_fault(struct mm_struct *mm,
3807                      struct vm_area_struct *vma, unsigned long address,
3808                      pte_t *pte, pmd_t *pmd, unsigned int flags)
3809 {
3810         pte_t entry;
3811         spinlock_t *ptl;
3812 
3813         entry = *pte;
3814         if (!pte_present(entry)) {
3815                 if (pte_none(entry)) {
3816                         if (vma->vm_ops) {
3817                                 if (likely(vma->vm_ops->fault))
3818                                         return do_linear_fault(mm, vma, address,
3819                                                 pte, pmd, flags, entry);
3820                         }
3821                         return do_anonymous_page(mm, vma, address,
3822                                                  pte, pmd, flags);
3823                 }
3824                 if (pte_file(entry))
3825                         return do_nonlinear_fault(mm, vma, address,
3826                                         pte, pmd, flags, entry);
3827                 return do_swap_page(mm, vma, address,
3828                                         pte, pmd, flags, entry);
3829         }
3830 
3831         if (pte_numa(entry))
3832                 return do_numa_page(mm, vma, address, entry, pte, pmd);
3833 
3834         ptl = pte_lockptr(mm, pmd);
3835         spin_lock(ptl);
3836         if (unlikely(!pte_same(*pte, entry)))
3837                 goto unlock;
3838         if (flags & FAULT_FLAG_WRITE) {
3839                 if (!pte_write(entry))
3840                         return do_wp_page(mm, vma, address,
3841                                         pte, pmd, ptl, entry);
3842                 entry = pte_mkdirty(entry);
3843         }
3844         entry = pte_mkyoung(entry);
3845         if (ptep_set_access_flags(vma, address, pte, entry, flags & FAULT_FLAG_WRITE)) {
3846                 update_mmu_cache(vma, address, pte);
3847         } else {
3848                 /*
3849                  * This is needed only for protection faults but the arch code
3850                  * is not yet telling us if this is a protection fault or not.
3851                  * This still avoids useless tlb flushes for .text page faults
3852                  * with threads.
3853                  */
3854                 if (flags & FAULT_FLAG_WRITE)
3855                         flush_tlb_fix_spurious_fault(vma, address);
3856         }
3857 unlock:
3858         pte_unmap_unlock(pte, ptl);
3859         return 0;
3860 }
3861 
3862 /*
3863  * By the time we get here, we already hold the mm semaphore
3864  */
3865 static int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3866                              unsigned long address, unsigned int flags)
3867 {
3868         pgd_t *pgd;
3869         pud_t *pud;
3870         pmd_t *pmd;
3871         pte_t *pte;
3872 
3873         if (unlikely(is_vm_hugetlb_page(vma)))
3874                 return hugetlb_fault(mm, vma, address, flags);
3875 
3876         pgd = pgd_offset(mm, address);
3877         pud = pud_alloc(mm, pgd, address);
3878         if (!pud)
3879                 return VM_FAULT_OOM;
3880         pmd = pmd_alloc(mm, pud, address);
3881         if (!pmd)
3882                 return VM_FAULT_OOM;
3883         if (pmd_none(*pmd) && transparent_hugepage_enabled(vma)) {
3884                 int ret = VM_FAULT_FALLBACK;
3885                 if (!vma->vm_ops)
3886                         ret = do_huge_pmd_anonymous_page(mm, vma, address,
3887                                         pmd, flags);
3888                 if (!(ret & VM_FAULT_FALLBACK))
3889                         return ret;
3890         } else {
3891                 pmd_t orig_pmd = *pmd;
3892                 int ret;
3893 
3894                 barrier();
3895                 if (pmd_trans_huge(orig_pmd)) {
3896                         unsigned int dirty = flags & FAULT_FLAG_WRITE;
3897 
3898                         /*
3899                          * If the pmd is splitting, return and retry the
3900                          * the fault.  Alternative: wait until the split
3901                          * is done, and goto retry.
3902                          */
3903                         if (pmd_trans_splitting(orig_pmd))
3904                                 return 0;
3905 
3906                         if (pmd_numa(orig_pmd))
3907                                 return do_huge_pmd_numa_page(mm, vma, address,
3908                                                              orig_pmd, pmd);
3909 
3910                         if (dirty && !pmd_write(orig_pmd)) {
3911                                 ret = do_huge_pmd_wp_page(mm, vma, address, pmd,
3912                                                           orig_pmd);
3913                                 if (!(ret & VM_FAULT_FALLBACK))
3914                                         return ret;
3915                         } else {
3916                                 huge_pmd_set_accessed(mm, vma, address, pmd,
3917                                                       orig_pmd, dirty);
3918                                 return 0;
3919                         }
3920                 }
3921         }
3922 
3923         /* THP should already have been handled */
3924         BUG_ON(pmd_numa(*pmd));
3925 
3926         /*
3927          * Use __pte_alloc instead of pte_alloc_map, because we can't
3928          * run pte_offset_map on the pmd, if an huge pmd could
3929          * materialize from under us from a different thread.
3930          */
3931         if (unlikely(pmd_none(*pmd)) &&
3932             unlikely(__pte_alloc(mm, vma, pmd, address)))
3933                 return VM_FAULT_OOM;
3934         /* if an huge pmd materialized from under us just retry later */
3935         if (unlikely(pmd_trans_huge(*pmd)))
3936                 return 0;
3937         /*
3938          * A regular pmd is established and it can't morph into a huge pmd
3939          * from under us anymore at this point because we hold the mmap_sem
3940          * read mode and khugepaged takes it in write mode. So now it's
3941          * safe to run pte_offset_map().
3942          */
3943         pte = pte_offset_map(pmd, address);
3944 
3945         return handle_pte_fault(mm, vma, address, pte, pmd, flags);
3946 }
3947 
3948 int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3949                     unsigned long address, unsigned int flags)
3950 {
3951         int ret;
3952 
3953         __set_current_state(TASK_RUNNING);
3954 
3955         count_vm_event(PGFAULT);
3956         mem_cgroup_count_vm_event(mm, PGFAULT);
3957 
3958         /* do counter updates before entering really critical section. */
3959         check_sync_rss_stat(current);
3960 
3961         /*
3962          * Enable the memcg OOM handling for faults triggered in user
3963          * space.  Kernel faults are handled more gracefully.
3964          */
3965         if (flags & FAULT_FLAG_USER)
3966                 mem_cgroup_oom_enable();
3967 
3968         ret = __handle_mm_fault(mm, vma, address, flags);
3969 
3970         if (flags & FAULT_FLAG_USER) {
3971                 mem_cgroup_oom_disable();
3972                 /*
3973                  * The task may have entered a memcg OOM situation but
3974                  * if the allocation error was handled gracefully (no
3975                  * VM_FAULT_OOM), there is no need to kill anything.
3976                  * Just clean up the OOM state peacefully.
3977                  */
3978                 if (task_in_memcg_oom(current) && !(ret & VM_FAULT_OOM))
3979                         mem_cgroup_oom_synchronize(false);
3980         }
3981 
3982         return ret;
3983 }
3984 
3985 #ifndef __PAGETABLE_PUD_FOLDED
3986 /*
3987  * Allocate page upper directory.
3988  * We've already handled the fast-path in-line.
3989  */
3990 int __pud_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address)
3991 {
3992         pud_t *new = pud_alloc_one(mm, address);
3993         if (!new)
3994                 return -ENOMEM;
3995 
3996         smp_wmb(); /* See comment in __pte_alloc */
3997 
3998         spin_lock(&mm->page_table_lock);
3999         if (pgd_present(*pgd))          /* Another has populated it */
4000                 pud_free(mm, new);
4001         else
4002                 pgd_populate(mm, pgd, new);
4003         spin_unlock(&mm->page_table_lock);
4004         return 0;
4005 }
4006 #endif /* __PAGETABLE_PUD_FOLDED */
4007 
4008 #ifndef __PAGETABLE_PMD_FOLDED
4009 /*
4010  * Allocate page middle directory.
4011  * We've already handled the fast-path in-line.
4012  */
4013 int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address)
4014 {
4015         pmd_t *new = pmd_alloc_one(mm, address);
4016         if (!new)
4017                 return -ENOMEM;
4018 
4019         smp_wmb(); /* See comment in __pte_alloc */
4020 
4021         spin_lock(&mm->page_table_lock);
4022 #ifndef __ARCH_HAS_4LEVEL_HACK
4023         if (pud_present(*pud))          /* Another has populated it */
4024                 pmd_free(mm, new);
4025         else
4026                 pud_populate(mm, pud, new);
4027 #else
4028         if (pgd_present(*pud))          /* Another has populated it */
4029                 pmd_free(mm, new);
4030         else
4031                 pgd_populate(mm, pud, new);
4032 #endif /* __ARCH_HAS_4LEVEL_HACK */
4033         spin_unlock(&mm->page_table_lock);
4034         return 0;
4035 }
4036 #endif /* __PAGETABLE_PMD_FOLDED */
4037 
4038 #if !defined(__HAVE_ARCH_GATE_AREA)
4039 
4040 #if defined(AT_SYSINFO_EHDR)
4041 static struct vm_area_struct gate_vma;
4042 
4043 static int __init gate_vma_init(void)
4044 {
4045         gate_vma.vm_mm = NULL;
4046         gate_vma.vm_start = FIXADDR_USER_START;
4047         gate_vma.vm_end = FIXADDR_USER_END;
4048         gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
4049         gate_vma.vm_page_prot = __P101;
4050 
4051         return 0;
4052 }
4053 __initcall(gate_vma_init);
4054 #endif
4055 
4056 struct vm_area_struct *get_gate_vma(struct mm_struct *mm)
4057 {
4058 #ifdef AT_SYSINFO_EHDR
4059         return &gate_vma;
4060 #else
4061         return NULL;
4062 #endif
4063 }
4064 
4065 int in_gate_area_no_mm(unsigned long addr)
4066 {
4067 #ifdef AT_SYSINFO_EHDR
4068         if ((addr >= FIXADDR_USER_START) && (addr < FIXADDR_USER_END))
4069                 return 1;
4070 #endif
4071         return 0;
4072 }
4073 
4074 #endif  /* __HAVE_ARCH_GATE_AREA */
4075 
4076 static int __follow_pte(struct mm_struct *mm, unsigned long address,
4077                 pte_t **ptepp, spinlock_t **ptlp)
4078 {
4079         pgd_t *pgd;
4080         pud_t *pud;
4081         pmd_t *pmd;
4082         pte_t *ptep;
4083 
4084         pgd = pgd_offset(mm, address);
4085         if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
4086                 goto out;
4087 
4088         pud = pud_offset(pgd, address);
4089         if (pud_none(*pud) || unlikely(pud_bad(*pud)))
4090                 goto out;
4091 
4092         pmd = pmd_offset(pud, address);
4093         VM_BUG_ON(pmd_trans_huge(*pmd));
4094         if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
4095                 goto out;
4096 
4097         /* We cannot handle huge page PFN maps. Luckily they don't exist. */
4098         if (pmd_huge(*pmd))
4099                 goto out;
4100 
4101         ptep = pte_offset_map_lock(mm, pmd, address, ptlp);
4102         if (!ptep)
4103                 goto out;
4104         if (!pte_present(*ptep))
4105                 goto unlock;
4106         *ptepp = ptep;
4107         return 0;
4108 unlock:
4109         pte_unmap_unlock(ptep, *ptlp);
4110 out:
4111         return -EINVAL;
4112 }
4113 
4114 static inline int follow_pte(struct mm_struct *mm, unsigned long address,
4115                              pte_t **ptepp, spinlock_t **ptlp)
4116 {
4117         int res;
4118 
4119         /* (void) is needed to make gcc happy */
4120         (void) __cond_lock(*ptlp,
4121                            !(res = __follow_pte(mm, address, ptepp, ptlp)));
4122         return res;
4123 }
4124 
4125 /**
4126  * follow_pfn - look up PFN at a user virtual address
4127  * @vma: memory mapping
4128  * @address: user virtual address
4129  * @pfn: location to store found PFN
4130  *
4131  * Only IO mappings and raw PFN mappings are allowed.
4132  *
4133  * Returns zero and the pfn at @pfn on success, -ve otherwise.
4134  */
4135 int follow_pfn(struct vm_area_struct *vma, unsigned long address,
4136         unsigned long *pfn)
4137 {
4138         int ret = -EINVAL;
4139         spinlock_t *ptl;
4140         pte_t *ptep;
4141 
4142         if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
4143                 return ret;
4144 
4145         ret = follow_pte(vma->vm_mm, address, &ptep, &ptl);
4146         if (ret)
4147                 return ret;
4148         *pfn = pte_pfn(*ptep);
4149         pte_unmap_unlock(ptep, ptl);
4150         return 0;
4151 }
4152 EXPORT_SYMBOL(follow_pfn);
4153 
4154 #ifdef CONFIG_HAVE_IOREMAP_PROT
4155 int follow_phys(struct vm_area_struct *vma,
4156                 unsigned long address, unsigned int flags,
4157                 unsigned long *prot, resource_size_t *phys)
4158 {
4159         int ret = -EINVAL;
4160         pte_t *ptep, pte;
4161         spinlock_t *ptl;
4162 
4163         if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
4164                 goto out;
4165 
4166         if (follow_pte(vma->vm_mm, address, &ptep, &ptl))
4167                 goto out;
4168         pte = *ptep;
4169 
4170         if ((flags & FOLL_WRITE) && !pte_write(pte))
4171                 goto unlock;
4172 
4173         *prot = pgprot_val(pte_pgprot(pte));
4174         *phys = (resource_size_t)pte_pfn(pte) << PAGE_SHIFT;
4175 
4176         ret = 0;
4177 unlock:
4178         pte_unmap_unlock(ptep, ptl);
4179 out:
4180         return ret;
4181 }
4182 
4183 int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
4184                         void *buf, int len, int write)
4185 {
4186         resource_size_t phys_addr;
4187         unsigned long prot = 0;
4188         void __iomem *maddr;
4189         int offset = addr & (PAGE_SIZE-1);
4190 
4191         if (follow_phys(vma, addr, write, &prot, &phys_addr))
4192                 return -EINVAL;
4193 
4194         maddr = ioremap_prot(phys_addr, PAGE_SIZE, prot);
4195         if (write)
4196                 memcpy_toio(maddr + offset, buf, len);
4197         else
4198                 memcpy_fromio(buf, maddr + offset, len);
4199         iounmap(maddr);
4200 
4201         return len;
4202 }
4203 EXPORT_SYMBOL_GPL(generic_access_phys);
4204 #endif
4205 
4206 /*
4207  * Access another process' address space as given in mm.  If non-NULL, use the
4208  * given task for page fault accounting.
4209  */
4210 static int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
4211                 unsigned long addr, void *buf, int len, int write)
4212 {
4213         struct vm_area_struct *vma;
4214         void *old_buf = buf;
4215 
4216         down_read(&mm->mmap_sem);
4217         /* ignore errors, just check how much was successfully transferred */
4218         while (len) {
4219                 int bytes, ret, offset;
4220                 void *maddr;
4221                 struct page *page = NULL;
4222 
4223                 ret = get_user_pages(tsk, mm, addr, 1,
4224                                 write, 1, &page, &vma);
4225                 if (ret <= 0) {
4226                         /*
4227                          * Check if this is a VM_IO | VM_PFNMAP VMA, which
4228                          * we can access using slightly different code.
4229                          */
4230 #ifdef CONFIG_HAVE_IOREMAP_PROT
4231                         vma = find_vma(mm, addr);
4232                         if (!vma || vma->vm_start > addr)
4233                                 break;
4234                         if (vma->vm_ops && vma->vm_ops->access)
4235                                 ret = vma->vm_ops->access(vma, addr, buf,
4236                                                           len, write);
4237                         if (ret <= 0)
4238 #endif
4239                                 break;
4240                         bytes = ret;
4241                 } else {
4242                         bytes = len;
4243                         offset = addr & (PAGE_SIZE-1);
4244                         if (bytes > PAGE_SIZE-offset)
4245                                 bytes = PAGE_SIZE-offset;
4246 
4247                         maddr = kmap(page);
4248                         if (write) {
4249                                 copy_to_user_page(vma, page, addr,
4250                                                   maddr + offset, buf, bytes);
4251                                 set_page_dirty_lock(page);
4252                         } else {
4253                                 copy_from_user_page(vma, page, addr,
4254                                                     buf, maddr + offset, bytes);
4255                         }
4256                         kunmap(page);
4257                         page_cache_release(page);
4258                 }
4259                 len -= bytes;
4260                 buf += bytes;
4261                 addr += bytes;
4262         }
4263         up_read(&mm->mmap_sem);
4264 
4265         return buf - old_buf;
4266 }
4267 
4268 /**
4269  * access_remote_vm - access another process' address space
4270  * @mm:         the mm_struct of the target address space
4271  * @addr:       start address to access
4272  * @buf:        source or destination buffer
4273  * @len:        number of bytes to transfer
4274  * @write:      whether the access is a write
4275  *
4276  * The caller must hold a reference on @mm.
4277  */
4278 int access_remote_vm(struct mm_struct *mm, unsigned long addr,
4279                 void *buf, int len, int write)
4280 {
4281         return __access_remote_vm(NULL, mm, addr, buf, len, write);
4282 }
4283 
4284 /*
4285  * Access another process' address space.
4286  * Source/target buffer must be kernel space,
4287  * Do not walk the page table directly, use get_user_pages
4288  */
4289 int access_process_vm(struct task_struct *tsk, unsigned long addr,
4290                 void *buf, int len, int write)
4291 {
4292         struct mm_struct *mm;
4293         int ret;
4294 
4295         mm = get_task_mm(tsk);
4296         if (!mm)
4297                 return 0;
4298 
4299         ret = __access_remote_vm(tsk, mm, addr, buf, len, write);
4300         mmput(mm);
4301 
4302         return ret;
4303 }
4304 
4305 /*
4306  * Print the name of a VMA.
4307  */
4308 void print_vma_addr(char *prefix, unsigned long ip)
4309 {
4310         struct mm_struct *mm = current->mm;
4311         struct vm_area_struct *vma;
4312 
4313         /*
4314          * Do not print if we are in atomic
4315          * contexts (in exception stacks, etc.):
4316          */
4317         if (preempt_count())
4318                 return;
4319 
4320         down_read(&mm->mmap_sem);
4321         vma = find_vma(mm, ip);
4322         if (vma && vma->vm_file) {
4323                 struct file *f = vma->vm_file;
4324                 char *buf = (char *)__get_free_page(GFP_KERNEL);
4325                 if (buf) {
4326                         char *p;
4327 
4328                         p = d_path(&f->f_path, buf, PAGE_SIZE);
4329                         if (IS_ERR(p))
4330                                 p = "?";
4331                         printk("%s%s[%lx+%lx]", prefix, kbasename(p),
4332                                         vma->vm_start,
4333                                         vma->vm_end - vma->vm_start);
4334                         free_page((unsigned long)buf);
4335                 }
4336         }
4337         up_read(&mm->mmap_sem);
4338 }
4339 
4340 #if defined(CONFIG_PROVE_LOCKING) || defined(CONFIG_DEBUG_ATOMIC_SLEEP)
4341 void might_fault(void)
4342 {
4343         /*
4344          * Some code (nfs/sunrpc) uses socket ops on kernel memory while
4345          * holding the mmap_sem, this is safe because kernel memory doesn't
4346          * get paged out, therefore we'll never actually fault, and the
4347          * below annotations will generate false positives.
4348          */
4349         if (segment_eq(get_fs(), KERNEL_DS))
4350                 return;
4351 
4352         /*
4353          * it would be nicer only to annotate paths which are not under
4354          * pagefault_disable, however that requires a larger audit and
4355          * providing helpers like get_user_atomic.
4356          */
4357         if (in_atomic())
4358                 return;
4359 
4360         __might_sleep(__FILE__, __LINE__, 0);
4361 
4362         if (current->mm)
4363                 might_lock_read(&current->mm->mmap_sem);
4364 }
4365 EXPORT_SYMBOL(might_fault);
4366 #endif
4367 
4368 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HUGETLBFS)
4369 static void clear_gigantic_page(struct page *page,
4370                                 unsigned long addr,
4371                                 unsigned int pages_per_huge_page)
4372 {
4373         int i;
4374         struct page *p = page;
4375 
4376         might_sleep();
4377         for (i = 0; i < pages_per_huge_page;
4378              i++, p = mem_map_next(p, page, i)) {
4379                 cond_resched();
4380                 clear_user_highpage(p, addr + i * PAGE_SIZE);
4381         }
4382 }
4383 void clear_huge_page(struct page *page,
4384                      unsigned long addr, unsigned int pages_per_huge_page)
4385 {
4386         int i;
4387 
4388         if (unlikely(pages_per_huge_page > MAX_ORDER_NR_PAGES)) {
4389                 clear_gigantic_page(page, addr, pages_per_huge_page);
4390                 return;
4391         }
4392 
4393         might_sleep();
4394         for (i = 0; i < pages_per_huge_page; i++) {
4395                 cond_resched();
4396                 clear_user_highpage(page + i, addr + i * PAGE_SIZE);
4397         }
4398 }
4399 
4400 static void copy_user_gigantic_page(struct page *dst, struct page *src,
4401                                     unsigned long addr,
4402                                     struct vm_area_struct *vma,
4403                                     unsigned int pages_per_huge_page)
4404 {
4405         int i;
4406         struct page *dst_base = dst;
4407         struct page *src_base = src;
4408 
4409         for (i = 0; i < pages_per_huge_page; ) {
4410                 cond_resched();
4411                 copy_user_highpage(dst, src, addr + i*PAGE_SIZE, vma);
4412 
4413                 i++;
4414                 dst = mem_map_next(dst, dst_base, i);
4415                 src = mem_map_next(src, src_base, i);
4416         }
4417 }
4418 
4419 void copy_user_huge_page(struct page *dst, struct page *src,
4420                          unsigned long addr, struct vm_area_struct *vma,
4421                          unsigned int pages_per_huge_page)
4422 {
4423         int i;
4424 
4425         if (unlikely(pages_per_huge_page > MAX_ORDER_NR_PAGES)) {
4426                 copy_user_gigantic_page(dst, src, addr, vma,
4427                                         pages_per_huge_page);
4428                 return;
4429         }
4430 
4431         might_sleep();
4432         for (i = 0; i < pages_per_huge_page; i++) {
4433                 cond_resched();
4434                 copy_user_highpage(dst + i, src + i, addr + i*PAGE_SIZE, vma);
4435         }
4436 }
4437 #endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */
4438 
4439 #if USE_SPLIT_PTE_PTLOCKS && ALLOC_SPLIT_PTLOCKS
4440 
4441 static struct kmem_cache *page_ptl_cachep;
4442 
4443 void __init ptlock_cache_init(void)
4444 {
4445         page_ptl_cachep = kmem_cache_create("page->ptl", sizeof(spinlock_t), 0,
4446                         SLAB_PANIC, NULL);
4447 }
4448 
4449 bool ptlock_alloc(struct page *page)
4450 {
4451         spinlock_t *ptl;
4452 
4453         ptl = kmem_cache_alloc(page_ptl_cachep, GFP_KERNEL);
4454         if (!ptl)
4455                 return false;
4456         page->ptl = ptl;
4457         return true;
4458 }
4459 
4460 void ptlock_free(struct page *page)
4461 {
4462         kmem_cache_free(page_ptl_cachep, page->ptl);
4463 }
4464 #endif
4465 

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