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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 #include <linux/userfaultfd_k.h>
 65 
 66 #include <asm/io.h>
 67 #include <asm/pgalloc.h>
 68 #include <asm/uaccess.h>
 69 #include <asm/tlb.h>
 70 #include <asm/tlbflush.h>
 71 #include <asm/pgtable.h>
 72 
 73 #include "internal.h"
 74 
 75 #ifdef LAST_CPUPID_NOT_IN_PAGE_FLAGS
 76 #warning Unfortunate NUMA and NUMA Balancing config, growing page-frame for last_cpupid.
 77 #endif
 78 
 79 #ifndef CONFIG_NEED_MULTIPLE_NODES
 80 /* use the per-pgdat data instead for discontigmem - mbligh */
 81 unsigned long max_mapnr;
 82 struct page *mem_map;
 83 
 84 EXPORT_SYMBOL(max_mapnr);
 85 EXPORT_SYMBOL(mem_map);
 86 #endif
 87 
 88 /*
 89  * A number of key systems in x86 including ioremap() rely on the assumption
 90  * that high_memory defines the upper bound on direct map memory, then end
 91  * of ZONE_NORMAL.  Under CONFIG_DISCONTIG this means that max_low_pfn and
 92  * highstart_pfn must be the same; there must be no gap between ZONE_NORMAL
 93  * and ZONE_HIGHMEM.
 94  */
 95 void * high_memory;
 96 
 97 EXPORT_SYMBOL(high_memory);
 98 
 99 /*
100  * Randomize the address space (stacks, mmaps, brk, etc.).
101  *
102  * ( When CONFIG_COMPAT_BRK=y we exclude brk from randomization,
103  *   as ancient (libc5 based) binaries can segfault. )
104  */
105 int randomize_va_space __read_mostly =
106 #ifdef CONFIG_COMPAT_BRK
107                                         1;
108 #else
109                                         2;
110 #endif
111 
112 static int __init disable_randmaps(char *s)
113 {
114         randomize_va_space = 0;
115         return 1;
116 }
117 __setup("norandmaps", disable_randmaps);
118 
119 unsigned long zero_pfn __read_mostly;
120 unsigned long highest_memmap_pfn __read_mostly;
121 
122 EXPORT_SYMBOL(zero_pfn);
123 
124 /*
125  * CONFIG_MMU architectures set up ZERO_PAGE in their paging_init()
126  */
127 static int __init init_zero_pfn(void)
128 {
129         zero_pfn = page_to_pfn(ZERO_PAGE(0));
130         return 0;
131 }
132 core_initcall(init_zero_pfn);
133 
134 
135 #if defined(SPLIT_RSS_COUNTING)
136 
137 void sync_mm_rss(struct mm_struct *mm)
138 {
139         int i;
140 
141         for (i = 0; i < NR_MM_COUNTERS; i++) {
142                 if (current->rss_stat.count[i]) {
143                         add_mm_counter(mm, i, current->rss_stat.count[i]);
144                         current->rss_stat.count[i] = 0;
145                 }
146         }
147         current->rss_stat.events = 0;
148 }
149 
150 static void add_mm_counter_fast(struct mm_struct *mm, int member, int val)
151 {
152         struct task_struct *task = current;
153 
154         if (likely(task->mm == mm))
155                 task->rss_stat.count[member] += val;
156         else
157                 add_mm_counter(mm, member, val);
158 }
159 #define inc_mm_counter_fast(mm, member) add_mm_counter_fast(mm, member, 1)
160 #define dec_mm_counter_fast(mm, member) add_mm_counter_fast(mm, member, -1)
161 
162 /* sync counter once per 64 page faults */
163 #define TASK_RSS_EVENTS_THRESH  (64)
164 static void check_sync_rss_stat(struct task_struct *task)
165 {
166         if (unlikely(task != current))
167                 return;
168         if (unlikely(task->rss_stat.events++ > TASK_RSS_EVENTS_THRESH))
169                 sync_mm_rss(task->mm);
170 }
171 #else /* SPLIT_RSS_COUNTING */
172 
173 #define inc_mm_counter_fast(mm, member) inc_mm_counter(mm, member)
174 #define dec_mm_counter_fast(mm, member) dec_mm_counter(mm, member)
175 
176 static void check_sync_rss_stat(struct task_struct *task)
177 {
178 }
179 
180 #endif /* SPLIT_RSS_COUNTING */
181 
182 #ifdef HAVE_GENERIC_MMU_GATHER
183 
184 static bool tlb_next_batch(struct mmu_gather *tlb)
185 {
186         struct mmu_gather_batch *batch;
187 
188         batch = tlb->active;
189         if (batch->next) {
190                 tlb->active = batch->next;
191                 return true;
192         }
193 
194         if (tlb->batch_count == MAX_GATHER_BATCH_COUNT)
195                 return false;
196 
197         batch = (void *)__get_free_pages(GFP_NOWAIT | __GFP_NOWARN, 0);
198         if (!batch)
199                 return false;
200 
201         tlb->batch_count++;
202         batch->next = NULL;
203         batch->nr   = 0;
204         batch->max  = MAX_GATHER_BATCH;
205 
206         tlb->active->next = batch;
207         tlb->active = batch;
208 
209         return true;
210 }
211 
212 /* tlb_gather_mmu
213  *      Called to initialize an (on-stack) mmu_gather structure for page-table
214  *      tear-down from @mm. The @fullmm argument is used when @mm is without
215  *      users and we're going to destroy the full address space (exit/execve).
216  */
217 void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, unsigned long start, unsigned long end)
218 {
219         tlb->mm = mm;
220 
221         /* Is it from 0 to ~0? */
222         tlb->fullmm     = !(start | (end+1));
223         tlb->need_flush_all = 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         __tlb_reset_range(tlb);
235 }
236 
237 static void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb)
238 {
239         if (!tlb->end)
240                 return;
241 
242         tlb_flush(tlb);
243         mmu_notifier_invalidate_range(tlb->mm, tlb->start, tlb->end);
244 #ifdef CONFIG_HAVE_RCU_TABLE_FREE
245         tlb_table_flush(tlb);
246 #endif
247         __tlb_reset_range(tlb);
248 }
249 
250 static void tlb_flush_mmu_free(struct mmu_gather *tlb)
251 {
252         struct mmu_gather_batch *batch;
253 
254         for (batch = &tlb->local; batch && batch->nr; batch = batch->next) {
255                 free_pages_and_swap_cache(batch->pages, batch->nr);
256                 batch->nr = 0;
257         }
258         tlb->active = &tlb->local;
259 }
260 
261 void tlb_flush_mmu(struct mmu_gather *tlb)
262 {
263         tlb_flush_mmu_tlbonly(tlb);
264         tlb_flush_mmu_free(tlb);
265 }
266 
267 /* tlb_finish_mmu
268  *      Called at the end of the shootdown operation to free up any resources
269  *      that were required.
270  */
271 void tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
272 {
273         struct mmu_gather_batch *batch, *next;
274 
275         tlb_flush_mmu(tlb);
276 
277         /* keep the page table cache within bounds */
278         check_pgt_cache();
279 
280         for (batch = tlb->local.next; batch; batch = next) {
281                 next = batch->next;
282                 free_pages((unsigned long)batch, 0);
283         }
284         tlb->local.next = NULL;
285 }
286 
287 /* __tlb_remove_page
288  *      Must perform the equivalent to __free_pte(pte_get_and_clear(ptep)), while
289  *      handling the additional races in SMP caused by other CPUs caching valid
290  *      mappings in their TLBs. Returns the number of free page slots left.
291  *      When out of page slots we must call tlb_flush_mmu().
292  */
293 int __tlb_remove_page(struct mmu_gather *tlb, struct page *page)
294 {
295         struct mmu_gather_batch *batch;
296 
297         VM_BUG_ON(!tlb->end);
298 
299         batch = tlb->active;
300         batch->pages[batch->nr++] = page;
301         if (batch->nr == batch->max) {
302                 if (!tlb_next_batch(tlb))
303                         return 0;
304                 batch = tlb->active;
305         }
306         VM_BUG_ON_PAGE(batch->nr > batch->max, page);
307 
308         return batch->max - batch->nr;
309 }
310 
311 #endif /* HAVE_GENERIC_MMU_GATHER */
312 
313 #ifdef CONFIG_HAVE_RCU_TABLE_FREE
314 
315 /*
316  * See the comment near struct mmu_table_batch.
317  */
318 
319 static void tlb_remove_table_smp_sync(void *arg)
320 {
321         /* Simply deliver the interrupt */
322 }
323 
324 static void tlb_remove_table_one(void *table)
325 {
326         /*
327          * This isn't an RCU grace period and hence the page-tables cannot be
328          * assumed to be actually RCU-freed.
329          *
330          * It is however sufficient for software page-table walkers that rely on
331          * IRQ disabling. See the comment near struct mmu_table_batch.
332          */
333         smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
334         __tlb_remove_table(table);
335 }
336 
337 static void tlb_remove_table_rcu(struct rcu_head *head)
338 {
339         struct mmu_table_batch *batch;
340         int i;
341 
342         batch = container_of(head, struct mmu_table_batch, rcu);
343 
344         for (i = 0; i < batch->nr; i++)
345                 __tlb_remove_table(batch->tables[i]);
346 
347         free_page((unsigned long)batch);
348 }
349 
350 void tlb_table_flush(struct mmu_gather *tlb)
351 {
352         struct mmu_table_batch **batch = &tlb->batch;
353 
354         if (*batch) {
355                 call_rcu_sched(&(*batch)->rcu, tlb_remove_table_rcu);
356                 *batch = NULL;
357         }
358 }
359 
360 void tlb_remove_table(struct mmu_gather *tlb, void *table)
361 {
362         struct mmu_table_batch **batch = &tlb->batch;
363 
364         /*
365          * When there's less then two users of this mm there cannot be a
366          * concurrent page-table walk.
367          */
368         if (atomic_read(&tlb->mm->mm_users) < 2) {
369                 __tlb_remove_table(table);
370                 return;
371         }
372 
373         if (*batch == NULL) {
374                 *batch = (struct mmu_table_batch *)__get_free_page(GFP_NOWAIT | __GFP_NOWARN);
375                 if (*batch == NULL) {
376                         tlb_remove_table_one(table);
377                         return;
378                 }
379                 (*batch)->nr = 0;
380         }
381         (*batch)->tables[(*batch)->nr++] = table;
382         if ((*batch)->nr == MAX_TABLE_BATCH)
383                 tlb_table_flush(tlb);
384 }
385 
386 #endif /* CONFIG_HAVE_RCU_TABLE_FREE */
387 
388 /*
389  * Note: this doesn't free the actual pages themselves. That
390  * has been handled earlier when unmapping all the memory regions.
391  */
392 static void free_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
393                            unsigned long addr)
394 {
395         pgtable_t token = pmd_pgtable(*pmd);
396         pmd_clear(pmd);
397         pte_free_tlb(tlb, token, addr);
398         atomic_long_dec(&tlb->mm->nr_ptes);
399 }
400 
401 static inline void free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
402                                 unsigned long addr, unsigned long end,
403                                 unsigned long floor, unsigned long ceiling)
404 {
405         pmd_t *pmd;
406         unsigned long next;
407         unsigned long start;
408 
409         start = addr;
410         pmd = pmd_offset(pud, addr);
411         do {
412                 next = pmd_addr_end(addr, end);
413                 if (pmd_none_or_clear_bad(pmd))
414                         continue;
415                 free_pte_range(tlb, pmd, addr);
416         } while (pmd++, addr = next, addr != end);
417 
418         start &= PUD_MASK;
419         if (start < floor)
420                 return;
421         if (ceiling) {
422                 ceiling &= PUD_MASK;
423                 if (!ceiling)
424                         return;
425         }
426         if (end - 1 > ceiling - 1)
427                 return;
428 
429         pmd = pmd_offset(pud, start);
430         pud_clear(pud);
431         pmd_free_tlb(tlb, pmd, start);
432         mm_dec_nr_pmds(tlb->mm);
433 }
434 
435 static inline void free_pud_range(struct mmu_gather *tlb, pgd_t *pgd,
436                                 unsigned long addr, unsigned long end,
437                                 unsigned long floor, unsigned long ceiling)
438 {
439         pud_t *pud;
440         unsigned long next;
441         unsigned long start;
442 
443         start = addr;
444         pud = pud_offset(pgd, addr);
445         do {
446                 next = pud_addr_end(addr, end);
447                 if (pud_none_or_clear_bad(pud))
448                         continue;
449                 free_pmd_range(tlb, pud, addr, next, floor, ceiling);
450         } while (pud++, addr = next, addr != end);
451 
452         start &= PGDIR_MASK;
453         if (start < floor)
454                 return;
455         if (ceiling) {
456                 ceiling &= PGDIR_MASK;
457                 if (!ceiling)
458                         return;
459         }
460         if (end - 1 > ceiling - 1)
461                 return;
462 
463         pud = pud_offset(pgd, start);
464         pgd_clear(pgd);
465         pud_free_tlb(tlb, pud, start);
466 }
467 
468 /*
469  * This function frees user-level page tables of a process.
470  */
471 void free_pgd_range(struct mmu_gather *tlb,
472                         unsigned long addr, unsigned long end,
473                         unsigned long floor, unsigned long ceiling)
474 {
475         pgd_t *pgd;
476         unsigned long next;
477 
478         /*
479          * The next few lines have given us lots of grief...
480          *
481          * Why are we testing PMD* at this top level?  Because often
482          * there will be no work to do at all, and we'd prefer not to
483          * go all the way down to the bottom just to discover that.
484          *
485          * Why all these "- 1"s?  Because 0 represents both the bottom
486          * of the address space and the top of it (using -1 for the
487          * top wouldn't help much: the masks would do the wrong thing).
488          * The rule is that addr 0 and floor 0 refer to the bottom of
489          * the address space, but end 0 and ceiling 0 refer to the top
490          * Comparisons need to use "end - 1" and "ceiling - 1" (though
491          * that end 0 case should be mythical).
492          *
493          * Wherever addr is brought up or ceiling brought down, we must
494          * be careful to reject "the opposite 0" before it confuses the
495          * subsequent tests.  But what about where end is brought down
496          * by PMD_SIZE below? no, end can't go down to 0 there.
497          *
498          * Whereas we round start (addr) and ceiling down, by different
499          * masks at different levels, in order to test whether a table
500          * now has no other vmas using it, so can be freed, we don't
501          * bother to round floor or end up - the tests don't need that.
502          */
503 
504         addr &= PMD_MASK;
505         if (addr < floor) {
506                 addr += PMD_SIZE;
507                 if (!addr)
508                         return;
509         }
510         if (ceiling) {
511                 ceiling &= PMD_MASK;
512                 if (!ceiling)
513                         return;
514         }
515         if (end - 1 > ceiling - 1)
516                 end -= PMD_SIZE;
517         if (addr > end - 1)
518                 return;
519 
520         pgd = pgd_offset(tlb->mm, addr);
521         do {
522                 next = pgd_addr_end(addr, end);
523                 if (pgd_none_or_clear_bad(pgd))
524                         continue;
525                 free_pud_range(tlb, pgd, addr, next, floor, ceiling);
526         } while (pgd++, addr = next, addr != end);
527 }
528 
529 void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *vma,
530                 unsigned long floor, unsigned long ceiling)
531 {
532         while (vma) {
533                 struct vm_area_struct *next = vma->vm_next;
534                 unsigned long addr = vma->vm_start;
535 
536                 /*
537                  * Hide vma from rmap and truncate_pagecache before freeing
538                  * pgtables
539                  */
540                 unlink_anon_vmas(vma);
541                 unlink_file_vma(vma);
542 
543                 if (is_vm_hugetlb_page(vma)) {
544                         hugetlb_free_pgd_range(tlb, addr, vma->vm_end,
545                                 floor, next? next->vm_start: ceiling);
546                 } else {
547                         /*
548                          * Optimization: gather nearby vmas into one call down
549                          */
550                         while (next && next->vm_start <= vma->vm_end + PMD_SIZE
551                                && !is_vm_hugetlb_page(next)) {
552                                 vma = next;
553                                 next = vma->vm_next;
554                                 unlink_anon_vmas(vma);
555                                 unlink_file_vma(vma);
556                         }
557                         free_pgd_range(tlb, addr, vma->vm_end,
558                                 floor, next? next->vm_start: ceiling);
559                 }
560                 vma = next;
561         }
562 }
563 
564 int __pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma,
565                 pmd_t *pmd, unsigned long address)
566 {
567         spinlock_t *ptl;
568         pgtable_t new = pte_alloc_one(mm, address);
569         int wait_split_huge_page;
570         if (!new)
571                 return -ENOMEM;
572 
573         /*
574          * Ensure all pte setup (eg. pte page lock and page clearing) are
575          * visible before the pte is made visible to other CPUs by being
576          * put into page tables.
577          *
578          * The other side of the story is the pointer chasing in the page
579          * table walking code (when walking the page table without locking;
580          * ie. most of the time). Fortunately, these data accesses consist
581          * of a chain of data-dependent loads, meaning most CPUs (alpha
582          * being the notable exception) will already guarantee loads are
583          * seen in-order. See the alpha page table accessors for the
584          * smp_read_barrier_depends() barriers in page table walking code.
585          */
586         smp_wmb(); /* Could be smp_wmb__xxx(before|after)_spin_lock */
587 
588         ptl = pmd_lock(mm, pmd);
589         wait_split_huge_page = 0;
590         if (likely(pmd_none(*pmd))) {   /* Has another populated it ? */
591                 atomic_long_inc(&mm->nr_ptes);
592                 pmd_populate(mm, pmd, new);
593                 new = NULL;
594         } else if (unlikely(pmd_trans_splitting(*pmd)))
595                 wait_split_huge_page = 1;
596         spin_unlock(ptl);
597         if (new)
598                 pte_free(mm, new);
599         if (wait_split_huge_page)
600                 wait_split_huge_page(vma->anon_vma, pmd);
601         return 0;
602 }
603 
604 int __pte_alloc_kernel(pmd_t *pmd, unsigned long address)
605 {
606         pte_t *new = pte_alloc_one_kernel(&init_mm, address);
607         if (!new)
608                 return -ENOMEM;
609 
610         smp_wmb(); /* See comment in __pte_alloc */
611 
612         spin_lock(&init_mm.page_table_lock);
613         if (likely(pmd_none(*pmd))) {   /* Has another populated it ? */
614                 pmd_populate_kernel(&init_mm, pmd, new);
615                 new = NULL;
616         } else
617                 VM_BUG_ON(pmd_trans_splitting(*pmd));
618         spin_unlock(&init_mm.page_table_lock);
619         if (new)
620                 pte_free_kernel(&init_mm, new);
621         return 0;
622 }
623 
624 static inline void init_rss_vec(int *rss)
625 {
626         memset(rss, 0, sizeof(int) * NR_MM_COUNTERS);
627 }
628 
629 static inline void add_mm_rss_vec(struct mm_struct *mm, int *rss)
630 {
631         int i;
632 
633         if (current->mm == mm)
634                 sync_mm_rss(mm);
635         for (i = 0; i < NR_MM_COUNTERS; i++)
636                 if (rss[i])
637                         add_mm_counter(mm, i, rss[i]);
638 }
639 
640 /*
641  * This function is called to print an error when a bad pte
642  * is found. For example, we might have a PFN-mapped pte in
643  * a region that doesn't allow it.
644  *
645  * The calling function must still handle the error.
646  */
647 static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
648                           pte_t pte, struct page *page)
649 {
650         pgd_t *pgd = pgd_offset(vma->vm_mm, addr);
651         pud_t *pud = pud_offset(pgd, addr);
652         pmd_t *pmd = pmd_offset(pud, addr);
653         struct address_space *mapping;
654         pgoff_t index;
655         static unsigned long resume;
656         static unsigned long nr_shown;
657         static unsigned long nr_unshown;
658 
659         /*
660          * Allow a burst of 60 reports, then keep quiet for that minute;
661          * or allow a steady drip of one report per second.
662          */
663         if (nr_shown == 60) {
664                 if (time_before(jiffies, resume)) {
665                         nr_unshown++;
666                         return;
667                 }
668                 if (nr_unshown) {
669                         printk(KERN_ALERT
670                                 "BUG: Bad page map: %lu messages suppressed\n",
671                                 nr_unshown);
672                         nr_unshown = 0;
673                 }
674                 nr_shown = 0;
675         }
676         if (nr_shown++ == 0)
677                 resume = jiffies + 60 * HZ;
678 
679         mapping = vma->vm_file ? vma->vm_file->f_mapping : NULL;
680         index = linear_page_index(vma, addr);
681 
682         printk(KERN_ALERT
683                 "BUG: Bad page map in process %s  pte:%08llx pmd:%08llx\n",
684                 current->comm,
685                 (long long)pte_val(pte), (long long)pmd_val(*pmd));
686         if (page)
687                 dump_page(page, "bad pte");
688         printk(KERN_ALERT
689                 "addr:%p vm_flags:%08lx anon_vma:%p mapping:%p index:%lx\n",
690                 (void *)addr, vma->vm_flags, vma->anon_vma, mapping, index);
691         /*
692          * Choose text because data symbols depend on CONFIG_KALLSYMS_ALL=y
693          */
694         pr_alert("file:%pD fault:%pf mmap:%pf readpage:%pf\n",
695                  vma->vm_file,
696                  vma->vm_ops ? vma->vm_ops->fault : NULL,
697                  vma->vm_file ? vma->vm_file->f_op->mmap : NULL,
698                  mapping ? mapping->a_ops->readpage : NULL);
699         dump_stack();
700         add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
701 }
702 
703 /*
704  * vm_normal_page -- This function gets the "struct page" associated with a pte.
705  *
706  * "Special" mappings do not wish to be associated with a "struct page" (either
707  * it doesn't exist, or it exists but they don't want to touch it). In this
708  * case, NULL is returned here. "Normal" mappings do have a struct page.
709  *
710  * There are 2 broad cases. Firstly, an architecture may define a pte_special()
711  * pte bit, in which case this function is trivial. Secondly, an architecture
712  * may not have a spare pte bit, which requires a more complicated scheme,
713  * described below.
714  *
715  * A raw VM_PFNMAP mapping (ie. one that is not COWed) is always considered a
716  * special mapping (even if there are underlying and valid "struct pages").
717  * COWed pages of a VM_PFNMAP are always normal.
718  *
719  * The way we recognize COWed pages within VM_PFNMAP mappings is through the
720  * rules set up by "remap_pfn_range()": the vma will have the VM_PFNMAP bit
721  * set, and the vm_pgoff will point to the first PFN mapped: thus every special
722  * mapping will always honor the rule
723  *
724  *      pfn_of_page == vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT)
725  *
726  * And for normal mappings this is false.
727  *
728  * This restricts such mappings to be a linear translation from virtual address
729  * to pfn. To get around this restriction, we allow arbitrary mappings so long
730  * as the vma is not a COW mapping; in that case, we know that all ptes are
731  * special (because none can have been COWed).
732  *
733  *
734  * In order to support COW of arbitrary special mappings, we have VM_MIXEDMAP.
735  *
736  * VM_MIXEDMAP mappings can likewise contain memory with or without "struct
737  * page" backing, however the difference is that _all_ pages with a struct
738  * page (that is, those where pfn_valid is true) are refcounted and considered
739  * normal pages by the VM. The disadvantage is that pages are refcounted
740  * (which can be slower and simply not an option for some PFNMAP users). The
741  * advantage is that we don't have to follow the strict linearity rule of
742  * PFNMAP mappings in order to support COWable mappings.
743  *
744  */
745 #ifdef __HAVE_ARCH_PTE_SPECIAL
746 # define HAVE_PTE_SPECIAL 1
747 #else
748 # define HAVE_PTE_SPECIAL 0
749 #endif
750 struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
751                                 pte_t pte)
752 {
753         unsigned long pfn = pte_pfn(pte);
754 
755         if (HAVE_PTE_SPECIAL) {
756                 if (likely(!pte_special(pte)))
757                         goto check_pfn;
758                 if (vma->vm_ops && vma->vm_ops->find_special_page)
759                         return vma->vm_ops->find_special_page(vma, addr);
760                 if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
761                         return NULL;
762                 if (!is_zero_pfn(pfn))
763                         print_bad_pte(vma, addr, pte, NULL);
764                 return NULL;
765         }
766 
767         /* !HAVE_PTE_SPECIAL case follows: */
768 
769         if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
770                 if (vma->vm_flags & VM_MIXEDMAP) {
771                         if (!pfn_valid(pfn))
772                                 return NULL;
773                         goto out;
774                 } else {
775                         unsigned long off;
776                         off = (addr - vma->vm_start) >> PAGE_SHIFT;
777                         if (pfn == vma->vm_pgoff + off)
778                                 return NULL;
779                         if (!is_cow_mapping(vma->vm_flags))
780                                 return NULL;
781                 }
782         }
783 
784         if (is_zero_pfn(pfn))
785                 return NULL;
786 check_pfn:
787         if (unlikely(pfn > highest_memmap_pfn)) {
788                 print_bad_pte(vma, addr, pte, NULL);
789                 return NULL;
790         }
791 
792         /*
793          * NOTE! We still have PageReserved() pages in the page tables.
794          * eg. VDSO mappings can cause them to exist.
795          */
796 out:
797         return pfn_to_page(pfn);
798 }
799 
800 /*
801  * copy one vm_area from one task to the other. Assumes the page tables
802  * already present in the new task to be cleared in the whole range
803  * covered by this vma.
804  */
805 
806 static inline unsigned long
807 copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
808                 pte_t *dst_pte, pte_t *src_pte, struct vm_area_struct *vma,
809                 unsigned long addr, int *rss)
810 {
811         unsigned long vm_flags = vma->vm_flags;
812         pte_t pte = *src_pte;
813         struct page *page;
814 
815         /* pte contains position in swap or file, so copy. */
816         if (unlikely(!pte_present(pte))) {
817                 swp_entry_t entry = pte_to_swp_entry(pte);
818 
819                 if (likely(!non_swap_entry(entry))) {
820                         if (swap_duplicate(entry) < 0)
821                                 return entry.val;
822 
823                         /* make sure dst_mm is on swapoff's mmlist. */
824                         if (unlikely(list_empty(&dst_mm->mmlist))) {
825                                 spin_lock(&mmlist_lock);
826                                 if (list_empty(&dst_mm->mmlist))
827                                         list_add(&dst_mm->mmlist,
828                                                         &src_mm->mmlist);
829                                 spin_unlock(&mmlist_lock);
830                         }
831                         rss[MM_SWAPENTS]++;
832                 } else if (is_migration_entry(entry)) {
833                         page = migration_entry_to_page(entry);
834 
835                         if (PageAnon(page))
836                                 rss[MM_ANONPAGES]++;
837                         else
838                                 rss[MM_FILEPAGES]++;
839 
840                         if (is_write_migration_entry(entry) &&
841                                         is_cow_mapping(vm_flags)) {
842                                 /*
843                                  * COW mappings require pages in both
844                                  * parent and child to be set to read.
845                                  */
846                                 make_migration_entry_read(&entry);
847                                 pte = swp_entry_to_pte(entry);
848                                 if (pte_swp_soft_dirty(*src_pte))
849                                         pte = pte_swp_mksoft_dirty(pte);
850                                 set_pte_at(src_mm, addr, src_pte, pte);
851                         }
852                 }
853                 goto out_set_pte;
854         }
855 
856         /*
857          * If it's a COW mapping, write protect it both
858          * in the parent and the child
859          */
860         if (is_cow_mapping(vm_flags)) {
861                 ptep_set_wrprotect(src_mm, addr, src_pte);
862                 pte = pte_wrprotect(pte);
863         }
864 
865         /*
866          * If it's a shared mapping, mark it clean in
867          * the child
868          */
869         if (vm_flags & VM_SHARED)
870                 pte = pte_mkclean(pte);
871         pte = pte_mkold(pte);
872 
873         page = vm_normal_page(vma, addr, pte);
874         if (page) {
875                 get_page(page);
876                 page_dup_rmap(page);
877                 if (PageAnon(page))
878                         rss[MM_ANONPAGES]++;
879                 else
880                         rss[MM_FILEPAGES]++;
881         }
882 
883 out_set_pte:
884         set_pte_at(dst_mm, addr, dst_pte, pte);
885         return 0;
886 }
887 
888 static int copy_pte_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
889                    pmd_t *dst_pmd, pmd_t *src_pmd, struct vm_area_struct *vma,
890                    unsigned long addr, unsigned long end)
891 {
892         pte_t *orig_src_pte, *orig_dst_pte;
893         pte_t *src_pte, *dst_pte;
894         spinlock_t *src_ptl, *dst_ptl;
895         int progress = 0;
896         int rss[NR_MM_COUNTERS];
897         swp_entry_t entry = (swp_entry_t){0};
898 
899 again:
900         init_rss_vec(rss);
901 
902         dst_pte = pte_alloc_map_lock(dst_mm, dst_pmd, addr, &dst_ptl);
903         if (!dst_pte)
904                 return -ENOMEM;
905         src_pte = pte_offset_map(src_pmd, addr);
906         src_ptl = pte_lockptr(src_mm, src_pmd);
907         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
908         orig_src_pte = src_pte;
909         orig_dst_pte = dst_pte;
910         arch_enter_lazy_mmu_mode();
911 
912         do {
913                 /*
914                  * We are holding two locks at this point - either of them
915                  * could generate latencies in another task on another CPU.
916                  */
917                 if (progress >= 32) {
918                         progress = 0;
919                         if (need_resched() ||
920                             spin_needbreak(src_ptl) || spin_needbreak(dst_ptl))
921                                 break;
922                 }
923                 if (pte_none(*src_pte)) {
924                         progress++;
925                         continue;
926                 }
927                 entry.val = copy_one_pte(dst_mm, src_mm, dst_pte, src_pte,
928                                                         vma, addr, rss);
929                 if (entry.val)
930                         break;
931                 progress += 8;
932         } while (dst_pte++, src_pte++, addr += PAGE_SIZE, addr != end);
933 
934         arch_leave_lazy_mmu_mode();
935         spin_unlock(src_ptl);
936         pte_unmap(orig_src_pte);
937         add_mm_rss_vec(dst_mm, rss);
938         pte_unmap_unlock(orig_dst_pte, dst_ptl);
939         cond_resched();
940 
941         if (entry.val) {
942                 if (add_swap_count_continuation(entry, GFP_KERNEL) < 0)
943                         return -ENOMEM;
944                 progress = 0;
945         }
946         if (addr != end)
947                 goto again;
948         return 0;
949 }
950 
951 static inline int copy_pmd_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
952                 pud_t *dst_pud, pud_t *src_pud, struct vm_area_struct *vma,
953                 unsigned long addr, unsigned long end)
954 {
955         pmd_t *src_pmd, *dst_pmd;
956         unsigned long next;
957 
958         dst_pmd = pmd_alloc(dst_mm, dst_pud, addr);
959         if (!dst_pmd)
960                 return -ENOMEM;
961         src_pmd = pmd_offset(src_pud, addr);
962         do {
963                 next = pmd_addr_end(addr, end);
964                 if (pmd_trans_huge(*src_pmd)) {
965                         int err;
966                         VM_BUG_ON(next-addr != HPAGE_PMD_SIZE);
967                         err = copy_huge_pmd(dst_mm, src_mm,
968                                             dst_pmd, src_pmd, addr, vma);
969                         if (err == -ENOMEM)
970                                 return -ENOMEM;
971                         if (!err)
972                                 continue;
973                         /* fall through */
974                 }
975                 if (pmd_none_or_clear_bad(src_pmd))
976                         continue;
977                 if (copy_pte_range(dst_mm, src_mm, dst_pmd, src_pmd,
978                                                 vma, addr, next))
979                         return -ENOMEM;
980         } while (dst_pmd++, src_pmd++, addr = next, addr != end);
981         return 0;
982 }
983 
984 static inline int copy_pud_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
985                 pgd_t *dst_pgd, pgd_t *src_pgd, struct vm_area_struct *vma,
986                 unsigned long addr, unsigned long end)
987 {
988         pud_t *src_pud, *dst_pud;
989         unsigned long next;
990 
991         dst_pud = pud_alloc(dst_mm, dst_pgd, addr);
992         if (!dst_pud)
993                 return -ENOMEM;
994         src_pud = pud_offset(src_pgd, addr);
995         do {
996                 next = pud_addr_end(addr, end);
997                 if (pud_none_or_clear_bad(src_pud))
998                         continue;
999                 if (copy_pmd_range(dst_mm, src_mm, dst_pud, src_pud,
1000                                                 vma, addr, next))
1001                         return -ENOMEM;
1002         } while (dst_pud++, src_pud++, addr = next, addr != end);
1003         return 0;
1004 }
1005 
1006 int copy_page_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1007                 struct vm_area_struct *vma)
1008 {
1009         pgd_t *src_pgd, *dst_pgd;
1010         unsigned long next;
1011         unsigned long addr = vma->vm_start;
1012         unsigned long end = vma->vm_end;
1013         unsigned long mmun_start;       /* For mmu_notifiers */
1014         unsigned long mmun_end;         /* For mmu_notifiers */
1015         bool is_cow;
1016         int ret;
1017 
1018         /*
1019          * Don't copy ptes where a page fault will fill them correctly.
1020          * Fork becomes much lighter when there are big shared or private
1021          * readonly mappings. The tradeoff is that copy_page_range is more
1022          * efficient than faulting.
1023          */
1024         if (!(vma->vm_flags & (VM_HUGETLB | VM_PFNMAP | VM_MIXEDMAP)) &&
1025                         !vma->anon_vma)
1026                 return 0;
1027 
1028         if (is_vm_hugetlb_page(vma))
1029                 return copy_hugetlb_page_range(dst_mm, src_mm, vma);
1030 
1031         if (unlikely(vma->vm_flags & VM_PFNMAP)) {
1032                 /*
1033                  * We do not free on error cases below as remove_vma
1034                  * gets called on error from higher level routine
1035                  */
1036                 ret = track_pfn_copy(vma);
1037                 if (ret)
1038                         return ret;
1039         }
1040 
1041         /*
1042          * We need to invalidate the secondary MMU mappings only when
1043          * there could be a permission downgrade on the ptes of the
1044          * parent mm. And a permission downgrade will only happen if
1045          * is_cow_mapping() returns true.
1046          */
1047         is_cow = is_cow_mapping(vma->vm_flags);
1048         mmun_start = addr;
1049         mmun_end   = end;
1050         if (is_cow)
1051                 mmu_notifier_invalidate_range_start(src_mm, mmun_start,
1052                                                     mmun_end);
1053 
1054         ret = 0;
1055         dst_pgd = pgd_offset(dst_mm, addr);
1056         src_pgd = pgd_offset(src_mm, addr);
1057         do {
1058                 next = pgd_addr_end(addr, end);
1059                 if (pgd_none_or_clear_bad(src_pgd))
1060                         continue;
1061                 if (unlikely(copy_pud_range(dst_mm, src_mm, dst_pgd, src_pgd,
1062                                             vma, addr, next))) {
1063                         ret = -ENOMEM;
1064                         break;
1065                 }
1066         } while (dst_pgd++, src_pgd++, addr = next, addr != end);
1067 
1068         if (is_cow)
1069                 mmu_notifier_invalidate_range_end(src_mm, mmun_start, mmun_end);
1070         return ret;
1071 }
1072 
1073 static unsigned long zap_pte_range(struct mmu_gather *tlb,
1074                                 struct vm_area_struct *vma, pmd_t *pmd,
1075                                 unsigned long addr, unsigned long end,
1076                                 struct zap_details *details)
1077 {
1078         struct mm_struct *mm = tlb->mm;
1079         int force_flush = 0;
1080         int rss[NR_MM_COUNTERS];
1081         spinlock_t *ptl;
1082         pte_t *start_pte;
1083         pte_t *pte;
1084         swp_entry_t entry;
1085 
1086 again:
1087         init_rss_vec(rss);
1088         start_pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
1089         pte = start_pte;
1090         arch_enter_lazy_mmu_mode();
1091         do {
1092                 pte_t ptent = *pte;
1093                 if (pte_none(ptent)) {
1094                         continue;
1095                 }
1096 
1097                 if (pte_present(ptent)) {
1098                         struct page *page;
1099 
1100                         page = vm_normal_page(vma, addr, ptent);
1101                         if (unlikely(details) && page) {
1102                                 /*
1103                                  * unmap_shared_mapping_pages() wants to
1104                                  * invalidate cache without truncating:
1105                                  * unmap shared but keep private pages.
1106                                  */
1107                                 if (details->check_mapping &&
1108                                     details->check_mapping != page->mapping)
1109                                         continue;
1110                         }
1111                         ptent = ptep_get_and_clear_full(mm, addr, pte,
1112                                                         tlb->fullmm);
1113                         tlb_remove_tlb_entry(tlb, pte, addr);
1114                         if (unlikely(!page))
1115                                 continue;
1116                         if (PageAnon(page))
1117                                 rss[MM_ANONPAGES]--;
1118                         else {
1119                                 if (pte_dirty(ptent)) {
1120                                         force_flush = 1;
1121                                         set_page_dirty(page);
1122                                 }
1123                                 if (pte_young(ptent) &&
1124                                     likely(!(vma->vm_flags & VM_SEQ_READ)))
1125                                         mark_page_accessed(page);
1126                                 rss[MM_FILEPAGES]--;
1127                         }
1128                         page_remove_rmap(page);
1129                         if (unlikely(page_mapcount(page) < 0))
1130                                 print_bad_pte(vma, addr, ptent, page);
1131                         if (unlikely(!__tlb_remove_page(tlb, page))) {
1132                                 force_flush = 1;
1133                                 addr += PAGE_SIZE;
1134                                 break;
1135                         }
1136                         continue;
1137                 }
1138                 /* If details->check_mapping, we leave swap entries. */
1139                 if (unlikely(details))
1140                         continue;
1141 
1142                 entry = pte_to_swp_entry(ptent);
1143                 if (!non_swap_entry(entry))
1144                         rss[MM_SWAPENTS]--;
1145                 else if (is_migration_entry(entry)) {
1146                         struct page *page;
1147 
1148                         page = migration_entry_to_page(entry);
1149 
1150                         if (PageAnon(page))
1151                                 rss[MM_ANONPAGES]--;
1152                         else
1153                                 rss[MM_FILEPAGES]--;
1154                 }
1155                 if (unlikely(!free_swap_and_cache(entry)))
1156                         print_bad_pte(vma, addr, ptent, NULL);
1157                 pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
1158         } while (pte++, addr += PAGE_SIZE, addr != end);
1159 
1160         add_mm_rss_vec(mm, rss);
1161         arch_leave_lazy_mmu_mode();
1162 
1163         /* Do the actual TLB flush before dropping ptl */
1164         if (force_flush)
1165                 tlb_flush_mmu_tlbonly(tlb);
1166         pte_unmap_unlock(start_pte, ptl);
1167 
1168         /*
1169          * If we forced a TLB flush (either due to running out of
1170          * batch buffers or because we needed to flush dirty TLB
1171          * entries before releasing the ptl), free the batched
1172          * memory too. Restart if we didn't do everything.
1173          */
1174         if (force_flush) {
1175                 force_flush = 0;
1176                 tlb_flush_mmu_free(tlb);
1177 
1178                 if (addr != end)
1179                         goto again;
1180         }
1181 
1182         return addr;
1183 }
1184 
1185 static inline unsigned long zap_pmd_range(struct mmu_gather *tlb,
1186                                 struct vm_area_struct *vma, pud_t *pud,
1187                                 unsigned long addr, unsigned long end,
1188                                 struct zap_details *details)
1189 {
1190         pmd_t *pmd;
1191         unsigned long next;
1192 
1193         pmd = pmd_offset(pud, addr);
1194         do {
1195                 next = pmd_addr_end(addr, end);
1196                 if (pmd_trans_huge(*pmd)) {
1197                         if (next - addr != HPAGE_PMD_SIZE) {
1198 #ifdef CONFIG_DEBUG_VM
1199                                 if (!rwsem_is_locked(&tlb->mm->mmap_sem)) {
1200                                         pr_err("%s: mmap_sem is unlocked! addr=0x%lx end=0x%lx vma->vm_start=0x%lx vma->vm_end=0x%lx\n",
1201                                                 __func__, addr, end,
1202                                                 vma->vm_start,
1203                                                 vma->vm_end);
1204                                         BUG();
1205                                 }
1206 #endif
1207                                 split_huge_page_pmd(vma, addr, pmd);
1208                         } else if (zap_huge_pmd(tlb, vma, pmd, addr))
1209                                 goto next;
1210                         /* fall through */
1211                 }
1212                 /*
1213                  * Here there can be other concurrent MADV_DONTNEED or
1214                  * trans huge page faults running, and if the pmd is
1215                  * none or trans huge it can change under us. This is
1216                  * because MADV_DONTNEED holds the mmap_sem in read
1217                  * mode.
1218                  */
1219                 if (pmd_none_or_trans_huge_or_clear_bad(pmd))
1220                         goto next;
1221                 next = zap_pte_range(tlb, vma, pmd, addr, next, details);
1222 next:
1223                 cond_resched();
1224         } while (pmd++, addr = next, addr != end);
1225 
1226         return addr;
1227 }
1228 
1229 static inline unsigned long zap_pud_range(struct mmu_gather *tlb,
1230                                 struct vm_area_struct *vma, pgd_t *pgd,
1231                                 unsigned long addr, unsigned long end,
1232                                 struct zap_details *details)
1233 {
1234         pud_t *pud;
1235         unsigned long next;
1236 
1237         pud = pud_offset(pgd, addr);
1238         do {
1239                 next = pud_addr_end(addr, end);
1240                 if (pud_none_or_clear_bad(pud))
1241                         continue;
1242                 next = zap_pmd_range(tlb, vma, pud, addr, next, details);
1243         } while (pud++, addr = next, addr != end);
1244 
1245         return addr;
1246 }
1247 
1248 static void unmap_page_range(struct mmu_gather *tlb,
1249                              struct vm_area_struct *vma,
1250                              unsigned long addr, unsigned long end,
1251                              struct zap_details *details)
1252 {
1253         pgd_t *pgd;
1254         unsigned long next;
1255 
1256         if (details && !details->check_mapping)
1257                 details = NULL;
1258 
1259         BUG_ON(addr >= end);
1260         tlb_start_vma(tlb, vma);
1261         pgd = pgd_offset(vma->vm_mm, addr);
1262         do {
1263                 next = pgd_addr_end(addr, end);
1264                 if (pgd_none_or_clear_bad(pgd))
1265                         continue;
1266                 next = zap_pud_range(tlb, vma, pgd, addr, next, details);
1267         } while (pgd++, addr = next, addr != end);
1268         tlb_end_vma(tlb, vma);
1269 }
1270 
1271 
1272 static void unmap_single_vma(struct mmu_gather *tlb,
1273                 struct vm_area_struct *vma, unsigned long start_addr,
1274                 unsigned long end_addr,
1275                 struct zap_details *details)
1276 {
1277         unsigned long start = max(vma->vm_start, start_addr);
1278         unsigned long end;
1279 
1280         if (start >= vma->vm_end)
1281                 return;
1282         end = min(vma->vm_end, end_addr);
1283         if (end <= vma->vm_start)
1284                 return;
1285 
1286         if (vma->vm_file)
1287                 uprobe_munmap(vma, start, end);
1288 
1289         if (unlikely(vma->vm_flags & VM_PFNMAP))
1290                 untrack_pfn(vma, 0, 0);
1291 
1292         if (start != end) {
1293                 if (unlikely(is_vm_hugetlb_page(vma))) {
1294                         /*
1295                          * It is undesirable to test vma->vm_file as it
1296                          * should be non-null for valid hugetlb area.
1297                          * However, vm_file will be NULL in the error
1298                          * cleanup path of mmap_region. When
1299                          * hugetlbfs ->mmap method fails,
1300                          * mmap_region() nullifies vma->vm_file
1301                          * before calling this function to clean up.
1302                          * Since no pte has actually been setup, it is
1303                          * safe to do nothing in this case.
1304                          */
1305                         if (vma->vm_file) {
1306                                 i_mmap_lock_write(vma->vm_file->f_mapping);
1307                                 __unmap_hugepage_range_final(tlb, vma, start, end, NULL);
1308                                 i_mmap_unlock_write(vma->vm_file->f_mapping);
1309                         }
1310                 } else
1311                         unmap_page_range(tlb, vma, start, end, details);
1312         }
1313 }
1314 
1315 /**
1316  * unmap_vmas - unmap a range of memory covered by a list of vma's
1317  * @tlb: address of the caller's struct mmu_gather
1318  * @vma: the starting vma
1319  * @start_addr: virtual address at which to start unmapping
1320  * @end_addr: virtual address at which to end unmapping
1321  *
1322  * Unmap all pages in the vma list.
1323  *
1324  * Only addresses between `start' and `end' will be unmapped.
1325  *
1326  * The VMA list must be sorted in ascending virtual address order.
1327  *
1328  * unmap_vmas() assumes that the caller will flush the whole unmapped address
1329  * range after unmap_vmas() returns.  So the only responsibility here is to
1330  * ensure that any thus-far unmapped pages are flushed before unmap_vmas()
1331  * drops the lock and schedules.
1332  */
1333 void unmap_vmas(struct mmu_gather *tlb,
1334                 struct vm_area_struct *vma, unsigned long start_addr,
1335                 unsigned long end_addr)
1336 {
1337         struct mm_struct *mm = vma->vm_mm;
1338 
1339         mmu_notifier_invalidate_range_start(mm, start_addr, end_addr);
1340         for ( ; vma && vma->vm_start < end_addr; vma = vma->vm_next)
1341                 unmap_single_vma(tlb, vma, start_addr, end_addr, NULL);
1342         mmu_notifier_invalidate_range_end(mm, start_addr, end_addr);
1343 }
1344 
1345 /**
1346  * zap_page_range - remove user pages in a given range
1347  * @vma: vm_area_struct holding the applicable pages
1348  * @start: starting address of pages to zap
1349  * @size: number of bytes to zap
1350  * @details: details of shared cache invalidation
1351  *
1352  * Caller must protect the VMA list
1353  */
1354 void zap_page_range(struct vm_area_struct *vma, unsigned long start,
1355                 unsigned long size, struct zap_details *details)
1356 {
1357         struct mm_struct *mm = vma->vm_mm;
1358         struct mmu_gather tlb;
1359         unsigned long end = start + size;
1360 
1361         lru_add_drain();
1362         tlb_gather_mmu(&tlb, mm, start, end);
1363         update_hiwater_rss(mm);
1364         mmu_notifier_invalidate_range_start(mm, start, end);
1365         for ( ; vma && vma->vm_start < end; vma = vma->vm_next)
1366                 unmap_single_vma(&tlb, vma, start, end, details);
1367         mmu_notifier_invalidate_range_end(mm, start, end);
1368         tlb_finish_mmu(&tlb, start, end);
1369 }
1370 
1371 /**
1372  * zap_page_range_single - remove user pages in a given range
1373  * @vma: vm_area_struct holding the applicable pages
1374  * @address: starting address of pages to zap
1375  * @size: number of bytes to zap
1376  * @details: details of shared cache invalidation
1377  *
1378  * The range must fit into one VMA.
1379  */
1380 static void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
1381                 unsigned long size, struct zap_details *details)
1382 {
1383         struct mm_struct *mm = vma->vm_mm;
1384         struct mmu_gather tlb;
1385         unsigned long end = address + size;
1386 
1387         lru_add_drain();
1388         tlb_gather_mmu(&tlb, mm, address, end);
1389         update_hiwater_rss(mm);
1390         mmu_notifier_invalidate_range_start(mm, address, end);
1391         unmap_single_vma(&tlb, vma, address, end, details);
1392         mmu_notifier_invalidate_range_end(mm, address, end);
1393         tlb_finish_mmu(&tlb, address, end);
1394 }
1395 
1396 /**
1397  * zap_vma_ptes - remove ptes mapping the vma
1398  * @vma: vm_area_struct holding ptes to be zapped
1399  * @address: starting address of pages to zap
1400  * @size: number of bytes to zap
1401  *
1402  * This function only unmaps ptes assigned to VM_PFNMAP vmas.
1403  *
1404  * The entire address range must be fully contained within the vma.
1405  *
1406  * Returns 0 if successful.
1407  */
1408 int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
1409                 unsigned long size)
1410 {
1411         if (address < vma->vm_start || address + size > vma->vm_end ||
1412                         !(vma->vm_flags & VM_PFNMAP))
1413                 return -1;
1414         zap_page_range_single(vma, address, size, NULL);
1415         return 0;
1416 }
1417 EXPORT_SYMBOL_GPL(zap_vma_ptes);
1418 
1419 pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr,
1420                         spinlock_t **ptl)
1421 {
1422         pgd_t * pgd = pgd_offset(mm, addr);
1423         pud_t * pud = pud_alloc(mm, pgd, addr);
1424         if (pud) {
1425                 pmd_t * pmd = pmd_alloc(mm, pud, addr);
1426                 if (pmd) {
1427                         VM_BUG_ON(pmd_trans_huge(*pmd));
1428                         return pte_alloc_map_lock(mm, pmd, addr, ptl);
1429                 }
1430         }
1431         return NULL;
1432 }
1433 
1434 /*
1435  * This is the old fallback for page remapping.
1436  *
1437  * For historical reasons, it only allows reserved pages. Only
1438  * old drivers should use this, and they needed to mark their
1439  * pages reserved for the old functions anyway.
1440  */
1441 static int insert_page(struct vm_area_struct *vma, unsigned long addr,
1442                         struct page *page, pgprot_t prot)
1443 {
1444         struct mm_struct *mm = vma->vm_mm;
1445         int retval;
1446         pte_t *pte;
1447         spinlock_t *ptl;
1448 
1449         retval = -EINVAL;
1450         if (PageAnon(page))
1451                 goto out;
1452         retval = -ENOMEM;
1453         flush_dcache_page(page);
1454         pte = get_locked_pte(mm, addr, &ptl);
1455         if (!pte)
1456                 goto out;
1457         retval = -EBUSY;
1458         if (!pte_none(*pte))
1459                 goto out_unlock;
1460 
1461         /* Ok, finally just insert the thing.. */
1462         get_page(page);
1463         inc_mm_counter_fast(mm, MM_FILEPAGES);
1464         page_add_file_rmap(page);
1465         set_pte_at(mm, addr, pte, mk_pte(page, prot));
1466 
1467         retval = 0;
1468         pte_unmap_unlock(pte, ptl);
1469         return retval;
1470 out_unlock:
1471         pte_unmap_unlock(pte, ptl);
1472 out:
1473         return retval;
1474 }
1475 
1476 /**
1477  * vm_insert_page - insert single page into user vma
1478  * @vma: user vma to map to
1479  * @addr: target user address of this page
1480  * @page: source kernel page
1481  *
1482  * This allows drivers to insert individual pages they've allocated
1483  * into a user vma.
1484  *
1485  * The page has to be a nice clean _individual_ kernel allocation.
1486  * If you allocate a compound page, you need to have marked it as
1487  * such (__GFP_COMP), or manually just split the page up yourself
1488  * (see split_page()).
1489  *
1490  * NOTE! Traditionally this was done with "remap_pfn_range()" which
1491  * took an arbitrary page protection parameter. This doesn't allow
1492  * that. Your vma protection will have to be set up correctly, which
1493  * means that if you want a shared writable mapping, you'd better
1494  * ask for a shared writable mapping!
1495  *
1496  * The page does not need to be reserved.
1497  *
1498  * Usually this function is called from f_op->mmap() handler
1499  * under mm->mmap_sem write-lock, so it can change vma->vm_flags.
1500  * Caller must set VM_MIXEDMAP on vma if it wants to call this
1501  * function from other places, for example from page-fault handler.
1502  */
1503 int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
1504                         struct page *page)
1505 {
1506         if (addr < vma->vm_start || addr >= vma->vm_end)
1507                 return -EFAULT;
1508         if (!page_count(page))
1509                 return -EINVAL;
1510         if (!(vma->vm_flags & VM_MIXEDMAP)) {
1511                 BUG_ON(down_read_trylock(&vma->vm_mm->mmap_sem));
1512                 BUG_ON(vma->vm_flags & VM_PFNMAP);
1513                 vma->vm_flags |= VM_MIXEDMAP;
1514         }
1515         return insert_page(vma, addr, page, vma->vm_page_prot);
1516 }
1517 EXPORT_SYMBOL(vm_insert_page);
1518 
1519 static int insert_pfn(struct vm_area_struct *vma, unsigned long addr,
1520                         unsigned long pfn, pgprot_t prot)
1521 {
1522         struct mm_struct *mm = vma->vm_mm;
1523         int retval;
1524         pte_t *pte, entry;
1525         spinlock_t *ptl;
1526 
1527         retval = -ENOMEM;
1528         pte = get_locked_pte(mm, addr, &ptl);
1529         if (!pte)
1530                 goto out;
1531         retval = -EBUSY;
1532         if (!pte_none(*pte))
1533                 goto out_unlock;
1534 
1535         /* Ok, finally just insert the thing.. */
1536         entry = pte_mkspecial(pfn_pte(pfn, prot));
1537         set_pte_at(mm, addr, pte, entry);
1538         update_mmu_cache(vma, addr, pte); /* XXX: why not for insert_page? */
1539 
1540         retval = 0;
1541 out_unlock:
1542         pte_unmap_unlock(pte, ptl);
1543 out:
1544         return retval;
1545 }
1546 
1547 /**
1548  * vm_insert_pfn - insert single pfn into user vma
1549  * @vma: user vma to map to
1550  * @addr: target user address of this page
1551  * @pfn: source kernel pfn
1552  *
1553  * Similar to vm_insert_page, this allows drivers to insert individual pages
1554  * they've allocated into a user vma. Same comments apply.
1555  *
1556  * This function should only be called from a vm_ops->fault handler, and
1557  * in that case the handler should return NULL.
1558  *
1559  * vma cannot be a COW mapping.
1560  *
1561  * As this is called only for pages that do not currently exist, we
1562  * do not need to flush old virtual caches or the TLB.
1563  */
1564 int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
1565                         unsigned long pfn)
1566 {
1567         int ret;
1568         pgprot_t pgprot = vma->vm_page_prot;
1569         /*
1570          * Technically, architectures with pte_special can avoid all these
1571          * restrictions (same for remap_pfn_range).  However we would like
1572          * consistency in testing and feature parity among all, so we should
1573          * try to keep these invariants in place for everybody.
1574          */
1575         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
1576         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
1577                                                 (VM_PFNMAP|VM_MIXEDMAP));
1578         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
1579         BUG_ON((vma->vm_flags & VM_MIXEDMAP) && pfn_valid(pfn));
1580 
1581         if (addr < vma->vm_start || addr >= vma->vm_end)
1582                 return -EFAULT;
1583         if (track_pfn_insert(vma, &pgprot, pfn))
1584                 return -EINVAL;
1585 
1586         ret = insert_pfn(vma, addr, pfn, pgprot);
1587 
1588         return ret;
1589 }
1590 EXPORT_SYMBOL(vm_insert_pfn);
1591 
1592 int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
1593                         unsigned long pfn)
1594 {
1595         BUG_ON(!(vma->vm_flags & VM_MIXEDMAP));
1596 
1597         if (addr < vma->vm_start || addr >= vma->vm_end)
1598                 return -EFAULT;
1599 
1600         /*
1601          * If we don't have pte special, then we have to use the pfn_valid()
1602          * based VM_MIXEDMAP scheme (see vm_normal_page), and thus we *must*
1603          * refcount the page if pfn_valid is true (hence insert_page rather
1604          * than insert_pfn).  If a zero_pfn were inserted into a VM_MIXEDMAP
1605          * without pte special, it would there be refcounted as a normal page.
1606          */
1607         if (!HAVE_PTE_SPECIAL && pfn_valid(pfn)) {
1608                 struct page *page;
1609 
1610                 page = pfn_to_page(pfn);
1611                 return insert_page(vma, addr, page, vma->vm_page_prot);
1612         }
1613         return insert_pfn(vma, addr, pfn, vma->vm_page_prot);
1614 }
1615 EXPORT_SYMBOL(vm_insert_mixed);
1616 
1617 /*
1618  * maps a range of physical memory into the requested pages. the old
1619  * mappings are removed. any references to nonexistent pages results
1620  * in null mappings (currently treated as "copy-on-access")
1621  */
1622 static int remap_pte_range(struct mm_struct *mm, pmd_t *pmd,
1623                         unsigned long addr, unsigned long end,
1624                         unsigned long pfn, pgprot_t prot)
1625 {
1626         pte_t *pte;
1627         spinlock_t *ptl;
1628 
1629         pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
1630         if (!pte)
1631                 return -ENOMEM;
1632         arch_enter_lazy_mmu_mode();
1633         do {
1634                 BUG_ON(!pte_none(*pte));
1635                 set_pte_at(mm, addr, pte, pte_mkspecial(pfn_pte(pfn, prot)));
1636                 pfn++;
1637         } while (pte++, addr += PAGE_SIZE, addr != end);
1638         arch_leave_lazy_mmu_mode();
1639         pte_unmap_unlock(pte - 1, ptl);
1640         return 0;
1641 }
1642 
1643 static inline int remap_pmd_range(struct mm_struct *mm, pud_t *pud,
1644                         unsigned long addr, unsigned long end,
1645                         unsigned long pfn, pgprot_t prot)
1646 {
1647         pmd_t *pmd;
1648         unsigned long next;
1649 
1650         pfn -= addr >> PAGE_SHIFT;
1651         pmd = pmd_alloc(mm, pud, addr);
1652         if (!pmd)
1653                 return -ENOMEM;
1654         VM_BUG_ON(pmd_trans_huge(*pmd));
1655         do {
1656                 next = pmd_addr_end(addr, end);
1657                 if (remap_pte_range(mm, pmd, addr, next,
1658                                 pfn + (addr >> PAGE_SHIFT), prot))
1659                         return -ENOMEM;
1660         } while (pmd++, addr = next, addr != end);
1661         return 0;
1662 }
1663 
1664 static inline int remap_pud_range(struct mm_struct *mm, pgd_t *pgd,
1665                         unsigned long addr, unsigned long end,
1666                         unsigned long pfn, pgprot_t prot)
1667 {
1668         pud_t *pud;
1669         unsigned long next;
1670 
1671         pfn -= addr >> PAGE_SHIFT;
1672         pud = pud_alloc(mm, pgd, addr);
1673         if (!pud)
1674                 return -ENOMEM;
1675         do {
1676                 next = pud_addr_end(addr, end);
1677                 if (remap_pmd_range(mm, pud, addr, next,
1678                                 pfn + (addr >> PAGE_SHIFT), prot))
1679                         return -ENOMEM;
1680         } while (pud++, addr = next, addr != end);
1681         return 0;
1682 }
1683 
1684 /**
1685  * remap_pfn_range - remap kernel memory to userspace
1686  * @vma: user vma to map to
1687  * @addr: target user address to start at
1688  * @pfn: physical address of kernel memory
1689  * @size: size of map area
1690  * @prot: page protection flags for this mapping
1691  *
1692  *  Note: this is only safe if the mm semaphore is held when called.
1693  */
1694 int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
1695                     unsigned long pfn, unsigned long size, pgprot_t prot)
1696 {
1697         pgd_t *pgd;
1698         unsigned long next;
1699         unsigned long end = addr + PAGE_ALIGN(size);
1700         struct mm_struct *mm = vma->vm_mm;
1701         int err;
1702 
1703         /*
1704          * Physically remapped pages are special. Tell the
1705          * rest of the world about it:
1706          *   VM_IO tells people not to look at these pages
1707          *      (accesses can have side effects).
1708          *   VM_PFNMAP tells the core MM that the base pages are just
1709          *      raw PFN mappings, and do not have a "struct page" associated
1710          *      with them.
1711          *   VM_DONTEXPAND
1712          *      Disable vma merging and expanding with mremap().
1713          *   VM_DONTDUMP
1714          *      Omit vma from core dump, even when VM_IO turned off.
1715          *
1716          * There's a horrible special case to handle copy-on-write
1717          * behaviour that some programs depend on. We mark the "original"
1718          * un-COW'ed pages by matching them up with "vma->vm_pgoff".
1719          * See vm_normal_page() for details.
1720          */
1721         if (is_cow_mapping(vma->vm_flags)) {
1722                 if (addr != vma->vm_start || end != vma->vm_end)
1723                         return -EINVAL;
1724                 vma->vm_pgoff = pfn;
1725         }
1726 
1727         err = track_pfn_remap(vma, &prot, pfn, addr, PAGE_ALIGN(size));
1728         if (err)
1729                 return -EINVAL;
1730 
1731         vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
1732 
1733         BUG_ON(addr >= end);
1734         pfn -= addr >> PAGE_SHIFT;
1735         pgd = pgd_offset(mm, addr);
1736         flush_cache_range(vma, addr, end);
1737         do {
1738                 next = pgd_addr_end(addr, end);
1739                 err = remap_pud_range(mm, pgd, addr, next,
1740                                 pfn + (addr >> PAGE_SHIFT), prot);
1741                 if (err)
1742                         break;
1743         } while (pgd++, addr = next, addr != end);
1744 
1745         if (err)
1746                 untrack_pfn(vma, pfn, PAGE_ALIGN(size));
1747 
1748         return err;
1749 }
1750 EXPORT_SYMBOL(remap_pfn_range);
1751 
1752 /**
1753  * vm_iomap_memory - remap memory to userspace
1754  * @vma: user vma to map to
1755  * @start: start of area
1756  * @len: size of area
1757  *
1758  * This is a simplified io_remap_pfn_range() for common driver use. The
1759  * driver just needs to give us the physical memory range to be mapped,
1760  * we'll figure out the rest from the vma information.
1761  *
1762  * NOTE! Some drivers might want to tweak vma->vm_page_prot first to get
1763  * whatever write-combining details or similar.
1764  */
1765 int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len)
1766 {
1767         unsigned long vm_len, pfn, pages;
1768 
1769         /* Check that the physical memory area passed in looks valid */
1770         if (start + len < start)
1771                 return -EINVAL;
1772         /*
1773          * You *really* shouldn't map things that aren't page-aligned,
1774          * but we've historically allowed it because IO memory might
1775          * just have smaller alignment.
1776          */
1777         len += start & ~PAGE_MASK;
1778         pfn = start >> PAGE_SHIFT;
1779         pages = (len + ~PAGE_MASK) >> PAGE_SHIFT;
1780         if (pfn + pages < pfn)
1781                 return -EINVAL;
1782 
1783         /* We start the mapping 'vm_pgoff' pages into the area */
1784         if (vma->vm_pgoff > pages)
1785                 return -EINVAL;
1786         pfn += vma->vm_pgoff;
1787         pages -= vma->vm_pgoff;
1788 
1789         /* Can we fit all of the mapping? */
1790         vm_len = vma->vm_end - vma->vm_start;
1791         if (vm_len >> PAGE_SHIFT > pages)
1792                 return -EINVAL;
1793 
1794         /* Ok, let it rip */
1795         return io_remap_pfn_range(vma, vma->vm_start, pfn, vm_len, vma->vm_page_prot);
1796 }
1797 EXPORT_SYMBOL(vm_iomap_memory);
1798 
1799 static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
1800                                      unsigned long addr, unsigned long end,
1801                                      pte_fn_t fn, void *data)
1802 {
1803         pte_t *pte;
1804         int err;
1805         pgtable_t token;
1806         spinlock_t *uninitialized_var(ptl);
1807 
1808         pte = (mm == &init_mm) ?
1809                 pte_alloc_kernel(pmd, addr) :
1810                 pte_alloc_map_lock(mm, pmd, addr, &ptl);
1811         if (!pte)
1812                 return -ENOMEM;
1813 
1814         BUG_ON(pmd_huge(*pmd));
1815 
1816         arch_enter_lazy_mmu_mode();
1817 
1818         token = pmd_pgtable(*pmd);
1819 
1820         do {
1821                 err = fn(pte++, token, addr, data);
1822                 if (err)
1823                         break;
1824         } while (addr += PAGE_SIZE, addr != end);
1825 
1826         arch_leave_lazy_mmu_mode();
1827 
1828         if (mm != &init_mm)
1829                 pte_unmap_unlock(pte-1, ptl);
1830         return err;
1831 }
1832 
1833 static int apply_to_pmd_range(struct mm_struct *mm, pud_t *pud,
1834                                      unsigned long addr, unsigned long end,
1835                                      pte_fn_t fn, void *data)
1836 {
1837         pmd_t *pmd;
1838         unsigned long next;
1839         int err;
1840 
1841         BUG_ON(pud_huge(*pud));
1842 
1843         pmd = pmd_alloc(mm, pud, addr);
1844         if (!pmd)
1845                 return -ENOMEM;
1846         do {
1847                 next = pmd_addr_end(addr, end);
1848                 err = apply_to_pte_range(mm, pmd, addr, next, fn, data);
1849                 if (err)
1850                         break;
1851         } while (pmd++, addr = next, addr != end);
1852         return err;
1853 }
1854 
1855 static int apply_to_pud_range(struct mm_struct *mm, pgd_t *pgd,
1856                                      unsigned long addr, unsigned long end,
1857                                      pte_fn_t fn, void *data)
1858 {
1859         pud_t *pud;
1860         unsigned long next;
1861         int err;
1862 
1863         pud = pud_alloc(mm, pgd, addr);
1864         if (!pud)
1865                 return -ENOMEM;
1866         do {
1867                 next = pud_addr_end(addr, end);
1868                 err = apply_to_pmd_range(mm, pud, addr, next, fn, data);
1869                 if (err)
1870                         break;
1871         } while (pud++, addr = next, addr != end);
1872         return err;
1873 }
1874 
1875 /*
1876  * Scan a region of virtual memory, filling in page tables as necessary
1877  * and calling a provided function on each leaf page table.
1878  */
1879 int apply_to_page_range(struct mm_struct *mm, unsigned long addr,
1880                         unsigned long size, pte_fn_t fn, void *data)
1881 {
1882         pgd_t *pgd;
1883         unsigned long next;
1884         unsigned long end = addr + size;
1885         int err;
1886 
1887         BUG_ON(addr >= end);
1888         pgd = pgd_offset(mm, addr);
1889         do {
1890                 next = pgd_addr_end(addr, end);
1891                 err = apply_to_pud_range(mm, pgd, addr, next, fn, data);
1892                 if (err)
1893                         break;
1894         } while (pgd++, addr = next, addr != end);
1895 
1896         return err;
1897 }
1898 EXPORT_SYMBOL_GPL(apply_to_page_range);
1899 
1900 /*
1901  * handle_pte_fault chooses page fault handler according to an entry which was
1902  * read non-atomically.  Before making any commitment, on those architectures
1903  * or configurations (e.g. i386 with PAE) which might give a mix of unmatched
1904  * parts, do_swap_page must check under lock before unmapping the pte and
1905  * proceeding (but do_wp_page is only called after already making such a check;
1906  * and do_anonymous_page can safely check later on).
1907  */
1908 static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd,
1909                                 pte_t *page_table, pte_t orig_pte)
1910 {
1911         int same = 1;
1912 #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
1913         if (sizeof(pte_t) > sizeof(unsigned long)) {
1914                 spinlock_t *ptl = pte_lockptr(mm, pmd);
1915                 spin_lock(ptl);
1916                 same = pte_same(*page_table, orig_pte);
1917                 spin_unlock(ptl);
1918         }
1919 #endif
1920         pte_unmap(page_table);
1921         return same;
1922 }
1923 
1924 static inline void cow_user_page(struct page *dst, struct page *src, unsigned long va, struct vm_area_struct *vma)
1925 {
1926         debug_dma_assert_idle(src);
1927 
1928         /*
1929          * If the source page was a PFN mapping, we don't have
1930          * a "struct page" for it. We do a best-effort copy by
1931          * just copying from the original user address. If that
1932          * fails, we just zero-fill it. Live with it.
1933          */
1934         if (unlikely(!src)) {
1935                 void *kaddr = kmap_atomic(dst);
1936                 void __user *uaddr = (void __user *)(va & PAGE_MASK);
1937 
1938                 /*
1939                  * This really shouldn't fail, because the page is there
1940                  * in the page tables. But it might just be unreadable,
1941                  * in which case we just give up and fill the result with
1942                  * zeroes.
1943                  */
1944                 if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE))
1945                         clear_page(kaddr);
1946                 kunmap_atomic(kaddr);
1947                 flush_dcache_page(dst);
1948         } else
1949                 copy_user_highpage(dst, src, va, vma);
1950 }
1951 
1952 /*
1953  * Notify the address space that the page is about to become writable so that
1954  * it can prohibit this or wait for the page to get into an appropriate state.
1955  *
1956  * We do this without the lock held, so that it can sleep if it needs to.
1957  */
1958 static int do_page_mkwrite(struct vm_area_struct *vma, struct page *page,
1959                unsigned long address)
1960 {
1961         struct vm_fault vmf;
1962         int ret;
1963 
1964         vmf.virtual_address = (void __user *)(address & PAGE_MASK);
1965         vmf.pgoff = page->index;
1966         vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
1967         vmf.page = page;
1968         vmf.cow_page = NULL;
1969 
1970         ret = vma->vm_ops->page_mkwrite(vma, &vmf);
1971         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))
1972                 return ret;
1973         if (unlikely(!(ret & VM_FAULT_LOCKED))) {
1974                 lock_page(page);
1975                 if (!page->mapping) {
1976                         unlock_page(page);
1977                         return 0; /* retry */
1978                 }
1979                 ret |= VM_FAULT_LOCKED;
1980         } else
1981                 VM_BUG_ON_PAGE(!PageLocked(page), page);
1982         return ret;
1983 }
1984 
1985 /*
1986  * Handle write page faults for pages that can be reused in the current vma
1987  *
1988  * This can happen either due to the mapping being with the VM_SHARED flag,
1989  * or due to us being the last reference standing to the page. In either
1990  * case, all we need to do here is to mark the page as writable and update
1991  * any related book-keeping.
1992  */
1993 static inline int wp_page_reuse(struct mm_struct *mm,
1994                         struct vm_area_struct *vma, unsigned long address,
1995                         pte_t *page_table, spinlock_t *ptl, pte_t orig_pte,
1996                         struct page *page, int page_mkwrite,
1997                         int dirty_shared)
1998         __releases(ptl)
1999 {
2000         pte_t entry;
2001         /*
2002          * Clear the pages cpupid information as the existing
2003          * information potentially belongs to a now completely
2004          * unrelated process.
2005          */
2006         if (page)
2007                 page_cpupid_xchg_last(page, (1 << LAST_CPUPID_SHIFT) - 1);
2008 
2009         flush_cache_page(vma, address, pte_pfn(orig_pte));
2010         entry = pte_mkyoung(orig_pte);
2011         entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2012         if (ptep_set_access_flags(vma, address, page_table, entry, 1))
2013                 update_mmu_cache(vma, address, page_table);
2014         pte_unmap_unlock(page_table, ptl);
2015 
2016         if (dirty_shared) {
2017                 struct address_space *mapping;
2018                 int dirtied;
2019 
2020                 if (!page_mkwrite)
2021                         lock_page(page);
2022 
2023                 dirtied = set_page_dirty(page);
2024                 VM_BUG_ON_PAGE(PageAnon(page), page);
2025                 mapping = page->mapping;
2026                 unlock_page(page);
2027                 page_cache_release(page);
2028 
2029                 if ((dirtied || page_mkwrite) && mapping) {
2030                         /*
2031                          * Some device drivers do not set page.mapping
2032                          * but still dirty their pages
2033                          */
2034                         balance_dirty_pages_ratelimited(mapping);
2035                 }
2036 
2037                 if (!page_mkwrite)
2038                         file_update_time(vma->vm_file);
2039         }
2040 
2041         return VM_FAULT_WRITE;
2042 }
2043 
2044 /*
2045  * Handle the case of a page which we actually need to copy to a new page.
2046  *
2047  * Called with mmap_sem locked and the old page referenced, but
2048  * without the ptl held.
2049  *
2050  * High level logic flow:
2051  *
2052  * - Allocate a page, copy the content of the old page to the new one.
2053  * - Handle book keeping and accounting - cgroups, mmu-notifiers, etc.
2054  * - Take the PTL. If the pte changed, bail out and release the allocated page
2055  * - If the pte is still the way we remember it, update the page table and all
2056  *   relevant references. This includes dropping the reference the page-table
2057  *   held to the old page, as well as updating the rmap.
2058  * - In any case, unlock the PTL and drop the reference we took to the old page.
2059  */
2060 static int wp_page_copy(struct mm_struct *mm, struct vm_area_struct *vma,
2061                         unsigned long address, pte_t *page_table, pmd_t *pmd,
2062                         pte_t orig_pte, struct page *old_page)
2063 {
2064         struct page *new_page = NULL;
2065         spinlock_t *ptl = NULL;
2066         pte_t entry;
2067         int page_copied = 0;
2068         const unsigned long mmun_start = address & PAGE_MASK;   /* For mmu_notifiers */
2069         const unsigned long mmun_end = mmun_start + PAGE_SIZE;  /* For mmu_notifiers */
2070         struct mem_cgroup *memcg;
2071 
2072         if (unlikely(anon_vma_prepare(vma)))
2073                 goto oom;
2074 
2075         if (is_zero_pfn(pte_pfn(orig_pte))) {
2076                 new_page = alloc_zeroed_user_highpage_movable(vma, address);
2077                 if (!new_page)
2078                         goto oom;
2079         } else {
2080                 new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
2081                 if (!new_page)
2082                         goto oom;
2083                 cow_user_page(new_page, old_page, address, vma);
2084         }
2085 
2086         if (mem_cgroup_try_charge(new_page, mm, GFP_KERNEL, &memcg))
2087                 goto oom_free_new;
2088 
2089         __SetPageUptodate(new_page);
2090 
2091         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2092 
2093         /*
2094          * Re-check the pte - we dropped the lock
2095          */
2096         page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2097         if (likely(pte_same(*page_table, orig_pte))) {
2098                 if (old_page) {
2099                         if (!PageAnon(old_page)) {
2100                                 dec_mm_counter_fast(mm, MM_FILEPAGES);
2101                                 inc_mm_counter_fast(mm, MM_ANONPAGES);
2102                         }
2103                 } else {
2104                         inc_mm_counter_fast(mm, MM_ANONPAGES);
2105                 }
2106                 flush_cache_page(vma, address, pte_pfn(orig_pte));
2107                 entry = mk_pte(new_page, vma->vm_page_prot);
2108                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2109                 /*
2110                  * Clear the pte entry and flush it first, before updating the
2111                  * pte with the new entry. This will avoid a race condition
2112                  * seen in the presence of one thread doing SMC and another
2113                  * thread doing COW.
2114                  */
2115                 ptep_clear_flush_notify(vma, address, page_table);
2116                 page_add_new_anon_rmap(new_page, vma, address);
2117                 mem_cgroup_commit_charge(new_page, memcg, false);
2118                 lru_cache_add_active_or_unevictable(new_page, vma);
2119                 /*
2120                  * We call the notify macro here because, when using secondary
2121                  * mmu page tables (such as kvm shadow page tables), we want the
2122                  * new page to be mapped directly into the secondary page table.
2123                  */
2124                 set_pte_at_notify(mm, address, page_table, entry);
2125                 update_mmu_cache(vma, address, page_table);
2126                 if (old_page) {
2127                         /*
2128                          * Only after switching the pte to the new page may
2129                          * we remove the mapcount here. Otherwise another
2130                          * process may come and find the rmap count decremented
2131                          * before the pte is switched to the new page, and
2132                          * "reuse" the old page writing into it while our pte
2133                          * here still points into it and can be read by other
2134                          * threads.
2135                          *
2136                          * The critical issue is to order this
2137                          * page_remove_rmap with the ptp_clear_flush above.
2138                          * Those stores are ordered by (if nothing else,)
2139                          * the barrier present in the atomic_add_negative
2140                          * in page_remove_rmap.
2141                          *
2142                          * Then the TLB flush in ptep_clear_flush ensures that
2143                          * no process can access the old page before the
2144                          * decremented mapcount is visible. And the old page
2145                          * cannot be reused until after the decremented
2146                          * mapcount is visible. So transitively, TLBs to
2147                          * old page will be flushed before it can be reused.
2148                          */
2149                         page_remove_rmap(old_page);
2150                 }
2151 
2152                 /* Free the old page.. */
2153                 new_page = old_page;
2154                 page_copied = 1;
2155         } else {
2156                 mem_cgroup_cancel_charge(new_page, memcg);
2157         }
2158 
2159         if (new_page)
2160                 page_cache_release(new_page);
2161 
2162         pte_unmap_unlock(page_table, ptl);
2163         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2164         if (old_page) {
2165                 /*
2166                  * Don't let another task, with possibly unlocked vma,
2167                  * keep the mlocked page.
2168                  */
2169                 if (page_copied && (vma->vm_flags & VM_LOCKED)) {
2170                         lock_page(old_page);    /* LRU manipulation */
2171                         munlock_vma_page(old_page);
2172                         unlock_page(old_page);
2173                 }
2174                 page_cache_release(old_page);
2175         }
2176         return page_copied ? VM_FAULT_WRITE : 0;
2177 oom_free_new:
2178         page_cache_release(new_page);
2179 oom:
2180         if (old_page)
2181                 page_cache_release(old_page);
2182         return VM_FAULT_OOM;
2183 }
2184 
2185 /*
2186  * Handle write page faults for VM_MIXEDMAP or VM_PFNMAP for a VM_SHARED
2187  * mapping
2188  */
2189 static int wp_pfn_shared(struct mm_struct *mm,
2190                         struct vm_area_struct *vma, unsigned long address,
2191                         pte_t *page_table, spinlock_t *ptl, pte_t orig_pte,
2192                         pmd_t *pmd)
2193 {
2194         if (vma->vm_ops && vma->vm_ops->pfn_mkwrite) {
2195                 struct vm_fault vmf = {
2196                         .page = NULL,
2197                         .pgoff = linear_page_index(vma, address),
2198                         .virtual_address = (void __user *)(address & PAGE_MASK),
2199                         .flags = FAULT_FLAG_WRITE | FAULT_FLAG_MKWRITE,
2200                 };
2201                 int ret;
2202 
2203                 pte_unmap_unlock(page_table, ptl);
2204                 ret = vma->vm_ops->pfn_mkwrite(vma, &vmf);
2205                 if (ret & VM_FAULT_ERROR)
2206                         return ret;
2207                 page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2208                 /*
2209                  * We might have raced with another page fault while we
2210                  * released the pte_offset_map_lock.
2211                  */
2212                 if (!pte_same(*page_table, orig_pte)) {
2213                         pte_unmap_unlock(page_table, ptl);
2214                         return 0;
2215                 }
2216         }
2217         return wp_page_reuse(mm, vma, address, page_table, ptl, orig_pte,
2218                              NULL, 0, 0);
2219 }
2220 
2221 static int wp_page_shared(struct mm_struct *mm, struct vm_area_struct *vma,
2222                           unsigned long address, pte_t *page_table,
2223                           pmd_t *pmd, spinlock_t *ptl, pte_t orig_pte,
2224                           struct page *old_page)
2225         __releases(ptl)
2226 {
2227         int page_mkwrite = 0;
2228 
2229         page_cache_get(old_page);
2230 
2231         /*
2232          * Only catch write-faults on shared writable pages,
2233          * read-only shared pages can get COWed by
2234          * get_user_pages(.write=1, .force=1).
2235          */
2236         if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
2237                 int tmp;
2238 
2239                 pte_unmap_unlock(page_table, ptl);
2240                 tmp = do_page_mkwrite(vma, old_page, address);
2241                 if (unlikely(!tmp || (tmp &
2242                                       (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
2243                         page_cache_release(old_page);
2244                         return tmp;
2245                 }
2246                 /*
2247                  * Since we dropped the lock we need to revalidate
2248                  * the PTE as someone else may have changed it.  If
2249                  * they did, we just return, as we can count on the
2250                  * MMU to tell us if they didn't also make it writable.
2251                  */
2252                 page_table = pte_offset_map_lock(mm, pmd, address,
2253                                                  &ptl);
2254                 if (!pte_same(*page_table, orig_pte)) {
2255                         unlock_page(old_page);
2256                         pte_unmap_unlock(page_table, ptl);
2257                         page_cache_release(old_page);
2258                         return 0;
2259                 }
2260                 page_mkwrite = 1;
2261         }
2262 
2263         return wp_page_reuse(mm, vma, address, page_table, ptl,
2264                              orig_pte, old_page, page_mkwrite, 1);
2265 }
2266 
2267 /*
2268  * This routine handles present pages, when users try to write
2269  * to a shared page. It is done by copying the page to a new address
2270  * and decrementing the shared-page counter for the old page.
2271  *
2272  * Note that this routine assumes that the protection checks have been
2273  * done by the caller (the low-level page fault routine in most cases).
2274  * Thus we can safely just mark it writable once we've done any necessary
2275  * COW.
2276  *
2277  * We also mark the page dirty at this point even though the page will
2278  * change only once the write actually happens. This avoids a few races,
2279  * and potentially makes it more efficient.
2280  *
2281  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2282  * but allow concurrent faults), with pte both mapped and locked.
2283  * We return with mmap_sem still held, but pte unmapped and unlocked.
2284  */
2285 static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
2286                 unsigned long address, pte_t *page_table, pmd_t *pmd,
2287                 spinlock_t *ptl, pte_t orig_pte)
2288         __releases(ptl)
2289 {
2290         struct page *old_page;
2291 
2292         old_page = vm_normal_page(vma, address, orig_pte);
2293         if (!old_page) {
2294                 /*
2295                  * VM_MIXEDMAP !pfn_valid() case, or VM_SOFTDIRTY clear on a
2296                  * VM_PFNMAP VMA.
2297                  *
2298                  * We should not cow pages in a shared writeable mapping.
2299                  * Just mark the pages writable and/or call ops->pfn_mkwrite.
2300                  */
2301                 if ((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
2302                                      (VM_WRITE|VM_SHARED))
2303                         return wp_pfn_shared(mm, vma, address, page_table, ptl,
2304                                              orig_pte, pmd);
2305 
2306                 pte_unmap_unlock(page_table, ptl);
2307                 return wp_page_copy(mm, vma, address, page_table, pmd,
2308                                     orig_pte, old_page);
2309         }
2310 
2311         /*
2312          * Take out anonymous pages first, anonymous shared vmas are
2313          * not dirty accountable.
2314          */
2315         if (PageAnon(old_page) && !PageKsm(old_page)) {
2316                 if (!trylock_page(old_page)) {
2317                         page_cache_get(old_page);
2318                         pte_unmap_unlock(page_table, ptl);
2319                         lock_page(old_page);
2320                         page_table = pte_offset_map_lock(mm, pmd, address,
2321                                                          &ptl);
2322                         if (!pte_same(*page_table, orig_pte)) {
2323                                 unlock_page(old_page);
2324                                 pte_unmap_unlock(page_table, ptl);
2325                                 page_cache_release(old_page);
2326                                 return 0;
2327                         }
2328                         page_cache_release(old_page);
2329                 }
2330                 if (reuse_swap_page(old_page)) {
2331                         /*
2332                          * The page is all ours.  Move it to our anon_vma so
2333                          * the rmap code will not search our parent or siblings.
2334                          * Protected against the rmap code by the page lock.
2335                          */
2336                         page_move_anon_rmap(old_page, vma, address);
2337                         unlock_page(old_page);
2338                         return wp_page_reuse(mm, vma, address, page_table, ptl,
2339                                              orig_pte, old_page, 0, 0);
2340                 }
2341                 unlock_page(old_page);
2342         } else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
2343                                         (VM_WRITE|VM_SHARED))) {
2344                 return wp_page_shared(mm, vma, address, page_table, pmd,
2345                                       ptl, orig_pte, old_page);
2346         }
2347 
2348         /*
2349          * Ok, we need to copy. Oh, well..
2350          */
2351         page_cache_get(old_page);
2352 
2353         pte_unmap_unlock(page_table, ptl);
2354         return wp_page_copy(mm, vma, address, page_table, pmd,
2355                             orig_pte, old_page);
2356 }
2357 
2358 static void unmap_mapping_range_vma(struct vm_area_struct *vma,
2359                 unsigned long start_addr, unsigned long end_addr,
2360                 struct zap_details *details)
2361 {
2362         zap_page_range_single(vma, start_addr, end_addr - start_addr, details);
2363 }
2364 
2365 static inline void unmap_mapping_range_tree(struct rb_root *root,
2366                                             struct zap_details *details)
2367 {
2368         struct vm_area_struct *vma;
2369         pgoff_t vba, vea, zba, zea;
2370 
2371         vma_interval_tree_foreach(vma, root,
2372                         details->first_index, details->last_index) {
2373 
2374                 vba = vma->vm_pgoff;
2375                 vea = vba + vma_pages(vma) - 1;
2376                 /* Assume for now that PAGE_CACHE_SHIFT == PAGE_SHIFT */
2377                 zba = details->first_index;
2378                 if (zba < vba)
2379                         zba = vba;
2380                 zea = details->last_index;
2381                 if (zea > vea)
2382                         zea = vea;
2383 
2384                 unmap_mapping_range_vma(vma,
2385                         ((zba - vba) << PAGE_SHIFT) + vma->vm_start,
2386                         ((zea - vba + 1) << PAGE_SHIFT) + vma->vm_start,
2387                                 details);
2388         }
2389 }
2390 
2391 /**
2392  * unmap_mapping_range - unmap the portion of all mmaps in the specified
2393  * address_space corresponding to the specified page range in the underlying
2394  * file.
2395  *
2396  * @mapping: the address space containing mmaps to be unmapped.
2397  * @holebegin: byte in first page to unmap, relative to the start of
2398  * the underlying file.  This will be rounded down to a PAGE_SIZE
2399  * boundary.  Note that this is different from truncate_pagecache(), which
2400  * must keep the partial page.  In contrast, we must get rid of
2401  * partial pages.
2402  * @holelen: size of prospective hole in bytes.  This will be rounded
2403  * up to a PAGE_SIZE boundary.  A holelen of zero truncates to the
2404  * end of the file.
2405  * @even_cows: 1 when truncating a file, unmap even private COWed pages;
2406  * but 0 when invalidating pagecache, don't throw away private data.
2407  */
2408 void unmap_mapping_range(struct address_space *mapping,
2409                 loff_t const holebegin, loff_t const holelen, int even_cows)
2410 {
2411         struct zap_details details;
2412         pgoff_t hba = holebegin >> PAGE_SHIFT;
2413         pgoff_t hlen = (holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
2414 
2415         /* Check for overflow. */
2416         if (sizeof(holelen) > sizeof(hlen)) {
2417                 long long holeend =
2418                         (holebegin + holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
2419                 if (holeend & ~(long long)ULONG_MAX)
2420                         hlen = ULONG_MAX - hba + 1;
2421         }
2422 
2423         details.check_mapping = even_cows? NULL: mapping;
2424         details.first_index = hba;
2425         details.last_index = hba + hlen - 1;
2426         if (details.last_index < details.first_index)
2427                 details.last_index = ULONG_MAX;
2428 
2429 
2430         /* DAX uses i_mmap_lock to serialise file truncate vs page fault */
2431         i_mmap_lock_write(mapping);
2432         if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap)))
2433                 unmap_mapping_range_tree(&mapping->i_mmap, &details);
2434         i_mmap_unlock_write(mapping);
2435 }
2436 EXPORT_SYMBOL(unmap_mapping_range);
2437 
2438 /*
2439  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2440  * but allow concurrent faults), and pte mapped but not yet locked.
2441  * We return with pte unmapped and unlocked.
2442  *
2443  * We return with the mmap_sem locked or unlocked in the same cases
2444  * as does filemap_fault().
2445  */
2446 static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
2447                 unsigned long address, pte_t *page_table, pmd_t *pmd,
2448                 unsigned int flags, pte_t orig_pte)
2449 {
2450         spinlock_t *ptl;
2451         struct page *page, *swapcache;
2452         struct mem_cgroup *memcg;
2453         swp_entry_t entry;
2454         pte_t pte;
2455         int locked;
2456         int exclusive = 0;
2457         int ret = 0;
2458 
2459         if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
2460                 goto out;
2461 
2462         entry = pte_to_swp_entry(orig_pte);
2463         if (unlikely(non_swap_entry(entry))) {
2464                 if (is_migration_entry(entry)) {
2465                         migration_entry_wait(mm, pmd, address);
2466                 } else if (is_hwpoison_entry(entry)) {
2467                         ret = VM_FAULT_HWPOISON;
2468                 } else {
2469                         print_bad_pte(vma, address, orig_pte, NULL);
2470                         ret = VM_FAULT_SIGBUS;
2471                 }
2472                 goto out;
2473         }
2474         delayacct_set_flag(DELAYACCT_PF_SWAPIN);
2475         page = lookup_swap_cache(entry);
2476         if (!page) {
2477                 page = swapin_readahead(entry,
2478                                         GFP_HIGHUSER_MOVABLE, vma, address);
2479                 if (!page) {
2480                         /*
2481                          * Back out if somebody else faulted in this pte
2482                          * while we released the pte lock.
2483                          */
2484                         page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2485                         if (likely(pte_same(*page_table, orig_pte)))
2486                                 ret = VM_FAULT_OOM;
2487                         delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
2488                         goto unlock;
2489                 }
2490 
2491                 /* Had to read the page from swap area: Major fault */
2492                 ret = VM_FAULT_MAJOR;
2493                 count_vm_event(PGMAJFAULT);
2494                 mem_cgroup_count_vm_event(mm, PGMAJFAULT);
2495         } else if (PageHWPoison(page)) {
2496                 /*
2497                  * hwpoisoned dirty swapcache pages are kept for killing
2498                  * owner processes (which may be unknown at hwpoison time)
2499                  */
2500                 ret = VM_FAULT_HWPOISON;
2501                 delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
2502                 swapcache = page;
2503                 goto out_release;
2504         }
2505 
2506         swapcache = page;
2507         locked = lock_page_or_retry(page, mm, flags);
2508 
2509         delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
2510         if (!locked) {
2511                 ret |= VM_FAULT_RETRY;
2512                 goto out_release;
2513         }
2514 
2515         /*
2516          * Make sure try_to_free_swap or reuse_swap_page or swapoff did not
2517          * release the swapcache from under us.  The page pin, and pte_same
2518          * test below, are not enough to exclude that.  Even if it is still
2519          * swapcache, we need to check that the page's swap has not changed.
2520          */
2521         if (unlikely(!PageSwapCache(page) || page_private(page) != entry.val))
2522                 goto out_page;
2523 
2524         page = ksm_might_need_to_copy(page, vma, address);
2525         if (unlikely(!page)) {
2526                 ret = VM_FAULT_OOM;
2527                 page = swapcache;
2528                 goto out_page;
2529         }
2530 
2531         if (mem_cgroup_try_charge(page, mm, GFP_KERNEL, &memcg)) {
2532                 ret = VM_FAULT_OOM;
2533                 goto out_page;
2534         }
2535 
2536         /*
2537          * Back out if somebody else already faulted in this pte.
2538          */
2539         page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2540         if (unlikely(!pte_same(*page_table, orig_pte)))
2541                 goto out_nomap;
2542 
2543         if (unlikely(!PageUptodate(page))) {
2544                 ret = VM_FAULT_SIGBUS;
2545                 goto out_nomap;
2546         }
2547 
2548         /*
2549          * The page isn't present yet, go ahead with the fault.
2550          *
2551          * Be careful about the sequence of operations here.
2552          * To get its accounting right, reuse_swap_page() must be called
2553          * while the page is counted on swap but not yet in mapcount i.e.
2554          * before page_add_anon_rmap() and swap_free(); try_to_free_swap()
2555          * must be called after the swap_free(), or it will never succeed.
2556          */
2557 
2558         inc_mm_counter_fast(mm, MM_ANONPAGES);
2559         dec_mm_counter_fast(mm, MM_SWAPENTS);
2560         pte = mk_pte(page, vma->vm_page_prot);
2561         if ((flags & FAULT_FLAG_WRITE) && reuse_swap_page(page)) {
2562                 pte = maybe_mkwrite(pte_mkdirty(pte), vma);
2563                 flags &= ~FAULT_FLAG_WRITE;
2564                 ret |= VM_FAULT_WRITE;
2565                 exclusive = 1;
2566         }
2567         flush_icache_page(vma, page);
2568         if (pte_swp_soft_dirty(orig_pte))
2569                 pte = pte_mksoft_dirty(pte);
2570         set_pte_at(mm, address, page_table, pte);
2571         if (page == swapcache) {
2572                 do_page_add_anon_rmap(page, vma, address, exclusive);
2573                 mem_cgroup_commit_charge(page, memcg, true);
2574         } else { /* ksm created a completely new copy */
2575                 page_add_new_anon_rmap(page, vma, address);
2576                 mem_cgroup_commit_charge(page, memcg, false);
2577                 lru_cache_add_active_or_unevictable(page, vma);
2578         }
2579 
2580         swap_free(entry);
2581         if (vm_swap_full() || (vma->vm_flags & VM_LOCKED) || PageMlocked(page))
2582                 try_to_free_swap(page);
2583         unlock_page(page);
2584         if (page != swapcache) {
2585                 /*
2586                  * Hold the lock to avoid the swap entry to be reused
2587                  * until we take the PT lock for the pte_same() check
2588                  * (to avoid false positives from pte_same). For
2589                  * further safety release the lock after the swap_free
2590                  * so that the swap count won't change under a
2591                  * parallel locked swapcache.
2592                  */
2593                 unlock_page(swapcache);
2594                 page_cache_release(swapcache);
2595         }
2596 
2597         if (flags & FAULT_FLAG_WRITE) {
2598                 ret |= do_wp_page(mm, vma, address, page_table, pmd, ptl, pte);
2599                 if (ret & VM_FAULT_ERROR)
2600                         ret &= VM_FAULT_ERROR;
2601                 goto out;
2602         }
2603 
2604         /* No need to invalidate - it was non-present before */
2605         update_mmu_cache(vma, address, page_table);
2606 unlock:
2607         pte_unmap_unlock(page_table, ptl);
2608 out:
2609         return ret;
2610 out_nomap:
2611         mem_cgroup_cancel_charge(page, memcg);
2612         pte_unmap_unlock(page_table, ptl);
2613 out_page:
2614         unlock_page(page);
2615 out_release:
2616         page_cache_release(page);
2617         if (page != swapcache) {
2618                 unlock_page(swapcache);
2619                 page_cache_release(swapcache);
2620         }
2621         return ret;
2622 }
2623 
2624 /*
2625  * This is like a special single-page "expand_{down|up}wards()",
2626  * except we must first make sure that 'address{-|+}PAGE_SIZE'
2627  * doesn't hit another vma.
2628  */
2629 static inline int check_stack_guard_page(struct vm_area_struct *vma, unsigned long address)
2630 {
2631         address &= PAGE_MASK;
2632         if ((vma->vm_flags & VM_GROWSDOWN) && address == vma->vm_start) {
2633                 struct vm_area_struct *prev = vma->vm_prev;
2634 
2635                 /*
2636                  * Is there a mapping abutting this one below?
2637                  *
2638                  * That's only ok if it's the same stack mapping
2639                  * that has gotten split..
2640                  */
2641                 if (prev && prev->vm_end == address)
2642                         return prev->vm_flags & VM_GROWSDOWN ? 0 : -ENOMEM;
2643 
2644                 return expand_downwards(vma, address - PAGE_SIZE);
2645         }
2646         if ((vma->vm_flags & VM_GROWSUP) && address + PAGE_SIZE == vma->vm_end) {
2647                 struct vm_area_struct *next = vma->vm_next;
2648 
2649                 /* As VM_GROWSDOWN but s/below/above/ */
2650                 if (next && next->vm_start == address + PAGE_SIZE)
2651                         return next->vm_flags & VM_GROWSUP ? 0 : -ENOMEM;
2652 
2653                 return expand_upwards(vma, address + PAGE_SIZE);
2654         }
2655         return 0;
2656 }
2657 
2658 /*
2659  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2660  * but allow concurrent faults), and pte mapped but not yet locked.
2661  * We return with mmap_sem still held, but pte unmapped and unlocked.
2662  */
2663 static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
2664                 unsigned long address, pte_t *page_table, pmd_t *pmd,
2665                 unsigned int flags)
2666 {
2667         struct mem_cgroup *memcg;
2668         struct page *page;
2669         spinlock_t *ptl;
2670         pte_t entry;
2671 
2672         pte_unmap(page_table);
2673 
2674         /* File mapping without ->vm_ops ? */
2675         if (vma->vm_flags & VM_SHARED)
2676                 return VM_FAULT_SIGBUS;
2677 
2678         /* Check if we need to add a guard page to the stack */
2679         if (check_stack_guard_page(vma, address) < 0)
2680                 return VM_FAULT_SIGSEGV;
2681 
2682         /* Use the zero-page for reads */
2683         if (!(flags & FAULT_FLAG_WRITE) && !mm_forbids_zeropage(mm)) {
2684                 entry = pte_mkspecial(pfn_pte(my_zero_pfn(address),
2685                                                 vma->vm_page_prot));
2686                 page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2687                 if (!pte_none(*page_table))
2688                         goto unlock;
2689                 /* Deliver the page fault to userland, check inside PT lock */
2690                 if (userfaultfd_missing(vma)) {
2691                         pte_unmap_unlock(page_table, ptl);
2692                         return handle_userfault(vma, address, flags,
2693                                                 VM_UFFD_MISSING);
2694                 }
2695                 goto setpte;
2696         }
2697 
2698         /* Allocate our own private page. */
2699         if (unlikely(anon_vma_prepare(vma)))
2700                 goto oom;
2701         page = alloc_zeroed_user_highpage_movable(vma, address);
2702         if (!page)
2703                 goto oom;
2704 
2705         if (mem_cgroup_try_charge(page, mm, GFP_KERNEL, &memcg))
2706                 goto oom_free_page;
2707 
2708         /*
2709          * The memory barrier inside __SetPageUptodate makes sure that
2710          * preceeding stores to the page contents become visible before
2711          * the set_pte_at() write.
2712          */
2713         __SetPageUptodate(page);
2714 
2715         entry = mk_pte(page, vma->vm_page_prot);
2716         if (vma->vm_flags & VM_WRITE)
2717                 entry = pte_mkwrite(pte_mkdirty(entry));
2718 
2719         page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2720         if (!pte_none(*page_table))
2721                 goto release;
2722 
2723         /* Deliver the page fault to userland, check inside PT lock */
2724         if (userfaultfd_missing(vma)) {
2725                 pte_unmap_unlock(page_table, ptl);
2726                 mem_cgroup_cancel_charge(page, memcg);
2727                 page_cache_release(page);
2728                 return handle_userfault(vma, address, flags,
2729                                         VM_UFFD_MISSING);
2730         }
2731 
2732         inc_mm_counter_fast(mm, MM_ANONPAGES);
2733         page_add_new_anon_rmap(page, vma, address);
2734         mem_cgroup_commit_charge(page, memcg, false);
2735         lru_cache_add_active_or_unevictable(page, vma);
2736 setpte:
2737         set_pte_at(mm, address, page_table, entry);
2738 
2739         /* No need to invalidate - it was non-present before */
2740         update_mmu_cache(vma, address, page_table);
2741 unlock:
2742         pte_unmap_unlock(page_table, ptl);
2743         return 0;
2744 release:
2745         mem_cgroup_cancel_charge(page, memcg);
2746         page_cache_release(page);
2747         goto unlock;
2748 oom_free_page:
2749         page_cache_release(page);
2750 oom:
2751         return VM_FAULT_OOM;
2752 }
2753 
2754 /*
2755  * The mmap_sem must have been held on entry, and may have been
2756  * released depending on flags and vma->vm_ops->fault() return value.
2757  * See filemap_fault() and __lock_page_retry().
2758  */
2759 static int __do_fault(struct vm_area_struct *vma, unsigned long address,
2760                         pgoff_t pgoff, unsigned int flags,
2761                         struct page *cow_page, struct page **page)
2762 {
2763         struct vm_fault vmf;
2764         int ret;
2765 
2766         vmf.virtual_address = (void __user *)(address & PAGE_MASK);
2767         vmf.pgoff = pgoff;
2768         vmf.flags = flags;
2769         vmf.page = NULL;
2770         vmf.cow_page = cow_page;
2771 
2772         ret = vma->vm_ops->fault(vma, &vmf);
2773         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
2774                 return ret;
2775         if (!vmf.page)
2776                 goto out;
2777 
2778         if (unlikely(PageHWPoison(vmf.page))) {
2779                 if (ret & VM_FAULT_LOCKED)
2780                         unlock_page(vmf.page);
2781                 page_cache_release(vmf.page);
2782                 return VM_FAULT_HWPOISON;
2783         }
2784 
2785         if (unlikely(!(ret & VM_FAULT_LOCKED)))
2786                 lock_page(vmf.page);
2787         else
2788                 VM_BUG_ON_PAGE(!PageLocked(vmf.page), vmf.page);
2789 
2790  out:
2791         *page = vmf.page;
2792         return ret;
2793 }
2794 
2795 /**
2796  * do_set_pte - setup new PTE entry for given page and add reverse page mapping.
2797  *
2798  * @vma: virtual memory area
2799  * @address: user virtual address
2800  * @page: page to map
2801  * @pte: pointer to target page table entry
2802  * @write: true, if new entry is writable
2803  * @anon: true, if it's anonymous page
2804  *
2805  * Caller must hold page table lock relevant for @pte.
2806  *
2807  * Target users are page handler itself and implementations of
2808  * vm_ops->map_pages.
2809  */
2810 void do_set_pte(struct vm_area_struct *vma, unsigned long address,
2811                 struct page *page, pte_t *pte, bool write, bool anon)
2812 {
2813         pte_t entry;
2814 
2815         flush_icache_page(vma, page);
2816         entry = mk_pte(page, vma->vm_page_prot);
2817         if (write)
2818                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2819         if (anon) {
2820                 inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
2821                 page_add_new_anon_rmap(page, vma, address);
2822         } else {
2823                 inc_mm_counter_fast(vma->vm_mm, MM_FILEPAGES);
2824                 page_add_file_rmap(page);
2825         }
2826         set_pte_at(vma->vm_mm, address, pte, entry);
2827 
2828         /* no need to invalidate: a not-present page won't be cached */
2829         update_mmu_cache(vma, address, pte);
2830 }
2831 
2832 static unsigned long fault_around_bytes __read_mostly =
2833         rounddown_pow_of_two(65536);
2834 
2835 #ifdef CONFIG_DEBUG_FS
2836 static int fault_around_bytes_get(void *data, u64 *val)
2837 {
2838         *val = fault_around_bytes;
2839         return 0;
2840 }
2841 
2842 /*
2843  * fault_around_pages() and fault_around_mask() expects fault_around_bytes
2844  * rounded down to nearest page order. It's what do_fault_around() expects to
2845  * see.
2846  */
2847 static int fault_around_bytes_set(void *data, u64 val)
2848 {
2849         if (val / PAGE_SIZE > PTRS_PER_PTE)
2850                 return -EINVAL;
2851         if (val > PAGE_SIZE)
2852                 fault_around_bytes = rounddown_pow_of_two(val);
2853         else
2854                 fault_around_bytes = PAGE_SIZE; /* rounddown_pow_of_two(0) is undefined */
2855         return 0;
2856 }
2857 DEFINE_SIMPLE_ATTRIBUTE(fault_around_bytes_fops,
2858                 fault_around_bytes_get, fault_around_bytes_set, "%llu\n");
2859 
2860 static int __init fault_around_debugfs(void)
2861 {
2862         void *ret;
2863 
2864         ret = debugfs_create_file("fault_around_bytes", 0644, NULL, NULL,
2865                         &fault_around_bytes_fops);
2866         if (!ret)
2867                 pr_warn("Failed to create fault_around_bytes in debugfs");
2868         return 0;
2869 }
2870 late_initcall(fault_around_debugfs);
2871 #endif
2872 
2873 /*
2874  * do_fault_around() tries to map few pages around the fault address. The hope
2875  * is that the pages will be needed soon and this will lower the number of
2876  * faults to handle.
2877  *
2878  * It uses vm_ops->map_pages() to map the pages, which skips the page if it's
2879  * not ready to be mapped: not up-to-date, locked, etc.
2880  *
2881  * This function is called with the page table lock taken. In the split ptlock
2882  * case the page table lock only protects only those entries which belong to
2883  * the page table corresponding to the fault address.
2884  *
2885  * This function doesn't cross the VMA boundaries, in order to call map_pages()
2886  * only once.
2887  *
2888  * fault_around_pages() defines how many pages we'll try to map.
2889  * do_fault_around() expects it to return a power of two less than or equal to
2890  * PTRS_PER_PTE.
2891  *
2892  * The virtual address of the area that we map is naturally aligned to the
2893  * fault_around_pages() value (and therefore to page order).  This way it's
2894  * easier to guarantee that we don't cross page table boundaries.
2895  */
2896 static void do_fault_around(struct vm_area_struct *vma, unsigned long address,
2897                 pte_t *pte, pgoff_t pgoff, unsigned int flags)
2898 {
2899         unsigned long start_addr, nr_pages, mask;
2900         pgoff_t max_pgoff;
2901         struct vm_fault vmf;
2902         int off;
2903 
2904         nr_pages = READ_ONCE(fault_around_bytes) >> PAGE_SHIFT;
2905         mask = ~(nr_pages * PAGE_SIZE - 1) & PAGE_MASK;
2906 
2907         start_addr = max(address & mask, vma->vm_start);
2908         off = ((address - start_addr) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
2909         pte -= off;
2910         pgoff -= off;
2911 
2912         /*
2913          *  max_pgoff is either end of page table or end of vma
2914          *  or fault_around_pages() from pgoff, depending what is nearest.
2915          */
2916         max_pgoff = pgoff - ((start_addr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1)) +
2917                 PTRS_PER_PTE - 1;
2918         max_pgoff = min3(max_pgoff, vma_pages(vma) + vma->vm_pgoff - 1,
2919                         pgoff + nr_pages - 1);
2920 
2921         /* Check if it makes any sense to call ->map_pages */
2922         while (!pte_none(*pte)) {
2923                 if (++pgoff > max_pgoff)
2924                         return;
2925                 start_addr += PAGE_SIZE;
2926                 if (start_addr >= vma->vm_end)
2927                         return;
2928                 pte++;
2929         }
2930 
2931         vmf.virtual_address = (void __user *) start_addr;
2932         vmf.pte = pte;
2933         vmf.pgoff = pgoff;
2934         vmf.max_pgoff = max_pgoff;
2935         vmf.flags = flags;
2936         vma->vm_ops->map_pages(vma, &vmf);
2937 }
2938 
2939 static int do_read_fault(struct mm_struct *mm, struct vm_area_struct *vma,
2940                 unsigned long address, pmd_t *pmd,
2941                 pgoff_t pgoff, unsigned int flags, pte_t orig_pte)
2942 {
2943         struct page *fault_page;
2944         spinlock_t *ptl;
2945         pte_t *pte;
2946         int ret = 0;
2947 
2948         /*
2949          * Let's call ->map_pages() first and use ->fault() as fallback
2950          * if page by the offset is not ready to be mapped (cold cache or
2951          * something).
2952          */
2953         if (vma->vm_ops->map_pages && fault_around_bytes >> PAGE_SHIFT > 1) {
2954                 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2955                 do_fault_around(vma, address, pte, pgoff, flags);
2956                 if (!pte_same(*pte, orig_pte))
2957                         goto unlock_out;
2958                 pte_unmap_unlock(pte, ptl);
2959         }
2960 
2961         ret = __do_fault(vma, address, pgoff, flags, NULL, &fault_page);
2962         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
2963                 return ret;
2964 
2965         pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2966         if (unlikely(!pte_same(*pte, orig_pte))) {
2967                 pte_unmap_unlock(pte, ptl);
2968                 unlock_page(fault_page);
2969                 page_cache_release(fault_page);
2970                 return ret;
2971         }
2972         do_set_pte(vma, address, fault_page, pte, false, false);
2973         unlock_page(fault_page);
2974 unlock_out:
2975         pte_unmap_unlock(pte, ptl);
2976         return ret;
2977 }
2978 
2979 static int do_cow_fault(struct mm_struct *mm, struct vm_area_struct *vma,
2980                 unsigned long address, pmd_t *pmd,
2981                 pgoff_t pgoff, unsigned int flags, pte_t orig_pte)
2982 {
2983         struct page *fault_page, *new_page;
2984         struct mem_cgroup *memcg;
2985         spinlock_t *ptl;
2986         pte_t *pte;
2987         int ret;
2988 
2989         if (unlikely(anon_vma_prepare(vma)))
2990                 return VM_FAULT_OOM;
2991 
2992         new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
2993         if (!new_page)
2994                 return VM_FAULT_OOM;
2995 
2996         if (mem_cgroup_try_charge(new_page, mm, GFP_KERNEL, &memcg)) {
2997                 page_cache_release(new_page);
2998                 return VM_FAULT_OOM;
2999         }
3000 
3001         ret = __do_fault(vma, address, pgoff, flags, new_page, &fault_page);
3002         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
3003                 goto uncharge_out;
3004 
3005         if (fault_page)
3006                 copy_user_highpage(new_page, fault_page, address, vma);
3007         __SetPageUptodate(new_page);
3008 
3009         pte = pte_offset_map_lock(mm, pmd, address, &ptl);
3010         if (unlikely(!pte_same(*pte, orig_pte))) {
3011                 pte_unmap_unlock(pte, ptl);
3012                 if (fault_page) {
3013                         unlock_page(fault_page);
3014                         page_cache_release(fault_page);
3015                 } else {
3016                         /*
3017                          * The fault handler has no page to lock, so it holds
3018                          * i_mmap_lock for read to protect against truncate.
3019                          */
3020                         i_mmap_unlock_read(vma->vm_file->f_mapping);
3021                 }
3022                 goto uncharge_out;
3023         }
3024         do_set_pte(vma, address, new_page, pte, true, true);
3025         mem_cgroup_commit_charge(new_page, memcg, false);
3026         lru_cache_add_active_or_unevictable(new_page, vma);
3027         pte_unmap_unlock(pte, ptl);
3028         if (fault_page) {
3029                 unlock_page(fault_page);
3030                 page_cache_release(fault_page);
3031         } else {
3032                 /*
3033                  * The fault handler has no page to lock, so it holds
3034                  * i_mmap_lock for read to protect against truncate.
3035                  */
3036                 i_mmap_unlock_read(vma->vm_file->f_mapping);
3037         }
3038         return ret;
3039 uncharge_out:
3040         mem_cgroup_cancel_charge(new_page, memcg);
3041         page_cache_release(new_page);
3042         return ret;
3043 }
3044 
3045 static int do_shared_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3046                 unsigned long address, pmd_t *pmd,
3047                 pgoff_t pgoff, unsigned int flags, pte_t orig_pte)
3048 {
3049         struct page *fault_page;
3050         struct address_space *mapping;
3051         spinlock_t *ptl;
3052         pte_t *pte;
3053         int dirtied = 0;
3054         int ret, tmp;
3055 
3056         ret = __do_fault(vma, address, pgoff, flags, NULL, &fault_page);
3057         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
3058                 return ret;
3059 
3060         /*
3061          * Check if the backing address space wants to know that the page is
3062          * about to become writable
3063          */
3064         if (vma->vm_ops->page_mkwrite) {
3065                 unlock_page(fault_page);
3066                 tmp = do_page_mkwrite(vma, fault_page, address);
3067                 if (unlikely(!tmp ||
3068                                 (tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
3069                         page_cache_release(fault_page);
3070                         return tmp;
3071                 }
3072         }
3073 
3074         pte = pte_offset_map_lock(mm, pmd, address, &ptl);
3075         if (unlikely(!pte_same(*pte, orig_pte))) {
3076                 pte_unmap_unlock(pte, ptl);
3077                 unlock_page(fault_page);
3078                 page_cache_release(fault_page);
3079                 return ret;
3080         }
3081         do_set_pte(vma, address, fault_page, pte, true, false);
3082         pte_unmap_unlock(pte, ptl);
3083 
3084         if (set_page_dirty(fault_page))
3085                 dirtied = 1;
3086         /*
3087          * Take a local copy of the address_space - page.mapping may be zeroed
3088          * by truncate after unlock_page().   The address_space itself remains
3089          * pinned by vma->vm_file's reference.  We rely on unlock_page()'s
3090          * release semantics to prevent the compiler from undoing this copying.
3091          */
3092         mapping = fault_page->mapping;
3093         unlock_page(fault_page);
3094         if ((dirtied || vma->vm_ops->page_mkwrite) && mapping) {
3095                 /*
3096                  * Some device drivers do not set page.mapping but still
3097                  * dirty their pages
3098                  */
3099                 balance_dirty_pages_ratelimited(mapping);
3100         }
3101 
3102         if (!vma->vm_ops->page_mkwrite)
3103                 file_update_time(vma->vm_file);
3104 
3105         return ret;
3106 }
3107 
3108 /*
3109  * We enter with non-exclusive mmap_sem (to exclude vma changes,
3110  * but allow concurrent faults).
3111  * The mmap_sem may have been released depending on flags and our
3112  * return value.  See filemap_fault() and __lock_page_or_retry().
3113  */
3114 static int do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3115                 unsigned long address, pte_t *page_table, pmd_t *pmd,
3116                 unsigned int flags, pte_t orig_pte)
3117 {
3118         pgoff_t pgoff = (((address & PAGE_MASK)
3119                         - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
3120 
3121         pte_unmap(page_table);
3122         /* The VMA was not fully populated on mmap() or missing VM_DONTEXPAND */
3123         if (!vma->vm_ops->fault)
3124                 return VM_FAULT_SIGBUS;
3125         if (!(flags & FAULT_FLAG_WRITE))
3126                 return do_read_fault(mm, vma, address, pmd, pgoff, flags,
3127                                 orig_pte);
3128         if (!(vma->vm_flags & VM_SHARED))
3129                 return do_cow_fault(mm, vma, address, pmd, pgoff, flags,
3130                                 orig_pte);
3131         return do_shared_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
3132 }
3133 
3134 static int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,
3135                                 unsigned long addr, int page_nid,
3136                                 int *flags)
3137 {
3138         get_page(page);
3139 
3140         count_vm_numa_event(NUMA_HINT_FAULTS);
3141         if (page_nid == numa_node_id()) {
3142                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
3143                 *flags |= TNF_FAULT_LOCAL;
3144         }
3145 
3146         return mpol_misplaced(page, vma, addr);
3147 }
3148 
3149 static int do_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
3150                    unsigned long addr, pte_t pte, pte_t *ptep, pmd_t *pmd)
3151 {
3152         struct page *page = NULL;
3153         spinlock_t *ptl;
3154         int page_nid = -1;
3155         int last_cpupid;
3156         int target_nid;
3157         bool migrated = false;
3158         bool was_writable = pte_write(pte);
3159         int flags = 0;
3160 
3161         /* A PROT_NONE fault should not end up here */
3162         BUG_ON(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)));
3163 
3164         /*
3165         * The "pte" at this point cannot be used safely without
3166         * validation through pte_unmap_same(). It's of NUMA type but
3167         * the pfn may be screwed if the read is non atomic.
3168         *
3169         * We can safely just do a "set_pte_at()", because the old
3170         * page table entry is not accessible, so there would be no
3171         * concurrent hardware modifications to the PTE.
3172         */
3173         ptl = pte_lockptr(mm, pmd);
3174         spin_lock(ptl);
3175         if (unlikely(!pte_same(*ptep, pte))) {
3176                 pte_unmap_unlock(ptep, ptl);
3177                 goto out;
3178         }
3179 
3180         /* Make it present again */
3181         pte = pte_modify(pte, vma->vm_page_prot);
3182         pte = pte_mkyoung(pte);
3183         if (was_writable)
3184                 pte = pte_mkwrite(pte);
3185         set_pte_at(mm, addr, ptep, pte);
3186         update_mmu_cache(vma, addr, ptep);
3187 
3188         page = vm_normal_page(vma, addr, pte);
3189         if (!page) {
3190                 pte_unmap_unlock(ptep, ptl);
3191                 return 0;
3192         }
3193 
3194         /*
3195          * Avoid grouping on RO pages in general. RO pages shouldn't hurt as
3196          * much anyway since they can be in shared cache state. This misses
3197          * the case where a mapping is writable but the process never writes
3198          * to it but pte_write gets cleared during protection updates and
3199          * pte_dirty has unpredictable behaviour between PTE scan updates,
3200          * background writeback, dirty balancing and application behaviour.
3201          */
3202         if (!(vma->vm_flags & VM_WRITE))
3203                 flags |= TNF_NO_GROUP;
3204 
3205         /*
3206          * Flag if the page is shared between multiple address spaces. This
3207          * is later used when determining whether to group tasks together
3208          */
3209         if (page_mapcount(page) > 1 && (vma->vm_flags & VM_SHARED))
3210                 flags |= TNF_SHARED;
3211 
3212         last_cpupid = page_cpupid_last(page);
3213         page_nid = page_to_nid(page);
3214         target_nid = numa_migrate_prep(page, vma, addr, page_nid, &flags);
3215         pte_unmap_unlock(ptep, ptl);
3216         if (target_nid == -1) {
3217                 put_page(page);
3218                 goto out;
3219         }
3220 
3221         /* Migrate to the requested node */
3222         migrated = migrate_misplaced_page(page, vma, target_nid);
3223         if (migrated) {
3224                 page_nid = target_nid;
3225                 flags |= TNF_MIGRATED;
3226         } else
3227                 flags |= TNF_MIGRATE_FAIL;
3228 
3229 out:
3230         if (page_nid != -1)
3231                 task_numa_fault(last_cpupid, page_nid, 1, flags);
3232         return 0;
3233 }
3234 
3235 static int create_huge_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
3236                         unsigned long address, pmd_t *pmd, unsigned int flags)
3237 {
3238         if (vma_is_anonymous(vma))
3239                 return do_huge_pmd_anonymous_page(mm, vma, address, pmd, flags);
3240         if (vma->vm_ops->pmd_fault)
3241                 return vma->vm_ops->pmd_fault(vma, address, pmd, flags);
3242         return VM_FAULT_FALLBACK;
3243 }
3244 
3245 static int wp_huge_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
3246                         unsigned long address, pmd_t *pmd, pmd_t orig_pmd,
3247                         unsigned int flags)
3248 {
3249         if (vma_is_anonymous(vma))
3250                 return do_huge_pmd_wp_page(mm, vma, address, pmd, orig_pmd);
3251         if (vma->vm_ops->pmd_fault)
3252                 return vma->vm_ops->pmd_fault(vma, address, pmd, flags);
3253         return VM_FAULT_FALLBACK;
3254 }
3255 
3256 /*
3257  * These routines also need to handle stuff like marking pages dirty
3258  * and/or accessed for architectures that don't do it in hardware (most
3259  * RISC architectures).  The early dirtying is also good on the i386.
3260  *
3261  * There is also a hook called "update_mmu_cache()" that architectures
3262  * with external mmu caches can use to update those (ie the Sparc or
3263  * PowerPC hashed page tables that act as extended TLBs).
3264  *
3265  * We enter with non-exclusive mmap_sem (to exclude vma changes,
3266  * but allow concurrent faults), and pte mapped but not yet locked.
3267  * We return with pte unmapped and unlocked.
3268  *
3269  * The mmap_sem may have been released depending on flags and our
3270  * return value.  See filemap_fault() and __lock_page_or_retry().
3271  */
3272 static int handle_pte_fault(struct mm_struct *mm,
3273                      struct vm_area_struct *vma, unsigned long address,
3274                      pte_t *pte, pmd_t *pmd, unsigned int flags)
3275 {
3276         pte_t entry;
3277         spinlock_t *ptl;
3278 
3279         /*
3280          * some architectures can have larger ptes than wordsize,
3281          * e.g.ppc44x-defconfig has CONFIG_PTE_64BIT=y and CONFIG_32BIT=y,
3282          * so READ_ONCE or ACCESS_ONCE cannot guarantee atomic accesses.
3283          * The code below just needs a consistent view for the ifs and
3284          * we later double check anyway with the ptl lock held. So here
3285          * a barrier will do.
3286          */
3287         entry = *pte;
3288         barrier();
3289         if (!pte_present(entry)) {
3290                 if (pte_none(entry)) {
3291                         if (vma_is_anonymous(vma))
3292                                 return do_anonymous_page(mm, vma, address,
3293                                                          pte, pmd, flags);
3294                         else
3295                                 return do_fault(mm, vma, address, pte, pmd,
3296                                                 flags, entry);
3297                 }
3298                 return do_swap_page(mm, vma, address,
3299                                         pte, pmd, flags, entry);
3300         }
3301 
3302         if (pte_protnone(entry))
3303                 return do_numa_page(mm, vma, address, entry, pte, pmd);
3304 
3305         ptl = pte_lockptr(mm, pmd);
3306         spin_lock(ptl);
3307         if (unlikely(!pte_same(*pte, entry)))
3308                 goto unlock;
3309         if (flags & FAULT_FLAG_WRITE) {
3310                 if (!pte_write(entry))
3311                         return do_wp_page(mm, vma, address,
3312                                         pte, pmd, ptl, entry);
3313                 entry = pte_mkdirty(entry);
3314         }
3315         entry = pte_mkyoung(entry);
3316         if (ptep_set_access_flags(vma, address, pte, entry, flags & FAULT_FLAG_WRITE)) {
3317                 update_mmu_cache(vma, address, pte);
3318         } else {
3319                 /*
3320                  * This is needed only for protection faults but the arch code
3321                  * is not yet telling us if this is a protection fault or not.
3322                  * This still avoids useless tlb flushes for .text page faults
3323                  * with threads.
3324                  */
3325                 if (flags & FAULT_FLAG_WRITE)
3326                         flush_tlb_fix_spurious_fault(vma, address);
3327         }
3328 unlock:
3329         pte_unmap_unlock(pte, ptl);
3330         return 0;
3331 }
3332 
3333 /*
3334  * By the time we get here, we already hold the mm semaphore
3335  *
3336  * The mmap_sem may have been released depending on flags and our
3337  * return value.  See filemap_fault() and __lock_page_or_retry().
3338  */
3339 static int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3340                              unsigned long address, unsigned int flags)
3341 {
3342         pgd_t *pgd;
3343         pud_t *pud;
3344         pmd_t *pmd;
3345         pte_t *pte;
3346 
3347         if (unlikely(is_vm_hugetlb_page(vma)))
3348                 return hugetlb_fault(mm, vma, address, flags);
3349 
3350         pgd = pgd_offset(mm, address);
3351         pud = pud_alloc(mm, pgd, address);
3352         if (!pud)
3353                 return VM_FAULT_OOM;
3354         pmd = pmd_alloc(mm, pud, address);
3355         if (!pmd)
3356                 return VM_FAULT_OOM;
3357         if (pmd_none(*pmd) && transparent_hugepage_enabled(vma)) {
3358                 int ret = create_huge_pmd(mm, vma, address, pmd, flags);
3359                 if (!(ret & VM_FAULT_FALLBACK))
3360                         return ret;
3361         } else {
3362                 pmd_t orig_pmd = *pmd;
3363                 int ret;
3364 
3365                 barrier();
3366                 if (pmd_trans_huge(orig_pmd)) {
3367                         unsigned int dirty = flags & FAULT_FLAG_WRITE;
3368 
3369                         /*
3370                          * If the pmd is splitting, return and retry the
3371                          * the fault.  Alternative: wait until the split
3372                          * is done, and goto retry.
3373                          */
3374                         if (pmd_trans_splitting(orig_pmd))
3375                                 return 0;
3376 
3377                         if (pmd_protnone(orig_pmd))
3378                                 return do_huge_pmd_numa_page(mm, vma, address,
3379                                                              orig_pmd, pmd);
3380 
3381                         if (dirty && !pmd_write(orig_pmd)) {
3382                                 ret = wp_huge_pmd(mm, vma, address, pmd,
3383                                                         orig_pmd, flags);
3384                                 if (!(ret & VM_FAULT_FALLBACK))
3385                                         return ret;
3386                         } else {
3387                                 huge_pmd_set_accessed(mm, vma, address, pmd,
3388                                                       orig_pmd, dirty);
3389                                 return 0;
3390                         }
3391                 }
3392         }
3393 
3394         /*
3395          * Use __pte_alloc instead of pte_alloc_map, because we can't
3396          * run pte_offset_map on the pmd, if an huge pmd could
3397          * materialize from under us from a different thread.
3398          */
3399         if (unlikely(pmd_none(*pmd)) &&
3400             unlikely(__pte_alloc(mm, vma, pmd, address)))
3401                 return VM_FAULT_OOM;
3402         /* if an huge pmd materialized from under us just retry later */
3403         if (unlikely(pmd_trans_huge(*pmd)))
3404                 return 0;
3405         /*
3406          * A regular pmd is established and it can't morph into a huge pmd
3407          * from under us anymore at this point because we hold the mmap_sem
3408          * read mode and khugepaged takes it in write mode. So now it's
3409          * safe to run pte_offset_map().
3410          */
3411         pte = pte_offset_map(pmd, address);
3412 
3413         return handle_pte_fault(mm, vma, address, pte, pmd, flags);
3414 }
3415 
3416 /*
3417  * By the time we get here, we already hold the mm semaphore
3418  *
3419  * The mmap_sem may have been released depending on flags and our
3420  * return value.  See filemap_fault() and __lock_page_or_retry().
3421  */
3422 int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3423                     unsigned long address, unsigned int flags)
3424 {
3425         int ret;
3426 
3427         __set_current_state(TASK_RUNNING);
3428 
3429         count_vm_event(PGFAULT);
3430         mem_cgroup_count_vm_event(mm, PGFAULT);
3431 
3432         /* do counter updates before entering really critical section. */
3433         check_sync_rss_stat(current);
3434 
3435         /*
3436          * Enable the memcg OOM handling for faults triggered in user
3437          * space.  Kernel faults are handled more gracefully.
3438          */
3439         if (flags & FAULT_FLAG_USER)
3440                 mem_cgroup_oom_enable();
3441 
3442         ret = __handle_mm_fault(mm, vma, address, flags);
3443 
3444         if (flags & FAULT_FLAG_USER) {
3445                 mem_cgroup_oom_disable();
3446                 /*
3447                  * The task may have entered a memcg OOM situation but
3448                  * if the allocation error was handled gracefully (no
3449                  * VM_FAULT_OOM), there is no need to kill anything.
3450                  * Just clean up the OOM state peacefully.
3451                  */
3452                 if (task_in_memcg_oom(current) && !(ret & VM_FAULT_OOM))
3453                         mem_cgroup_oom_synchronize(false);
3454         }
3455 
3456         return ret;
3457 }
3458 EXPORT_SYMBOL_GPL(handle_mm_fault);
3459 
3460 #ifndef __PAGETABLE_PUD_FOLDED
3461 /*
3462  * Allocate page upper directory.
3463  * We've already handled the fast-path in-line.
3464  */
3465 int __pud_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address)
3466 {
3467         pud_t *new = pud_alloc_one(mm, address);
3468         if (!new)
3469                 return -ENOMEM;
3470 
3471         smp_wmb(); /* See comment in __pte_alloc */
3472 
3473         spin_lock(&mm->page_table_lock);
3474         if (pgd_present(*pgd))          /* Another has populated it */
3475                 pud_free(mm, new);
3476         else
3477                 pgd_populate(mm, pgd, new);
3478         spin_unlock(&mm->page_table_lock);
3479         return 0;
3480 }
3481 #endif /* __PAGETABLE_PUD_FOLDED */
3482 
3483 #ifndef __PAGETABLE_PMD_FOLDED
3484 /*
3485  * Allocate page middle directory.
3486  * We've already handled the fast-path in-line.
3487  */
3488 int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address)
3489 {
3490         pmd_t *new = pmd_alloc_one(mm, address);
3491         if (!new)
3492                 return -ENOMEM;
3493 
3494         smp_wmb(); /* See comment in __pte_alloc */
3495 
3496         spin_lock(&mm->page_table_lock);
3497 #ifndef __ARCH_HAS_4LEVEL_HACK
3498         if (!pud_present(*pud)) {
3499                 mm_inc_nr_pmds(mm);
3500                 pud_populate(mm, pud, new);
3501         } else  /* Another has populated it */
3502                 pmd_free(mm, new);
3503 #else
3504         if (!pgd_present(*pud)) {
3505                 mm_inc_nr_pmds(mm);
3506                 pgd_populate(mm, pud, new);
3507         } else /* Another has populated it */
3508                 pmd_free(mm, new);
3509 #endif /* __ARCH_HAS_4LEVEL_HACK */
3510         spin_unlock(&mm->page_table_lock);
3511         return 0;
3512 }
3513 #endif /* __PAGETABLE_PMD_FOLDED */
3514 
3515 static int __follow_pte(struct mm_struct *mm, unsigned long address,
3516                 pte_t **ptepp, spinlock_t **ptlp)
3517 {
3518         pgd_t *pgd;
3519         pud_t *pud;
3520         pmd_t *pmd;
3521         pte_t *ptep;
3522 
3523         pgd = pgd_offset(mm, address);
3524         if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
3525                 goto out;
3526 
3527         pud = pud_offset(pgd, address);
3528         if (pud_none(*pud) || unlikely(pud_bad(*pud)))
3529                 goto out;
3530 
3531         pmd = pmd_offset(pud, address);
3532         VM_BUG_ON(pmd_trans_huge(*pmd));
3533         if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
3534                 goto out;
3535 
3536         /* We cannot handle huge page PFN maps. Luckily they don't exist. */
3537         if (pmd_huge(*pmd))
3538                 goto out;
3539 
3540         ptep = pte_offset_map_lock(mm, pmd, address, ptlp);
3541         if (!ptep)
3542                 goto out;
3543         if (!pte_present(*ptep))
3544                 goto unlock;
3545         *ptepp = ptep;
3546         return 0;
3547 unlock:
3548         pte_unmap_unlock(ptep, *ptlp);
3549 out:
3550         return -EINVAL;
3551 }
3552 
3553 static inline int follow_pte(struct mm_struct *mm, unsigned long address,
3554                              pte_t **ptepp, spinlock_t **ptlp)
3555 {
3556         int res;
3557 
3558         /* (void) is needed to make gcc happy */
3559         (void) __cond_lock(*ptlp,
3560                            !(res = __follow_pte(mm, address, ptepp, ptlp)));
3561         return res;
3562 }
3563 
3564 /**
3565  * follow_pfn - look up PFN at a user virtual address
3566  * @vma: memory mapping
3567  * @address: user virtual address
3568  * @pfn: location to store found PFN
3569  *
3570  * Only IO mappings and raw PFN mappings are allowed.
3571  *
3572  * Returns zero and the pfn at @pfn on success, -ve otherwise.
3573  */
3574 int follow_pfn(struct vm_area_struct *vma, unsigned long address,
3575         unsigned long *pfn)
3576 {
3577         int ret = -EINVAL;
3578         spinlock_t *ptl;
3579         pte_t *ptep;
3580 
3581         if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
3582                 return ret;
3583 
3584         ret = follow_pte(vma->vm_mm, address, &ptep, &ptl);
3585         if (ret)
3586                 return ret;
3587         *pfn = pte_pfn(*ptep);
3588         pte_unmap_unlock(ptep, ptl);
3589         return 0;
3590 }
3591 EXPORT_SYMBOL(follow_pfn);
3592 
3593 #ifdef CONFIG_HAVE_IOREMAP_PROT
3594 int follow_phys(struct vm_area_struct *vma,
3595                 unsigned long address, unsigned int flags,
3596                 unsigned long *prot, resource_size_t *phys)
3597 {
3598         int ret = -EINVAL;
3599         pte_t *ptep, pte;
3600         spinlock_t *ptl;
3601 
3602         if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
3603                 goto out;
3604 
3605         if (follow_pte(vma->vm_mm, address, &ptep, &ptl))
3606                 goto out;
3607         pte = *ptep;
3608 
3609         if ((flags & FOLL_WRITE) && !pte_write(pte))
3610                 goto unlock;
3611 
3612         *prot = pgprot_val(pte_pgprot(pte));
3613         *phys = (resource_size_t)pte_pfn(pte) << PAGE_SHIFT;
3614 
3615         ret = 0;
3616 unlock:
3617         pte_unmap_unlock(ptep, ptl);
3618 out:
3619         return ret;
3620 }
3621 
3622 int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
3623                         void *buf, int len, int write)
3624 {
3625         resource_size_t phys_addr;
3626         unsigned long prot = 0;
3627         void __iomem *maddr;
3628         int offset = addr & (PAGE_SIZE-1);
3629 
3630         if (follow_phys(vma, addr, write, &prot, &phys_addr))
3631                 return -EINVAL;
3632 
3633         maddr = ioremap_prot(phys_addr, PAGE_ALIGN(len + offset), prot);
3634         if (write)
3635                 memcpy_toio(maddr + offset, buf, len);
3636         else
3637                 memcpy_fromio(buf, maddr + offset, len);
3638         iounmap(maddr);
3639 
3640         return len;
3641 }
3642 EXPORT_SYMBOL_GPL(generic_access_phys);
3643 #endif
3644 
3645 /*
3646  * Access another process' address space as given in mm.  If non-NULL, use the
3647  * given task for page fault accounting.
3648  */
3649 static int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
3650                 unsigned long addr, void *buf, int len, int write)
3651 {
3652         struct vm_area_struct *vma;
3653         void *old_buf = buf;
3654 
3655         down_read(&mm->mmap_sem);
3656         /* ignore errors, just check how much was successfully transferred */
3657         while (len) {
3658                 int bytes, ret, offset;
3659                 void *maddr;
3660                 struct page *page = NULL;
3661 
3662                 ret = get_user_pages(tsk, mm, addr, 1,
3663                                 write, 1, &page, &vma);
3664                 if (ret <= 0) {
3665 #ifndef CONFIG_HAVE_IOREMAP_PROT
3666                         break;
3667 #else
3668                         /*
3669                          * Check if this is a VM_IO | VM_PFNMAP VMA, which
3670                          * we can access using slightly different code.
3671                          */
3672                         vma = find_vma(mm, addr);
3673                         if (!vma || vma->vm_start > addr)
3674                                 break;
3675                         if (vma->vm_ops && vma->vm_ops->access)
3676                                 ret = vma->vm_ops->access(vma, addr, buf,
3677                                                           len, write);
3678                         if (ret <= 0)
3679                                 break;
3680                         bytes = ret;
3681 #endif
3682                 } else {
3683                         bytes = len;
3684                         offset = addr & (PAGE_SIZE-1);
3685                         if (bytes > PAGE_SIZE-offset)
3686                                 bytes = PAGE_SIZE-offset;
3687 
3688                         maddr = kmap(page);
3689                         if (write) {
3690                                 copy_to_user_page(vma, page, addr,
3691                                                   maddr + offset, buf, bytes);
3692                                 set_page_dirty_lock(page);
3693                         } else {
3694                                 copy_from_user_page(vma, page, addr,
3695                                                     buf, maddr + offset, bytes);
3696                         }
3697                         kunmap(page);
3698                         page_cache_release(page);
3699                 }
3700                 len -= bytes;
3701                 buf += bytes;
3702                 addr += bytes;
3703         }
3704         up_read(&mm->mmap_sem);
3705 
3706         return buf - old_buf;
3707 }
3708 
3709 /**
3710  * access_remote_vm - access another process' address space
3711  * @mm:         the mm_struct of the target address space
3712  * @addr:       start address to access
3713  * @buf:        source or destination buffer
3714  * @len:        number of bytes to transfer
3715  * @write:      whether the access is a write
3716  *
3717  * The caller must hold a reference on @mm.
3718  */
3719 int access_remote_vm(struct mm_struct *mm, unsigned long addr,
3720                 void *buf, int len, int write)
3721 {
3722         return __access_remote_vm(NULL, mm, addr, buf, len, write);
3723 }
3724 
3725 /*
3726  * Access another process' address space.
3727  * Source/target buffer must be kernel space,
3728  * Do not walk the page table directly, use get_user_pages
3729  */
3730 int access_process_vm(struct task_struct *tsk, unsigned long addr,
3731                 void *buf, int len, int write)
3732 {
3733         struct mm_struct *mm;
3734         int ret;
3735 
3736         mm = get_task_mm(tsk);
3737         if (!mm)
3738                 return 0;
3739 
3740         ret = __access_remote_vm(tsk, mm, addr, buf, len, write);
3741         mmput(mm);
3742 
3743         return ret;
3744 }
3745 
3746 /*
3747  * Print the name of a VMA.
3748  */
3749 void print_vma_addr(char *prefix, unsigned long ip)
3750 {
3751         struct mm_struct *mm = current->mm;
3752         struct vm_area_struct *vma;
3753 
3754         /*
3755          * Do not print if we are in atomic
3756          * contexts (in exception stacks, etc.):
3757          */
3758         if (preempt_count())
3759                 return;
3760 
3761         down_read(&mm->mmap_sem);
3762         vma = find_vma(mm, ip);
3763         if (vma && vma->vm_file) {
3764                 struct file *f = vma->vm_file;
3765                 char *buf = (char *)__get_free_page(GFP_KERNEL);
3766                 if (buf) {
3767                         char *p;
3768 
3769                         p = file_path(f, buf, PAGE_SIZE);
3770                         if (IS_ERR(p))
3771                                 p = "?";
3772                         printk("%s%s[%lx+%lx]", prefix, kbasename(p),
3773                                         vma->vm_start,
3774                                         vma->vm_end - vma->vm_start);
3775                         free_page((unsigned long)buf);
3776                 }
3777         }
3778         up_read(&mm->mmap_sem);
3779 }
3780 
3781 #if defined(CONFIG_PROVE_LOCKING) || defined(CONFIG_DEBUG_ATOMIC_SLEEP)
3782 void __might_fault(const char *file, int line)
3783 {
3784         /*
3785          * Some code (nfs/sunrpc) uses socket ops on kernel memory while
3786          * holding the mmap_sem, this is safe because kernel memory doesn't
3787          * get paged out, therefore we'll never actually fault, and the
3788          * below annotations will generate false positives.
3789          */
3790         if (segment_eq(get_fs(), KERNEL_DS))
3791                 return;
3792         if (pagefault_disabled())
3793                 return;
3794         __might_sleep(file, line, 0);
3795 #if defined(CONFIG_DEBUG_ATOMIC_SLEEP)
3796         if (current->mm)
3797                 might_lock_read(&current->mm->mmap_sem);
3798 #endif
3799 }
3800 EXPORT_SYMBOL(__might_fault);
3801 #endif
3802 
3803 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HUGETLBFS)
3804 static void clear_gigantic_page(struct page *page,
3805                                 unsigned long addr,
3806                                 unsigned int pages_per_huge_page)
3807 {
3808         int i;
3809         struct page *p = page;
3810 
3811         might_sleep();
3812         for (i = 0; i < pages_per_huge_page;
3813              i++, p = mem_map_next(p, page, i)) {
3814                 cond_resched();
3815                 clear_user_highpage(p, addr + i * PAGE_SIZE);
3816         }
3817 }
3818 void clear_huge_page(struct page *page,
3819                      unsigned long addr, unsigned int pages_per_huge_page)
3820 {
3821         int i;
3822 
3823         if (unlikely(pages_per_huge_page > MAX_ORDER_NR_PAGES)) {
3824                 clear_gigantic_page(page, addr, pages_per_huge_page);
3825                 return;
3826         }
3827 
3828         might_sleep();
3829         for (i = 0; i < pages_per_huge_page; i++) {
3830                 cond_resched();
3831                 clear_user_highpage(page + i, addr + i * PAGE_SIZE);
3832         }
3833 }
3834 
3835 static void copy_user_gigantic_page(struct page *dst, struct page *src,
3836                                     unsigned long addr,
3837                                     struct vm_area_struct *vma,
3838                                     unsigned int pages_per_huge_page)
3839 {
3840         int i;
3841         struct page *dst_base = dst;
3842         struct page *src_base = src;
3843 
3844         for (i = 0; i < pages_per_huge_page; ) {
3845                 cond_resched();
3846                 copy_user_highpage(dst, src, addr + i*PAGE_SIZE, vma);
3847 
3848                 i++;
3849                 dst = mem_map_next(dst, dst_base, i);
3850                 src = mem_map_next(src, src_base, i);
3851         }
3852 }
3853 
3854 void copy_user_huge_page(struct page *dst, struct page *src,
3855                          unsigned long addr, struct vm_area_struct *vma,
3856                          unsigned int pages_per_huge_page)
3857 {
3858         int i;
3859 
3860         if (unlikely(pages_per_huge_page > MAX_ORDER_NR_PAGES)) {
3861                 copy_user_gigantic_page(dst, src, addr, vma,
3862                                         pages_per_huge_page);
3863                 return;
3864         }
3865 
3866         might_sleep();
3867         for (i = 0; i < pages_per_huge_page; i++) {
3868                 cond_resched();
3869                 copy_user_highpage(dst + i, src + i, addr + i*PAGE_SIZE, vma);
3870         }
3871 }
3872 #endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */
3873 
3874 #if USE_SPLIT_PTE_PTLOCKS && ALLOC_SPLIT_PTLOCKS
3875 
3876 static struct kmem_cache *page_ptl_cachep;
3877 
3878 void __init ptlock_cache_init(void)
3879 {
3880         page_ptl_cachep = kmem_cache_create("page->ptl", sizeof(spinlock_t), 0,
3881                         SLAB_PANIC, NULL);
3882 }
3883 
3884 bool ptlock_alloc(struct page *page)
3885 {
3886         spinlock_t *ptl;
3887 
3888         ptl = kmem_cache_alloc(page_ptl_cachep, GFP_KERNEL);
3889         if (!ptl)
3890                 return false;
3891         page->ptl = ptl;
3892         return true;
3893 }
3894 
3895 void ptlock_free(struct page *page)
3896 {
3897         kmem_cache_free(page_ptl_cachep, page->ptl);
3898 }
3899 #endif
3900 

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