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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/pfn_t.h>
 54 #include <linux/writeback.h>
 55 #include <linux/memcontrol.h>
 56 #include <linux/mmu_notifier.h>
 57 #include <linux/kallsyms.h>
 58 #include <linux/swapops.h>
 59 #include <linux/elf.h>
 60 #include <linux/gfp.h>
 61 #include <linux/migrate.h>
 62 #include <linux/string.h>
 63 #include <linux/dma-debug.h>
 64 #include <linux/debugfs.h>
 65 #include <linux/userfaultfd_k.h>
 66 
 67 #include <asm/io.h>
 68 #include <asm/mmu_context.h>
 69 #include <asm/pgalloc.h>
 70 #include <asm/uaccess.h>
 71 #include <asm/tlb.h>
 72 #include <asm/tlbflush.h>
 73 #include <asm/pgtable.h>
 74 
 75 #include "internal.h"
 76 
 77 #ifdef LAST_CPUPID_NOT_IN_PAGE_FLAGS
 78 #warning Unfortunate NUMA and NUMA Balancing config, growing page-frame for last_cpupid.
 79 #endif
 80 
 81 #ifndef CONFIG_NEED_MULTIPLE_NODES
 82 /* use the per-pgdat data instead for discontigmem - mbligh */
 83 unsigned long max_mapnr;
 84 struct page *mem_map;
 85 
 86 EXPORT_SYMBOL(max_mapnr);
 87 EXPORT_SYMBOL(mem_map);
 88 #endif
 89 
 90 /*
 91  * A number of key systems in x86 including ioremap() rely on the assumption
 92  * that high_memory defines the upper bound on direct map memory, then end
 93  * of ZONE_NORMAL.  Under CONFIG_DISCONTIG this means that max_low_pfn and
 94  * highstart_pfn must be the same; there must be no gap between ZONE_NORMAL
 95  * and ZONE_HIGHMEM.
 96  */
 97 void * high_memory;
 98 
 99 EXPORT_SYMBOL(high_memory);
100 
101 /*
102  * Randomize the address space (stacks, mmaps, brk, etc.).
103  *
104  * ( When CONFIG_COMPAT_BRK=y we exclude brk from randomization,
105  *   as ancient (libc5 based) binaries can segfault. )
106  */
107 int randomize_va_space __read_mostly =
108 #ifdef CONFIG_COMPAT_BRK
109                                         1;
110 #else
111                                         2;
112 #endif
113 
114 static int __init disable_randmaps(char *s)
115 {
116         randomize_va_space = 0;
117         return 1;
118 }
119 __setup("norandmaps", disable_randmaps);
120 
121 unsigned long zero_pfn __read_mostly;
122 unsigned long highest_memmap_pfn __read_mostly;
123 
124 EXPORT_SYMBOL(zero_pfn);
125 
126 /*
127  * CONFIG_MMU architectures set up ZERO_PAGE in their paging_init()
128  */
129 static int __init init_zero_pfn(void)
130 {
131         zero_pfn = page_to_pfn(ZERO_PAGE(0));
132         return 0;
133 }
134 core_initcall(init_zero_pfn);
135 
136 
137 #if defined(SPLIT_RSS_COUNTING)
138 
139 void sync_mm_rss(struct mm_struct *mm)
140 {
141         int i;
142 
143         for (i = 0; i < NR_MM_COUNTERS; i++) {
144                 if (current->rss_stat.count[i]) {
145                         add_mm_counter(mm, i, current->rss_stat.count[i]);
146                         current->rss_stat.count[i] = 0;
147                 }
148         }
149         current->rss_stat.events = 0;
150 }
151 
152 static void add_mm_counter_fast(struct mm_struct *mm, int member, int val)
153 {
154         struct task_struct *task = current;
155 
156         if (likely(task->mm == mm))
157                 task->rss_stat.count[member] += val;
158         else
159                 add_mm_counter(mm, member, val);
160 }
161 #define inc_mm_counter_fast(mm, member) add_mm_counter_fast(mm, member, 1)
162 #define dec_mm_counter_fast(mm, member) add_mm_counter_fast(mm, member, -1)
163 
164 /* sync counter once per 64 page faults */
165 #define TASK_RSS_EVENTS_THRESH  (64)
166 static void check_sync_rss_stat(struct task_struct *task)
167 {
168         if (unlikely(task != current))
169                 return;
170         if (unlikely(task->rss_stat.events++ > TASK_RSS_EVENTS_THRESH))
171                 sync_mm_rss(task->mm);
172 }
173 #else /* SPLIT_RSS_COUNTING */
174 
175 #define inc_mm_counter_fast(mm, member) inc_mm_counter(mm, member)
176 #define dec_mm_counter_fast(mm, member) dec_mm_counter(mm, member)
177 
178 static void check_sync_rss_stat(struct task_struct *task)
179 {
180 }
181 
182 #endif /* SPLIT_RSS_COUNTING */
183 
184 #ifdef HAVE_GENERIC_MMU_GATHER
185 
186 static bool tlb_next_batch(struct mmu_gather *tlb)
187 {
188         struct mmu_gather_batch *batch;
189 
190         batch = tlb->active;
191         if (batch->next) {
192                 tlb->active = batch->next;
193                 return true;
194         }
195 
196         if (tlb->batch_count == MAX_GATHER_BATCH_COUNT)
197                 return false;
198 
199         batch = (void *)__get_free_pages(GFP_NOWAIT | __GFP_NOWARN, 0);
200         if (!batch)
201                 return false;
202 
203         tlb->batch_count++;
204         batch->next = NULL;
205         batch->nr   = 0;
206         batch->max  = MAX_GATHER_BATCH;
207 
208         tlb->active->next = batch;
209         tlb->active = batch;
210 
211         return true;
212 }
213 
214 /* tlb_gather_mmu
215  *      Called to initialize an (on-stack) mmu_gather structure for page-table
216  *      tear-down from @mm. The @fullmm argument is used when @mm is without
217  *      users and we're going to destroy the full address space (exit/execve).
218  */
219 void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, unsigned long start, unsigned long end)
220 {
221         tlb->mm = mm;
222 
223         /* Is it from 0 to ~0? */
224         tlb->fullmm     = !(start | (end+1));
225         tlb->need_flush_all = 0;
226         tlb->local.next = NULL;
227         tlb->local.nr   = 0;
228         tlb->local.max  = ARRAY_SIZE(tlb->__pages);
229         tlb->active     = &tlb->local;
230         tlb->batch_count = 0;
231 
232 #ifdef CONFIG_HAVE_RCU_TABLE_FREE
233         tlb->batch = NULL;
234 #endif
235 
236         __tlb_reset_range(tlb);
237 }
238 
239 static void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb)
240 {
241         if (!tlb->end)
242                 return;
243 
244         tlb_flush(tlb);
245         mmu_notifier_invalidate_range(tlb->mm, tlb->start, tlb->end);
246 #ifdef CONFIG_HAVE_RCU_TABLE_FREE
247         tlb_table_flush(tlb);
248 #endif
249         __tlb_reset_range(tlb);
250 }
251 
252 static void tlb_flush_mmu_free(struct mmu_gather *tlb)
253 {
254         struct mmu_gather_batch *batch;
255 
256         for (batch = &tlb->local; batch && batch->nr; batch = batch->next) {
257                 free_pages_and_swap_cache(batch->pages, batch->nr);
258                 batch->nr = 0;
259         }
260         tlb->active = &tlb->local;
261 }
262 
263 void tlb_flush_mmu(struct mmu_gather *tlb)
264 {
265         tlb_flush_mmu_tlbonly(tlb);
266         tlb_flush_mmu_free(tlb);
267 }
268 
269 /* tlb_finish_mmu
270  *      Called at the end of the shootdown operation to free up any resources
271  *      that were required.
272  */
273 void tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
274 {
275         struct mmu_gather_batch *batch, *next;
276 
277         tlb_flush_mmu(tlb);
278 
279         /* keep the page table cache within bounds */
280         check_pgt_cache();
281 
282         for (batch = tlb->local.next; batch; batch = next) {
283                 next = batch->next;
284                 free_pages((unsigned long)batch, 0);
285         }
286         tlb->local.next = NULL;
287 }
288 
289 /* __tlb_remove_page
290  *      Must perform the equivalent to __free_pte(pte_get_and_clear(ptep)), while
291  *      handling the additional races in SMP caused by other CPUs caching valid
292  *      mappings in their TLBs. Returns the number of free page slots left.
293  *      When out of page slots we must call tlb_flush_mmu().
294  */
295 int __tlb_remove_page(struct mmu_gather *tlb, struct page *page)
296 {
297         struct mmu_gather_batch *batch;
298 
299         VM_BUG_ON(!tlb->end);
300 
301         batch = tlb->active;
302         batch->pages[batch->nr++] = page;
303         if (batch->nr == batch->max) {
304                 if (!tlb_next_batch(tlb))
305                         return 0;
306                 batch = tlb->active;
307         }
308         VM_BUG_ON_PAGE(batch->nr > batch->max, page);
309 
310         return batch->max - batch->nr;
311 }
312 
313 #endif /* HAVE_GENERIC_MMU_GATHER */
314 
315 #ifdef CONFIG_HAVE_RCU_TABLE_FREE
316 
317 /*
318  * See the comment near struct mmu_table_batch.
319  */
320 
321 static void tlb_remove_table_smp_sync(void *arg)
322 {
323         /* Simply deliver the interrupt */
324 }
325 
326 static void tlb_remove_table_one(void *table)
327 {
328         /*
329          * This isn't an RCU grace period and hence the page-tables cannot be
330          * assumed to be actually RCU-freed.
331          *
332          * It is however sufficient for software page-table walkers that rely on
333          * IRQ disabling. See the comment near struct mmu_table_batch.
334          */
335         smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
336         __tlb_remove_table(table);
337 }
338 
339 static void tlb_remove_table_rcu(struct rcu_head *head)
340 {
341         struct mmu_table_batch *batch;
342         int i;
343 
344         batch = container_of(head, struct mmu_table_batch, rcu);
345 
346         for (i = 0; i < batch->nr; i++)
347                 __tlb_remove_table(batch->tables[i]);
348 
349         free_page((unsigned long)batch);
350 }
351 
352 void tlb_table_flush(struct mmu_gather *tlb)
353 {
354         struct mmu_table_batch **batch = &tlb->batch;
355 
356         if (*batch) {
357                 call_rcu_sched(&(*batch)->rcu, tlb_remove_table_rcu);
358                 *batch = NULL;
359         }
360 }
361 
362 void tlb_remove_table(struct mmu_gather *tlb, void *table)
363 {
364         struct mmu_table_batch **batch = &tlb->batch;
365 
366         /*
367          * When there's less then two users of this mm there cannot be a
368          * concurrent page-table walk.
369          */
370         if (atomic_read(&tlb->mm->mm_users) < 2) {
371                 __tlb_remove_table(table);
372                 return;
373         }
374 
375         if (*batch == NULL) {
376                 *batch = (struct mmu_table_batch *)__get_free_page(GFP_NOWAIT | __GFP_NOWARN);
377                 if (*batch == NULL) {
378                         tlb_remove_table_one(table);
379                         return;
380                 }
381                 (*batch)->nr = 0;
382         }
383         (*batch)->tables[(*batch)->nr++] = table;
384         if ((*batch)->nr == MAX_TABLE_BATCH)
385                 tlb_table_flush(tlb);
386 }
387 
388 #endif /* CONFIG_HAVE_RCU_TABLE_FREE */
389 
390 /*
391  * Note: this doesn't free the actual pages themselves. That
392  * has been handled earlier when unmapping all the memory regions.
393  */
394 static void free_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
395                            unsigned long addr)
396 {
397         pgtable_t token = pmd_pgtable(*pmd);
398         pmd_clear(pmd);
399         pte_free_tlb(tlb, token, addr);
400         atomic_long_dec(&tlb->mm->nr_ptes);
401 }
402 
403 static inline void free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
404                                 unsigned long addr, unsigned long end,
405                                 unsigned long floor, unsigned long ceiling)
406 {
407         pmd_t *pmd;
408         unsigned long next;
409         unsigned long start;
410 
411         start = addr;
412         pmd = pmd_offset(pud, addr);
413         do {
414                 next = pmd_addr_end(addr, end);
415                 if (pmd_none_or_clear_bad(pmd))
416                         continue;
417                 free_pte_range(tlb, pmd, addr);
418         } while (pmd++, addr = next, addr != end);
419 
420         start &= PUD_MASK;
421         if (start < floor)
422                 return;
423         if (ceiling) {
424                 ceiling &= PUD_MASK;
425                 if (!ceiling)
426                         return;
427         }
428         if (end - 1 > ceiling - 1)
429                 return;
430 
431         pmd = pmd_offset(pud, start);
432         pud_clear(pud);
433         pmd_free_tlb(tlb, pmd, start);
434         mm_dec_nr_pmds(tlb->mm);
435 }
436 
437 static inline void free_pud_range(struct mmu_gather *tlb, pgd_t *pgd,
438                                 unsigned long addr, unsigned long end,
439                                 unsigned long floor, unsigned long ceiling)
440 {
441         pud_t *pud;
442         unsigned long next;
443         unsigned long start;
444 
445         start = addr;
446         pud = pud_offset(pgd, addr);
447         do {
448                 next = pud_addr_end(addr, end);
449                 if (pud_none_or_clear_bad(pud))
450                         continue;
451                 free_pmd_range(tlb, pud, addr, next, floor, ceiling);
452         } while (pud++, addr = next, addr != end);
453 
454         start &= PGDIR_MASK;
455         if (start < floor)
456                 return;
457         if (ceiling) {
458                 ceiling &= PGDIR_MASK;
459                 if (!ceiling)
460                         return;
461         }
462         if (end - 1 > ceiling - 1)
463                 return;
464 
465         pud = pud_offset(pgd, start);
466         pgd_clear(pgd);
467         pud_free_tlb(tlb, pud, start);
468 }
469 
470 /*
471  * This function frees user-level page tables of a process.
472  */
473 void free_pgd_range(struct mmu_gather *tlb,
474                         unsigned long addr, unsigned long end,
475                         unsigned long floor, unsigned long ceiling)
476 {
477         pgd_t *pgd;
478         unsigned long next;
479 
480         /*
481          * The next few lines have given us lots of grief...
482          *
483          * Why are we testing PMD* at this top level?  Because often
484          * there will be no work to do at all, and we'd prefer not to
485          * go all the way down to the bottom just to discover that.
486          *
487          * Why all these "- 1"s?  Because 0 represents both the bottom
488          * of the address space and the top of it (using -1 for the
489          * top wouldn't help much: the masks would do the wrong thing).
490          * The rule is that addr 0 and floor 0 refer to the bottom of
491          * the address space, but end 0 and ceiling 0 refer to the top
492          * Comparisons need to use "end - 1" and "ceiling - 1" (though
493          * that end 0 case should be mythical).
494          *
495          * Wherever addr is brought up or ceiling brought down, we must
496          * be careful to reject "the opposite 0" before it confuses the
497          * subsequent tests.  But what about where end is brought down
498          * by PMD_SIZE below? no, end can't go down to 0 there.
499          *
500          * Whereas we round start (addr) and ceiling down, by different
501          * masks at different levels, in order to test whether a table
502          * now has no other vmas using it, so can be freed, we don't
503          * bother to round floor or end up - the tests don't need that.
504          */
505 
506         addr &= PMD_MASK;
507         if (addr < floor) {
508                 addr += PMD_SIZE;
509                 if (!addr)
510                         return;
511         }
512         if (ceiling) {
513                 ceiling &= PMD_MASK;
514                 if (!ceiling)
515                         return;
516         }
517         if (end - 1 > ceiling - 1)
518                 end -= PMD_SIZE;
519         if (addr > end - 1)
520                 return;
521 
522         pgd = pgd_offset(tlb->mm, addr);
523         do {
524                 next = pgd_addr_end(addr, end);
525                 if (pgd_none_or_clear_bad(pgd))
526                         continue;
527                 free_pud_range(tlb, pgd, addr, next, floor, ceiling);
528         } while (pgd++, addr = next, addr != end);
529 }
530 
531 void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *vma,
532                 unsigned long floor, unsigned long ceiling)
533 {
534         while (vma) {
535                 struct vm_area_struct *next = vma->vm_next;
536                 unsigned long addr = vma->vm_start;
537 
538                 /*
539                  * Hide vma from rmap and truncate_pagecache before freeing
540                  * pgtables
541                  */
542                 unlink_anon_vmas(vma);
543                 unlink_file_vma(vma);
544 
545                 if (is_vm_hugetlb_page(vma)) {
546                         hugetlb_free_pgd_range(tlb, addr, vma->vm_end,
547                                 floor, next? next->vm_start: ceiling);
548                 } else {
549                         /*
550                          * Optimization: gather nearby vmas into one call down
551                          */
552                         while (next && next->vm_start <= vma->vm_end + PMD_SIZE
553                                && !is_vm_hugetlb_page(next)) {
554                                 vma = next;
555                                 next = vma->vm_next;
556                                 unlink_anon_vmas(vma);
557                                 unlink_file_vma(vma);
558                         }
559                         free_pgd_range(tlb, addr, vma->vm_end,
560                                 floor, next? next->vm_start: ceiling);
561                 }
562                 vma = next;
563         }
564 }
565 
566 int __pte_alloc(struct mm_struct *mm, pmd_t *pmd, unsigned long address)
567 {
568         spinlock_t *ptl;
569         pgtable_t new = pte_alloc_one(mm, address);
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         if (likely(pmd_none(*pmd))) {   /* Has another populated it ? */
590                 atomic_long_inc(&mm->nr_ptes);
591                 pmd_populate(mm, pmd, new);
592                 new = NULL;
593         }
594         spin_unlock(ptl);
595         if (new)
596                 pte_free(mm, new);
597         return 0;
598 }
599 
600 int __pte_alloc_kernel(pmd_t *pmd, unsigned long address)
601 {
602         pte_t *new = pte_alloc_one_kernel(&init_mm, address);
603         if (!new)
604                 return -ENOMEM;
605 
606         smp_wmb(); /* See comment in __pte_alloc */
607 
608         spin_lock(&init_mm.page_table_lock);
609         if (likely(pmd_none(*pmd))) {   /* Has another populated it ? */
610                 pmd_populate_kernel(&init_mm, pmd, new);
611                 new = NULL;
612         }
613         spin_unlock(&init_mm.page_table_lock);
614         if (new)
615                 pte_free_kernel(&init_mm, new);
616         return 0;
617 }
618 
619 static inline void init_rss_vec(int *rss)
620 {
621         memset(rss, 0, sizeof(int) * NR_MM_COUNTERS);
622 }
623 
624 static inline void add_mm_rss_vec(struct mm_struct *mm, int *rss)
625 {
626         int i;
627 
628         if (current->mm == mm)
629                 sync_mm_rss(mm);
630         for (i = 0; i < NR_MM_COUNTERS; i++)
631                 if (rss[i])
632                         add_mm_counter(mm, i, rss[i]);
633 }
634 
635 /*
636  * This function is called to print an error when a bad pte
637  * is found. For example, we might have a PFN-mapped pte in
638  * a region that doesn't allow it.
639  *
640  * The calling function must still handle the error.
641  */
642 static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
643                           pte_t pte, struct page *page)
644 {
645         pgd_t *pgd = pgd_offset(vma->vm_mm, addr);
646         pud_t *pud = pud_offset(pgd, addr);
647         pmd_t *pmd = pmd_offset(pud, addr);
648         struct address_space *mapping;
649         pgoff_t index;
650         static unsigned long resume;
651         static unsigned long nr_shown;
652         static unsigned long nr_unshown;
653 
654         /*
655          * Allow a burst of 60 reports, then keep quiet for that minute;
656          * or allow a steady drip of one report per second.
657          */
658         if (nr_shown == 60) {
659                 if (time_before(jiffies, resume)) {
660                         nr_unshown++;
661                         return;
662                 }
663                 if (nr_unshown) {
664                         pr_alert("BUG: Bad page map: %lu messages suppressed\n",
665                                  nr_unshown);
666                         nr_unshown = 0;
667                 }
668                 nr_shown = 0;
669         }
670         if (nr_shown++ == 0)
671                 resume = jiffies + 60 * HZ;
672 
673         mapping = vma->vm_file ? vma->vm_file->f_mapping : NULL;
674         index = linear_page_index(vma, addr);
675 
676         pr_alert("BUG: Bad page map in process %s  pte:%08llx pmd:%08llx\n",
677                  current->comm,
678                  (long long)pte_val(pte), (long long)pmd_val(*pmd));
679         if (page)
680                 dump_page(page, "bad pte");
681         pr_alert("addr:%p vm_flags:%08lx anon_vma:%p mapping:%p index:%lx\n",
682                  (void *)addr, vma->vm_flags, vma->anon_vma, mapping, index);
683         /*
684          * Choose text because data symbols depend on CONFIG_KALLSYMS_ALL=y
685          */
686         pr_alert("file:%pD fault:%pf mmap:%pf readpage:%pf\n",
687                  vma->vm_file,
688                  vma->vm_ops ? vma->vm_ops->fault : NULL,
689                  vma->vm_file ? vma->vm_file->f_op->mmap : NULL,
690                  mapping ? mapping->a_ops->readpage : NULL);
691         dump_stack();
692         add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
693 }
694 
695 /*
696  * vm_normal_page -- This function gets the "struct page" associated with a pte.
697  *
698  * "Special" mappings do not wish to be associated with a "struct page" (either
699  * it doesn't exist, or it exists but they don't want to touch it). In this
700  * case, NULL is returned here. "Normal" mappings do have a struct page.
701  *
702  * There are 2 broad cases. Firstly, an architecture may define a pte_special()
703  * pte bit, in which case this function is trivial. Secondly, an architecture
704  * may not have a spare pte bit, which requires a more complicated scheme,
705  * described below.
706  *
707  * A raw VM_PFNMAP mapping (ie. one that is not COWed) is always considered a
708  * special mapping (even if there are underlying and valid "struct pages").
709  * COWed pages of a VM_PFNMAP are always normal.
710  *
711  * The way we recognize COWed pages within VM_PFNMAP mappings is through the
712  * rules set up by "remap_pfn_range()": the vma will have the VM_PFNMAP bit
713  * set, and the vm_pgoff will point to the first PFN mapped: thus every special
714  * mapping will always honor the rule
715  *
716  *      pfn_of_page == vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT)
717  *
718  * And for normal mappings this is false.
719  *
720  * This restricts such mappings to be a linear translation from virtual address
721  * to pfn. To get around this restriction, we allow arbitrary mappings so long
722  * as the vma is not a COW mapping; in that case, we know that all ptes are
723  * special (because none can have been COWed).
724  *
725  *
726  * In order to support COW of arbitrary special mappings, we have VM_MIXEDMAP.
727  *
728  * VM_MIXEDMAP mappings can likewise contain memory with or without "struct
729  * page" backing, however the difference is that _all_ pages with a struct
730  * page (that is, those where pfn_valid is true) are refcounted and considered
731  * normal pages by the VM. The disadvantage is that pages are refcounted
732  * (which can be slower and simply not an option for some PFNMAP users). The
733  * advantage is that we don't have to follow the strict linearity rule of
734  * PFNMAP mappings in order to support COWable mappings.
735  *
736  */
737 #ifdef __HAVE_ARCH_PTE_SPECIAL
738 # define HAVE_PTE_SPECIAL 1
739 #else
740 # define HAVE_PTE_SPECIAL 0
741 #endif
742 struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
743                                 pte_t pte)
744 {
745         unsigned long pfn = pte_pfn(pte);
746 
747         if (HAVE_PTE_SPECIAL) {
748                 if (likely(!pte_special(pte)))
749                         goto check_pfn;
750                 if (vma->vm_ops && vma->vm_ops->find_special_page)
751                         return vma->vm_ops->find_special_page(vma, addr);
752                 if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
753                         return NULL;
754                 if (!is_zero_pfn(pfn))
755                         print_bad_pte(vma, addr, pte, NULL);
756                 return NULL;
757         }
758 
759         /* !HAVE_PTE_SPECIAL case follows: */
760 
761         if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
762                 if (vma->vm_flags & VM_MIXEDMAP) {
763                         if (!pfn_valid(pfn))
764                                 return NULL;
765                         goto out;
766                 } else {
767                         unsigned long off;
768                         off = (addr - vma->vm_start) >> PAGE_SHIFT;
769                         if (pfn == vma->vm_pgoff + off)
770                                 return NULL;
771                         if (!is_cow_mapping(vma->vm_flags))
772                                 return NULL;
773                 }
774         }
775 
776         if (is_zero_pfn(pfn))
777                 return NULL;
778 check_pfn:
779         if (unlikely(pfn > highest_memmap_pfn)) {
780                 print_bad_pte(vma, addr, pte, NULL);
781                 return NULL;
782         }
783 
784         /*
785          * NOTE! We still have PageReserved() pages in the page tables.
786          * eg. VDSO mappings can cause them to exist.
787          */
788 out:
789         return pfn_to_page(pfn);
790 }
791 
792 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
793 struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,
794                                 pmd_t pmd)
795 {
796         unsigned long pfn = pmd_pfn(pmd);
797 
798         /*
799          * There is no pmd_special() but there may be special pmds, e.g.
800          * in a direct-access (dax) mapping, so let's just replicate the
801          * !HAVE_PTE_SPECIAL case from vm_normal_page() here.
802          */
803         if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
804                 if (vma->vm_flags & VM_MIXEDMAP) {
805                         if (!pfn_valid(pfn))
806                                 return NULL;
807                         goto out;
808                 } else {
809                         unsigned long off;
810                         off = (addr - vma->vm_start) >> PAGE_SHIFT;
811                         if (pfn == vma->vm_pgoff + off)
812                                 return NULL;
813                         if (!is_cow_mapping(vma->vm_flags))
814                                 return NULL;
815                 }
816         }
817 
818         if (is_zero_pfn(pfn))
819                 return NULL;
820         if (unlikely(pfn > highest_memmap_pfn))
821                 return NULL;
822 
823         /*
824          * NOTE! We still have PageReserved() pages in the page tables.
825          * eg. VDSO mappings can cause them to exist.
826          */
827 out:
828         return pfn_to_page(pfn);
829 }
830 #endif
831 
832 /*
833  * copy one vm_area from one task to the other. Assumes the page tables
834  * already present in the new task to be cleared in the whole range
835  * covered by this vma.
836  */
837 
838 static inline unsigned long
839 copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
840                 pte_t *dst_pte, pte_t *src_pte, struct vm_area_struct *vma,
841                 unsigned long addr, int *rss)
842 {
843         unsigned long vm_flags = vma->vm_flags;
844         pte_t pte = *src_pte;
845         struct page *page;
846 
847         /* pte contains position in swap or file, so copy. */
848         if (unlikely(!pte_present(pte))) {
849                 swp_entry_t entry = pte_to_swp_entry(pte);
850 
851                 if (likely(!non_swap_entry(entry))) {
852                         if (swap_duplicate(entry) < 0)
853                                 return entry.val;
854 
855                         /* make sure dst_mm is on swapoff's mmlist. */
856                         if (unlikely(list_empty(&dst_mm->mmlist))) {
857                                 spin_lock(&mmlist_lock);
858                                 if (list_empty(&dst_mm->mmlist))
859                                         list_add(&dst_mm->mmlist,
860                                                         &src_mm->mmlist);
861                                 spin_unlock(&mmlist_lock);
862                         }
863                         rss[MM_SWAPENTS]++;
864                 } else if (is_migration_entry(entry)) {
865                         page = migration_entry_to_page(entry);
866 
867                         rss[mm_counter(page)]++;
868 
869                         if (is_write_migration_entry(entry) &&
870                                         is_cow_mapping(vm_flags)) {
871                                 /*
872                                  * COW mappings require pages in both
873                                  * parent and child to be set to read.
874                                  */
875                                 make_migration_entry_read(&entry);
876                                 pte = swp_entry_to_pte(entry);
877                                 if (pte_swp_soft_dirty(*src_pte))
878                                         pte = pte_swp_mksoft_dirty(pte);
879                                 set_pte_at(src_mm, addr, src_pte, pte);
880                         }
881                 }
882                 goto out_set_pte;
883         }
884 
885         /*
886          * If it's a COW mapping, write protect it both
887          * in the parent and the child
888          */
889         if (is_cow_mapping(vm_flags)) {
890                 ptep_set_wrprotect(src_mm, addr, src_pte);
891                 pte = pte_wrprotect(pte);
892         }
893 
894         /*
895          * If it's a shared mapping, mark it clean in
896          * the child
897          */
898         if (vm_flags & VM_SHARED)
899                 pte = pte_mkclean(pte);
900         pte = pte_mkold(pte);
901 
902         page = vm_normal_page(vma, addr, pte);
903         if (page) {
904                 get_page(page);
905                 page_dup_rmap(page, false);
906                 rss[mm_counter(page)]++;
907         }
908 
909 out_set_pte:
910         set_pte_at(dst_mm, addr, dst_pte, pte);
911         return 0;
912 }
913 
914 static int copy_pte_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
915                    pmd_t *dst_pmd, pmd_t *src_pmd, struct vm_area_struct *vma,
916                    unsigned long addr, unsigned long end)
917 {
918         pte_t *orig_src_pte, *orig_dst_pte;
919         pte_t *src_pte, *dst_pte;
920         spinlock_t *src_ptl, *dst_ptl;
921         int progress = 0;
922         int rss[NR_MM_COUNTERS];
923         swp_entry_t entry = (swp_entry_t){0};
924 
925 again:
926         init_rss_vec(rss);
927 
928         dst_pte = pte_alloc_map_lock(dst_mm, dst_pmd, addr, &dst_ptl);
929         if (!dst_pte)
930                 return -ENOMEM;
931         src_pte = pte_offset_map(src_pmd, addr);
932         src_ptl = pte_lockptr(src_mm, src_pmd);
933         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
934         orig_src_pte = src_pte;
935         orig_dst_pte = dst_pte;
936         arch_enter_lazy_mmu_mode();
937 
938         do {
939                 /*
940                  * We are holding two locks at this point - either of them
941                  * could generate latencies in another task on another CPU.
942                  */
943                 if (progress >= 32) {
944                         progress = 0;
945                         if (need_resched() ||
946                             spin_needbreak(src_ptl) || spin_needbreak(dst_ptl))
947                                 break;
948                 }
949                 if (pte_none(*src_pte)) {
950                         progress++;
951                         continue;
952                 }
953                 entry.val = copy_one_pte(dst_mm, src_mm, dst_pte, src_pte,
954                                                         vma, addr, rss);
955                 if (entry.val)
956                         break;
957                 progress += 8;
958         } while (dst_pte++, src_pte++, addr += PAGE_SIZE, addr != end);
959 
960         arch_leave_lazy_mmu_mode();
961         spin_unlock(src_ptl);
962         pte_unmap(orig_src_pte);
963         add_mm_rss_vec(dst_mm, rss);
964         pte_unmap_unlock(orig_dst_pte, dst_ptl);
965         cond_resched();
966 
967         if (entry.val) {
968                 if (add_swap_count_continuation(entry, GFP_KERNEL) < 0)
969                         return -ENOMEM;
970                 progress = 0;
971         }
972         if (addr != end)
973                 goto again;
974         return 0;
975 }
976 
977 static inline int copy_pmd_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
978                 pud_t *dst_pud, pud_t *src_pud, struct vm_area_struct *vma,
979                 unsigned long addr, unsigned long end)
980 {
981         pmd_t *src_pmd, *dst_pmd;
982         unsigned long next;
983 
984         dst_pmd = pmd_alloc(dst_mm, dst_pud, addr);
985         if (!dst_pmd)
986                 return -ENOMEM;
987         src_pmd = pmd_offset(src_pud, addr);
988         do {
989                 next = pmd_addr_end(addr, end);
990                 if (pmd_trans_huge(*src_pmd) || pmd_devmap(*src_pmd)) {
991                         int err;
992                         VM_BUG_ON(next-addr != HPAGE_PMD_SIZE);
993                         err = copy_huge_pmd(dst_mm, src_mm,
994                                             dst_pmd, src_pmd, addr, vma);
995                         if (err == -ENOMEM)
996                                 return -ENOMEM;
997                         if (!err)
998                                 continue;
999                         /* fall through */
1000                 }
1001                 if (pmd_none_or_clear_bad(src_pmd))
1002                         continue;
1003                 if (copy_pte_range(dst_mm, src_mm, dst_pmd, src_pmd,
1004                                                 vma, addr, next))
1005                         return -ENOMEM;
1006         } while (dst_pmd++, src_pmd++, addr = next, addr != end);
1007         return 0;
1008 }
1009 
1010 static inline int copy_pud_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1011                 pgd_t *dst_pgd, pgd_t *src_pgd, struct vm_area_struct *vma,
1012                 unsigned long addr, unsigned long end)
1013 {
1014         pud_t *src_pud, *dst_pud;
1015         unsigned long next;
1016 
1017         dst_pud = pud_alloc(dst_mm, dst_pgd, addr);
1018         if (!dst_pud)
1019                 return -ENOMEM;
1020         src_pud = pud_offset(src_pgd, addr);
1021         do {
1022                 next = pud_addr_end(addr, end);
1023                 if (pud_none_or_clear_bad(src_pud))
1024                         continue;
1025                 if (copy_pmd_range(dst_mm, src_mm, dst_pud, src_pud,
1026                                                 vma, addr, next))
1027                         return -ENOMEM;
1028         } while (dst_pud++, src_pud++, addr = next, addr != end);
1029         return 0;
1030 }
1031 
1032 int copy_page_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1033                 struct vm_area_struct *vma)
1034 {
1035         pgd_t *src_pgd, *dst_pgd;
1036         unsigned long next;
1037         unsigned long addr = vma->vm_start;
1038         unsigned long end = vma->vm_end;
1039         unsigned long mmun_start;       /* For mmu_notifiers */
1040         unsigned long mmun_end;         /* For mmu_notifiers */
1041         bool is_cow;
1042         int ret;
1043 
1044         /*
1045          * Don't copy ptes where a page fault will fill them correctly.
1046          * Fork becomes much lighter when there are big shared or private
1047          * readonly mappings. The tradeoff is that copy_page_range is more
1048          * efficient than faulting.
1049          */
1050         if (!(vma->vm_flags & (VM_HUGETLB | VM_PFNMAP | VM_MIXEDMAP)) &&
1051                         !vma->anon_vma)
1052                 return 0;
1053 
1054         if (is_vm_hugetlb_page(vma))
1055                 return copy_hugetlb_page_range(dst_mm, src_mm, vma);
1056 
1057         if (unlikely(vma->vm_flags & VM_PFNMAP)) {
1058                 /*
1059                  * We do not free on error cases below as remove_vma
1060                  * gets called on error from higher level routine
1061                  */
1062                 ret = track_pfn_copy(vma);
1063                 if (ret)
1064                         return ret;
1065         }
1066 
1067         /*
1068          * We need to invalidate the secondary MMU mappings only when
1069          * there could be a permission downgrade on the ptes of the
1070          * parent mm. And a permission downgrade will only happen if
1071          * is_cow_mapping() returns true.
1072          */
1073         is_cow = is_cow_mapping(vma->vm_flags);
1074         mmun_start = addr;
1075         mmun_end   = end;
1076         if (is_cow)
1077                 mmu_notifier_invalidate_range_start(src_mm, mmun_start,
1078                                                     mmun_end);
1079 
1080         ret = 0;
1081         dst_pgd = pgd_offset(dst_mm, addr);
1082         src_pgd = pgd_offset(src_mm, addr);
1083         do {
1084                 next = pgd_addr_end(addr, end);
1085                 if (pgd_none_or_clear_bad(src_pgd))
1086                         continue;
1087                 if (unlikely(copy_pud_range(dst_mm, src_mm, dst_pgd, src_pgd,
1088                                             vma, addr, next))) {
1089                         ret = -ENOMEM;
1090                         break;
1091                 }
1092         } while (dst_pgd++, src_pgd++, addr = next, addr != end);
1093 
1094         if (is_cow)
1095                 mmu_notifier_invalidate_range_end(src_mm, mmun_start, mmun_end);
1096         return ret;
1097 }
1098 
1099 static unsigned long zap_pte_range(struct mmu_gather *tlb,
1100                                 struct vm_area_struct *vma, pmd_t *pmd,
1101                                 unsigned long addr, unsigned long end,
1102                                 struct zap_details *details)
1103 {
1104         struct mm_struct *mm = tlb->mm;
1105         int force_flush = 0;
1106         int rss[NR_MM_COUNTERS];
1107         spinlock_t *ptl;
1108         pte_t *start_pte;
1109         pte_t *pte;
1110         swp_entry_t entry;
1111 
1112 again:
1113         init_rss_vec(rss);
1114         start_pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
1115         pte = start_pte;
1116         arch_enter_lazy_mmu_mode();
1117         do {
1118                 pte_t ptent = *pte;
1119                 if (pte_none(ptent)) {
1120                         continue;
1121                 }
1122 
1123                 if (pte_present(ptent)) {
1124                         struct page *page;
1125 
1126                         page = vm_normal_page(vma, addr, ptent);
1127                         if (unlikely(details) && page) {
1128                                 /*
1129                                  * unmap_shared_mapping_pages() wants to
1130                                  * invalidate cache without truncating:
1131                                  * unmap shared but keep private pages.
1132                                  */
1133                                 if (details->check_mapping &&
1134                                     details->check_mapping != page->mapping)
1135                                         continue;
1136                         }
1137                         ptent = ptep_get_and_clear_full(mm, addr, pte,
1138                                                         tlb->fullmm);
1139                         tlb_remove_tlb_entry(tlb, pte, addr);
1140                         if (unlikely(!page))
1141                                 continue;
1142 
1143                         if (!PageAnon(page)) {
1144                                 if (pte_dirty(ptent)) {
1145                                         /*
1146                                          * oom_reaper cannot tear down dirty
1147                                          * pages
1148                                          */
1149                                         if (unlikely(details && details->ignore_dirty))
1150                                                 continue;
1151                                         force_flush = 1;
1152                                         set_page_dirty(page);
1153                                 }
1154                                 if (pte_young(ptent) &&
1155                                     likely(!(vma->vm_flags & VM_SEQ_READ)))
1156                                         mark_page_accessed(page);
1157                         }
1158                         rss[mm_counter(page)]--;
1159                         page_remove_rmap(page, false);
1160                         if (unlikely(page_mapcount(page) < 0))
1161                                 print_bad_pte(vma, addr, ptent, page);
1162                         if (unlikely(!__tlb_remove_page(tlb, page))) {
1163                                 force_flush = 1;
1164                                 addr += PAGE_SIZE;
1165                                 break;
1166                         }
1167                         continue;
1168                 }
1169                 /* only check swap_entries if explicitly asked for in details */
1170                 if (unlikely(details && !details->check_swap_entries))
1171                         continue;
1172 
1173                 entry = pte_to_swp_entry(ptent);
1174                 if (!non_swap_entry(entry))
1175                         rss[MM_SWAPENTS]--;
1176                 else if (is_migration_entry(entry)) {
1177                         struct page *page;
1178 
1179                         page = migration_entry_to_page(entry);
1180                         rss[mm_counter(page)]--;
1181                 }
1182                 if (unlikely(!free_swap_and_cache(entry)))
1183                         print_bad_pte(vma, addr, ptent, NULL);
1184                 pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
1185         } while (pte++, addr += PAGE_SIZE, addr != end);
1186 
1187         add_mm_rss_vec(mm, rss);
1188         arch_leave_lazy_mmu_mode();
1189 
1190         /* Do the actual TLB flush before dropping ptl */
1191         if (force_flush)
1192                 tlb_flush_mmu_tlbonly(tlb);
1193         pte_unmap_unlock(start_pte, ptl);
1194 
1195         /*
1196          * If we forced a TLB flush (either due to running out of
1197          * batch buffers or because we needed to flush dirty TLB
1198          * entries before releasing the ptl), free the batched
1199          * memory too. Restart if we didn't do everything.
1200          */
1201         if (force_flush) {
1202                 force_flush = 0;
1203                 tlb_flush_mmu_free(tlb);
1204 
1205                 if (addr != end)
1206                         goto again;
1207         }
1208 
1209         return addr;
1210 }
1211 
1212 static inline unsigned long zap_pmd_range(struct mmu_gather *tlb,
1213                                 struct vm_area_struct *vma, pud_t *pud,
1214                                 unsigned long addr, unsigned long end,
1215                                 struct zap_details *details)
1216 {
1217         pmd_t *pmd;
1218         unsigned long next;
1219 
1220         pmd = pmd_offset(pud, addr);
1221         do {
1222                 next = pmd_addr_end(addr, end);
1223                 if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) {
1224                         if (next - addr != HPAGE_PMD_SIZE) {
1225                                 VM_BUG_ON_VMA(vma_is_anonymous(vma) &&
1226                                     !rwsem_is_locked(&tlb->mm->mmap_sem), vma);
1227                                 split_huge_pmd(vma, pmd, addr);
1228                         } else if (zap_huge_pmd(tlb, vma, pmd, addr))
1229                                 goto next;
1230                         /* fall through */
1231                 }
1232                 /*
1233                  * Here there can be other concurrent MADV_DONTNEED or
1234                  * trans huge page faults running, and if the pmd is
1235                  * none or trans huge it can change under us. This is
1236                  * because MADV_DONTNEED holds the mmap_sem in read
1237                  * mode.
1238                  */
1239                 if (pmd_none_or_trans_huge_or_clear_bad(pmd))
1240                         goto next;
1241                 next = zap_pte_range(tlb, vma, pmd, addr, next, details);
1242 next:
1243                 cond_resched();
1244         } while (pmd++, addr = next, addr != end);
1245 
1246         return addr;
1247 }
1248 
1249 static inline unsigned long zap_pud_range(struct mmu_gather *tlb,
1250                                 struct vm_area_struct *vma, pgd_t *pgd,
1251                                 unsigned long addr, unsigned long end,
1252                                 struct zap_details *details)
1253 {
1254         pud_t *pud;
1255         unsigned long next;
1256 
1257         pud = pud_offset(pgd, addr);
1258         do {
1259                 next = pud_addr_end(addr, end);
1260                 if (pud_none_or_clear_bad(pud))
1261                         continue;
1262                 next = zap_pmd_range(tlb, vma, pud, addr, next, details);
1263         } while (pud++, addr = next, addr != end);
1264 
1265         return addr;
1266 }
1267 
1268 void unmap_page_range(struct mmu_gather *tlb,
1269                              struct vm_area_struct *vma,
1270                              unsigned long addr, unsigned long end,
1271                              struct zap_details *details)
1272 {
1273         pgd_t *pgd;
1274         unsigned long next;
1275 
1276         BUG_ON(addr >= end);
1277         tlb_start_vma(tlb, vma);
1278         pgd = pgd_offset(vma->vm_mm, addr);
1279         do {
1280                 next = pgd_addr_end(addr, end);
1281                 if (pgd_none_or_clear_bad(pgd))
1282                         continue;
1283                 next = zap_pud_range(tlb, vma, pgd, addr, next, details);
1284         } while (pgd++, addr = next, addr != end);
1285         tlb_end_vma(tlb, vma);
1286 }
1287 
1288 
1289 static void unmap_single_vma(struct mmu_gather *tlb,
1290                 struct vm_area_struct *vma, unsigned long start_addr,
1291                 unsigned long end_addr,
1292                 struct zap_details *details)
1293 {
1294         unsigned long start = max(vma->vm_start, start_addr);
1295         unsigned long end;
1296 
1297         if (start >= vma->vm_end)
1298                 return;
1299         end = min(vma->vm_end, end_addr);
1300         if (end <= vma->vm_start)
1301                 return;
1302 
1303         if (vma->vm_file)
1304                 uprobe_munmap(vma, start, end);
1305 
1306         if (unlikely(vma->vm_flags & VM_PFNMAP))
1307                 untrack_pfn(vma, 0, 0);
1308 
1309         if (start != end) {
1310                 if (unlikely(is_vm_hugetlb_page(vma))) {
1311                         /*
1312                          * It is undesirable to test vma->vm_file as it
1313                          * should be non-null for valid hugetlb area.
1314                          * However, vm_file will be NULL in the error
1315                          * cleanup path of mmap_region. When
1316                          * hugetlbfs ->mmap method fails,
1317                          * mmap_region() nullifies vma->vm_file
1318                          * before calling this function to clean up.
1319                          * Since no pte has actually been setup, it is
1320                          * safe to do nothing in this case.
1321                          */
1322                         if (vma->vm_file) {
1323                                 i_mmap_lock_write(vma->vm_file->f_mapping);
1324                                 __unmap_hugepage_range_final(tlb, vma, start, end, NULL);
1325                                 i_mmap_unlock_write(vma->vm_file->f_mapping);
1326                         }
1327                 } else
1328                         unmap_page_range(tlb, vma, start, end, details);
1329         }
1330 }
1331 
1332 /**
1333  * unmap_vmas - unmap a range of memory covered by a list of vma's
1334  * @tlb: address of the caller's struct mmu_gather
1335  * @vma: the starting vma
1336  * @start_addr: virtual address at which to start unmapping
1337  * @end_addr: virtual address at which to end unmapping
1338  *
1339  * Unmap all pages in the vma list.
1340  *
1341  * Only addresses between `start' and `end' will be unmapped.
1342  *
1343  * The VMA list must be sorted in ascending virtual address order.
1344  *
1345  * unmap_vmas() assumes that the caller will flush the whole unmapped address
1346  * range after unmap_vmas() returns.  So the only responsibility here is to
1347  * ensure that any thus-far unmapped pages are flushed before unmap_vmas()
1348  * drops the lock and schedules.
1349  */
1350 void unmap_vmas(struct mmu_gather *tlb,
1351                 struct vm_area_struct *vma, unsigned long start_addr,
1352                 unsigned long end_addr)
1353 {
1354         struct mm_struct *mm = vma->vm_mm;
1355 
1356         mmu_notifier_invalidate_range_start(mm, start_addr, end_addr);
1357         for ( ; vma && vma->vm_start < end_addr; vma = vma->vm_next)
1358                 unmap_single_vma(tlb, vma, start_addr, end_addr, NULL);
1359         mmu_notifier_invalidate_range_end(mm, start_addr, end_addr);
1360 }
1361 
1362 /**
1363  * zap_page_range - remove user pages in a given range
1364  * @vma: vm_area_struct holding the applicable pages
1365  * @start: starting address of pages to zap
1366  * @size: number of bytes to zap
1367  * @details: details of shared cache invalidation
1368  *
1369  * Caller must protect the VMA list
1370  */
1371 void zap_page_range(struct vm_area_struct *vma, unsigned long start,
1372                 unsigned long size, struct zap_details *details)
1373 {
1374         struct mm_struct *mm = vma->vm_mm;
1375         struct mmu_gather tlb;
1376         unsigned long end = start + size;
1377 
1378         lru_add_drain();
1379         tlb_gather_mmu(&tlb, mm, start, end);
1380         update_hiwater_rss(mm);
1381         mmu_notifier_invalidate_range_start(mm, start, end);
1382         for ( ; vma && vma->vm_start < end; vma = vma->vm_next)
1383                 unmap_single_vma(&tlb, vma, start, end, details);
1384         mmu_notifier_invalidate_range_end(mm, start, end);
1385         tlb_finish_mmu(&tlb, start, end);
1386 }
1387 
1388 /**
1389  * zap_page_range_single - remove user pages in a given range
1390  * @vma: vm_area_struct holding the applicable pages
1391  * @address: starting address of pages to zap
1392  * @size: number of bytes to zap
1393  * @details: details of shared cache invalidation
1394  *
1395  * The range must fit into one VMA.
1396  */
1397 static void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
1398                 unsigned long size, struct zap_details *details)
1399 {
1400         struct mm_struct *mm = vma->vm_mm;
1401         struct mmu_gather tlb;
1402         unsigned long end = address + size;
1403 
1404         lru_add_drain();
1405         tlb_gather_mmu(&tlb, mm, address, end);
1406         update_hiwater_rss(mm);
1407         mmu_notifier_invalidate_range_start(mm, address, end);
1408         unmap_single_vma(&tlb, vma, address, end, details);
1409         mmu_notifier_invalidate_range_end(mm, address, end);
1410         tlb_finish_mmu(&tlb, address, end);
1411 }
1412 
1413 /**
1414  * zap_vma_ptes - remove ptes mapping the vma
1415  * @vma: vm_area_struct holding ptes to be zapped
1416  * @address: starting address of pages to zap
1417  * @size: number of bytes to zap
1418  *
1419  * This function only unmaps ptes assigned to VM_PFNMAP vmas.
1420  *
1421  * The entire address range must be fully contained within the vma.
1422  *
1423  * Returns 0 if successful.
1424  */
1425 int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
1426                 unsigned long size)
1427 {
1428         if (address < vma->vm_start || address + size > vma->vm_end ||
1429                         !(vma->vm_flags & VM_PFNMAP))
1430                 return -1;
1431         zap_page_range_single(vma, address, size, NULL);
1432         return 0;
1433 }
1434 EXPORT_SYMBOL_GPL(zap_vma_ptes);
1435 
1436 pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr,
1437                         spinlock_t **ptl)
1438 {
1439         pgd_t * pgd = pgd_offset(mm, addr);
1440         pud_t * pud = pud_alloc(mm, pgd, addr);
1441         if (pud) {
1442                 pmd_t * pmd = pmd_alloc(mm, pud, addr);
1443                 if (pmd) {
1444                         VM_BUG_ON(pmd_trans_huge(*pmd));
1445                         return pte_alloc_map_lock(mm, pmd, addr, ptl);
1446                 }
1447         }
1448         return NULL;
1449 }
1450 
1451 /*
1452  * This is the old fallback for page remapping.
1453  *
1454  * For historical reasons, it only allows reserved pages. Only
1455  * old drivers should use this, and they needed to mark their
1456  * pages reserved for the old functions anyway.
1457  */
1458 static int insert_page(struct vm_area_struct *vma, unsigned long addr,
1459                         struct page *page, pgprot_t prot)
1460 {
1461         struct mm_struct *mm = vma->vm_mm;
1462         int retval;
1463         pte_t *pte;
1464         spinlock_t *ptl;
1465 
1466         retval = -EINVAL;
1467         if (PageAnon(page))
1468                 goto out;
1469         retval = -ENOMEM;
1470         flush_dcache_page(page);
1471         pte = get_locked_pte(mm, addr, &ptl);
1472         if (!pte)
1473                 goto out;
1474         retval = -EBUSY;
1475         if (!pte_none(*pte))
1476                 goto out_unlock;
1477 
1478         /* Ok, finally just insert the thing.. */
1479         get_page(page);
1480         inc_mm_counter_fast(mm, mm_counter_file(page));
1481         page_add_file_rmap(page);
1482         set_pte_at(mm, addr, pte, mk_pte(page, prot));
1483 
1484         retval = 0;
1485         pte_unmap_unlock(pte, ptl);
1486         return retval;
1487 out_unlock:
1488         pte_unmap_unlock(pte, ptl);
1489 out:
1490         return retval;
1491 }
1492 
1493 /**
1494  * vm_insert_page - insert single page into user vma
1495  * @vma: user vma to map to
1496  * @addr: target user address of this page
1497  * @page: source kernel page
1498  *
1499  * This allows drivers to insert individual pages they've allocated
1500  * into a user vma.
1501  *
1502  * The page has to be a nice clean _individual_ kernel allocation.
1503  * If you allocate a compound page, you need to have marked it as
1504  * such (__GFP_COMP), or manually just split the page up yourself
1505  * (see split_page()).
1506  *
1507  * NOTE! Traditionally this was done with "remap_pfn_range()" which
1508  * took an arbitrary page protection parameter. This doesn't allow
1509  * that. Your vma protection will have to be set up correctly, which
1510  * means that if you want a shared writable mapping, you'd better
1511  * ask for a shared writable mapping!
1512  *
1513  * The page does not need to be reserved.
1514  *
1515  * Usually this function is called from f_op->mmap() handler
1516  * under mm->mmap_sem write-lock, so it can change vma->vm_flags.
1517  * Caller must set VM_MIXEDMAP on vma if it wants to call this
1518  * function from other places, for example from page-fault handler.
1519  */
1520 int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
1521                         struct page *page)
1522 {
1523         if (addr < vma->vm_start || addr >= vma->vm_end)
1524                 return -EFAULT;
1525         if (!page_count(page))
1526                 return -EINVAL;
1527         if (!(vma->vm_flags & VM_MIXEDMAP)) {
1528                 BUG_ON(down_read_trylock(&vma->vm_mm->mmap_sem));
1529                 BUG_ON(vma->vm_flags & VM_PFNMAP);
1530                 vma->vm_flags |= VM_MIXEDMAP;
1531         }
1532         return insert_page(vma, addr, page, vma->vm_page_prot);
1533 }
1534 EXPORT_SYMBOL(vm_insert_page);
1535 
1536 static int insert_pfn(struct vm_area_struct *vma, unsigned long addr,
1537                         pfn_t pfn, pgprot_t prot)
1538 {
1539         struct mm_struct *mm = vma->vm_mm;
1540         int retval;
1541         pte_t *pte, entry;
1542         spinlock_t *ptl;
1543 
1544         retval = -ENOMEM;
1545         pte = get_locked_pte(mm, addr, &ptl);
1546         if (!pte)
1547                 goto out;
1548         retval = -EBUSY;
1549         if (!pte_none(*pte))
1550                 goto out_unlock;
1551 
1552         /* Ok, finally just insert the thing.. */
1553         if (pfn_t_devmap(pfn))
1554                 entry = pte_mkdevmap(pfn_t_pte(pfn, prot));
1555         else
1556                 entry = pte_mkspecial(pfn_t_pte(pfn, prot));
1557         set_pte_at(mm, addr, pte, entry);
1558         update_mmu_cache(vma, addr, pte); /* XXX: why not for insert_page? */
1559 
1560         retval = 0;
1561 out_unlock:
1562         pte_unmap_unlock(pte, ptl);
1563 out:
1564         return retval;
1565 }
1566 
1567 /**
1568  * vm_insert_pfn - insert single pfn into user vma
1569  * @vma: user vma to map to
1570  * @addr: target user address of this page
1571  * @pfn: source kernel pfn
1572  *
1573  * Similar to vm_insert_page, this allows drivers to insert individual pages
1574  * they've allocated into a user vma. Same comments apply.
1575  *
1576  * This function should only be called from a vm_ops->fault handler, and
1577  * in that case the handler should return NULL.
1578  *
1579  * vma cannot be a COW mapping.
1580  *
1581  * As this is called only for pages that do not currently exist, we
1582  * do not need to flush old virtual caches or the TLB.
1583  */
1584 int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
1585                         unsigned long pfn)
1586 {
1587         return vm_insert_pfn_prot(vma, addr, pfn, vma->vm_page_prot);
1588 }
1589 EXPORT_SYMBOL(vm_insert_pfn);
1590 
1591 /**
1592  * vm_insert_pfn_prot - insert single pfn into user vma with specified pgprot
1593  * @vma: user vma to map to
1594  * @addr: target user address of this page
1595  * @pfn: source kernel pfn
1596  * @pgprot: pgprot flags for the inserted page
1597  *
1598  * This is exactly like vm_insert_pfn, except that it allows drivers to
1599  * to override pgprot on a per-page basis.
1600  *
1601  * This only makes sense for IO mappings, and it makes no sense for
1602  * cow mappings.  In general, using multiple vmas is preferable;
1603  * vm_insert_pfn_prot should only be used if using multiple VMAs is
1604  * impractical.
1605  */
1606 int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
1607                         unsigned long pfn, pgprot_t pgprot)
1608 {
1609         int ret;
1610         /*
1611          * Technically, architectures with pte_special can avoid all these
1612          * restrictions (same for remap_pfn_range).  However we would like
1613          * consistency in testing and feature parity among all, so we should
1614          * try to keep these invariants in place for everybody.
1615          */
1616         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
1617         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
1618                                                 (VM_PFNMAP|VM_MIXEDMAP));
1619         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
1620         BUG_ON((vma->vm_flags & VM_MIXEDMAP) && pfn_valid(pfn));
1621 
1622         if (addr < vma->vm_start || addr >= vma->vm_end)
1623                 return -EFAULT;
1624         if (track_pfn_insert(vma, &pgprot, __pfn_to_pfn_t(pfn, PFN_DEV)))
1625                 return -EINVAL;
1626 
1627         ret = insert_pfn(vma, addr, __pfn_to_pfn_t(pfn, PFN_DEV), pgprot);
1628 
1629         return ret;
1630 }
1631 EXPORT_SYMBOL(vm_insert_pfn_prot);
1632 
1633 int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
1634                         pfn_t pfn)
1635 {
1636         BUG_ON(!(vma->vm_flags & VM_MIXEDMAP));
1637 
1638         if (addr < vma->vm_start || addr >= vma->vm_end)
1639                 return -EFAULT;
1640 
1641         /*
1642          * If we don't have pte special, then we have to use the pfn_valid()
1643          * based VM_MIXEDMAP scheme (see vm_normal_page), and thus we *must*
1644          * refcount the page if pfn_valid is true (hence insert_page rather
1645          * than insert_pfn).  If a zero_pfn were inserted into a VM_MIXEDMAP
1646          * without pte special, it would there be refcounted as a normal page.
1647          */
1648         if (!HAVE_PTE_SPECIAL && !pfn_t_devmap(pfn) && pfn_t_valid(pfn)) {
1649                 struct page *page;
1650 
1651                 /*
1652                  * At this point we are committed to insert_page()
1653                  * regardless of whether the caller specified flags that
1654                  * result in pfn_t_has_page() == false.
1655                  */
1656                 page = pfn_to_page(pfn_t_to_pfn(pfn));
1657                 return insert_page(vma, addr, page, vma->vm_page_prot);
1658         }
1659         return insert_pfn(vma, addr, pfn, vma->vm_page_prot);
1660 }
1661 EXPORT_SYMBOL(vm_insert_mixed);
1662 
1663 /*
1664  * maps a range of physical memory into the requested pages. the old
1665  * mappings are removed. any references to nonexistent pages results
1666  * in null mappings (currently treated as "copy-on-access")
1667  */
1668 static int remap_pte_range(struct mm_struct *mm, pmd_t *pmd,
1669                         unsigned long addr, unsigned long end,
1670                         unsigned long pfn, pgprot_t prot)
1671 {
1672         pte_t *pte;
1673         spinlock_t *ptl;
1674 
1675         pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
1676         if (!pte)
1677                 return -ENOMEM;
1678         arch_enter_lazy_mmu_mode();
1679         do {
1680                 BUG_ON(!pte_none(*pte));
1681                 set_pte_at(mm, addr, pte, pte_mkspecial(pfn_pte(pfn, prot)));
1682                 pfn++;
1683         } while (pte++, addr += PAGE_SIZE, addr != end);
1684         arch_leave_lazy_mmu_mode();
1685         pte_unmap_unlock(pte - 1, ptl);
1686         return 0;
1687 }
1688 
1689 static inline int remap_pmd_range(struct mm_struct *mm, pud_t *pud,
1690                         unsigned long addr, unsigned long end,
1691                         unsigned long pfn, pgprot_t prot)
1692 {
1693         pmd_t *pmd;
1694         unsigned long next;
1695 
1696         pfn -= addr >> PAGE_SHIFT;
1697         pmd = pmd_alloc(mm, pud, addr);
1698         if (!pmd)
1699                 return -ENOMEM;
1700         VM_BUG_ON(pmd_trans_huge(*pmd));
1701         do {
1702                 next = pmd_addr_end(addr, end);
1703                 if (remap_pte_range(mm, pmd, addr, next,
1704                                 pfn + (addr >> PAGE_SHIFT), prot))
1705                         return -ENOMEM;
1706         } while (pmd++, addr = next, addr != end);
1707         return 0;
1708 }
1709 
1710 static inline int remap_pud_range(struct mm_struct *mm, pgd_t *pgd,
1711                         unsigned long addr, unsigned long end,
1712                         unsigned long pfn, pgprot_t prot)
1713 {
1714         pud_t *pud;
1715         unsigned long next;
1716 
1717         pfn -= addr >> PAGE_SHIFT;
1718         pud = pud_alloc(mm, pgd, addr);
1719         if (!pud)
1720                 return -ENOMEM;
1721         do {
1722                 next = pud_addr_end(addr, end);
1723                 if (remap_pmd_range(mm, pud, addr, next,
1724                                 pfn + (addr >> PAGE_SHIFT), prot))
1725                         return -ENOMEM;
1726         } while (pud++, addr = next, addr != end);
1727         return 0;
1728 }
1729 
1730 /**
1731  * remap_pfn_range - remap kernel memory to userspace
1732  * @vma: user vma to map to
1733  * @addr: target user address to start at
1734  * @pfn: physical address of kernel memory
1735  * @size: size of map area
1736  * @prot: page protection flags for this mapping
1737  *
1738  *  Note: this is only safe if the mm semaphore is held when called.
1739  */
1740 int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
1741                     unsigned long pfn, unsigned long size, pgprot_t prot)
1742 {
1743         pgd_t *pgd;
1744         unsigned long next;
1745         unsigned long end = addr + PAGE_ALIGN(size);
1746         struct mm_struct *mm = vma->vm_mm;
1747         int err;
1748 
1749         /*
1750          * Physically remapped pages are special. Tell the
1751          * rest of the world about it:
1752          *   VM_IO tells people not to look at these pages
1753          *      (accesses can have side effects).
1754          *   VM_PFNMAP tells the core MM that the base pages are just
1755          *      raw PFN mappings, and do not have a "struct page" associated
1756          *      with them.
1757          *   VM_DONTEXPAND
1758          *      Disable vma merging and expanding with mremap().
1759          *   VM_DONTDUMP
1760          *      Omit vma from core dump, even when VM_IO turned off.
1761          *
1762          * There's a horrible special case to handle copy-on-write
1763          * behaviour that some programs depend on. We mark the "original"
1764          * un-COW'ed pages by matching them up with "vma->vm_pgoff".
1765          * See vm_normal_page() for details.
1766          */
1767         if (is_cow_mapping(vma->vm_flags)) {
1768                 if (addr != vma->vm_start || end != vma->vm_end)
1769                         return -EINVAL;
1770                 vma->vm_pgoff = pfn;
1771         }
1772 
1773         err = track_pfn_remap(vma, &prot, pfn, addr, PAGE_ALIGN(size));
1774         if (err)
1775                 return -EINVAL;
1776 
1777         vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
1778 
1779         BUG_ON(addr >= end);
1780         pfn -= addr >> PAGE_SHIFT;
1781         pgd = pgd_offset(mm, addr);
1782         flush_cache_range(vma, addr, end);
1783         do {
1784                 next = pgd_addr_end(addr, end);
1785                 err = remap_pud_range(mm, pgd, addr, next,
1786                                 pfn + (addr >> PAGE_SHIFT), prot);
1787                 if (err)
1788                         break;
1789         } while (pgd++, addr = next, addr != end);
1790 
1791         if (err)
1792                 untrack_pfn(vma, pfn, PAGE_ALIGN(size));
1793 
1794         return err;
1795 }
1796 EXPORT_SYMBOL(remap_pfn_range);
1797 
1798 /**
1799  * vm_iomap_memory - remap memory to userspace
1800  * @vma: user vma to map to
1801  * @start: start of area
1802  * @len: size of area
1803  *
1804  * This is a simplified io_remap_pfn_range() for common driver use. The
1805  * driver just needs to give us the physical memory range to be mapped,
1806  * we'll figure out the rest from the vma information.
1807  *
1808  * NOTE! Some drivers might want to tweak vma->vm_page_prot first to get
1809  * whatever write-combining details or similar.
1810  */
1811 int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len)
1812 {
1813         unsigned long vm_len, pfn, pages;
1814 
1815         /* Check that the physical memory area passed in looks valid */
1816         if (start + len < start)
1817                 return -EINVAL;
1818         /*
1819          * You *really* shouldn't map things that aren't page-aligned,
1820          * but we've historically allowed it because IO memory might
1821          * just have smaller alignment.
1822          */
1823         len += start & ~PAGE_MASK;
1824         pfn = start >> PAGE_SHIFT;
1825         pages = (len + ~PAGE_MASK) >> PAGE_SHIFT;
1826         if (pfn + pages < pfn)
1827                 return -EINVAL;
1828 
1829         /* We start the mapping 'vm_pgoff' pages into the area */
1830         if (vma->vm_pgoff > pages)
1831                 return -EINVAL;
1832         pfn += vma->vm_pgoff;
1833         pages -= vma->vm_pgoff;
1834 
1835         /* Can we fit all of the mapping? */
1836         vm_len = vma->vm_end - vma->vm_start;
1837         if (vm_len >> PAGE_SHIFT > pages)
1838                 return -EINVAL;
1839 
1840         /* Ok, let it rip */
1841         return io_remap_pfn_range(vma, vma->vm_start, pfn, vm_len, vma->vm_page_prot);
1842 }
1843 EXPORT_SYMBOL(vm_iomap_memory);
1844 
1845 static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
1846                                      unsigned long addr, unsigned long end,
1847                                      pte_fn_t fn, void *data)
1848 {
1849         pte_t *pte;
1850         int err;
1851         pgtable_t token;
1852         spinlock_t *uninitialized_var(ptl);
1853 
1854         pte = (mm == &init_mm) ?
1855                 pte_alloc_kernel(pmd, addr) :
1856                 pte_alloc_map_lock(mm, pmd, addr, &ptl);
1857         if (!pte)
1858                 return -ENOMEM;
1859 
1860         BUG_ON(pmd_huge(*pmd));
1861 
1862         arch_enter_lazy_mmu_mode();
1863 
1864         token = pmd_pgtable(*pmd);
1865 
1866         do {
1867                 err = fn(pte++, token, addr, data);
1868                 if (err)
1869                         break;
1870         } while (addr += PAGE_SIZE, addr != end);
1871 
1872         arch_leave_lazy_mmu_mode();
1873 
1874         if (mm != &init_mm)
1875                 pte_unmap_unlock(pte-1, ptl);
1876         return err;
1877 }
1878 
1879 static int apply_to_pmd_range(struct mm_struct *mm, pud_t *pud,
1880                                      unsigned long addr, unsigned long end,
1881                                      pte_fn_t fn, void *data)
1882 {
1883         pmd_t *pmd;
1884         unsigned long next;
1885         int err;
1886 
1887         BUG_ON(pud_huge(*pud));
1888 
1889         pmd = pmd_alloc(mm, pud, addr);
1890         if (!pmd)
1891                 return -ENOMEM;
1892         do {
1893                 next = pmd_addr_end(addr, end);
1894                 err = apply_to_pte_range(mm, pmd, addr, next, fn, data);
1895                 if (err)
1896                         break;
1897         } while (pmd++, addr = next, addr != end);
1898         return err;
1899 }
1900 
1901 static int apply_to_pud_range(struct mm_struct *mm, pgd_t *pgd,
1902                                      unsigned long addr, unsigned long end,
1903                                      pte_fn_t fn, void *data)
1904 {
1905         pud_t *pud;
1906         unsigned long next;
1907         int err;
1908 
1909         pud = pud_alloc(mm, pgd, addr);
1910         if (!pud)
1911                 return -ENOMEM;
1912         do {
1913                 next = pud_addr_end(addr, end);
1914                 err = apply_to_pmd_range(mm, pud, addr, next, fn, data);
1915                 if (err)
1916                         break;
1917         } while (pud++, addr = next, addr != end);
1918         return err;
1919 }
1920 
1921 /*
1922  * Scan a region of virtual memory, filling in page tables as necessary
1923  * and calling a provided function on each leaf page table.
1924  */
1925 int apply_to_page_range(struct mm_struct *mm, unsigned long addr,
1926                         unsigned long size, pte_fn_t fn, void *data)
1927 {
1928         pgd_t *pgd;
1929         unsigned long next;
1930         unsigned long end = addr + size;
1931         int err;
1932 
1933         if (WARN_ON(addr >= end))
1934                 return -EINVAL;
1935 
1936         pgd = pgd_offset(mm, addr);
1937         do {
1938                 next = pgd_addr_end(addr, end);
1939                 err = apply_to_pud_range(mm, pgd, addr, next, fn, data);
1940                 if (err)
1941                         break;
1942         } while (pgd++, addr = next, addr != end);
1943 
1944         return err;
1945 }
1946 EXPORT_SYMBOL_GPL(apply_to_page_range);
1947 
1948 /*
1949  * handle_pte_fault chooses page fault handler according to an entry which was
1950  * read non-atomically.  Before making any commitment, on those architectures
1951  * or configurations (e.g. i386 with PAE) which might give a mix of unmatched
1952  * parts, do_swap_page must check under lock before unmapping the pte and
1953  * proceeding (but do_wp_page is only called after already making such a check;
1954  * and do_anonymous_page can safely check later on).
1955  */
1956 static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd,
1957                                 pte_t *page_table, pte_t orig_pte)
1958 {
1959         int same = 1;
1960 #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
1961         if (sizeof(pte_t) > sizeof(unsigned long)) {
1962                 spinlock_t *ptl = pte_lockptr(mm, pmd);
1963                 spin_lock(ptl);
1964                 same = pte_same(*page_table, orig_pte);
1965                 spin_unlock(ptl);
1966         }
1967 #endif
1968         pte_unmap(page_table);
1969         return same;
1970 }
1971 
1972 static inline void cow_user_page(struct page *dst, struct page *src, unsigned long va, struct vm_area_struct *vma)
1973 {
1974         debug_dma_assert_idle(src);
1975 
1976         /*
1977          * If the source page was a PFN mapping, we don't have
1978          * a "struct page" for it. We do a best-effort copy by
1979          * just copying from the original user address. If that
1980          * fails, we just zero-fill it. Live with it.
1981          */
1982         if (unlikely(!src)) {
1983                 void *kaddr = kmap_atomic(dst);
1984                 void __user *uaddr = (void __user *)(va & PAGE_MASK);
1985 
1986                 /*
1987                  * This really shouldn't fail, because the page is there
1988                  * in the page tables. But it might just be unreadable,
1989                  * in which case we just give up and fill the result with
1990                  * zeroes.
1991                  */
1992                 if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE))
1993                         clear_page(kaddr);
1994                 kunmap_atomic(kaddr);
1995                 flush_dcache_page(dst);
1996         } else
1997                 copy_user_highpage(dst, src, va, vma);
1998 }
1999 
2000 static gfp_t __get_fault_gfp_mask(struct vm_area_struct *vma)
2001 {
2002         struct file *vm_file = vma->vm_file;
2003 
2004         if (vm_file)
2005                 return mapping_gfp_mask(vm_file->f_mapping) | __GFP_FS | __GFP_IO;
2006 
2007         /*
2008          * Special mappings (e.g. VDSO) do not have any file so fake
2009          * a default GFP_KERNEL for them.
2010          */
2011         return GFP_KERNEL;
2012 }
2013 
2014 /*
2015  * Notify the address space that the page is about to become writable so that
2016  * it can prohibit this or wait for the page to get into an appropriate state.
2017  *
2018  * We do this without the lock held, so that it can sleep if it needs to.
2019  */
2020 static int do_page_mkwrite(struct vm_area_struct *vma, struct page *page,
2021                unsigned long address)
2022 {
2023         struct vm_fault vmf;
2024         int ret;
2025 
2026         vmf.virtual_address = (void __user *)(address & PAGE_MASK);
2027         vmf.pgoff = page->index;
2028         vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
2029         vmf.gfp_mask = __get_fault_gfp_mask(vma);
2030         vmf.page = page;
2031         vmf.cow_page = NULL;
2032 
2033         ret = vma->vm_ops->page_mkwrite(vma, &vmf);
2034         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))
2035                 return ret;
2036         if (unlikely(!(ret & VM_FAULT_LOCKED))) {
2037                 lock_page(page);
2038                 if (!page->mapping) {
2039                         unlock_page(page);
2040                         return 0; /* retry */
2041                 }
2042                 ret |= VM_FAULT_LOCKED;
2043         } else
2044                 VM_BUG_ON_PAGE(!PageLocked(page), page);
2045         return ret;
2046 }
2047 
2048 /*
2049  * Handle write page faults for pages that can be reused in the current vma
2050  *
2051  * This can happen either due to the mapping being with the VM_SHARED flag,
2052  * or due to us being the last reference standing to the page. In either
2053  * case, all we need to do here is to mark the page as writable and update
2054  * any related book-keeping.
2055  */
2056 static inline int wp_page_reuse(struct mm_struct *mm,
2057                         struct vm_area_struct *vma, unsigned long address,
2058                         pte_t *page_table, spinlock_t *ptl, pte_t orig_pte,
2059                         struct page *page, int page_mkwrite,
2060                         int dirty_shared)
2061         __releases(ptl)
2062 {
2063         pte_t entry;
2064         /*
2065          * Clear the pages cpupid information as the existing
2066          * information potentially belongs to a now completely
2067          * unrelated process.
2068          */
2069         if (page)
2070                 page_cpupid_xchg_last(page, (1 << LAST_CPUPID_SHIFT) - 1);
2071 
2072         flush_cache_page(vma, address, pte_pfn(orig_pte));
2073         entry = pte_mkyoung(orig_pte);
2074         entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2075         if (ptep_set_access_flags(vma, address, page_table, entry, 1))
2076                 update_mmu_cache(vma, address, page_table);
2077         pte_unmap_unlock(page_table, ptl);
2078 
2079         if (dirty_shared) {
2080                 struct address_space *mapping;
2081                 int dirtied;
2082 
2083                 if (!page_mkwrite)
2084                         lock_page(page);
2085 
2086                 dirtied = set_page_dirty(page);
2087                 VM_BUG_ON_PAGE(PageAnon(page), page);
2088                 mapping = page->mapping;
2089                 unlock_page(page);
2090                 put_page(page);
2091 
2092                 if ((dirtied || page_mkwrite) && mapping) {
2093                         /*
2094                          * Some device drivers do not set page.mapping
2095                          * but still dirty their pages
2096                          */
2097                         balance_dirty_pages_ratelimited(mapping);
2098                 }
2099 
2100                 if (!page_mkwrite)
2101                         file_update_time(vma->vm_file);
2102         }
2103 
2104         return VM_FAULT_WRITE;
2105 }
2106 
2107 /*
2108  * Handle the case of a page which we actually need to copy to a new page.
2109  *
2110  * Called with mmap_sem locked and the old page referenced, but
2111  * without the ptl held.
2112  *
2113  * High level logic flow:
2114  *
2115  * - Allocate a page, copy the content of the old page to the new one.
2116  * - Handle book keeping and accounting - cgroups, mmu-notifiers, etc.
2117  * - Take the PTL. If the pte changed, bail out and release the allocated page
2118  * - If the pte is still the way we remember it, update the page table and all
2119  *   relevant references. This includes dropping the reference the page-table
2120  *   held to the old page, as well as updating the rmap.
2121  * - In any case, unlock the PTL and drop the reference we took to the old page.
2122  */
2123 static int wp_page_copy(struct mm_struct *mm, struct vm_area_struct *vma,
2124                         unsigned long address, pte_t *page_table, pmd_t *pmd,
2125                         pte_t orig_pte, struct page *old_page)
2126 {
2127         struct page *new_page = NULL;
2128         spinlock_t *ptl = NULL;
2129         pte_t entry;
2130         int page_copied = 0;
2131         const unsigned long mmun_start = address & PAGE_MASK;   /* For mmu_notifiers */
2132         const unsigned long mmun_end = mmun_start + PAGE_SIZE;  /* For mmu_notifiers */
2133         struct mem_cgroup *memcg;
2134 
2135         if (unlikely(anon_vma_prepare(vma)))
2136                 goto oom;
2137 
2138         if (is_zero_pfn(pte_pfn(orig_pte))) {
2139                 new_page = alloc_zeroed_user_highpage_movable(vma, address);
2140                 if (!new_page)
2141                         goto oom;
2142         } else {
2143                 new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
2144                 if (!new_page)
2145                         goto oom;
2146                 cow_user_page(new_page, old_page, address, vma);
2147         }
2148 
2149         if (mem_cgroup_try_charge(new_page, mm, GFP_KERNEL, &memcg, false))
2150                 goto oom_free_new;
2151 
2152         __SetPageUptodate(new_page);
2153 
2154         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2155 
2156         /*
2157          * Re-check the pte - we dropped the lock
2158          */
2159         page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2160         if (likely(pte_same(*page_table, orig_pte))) {
2161                 if (old_page) {
2162                         if (!PageAnon(old_page)) {
2163                                 dec_mm_counter_fast(mm,
2164                                                 mm_counter_file(old_page));
2165                                 inc_mm_counter_fast(mm, MM_ANONPAGES);
2166                         }
2167                 } else {
2168                         inc_mm_counter_fast(mm, MM_ANONPAGES);
2169                 }
2170                 flush_cache_page(vma, address, pte_pfn(orig_pte));
2171                 entry = mk_pte(new_page, vma->vm_page_prot);
2172                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2173                 /*
2174                  * Clear the pte entry and flush it first, before updating the
2175                  * pte with the new entry. This will avoid a race condition
2176                  * seen in the presence of one thread doing SMC and another
2177                  * thread doing COW.
2178                  */
2179                 ptep_clear_flush_notify(vma, address, page_table);
2180                 page_add_new_anon_rmap(new_page, vma, address, false);
2181                 mem_cgroup_commit_charge(new_page, memcg, false, false);
2182                 lru_cache_add_active_or_unevictable(new_page, vma);
2183                 /*
2184                  * We call the notify macro here because, when using secondary
2185                  * mmu page tables (such as kvm shadow page tables), we want the
2186                  * new page to be mapped directly into the secondary page table.
2187                  */
2188                 set_pte_at_notify(mm, address, page_table, entry);
2189                 update_mmu_cache(vma, address, page_table);
2190                 if (old_page) {
2191                         /*
2192                          * Only after switching the pte to the new page may
2193                          * we remove the mapcount here. Otherwise another
2194                          * process may come and find the rmap count decremented
2195                          * before the pte is switched to the new page, and
2196                          * "reuse" the old page writing into it while our pte
2197                          * here still points into it and can be read by other
2198                          * threads.
2199                          *
2200                          * The critical issue is to order this
2201                          * page_remove_rmap with the ptp_clear_flush above.
2202                          * Those stores are ordered by (if nothing else,)
2203                          * the barrier present in the atomic_add_negative
2204                          * in page_remove_rmap.
2205                          *
2206                          * Then the TLB flush in ptep_clear_flush ensures that
2207                          * no process can access the old page before the
2208                          * decremented mapcount is visible. And the old page
2209                          * cannot be reused until after the decremented
2210                          * mapcount is visible. So transitively, TLBs to
2211                          * old page will be flushed before it can be reused.
2212                          */
2213                         page_remove_rmap(old_page, false);
2214                 }
2215 
2216                 /* Free the old page.. */
2217                 new_page = old_page;
2218                 page_copied = 1;
2219         } else {
2220                 mem_cgroup_cancel_charge(new_page, memcg, false);
2221         }
2222 
2223         if (new_page)
2224                 put_page(new_page);
2225 
2226         pte_unmap_unlock(page_table, ptl);
2227         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2228         if (old_page) {
2229                 /*
2230                  * Don't let another task, with possibly unlocked vma,
2231                  * keep the mlocked page.
2232                  */
2233                 if (page_copied && (vma->vm_flags & VM_LOCKED)) {
2234                         lock_page(old_page);    /* LRU manipulation */
2235                         if (PageMlocked(old_page))
2236                                 munlock_vma_page(old_page);
2237                         unlock_page(old_page);
2238                 }
2239                 put_page(old_page);
2240         }
2241         return page_copied ? VM_FAULT_WRITE : 0;
2242 oom_free_new:
2243         put_page(new_page);
2244 oom:
2245         if (old_page)
2246                 put_page(old_page);
2247         return VM_FAULT_OOM;
2248 }
2249 
2250 /*
2251  * Handle write page faults for VM_MIXEDMAP or VM_PFNMAP for a VM_SHARED
2252  * mapping
2253  */
2254 static int wp_pfn_shared(struct mm_struct *mm,
2255                         struct vm_area_struct *vma, unsigned long address,
2256                         pte_t *page_table, spinlock_t *ptl, pte_t orig_pte,
2257                         pmd_t *pmd)
2258 {
2259         if (vma->vm_ops && vma->vm_ops->pfn_mkwrite) {
2260                 struct vm_fault vmf = {
2261                         .page = NULL,
2262                         .pgoff = linear_page_index(vma, address),
2263                         .virtual_address = (void __user *)(address & PAGE_MASK),
2264                         .flags = FAULT_FLAG_WRITE | FAULT_FLAG_MKWRITE,
2265                 };
2266                 int ret;
2267 
2268                 pte_unmap_unlock(page_table, ptl);
2269                 ret = vma->vm_ops->pfn_mkwrite(vma, &vmf);
2270                 if (ret & VM_FAULT_ERROR)
2271                         return ret;
2272                 page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2273                 /*
2274                  * We might have raced with another page fault while we
2275                  * released the pte_offset_map_lock.
2276                  */
2277                 if (!pte_same(*page_table, orig_pte)) {
2278                         pte_unmap_unlock(page_table, ptl);
2279                         return 0;
2280                 }
2281         }
2282         return wp_page_reuse(mm, vma, address, page_table, ptl, orig_pte,
2283                              NULL, 0, 0);
2284 }
2285 
2286 static int wp_page_shared(struct mm_struct *mm, struct vm_area_struct *vma,
2287                           unsigned long address, pte_t *page_table,
2288                           pmd_t *pmd, spinlock_t *ptl, pte_t orig_pte,
2289                           struct page *old_page)
2290         __releases(ptl)
2291 {
2292         int page_mkwrite = 0;
2293 
2294         get_page(old_page);
2295 
2296         if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
2297                 int tmp;
2298 
2299                 pte_unmap_unlock(page_table, ptl);
2300                 tmp = do_page_mkwrite(vma, old_page, address);
2301                 if (unlikely(!tmp || (tmp &
2302                                       (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
2303                         put_page(old_page);
2304                         return tmp;
2305                 }
2306                 /*
2307                  * Since we dropped the lock we need to revalidate
2308                  * the PTE as someone else may have changed it.  If
2309                  * they did, we just return, as we can count on the
2310                  * MMU to tell us if they didn't also make it writable.
2311                  */
2312                 page_table = pte_offset_map_lock(mm, pmd, address,
2313                                                  &ptl);
2314                 if (!pte_same(*page_table, orig_pte)) {
2315                         unlock_page(old_page);
2316                         pte_unmap_unlock(page_table, ptl);
2317                         put_page(old_page);
2318                         return 0;
2319                 }
2320                 page_mkwrite = 1;
2321         }
2322 
2323         return wp_page_reuse(mm, vma, address, page_table, ptl,
2324                              orig_pte, old_page, page_mkwrite, 1);
2325 }
2326 
2327 /*
2328  * This routine handles present pages, when users try to write
2329  * to a shared page. It is done by copying the page to a new address
2330  * and decrementing the shared-page counter for the old page.
2331  *
2332  * Note that this routine assumes that the protection checks have been
2333  * done by the caller (the low-level page fault routine in most cases).
2334  * Thus we can safely just mark it writable once we've done any necessary
2335  * COW.
2336  *
2337  * We also mark the page dirty at this point even though the page will
2338  * change only once the write actually happens. This avoids a few races,
2339  * and potentially makes it more efficient.
2340  *
2341  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2342  * but allow concurrent faults), with pte both mapped and locked.
2343  * We return with mmap_sem still held, but pte unmapped and unlocked.
2344  */
2345 static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
2346                 unsigned long address, pte_t *page_table, pmd_t *pmd,
2347                 spinlock_t *ptl, pte_t orig_pte)
2348         __releases(ptl)
2349 {
2350         struct page *old_page;
2351 
2352         old_page = vm_normal_page(vma, address, orig_pte);
2353         if (!old_page) {
2354                 /*
2355                  * VM_MIXEDMAP !pfn_valid() case, or VM_SOFTDIRTY clear on a
2356                  * VM_PFNMAP VMA.
2357                  *
2358                  * We should not cow pages in a shared writeable mapping.
2359                  * Just mark the pages writable and/or call ops->pfn_mkwrite.
2360                  */
2361                 if ((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
2362                                      (VM_WRITE|VM_SHARED))
2363                         return wp_pfn_shared(mm, vma, address, page_table, ptl,
2364                                              orig_pte, pmd);
2365 
2366                 pte_unmap_unlock(page_table, ptl);
2367                 return wp_page_copy(mm, vma, address, page_table, pmd,
2368                                     orig_pte, old_page);
2369         }
2370 
2371         /*
2372          * Take out anonymous pages first, anonymous shared vmas are
2373          * not dirty accountable.
2374          */
2375         if (PageAnon(old_page) && !PageKsm(old_page)) {
2376                 int total_mapcount;
2377                 if (!trylock_page(old_page)) {
2378                         get_page(old_page);
2379                         pte_unmap_unlock(page_table, ptl);
2380                         lock_page(old_page);
2381                         page_table = pte_offset_map_lock(mm, pmd, address,
2382                                                          &ptl);
2383                         if (!pte_same(*page_table, orig_pte)) {
2384                                 unlock_page(old_page);
2385                                 pte_unmap_unlock(page_table, ptl);
2386                                 put_page(old_page);
2387                                 return 0;
2388                         }
2389                         put_page(old_page);
2390                 }
2391                 if (reuse_swap_page(old_page, &total_mapcount)) {
2392                         if (total_mapcount == 1) {
2393                                 /*
2394                                  * The page is all ours. Move it to
2395                                  * our anon_vma so the rmap code will
2396                                  * not search our parent or siblings.
2397                                  * Protected against the rmap code by
2398                                  * the page lock.
2399                                  */
2400                                 page_move_anon_rmap(compound_head(old_page),
2401                                                     vma, address);
2402                         }
2403                         unlock_page(old_page);
2404                         return wp_page_reuse(mm, vma, address, page_table, ptl,
2405                                              orig_pte, old_page, 0, 0);
2406                 }
2407                 unlock_page(old_page);
2408         } else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
2409                                         (VM_WRITE|VM_SHARED))) {
2410                 return wp_page_shared(mm, vma, address, page_table, pmd,
2411                                       ptl, orig_pte, old_page);
2412         }
2413 
2414         /*
2415          * Ok, we need to copy. Oh, well..
2416          */
2417         get_page(old_page);
2418 
2419         pte_unmap_unlock(page_table, ptl);
2420         return wp_page_copy(mm, vma, address, page_table, pmd,
2421                             orig_pte, old_page);
2422 }
2423 
2424 static void unmap_mapping_range_vma(struct vm_area_struct *vma,
2425                 unsigned long start_addr, unsigned long end_addr,
2426                 struct zap_details *details)
2427 {
2428         zap_page_range_single(vma, start_addr, end_addr - start_addr, details);
2429 }
2430 
2431 static inline void unmap_mapping_range_tree(struct rb_root *root,
2432                                             struct zap_details *details)
2433 {
2434         struct vm_area_struct *vma;
2435         pgoff_t vba, vea, zba, zea;
2436 
2437         vma_interval_tree_foreach(vma, root,
2438                         details->first_index, details->last_index) {
2439 
2440                 vba = vma->vm_pgoff;
2441                 vea = vba + vma_pages(vma) - 1;
2442                 zba = details->first_index;
2443                 if (zba < vba)
2444                         zba = vba;
2445                 zea = details->last_index;
2446                 if (zea > vea)
2447                         zea = vea;
2448 
2449                 unmap_mapping_range_vma(vma,
2450                         ((zba - vba) << PAGE_SHIFT) + vma->vm_start,
2451                         ((zea - vba + 1) << PAGE_SHIFT) + vma->vm_start,
2452                                 details);
2453         }
2454 }
2455 
2456 /**
2457  * unmap_mapping_range - unmap the portion of all mmaps in the specified
2458  * address_space corresponding to the specified page range in the underlying
2459  * file.
2460  *
2461  * @mapping: the address space containing mmaps to be unmapped.
2462  * @holebegin: byte in first page to unmap, relative to the start of
2463  * the underlying file.  This will be rounded down to a PAGE_SIZE
2464  * boundary.  Note that this is different from truncate_pagecache(), which
2465  * must keep the partial page.  In contrast, we must get rid of
2466  * partial pages.
2467  * @holelen: size of prospective hole in bytes.  This will be rounded
2468  * up to a PAGE_SIZE boundary.  A holelen of zero truncates to the
2469  * end of the file.
2470  * @even_cows: 1 when truncating a file, unmap even private COWed pages;
2471  * but 0 when invalidating pagecache, don't throw away private data.
2472  */
2473 void unmap_mapping_range(struct address_space *mapping,
2474                 loff_t const holebegin, loff_t const holelen, int even_cows)
2475 {
2476         struct zap_details details = { };
2477         pgoff_t hba = holebegin >> PAGE_SHIFT;
2478         pgoff_t hlen = (holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
2479 
2480         /* Check for overflow. */
2481         if (sizeof(holelen) > sizeof(hlen)) {
2482                 long long holeend =
2483                         (holebegin + holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
2484                 if (holeend & ~(long long)ULONG_MAX)
2485                         hlen = ULONG_MAX - hba + 1;
2486         }
2487 
2488         details.check_mapping = even_cows? NULL: mapping;
2489         details.first_index = hba;
2490         details.last_index = hba + hlen - 1;
2491         if (details.last_index < details.first_index)
2492                 details.last_index = ULONG_MAX;
2493 
2494 
2495         /* DAX uses i_mmap_lock to serialise file truncate vs page fault */
2496         i_mmap_lock_write(mapping);
2497         if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap)))
2498                 unmap_mapping_range_tree(&mapping->i_mmap, &details);
2499         i_mmap_unlock_write(mapping);
2500 }
2501 EXPORT_SYMBOL(unmap_mapping_range);
2502 
2503 /*
2504  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2505  * but allow concurrent faults), and pte mapped but not yet locked.
2506  * We return with pte unmapped and unlocked.
2507  *
2508  * We return with the mmap_sem locked or unlocked in the same cases
2509  * as does filemap_fault().
2510  */
2511 static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
2512                 unsigned long address, pte_t *page_table, pmd_t *pmd,
2513                 unsigned int flags, pte_t orig_pte)
2514 {
2515         spinlock_t *ptl;
2516         struct page *page, *swapcache;
2517         struct mem_cgroup *memcg;
2518         swp_entry_t entry;
2519         pte_t pte;
2520         int locked;
2521         int exclusive = 0;
2522         int ret = 0;
2523 
2524         if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
2525                 goto out;
2526 
2527         entry = pte_to_swp_entry(orig_pte);
2528         if (unlikely(non_swap_entry(entry))) {
2529                 if (is_migration_entry(entry)) {
2530                         migration_entry_wait(mm, pmd, address);
2531                 } else if (is_hwpoison_entry(entry)) {
2532                         ret = VM_FAULT_HWPOISON;
2533                 } else {
2534                         print_bad_pte(vma, address, orig_pte, NULL);
2535                         ret = VM_FAULT_SIGBUS;
2536                 }
2537                 goto out;
2538         }
2539         delayacct_set_flag(DELAYACCT_PF_SWAPIN);
2540         page = lookup_swap_cache(entry);
2541         if (!page) {
2542                 page = swapin_readahead(entry,
2543                                         GFP_HIGHUSER_MOVABLE, vma, address);
2544                 if (!page) {
2545                         /*
2546                          * Back out if somebody else faulted in this pte
2547                          * while we released the pte lock.
2548                          */
2549                         page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2550                         if (likely(pte_same(*page_table, orig_pte)))
2551                                 ret = VM_FAULT_OOM;
2552                         delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
2553                         goto unlock;
2554                 }
2555 
2556                 /* Had to read the page from swap area: Major fault */
2557                 ret = VM_FAULT_MAJOR;
2558                 count_vm_event(PGMAJFAULT);
2559                 mem_cgroup_count_vm_event(mm, PGMAJFAULT);
2560         } else if (PageHWPoison(page)) {
2561                 /*
2562                  * hwpoisoned dirty swapcache pages are kept for killing
2563                  * owner processes (which may be unknown at hwpoison time)
2564                  */
2565                 ret = VM_FAULT_HWPOISON;
2566                 delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
2567                 swapcache = page;
2568                 goto out_release;
2569         }
2570 
2571         swapcache = page;
2572         locked = lock_page_or_retry(page, mm, flags);
2573 
2574         delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
2575         if (!locked) {
2576                 ret |= VM_FAULT_RETRY;
2577                 goto out_release;
2578         }
2579 
2580         /*
2581          * Make sure try_to_free_swap or reuse_swap_page or swapoff did not
2582          * release the swapcache from under us.  The page pin, and pte_same
2583          * test below, are not enough to exclude that.  Even if it is still
2584          * swapcache, we need to check that the page's swap has not changed.
2585          */
2586         if (unlikely(!PageSwapCache(page) || page_private(page) != entry.val))
2587                 goto out_page;
2588 
2589         page = ksm_might_need_to_copy(page, vma, address);
2590         if (unlikely(!page)) {
2591                 ret = VM_FAULT_OOM;
2592                 page = swapcache;
2593                 goto out_page;
2594         }
2595 
2596         if (mem_cgroup_try_charge(page, mm, GFP_KERNEL, &memcg, false)) {
2597                 ret = VM_FAULT_OOM;
2598                 goto out_page;
2599         }
2600 
2601         /*
2602          * Back out if somebody else already faulted in this pte.
2603          */
2604         page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2605         if (unlikely(!pte_same(*page_table, orig_pte)))
2606                 goto out_nomap;
2607 
2608         if (unlikely(!PageUptodate(page))) {
2609                 ret = VM_FAULT_SIGBUS;
2610                 goto out_nomap;
2611         }
2612 
2613         /*
2614          * The page isn't present yet, go ahead with the fault.
2615          *
2616          * Be careful about the sequence of operations here.
2617          * To get its accounting right, reuse_swap_page() must be called
2618          * while the page is counted on swap but not yet in mapcount i.e.
2619          * before page_add_anon_rmap() and swap_free(); try_to_free_swap()
2620          * must be called after the swap_free(), or it will never succeed.
2621          */
2622 
2623         inc_mm_counter_fast(mm, MM_ANONPAGES);
2624         dec_mm_counter_fast(mm, MM_SWAPENTS);
2625         pte = mk_pte(page, vma->vm_page_prot);
2626         if ((flags & FAULT_FLAG_WRITE) && reuse_swap_page(page, NULL)) {
2627                 pte = maybe_mkwrite(pte_mkdirty(pte), vma);
2628                 flags &= ~FAULT_FLAG_WRITE;
2629                 ret |= VM_FAULT_WRITE;
2630                 exclusive = RMAP_EXCLUSIVE;
2631         }
2632         flush_icache_page(vma, page);
2633         if (pte_swp_soft_dirty(orig_pte))
2634                 pte = pte_mksoft_dirty(pte);
2635         set_pte_at(mm, address, page_table, pte);
2636         if (page == swapcache) {
2637                 do_page_add_anon_rmap(page, vma, address, exclusive);
2638                 mem_cgroup_commit_charge(page, memcg, true, false);
2639         } else { /* ksm created a completely new copy */
2640                 page_add_new_anon_rmap(page, vma, address, false);
2641                 mem_cgroup_commit_charge(page, memcg, false, false);
2642                 lru_cache_add_active_or_unevictable(page, vma);
2643         }
2644 
2645         swap_free(entry);
2646         if (mem_cgroup_swap_full(page) ||
2647             (vma->vm_flags & VM_LOCKED) || PageMlocked(page))
2648                 try_to_free_swap(page);
2649         unlock_page(page);
2650         if (page != swapcache) {
2651                 /*
2652                  * Hold the lock to avoid the swap entry to be reused
2653                  * until we take the PT lock for the pte_same() check
2654                  * (to avoid false positives from pte_same). For
2655                  * further safety release the lock after the swap_free
2656                  * so that the swap count won't change under a
2657                  * parallel locked swapcache.
2658                  */
2659                 unlock_page(swapcache);
2660                 put_page(swapcache);
2661         }
2662 
2663         if (flags & FAULT_FLAG_WRITE) {
2664                 ret |= do_wp_page(mm, vma, address, page_table, pmd, ptl, pte);
2665                 if (ret & VM_FAULT_ERROR)
2666                         ret &= VM_FAULT_ERROR;
2667                 goto out;
2668         }
2669 
2670         /* No need to invalidate - it was non-present before */
2671         update_mmu_cache(vma, address, page_table);
2672 unlock:
2673         pte_unmap_unlock(page_table, ptl);
2674 out:
2675         return ret;
2676 out_nomap:
2677         mem_cgroup_cancel_charge(page, memcg, false);
2678         pte_unmap_unlock(page_table, ptl);
2679 out_page:
2680         unlock_page(page);
2681 out_release:
2682         put_page(page);
2683         if (page != swapcache) {
2684                 unlock_page(swapcache);
2685                 put_page(swapcache);
2686         }
2687         return ret;
2688 }
2689 
2690 /*
2691  * This is like a special single-page "expand_{down|up}wards()",
2692  * except we must first make sure that 'address{-|+}PAGE_SIZE'
2693  * doesn't hit another vma.
2694  */
2695 static inline int check_stack_guard_page(struct vm_area_struct *vma, unsigned long address)
2696 {
2697         address &= PAGE_MASK;
2698         if ((vma->vm_flags & VM_GROWSDOWN) && address == vma->vm_start) {
2699                 struct vm_area_struct *prev = vma->vm_prev;
2700 
2701                 /*
2702                  * Is there a mapping abutting this one below?
2703                  *
2704                  * That's only ok if it's the same stack mapping
2705                  * that has gotten split..
2706                  */
2707                 if (prev && prev->vm_end == address)
2708                         return prev->vm_flags & VM_GROWSDOWN ? 0 : -ENOMEM;
2709 
2710                 return expand_downwards(vma, address - PAGE_SIZE);
2711         }
2712         if ((vma->vm_flags & VM_GROWSUP) && address + PAGE_SIZE == vma->vm_end) {
2713                 struct vm_area_struct *next = vma->vm_next;
2714 
2715                 /* As VM_GROWSDOWN but s/below/above/ */
2716                 if (next && next->vm_start == address + PAGE_SIZE)
2717                         return next->vm_flags & VM_GROWSUP ? 0 : -ENOMEM;
2718 
2719                 return expand_upwards(vma, address + PAGE_SIZE);
2720         }
2721         return 0;
2722 }
2723 
2724 /*
2725  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2726  * but allow concurrent faults), and pte mapped but not yet locked.
2727  * We return with mmap_sem still held, but pte unmapped and unlocked.
2728  */
2729 static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
2730                 unsigned long address, pte_t *page_table, pmd_t *pmd,
2731                 unsigned int flags)
2732 {
2733         struct mem_cgroup *memcg;
2734         struct page *page;
2735         spinlock_t *ptl;
2736         pte_t entry;
2737 
2738         pte_unmap(page_table);
2739 
2740         /* File mapping without ->vm_ops ? */
2741         if (vma->vm_flags & VM_SHARED)
2742                 return VM_FAULT_SIGBUS;
2743 
2744         /* Check if we need to add a guard page to the stack */
2745         if (check_stack_guard_page(vma, address) < 0)
2746                 return VM_FAULT_SIGSEGV;
2747 
2748         /* Use the zero-page for reads */
2749         if (!(flags & FAULT_FLAG_WRITE) && !mm_forbids_zeropage(mm)) {
2750                 entry = pte_mkspecial(pfn_pte(my_zero_pfn(address),
2751                                                 vma->vm_page_prot));
2752                 page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2753                 if (!pte_none(*page_table))
2754                         goto unlock;
2755                 /* Deliver the page fault to userland, check inside PT lock */
2756                 if (userfaultfd_missing(vma)) {
2757                         pte_unmap_unlock(page_table, ptl);
2758                         return handle_userfault(vma, address, flags,
2759                                                 VM_UFFD_MISSING);
2760                 }
2761                 goto setpte;
2762         }
2763 
2764         /* Allocate our own private page. */
2765         if (unlikely(anon_vma_prepare(vma)))
2766                 goto oom;
2767         page = alloc_zeroed_user_highpage_movable(vma, address);
2768         if (!page)
2769                 goto oom;
2770 
2771         if (mem_cgroup_try_charge(page, mm, GFP_KERNEL, &memcg, false))
2772                 goto oom_free_page;
2773 
2774         /*
2775          * The memory barrier inside __SetPageUptodate makes sure that
2776          * preceeding stores to the page contents become visible before
2777          * the set_pte_at() write.
2778          */
2779         __SetPageUptodate(page);
2780 
2781         entry = mk_pte(page, vma->vm_page_prot);
2782         if (vma->vm_flags & VM_WRITE)
2783                 entry = pte_mkwrite(pte_mkdirty(entry));
2784 
2785         page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2786         if (!pte_none(*page_table))
2787                 goto release;
2788 
2789         /* Deliver the page fault to userland, check inside PT lock */
2790         if (userfaultfd_missing(vma)) {
2791                 pte_unmap_unlock(page_table, ptl);
2792                 mem_cgroup_cancel_charge(page, memcg, false);
2793                 put_page(page);
2794                 return handle_userfault(vma, address, flags,
2795                                         VM_UFFD_MISSING);
2796         }
2797 
2798         inc_mm_counter_fast(mm, MM_ANONPAGES);
2799         page_add_new_anon_rmap(page, vma, address, false);
2800         mem_cgroup_commit_charge(page, memcg, false, false);
2801         lru_cache_add_active_or_unevictable(page, vma);
2802 setpte:
2803         set_pte_at(mm, address, page_table, entry);
2804 
2805         /* No need to invalidate - it was non-present before */
2806         update_mmu_cache(vma, address, page_table);
2807 unlock:
2808         pte_unmap_unlock(page_table, ptl);
2809         return 0;
2810 release:
2811         mem_cgroup_cancel_charge(page, memcg, false);
2812         put_page(page);
2813         goto unlock;
2814 oom_free_page:
2815         put_page(page);
2816 oom:
2817         return VM_FAULT_OOM;
2818 }
2819 
2820 /*
2821  * The mmap_sem must have been held on entry, and may have been
2822  * released depending on flags and vma->vm_ops->fault() return value.
2823  * See filemap_fault() and __lock_page_retry().
2824  */
2825 static int __do_fault(struct vm_area_struct *vma, unsigned long address,
2826                         pgoff_t pgoff, unsigned int flags,
2827                         struct page *cow_page, struct page **page)
2828 {
2829         struct vm_fault vmf;
2830         int ret;
2831 
2832         vmf.virtual_address = (void __user *)(address & PAGE_MASK);
2833         vmf.pgoff = pgoff;
2834         vmf.flags = flags;
2835         vmf.page = NULL;
2836         vmf.gfp_mask = __get_fault_gfp_mask(vma);
2837         vmf.cow_page = cow_page;
2838 
2839         ret = vma->vm_ops->fault(vma, &vmf);
2840         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
2841                 return ret;
2842         if (!vmf.page)
2843                 goto out;
2844 
2845         if (unlikely(PageHWPoison(vmf.page))) {
2846                 if (ret & VM_FAULT_LOCKED)
2847                         unlock_page(vmf.page);
2848                 put_page(vmf.page);
2849                 return VM_FAULT_HWPOISON;
2850         }
2851 
2852         if (unlikely(!(ret & VM_FAULT_LOCKED)))
2853                 lock_page(vmf.page);
2854         else
2855                 VM_BUG_ON_PAGE(!PageLocked(vmf.page), vmf.page);
2856 
2857  out:
2858         *page = vmf.page;
2859         return ret;
2860 }
2861 
2862 /**
2863  * do_set_pte - setup new PTE entry for given page and add reverse page mapping.
2864  *
2865  * @vma: virtual memory area
2866  * @address: user virtual address
2867  * @page: page to map
2868  * @pte: pointer to target page table entry
2869  * @write: true, if new entry is writable
2870  * @anon: true, if it's anonymous page
2871  *
2872  * Caller must hold page table lock relevant for @pte.
2873  *
2874  * Target users are page handler itself and implementations of
2875  * vm_ops->map_pages.
2876  */
2877 void do_set_pte(struct vm_area_struct *vma, unsigned long address,
2878                 struct page *page, pte_t *pte, bool write, bool anon)
2879 {
2880         pte_t entry;
2881 
2882         flush_icache_page(vma, page);
2883         entry = mk_pte(page, vma->vm_page_prot);
2884         if (write)
2885                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2886         if (anon) {
2887                 inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
2888                 page_add_new_anon_rmap(page, vma, address, false);
2889         } else {
2890                 inc_mm_counter_fast(vma->vm_mm, mm_counter_file(page));
2891                 page_add_file_rmap(page);
2892         }
2893         set_pte_at(vma->vm_mm, address, pte, entry);
2894 
2895         /* no need to invalidate: a not-present page won't be cached */
2896         update_mmu_cache(vma, address, pte);
2897 }
2898 
2899 static unsigned long fault_around_bytes __read_mostly =
2900         rounddown_pow_of_two(65536);
2901 
2902 #ifdef CONFIG_DEBUG_FS
2903 static int fault_around_bytes_get(void *data, u64 *val)
2904 {
2905         *val = fault_around_bytes;
2906         return 0;
2907 }
2908 
2909 /*
2910  * fault_around_pages() and fault_around_mask() expects fault_around_bytes
2911  * rounded down to nearest page order. It's what do_fault_around() expects to
2912  * see.
2913  */
2914 static int fault_around_bytes_set(void *data, u64 val)
2915 {
2916         if (val / PAGE_SIZE > PTRS_PER_PTE)
2917                 return -EINVAL;
2918         if (val > PAGE_SIZE)
2919                 fault_around_bytes = rounddown_pow_of_two(val);
2920         else
2921                 fault_around_bytes = PAGE_SIZE; /* rounddown_pow_of_two(0) is undefined */
2922         return 0;
2923 }
2924 DEFINE_SIMPLE_ATTRIBUTE(fault_around_bytes_fops,
2925                 fault_around_bytes_get, fault_around_bytes_set, "%llu\n");
2926 
2927 static int __init fault_around_debugfs(void)
2928 {
2929         void *ret;
2930 
2931         ret = debugfs_create_file("fault_around_bytes", 0644, NULL, NULL,
2932                         &fault_around_bytes_fops);
2933         if (!ret)
2934                 pr_warn("Failed to create fault_around_bytes in debugfs");
2935         return 0;
2936 }
2937 late_initcall(fault_around_debugfs);
2938 #endif
2939 
2940 /*
2941  * do_fault_around() tries to map few pages around the fault address. The hope
2942  * is that the pages will be needed soon and this will lower the number of
2943  * faults to handle.
2944  *
2945  * It uses vm_ops->map_pages() to map the pages, which skips the page if it's
2946  * not ready to be mapped: not up-to-date, locked, etc.
2947  *
2948  * This function is called with the page table lock taken. In the split ptlock
2949  * case the page table lock only protects only those entries which belong to
2950  * the page table corresponding to the fault address.
2951  *
2952  * This function doesn't cross the VMA boundaries, in order to call map_pages()
2953  * only once.
2954  *
2955  * fault_around_pages() defines how many pages we'll try to map.
2956  * do_fault_around() expects it to return a power of two less than or equal to
2957  * PTRS_PER_PTE.
2958  *
2959  * The virtual address of the area that we map is naturally aligned to the
2960  * fault_around_pages() value (and therefore to page order).  This way it's
2961  * easier to guarantee that we don't cross page table boundaries.
2962  */
2963 static void do_fault_around(struct vm_area_struct *vma, unsigned long address,
2964                 pte_t *pte, pgoff_t pgoff, unsigned int flags)
2965 {
2966         unsigned long start_addr, nr_pages, mask;
2967         pgoff_t max_pgoff;
2968         struct vm_fault vmf;
2969         int off;
2970 
2971         nr_pages = READ_ONCE(fault_around_bytes) >> PAGE_SHIFT;
2972         mask = ~(nr_pages * PAGE_SIZE - 1) & PAGE_MASK;
2973 
2974         start_addr = max(address & mask, vma->vm_start);
2975         off = ((address - start_addr) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
2976         pte -= off;
2977         pgoff -= off;
2978 
2979         /*
2980          *  max_pgoff is either end of page table or end of vma
2981          *  or fault_around_pages() from pgoff, depending what is nearest.
2982          */
2983         max_pgoff = pgoff - ((start_addr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1)) +
2984                 PTRS_PER_PTE - 1;
2985         max_pgoff = min3(max_pgoff, vma_pages(vma) + vma->vm_pgoff - 1,
2986                         pgoff + nr_pages - 1);
2987 
2988         /* Check if it makes any sense to call ->map_pages */
2989         while (!pte_none(*pte)) {
2990                 if (++pgoff > max_pgoff)
2991                         return;
2992                 start_addr += PAGE_SIZE;
2993                 if (start_addr >= vma->vm_end)
2994                         return;
2995                 pte++;
2996         }
2997 
2998         vmf.virtual_address = (void __user *) start_addr;
2999         vmf.pte = pte;
3000         vmf.pgoff = pgoff;
3001         vmf.max_pgoff = max_pgoff;
3002         vmf.flags = flags;
3003         vmf.gfp_mask = __get_fault_gfp_mask(vma);
3004         vma->vm_ops->map_pages(vma, &vmf);
3005 }
3006 
3007 static int do_read_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3008                 unsigned long address, pmd_t *pmd,
3009                 pgoff_t pgoff, unsigned int flags, pte_t orig_pte)
3010 {
3011         struct page *fault_page;
3012         spinlock_t *ptl;
3013         pte_t *pte;
3014         int ret = 0;
3015 
3016         /*
3017          * Let's call ->map_pages() first and use ->fault() as fallback
3018          * if page by the offset is not ready to be mapped (cold cache or
3019          * something).
3020          */
3021         if (vma->vm_ops->map_pages && fault_around_bytes >> PAGE_SHIFT > 1) {
3022                 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
3023                 do_fault_around(vma, address, pte, pgoff, flags);
3024                 if (!pte_same(*pte, orig_pte))
3025                         goto unlock_out;
3026                 pte_unmap_unlock(pte, ptl);
3027         }
3028 
3029         ret = __do_fault(vma, address, pgoff, flags, NULL, &fault_page);
3030         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
3031                 return ret;
3032 
3033         pte = pte_offset_map_lock(mm, pmd, address, &ptl);
3034         if (unlikely(!pte_same(*pte, orig_pte))) {
3035                 pte_unmap_unlock(pte, ptl);
3036                 unlock_page(fault_page);
3037                 put_page(fault_page);
3038                 return ret;
3039         }
3040         do_set_pte(vma, address, fault_page, pte, false, false);
3041         unlock_page(fault_page);
3042 unlock_out:
3043         pte_unmap_unlock(pte, ptl);
3044         return ret;
3045 }
3046 
3047 static int do_cow_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3048                 unsigned long address, pmd_t *pmd,
3049                 pgoff_t pgoff, unsigned int flags, pte_t orig_pte)
3050 {
3051         struct page *fault_page, *new_page;
3052         struct mem_cgroup *memcg;
3053         spinlock_t *ptl;
3054         pte_t *pte;
3055         int ret;
3056 
3057         if (unlikely(anon_vma_prepare(vma)))
3058                 return VM_FAULT_OOM;
3059 
3060         new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
3061         if (!new_page)
3062                 return VM_FAULT_OOM;
3063 
3064         if (mem_cgroup_try_charge(new_page, mm, GFP_KERNEL, &memcg, false)) {
3065                 put_page(new_page);
3066                 return VM_FAULT_OOM;
3067         }
3068 
3069         ret = __do_fault(vma, address, pgoff, flags, new_page, &fault_page);
3070         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
3071                 goto uncharge_out;
3072 
3073         if (fault_page)
3074                 copy_user_highpage(new_page, fault_page, address, vma);
3075         __SetPageUptodate(new_page);
3076 
3077         pte = pte_offset_map_lock(mm, pmd, address, &ptl);
3078         if (unlikely(!pte_same(*pte, orig_pte))) {
3079                 pte_unmap_unlock(pte, ptl);
3080                 if (fault_page) {
3081                         unlock_page(fault_page);
3082                         put_page(fault_page);
3083                 } else {
3084                         /*
3085                          * The fault handler has no page to lock, so it holds
3086                          * i_mmap_lock for read to protect against truncate.
3087                          */
3088                         i_mmap_unlock_read(vma->vm_file->f_mapping);
3089                 }
3090                 goto uncharge_out;
3091         }
3092         do_set_pte(vma, address, new_page, pte, true, true);
3093         mem_cgroup_commit_charge(new_page, memcg, false, false);
3094         lru_cache_add_active_or_unevictable(new_page, vma);
3095         pte_unmap_unlock(pte, ptl);
3096         if (fault_page) {
3097                 unlock_page(fault_page);
3098                 put_page(fault_page);
3099         } else {
3100                 /*
3101                  * The fault handler has no page to lock, so it holds
3102                  * i_mmap_lock for read to protect against truncate.
3103                  */
3104                 i_mmap_unlock_read(vma->vm_file->f_mapping);
3105         }
3106         return ret;
3107 uncharge_out:
3108         mem_cgroup_cancel_charge(new_page, memcg, false);
3109         put_page(new_page);
3110         return ret;
3111 }
3112 
3113 static int do_shared_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3114                 unsigned long address, pmd_t *pmd,
3115                 pgoff_t pgoff, unsigned int flags, pte_t orig_pte)
3116 {
3117         struct page *fault_page;
3118         struct address_space *mapping;
3119         spinlock_t *ptl;
3120         pte_t *pte;
3121         int dirtied = 0;
3122         int ret, tmp;
3123 
3124         ret = __do_fault(vma, address, pgoff, flags, NULL, &fault_page);
3125         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
3126                 return ret;
3127 
3128         /*
3129          * Check if the backing address space wants to know that the page is
3130          * about to become writable
3131          */
3132         if (vma->vm_ops->page_mkwrite) {
3133                 unlock_page(fault_page);
3134                 tmp = do_page_mkwrite(vma, fault_page, address);
3135                 if (unlikely(!tmp ||
3136                                 (tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
3137                         put_page(fault_page);
3138                         return tmp;
3139                 }
3140         }
3141 
3142         pte = pte_offset_map_lock(mm, pmd, address, &ptl);
3143         if (unlikely(!pte_same(*pte, orig_pte))) {
3144                 pte_unmap_unlock(pte, ptl);
3145                 unlock_page(fault_page);
3146                 put_page(fault_page);
3147                 return ret;
3148         }
3149         do_set_pte(vma, address, fault_page, pte, true, false);
3150         pte_unmap_unlock(pte, ptl);
3151 
3152         if (set_page_dirty(fault_page))
3153                 dirtied = 1;
3154         /*
3155          * Take a local copy of the address_space - page.mapping may be zeroed
3156          * by truncate after unlock_page().   The address_space itself remains
3157          * pinned by vma->vm_file's reference.  We rely on unlock_page()'s
3158          * release semantics to prevent the compiler from undoing this copying.
3159          */
3160         mapping = page_rmapping(fault_page);
3161         unlock_page(fault_page);
3162         if ((dirtied || vma->vm_ops->page_mkwrite) && mapping) {
3163                 /*
3164                  * Some device drivers do not set page.mapping but still
3165                  * dirty their pages
3166                  */
3167                 balance_dirty_pages_ratelimited(mapping);
3168         }
3169 
3170         if (!vma->vm_ops->page_mkwrite)
3171                 file_update_time(vma->vm_file);
3172 
3173         return ret;
3174 }
3175 
3176 /*
3177  * We enter with non-exclusive mmap_sem (to exclude vma changes,
3178  * but allow concurrent faults).
3179  * The mmap_sem may have been released depending on flags and our
3180  * return value.  See filemap_fault() and __lock_page_or_retry().
3181  */
3182 static int do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3183                 unsigned long address, pte_t *page_table, pmd_t *pmd,
3184                 unsigned int flags, pte_t orig_pte)
3185 {
3186         pgoff_t pgoff = linear_page_index(vma, address);
3187 
3188         pte_unmap(page_table);
3189         /* The VMA was not fully populated on mmap() or missing VM_DONTEXPAND */
3190         if (!vma->vm_ops->fault)
3191                 return VM_FAULT_SIGBUS;
3192         if (!(flags & FAULT_FLAG_WRITE))
3193                 return do_read_fault(mm, vma, address, pmd, pgoff, flags,
3194                                 orig_pte);
3195         if (!(vma->vm_flags & VM_SHARED))
3196                 return do_cow_fault(mm, vma, address, pmd, pgoff, flags,
3197                                 orig_pte);
3198         return do_shared_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
3199 }
3200 
3201 static int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,
3202                                 unsigned long addr, int page_nid,
3203                                 int *flags)
3204 {
3205         get_page(page);
3206 
3207         count_vm_numa_event(NUMA_HINT_FAULTS);
3208         if (page_nid == numa_node_id()) {
3209                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
3210                 *flags |= TNF_FAULT_LOCAL;
3211         }
3212 
3213         return mpol_misplaced(page, vma, addr);
3214 }
3215 
3216 static int do_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
3217                    unsigned long addr, pte_t pte, pte_t *ptep, pmd_t *pmd)
3218 {
3219         struct page *page = NULL;
3220         spinlock_t *ptl;
3221         int page_nid = -1;
3222         int last_cpupid;
3223         int target_nid;
3224         bool migrated = false;
3225         bool was_writable = pte_write(pte);
3226         int flags = 0;
3227 
3228         /* A PROT_NONE fault should not end up here */
3229         BUG_ON(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)));
3230 
3231         /*
3232         * The "pte" at this point cannot be used safely without
3233         * validation through pte_unmap_same(). It's of NUMA type but
3234         * the pfn may be screwed if the read is non atomic.
3235         *
3236         * We can safely just do a "set_pte_at()", because the old
3237         * page table entry is not accessible, so there would be no
3238         * concurrent hardware modifications to the PTE.
3239         */
3240         ptl = pte_lockptr(mm, pmd);
3241         spin_lock(ptl);
3242         if (unlikely(!pte_same(*ptep, pte))) {
3243                 pte_unmap_unlock(ptep, ptl);
3244                 goto out;
3245         }
3246 
3247         /* Make it present again */
3248         pte = pte_modify(pte, vma->vm_page_prot);
3249         pte = pte_mkyoung(pte);
3250         if (was_writable)
3251                 pte = pte_mkwrite(pte);
3252         set_pte_at(mm, addr, ptep, pte);
3253         update_mmu_cache(vma, addr, ptep);
3254 
3255         page = vm_normal_page(vma, addr, pte);
3256         if (!page) {
3257                 pte_unmap_unlock(ptep, ptl);
3258                 return 0;
3259         }
3260 
3261         /* TODO: handle PTE-mapped THP */
3262         if (PageCompound(page)) {
3263                 pte_unmap_unlock(ptep, ptl);
3264                 return 0;
3265         }
3266 
3267         /*
3268          * Avoid grouping on RO pages in general. RO pages shouldn't hurt as
3269          * much anyway since they can be in shared cache state. This misses
3270          * the case where a mapping is writable but the process never writes
3271          * to it but pte_write gets cleared during protection updates and
3272          * pte_dirty has unpredictable behaviour between PTE scan updates,
3273          * background writeback, dirty balancing and application behaviour.
3274          */
3275         if (!(vma->vm_flags & VM_WRITE))
3276                 flags |= TNF_NO_GROUP;
3277 
3278         /*
3279          * Flag if the page is shared between multiple address spaces. This
3280          * is later used when determining whether to group tasks together
3281          */
3282         if (page_mapcount(page) > 1 && (vma->vm_flags & VM_SHARED))
3283                 flags |= TNF_SHARED;
3284 
3285         last_cpupid = page_cpupid_last(page);
3286         page_nid = page_to_nid(page);
3287         target_nid = numa_migrate_prep(page, vma, addr, page_nid, &flags);
3288         pte_unmap_unlock(ptep, ptl);
3289         if (target_nid == -1) {
3290                 put_page(page);
3291                 goto out;
3292         }
3293 
3294         /* Migrate to the requested node */
3295         migrated = migrate_misplaced_page(page, vma, target_nid);
3296         if (migrated) {
3297                 page_nid = target_nid;
3298                 flags |= TNF_MIGRATED;
3299         } else
3300                 flags |= TNF_MIGRATE_FAIL;
3301 
3302 out:
3303         if (page_nid != -1)
3304                 task_numa_fault(last_cpupid, page_nid, 1, flags);
3305         return 0;
3306 }
3307 
3308 static int create_huge_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
3309                         unsigned long address, pmd_t *pmd, unsigned int flags)
3310 {
3311         if (vma_is_anonymous(vma))
3312                 return do_huge_pmd_anonymous_page(mm, vma, address, pmd, flags);
3313         if (vma->vm_ops->pmd_fault)
3314                 return vma->vm_ops->pmd_fault(vma, address, pmd, flags);
3315         return VM_FAULT_FALLBACK;
3316 }
3317 
3318 static int wp_huge_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
3319                         unsigned long address, pmd_t *pmd, pmd_t orig_pmd,
3320                         unsigned int flags)
3321 {
3322         if (vma_is_anonymous(vma))
3323                 return do_huge_pmd_wp_page(mm, vma, address, pmd, orig_pmd);
3324         if (vma->vm_ops->pmd_fault)
3325                 return vma->vm_ops->pmd_fault(vma, address, pmd, flags);
3326         return VM_FAULT_FALLBACK;
3327 }
3328 
3329 /*
3330  * These routines also need to handle stuff like marking pages dirty
3331  * and/or accessed for architectures that don't do it in hardware (most
3332  * RISC architectures).  The early dirtying is also good on the i386.
3333  *
3334  * There is also a hook called "update_mmu_cache()" that architectures
3335  * with external mmu caches can use to update those (ie the Sparc or
3336  * PowerPC hashed page tables that act as extended TLBs).
3337  *
3338  * We enter with non-exclusive mmap_sem (to exclude vma changes,
3339  * but allow concurrent faults), and pte mapped but not yet locked.
3340  * We return with pte unmapped and unlocked.
3341  *
3342  * The mmap_sem may have been released depending on flags and our
3343  * return value.  See filemap_fault() and __lock_page_or_retry().
3344  */
3345 static int handle_pte_fault(struct mm_struct *mm,
3346                      struct vm_area_struct *vma, unsigned long address,
3347                      pte_t *pte, pmd_t *pmd, unsigned int flags)
3348 {
3349         pte_t entry;
3350         spinlock_t *ptl;
3351 
3352         /*
3353          * some architectures can have larger ptes than wordsize,
3354          * e.g.ppc44x-defconfig has CONFIG_PTE_64BIT=y and CONFIG_32BIT=y,
3355          * so READ_ONCE or ACCESS_ONCE cannot guarantee atomic accesses.
3356          * The code below just needs a consistent view for the ifs and
3357          * we later double check anyway with the ptl lock held. So here
3358          * a barrier will do.
3359          */
3360         entry = *pte;
3361         barrier();
3362         if (!pte_present(entry)) {
3363                 if (pte_none(entry)) {
3364                         if (vma_is_anonymous(vma))
3365                                 return do_anonymous_page(mm, vma, address,
3366                                                          pte, pmd, flags);
3367                         else
3368                                 return do_fault(mm, vma, address, pte, pmd,
3369                                                 flags, entry);
3370                 }
3371                 return do_swap_page(mm, vma, address,
3372                                         pte, pmd, flags, entry);
3373         }
3374 
3375         if (pte_protnone(entry))
3376                 return do_numa_page(mm, vma, address, entry, pte, pmd);
3377 
3378         ptl = pte_lockptr(mm, pmd);
3379         spin_lock(ptl);
3380         if (unlikely(!pte_same(*pte, entry)))
3381                 goto unlock;
3382         if (flags & FAULT_FLAG_WRITE) {
3383                 if (!pte_write(entry))
3384                         return do_wp_page(mm, vma, address,
3385                                         pte, pmd, ptl, entry);
3386                 entry = pte_mkdirty(entry);
3387         }
3388         entry = pte_mkyoung(entry);
3389         if (ptep_set_access_flags(vma, address, pte, entry, flags & FAULT_FLAG_WRITE)) {
3390                 update_mmu_cache(vma, address, pte);
3391         } else {
3392                 /*
3393                  * This is needed only for protection faults but the arch code
3394                  * is not yet telling us if this is a protection fault or not.
3395                  * This still avoids useless tlb flushes for .text page faults
3396                  * with threads.
3397                  */
3398                 if (flags & FAULT_FLAG_WRITE)
3399                         flush_tlb_fix_spurious_fault(vma, address);
3400         }
3401 unlock:
3402         pte_unmap_unlock(pte, ptl);
3403         return 0;
3404 }
3405 
3406 /*
3407  * By the time we get here, we already hold the mm semaphore
3408  *
3409  * The mmap_sem may have been released depending on flags and our
3410  * return value.  See filemap_fault() and __lock_page_or_retry().
3411  */
3412 static int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3413                              unsigned long address, unsigned int flags)
3414 {
3415         pgd_t *pgd;
3416         pud_t *pud;
3417         pmd_t *pmd;
3418         pte_t *pte;
3419 
3420         if (!arch_vma_access_permitted(vma, flags & FAULT_FLAG_WRITE,
3421                                             flags & FAULT_FLAG_INSTRUCTION,
3422                                             flags & FAULT_FLAG_REMOTE))
3423                 return VM_FAULT_SIGSEGV;
3424 
3425         if (unlikely(is_vm_hugetlb_page(vma)))
3426                 return hugetlb_fault(mm, vma, address, flags);
3427 
3428         pgd = pgd_offset(mm, address);
3429         pud = pud_alloc(mm, pgd, address);
3430         if (!pud)
3431                 return VM_FAULT_OOM;
3432         pmd = pmd_alloc(mm, pud, address);
3433         if (!pmd)
3434                 return VM_FAULT_OOM;
3435         if (pmd_none(*pmd) && transparent_hugepage_enabled(vma)) {
3436                 int ret = create_huge_pmd(mm, vma, address, pmd, flags);
3437                 if (!(ret & VM_FAULT_FALLBACK))
3438                         return ret;
3439         } else {
3440                 pmd_t orig_pmd = *pmd;
3441                 int ret;
3442 
3443                 barrier();
3444                 if (pmd_trans_huge(orig_pmd) || pmd_devmap(orig_pmd)) {
3445                         unsigned int dirty = flags & FAULT_FLAG_WRITE;
3446 
3447                         if (pmd_protnone(orig_pmd))
3448                                 return do_huge_pmd_numa_page(mm, vma, address,
3449                                                              orig_pmd, pmd);
3450 
3451                         if (dirty && !pmd_write(orig_pmd)) {
3452                                 ret = wp_huge_pmd(mm, vma, address, pmd,
3453                                                         orig_pmd, flags);
3454                                 if (!(ret & VM_FAULT_FALLBACK))
3455                                         return ret;
3456                         } else {
3457                                 huge_pmd_set_accessed(mm, vma, address, pmd,
3458                                                       orig_pmd, dirty);
3459                                 return 0;
3460                         }
3461                 }
3462         }
3463 
3464         /*
3465          * Use pte_alloc() instead of pte_alloc_map, because we can't
3466          * run pte_offset_map on the pmd, if an huge pmd could
3467          * materialize from under us from a different thread.
3468          */
3469         if (unlikely(pte_alloc(mm, pmd, address)))
3470                 return VM_FAULT_OOM;
3471         /*
3472          * If a huge pmd materialized under us just retry later.  Use
3473          * pmd_trans_unstable() instead of pmd_trans_huge() to ensure the pmd
3474          * didn't become pmd_trans_huge under us and then back to pmd_none, as
3475          * a result of MADV_DONTNEED running immediately after a huge pmd fault
3476          * in a different thread of this mm, in turn leading to a misleading
3477          * pmd_trans_huge() retval.  All we have to ensure is that it is a
3478          * regular pmd that we can walk with pte_offset_map() and we can do that
3479          * through an atomic read in C, which is what pmd_trans_unstable()
3480          * provides.
3481          */
3482         if (unlikely(pmd_trans_unstable(pmd) || pmd_devmap(*pmd)))
3483                 return 0;
3484         /*
3485          * A regular pmd is established and it can't morph into a huge pmd
3486          * from under us anymore at this point because we hold the mmap_sem
3487          * read mode and khugepaged takes it in write mode. So now it's
3488          * safe to run pte_offset_map().
3489          */
3490         pte = pte_offset_map(pmd, address);
3491 
3492         return handle_pte_fault(mm, vma, address, pte, pmd, flags);
3493 }
3494 
3495 /*
3496  * By the time we get here, we already hold the mm semaphore
3497  *
3498  * The mmap_sem may have been released depending on flags and our
3499  * return value.  See filemap_fault() and __lock_page_or_retry().
3500  */
3501 int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3502                     unsigned long address, unsigned int flags)
3503 {
3504         int ret;
3505 
3506         __set_current_state(TASK_RUNNING);
3507 
3508         count_vm_event(PGFAULT);
3509         mem_cgroup_count_vm_event(mm, PGFAULT);
3510 
3511         /* do counter updates before entering really critical section. */
3512         check_sync_rss_stat(current);
3513 
3514         /*
3515          * Enable the memcg OOM handling for faults triggered in user
3516          * space.  Kernel faults are handled more gracefully.
3517          */
3518         if (flags & FAULT_FLAG_USER)
3519                 mem_cgroup_oom_enable();
3520 
3521         ret = __handle_mm_fault(mm, vma, address, flags);
3522 
3523         if (flags & FAULT_FLAG_USER) {
3524                 mem_cgroup_oom_disable();
3525                 /*
3526                  * The task may have entered a memcg OOM situation but
3527                  * if the allocation error was handled gracefully (no
3528                  * VM_FAULT_OOM), there is no need to kill anything.
3529                  * Just clean up the OOM state peacefully.
3530                  */
3531                 if (task_in_memcg_oom(current) && !(ret & VM_FAULT_OOM))
3532                         mem_cgroup_oom_synchronize(false);
3533         }
3534 
3535         return ret;
3536 }
3537 EXPORT_SYMBOL_GPL(handle_mm_fault);
3538 
3539 #ifndef __PAGETABLE_PUD_FOLDED
3540 /*
3541  * Allocate page upper directory.
3542  * We've already handled the fast-path in-line.
3543  */
3544 int __pud_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address)
3545 {
3546         pud_t *new = pud_alloc_one(mm, address);
3547         if (!new)
3548                 return -ENOMEM;
3549 
3550         smp_wmb(); /* See comment in __pte_alloc */
3551 
3552         spin_lock(&mm->page_table_lock);
3553         if (pgd_present(*pgd))          /* Another has populated it */
3554                 pud_free(mm, new);
3555         else
3556                 pgd_populate(mm, pgd, new);
3557         spin_unlock(&mm->page_table_lock);
3558         return 0;
3559 }
3560 #endif /* __PAGETABLE_PUD_FOLDED */
3561 
3562 #ifndef __PAGETABLE_PMD_FOLDED
3563 /*
3564  * Allocate page middle directory.
3565  * We've already handled the fast-path in-line.
3566  */
3567 int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address)
3568 {
3569         pmd_t *new = pmd_alloc_one(mm, address);
3570         if (!new)
3571                 return -ENOMEM;
3572 
3573         smp_wmb(); /* See comment in __pte_alloc */
3574 
3575         spin_lock(&mm->page_table_lock);
3576 #ifndef __ARCH_HAS_4LEVEL_HACK
3577         if (!pud_present(*pud)) {
3578                 mm_inc_nr_pmds(mm);
3579                 pud_populate(mm, pud, new);
3580         } else  /* Another has populated it */
3581                 pmd_free(mm, new);
3582 #else
3583         if (!pgd_present(*pud)) {
3584                 mm_inc_nr_pmds(mm);
3585                 pgd_populate(mm, pud, new);
3586         } else /* Another has populated it */
3587                 pmd_free(mm, new);
3588 #endif /* __ARCH_HAS_4LEVEL_HACK */
3589         spin_unlock(&mm->page_table_lock);
3590         return 0;
3591 }
3592 #endif /* __PAGETABLE_PMD_FOLDED */
3593 
3594 static int __follow_pte(struct mm_struct *mm, unsigned long address,
3595                 pte_t **ptepp, spinlock_t **ptlp)
3596 {
3597         pgd_t *pgd;
3598         pud_t *pud;
3599         pmd_t *pmd;
3600         pte_t *ptep;
3601 
3602         pgd = pgd_offset(mm, address);
3603         if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
3604                 goto out;
3605 
3606         pud = pud_offset(pgd, address);
3607         if (pud_none(*pud) || unlikely(pud_bad(*pud)))
3608                 goto out;
3609 
3610         pmd = pmd_offset(pud, address);
3611         VM_BUG_ON(pmd_trans_huge(*pmd));
3612         if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
3613                 goto out;
3614 
3615         /* We cannot handle huge page PFN maps. Luckily they don't exist. */
3616         if (pmd_huge(*pmd))
3617                 goto out;
3618 
3619         ptep = pte_offset_map_lock(mm, pmd, address, ptlp);
3620         if (!ptep)
3621                 goto out;
3622         if (!pte_present(*ptep))
3623                 goto unlock;
3624         *ptepp = ptep;
3625         return 0;
3626 unlock:
3627         pte_unmap_unlock(ptep, *ptlp);
3628 out:
3629         return -EINVAL;
3630 }
3631 
3632 static inline int follow_pte(struct mm_struct *mm, unsigned long address,
3633                              pte_t **ptepp, spinlock_t **ptlp)
3634 {
3635         int res;
3636 
3637         /* (void) is needed to make gcc happy */
3638         (void) __cond_lock(*ptlp,
3639                            !(res = __follow_pte(mm, address, ptepp, ptlp)));
3640         return res;
3641 }
3642 
3643 /**
3644  * follow_pfn - look up PFN at a user virtual address
3645  * @vma: memory mapping
3646  * @address: user virtual address
3647  * @pfn: location to store found PFN
3648  *
3649  * Only IO mappings and raw PFN mappings are allowed.
3650  *
3651  * Returns zero and the pfn at @pfn on success, -ve otherwise.
3652  */
3653 int follow_pfn(struct vm_area_struct *vma, unsigned long address,
3654         unsigned long *pfn)
3655 {
3656         int ret = -EINVAL;
3657         spinlock_t *ptl;
3658         pte_t *ptep;
3659 
3660         if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
3661                 return ret;
3662 
3663         ret = follow_pte(vma->vm_mm, address, &ptep, &ptl);
3664         if (ret)
3665                 return ret;
3666         *pfn = pte_pfn(*ptep);
3667         pte_unmap_unlock(ptep, ptl);
3668         return 0;
3669 }
3670 EXPORT_SYMBOL(follow_pfn);
3671 
3672 #ifdef CONFIG_HAVE_IOREMAP_PROT
3673 int follow_phys(struct vm_area_struct *vma,
3674                 unsigned long address, unsigned int flags,
3675                 unsigned long *prot, resource_size_t *phys)
3676 {
3677         int ret = -EINVAL;
3678         pte_t *ptep, pte;
3679         spinlock_t *ptl;
3680 
3681         if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
3682                 goto out;
3683 
3684         if (follow_pte(vma->vm_mm, address, &ptep, &ptl))
3685                 goto out;
3686         pte = *ptep;
3687 
3688         if ((flags & FOLL_WRITE) && !pte_write(pte))
3689                 goto unlock;
3690 
3691         *prot = pgprot_val(pte_pgprot(pte));
3692         *phys = (resource_size_t)pte_pfn(pte) << PAGE_SHIFT;
3693 
3694         ret = 0;
3695 unlock:
3696         pte_unmap_unlock(ptep, ptl);
3697 out:
3698         return ret;
3699 }
3700 
3701 int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
3702                         void *buf, int len, int write)
3703 {
3704         resource_size_t phys_addr;
3705         unsigned long prot = 0;
3706         void __iomem *maddr;
3707         int offset = addr & (PAGE_SIZE-1);
3708 
3709         if (follow_phys(vma, addr, write, &prot, &phys_addr))
3710                 return -EINVAL;
3711 
3712         maddr = ioremap_prot(phys_addr, PAGE_ALIGN(len + offset), prot);
3713         if (write)
3714                 memcpy_toio(maddr + offset, buf, len);
3715         else
3716                 memcpy_fromio(buf, maddr + offset, len);
3717         iounmap(maddr);
3718 
3719         return len;
3720 }
3721 EXPORT_SYMBOL_GPL(generic_access_phys);
3722 #endif
3723 
3724 /*
3725  * Access another process' address space as given in mm.  If non-NULL, use the
3726  * given task for page fault accounting.
3727  */
3728 static int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
3729                 unsigned long addr, void *buf, int len, int write)
3730 {
3731         struct vm_area_struct *vma;
3732         void *old_buf = buf;
3733 
3734         down_read(&mm->mmap_sem);
3735         /* ignore errors, just check how much was successfully transferred */
3736         while (len) {
3737                 int bytes, ret, offset;
3738                 void *maddr;
3739                 struct page *page = NULL;
3740 
3741                 ret = get_user_pages_remote(tsk, mm, addr, 1,
3742                                 write, 1, &page, &vma);
3743                 if (ret <= 0) {
3744 #ifndef CONFIG_HAVE_IOREMAP_PROT
3745                         break;
3746 #else
3747                         /*
3748                          * Check if this is a VM_IO | VM_PFNMAP VMA, which
3749                          * we can access using slightly different code.
3750                          */
3751                         vma = find_vma(mm, addr);
3752                         if (!vma || vma->vm_start > addr)
3753                                 break;
3754                         if (vma->vm_ops && vma->vm_ops->access)
3755                                 ret = vma->vm_ops->access(vma, addr, buf,
3756                                                           len, write);
3757                         if (ret <= 0)
3758                                 break;
3759                         bytes = ret;
3760 #endif
3761                 } else {
3762                         bytes = len;
3763                         offset = addr & (PAGE_SIZE-1);
3764                         if (bytes > PAGE_SIZE-offset)
3765                                 bytes = PAGE_SIZE-offset;
3766 
3767                         maddr = kmap(page);
3768                         if (write) {
3769                                 copy_to_user_page(vma, page, addr,
3770                                                   maddr + offset, buf, bytes);
3771                                 set_page_dirty_lock(page);
3772                         } else {
3773                                 copy_from_user_page(vma, page, addr,
3774                                                     buf, maddr + offset, bytes);
3775                         }
3776                         kunmap(page);
3777                         put_page(page);
3778                 }
3779                 len -= bytes;
3780                 buf += bytes;
3781                 addr += bytes;
3782         }
3783         up_read(&mm->mmap_sem);
3784 
3785         return buf - old_buf;
3786 }
3787 
3788 /**
3789  * access_remote_vm - access another process' address space
3790  * @mm:         the mm_struct of the target address space
3791  * @addr:       start address to access
3792  * @buf:        source or destination buffer
3793  * @len:        number of bytes to transfer
3794  * @write:      whether the access is a write
3795  *
3796  * The caller must hold a reference on @mm.
3797  */
3798 int access_remote_vm(struct mm_struct *mm, unsigned long addr,
3799                 void *buf, int len, int write)
3800 {
3801         return __access_remote_vm(NULL, mm, addr, buf, len, write);
3802 }
3803 
3804 /*
3805  * Access another process' address space.
3806  * Source/target buffer must be kernel space,
3807  * Do not walk the page table directly, use get_user_pages
3808  */
3809 int access_process_vm(struct task_struct *tsk, unsigned long addr,
3810                 void *buf, int len, int write)
3811 {
3812         struct mm_struct *mm;
3813         int ret;
3814 
3815         mm = get_task_mm(tsk);
3816         if (!mm)
3817                 return 0;
3818 
3819         ret = __access_remote_vm(tsk, mm, addr, buf, len, write);
3820         mmput(mm);
3821 
3822         return ret;
3823 }
3824 
3825 /*
3826  * Print the name of a VMA.
3827  */
3828 void print_vma_addr(char *prefix, unsigned long ip)
3829 {
3830         struct mm_struct *mm = current->mm;
3831         struct vm_area_struct *vma;
3832 
3833         /*
3834          * Do not print if we are in atomic
3835          * contexts (in exception stacks, etc.):
3836          */
3837         if (preempt_count())
3838                 return;
3839 
3840         down_read(&mm->mmap_sem);
3841         vma = find_vma(mm, ip);
3842         if (vma && vma->vm_file) {
3843                 struct file *f = vma->vm_file;
3844                 char *buf = (char *)__get_free_page(GFP_KERNEL);
3845                 if (buf) {
3846                         char *p;
3847 
3848                         p = file_path(f, buf, PAGE_SIZE);
3849                         if (IS_ERR(p))
3850                                 p = "?";
3851                         printk("%s%s[%lx+%lx]", prefix, kbasename(p),
3852                                         vma->vm_start,
3853                                         vma->vm_end - vma->vm_start);
3854                         free_page((unsigned long)buf);
3855                 }
3856         }
3857         up_read(&mm->mmap_sem);
3858 }
3859 
3860 #if defined(CONFIG_PROVE_LOCKING) || defined(CONFIG_DEBUG_ATOMIC_SLEEP)
3861 void __might_fault(const char *file, int line)
3862 {
3863         /*
3864          * Some code (nfs/sunrpc) uses socket ops on kernel memory while
3865          * holding the mmap_sem, this is safe because kernel memory doesn't
3866          * get paged out, therefore we'll never actually fault, and the
3867          * below annotations will generate false positives.
3868          */
3869         if (segment_eq(get_fs(), KERNEL_DS))
3870                 return;
3871         if (pagefault_disabled())
3872                 return;
3873         __might_sleep(file, line, 0);
3874 #if defined(CONFIG_DEBUG_ATOMIC_SLEEP)
3875         if (current->mm)
3876                 might_lock_read(&current->mm->mmap_sem);
3877 #endif
3878 }
3879 EXPORT_SYMBOL(__might_fault);
3880 #endif
3881 
3882 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HUGETLBFS)
3883 static void clear_gigantic_page(struct page *page,
3884                                 unsigned long addr,
3885                                 unsigned int pages_per_huge_page)
3886 {
3887         int i;
3888         struct page *p = page;
3889 
3890         might_sleep();
3891         for (i = 0; i < pages_per_huge_page;
3892              i++, p = mem_map_next(p, page, i)) {
3893                 cond_resched();
3894                 clear_user_highpage(p, addr + i * PAGE_SIZE);
3895         }
3896 }
3897 void clear_huge_page(struct page *page,
3898                      unsigned long addr, unsigned int pages_per_huge_page)
3899 {
3900         int i;
3901 
3902         if (unlikely(pages_per_huge_page > MAX_ORDER_NR_PAGES)) {
3903                 clear_gigantic_page(page, addr, pages_per_huge_page);
3904                 return;
3905         }
3906 
3907         might_sleep();
3908         for (i = 0; i < pages_per_huge_page; i++) {
3909                 cond_resched();
3910                 clear_user_highpage(page + i, addr + i * PAGE_SIZE);
3911         }
3912 }
3913 
3914 static void copy_user_gigantic_page(struct page *dst, struct page *src,
3915                                     unsigned long addr,
3916                                     struct vm_area_struct *vma,
3917                                     unsigned int pages_per_huge_page)
3918 {
3919         int i;
3920         struct page *dst_base = dst;
3921         struct page *src_base = src;
3922 
3923         for (i = 0; i < pages_per_huge_page; ) {
3924                 cond_resched();
3925                 copy_user_highpage(dst, src, addr + i*PAGE_SIZE, vma);
3926 
3927                 i++;
3928                 dst = mem_map_next(dst, dst_base, i);
3929                 src = mem_map_next(src, src_base, i);
3930         }
3931 }
3932 
3933 void copy_user_huge_page(struct page *dst, struct page *src,
3934                          unsigned long addr, struct vm_area_struct *vma,
3935                          unsigned int pages_per_huge_page)
3936 {
3937         int i;
3938 
3939         if (unlikely(pages_per_huge_page > MAX_ORDER_NR_PAGES)) {
3940                 copy_user_gigantic_page(dst, src, addr, vma,
3941                                         pages_per_huge_page);
3942                 return;
3943         }
3944 
3945         might_sleep();
3946         for (i = 0; i < pages_per_huge_page; i++) {
3947                 cond_resched();
3948                 copy_user_highpage(dst + i, src + i, addr + i*PAGE_SIZE, vma);
3949         }
3950 }
3951 #endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */
3952 
3953 #if USE_SPLIT_PTE_PTLOCKS && ALLOC_SPLIT_PTLOCKS
3954 
3955 static struct kmem_cache *page_ptl_cachep;
3956 
3957 void __init ptlock_cache_init(void)
3958 {
3959         page_ptl_cachep = kmem_cache_create("page->ptl", sizeof(spinlock_t), 0,
3960                         SLAB_PANIC, NULL);
3961 }
3962 
3963 bool ptlock_alloc(struct page *page)
3964 {
3965         spinlock_t *ptl;
3966 
3967         ptl = kmem_cache_alloc(page_ptl_cachep, GFP_KERNEL);
3968         if (!ptl)
3969                 return false;
3970         page->ptl = ptl;
3971         return true;
3972 }
3973 
3974 void ptlock_free(struct page *page)
3975 {
3976         kmem_cache_free(page_ptl_cachep, page->ptl);
3977 }
3978 #endif
3979 

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