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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 #include <linux/dax.h>
 67 
 68 #include <asm/io.h>
 69 #include <asm/mmu_context.h>
 70 #include <asm/pgalloc.h>
 71 #include <linux/uaccess.h>
 72 #include <asm/tlb.h>
 73 #include <asm/tlbflush.h>
 74 #include <asm/pgtable.h>
 75 
 76 #include "internal.h"
 77 
 78 #ifdef LAST_CPUPID_NOT_IN_PAGE_FLAGS
 79 #warning Unfortunate NUMA and NUMA Balancing config, growing page-frame for last_cpupid.
 80 #endif
 81 
 82 #ifndef CONFIG_NEED_MULTIPLE_NODES
 83 /* use the per-pgdat data instead for discontigmem - mbligh */
 84 unsigned long max_mapnr;
 85 struct page *mem_map;
 86 
 87 EXPORT_SYMBOL(max_mapnr);
 88 EXPORT_SYMBOL(mem_map);
 89 #endif
 90 
 91 /*
 92  * A number of key systems in x86 including ioremap() rely on the assumption
 93  * that high_memory defines the upper bound on direct map memory, then end
 94  * of ZONE_NORMAL.  Under CONFIG_DISCONTIG this means that max_low_pfn and
 95  * highstart_pfn must be the same; there must be no gap between ZONE_NORMAL
 96  * and ZONE_HIGHMEM.
 97  */
 98 void * high_memory;
 99 
100 EXPORT_SYMBOL(high_memory);
101 
102 /*
103  * Randomize the address space (stacks, mmaps, brk, etc.).
104  *
105  * ( When CONFIG_COMPAT_BRK=y we exclude brk from randomization,
106  *   as ancient (libc5 based) binaries can segfault. )
107  */
108 int randomize_va_space __read_mostly =
109 #ifdef CONFIG_COMPAT_BRK
110                                         1;
111 #else
112                                         2;
113 #endif
114 
115 static int __init disable_randmaps(char *s)
116 {
117         randomize_va_space = 0;
118         return 1;
119 }
120 __setup("norandmaps", disable_randmaps);
121 
122 unsigned long zero_pfn __read_mostly;
123 unsigned long highest_memmap_pfn __read_mostly;
124 
125 EXPORT_SYMBOL(zero_pfn);
126 
127 /*
128  * CONFIG_MMU architectures set up ZERO_PAGE in their paging_init()
129  */
130 static int __init init_zero_pfn(void)
131 {
132         zero_pfn = page_to_pfn(ZERO_PAGE(0));
133         return 0;
134 }
135 core_initcall(init_zero_pfn);
136 
137 
138 #if defined(SPLIT_RSS_COUNTING)
139 
140 void sync_mm_rss(struct mm_struct *mm)
141 {
142         int i;
143 
144         for (i = 0; i < NR_MM_COUNTERS; i++) {
145                 if (current->rss_stat.count[i]) {
146                         add_mm_counter(mm, i, current->rss_stat.count[i]);
147                         current->rss_stat.count[i] = 0;
148                 }
149         }
150         current->rss_stat.events = 0;
151 }
152 
153 static void add_mm_counter_fast(struct mm_struct *mm, int member, int val)
154 {
155         struct task_struct *task = current;
156 
157         if (likely(task->mm == mm))
158                 task->rss_stat.count[member] += val;
159         else
160                 add_mm_counter(mm, member, val);
161 }
162 #define inc_mm_counter_fast(mm, member) add_mm_counter_fast(mm, member, 1)
163 #define dec_mm_counter_fast(mm, member) add_mm_counter_fast(mm, member, -1)
164 
165 /* sync counter once per 64 page faults */
166 #define TASK_RSS_EVENTS_THRESH  (64)
167 static void check_sync_rss_stat(struct task_struct *task)
168 {
169         if (unlikely(task != current))
170                 return;
171         if (unlikely(task->rss_stat.events++ > TASK_RSS_EVENTS_THRESH))
172                 sync_mm_rss(task->mm);
173 }
174 #else /* SPLIT_RSS_COUNTING */
175 
176 #define inc_mm_counter_fast(mm, member) inc_mm_counter(mm, member)
177 #define dec_mm_counter_fast(mm, member) dec_mm_counter(mm, member)
178 
179 static void check_sync_rss_stat(struct task_struct *task)
180 {
181 }
182 
183 #endif /* SPLIT_RSS_COUNTING */
184 
185 #ifdef HAVE_GENERIC_MMU_GATHER
186 
187 static bool tlb_next_batch(struct mmu_gather *tlb)
188 {
189         struct mmu_gather_batch *batch;
190 
191         batch = tlb->active;
192         if (batch->next) {
193                 tlb->active = batch->next;
194                 return true;
195         }
196 
197         if (tlb->batch_count == MAX_GATHER_BATCH_COUNT)
198                 return false;
199 
200         batch = (void *)__get_free_pages(GFP_NOWAIT | __GFP_NOWARN, 0);
201         if (!batch)
202                 return false;
203 
204         tlb->batch_count++;
205         batch->next = NULL;
206         batch->nr   = 0;
207         batch->max  = MAX_GATHER_BATCH;
208 
209         tlb->active->next = batch;
210         tlb->active = batch;
211 
212         return true;
213 }
214 
215 /* tlb_gather_mmu
216  *      Called to initialize an (on-stack) mmu_gather structure for page-table
217  *      tear-down from @mm. The @fullmm argument is used when @mm is without
218  *      users and we're going to destroy the full address space (exit/execve).
219  */
220 void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, unsigned long start, unsigned long end)
221 {
222         tlb->mm = mm;
223 
224         /* Is it from 0 to ~0? */
225         tlb->fullmm     = !(start | (end+1));
226         tlb->need_flush_all = 0;
227         tlb->local.next = NULL;
228         tlb->local.nr   = 0;
229         tlb->local.max  = ARRAY_SIZE(tlb->__pages);
230         tlb->active     = &tlb->local;
231         tlb->batch_count = 0;
232 
233 #ifdef CONFIG_HAVE_RCU_TABLE_FREE
234         tlb->batch = NULL;
235 #endif
236         tlb->page_size = 0;
237 
238         __tlb_reset_range(tlb);
239 }
240 
241 static void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb)
242 {
243         if (!tlb->end)
244                 return;
245 
246         tlb_flush(tlb);
247         mmu_notifier_invalidate_range(tlb->mm, tlb->start, tlb->end);
248 #ifdef CONFIG_HAVE_RCU_TABLE_FREE
249         tlb_table_flush(tlb);
250 #endif
251         __tlb_reset_range(tlb);
252 }
253 
254 static void tlb_flush_mmu_free(struct mmu_gather *tlb)
255 {
256         struct mmu_gather_batch *batch;
257 
258         for (batch = &tlb->local; batch && batch->nr; batch = batch->next) {
259                 free_pages_and_swap_cache(batch->pages, batch->nr);
260                 batch->nr = 0;
261         }
262         tlb->active = &tlb->local;
263 }
264 
265 void tlb_flush_mmu(struct mmu_gather *tlb)
266 {
267         tlb_flush_mmu_tlbonly(tlb);
268         tlb_flush_mmu_free(tlb);
269 }
270 
271 /* tlb_finish_mmu
272  *      Called at the end of the shootdown operation to free up any resources
273  *      that were required.
274  */
275 void tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
276 {
277         struct mmu_gather_batch *batch, *next;
278 
279         tlb_flush_mmu(tlb);
280 
281         /* keep the page table cache within bounds */
282         check_pgt_cache();
283 
284         for (batch = tlb->local.next; batch; batch = next) {
285                 next = batch->next;
286                 free_pages((unsigned long)batch, 0);
287         }
288         tlb->local.next = NULL;
289 }
290 
291 /* __tlb_remove_page
292  *      Must perform the equivalent to __free_pte(pte_get_and_clear(ptep)), while
293  *      handling the additional races in SMP caused by other CPUs caching valid
294  *      mappings in their TLBs. Returns the number of free page slots left.
295  *      When out of page slots we must call tlb_flush_mmu().
296  *returns true if the caller should flush.
297  */
298 bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page, int page_size)
299 {
300         struct mmu_gather_batch *batch;
301 
302         VM_BUG_ON(!tlb->end);
303         VM_WARN_ON(tlb->page_size != page_size);
304 
305         batch = tlb->active;
306         /*
307          * Add the page and check if we are full. If so
308          * force a flush.
309          */
310         batch->pages[batch->nr++] = page;
311         if (batch->nr == batch->max) {
312                 if (!tlb_next_batch(tlb))
313                         return true;
314                 batch = tlb->active;
315         }
316         VM_BUG_ON_PAGE(batch->nr > batch->max, page);
317 
318         return false;
319 }
320 
321 #endif /* HAVE_GENERIC_MMU_GATHER */
322 
323 #ifdef CONFIG_HAVE_RCU_TABLE_FREE
324 
325 /*
326  * See the comment near struct mmu_table_batch.
327  */
328 
329 static void tlb_remove_table_smp_sync(void *arg)
330 {
331         /* Simply deliver the interrupt */
332 }
333 
334 static void tlb_remove_table_one(void *table)
335 {
336         /*
337          * This isn't an RCU grace period and hence the page-tables cannot be
338          * assumed to be actually RCU-freed.
339          *
340          * It is however sufficient for software page-table walkers that rely on
341          * IRQ disabling. See the comment near struct mmu_table_batch.
342          */
343         smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
344         __tlb_remove_table(table);
345 }
346 
347 static void tlb_remove_table_rcu(struct rcu_head *head)
348 {
349         struct mmu_table_batch *batch;
350         int i;
351 
352         batch = container_of(head, struct mmu_table_batch, rcu);
353 
354         for (i = 0; i < batch->nr; i++)
355                 __tlb_remove_table(batch->tables[i]);
356 
357         free_page((unsigned long)batch);
358 }
359 
360 void tlb_table_flush(struct mmu_gather *tlb)
361 {
362         struct mmu_table_batch **batch = &tlb->batch;
363 
364         if (*batch) {
365                 call_rcu_sched(&(*batch)->rcu, tlb_remove_table_rcu);
366                 *batch = NULL;
367         }
368 }
369 
370 void tlb_remove_table(struct mmu_gather *tlb, void *table)
371 {
372         struct mmu_table_batch **batch = &tlb->batch;
373 
374         /*
375          * When there's less then two users of this mm there cannot be a
376          * concurrent page-table walk.
377          */
378         if (atomic_read(&tlb->mm->mm_users) < 2) {
379                 __tlb_remove_table(table);
380                 return;
381         }
382 
383         if (*batch == NULL) {
384                 *batch = (struct mmu_table_batch *)__get_free_page(GFP_NOWAIT | __GFP_NOWARN);
385                 if (*batch == NULL) {
386                         tlb_remove_table_one(table);
387                         return;
388                 }
389                 (*batch)->nr = 0;
390         }
391         (*batch)->tables[(*batch)->nr++] = table;
392         if ((*batch)->nr == MAX_TABLE_BATCH)
393                 tlb_table_flush(tlb);
394 }
395 
396 #endif /* CONFIG_HAVE_RCU_TABLE_FREE */
397 
398 /*
399  * Note: this doesn't free the actual pages themselves. That
400  * has been handled earlier when unmapping all the memory regions.
401  */
402 static void free_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
403                            unsigned long addr)
404 {
405         pgtable_t token = pmd_pgtable(*pmd);
406         pmd_clear(pmd);
407         pte_free_tlb(tlb, token, addr);
408         atomic_long_dec(&tlb->mm->nr_ptes);
409 }
410 
411 static inline void free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
412                                 unsigned long addr, unsigned long end,
413                                 unsigned long floor, unsigned long ceiling)
414 {
415         pmd_t *pmd;
416         unsigned long next;
417         unsigned long start;
418 
419         start = addr;
420         pmd = pmd_offset(pud, addr);
421         do {
422                 next = pmd_addr_end(addr, end);
423                 if (pmd_none_or_clear_bad(pmd))
424                         continue;
425                 free_pte_range(tlb, pmd, addr);
426         } while (pmd++, addr = next, addr != end);
427 
428         start &= PUD_MASK;
429         if (start < floor)
430                 return;
431         if (ceiling) {
432                 ceiling &= PUD_MASK;
433                 if (!ceiling)
434                         return;
435         }
436         if (end - 1 > ceiling - 1)
437                 return;
438 
439         pmd = pmd_offset(pud, start);
440         pud_clear(pud);
441         pmd_free_tlb(tlb, pmd, start);
442         mm_dec_nr_pmds(tlb->mm);
443 }
444 
445 static inline void free_pud_range(struct mmu_gather *tlb, pgd_t *pgd,
446                                 unsigned long addr, unsigned long end,
447                                 unsigned long floor, unsigned long ceiling)
448 {
449         pud_t *pud;
450         unsigned long next;
451         unsigned long start;
452 
453         start = addr;
454         pud = pud_offset(pgd, addr);
455         do {
456                 next = pud_addr_end(addr, end);
457                 if (pud_none_or_clear_bad(pud))
458                         continue;
459                 free_pmd_range(tlb, pud, addr, next, floor, ceiling);
460         } while (pud++, addr = next, addr != end);
461 
462         start &= PGDIR_MASK;
463         if (start < floor)
464                 return;
465         if (ceiling) {
466                 ceiling &= PGDIR_MASK;
467                 if (!ceiling)
468                         return;
469         }
470         if (end - 1 > ceiling - 1)
471                 return;
472 
473         pud = pud_offset(pgd, start);
474         pgd_clear(pgd);
475         pud_free_tlb(tlb, pud, start);
476 }
477 
478 /*
479  * This function frees user-level page tables of a process.
480  */
481 void free_pgd_range(struct mmu_gather *tlb,
482                         unsigned long addr, unsigned long end,
483                         unsigned long floor, unsigned long ceiling)
484 {
485         pgd_t *pgd;
486         unsigned long next;
487 
488         /*
489          * The next few lines have given us lots of grief...
490          *
491          * Why are we testing PMD* at this top level?  Because often
492          * there will be no work to do at all, and we'd prefer not to
493          * go all the way down to the bottom just to discover that.
494          *
495          * Why all these "- 1"s?  Because 0 represents both the bottom
496          * of the address space and the top of it (using -1 for the
497          * top wouldn't help much: the masks would do the wrong thing).
498          * The rule is that addr 0 and floor 0 refer to the bottom of
499          * the address space, but end 0 and ceiling 0 refer to the top
500          * Comparisons need to use "end - 1" and "ceiling - 1" (though
501          * that end 0 case should be mythical).
502          *
503          * Wherever addr is brought up or ceiling brought down, we must
504          * be careful to reject "the opposite 0" before it confuses the
505          * subsequent tests.  But what about where end is brought down
506          * by PMD_SIZE below? no, end can't go down to 0 there.
507          *
508          * Whereas we round start (addr) and ceiling down, by different
509          * masks at different levels, in order to test whether a table
510          * now has no other vmas using it, so can be freed, we don't
511          * bother to round floor or end up - the tests don't need that.
512          */
513 
514         addr &= PMD_MASK;
515         if (addr < floor) {
516                 addr += PMD_SIZE;
517                 if (!addr)
518                         return;
519         }
520         if (ceiling) {
521                 ceiling &= PMD_MASK;
522                 if (!ceiling)
523                         return;
524         }
525         if (end - 1 > ceiling - 1)
526                 end -= PMD_SIZE;
527         if (addr > end - 1)
528                 return;
529         /*
530          * We add page table cache pages with PAGE_SIZE,
531          * (see pte_free_tlb()), flush the tlb if we need
532          */
533         tlb_remove_check_page_size_change(tlb, PAGE_SIZE);
534         pgd = pgd_offset(tlb->mm, addr);
535         do {
536                 next = pgd_addr_end(addr, end);
537                 if (pgd_none_or_clear_bad(pgd))
538                         continue;
539                 free_pud_range(tlb, pgd, addr, next, floor, ceiling);
540         } while (pgd++, addr = next, addr != end);
541 }
542 
543 void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *vma,
544                 unsigned long floor, unsigned long ceiling)
545 {
546         while (vma) {
547                 struct vm_area_struct *next = vma->vm_next;
548                 unsigned long addr = vma->vm_start;
549 
550                 /*
551                  * Hide vma from rmap and truncate_pagecache before freeing
552                  * pgtables
553                  */
554                 unlink_anon_vmas(vma);
555                 unlink_file_vma(vma);
556 
557                 if (is_vm_hugetlb_page(vma)) {
558                         hugetlb_free_pgd_range(tlb, addr, vma->vm_end,
559                                 floor, next? next->vm_start: ceiling);
560                 } else {
561                         /*
562                          * Optimization: gather nearby vmas into one call down
563                          */
564                         while (next && next->vm_start <= vma->vm_end + PMD_SIZE
565                                && !is_vm_hugetlb_page(next)) {
566                                 vma = next;
567                                 next = vma->vm_next;
568                                 unlink_anon_vmas(vma);
569                                 unlink_file_vma(vma);
570                         }
571                         free_pgd_range(tlb, addr, vma->vm_end,
572                                 floor, next? next->vm_start: ceiling);
573                 }
574                 vma = next;
575         }
576 }
577 
578 int __pte_alloc(struct mm_struct *mm, pmd_t *pmd, unsigned long address)
579 {
580         spinlock_t *ptl;
581         pgtable_t new = pte_alloc_one(mm, address);
582         if (!new)
583                 return -ENOMEM;
584 
585         /*
586          * Ensure all pte setup (eg. pte page lock and page clearing) are
587          * visible before the pte is made visible to other CPUs by being
588          * put into page tables.
589          *
590          * The other side of the story is the pointer chasing in the page
591          * table walking code (when walking the page table without locking;
592          * ie. most of the time). Fortunately, these data accesses consist
593          * of a chain of data-dependent loads, meaning most CPUs (alpha
594          * being the notable exception) will already guarantee loads are
595          * seen in-order. See the alpha page table accessors for the
596          * smp_read_barrier_depends() barriers in page table walking code.
597          */
598         smp_wmb(); /* Could be smp_wmb__xxx(before|after)_spin_lock */
599 
600         ptl = pmd_lock(mm, pmd);
601         if (likely(pmd_none(*pmd))) {   /* Has another populated it ? */
602                 atomic_long_inc(&mm->nr_ptes);
603                 pmd_populate(mm, pmd, new);
604                 new = NULL;
605         }
606         spin_unlock(ptl);
607         if (new)
608                 pte_free(mm, new);
609         return 0;
610 }
611 
612 int __pte_alloc_kernel(pmd_t *pmd, unsigned long address)
613 {
614         pte_t *new = pte_alloc_one_kernel(&init_mm, address);
615         if (!new)
616                 return -ENOMEM;
617 
618         smp_wmb(); /* See comment in __pte_alloc */
619 
620         spin_lock(&init_mm.page_table_lock);
621         if (likely(pmd_none(*pmd))) {   /* Has another populated it ? */
622                 pmd_populate_kernel(&init_mm, pmd, new);
623                 new = NULL;
624         }
625         spin_unlock(&init_mm.page_table_lock);
626         if (new)
627                 pte_free_kernel(&init_mm, new);
628         return 0;
629 }
630 
631 static inline void init_rss_vec(int *rss)
632 {
633         memset(rss, 0, sizeof(int) * NR_MM_COUNTERS);
634 }
635 
636 static inline void add_mm_rss_vec(struct mm_struct *mm, int *rss)
637 {
638         int i;
639 
640         if (current->mm == mm)
641                 sync_mm_rss(mm);
642         for (i = 0; i < NR_MM_COUNTERS; i++)
643                 if (rss[i])
644                         add_mm_counter(mm, i, rss[i]);
645 }
646 
647 /*
648  * This function is called to print an error when a bad pte
649  * is found. For example, we might have a PFN-mapped pte in
650  * a region that doesn't allow it.
651  *
652  * The calling function must still handle the error.
653  */
654 static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
655                           pte_t pte, struct page *page)
656 {
657         pgd_t *pgd = pgd_offset(vma->vm_mm, addr);
658         pud_t *pud = pud_offset(pgd, addr);
659         pmd_t *pmd = pmd_offset(pud, addr);
660         struct address_space *mapping;
661         pgoff_t index;
662         static unsigned long resume;
663         static unsigned long nr_shown;
664         static unsigned long nr_unshown;
665 
666         /*
667          * Allow a burst of 60 reports, then keep quiet for that minute;
668          * or allow a steady drip of one report per second.
669          */
670         if (nr_shown == 60) {
671                 if (time_before(jiffies, resume)) {
672                         nr_unshown++;
673                         return;
674                 }
675                 if (nr_unshown) {
676                         pr_alert("BUG: Bad page map: %lu messages suppressed\n",
677                                  nr_unshown);
678                         nr_unshown = 0;
679                 }
680                 nr_shown = 0;
681         }
682         if (nr_shown++ == 0)
683                 resume = jiffies + 60 * HZ;
684 
685         mapping = vma->vm_file ? vma->vm_file->f_mapping : NULL;
686         index = linear_page_index(vma, addr);
687 
688         pr_alert("BUG: Bad page map in process %s  pte:%08llx pmd:%08llx\n",
689                  current->comm,
690                  (long long)pte_val(pte), (long long)pmd_val(*pmd));
691         if (page)
692                 dump_page(page, "bad pte");
693         pr_alert("addr:%p vm_flags:%08lx anon_vma:%p mapping:%p index:%lx\n",
694                  (void *)addr, vma->vm_flags, vma->anon_vma, mapping, index);
695         /*
696          * Choose text because data symbols depend on CONFIG_KALLSYMS_ALL=y
697          */
698         pr_alert("file:%pD fault:%pf mmap:%pf readpage:%pf\n",
699                  vma->vm_file,
700                  vma->vm_ops ? vma->vm_ops->fault : NULL,
701                  vma->vm_file ? vma->vm_file->f_op->mmap : NULL,
702                  mapping ? mapping->a_ops->readpage : NULL);
703         dump_stack();
704         add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
705 }
706 
707 /*
708  * vm_normal_page -- This function gets the "struct page" associated with a pte.
709  *
710  * "Special" mappings do not wish to be associated with a "struct page" (either
711  * it doesn't exist, or it exists but they don't want to touch it). In this
712  * case, NULL is returned here. "Normal" mappings do have a struct page.
713  *
714  * There are 2 broad cases. Firstly, an architecture may define a pte_special()
715  * pte bit, in which case this function is trivial. Secondly, an architecture
716  * may not have a spare pte bit, which requires a more complicated scheme,
717  * described below.
718  *
719  * A raw VM_PFNMAP mapping (ie. one that is not COWed) is always considered a
720  * special mapping (even if there are underlying and valid "struct pages").
721  * COWed pages of a VM_PFNMAP are always normal.
722  *
723  * The way we recognize COWed pages within VM_PFNMAP mappings is through the
724  * rules set up by "remap_pfn_range()": the vma will have the VM_PFNMAP bit
725  * set, and the vm_pgoff will point to the first PFN mapped: thus every special
726  * mapping will always honor the rule
727  *
728  *      pfn_of_page == vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT)
729  *
730  * And for normal mappings this is false.
731  *
732  * This restricts such mappings to be a linear translation from virtual address
733  * to pfn. To get around this restriction, we allow arbitrary mappings so long
734  * as the vma is not a COW mapping; in that case, we know that all ptes are
735  * special (because none can have been COWed).
736  *
737  *
738  * In order to support COW of arbitrary special mappings, we have VM_MIXEDMAP.
739  *
740  * VM_MIXEDMAP mappings can likewise contain memory with or without "struct
741  * page" backing, however the difference is that _all_ pages with a struct
742  * page (that is, those where pfn_valid is true) are refcounted and considered
743  * normal pages by the VM. The disadvantage is that pages are refcounted
744  * (which can be slower and simply not an option for some PFNMAP users). The
745  * advantage is that we don't have to follow the strict linearity rule of
746  * PFNMAP mappings in order to support COWable mappings.
747  *
748  */
749 #ifdef __HAVE_ARCH_PTE_SPECIAL
750 # define HAVE_PTE_SPECIAL 1
751 #else
752 # define HAVE_PTE_SPECIAL 0
753 #endif
754 struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
755                                 pte_t pte)
756 {
757         unsigned long pfn = pte_pfn(pte);
758 
759         if (HAVE_PTE_SPECIAL) {
760                 if (likely(!pte_special(pte)))
761                         goto check_pfn;
762                 if (vma->vm_ops && vma->vm_ops->find_special_page)
763                         return vma->vm_ops->find_special_page(vma, addr);
764                 if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
765                         return NULL;
766                 if (!is_zero_pfn(pfn))
767                         print_bad_pte(vma, addr, pte, NULL);
768                 return NULL;
769         }
770 
771         /* !HAVE_PTE_SPECIAL case follows: */
772 
773         if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
774                 if (vma->vm_flags & VM_MIXEDMAP) {
775                         if (!pfn_valid(pfn))
776                                 return NULL;
777                         goto out;
778                 } else {
779                         unsigned long off;
780                         off = (addr - vma->vm_start) >> PAGE_SHIFT;
781                         if (pfn == vma->vm_pgoff + off)
782                                 return NULL;
783                         if (!is_cow_mapping(vma->vm_flags))
784                                 return NULL;
785                 }
786         }
787 
788         if (is_zero_pfn(pfn))
789                 return NULL;
790 check_pfn:
791         if (unlikely(pfn > highest_memmap_pfn)) {
792                 print_bad_pte(vma, addr, pte, NULL);
793                 return NULL;
794         }
795 
796         /*
797          * NOTE! We still have PageReserved() pages in the page tables.
798          * eg. VDSO mappings can cause them to exist.
799          */
800 out:
801         return pfn_to_page(pfn);
802 }
803 
804 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
805 struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,
806                                 pmd_t pmd)
807 {
808         unsigned long pfn = pmd_pfn(pmd);
809 
810         /*
811          * There is no pmd_special() but there may be special pmds, e.g.
812          * in a direct-access (dax) mapping, so let's just replicate the
813          * !HAVE_PTE_SPECIAL case from vm_normal_page() here.
814          */
815         if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
816                 if (vma->vm_flags & VM_MIXEDMAP) {
817                         if (!pfn_valid(pfn))
818                                 return NULL;
819                         goto out;
820                 } else {
821                         unsigned long off;
822                         off = (addr - vma->vm_start) >> PAGE_SHIFT;
823                         if (pfn == vma->vm_pgoff + off)
824                                 return NULL;
825                         if (!is_cow_mapping(vma->vm_flags))
826                                 return NULL;
827                 }
828         }
829 
830         if (is_zero_pfn(pfn))
831                 return NULL;
832         if (unlikely(pfn > highest_memmap_pfn))
833                 return NULL;
834 
835         /*
836          * NOTE! We still have PageReserved() pages in the page tables.
837          * eg. VDSO mappings can cause them to exist.
838          */
839 out:
840         return pfn_to_page(pfn);
841 }
842 #endif
843 
844 /*
845  * copy one vm_area from one task to the other. Assumes the page tables
846  * already present in the new task to be cleared in the whole range
847  * covered by this vma.
848  */
849 
850 static inline unsigned long
851 copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
852                 pte_t *dst_pte, pte_t *src_pte, struct vm_area_struct *vma,
853                 unsigned long addr, int *rss)
854 {
855         unsigned long vm_flags = vma->vm_flags;
856         pte_t pte = *src_pte;
857         struct page *page;
858 
859         /* pte contains position in swap or file, so copy. */
860         if (unlikely(!pte_present(pte))) {
861                 swp_entry_t entry = pte_to_swp_entry(pte);
862 
863                 if (likely(!non_swap_entry(entry))) {
864                         if (swap_duplicate(entry) < 0)
865                                 return entry.val;
866 
867                         /* make sure dst_mm is on swapoff's mmlist. */
868                         if (unlikely(list_empty(&dst_mm->mmlist))) {
869                                 spin_lock(&mmlist_lock);
870                                 if (list_empty(&dst_mm->mmlist))
871                                         list_add(&dst_mm->mmlist,
872                                                         &src_mm->mmlist);
873                                 spin_unlock(&mmlist_lock);
874                         }
875                         rss[MM_SWAPENTS]++;
876                 } else if (is_migration_entry(entry)) {
877                         page = migration_entry_to_page(entry);
878 
879                         rss[mm_counter(page)]++;
880 
881                         if (is_write_migration_entry(entry) &&
882                                         is_cow_mapping(vm_flags)) {
883                                 /*
884                                  * COW mappings require pages in both
885                                  * parent and child to be set to read.
886                                  */
887                                 make_migration_entry_read(&entry);
888                                 pte = swp_entry_to_pte(entry);
889                                 if (pte_swp_soft_dirty(*src_pte))
890                                         pte = pte_swp_mksoft_dirty(pte);
891                                 set_pte_at(src_mm, addr, src_pte, pte);
892                         }
893                 }
894                 goto out_set_pte;
895         }
896 
897         /*
898          * If it's a COW mapping, write protect it both
899          * in the parent and the child
900          */
901         if (is_cow_mapping(vm_flags)) {
902                 ptep_set_wrprotect(src_mm, addr, src_pte);
903                 pte = pte_wrprotect(pte);
904         }
905 
906         /*
907          * If it's a shared mapping, mark it clean in
908          * the child
909          */
910         if (vm_flags & VM_SHARED)
911                 pte = pte_mkclean(pte);
912         pte = pte_mkold(pte);
913 
914         page = vm_normal_page(vma, addr, pte);
915         if (page) {
916                 get_page(page);
917                 page_dup_rmap(page, false);
918                 rss[mm_counter(page)]++;
919         }
920 
921 out_set_pte:
922         set_pte_at(dst_mm, addr, dst_pte, pte);
923         return 0;
924 }
925 
926 static int copy_pte_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
927                    pmd_t *dst_pmd, pmd_t *src_pmd, struct vm_area_struct *vma,
928                    unsigned long addr, unsigned long end)
929 {
930         pte_t *orig_src_pte, *orig_dst_pte;
931         pte_t *src_pte, *dst_pte;
932         spinlock_t *src_ptl, *dst_ptl;
933         int progress = 0;
934         int rss[NR_MM_COUNTERS];
935         swp_entry_t entry = (swp_entry_t){0};
936 
937 again:
938         init_rss_vec(rss);
939 
940         dst_pte = pte_alloc_map_lock(dst_mm, dst_pmd, addr, &dst_ptl);
941         if (!dst_pte)
942                 return -ENOMEM;
943         src_pte = pte_offset_map(src_pmd, addr);
944         src_ptl = pte_lockptr(src_mm, src_pmd);
945         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
946         orig_src_pte = src_pte;
947         orig_dst_pte = dst_pte;
948         arch_enter_lazy_mmu_mode();
949 
950         do {
951                 /*
952                  * We are holding two locks at this point - either of them
953                  * could generate latencies in another task on another CPU.
954                  */
955                 if (progress >= 32) {
956                         progress = 0;
957                         if (need_resched() ||
958                             spin_needbreak(src_ptl) || spin_needbreak(dst_ptl))
959                                 break;
960                 }
961                 if (pte_none(*src_pte)) {
962                         progress++;
963                         continue;
964                 }
965                 entry.val = copy_one_pte(dst_mm, src_mm, dst_pte, src_pte,
966                                                         vma, addr, rss);
967                 if (entry.val)
968                         break;
969                 progress += 8;
970         } while (dst_pte++, src_pte++, addr += PAGE_SIZE, addr != end);
971 
972         arch_leave_lazy_mmu_mode();
973         spin_unlock(src_ptl);
974         pte_unmap(orig_src_pte);
975         add_mm_rss_vec(dst_mm, rss);
976         pte_unmap_unlock(orig_dst_pte, dst_ptl);
977         cond_resched();
978 
979         if (entry.val) {
980                 if (add_swap_count_continuation(entry, GFP_KERNEL) < 0)
981                         return -ENOMEM;
982                 progress = 0;
983         }
984         if (addr != end)
985                 goto again;
986         return 0;
987 }
988 
989 static inline int copy_pmd_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
990                 pud_t *dst_pud, pud_t *src_pud, struct vm_area_struct *vma,
991                 unsigned long addr, unsigned long end)
992 {
993         pmd_t *src_pmd, *dst_pmd;
994         unsigned long next;
995 
996         dst_pmd = pmd_alloc(dst_mm, dst_pud, addr);
997         if (!dst_pmd)
998                 return -ENOMEM;
999         src_pmd = pmd_offset(src_pud, addr);
1000         do {
1001                 next = pmd_addr_end(addr, end);
1002                 if (pmd_trans_huge(*src_pmd) || pmd_devmap(*src_pmd)) {
1003                         int err;
1004                         VM_BUG_ON(next-addr != HPAGE_PMD_SIZE);
1005                         err = copy_huge_pmd(dst_mm, src_mm,
1006                                             dst_pmd, src_pmd, addr, vma);
1007                         if (err == -ENOMEM)
1008                                 return -ENOMEM;
1009                         if (!err)
1010                                 continue;
1011                         /* fall through */
1012                 }
1013                 if (pmd_none_or_clear_bad(src_pmd))
1014                         continue;
1015                 if (copy_pte_range(dst_mm, src_mm, dst_pmd, src_pmd,
1016                                                 vma, addr, next))
1017                         return -ENOMEM;
1018         } while (dst_pmd++, src_pmd++, addr = next, addr != end);
1019         return 0;
1020 }
1021 
1022 static inline int copy_pud_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1023                 pgd_t *dst_pgd, pgd_t *src_pgd, struct vm_area_struct *vma,
1024                 unsigned long addr, unsigned long end)
1025 {
1026         pud_t *src_pud, *dst_pud;
1027         unsigned long next;
1028 
1029         dst_pud = pud_alloc(dst_mm, dst_pgd, addr);
1030         if (!dst_pud)
1031                 return -ENOMEM;
1032         src_pud = pud_offset(src_pgd, addr);
1033         do {
1034                 next = pud_addr_end(addr, end);
1035                 if (pud_none_or_clear_bad(src_pud))
1036                         continue;
1037                 if (copy_pmd_range(dst_mm, src_mm, dst_pud, src_pud,
1038                                                 vma, addr, next))
1039                         return -ENOMEM;
1040         } while (dst_pud++, src_pud++, addr = next, addr != end);
1041         return 0;
1042 }
1043 
1044 int copy_page_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1045                 struct vm_area_struct *vma)
1046 {
1047         pgd_t *src_pgd, *dst_pgd;
1048         unsigned long next;
1049         unsigned long addr = vma->vm_start;
1050         unsigned long end = vma->vm_end;
1051         unsigned long mmun_start;       /* For mmu_notifiers */
1052         unsigned long mmun_end;         /* For mmu_notifiers */
1053         bool is_cow;
1054         int ret;
1055 
1056         /*
1057          * Don't copy ptes where a page fault will fill them correctly.
1058          * Fork becomes much lighter when there are big shared or private
1059          * readonly mappings. The tradeoff is that copy_page_range is more
1060          * efficient than faulting.
1061          */
1062         if (!(vma->vm_flags & (VM_HUGETLB | VM_PFNMAP | VM_MIXEDMAP)) &&
1063                         !vma->anon_vma)
1064                 return 0;
1065 
1066         if (is_vm_hugetlb_page(vma))
1067                 return copy_hugetlb_page_range(dst_mm, src_mm, vma);
1068 
1069         if (unlikely(vma->vm_flags & VM_PFNMAP)) {
1070                 /*
1071                  * We do not free on error cases below as remove_vma
1072                  * gets called on error from higher level routine
1073                  */
1074                 ret = track_pfn_copy(vma);
1075                 if (ret)
1076                         return ret;
1077         }
1078 
1079         /*
1080          * We need to invalidate the secondary MMU mappings only when
1081          * there could be a permission downgrade on the ptes of the
1082          * parent mm. And a permission downgrade will only happen if
1083          * is_cow_mapping() returns true.
1084          */
1085         is_cow = is_cow_mapping(vma->vm_flags);
1086         mmun_start = addr;
1087         mmun_end   = end;
1088         if (is_cow)
1089                 mmu_notifier_invalidate_range_start(src_mm, mmun_start,
1090                                                     mmun_end);
1091 
1092         ret = 0;
1093         dst_pgd = pgd_offset(dst_mm, addr);
1094         src_pgd = pgd_offset(src_mm, addr);
1095         do {
1096                 next = pgd_addr_end(addr, end);
1097                 if (pgd_none_or_clear_bad(src_pgd))
1098                         continue;
1099                 if (unlikely(copy_pud_range(dst_mm, src_mm, dst_pgd, src_pgd,
1100                                             vma, addr, next))) {
1101                         ret = -ENOMEM;
1102                         break;
1103                 }
1104         } while (dst_pgd++, src_pgd++, addr = next, addr != end);
1105 
1106         if (is_cow)
1107                 mmu_notifier_invalidate_range_end(src_mm, mmun_start, mmun_end);
1108         return ret;
1109 }
1110 
1111 static unsigned long zap_pte_range(struct mmu_gather *tlb,
1112                                 struct vm_area_struct *vma, pmd_t *pmd,
1113                                 unsigned long addr, unsigned long end,
1114                                 struct zap_details *details)
1115 {
1116         struct mm_struct *mm = tlb->mm;
1117         int force_flush = 0;
1118         int rss[NR_MM_COUNTERS];
1119         spinlock_t *ptl;
1120         pte_t *start_pte;
1121         pte_t *pte;
1122         swp_entry_t entry;
1123 
1124         tlb_remove_check_page_size_change(tlb, PAGE_SIZE);
1125 again:
1126         init_rss_vec(rss);
1127         start_pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
1128         pte = start_pte;
1129         arch_enter_lazy_mmu_mode();
1130         do {
1131                 pte_t ptent = *pte;
1132                 if (pte_none(ptent)) {
1133                         continue;
1134                 }
1135 
1136                 if (pte_present(ptent)) {
1137                         struct page *page;
1138 
1139                         page = vm_normal_page(vma, addr, ptent);
1140                         if (unlikely(details) && page) {
1141                                 /*
1142                                  * unmap_shared_mapping_pages() wants to
1143                                  * invalidate cache without truncating:
1144                                  * unmap shared but keep private pages.
1145                                  */
1146                                 if (details->check_mapping &&
1147                                     details->check_mapping != page_rmapping(page))
1148                                         continue;
1149                         }
1150                         ptent = ptep_get_and_clear_full(mm, addr, pte,
1151                                                         tlb->fullmm);
1152                         tlb_remove_tlb_entry(tlb, pte, addr);
1153                         if (unlikely(!page))
1154                                 continue;
1155 
1156                         if (!PageAnon(page)) {
1157                                 if (pte_dirty(ptent)) {
1158                                         /*
1159                                          * oom_reaper cannot tear down dirty
1160                                          * pages
1161                                          */
1162                                         if (unlikely(details && details->ignore_dirty))
1163                                                 continue;
1164                                         force_flush = 1;
1165                                         set_page_dirty(page);
1166                                 }
1167                                 if (pte_young(ptent) &&
1168                                     likely(!(vma->vm_flags & VM_SEQ_READ)))
1169                                         mark_page_accessed(page);
1170                         }
1171                         rss[mm_counter(page)]--;
1172                         page_remove_rmap(page, false);
1173                         if (unlikely(page_mapcount(page) < 0))
1174                                 print_bad_pte(vma, addr, ptent, page);
1175                         if (unlikely(__tlb_remove_page(tlb, page))) {
1176                                 force_flush = 1;
1177                                 addr += PAGE_SIZE;
1178                                 break;
1179                         }
1180                         continue;
1181                 }
1182                 /* only check swap_entries if explicitly asked for in details */
1183                 if (unlikely(details && !details->check_swap_entries))
1184                         continue;
1185 
1186                 entry = pte_to_swp_entry(ptent);
1187                 if (!non_swap_entry(entry))
1188                         rss[MM_SWAPENTS]--;
1189                 else if (is_migration_entry(entry)) {
1190                         struct page *page;
1191 
1192                         page = migration_entry_to_page(entry);
1193                         rss[mm_counter(page)]--;
1194                 }
1195                 if (unlikely(!free_swap_and_cache(entry)))
1196                         print_bad_pte(vma, addr, ptent, NULL);
1197                 pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
1198         } while (pte++, addr += PAGE_SIZE, addr != end);
1199 
1200         add_mm_rss_vec(mm, rss);
1201         arch_leave_lazy_mmu_mode();
1202 
1203         /* Do the actual TLB flush before dropping ptl */
1204         if (force_flush)
1205                 tlb_flush_mmu_tlbonly(tlb);
1206         pte_unmap_unlock(start_pte, ptl);
1207 
1208         /*
1209          * If we forced a TLB flush (either due to running out of
1210          * batch buffers or because we needed to flush dirty TLB
1211          * entries before releasing the ptl), free the batched
1212          * memory too. Restart if we didn't do everything.
1213          */
1214         if (force_flush) {
1215                 force_flush = 0;
1216                 tlb_flush_mmu_free(tlb);
1217                 if (addr != end)
1218                         goto again;
1219         }
1220 
1221         return addr;
1222 }
1223 
1224 static inline unsigned long zap_pmd_range(struct mmu_gather *tlb,
1225                                 struct vm_area_struct *vma, pud_t *pud,
1226                                 unsigned long addr, unsigned long end,
1227                                 struct zap_details *details)
1228 {
1229         pmd_t *pmd;
1230         unsigned long next;
1231 
1232         pmd = pmd_offset(pud, addr);
1233         do {
1234                 next = pmd_addr_end(addr, end);
1235                 if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) {
1236                         if (next - addr != HPAGE_PMD_SIZE) {
1237                                 VM_BUG_ON_VMA(vma_is_anonymous(vma) &&
1238                                     !rwsem_is_locked(&tlb->mm->mmap_sem), vma);
1239                                 __split_huge_pmd(vma, pmd, addr, false, NULL);
1240                         } else if (zap_huge_pmd(tlb, vma, pmd, addr))
1241                                 goto next;
1242                         /* fall through */
1243                 }
1244                 /*
1245                  * Here there can be other concurrent MADV_DONTNEED or
1246                  * trans huge page faults running, and if the pmd is
1247                  * none or trans huge it can change under us. This is
1248                  * because MADV_DONTNEED holds the mmap_sem in read
1249                  * mode.
1250                  */
1251                 if (pmd_none_or_trans_huge_or_clear_bad(pmd))
1252                         goto next;
1253                 next = zap_pte_range(tlb, vma, pmd, addr, next, details);
1254 next:
1255                 cond_resched();
1256         } while (pmd++, addr = next, addr != end);
1257 
1258         return addr;
1259 }
1260 
1261 static inline unsigned long zap_pud_range(struct mmu_gather *tlb,
1262                                 struct vm_area_struct *vma, pgd_t *pgd,
1263                                 unsigned long addr, unsigned long end,
1264                                 struct zap_details *details)
1265 {
1266         pud_t *pud;
1267         unsigned long next;
1268 
1269         pud = pud_offset(pgd, addr);
1270         do {
1271                 next = pud_addr_end(addr, end);
1272                 if (pud_none_or_clear_bad(pud))
1273                         continue;
1274                 next = zap_pmd_range(tlb, vma, pud, addr, next, details);
1275         } while (pud++, addr = next, addr != end);
1276 
1277         return addr;
1278 }
1279 
1280 void unmap_page_range(struct mmu_gather *tlb,
1281                              struct vm_area_struct *vma,
1282                              unsigned long addr, unsigned long end,
1283                              struct zap_details *details)
1284 {
1285         pgd_t *pgd;
1286         unsigned long next;
1287 
1288         BUG_ON(addr >= end);
1289         tlb_start_vma(tlb, vma);
1290         pgd = pgd_offset(vma->vm_mm, addr);
1291         do {
1292                 next = pgd_addr_end(addr, end);
1293                 if (pgd_none_or_clear_bad(pgd))
1294                         continue;
1295                 next = zap_pud_range(tlb, vma, pgd, addr, next, details);
1296         } while (pgd++, addr = next, addr != end);
1297         tlb_end_vma(tlb, vma);
1298 }
1299 
1300 
1301 static void unmap_single_vma(struct mmu_gather *tlb,
1302                 struct vm_area_struct *vma, unsigned long start_addr,
1303                 unsigned long end_addr,
1304                 struct zap_details *details)
1305 {
1306         unsigned long start = max(vma->vm_start, start_addr);
1307         unsigned long end;
1308 
1309         if (start >= vma->vm_end)
1310                 return;
1311         end = min(vma->vm_end, end_addr);
1312         if (end <= vma->vm_start)
1313                 return;
1314 
1315         if (vma->vm_file)
1316                 uprobe_munmap(vma, start, end);
1317 
1318         if (unlikely(vma->vm_flags & VM_PFNMAP))
1319                 untrack_pfn(vma, 0, 0);
1320 
1321         if (start != end) {
1322                 if (unlikely(is_vm_hugetlb_page(vma))) {
1323                         /*
1324                          * It is undesirable to test vma->vm_file as it
1325                          * should be non-null for valid hugetlb area.
1326                          * However, vm_file will be NULL in the error
1327                          * cleanup path of mmap_region. When
1328                          * hugetlbfs ->mmap method fails,
1329                          * mmap_region() nullifies vma->vm_file
1330                          * before calling this function to clean up.
1331                          * Since no pte has actually been setup, it is
1332                          * safe to do nothing in this case.
1333                          */
1334                         if (vma->vm_file) {
1335                                 i_mmap_lock_write(vma->vm_file->f_mapping);
1336                                 __unmap_hugepage_range_final(tlb, vma, start, end, NULL);
1337                                 i_mmap_unlock_write(vma->vm_file->f_mapping);
1338                         }
1339                 } else
1340                         unmap_page_range(tlb, vma, start, end, details);
1341         }
1342 }
1343 
1344 /**
1345  * unmap_vmas - unmap a range of memory covered by a list of vma's
1346  * @tlb: address of the caller's struct mmu_gather
1347  * @vma: the starting vma
1348  * @start_addr: virtual address at which to start unmapping
1349  * @end_addr: virtual address at which to end unmapping
1350  *
1351  * Unmap all pages in the vma list.
1352  *
1353  * Only addresses between `start' and `end' will be unmapped.
1354  *
1355  * The VMA list must be sorted in ascending virtual address order.
1356  *
1357  * unmap_vmas() assumes that the caller will flush the whole unmapped address
1358  * range after unmap_vmas() returns.  So the only responsibility here is to
1359  * ensure that any thus-far unmapped pages are flushed before unmap_vmas()
1360  * drops the lock and schedules.
1361  */
1362 void unmap_vmas(struct mmu_gather *tlb,
1363                 struct vm_area_struct *vma, unsigned long start_addr,
1364                 unsigned long end_addr)
1365 {
1366         struct mm_struct *mm = vma->vm_mm;
1367 
1368         mmu_notifier_invalidate_range_start(mm, start_addr, end_addr);
1369         for ( ; vma && vma->vm_start < end_addr; vma = vma->vm_next)
1370                 unmap_single_vma(tlb, vma, start_addr, end_addr, NULL);
1371         mmu_notifier_invalidate_range_end(mm, start_addr, end_addr);
1372 }
1373 
1374 /**
1375  * zap_page_range - remove user pages in a given range
1376  * @vma: vm_area_struct holding the applicable pages
1377  * @start: starting address of pages to zap
1378  * @size: number of bytes to zap
1379  * @details: details of shared cache invalidation
1380  *
1381  * Caller must protect the VMA list
1382  */
1383 void zap_page_range(struct vm_area_struct *vma, unsigned long start,
1384                 unsigned long size, struct zap_details *details)
1385 {
1386         struct mm_struct *mm = vma->vm_mm;
1387         struct mmu_gather tlb;
1388         unsigned long end = start + size;
1389 
1390         lru_add_drain();
1391         tlb_gather_mmu(&tlb, mm, start, end);
1392         update_hiwater_rss(mm);
1393         mmu_notifier_invalidate_range_start(mm, start, end);
1394         for ( ; vma && vma->vm_start < end; vma = vma->vm_next)
1395                 unmap_single_vma(&tlb, vma, start, end, details);
1396         mmu_notifier_invalidate_range_end(mm, start, end);
1397         tlb_finish_mmu(&tlb, start, end);
1398 }
1399 
1400 /**
1401  * zap_page_range_single - remove user pages in a given range
1402  * @vma: vm_area_struct holding the applicable pages
1403  * @address: starting address of pages to zap
1404  * @size: number of bytes to zap
1405  * @details: details of shared cache invalidation
1406  *
1407  * The range must fit into one VMA.
1408  */
1409 static void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
1410                 unsigned long size, struct zap_details *details)
1411 {
1412         struct mm_struct *mm = vma->vm_mm;
1413         struct mmu_gather tlb;
1414         unsigned long end = address + size;
1415 
1416         lru_add_drain();
1417         tlb_gather_mmu(&tlb, mm, address, end);
1418         update_hiwater_rss(mm);
1419         mmu_notifier_invalidate_range_start(mm, address, end);
1420         unmap_single_vma(&tlb, vma, address, end, details);
1421         mmu_notifier_invalidate_range_end(mm, address, end);
1422         tlb_finish_mmu(&tlb, address, end);
1423 }
1424 
1425 /**
1426  * zap_vma_ptes - remove ptes mapping the vma
1427  * @vma: vm_area_struct holding ptes to be zapped
1428  * @address: starting address of pages to zap
1429  * @size: number of bytes to zap
1430  *
1431  * This function only unmaps ptes assigned to VM_PFNMAP vmas.
1432  *
1433  * The entire address range must be fully contained within the vma.
1434  *
1435  * Returns 0 if successful.
1436  */
1437 int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
1438                 unsigned long size)
1439 {
1440         if (address < vma->vm_start || address + size > vma->vm_end ||
1441                         !(vma->vm_flags & VM_PFNMAP))
1442                 return -1;
1443         zap_page_range_single(vma, address, size, NULL);
1444         return 0;
1445 }
1446 EXPORT_SYMBOL_GPL(zap_vma_ptes);
1447 
1448 pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr,
1449                         spinlock_t **ptl)
1450 {
1451         pgd_t * pgd = pgd_offset(mm, addr);
1452         pud_t * pud = pud_alloc(mm, pgd, addr);
1453         if (pud) {
1454                 pmd_t * pmd = pmd_alloc(mm, pud, addr);
1455                 if (pmd) {
1456                         VM_BUG_ON(pmd_trans_huge(*pmd));
1457                         return pte_alloc_map_lock(mm, pmd, addr, ptl);
1458                 }
1459         }
1460         return NULL;
1461 }
1462 
1463 /*
1464  * This is the old fallback for page remapping.
1465  *
1466  * For historical reasons, it only allows reserved pages. Only
1467  * old drivers should use this, and they needed to mark their
1468  * pages reserved for the old functions anyway.
1469  */
1470 static int insert_page(struct vm_area_struct *vma, unsigned long addr,
1471                         struct page *page, pgprot_t prot)
1472 {
1473         struct mm_struct *mm = vma->vm_mm;
1474         int retval;
1475         pte_t *pte;
1476         spinlock_t *ptl;
1477 
1478         retval = -EINVAL;
1479         if (PageAnon(page))
1480                 goto out;
1481         retval = -ENOMEM;
1482         flush_dcache_page(page);
1483         pte = get_locked_pte(mm, addr, &ptl);
1484         if (!pte)
1485                 goto out;
1486         retval = -EBUSY;
1487         if (!pte_none(*pte))
1488                 goto out_unlock;
1489 
1490         /* Ok, finally just insert the thing.. */
1491         get_page(page);
1492         inc_mm_counter_fast(mm, mm_counter_file(page));
1493         page_add_file_rmap(page, false);
1494         set_pte_at(mm, addr, pte, mk_pte(page, prot));
1495 
1496         retval = 0;
1497         pte_unmap_unlock(pte, ptl);
1498         return retval;
1499 out_unlock:
1500         pte_unmap_unlock(pte, ptl);
1501 out:
1502         return retval;
1503 }
1504 
1505 /**
1506  * vm_insert_page - insert single page into user vma
1507  * @vma: user vma to map to
1508  * @addr: target user address of this page
1509  * @page: source kernel page
1510  *
1511  * This allows drivers to insert individual pages they've allocated
1512  * into a user vma.
1513  *
1514  * The page has to be a nice clean _individual_ kernel allocation.
1515  * If you allocate a compound page, you need to have marked it as
1516  * such (__GFP_COMP), or manually just split the page up yourself
1517  * (see split_page()).
1518  *
1519  * NOTE! Traditionally this was done with "remap_pfn_range()" which
1520  * took an arbitrary page protection parameter. This doesn't allow
1521  * that. Your vma protection will have to be set up correctly, which
1522  * means that if you want a shared writable mapping, you'd better
1523  * ask for a shared writable mapping!
1524  *
1525  * The page does not need to be reserved.
1526  *
1527  * Usually this function is called from f_op->mmap() handler
1528  * under mm->mmap_sem write-lock, so it can change vma->vm_flags.
1529  * Caller must set VM_MIXEDMAP on vma if it wants to call this
1530  * function from other places, for example from page-fault handler.
1531  */
1532 int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
1533                         struct page *page)
1534 {
1535         if (addr < vma->vm_start || addr >= vma->vm_end)
1536                 return -EFAULT;
1537         if (!page_count(page))
1538                 return -EINVAL;
1539         if (!(vma->vm_flags & VM_MIXEDMAP)) {
1540                 BUG_ON(down_read_trylock(&vma->vm_mm->mmap_sem));
1541                 BUG_ON(vma->vm_flags & VM_PFNMAP);
1542                 vma->vm_flags |= VM_MIXEDMAP;
1543         }
1544         return insert_page(vma, addr, page, vma->vm_page_prot);
1545 }
1546 EXPORT_SYMBOL(vm_insert_page);
1547 
1548 static int insert_pfn(struct vm_area_struct *vma, unsigned long addr,
1549                         pfn_t pfn, pgprot_t prot)
1550 {
1551         struct mm_struct *mm = vma->vm_mm;
1552         int retval;
1553         pte_t *pte, entry;
1554         spinlock_t *ptl;
1555 
1556         retval = -ENOMEM;
1557         pte = get_locked_pte(mm, addr, &ptl);
1558         if (!pte)
1559                 goto out;
1560         retval = -EBUSY;
1561         if (!pte_none(*pte))
1562                 goto out_unlock;
1563 
1564         /* Ok, finally just insert the thing.. */
1565         if (pfn_t_devmap(pfn))
1566                 entry = pte_mkdevmap(pfn_t_pte(pfn, prot));
1567         else
1568                 entry = pte_mkspecial(pfn_t_pte(pfn, prot));
1569         set_pte_at(mm, addr, pte, entry);
1570         update_mmu_cache(vma, addr, pte); /* XXX: why not for insert_page? */
1571 
1572         retval = 0;
1573 out_unlock:
1574         pte_unmap_unlock(pte, ptl);
1575 out:
1576         return retval;
1577 }
1578 
1579 /**
1580  * vm_insert_pfn - insert single pfn into user vma
1581  * @vma: user vma to map to
1582  * @addr: target user address of this page
1583  * @pfn: source kernel pfn
1584  *
1585  * Similar to vm_insert_page, this allows drivers to insert individual pages
1586  * they've allocated into a user vma. Same comments apply.
1587  *
1588  * This function should only be called from a vm_ops->fault handler, and
1589  * in that case the handler should return NULL.
1590  *
1591  * vma cannot be a COW mapping.
1592  *
1593  * As this is called only for pages that do not currently exist, we
1594  * do not need to flush old virtual caches or the TLB.
1595  */
1596 int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
1597                         unsigned long pfn)
1598 {
1599         return vm_insert_pfn_prot(vma, addr, pfn, vma->vm_page_prot);
1600 }
1601 EXPORT_SYMBOL(vm_insert_pfn);
1602 
1603 /**
1604  * vm_insert_pfn_prot - insert single pfn into user vma with specified pgprot
1605  * @vma: user vma to map to
1606  * @addr: target user address of this page
1607  * @pfn: source kernel pfn
1608  * @pgprot: pgprot flags for the inserted page
1609  *
1610  * This is exactly like vm_insert_pfn, except that it allows drivers to
1611  * to override pgprot on a per-page basis.
1612  *
1613  * This only makes sense for IO mappings, and it makes no sense for
1614  * cow mappings.  In general, using multiple vmas is preferable;
1615  * vm_insert_pfn_prot should only be used if using multiple VMAs is
1616  * impractical.
1617  */
1618 int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
1619                         unsigned long pfn, pgprot_t pgprot)
1620 {
1621         int ret;
1622         /*
1623          * Technically, architectures with pte_special can avoid all these
1624          * restrictions (same for remap_pfn_range).  However we would like
1625          * consistency in testing and feature parity among all, so we should
1626          * try to keep these invariants in place for everybody.
1627          */
1628         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
1629         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
1630                                                 (VM_PFNMAP|VM_MIXEDMAP));
1631         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
1632         BUG_ON((vma->vm_flags & VM_MIXEDMAP) && pfn_valid(pfn));
1633 
1634         if (addr < vma->vm_start || addr >= vma->vm_end)
1635                 return -EFAULT;
1636 
1637         track_pfn_insert(vma, &pgprot, __pfn_to_pfn_t(pfn, PFN_DEV));
1638 
1639         ret = insert_pfn(vma, addr, __pfn_to_pfn_t(pfn, PFN_DEV), pgprot);
1640 
1641         return ret;
1642 }
1643 EXPORT_SYMBOL(vm_insert_pfn_prot);
1644 
1645 int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
1646                         pfn_t pfn)
1647 {
1648         pgprot_t pgprot = vma->vm_page_prot;
1649 
1650         BUG_ON(!(vma->vm_flags & VM_MIXEDMAP));
1651 
1652         if (addr < vma->vm_start || addr >= vma->vm_end)
1653                 return -EFAULT;
1654 
1655         track_pfn_insert(vma, &pgprot, pfn);
1656 
1657         /*
1658          * If we don't have pte special, then we have to use the pfn_valid()
1659          * based VM_MIXEDMAP scheme (see vm_normal_page), and thus we *must*
1660          * refcount the page if pfn_valid is true (hence insert_page rather
1661          * than insert_pfn).  If a zero_pfn were inserted into a VM_MIXEDMAP
1662          * without pte special, it would there be refcounted as a normal page.
1663          */
1664         if (!HAVE_PTE_SPECIAL && !pfn_t_devmap(pfn) && pfn_t_valid(pfn)) {
1665                 struct page *page;
1666 
1667                 /*
1668                  * At this point we are committed to insert_page()
1669                  * regardless of whether the caller specified flags that
1670                  * result in pfn_t_has_page() == false.
1671                  */
1672                 page = pfn_to_page(pfn_t_to_pfn(pfn));
1673                 return insert_page(vma, addr, page, pgprot);
1674         }
1675         return insert_pfn(vma, addr, pfn, pgprot);
1676 }
1677 EXPORT_SYMBOL(vm_insert_mixed);
1678 
1679 /*
1680  * maps a range of physical memory into the requested pages. the old
1681  * mappings are removed. any references to nonexistent pages results
1682  * in null mappings (currently treated as "copy-on-access")
1683  */
1684 static int remap_pte_range(struct mm_struct *mm, pmd_t *pmd,
1685                         unsigned long addr, unsigned long end,
1686                         unsigned long pfn, pgprot_t prot)
1687 {
1688         pte_t *pte;
1689         spinlock_t *ptl;
1690 
1691         pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
1692         if (!pte)
1693                 return -ENOMEM;
1694         arch_enter_lazy_mmu_mode();
1695         do {
1696                 BUG_ON(!pte_none(*pte));
1697                 set_pte_at(mm, addr, pte, pte_mkspecial(pfn_pte(pfn, prot)));
1698                 pfn++;
1699         } while (pte++, addr += PAGE_SIZE, addr != end);
1700         arch_leave_lazy_mmu_mode();
1701         pte_unmap_unlock(pte - 1, ptl);
1702         return 0;
1703 }
1704 
1705 static inline int remap_pmd_range(struct mm_struct *mm, pud_t *pud,
1706                         unsigned long addr, unsigned long end,
1707                         unsigned long pfn, pgprot_t prot)
1708 {
1709         pmd_t *pmd;
1710         unsigned long next;
1711 
1712         pfn -= addr >> PAGE_SHIFT;
1713         pmd = pmd_alloc(mm, pud, addr);
1714         if (!pmd)
1715                 return -ENOMEM;
1716         VM_BUG_ON(pmd_trans_huge(*pmd));
1717         do {
1718                 next = pmd_addr_end(addr, end);
1719                 if (remap_pte_range(mm, pmd, addr, next,
1720                                 pfn + (addr >> PAGE_SHIFT), prot))
1721                         return -ENOMEM;
1722         } while (pmd++, addr = next, addr != end);
1723         return 0;
1724 }
1725 
1726 static inline int remap_pud_range(struct mm_struct *mm, pgd_t *pgd,
1727                         unsigned long addr, unsigned long end,
1728                         unsigned long pfn, pgprot_t prot)
1729 {
1730         pud_t *pud;
1731         unsigned long next;
1732 
1733         pfn -= addr >> PAGE_SHIFT;
1734         pud = pud_alloc(mm, pgd, addr);
1735         if (!pud)
1736                 return -ENOMEM;
1737         do {
1738                 next = pud_addr_end(addr, end);
1739                 if (remap_pmd_range(mm, pud, addr, next,
1740                                 pfn + (addr >> PAGE_SHIFT), prot))
1741                         return -ENOMEM;
1742         } while (pud++, addr = next, addr != end);
1743         return 0;
1744 }
1745 
1746 /**
1747  * remap_pfn_range - remap kernel memory to userspace
1748  * @vma: user vma to map to
1749  * @addr: target user address to start at
1750  * @pfn: physical address of kernel memory
1751  * @size: size of map area
1752  * @prot: page protection flags for this mapping
1753  *
1754  *  Note: this is only safe if the mm semaphore is held when called.
1755  */
1756 int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
1757                     unsigned long pfn, unsigned long size, pgprot_t prot)
1758 {
1759         pgd_t *pgd;
1760         unsigned long next;
1761         unsigned long end = addr + PAGE_ALIGN(size);
1762         struct mm_struct *mm = vma->vm_mm;
1763         unsigned long remap_pfn = pfn;
1764         int err;
1765 
1766         /*
1767          * Physically remapped pages are special. Tell the
1768          * rest of the world about it:
1769          *   VM_IO tells people not to look at these pages
1770          *      (accesses can have side effects).
1771          *   VM_PFNMAP tells the core MM that the base pages are just
1772          *      raw PFN mappings, and do not have a "struct page" associated
1773          *      with them.
1774          *   VM_DONTEXPAND
1775          *      Disable vma merging and expanding with mremap().
1776          *   VM_DONTDUMP
1777          *      Omit vma from core dump, even when VM_IO turned off.
1778          *
1779          * There's a horrible special case to handle copy-on-write
1780          * behaviour that some programs depend on. We mark the "original"
1781          * un-COW'ed pages by matching them up with "vma->vm_pgoff".
1782          * See vm_normal_page() for details.
1783          */
1784         if (is_cow_mapping(vma->vm_flags)) {
1785                 if (addr != vma->vm_start || end != vma->vm_end)
1786                         return -EINVAL;
1787                 vma->vm_pgoff = pfn;
1788         }
1789 
1790         err = track_pfn_remap(vma, &prot, remap_pfn, addr, PAGE_ALIGN(size));
1791         if (err)
1792                 return -EINVAL;
1793 
1794         vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
1795 
1796         BUG_ON(addr >= end);
1797         pfn -= addr >> PAGE_SHIFT;
1798         pgd = pgd_offset(mm, addr);
1799         flush_cache_range(vma, addr, end);
1800         do {
1801                 next = pgd_addr_end(addr, end);
1802                 err = remap_pud_range(mm, pgd, addr, next,
1803                                 pfn + (addr >> PAGE_SHIFT), prot);
1804                 if (err)
1805                         break;
1806         } while (pgd++, addr = next, addr != end);
1807 
1808         if (err)
1809                 untrack_pfn(vma, remap_pfn, PAGE_ALIGN(size));
1810 
1811         return err;
1812 }
1813 EXPORT_SYMBOL(remap_pfn_range);
1814 
1815 /**
1816  * vm_iomap_memory - remap memory to userspace
1817  * @vma: user vma to map to
1818  * @start: start of area
1819  * @len: size of area
1820  *
1821  * This is a simplified io_remap_pfn_range() for common driver use. The
1822  * driver just needs to give us the physical memory range to be mapped,
1823  * we'll figure out the rest from the vma information.
1824  *
1825  * NOTE! Some drivers might want to tweak vma->vm_page_prot first to get
1826  * whatever write-combining details or similar.
1827  */
1828 int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len)
1829 {
1830         unsigned long vm_len, pfn, pages;
1831 
1832         /* Check that the physical memory area passed in looks valid */
1833         if (start + len < start)
1834                 return -EINVAL;
1835         /*
1836          * You *really* shouldn't map things that aren't page-aligned,
1837          * but we've historically allowed it because IO memory might
1838          * just have smaller alignment.
1839          */
1840         len += start & ~PAGE_MASK;
1841         pfn = start >> PAGE_SHIFT;
1842         pages = (len + ~PAGE_MASK) >> PAGE_SHIFT;
1843         if (pfn + pages < pfn)
1844                 return -EINVAL;
1845 
1846         /* We start the mapping 'vm_pgoff' pages into the area */
1847         if (vma->vm_pgoff > pages)
1848                 return -EINVAL;
1849         pfn += vma->vm_pgoff;
1850         pages -= vma->vm_pgoff;
1851 
1852         /* Can we fit all of the mapping? */
1853         vm_len = vma->vm_end - vma->vm_start;
1854         if (vm_len >> PAGE_SHIFT > pages)
1855                 return -EINVAL;
1856 
1857         /* Ok, let it rip */
1858         return io_remap_pfn_range(vma, vma->vm_start, pfn, vm_len, vma->vm_page_prot);
1859 }
1860 EXPORT_SYMBOL(vm_iomap_memory);
1861 
1862 static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
1863                                      unsigned long addr, unsigned long end,
1864                                      pte_fn_t fn, void *data)
1865 {
1866         pte_t *pte;
1867         int err;
1868         pgtable_t token;
1869         spinlock_t *uninitialized_var(ptl);
1870 
1871         pte = (mm == &init_mm) ?
1872                 pte_alloc_kernel(pmd, addr) :
1873                 pte_alloc_map_lock(mm, pmd, addr, &ptl);
1874         if (!pte)
1875                 return -ENOMEM;
1876 
1877         BUG_ON(pmd_huge(*pmd));
1878 
1879         arch_enter_lazy_mmu_mode();
1880 
1881         token = pmd_pgtable(*pmd);
1882 
1883         do {
1884                 err = fn(pte++, token, addr, data);
1885                 if (err)
1886                         break;
1887         } while (addr += PAGE_SIZE, addr != end);
1888 
1889         arch_leave_lazy_mmu_mode();
1890 
1891         if (mm != &init_mm)
1892                 pte_unmap_unlock(pte-1, ptl);
1893         return err;
1894 }
1895 
1896 static int apply_to_pmd_range(struct mm_struct *mm, pud_t *pud,
1897                                      unsigned long addr, unsigned long end,
1898                                      pte_fn_t fn, void *data)
1899 {
1900         pmd_t *pmd;
1901         unsigned long next;
1902         int err;
1903 
1904         BUG_ON(pud_huge(*pud));
1905 
1906         pmd = pmd_alloc(mm, pud, addr);
1907         if (!pmd)
1908                 return -ENOMEM;
1909         do {
1910                 next = pmd_addr_end(addr, end);
1911                 err = apply_to_pte_range(mm, pmd, addr, next, fn, data);
1912                 if (err)
1913                         break;
1914         } while (pmd++, addr = next, addr != end);
1915         return err;
1916 }
1917 
1918 static int apply_to_pud_range(struct mm_struct *mm, pgd_t *pgd,
1919                                      unsigned long addr, unsigned long end,
1920                                      pte_fn_t fn, void *data)
1921 {
1922         pud_t *pud;
1923         unsigned long next;
1924         int err;
1925 
1926         pud = pud_alloc(mm, pgd, addr);
1927         if (!pud)
1928                 return -ENOMEM;
1929         do {
1930                 next = pud_addr_end(addr, end);
1931                 err = apply_to_pmd_range(mm, pud, addr, next, fn, data);
1932                 if (err)
1933                         break;
1934         } while (pud++, addr = next, addr != end);
1935         return err;
1936 }
1937 
1938 /*
1939  * Scan a region of virtual memory, filling in page tables as necessary
1940  * and calling a provided function on each leaf page table.
1941  */
1942 int apply_to_page_range(struct mm_struct *mm, unsigned long addr,
1943                         unsigned long size, pte_fn_t fn, void *data)
1944 {
1945         pgd_t *pgd;
1946         unsigned long next;
1947         unsigned long end = addr + size;
1948         int err;
1949 
1950         if (WARN_ON(addr >= end))
1951                 return -EINVAL;
1952 
1953         pgd = pgd_offset(mm, addr);
1954         do {
1955                 next = pgd_addr_end(addr, end);
1956                 err = apply_to_pud_range(mm, pgd, addr, next, fn, data);
1957                 if (err)
1958                         break;
1959         } while (pgd++, addr = next, addr != end);
1960 
1961         return err;
1962 }
1963 EXPORT_SYMBOL_GPL(apply_to_page_range);
1964 
1965 /*
1966  * handle_pte_fault chooses page fault handler according to an entry which was
1967  * read non-atomically.  Before making any commitment, on those architectures
1968  * or configurations (e.g. i386 with PAE) which might give a mix of unmatched
1969  * parts, do_swap_page must check under lock before unmapping the pte and
1970  * proceeding (but do_wp_page is only called after already making such a check;
1971  * and do_anonymous_page can safely check later on).
1972  */
1973 static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd,
1974                                 pte_t *page_table, pte_t orig_pte)
1975 {
1976         int same = 1;
1977 #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
1978         if (sizeof(pte_t) > sizeof(unsigned long)) {
1979                 spinlock_t *ptl = pte_lockptr(mm, pmd);
1980                 spin_lock(ptl);
1981                 same = pte_same(*page_table, orig_pte);
1982                 spin_unlock(ptl);
1983         }
1984 #endif
1985         pte_unmap(page_table);
1986         return same;
1987 }
1988 
1989 static inline void cow_user_page(struct page *dst, struct page *src, unsigned long va, struct vm_area_struct *vma)
1990 {
1991         debug_dma_assert_idle(src);
1992 
1993         /*
1994          * If the source page was a PFN mapping, we don't have
1995          * a "struct page" for it. We do a best-effort copy by
1996          * just copying from the original user address. If that
1997          * fails, we just zero-fill it. Live with it.
1998          */
1999         if (unlikely(!src)) {
2000                 void *kaddr = kmap_atomic(dst);
2001                 void __user *uaddr = (void __user *)(va & PAGE_MASK);
2002 
2003                 /*
2004                  * This really shouldn't fail, because the page is there
2005                  * in the page tables. But it might just be unreadable,
2006                  * in which case we just give up and fill the result with
2007                  * zeroes.
2008                  */
2009                 if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE))
2010                         clear_page(kaddr);
2011                 kunmap_atomic(kaddr);
2012                 flush_dcache_page(dst);
2013         } else
2014                 copy_user_highpage(dst, src, va, vma);
2015 }
2016 
2017 static gfp_t __get_fault_gfp_mask(struct vm_area_struct *vma)
2018 {
2019         struct file *vm_file = vma->vm_file;
2020 
2021         if (vm_file)
2022                 return mapping_gfp_mask(vm_file->f_mapping) | __GFP_FS | __GFP_IO;
2023 
2024         /*
2025          * Special mappings (e.g. VDSO) do not have any file so fake
2026          * a default GFP_KERNEL for them.
2027          */
2028         return GFP_KERNEL;
2029 }
2030 
2031 /*
2032  * Notify the address space that the page is about to become writable so that
2033  * it can prohibit this or wait for the page to get into an appropriate state.
2034  *
2035  * We do this without the lock held, so that it can sleep if it needs to.
2036  */
2037 static int do_page_mkwrite(struct vm_fault *vmf)
2038 {
2039         int ret;
2040         struct page *page = vmf->page;
2041         unsigned int old_flags = vmf->flags;
2042 
2043         vmf->flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
2044 
2045         ret = vmf->vma->vm_ops->page_mkwrite(vmf->vma, vmf);
2046         /* Restore original flags so that caller is not surprised */
2047         vmf->flags = old_flags;
2048         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))
2049                 return ret;
2050         if (unlikely(!(ret & VM_FAULT_LOCKED))) {
2051                 lock_page(page);
2052                 if (!page->mapping) {
2053                         unlock_page(page);
2054                         return 0; /* retry */
2055                 }
2056                 ret |= VM_FAULT_LOCKED;
2057         } else
2058                 VM_BUG_ON_PAGE(!PageLocked(page), page);
2059         return ret;
2060 }
2061 
2062 /*
2063  * Handle dirtying of a page in shared file mapping on a write fault.
2064  *
2065  * The function expects the page to be locked and unlocks it.
2066  */
2067 static void fault_dirty_shared_page(struct vm_area_struct *vma,
2068                                     struct page *page)
2069 {
2070         struct address_space *mapping;
2071         bool dirtied;
2072         bool page_mkwrite = vma->vm_ops && vma->vm_ops->page_mkwrite;
2073 
2074         dirtied = set_page_dirty(page);
2075         VM_BUG_ON_PAGE(PageAnon(page), page);
2076         /*
2077          * Take a local copy of the address_space - page.mapping may be zeroed
2078          * by truncate after unlock_page().   The address_space itself remains
2079          * pinned by vma->vm_file's reference.  We rely on unlock_page()'s
2080          * release semantics to prevent the compiler from undoing this copying.
2081          */
2082         mapping = page_rmapping(page);
2083         unlock_page(page);
2084 
2085         if ((dirtied || page_mkwrite) && mapping) {
2086                 /*
2087                  * Some device drivers do not set page.mapping
2088                  * but still dirty their pages
2089                  */
2090                 balance_dirty_pages_ratelimited(mapping);
2091         }
2092 
2093         if (!page_mkwrite)
2094                 file_update_time(vma->vm_file);
2095 }
2096 
2097 /*
2098  * Handle write page faults for pages that can be reused in the current vma
2099  *
2100  * This can happen either due to the mapping being with the VM_SHARED flag,
2101  * or due to us being the last reference standing to the page. In either
2102  * case, all we need to do here is to mark the page as writable and update
2103  * any related book-keeping.
2104  */
2105 static inline void wp_page_reuse(struct vm_fault *vmf)
2106         __releases(vmf->ptl)
2107 {
2108         struct vm_area_struct *vma = vmf->vma;
2109         struct page *page = vmf->page;
2110         pte_t entry;
2111         /*
2112          * Clear the pages cpupid information as the existing
2113          * information potentially belongs to a now completely
2114          * unrelated process.
2115          */
2116         if (page)
2117                 page_cpupid_xchg_last(page, (1 << LAST_CPUPID_SHIFT) - 1);
2118 
2119         flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
2120         entry = pte_mkyoung(vmf->orig_pte);
2121         entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2122         if (ptep_set_access_flags(vma, vmf->address, vmf->pte, entry, 1))
2123                 update_mmu_cache(vma, vmf->address, vmf->pte);
2124         pte_unmap_unlock(vmf->pte, vmf->ptl);
2125 }
2126 
2127 /*
2128  * Handle the case of a page which we actually need to copy to a new page.
2129  *
2130  * Called with mmap_sem locked and the old page referenced, but
2131  * without the ptl held.
2132  *
2133  * High level logic flow:
2134  *
2135  * - Allocate a page, copy the content of the old page to the new one.
2136  * - Handle book keeping and accounting - cgroups, mmu-notifiers, etc.
2137  * - Take the PTL. If the pte changed, bail out and release the allocated page
2138  * - If the pte is still the way we remember it, update the page table and all
2139  *   relevant references. This includes dropping the reference the page-table
2140  *   held to the old page, as well as updating the rmap.
2141  * - In any case, unlock the PTL and drop the reference we took to the old page.
2142  */
2143 static int wp_page_copy(struct vm_fault *vmf)
2144 {
2145         struct vm_area_struct *vma = vmf->vma;
2146         struct mm_struct *mm = vma->vm_mm;
2147         struct page *old_page = vmf->page;
2148         struct page *new_page = NULL;
2149         pte_t entry;
2150         int page_copied = 0;
2151         const unsigned long mmun_start = vmf->address & PAGE_MASK;
2152         const unsigned long mmun_end = mmun_start + PAGE_SIZE;
2153         struct mem_cgroup *memcg;
2154 
2155         if (unlikely(anon_vma_prepare(vma)))
2156                 goto oom;
2157 
2158         if (is_zero_pfn(pte_pfn(vmf->orig_pte))) {
2159                 new_page = alloc_zeroed_user_highpage_movable(vma,
2160                                                               vmf->address);
2161                 if (!new_page)
2162                         goto oom;
2163         } else {
2164                 new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma,
2165                                 vmf->address);
2166                 if (!new_page)
2167                         goto oom;
2168                 cow_user_page(new_page, old_page, vmf->address, vma);
2169         }
2170 
2171         if (mem_cgroup_try_charge(new_page, mm, GFP_KERNEL, &memcg, false))
2172                 goto oom_free_new;
2173 
2174         __SetPageUptodate(new_page);
2175 
2176         mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2177 
2178         /*
2179          * Re-check the pte - we dropped the lock
2180          */
2181         vmf->pte = pte_offset_map_lock(mm, vmf->pmd, vmf->address, &vmf->ptl);
2182         if (likely(pte_same(*vmf->pte, vmf->orig_pte))) {
2183                 if (old_page) {
2184                         if (!PageAnon(old_page)) {
2185                                 dec_mm_counter_fast(mm,
2186                                                 mm_counter_file(old_page));
2187                                 inc_mm_counter_fast(mm, MM_ANONPAGES);
2188                         }
2189                 } else {
2190                         inc_mm_counter_fast(mm, MM_ANONPAGES);
2191                 }
2192                 flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
2193                 entry = mk_pte(new_page, vma->vm_page_prot);
2194                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2195                 /*
2196                  * Clear the pte entry and flush it first, before updating the
2197                  * pte with the new entry. This will avoid a race condition
2198                  * seen in the presence of one thread doing SMC and another
2199                  * thread doing COW.
2200                  */
2201                 ptep_clear_flush_notify(vma, vmf->address, vmf->pte);
2202                 page_add_new_anon_rmap(new_page, vma, vmf->address, false);
2203                 mem_cgroup_commit_charge(new_page, memcg, false, false);
2204                 lru_cache_add_active_or_unevictable(new_page, vma);
2205                 /*
2206                  * We call the notify macro here because, when using secondary
2207                  * mmu page tables (such as kvm shadow page tables), we want the
2208                  * new page to be mapped directly into the secondary page table.
2209                  */
2210                 set_pte_at_notify(mm, vmf->address, vmf->pte, entry);
2211                 update_mmu_cache(vma, vmf->address, vmf->pte);
2212                 if (old_page) {
2213                         /*
2214                          * Only after switching the pte to the new page may
2215                          * we remove the mapcount here. Otherwise another
2216                          * process may come and find the rmap count decremented
2217                          * before the pte is switched to the new page, and
2218                          * "reuse" the old page writing into it while our pte
2219                          * here still points into it and can be read by other
2220                          * threads.
2221                          *
2222                          * The critical issue is to order this
2223                          * page_remove_rmap with the ptp_clear_flush above.
2224                          * Those stores are ordered by (if nothing else,)
2225                          * the barrier present in the atomic_add_negative
2226                          * in page_remove_rmap.
2227                          *
2228                          * Then the TLB flush in ptep_clear_flush ensures that
2229                          * no process can access the old page before the
2230                          * decremented mapcount is visible. And the old page
2231                          * cannot be reused until after the decremented
2232                          * mapcount is visible. So transitively, TLBs to
2233                          * old page will be flushed before it can be reused.
2234                          */
2235                         page_remove_rmap(old_page, false);
2236                 }
2237 
2238                 /* Free the old page.. */
2239                 new_page = old_page;
2240                 page_copied = 1;
2241         } else {
2242                 mem_cgroup_cancel_charge(new_page, memcg, false);
2243         }
2244 
2245         if (new_page)
2246                 put_page(new_page);
2247 
2248         pte_unmap_unlock(vmf->pte, vmf->ptl);
2249         mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2250         if (old_page) {
2251                 /*
2252                  * Don't let another task, with possibly unlocked vma,
2253                  * keep the mlocked page.
2254                  */
2255                 if (page_copied && (vma->vm_flags & VM_LOCKED)) {
2256                         lock_page(old_page);    /* LRU manipulation */
2257                         if (PageMlocked(old_page))
2258                                 munlock_vma_page(old_page);
2259                         unlock_page(old_page);
2260                 }
2261                 put_page(old_page);
2262         }
2263         return page_copied ? VM_FAULT_WRITE : 0;
2264 oom_free_new:
2265         put_page(new_page);
2266 oom:
2267         if (old_page)
2268                 put_page(old_page);
2269         return VM_FAULT_OOM;
2270 }
2271 
2272 /**
2273  * finish_mkwrite_fault - finish page fault for a shared mapping, making PTE
2274  *                        writeable once the page is prepared
2275  *
2276  * @vmf: structure describing the fault
2277  *
2278  * This function handles all that is needed to finish a write page fault in a
2279  * shared mapping due to PTE being read-only once the mapped page is prepared.
2280  * It handles locking of PTE and modifying it. The function returns
2281  * VM_FAULT_WRITE on success, 0 when PTE got changed before we acquired PTE
2282  * lock.
2283  *
2284  * The function expects the page to be locked or other protection against
2285  * concurrent faults / writeback (such as DAX radix tree locks).
2286  */
2287 int finish_mkwrite_fault(struct vm_fault *vmf)
2288 {
2289         WARN_ON_ONCE(!(vmf->vma->vm_flags & VM_SHARED));
2290         vmf->pte = pte_offset_map_lock(vmf->vma->vm_mm, vmf->pmd, vmf->address,
2291                                        &vmf->ptl);
2292         /*
2293          * We might have raced with another page fault while we released the
2294          * pte_offset_map_lock.
2295          */
2296         if (!pte_same(*vmf->pte, vmf->orig_pte)) {
2297                 pte_unmap_unlock(vmf->pte, vmf->ptl);
2298                 return VM_FAULT_NOPAGE;
2299         }
2300         wp_page_reuse(vmf);
2301         return 0;
2302 }
2303 
2304 /*
2305  * Handle write page faults for VM_MIXEDMAP or VM_PFNMAP for a VM_SHARED
2306  * mapping
2307  */
2308 static int wp_pfn_shared(struct vm_fault *vmf)
2309 {
2310         struct vm_area_struct *vma = vmf->vma;
2311 
2312         if (vma->vm_ops && vma->vm_ops->pfn_mkwrite) {
2313                 int ret;
2314 
2315                 pte_unmap_unlock(vmf->pte, vmf->ptl);
2316                 vmf->flags |= FAULT_FLAG_MKWRITE;
2317                 ret = vma->vm_ops->pfn_mkwrite(vma, vmf);
2318                 if (ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))
2319                         return ret;
2320                 return finish_mkwrite_fault(vmf);
2321         }
2322         wp_page_reuse(vmf);
2323         return VM_FAULT_WRITE;
2324 }
2325 
2326 static int wp_page_shared(struct vm_fault *vmf)
2327         __releases(vmf->ptl)
2328 {
2329         struct vm_area_struct *vma = vmf->vma;
2330 
2331         get_page(vmf->page);
2332 
2333         if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
2334                 int tmp;
2335 
2336                 pte_unmap_unlock(vmf->pte, vmf->ptl);
2337                 tmp = do_page_mkwrite(vmf);
2338                 if (unlikely(!tmp || (tmp &
2339                                       (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
2340                         put_page(vmf->page);
2341                         return tmp;
2342                 }
2343                 tmp = finish_mkwrite_fault(vmf);
2344                 if (unlikely(tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
2345                         unlock_page(vmf->page);
2346                         put_page(vmf->page);
2347                         return tmp;
2348                 }
2349         } else {
2350                 wp_page_reuse(vmf);
2351                 lock_page(vmf->page);
2352         }
2353         fault_dirty_shared_page(vma, vmf->page);
2354         put_page(vmf->page);
2355 
2356         return VM_FAULT_WRITE;
2357 }
2358 
2359 /*
2360  * This routine handles present pages, when users try to write
2361  * to a shared page. It is done by copying the page to a new address
2362  * and decrementing the shared-page counter for the old page.
2363  *
2364  * Note that this routine assumes that the protection checks have been
2365  * done by the caller (the low-level page fault routine in most cases).
2366  * Thus we can safely just mark it writable once we've done any necessary
2367  * COW.
2368  *
2369  * We also mark the page dirty at this point even though the page will
2370  * change only once the write actually happens. This avoids a few races,
2371  * and potentially makes it more efficient.
2372  *
2373  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2374  * but allow concurrent faults), with pte both mapped and locked.
2375  * We return with mmap_sem still held, but pte unmapped and unlocked.
2376  */
2377 static int do_wp_page(struct vm_fault *vmf)
2378         __releases(vmf->ptl)
2379 {
2380         struct vm_area_struct *vma = vmf->vma;
2381 
2382         vmf->page = vm_normal_page(vma, vmf->address, vmf->orig_pte);
2383         if (!vmf->page) {
2384                 /*
2385                  * VM_MIXEDMAP !pfn_valid() case, or VM_SOFTDIRTY clear on a
2386                  * VM_PFNMAP VMA.
2387                  *
2388                  * We should not cow pages in a shared writeable mapping.
2389                  * Just mark the pages writable and/or call ops->pfn_mkwrite.
2390                  */
2391                 if ((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
2392                                      (VM_WRITE|VM_SHARED))
2393                         return wp_pfn_shared(vmf);
2394 
2395                 pte_unmap_unlock(vmf->pte, vmf->ptl);
2396                 return wp_page_copy(vmf);
2397         }
2398 
2399         /*
2400          * Take out anonymous pages first, anonymous shared vmas are
2401          * not dirty accountable.
2402          */
2403         if (PageAnon(vmf->page) && !PageKsm(vmf->page)) {
2404                 int total_mapcount;
2405                 if (!trylock_page(vmf->page)) {
2406                         get_page(vmf->page);
2407                         pte_unmap_unlock(vmf->pte, vmf->ptl);
2408                         lock_page(vmf->page);
2409                         vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
2410                                         vmf->address, &vmf->ptl);
2411                         if (!pte_same(*vmf->pte, vmf->orig_pte)) {
2412                                 unlock_page(vmf->page);
2413                                 pte_unmap_unlock(vmf->pte, vmf->ptl);
2414                                 put_page(vmf->page);
2415                                 return 0;
2416                         }
2417                         put_page(vmf->page);
2418                 }
2419                 if (reuse_swap_page(vmf->page, &total_mapcount)) {
2420                         if (total_mapcount == 1) {
2421                                 /*
2422                                  * The page is all ours. Move it to
2423                                  * our anon_vma so the rmap code will
2424                                  * not search our parent or siblings.
2425                                  * Protected against the rmap code by
2426                                  * the page lock.
2427                                  */
2428                                 page_move_anon_rmap(vmf->page, vma);
2429                         }
2430                         unlock_page(vmf->page);
2431                         wp_page_reuse(vmf);
2432                         return VM_FAULT_WRITE;
2433                 }
2434                 unlock_page(vmf->page);
2435         } else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
2436                                         (VM_WRITE|VM_SHARED))) {
2437                 return wp_page_shared(vmf);
2438         }
2439 
2440         /*
2441          * Ok, we need to copy. Oh, well..
2442          */
2443         get_page(vmf->page);
2444 
2445         pte_unmap_unlock(vmf->pte, vmf->ptl);
2446         return wp_page_copy(vmf);
2447 }
2448 
2449 static void unmap_mapping_range_vma(struct vm_area_struct *vma,
2450                 unsigned long start_addr, unsigned long end_addr,
2451                 struct zap_details *details)
2452 {
2453         zap_page_range_single(vma, start_addr, end_addr - start_addr, details);
2454 }
2455 
2456 static inline void unmap_mapping_range_tree(struct rb_root *root,
2457                                             struct zap_details *details)
2458 {
2459         struct vm_area_struct *vma;
2460         pgoff_t vba, vea, zba, zea;
2461 
2462         vma_interval_tree_foreach(vma, root,
2463                         details->first_index, details->last_index) {
2464 
2465                 vba = vma->vm_pgoff;
2466                 vea = vba + vma_pages(vma) - 1;
2467                 zba = details->first_index;
2468                 if (zba < vba)
2469                         zba = vba;
2470                 zea = details->last_index;
2471                 if (zea > vea)
2472                         zea = vea;
2473 
2474                 unmap_mapping_range_vma(vma,
2475                         ((zba - vba) << PAGE_SHIFT) + vma->vm_start,
2476                         ((zea - vba + 1) << PAGE_SHIFT) + vma->vm_start,
2477                                 details);
2478         }
2479 }
2480 
2481 /**
2482  * unmap_mapping_range - unmap the portion of all mmaps in the specified
2483  * address_space corresponding to the specified page range in the underlying
2484  * file.
2485  *
2486  * @mapping: the address space containing mmaps to be unmapped.
2487  * @holebegin: byte in first page to unmap, relative to the start of
2488  * the underlying file.  This will be rounded down to a PAGE_SIZE
2489  * boundary.  Note that this is different from truncate_pagecache(), which
2490  * must keep the partial page.  In contrast, we must get rid of
2491  * partial pages.
2492  * @holelen: size of prospective hole in bytes.  This will be rounded
2493  * up to a PAGE_SIZE boundary.  A holelen of zero truncates to the
2494  * end of the file.
2495  * @even_cows: 1 when truncating a file, unmap even private COWed pages;
2496  * but 0 when invalidating pagecache, don't throw away private data.
2497  */
2498 void unmap_mapping_range(struct address_space *mapping,
2499                 loff_t const holebegin, loff_t const holelen, int even_cows)
2500 {
2501         struct zap_details details = { };
2502         pgoff_t hba = holebegin >> PAGE_SHIFT;
2503         pgoff_t hlen = (holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
2504 
2505         /* Check for overflow. */
2506         if (sizeof(holelen) > sizeof(hlen)) {
2507                 long long holeend =
2508                         (holebegin + holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
2509                 if (holeend & ~(long long)ULONG_MAX)
2510                         hlen = ULONG_MAX - hba + 1;
2511         }
2512 
2513         details.check_mapping = even_cows? NULL: mapping;
2514         details.first_index = hba;
2515         details.last_index = hba + hlen - 1;
2516         if (details.last_index < details.first_index)
2517                 details.last_index = ULONG_MAX;
2518 
2519         i_mmap_lock_write(mapping);
2520         if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap)))
2521                 unmap_mapping_range_tree(&mapping->i_mmap, &details);
2522         i_mmap_unlock_write(mapping);
2523 }
2524 EXPORT_SYMBOL(unmap_mapping_range);
2525 
2526 /*
2527  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2528  * but allow concurrent faults), and pte mapped but not yet locked.
2529  * We return with pte unmapped and unlocked.
2530  *
2531  * We return with the mmap_sem locked or unlocked in the same cases
2532  * as does filemap_fault().
2533  */
2534 int do_swap_page(struct vm_fault *vmf)
2535 {
2536         struct vm_area_struct *vma = vmf->vma;
2537         struct page *page, *swapcache;
2538         struct mem_cgroup *memcg;
2539         swp_entry_t entry;
2540         pte_t pte;
2541         int locked;
2542         int exclusive = 0;
2543         int ret = 0;
2544 
2545         if (!pte_unmap_same(vma->vm_mm, vmf->pmd, vmf->pte, vmf->orig_pte))
2546                 goto out;
2547 
2548         entry = pte_to_swp_entry(vmf->orig_pte);
2549         if (unlikely(non_swap_entry(entry))) {
2550                 if (is_migration_entry(entry)) {
2551                         migration_entry_wait(vma->vm_mm, vmf->pmd,
2552                                              vmf->address);
2553                 } else if (is_hwpoison_entry(entry)) {
2554                         ret = VM_FAULT_HWPOISON;
2555                 } else {
2556                         print_bad_pte(vma, vmf->address, vmf->orig_pte, NULL);
2557                         ret = VM_FAULT_SIGBUS;
2558                 }
2559                 goto out;
2560         }
2561         delayacct_set_flag(DELAYACCT_PF_SWAPIN);
2562         page = lookup_swap_cache(entry);
2563         if (!page) {
2564                 page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE, vma,
2565                                         vmf->address);
2566                 if (!page) {
2567                         /*
2568                          * Back out if somebody else faulted in this pte
2569                          * while we released the pte lock.
2570                          */
2571                         vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
2572                                         vmf->address, &vmf->ptl);
2573                         if (likely(pte_same(*vmf->pte, vmf->orig_pte)))
2574                                 ret = VM_FAULT_OOM;
2575                         delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
2576                         goto unlock;
2577                 }
2578 
2579                 /* Had to read the page from swap area: Major fault */
2580                 ret = VM_FAULT_MAJOR;
2581                 count_vm_event(PGMAJFAULT);
2582                 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
2583         } else if (PageHWPoison(page)) {
2584                 /*
2585                  * hwpoisoned dirty swapcache pages are kept for killing
2586                  * owner processes (which may be unknown at hwpoison time)
2587                  */
2588                 ret = VM_FAULT_HWPOISON;
2589                 delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
2590                 swapcache = page;
2591                 goto out_release;
2592         }
2593 
2594         swapcache = page;
2595         locked = lock_page_or_retry(page, vma->vm_mm, vmf->flags);
2596 
2597         delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
2598         if (!locked) {
2599                 ret |= VM_FAULT_RETRY;
2600                 goto out_release;
2601         }
2602 
2603         /*
2604          * Make sure try_to_free_swap or reuse_swap_page or swapoff did not
2605          * release the swapcache from under us.  The page pin, and pte_same
2606          * test below, are not enough to exclude that.  Even if it is still
2607          * swapcache, we need to check that the page's swap has not changed.
2608          */
2609         if (unlikely(!PageSwapCache(page) || page_private(page) != entry.val))
2610                 goto out_page;
2611 
2612         page = ksm_might_need_to_copy(page, vma, vmf->address);
2613         if (unlikely(!page)) {
2614                 ret = VM_FAULT_OOM;
2615                 page = swapcache;
2616                 goto out_page;
2617         }
2618 
2619         if (mem_cgroup_try_charge(page, vma->vm_mm, GFP_KERNEL,
2620                                 &memcg, false)) {
2621                 ret = VM_FAULT_OOM;
2622                 goto out_page;
2623         }
2624 
2625         /*
2626          * Back out if somebody else already faulted in this pte.
2627          */
2628         vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address,
2629                         &vmf->ptl);
2630         if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte)))
2631                 goto out_nomap;
2632 
2633         if (unlikely(!PageUptodate(page))) {
2634                 ret = VM_FAULT_SIGBUS;
2635                 goto out_nomap;
2636         }
2637 
2638         /*
2639          * The page isn't present yet, go ahead with the fault.
2640          *
2641          * Be careful about the sequence of operations here.
2642          * To get its accounting right, reuse_swap_page() must be called
2643          * while the page is counted on swap but not yet in mapcount i.e.
2644          * before page_add_anon_rmap() and swap_free(); try_to_free_swap()
2645          * must be called after the swap_free(), or it will never succeed.
2646          */
2647 
2648         inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
2649         dec_mm_counter_fast(vma->vm_mm, MM_SWAPENTS);
2650         pte = mk_pte(page, vma->vm_page_prot);
2651         if ((vmf->flags & FAULT_FLAG_WRITE) && reuse_swap_page(page, NULL)) {
2652                 pte = maybe_mkwrite(pte_mkdirty(pte), vma);
2653                 vmf->flags &= ~FAULT_FLAG_WRITE;
2654                 ret |= VM_FAULT_WRITE;
2655                 exclusive = RMAP_EXCLUSIVE;
2656         }
2657         flush_icache_page(vma, page);
2658         if (pte_swp_soft_dirty(vmf->orig_pte))
2659                 pte = pte_mksoft_dirty(pte);
2660         set_pte_at(vma->vm_mm, vmf->address, vmf->pte, pte);
2661         vmf->orig_pte = pte;
2662         if (page == swapcache) {
2663                 do_page_add_anon_rmap(page, vma, vmf->address, exclusive);
2664                 mem_cgroup_commit_charge(page, memcg, true, false);
2665                 activate_page(page);
2666         } else { /* ksm created a completely new copy */
2667                 page_add_new_anon_rmap(page, vma, vmf->address, false);
2668                 mem_cgroup_commit_charge(page, memcg, false, false);
2669                 lru_cache_add_active_or_unevictable(page, vma);
2670         }
2671 
2672         swap_free(entry);
2673         if (mem_cgroup_swap_full(page) ||
2674             (vma->vm_flags & VM_LOCKED) || PageMlocked(page))
2675                 try_to_free_swap(page);
2676         unlock_page(page);
2677         if (page != swapcache) {
2678                 /*
2679                  * Hold the lock to avoid the swap entry to be reused
2680                  * until we take the PT lock for the pte_same() check
2681                  * (to avoid false positives from pte_same). For
2682                  * further safety release the lock after the swap_free
2683                  * so that the swap count won't change under a
2684                  * parallel locked swapcache.
2685                  */
2686                 unlock_page(swapcache);
2687                 put_page(swapcache);
2688         }
2689 
2690         if (vmf->flags & FAULT_FLAG_WRITE) {
2691                 ret |= do_wp_page(vmf);
2692                 if (ret & VM_FAULT_ERROR)
2693                         ret &= VM_FAULT_ERROR;
2694                 goto out;
2695         }
2696 
2697         /* No need to invalidate - it was non-present before */
2698         update_mmu_cache(vma, vmf->address, vmf->pte);
2699 unlock:
2700         pte_unmap_unlock(vmf->pte, vmf->ptl);
2701 out:
2702         return ret;
2703 out_nomap:
2704         mem_cgroup_cancel_charge(page, memcg, false);
2705         pte_unmap_unlock(vmf->pte, vmf->ptl);
2706 out_page:
2707         unlock_page(page);
2708 out_release:
2709         put_page(page);
2710         if (page != swapcache) {
2711                 unlock_page(swapcache);
2712                 put_page(swapcache);
2713         }
2714         return ret;
2715 }
2716 
2717 /*
2718  * This is like a special single-page "expand_{down|up}wards()",
2719  * except we must first make sure that 'address{-|+}PAGE_SIZE'
2720  * doesn't hit another vma.
2721  */
2722 static inline int check_stack_guard_page(struct vm_area_struct *vma, unsigned long address)
2723 {
2724         address &= PAGE_MASK;
2725         if ((vma->vm_flags & VM_GROWSDOWN) && address == vma->vm_start) {
2726                 struct vm_area_struct *prev = vma->vm_prev;
2727 
2728                 /*
2729                  * Is there a mapping abutting this one below?
2730                  *
2731                  * That's only ok if it's the same stack mapping
2732                  * that has gotten split..
2733                  */
2734                 if (prev && prev->vm_end == address)
2735                         return prev->vm_flags & VM_GROWSDOWN ? 0 : -ENOMEM;
2736 
2737                 return expand_downwards(vma, address - PAGE_SIZE);
2738         }
2739         if ((vma->vm_flags & VM_GROWSUP) && address + PAGE_SIZE == vma->vm_end) {
2740                 struct vm_area_struct *next = vma->vm_next;
2741 
2742                 /* As VM_GROWSDOWN but s/below/above/ */
2743                 if (next && next->vm_start == address + PAGE_SIZE)
2744                         return next->vm_flags & VM_GROWSUP ? 0 : -ENOMEM;
2745 
2746                 return expand_upwards(vma, address + PAGE_SIZE);
2747         }
2748         return 0;
2749 }
2750 
2751 /*
2752  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2753  * but allow concurrent faults), and pte mapped but not yet locked.
2754  * We return with mmap_sem still held, but pte unmapped and unlocked.
2755  */
2756 static int do_anonymous_page(struct vm_fault *vmf)
2757 {
2758         struct vm_area_struct *vma = vmf->vma;
2759         struct mem_cgroup *memcg;
2760         struct page *page;
2761         pte_t entry;
2762 
2763         /* File mapping without ->vm_ops ? */
2764         if (vma->vm_flags & VM_SHARED)
2765                 return VM_FAULT_SIGBUS;
2766 
2767         /* Check if we need to add a guard page to the stack */
2768         if (check_stack_guard_page(vma, vmf->address) < 0)
2769                 return VM_FAULT_SIGSEGV;
2770 
2771         /*
2772          * Use pte_alloc() instead of pte_alloc_map().  We can't run
2773          * pte_offset_map() on pmds where a huge pmd might be created
2774          * from a different thread.
2775          *
2776          * pte_alloc_map() is safe to use under down_write(mmap_sem) or when
2777          * parallel threads are excluded by other means.
2778          *
2779          * Here we only have down_read(mmap_sem).
2780          */
2781         if (pte_alloc(vma->vm_mm, vmf->pmd, vmf->address))
2782                 return VM_FAULT_OOM;
2783 
2784         /* See the comment in pte_alloc_one_map() */
2785         if (unlikely(pmd_trans_unstable(vmf->pmd)))
2786                 return 0;
2787 
2788         /* Use the zero-page for reads */
2789         if (!(vmf->flags & FAULT_FLAG_WRITE) &&
2790                         !mm_forbids_zeropage(vma->vm_mm)) {
2791                 entry = pte_mkspecial(pfn_pte(my_zero_pfn(vmf->address),
2792                                                 vma->vm_page_prot));
2793                 vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
2794                                 vmf->address, &vmf->ptl);
2795                 if (!pte_none(*vmf->pte))
2796                         goto unlock;
2797                 /* Deliver the page fault to userland, check inside PT lock */
2798                 if (userfaultfd_missing(vma)) {
2799                         pte_unmap_unlock(vmf->pte, vmf->ptl);
2800                         return handle_userfault(vmf, VM_UFFD_MISSING);
2801                 }
2802                 goto setpte;
2803         }
2804 
2805         /* Allocate our own private page. */
2806         if (unlikely(anon_vma_prepare(vma)))
2807                 goto oom;
2808         page = alloc_zeroed_user_highpage_movable(vma, vmf->address);
2809         if (!page)
2810                 goto oom;
2811 
2812         if (mem_cgroup_try_charge(page, vma->vm_mm, GFP_KERNEL, &memcg, false))
2813                 goto oom_free_page;
2814 
2815         /*
2816          * The memory barrier inside __SetPageUptodate makes sure that
2817          * preceeding stores to the page contents become visible before
2818          * the set_pte_at() write.
2819          */
2820         __SetPageUptodate(page);
2821 
2822         entry = mk_pte(page, vma->vm_page_prot);
2823         if (vma->vm_flags & VM_WRITE)
2824                 entry = pte_mkwrite(pte_mkdirty(entry));
2825 
2826         vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address,
2827                         &vmf->ptl);
2828         if (!pte_none(*vmf->pte))
2829                 goto release;
2830 
2831         /* Deliver the page fault to userland, check inside PT lock */
2832         if (userfaultfd_missing(vma)) {
2833                 pte_unmap_unlock(vmf->pte, vmf->ptl);
2834                 mem_cgroup_cancel_charge(page, memcg, false);
2835                 put_page(page);
2836                 return handle_userfault(vmf, VM_UFFD_MISSING);
2837         }
2838 
2839         inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
2840         page_add_new_anon_rmap(page, vma, vmf->address, false);
2841         mem_cgroup_commit_charge(page, memcg, false, false);
2842         lru_cache_add_active_or_unevictable(page, vma);
2843 setpte:
2844         set_pte_at(vma->vm_mm, vmf->address, vmf->pte, entry);
2845 
2846         /* No need to invalidate - it was non-present before */
2847         update_mmu_cache(vma, vmf->address, vmf->pte);
2848 unlock:
2849         pte_unmap_unlock(vmf->pte, vmf->ptl);
2850         return 0;
2851 release:
2852         mem_cgroup_cancel_charge(page, memcg, false);
2853         put_page(page);
2854         goto unlock;
2855 oom_free_page:
2856         put_page(page);
2857 oom:
2858         return VM_FAULT_OOM;
2859 }
2860 
2861 /*
2862  * The mmap_sem must have been held on entry, and may have been
2863  * released depending on flags and vma->vm_ops->fault() return value.
2864  * See filemap_fault() and __lock_page_retry().
2865  */
2866 static int __do_fault(struct vm_fault *vmf)
2867 {
2868         struct vm_area_struct *vma = vmf->vma;
2869         int ret;
2870 
2871         ret = vma->vm_ops->fault(vma, vmf);
2872         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY |
2873                             VM_FAULT_DONE_COW)))
2874                 return ret;
2875 
2876         if (unlikely(PageHWPoison(vmf->page))) {
2877                 if (ret & VM_FAULT_LOCKED)
2878                         unlock_page(vmf->page);
2879                 put_page(vmf->page);
2880                 vmf->page = NULL;
2881                 return VM_FAULT_HWPOISON;
2882         }
2883 
2884         if (unlikely(!(ret & VM_FAULT_LOCKED)))
2885                 lock_page(vmf->page);
2886         else
2887                 VM_BUG_ON_PAGE(!PageLocked(vmf->page), vmf->page);
2888 
2889         return ret;
2890 }
2891 
2892 static int pte_alloc_one_map(struct vm_fault *vmf)
2893 {
2894         struct vm_area_struct *vma = vmf->vma;
2895 
2896         if (!pmd_none(*vmf->pmd))
2897                 goto map_pte;
2898         if (vmf->prealloc_pte) {
2899                 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
2900                 if (unlikely(!pmd_none(*vmf->pmd))) {
2901                         spin_unlock(vmf->ptl);
2902                         goto map_pte;
2903                 }
2904 
2905                 atomic_long_inc(&vma->vm_mm->nr_ptes);
2906                 pmd_populate(vma->vm_mm, vmf->pmd, vmf->prealloc_pte);
2907                 spin_unlock(vmf->ptl);
2908                 vmf->prealloc_pte = 0;
2909         } else if (unlikely(pte_alloc(vma->vm_mm, vmf->pmd, vmf->address))) {
2910                 return VM_FAULT_OOM;
2911         }
2912 map_pte:
2913         /*
2914          * If a huge pmd materialized under us just retry later.  Use
2915          * pmd_trans_unstable() instead of pmd_trans_huge() to ensure the pmd
2916          * didn't become pmd_trans_huge under us and then back to pmd_none, as
2917          * a result of MADV_DONTNEED running immediately after a huge pmd fault
2918          * in a different thread of this mm, in turn leading to a misleading
2919          * pmd_trans_huge() retval.  All we have to ensure is that it is a
2920          * regular pmd that we can walk with pte_offset_map() and we can do that
2921          * through an atomic read in C, which is what pmd_trans_unstable()
2922          * provides.
2923          */
2924         if (pmd_trans_unstable(vmf->pmd) || pmd_devmap(*vmf->pmd))
2925                 return VM_FAULT_NOPAGE;
2926 
2927         vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address,
2928                         &vmf->ptl);
2929         return 0;
2930 }
2931 
2932 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
2933 
2934 #define HPAGE_CACHE_INDEX_MASK (HPAGE_PMD_NR - 1)
2935 static inline bool transhuge_vma_suitable(struct vm_area_struct *vma,
2936                 unsigned long haddr)
2937 {
2938         if (((vma->vm_start >> PAGE_SHIFT) & HPAGE_CACHE_INDEX_MASK) !=
2939                         (vma->vm_pgoff & HPAGE_CACHE_INDEX_MASK))
2940                 return false;
2941         if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
2942                 return false;
2943         return true;
2944 }
2945 
2946 static void deposit_prealloc_pte(struct vm_fault *vmf)
2947 {
2948         struct vm_area_struct *vma = vmf->vma;
2949 
2950         pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, vmf->prealloc_pte);
2951         /*
2952          * We are going to consume the prealloc table,
2953          * count that as nr_ptes.
2954          */
2955         atomic_long_inc(&vma->vm_mm->nr_ptes);
2956         vmf->prealloc_pte = 0;
2957 }
2958 
2959 static int do_set_pmd(struct vm_fault *vmf, struct page *page)
2960 {
2961         struct vm_area_struct *vma = vmf->vma;
2962         bool write = vmf->flags & FAULT_FLAG_WRITE;
2963         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
2964         pmd_t entry;
2965         int i, ret;
2966 
2967         if (!transhuge_vma_suitable(vma, haddr))
2968                 return VM_FAULT_FALLBACK;
2969 
2970         ret = VM_FAULT_FALLBACK;
2971         page = compound_head(page);
2972 
2973         /*
2974          * Archs like ppc64 need additonal space to store information
2975          * related to pte entry. Use the preallocated table for that.
2976          */
2977         if (arch_needs_pgtable_deposit() && !vmf->prealloc_pte) {
2978                 vmf->prealloc_pte = pte_alloc_one(vma->vm_mm, vmf->address);
2979                 if (!vmf->prealloc_pte)
2980                         return VM_FAULT_OOM;
2981                 smp_wmb(); /* See comment in __pte_alloc() */
2982         }
2983 
2984         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
2985         if (unlikely(!pmd_none(*vmf->pmd)))
2986                 goto out;
2987 
2988         for (i = 0; i < HPAGE_PMD_NR; i++)
2989                 flush_icache_page(vma, page + i);
2990 
2991         entry = mk_huge_pmd(page, vma->vm_page_prot);
2992         if (write)
2993                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
2994 
2995         add_mm_counter(vma->vm_mm, MM_FILEPAGES, HPAGE_PMD_NR);
2996         page_add_file_rmap(page, true);
2997         /*
2998          * deposit and withdraw with pmd lock held
2999          */
3000         if (arch_needs_pgtable_deposit())
3001                 deposit_prealloc_pte(vmf);
3002 
3003         set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
3004 
3005         update_mmu_cache_pmd(vma, haddr, vmf->pmd);
3006 
3007         /* fault is handled */
3008         ret = 0;
3009         count_vm_event(THP_FILE_MAPPED);
3010 out:
3011         spin_unlock(vmf->ptl);
3012         return ret;
3013 }
3014 #else
3015 static int do_set_pmd(struct vm_fault *vmf, struct page *page)
3016 {
3017         BUILD_BUG();
3018         return 0;
3019 }
3020 #endif
3021 
3022 /**
3023  * alloc_set_pte - setup new PTE entry for given page and add reverse page
3024  * mapping. If needed, the fucntion allocates page table or use pre-allocated.
3025  *
3026  * @vmf: fault environment
3027  * @memcg: memcg to charge page (only for private mappings)
3028  * @page: page to map
3029  *
3030  * Caller must take care of unlocking vmf->ptl, if vmf->pte is non-NULL on
3031  * return.
3032  *
3033  * Target users are page handler itself and implementations of
3034  * vm_ops->map_pages.
3035  */
3036 int alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg,
3037                 struct page *page)
3038 {
3039         struct vm_area_struct *vma = vmf->vma;
3040         bool write = vmf->flags & FAULT_FLAG_WRITE;
3041         pte_t entry;
3042         int ret;
3043 
3044         if (pmd_none(*vmf->pmd) && PageTransCompound(page) &&
3045                         IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE)) {
3046                 /* THP on COW? */
3047                 VM_BUG_ON_PAGE(memcg, page);
3048 
3049                 ret = do_set_pmd(vmf, page);
3050                 if (ret != VM_FAULT_FALLBACK)
3051                         return ret;
3052         }
3053 
3054         if (!vmf->pte) {
3055                 ret = pte_alloc_one_map(vmf);
3056                 if (ret)
3057                         return ret;
3058         }
3059 
3060         /* Re-check under ptl */
3061         if (unlikely(!pte_none(*vmf->pte)))
3062                 return VM_FAULT_NOPAGE;
3063 
3064         flush_icache_page(vma, page);
3065         entry = mk_pte(page, vma->vm_page_prot);
3066         if (write)
3067                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
3068         /* copy-on-write page */
3069         if (write && !(vma->vm_flags & VM_SHARED)) {
3070                 inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
3071                 page_add_new_anon_rmap(page, vma, vmf->address, false);
3072                 mem_cgroup_commit_charge(page, memcg, false, false);
3073                 lru_cache_add_active_or_unevictable(page, vma);
3074         } else {
3075                 inc_mm_counter_fast(vma->vm_mm, mm_counter_file(page));
3076                 page_add_file_rmap(page, false);
3077         }
3078         set_pte_at(vma->vm_mm, vmf->address, vmf->pte, entry);
3079 
3080         /* no need to invalidate: a not-present page won't be cached */
3081         update_mmu_cache(vma, vmf->address, vmf->pte);
3082 
3083         return 0;
3084 }
3085 
3086 
3087 /**
3088  * finish_fault - finish page fault once we have prepared the page to fault
3089  *
3090  * @vmf: structure describing the fault
3091  *
3092  * This function handles all that is needed to finish a page fault once the
3093  * page to fault in is prepared. It handles locking of PTEs, inserts PTE for
3094  * given page, adds reverse page mapping, handles memcg charges and LRU
3095  * addition. The function returns 0 on success, VM_FAULT_ code in case of
3096  * error.
3097  *
3098  * The function expects the page to be locked and on success it consumes a
3099  * reference of a page being mapped (for the PTE which maps it).
3100  */
3101 int finish_fault(struct vm_fault *vmf)
3102 {
3103         struct page *page;
3104         int ret;
3105 
3106         /* Did we COW the page? */
3107         if ((vmf->flags & FAULT_FLAG_WRITE) &&
3108             !(vmf->vma->vm_flags & VM_SHARED))
3109                 page = vmf->cow_page;
3110         else
3111                 page = vmf->page;
3112         ret = alloc_set_pte(vmf, vmf->memcg, page);
3113         if (vmf->pte)
3114                 pte_unmap_unlock(vmf->pte, vmf->ptl);
3115         return ret;
3116 }
3117 
3118 static unsigned long fault_around_bytes __read_mostly =
3119         rounddown_pow_of_two(65536);
3120 
3121 #ifdef CONFIG_DEBUG_FS
3122 static int fault_around_bytes_get(void *data, u64 *val)
3123 {
3124         *val = fault_around_bytes;
3125         return 0;
3126 }
3127 
3128 /*
3129  * fault_around_pages() and fault_around_mask() expects fault_around_bytes
3130  * rounded down to nearest page order. It's what do_fault_around() expects to
3131  * see.
3132  */
3133 static int fault_around_bytes_set(void *data, u64 val)
3134 {
3135         if (val / PAGE_SIZE > PTRS_PER_PTE)
3136                 return -EINVAL;
3137         if (val > PAGE_SIZE)
3138                 fault_around_bytes = rounddown_pow_of_two(val);
3139         else
3140                 fault_around_bytes = PAGE_SIZE; /* rounddown_pow_of_two(0) is undefined */
3141         return 0;
3142 }
3143 DEFINE_SIMPLE_ATTRIBUTE(fault_around_bytes_fops,
3144                 fault_around_bytes_get, fault_around_bytes_set, "%llu\n");
3145 
3146 static int __init fault_around_debugfs(void)
3147 {
3148         void *ret;
3149 
3150         ret = debugfs_create_file("fault_around_bytes", 0644, NULL, NULL,
3151                         &fault_around_bytes_fops);
3152         if (!ret)
3153                 pr_warn("Failed to create fault_around_bytes in debugfs");
3154         return 0;
3155 }
3156 late_initcall(fault_around_debugfs);
3157 #endif
3158 
3159 /*
3160  * do_fault_around() tries to map few pages around the fault address. The hope
3161  * is that the pages will be needed soon and this will lower the number of
3162  * faults to handle.
3163  *
3164  * It uses vm_ops->map_pages() to map the pages, which skips the page if it's
3165  * not ready to be mapped: not up-to-date, locked, etc.
3166  *
3167  * This function is called with the page table lock taken. In the split ptlock
3168  * case the page table lock only protects only those entries which belong to
3169  * the page table corresponding to the fault address.
3170  *
3171  * This function doesn't cross the VMA boundaries, in order to call map_pages()
3172  * only once.
3173  *
3174  * fault_around_pages() defines how many pages we'll try to map.
3175  * do_fault_around() expects it to return a power of two less than or equal to
3176  * PTRS_PER_PTE.
3177  *
3178  * The virtual address of the area that we map is naturally aligned to the
3179  * fault_around_pages() value (and therefore to page order).  This way it's
3180  * easier to guarantee that we don't cross page table boundaries.
3181  */
3182 static int do_fault_around(struct vm_fault *vmf)
3183 {
3184         unsigned long address = vmf->address, nr_pages, mask;
3185         pgoff_t start_pgoff = vmf->pgoff;
3186         pgoff_t end_pgoff;
3187         int off, ret = 0;
3188 
3189         nr_pages = READ_ONCE(fault_around_bytes) >> PAGE_SHIFT;
3190         mask = ~(nr_pages * PAGE_SIZE - 1) & PAGE_MASK;
3191 
3192         vmf->address = max(address & mask, vmf->vma->vm_start);
3193         off = ((address - vmf->address) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
3194         start_pgoff -= off;
3195 
3196         /*
3197          *  end_pgoff is either end of page table or end of vma
3198          *  or fault_around_pages() from start_pgoff, depending what is nearest.
3199          */
3200         end_pgoff = start_pgoff -
3201                 ((vmf->address >> PAGE_SHIFT) & (PTRS_PER_PTE - 1)) +
3202                 PTRS_PER_PTE - 1;
3203         end_pgoff = min3(end_pgoff, vma_pages(vmf->vma) + vmf->vma->vm_pgoff - 1,
3204                         start_pgoff + nr_pages - 1);
3205 
3206         if (pmd_none(*vmf->pmd)) {
3207                 vmf->prealloc_pte = pte_alloc_one(vmf->vma->vm_mm,
3208                                                   vmf->address);
3209                 if (!vmf->prealloc_pte)
3210                         goto out;
3211                 smp_wmb(); /* See comment in __pte_alloc() */
3212         }
3213 
3214         vmf->vma->vm_ops->map_pages(vmf, start_pgoff, end_pgoff);
3215 
3216         /* Huge page is mapped? Page fault is solved */
3217         if (pmd_trans_huge(*vmf->pmd)) {
3218                 ret = VM_FAULT_NOPAGE;
3219                 goto out;
3220         }
3221 
3222         /* ->map_pages() haven't done anything useful. Cold page cache? */
3223         if (!vmf->pte)
3224                 goto out;
3225 
3226         /* check if the page fault is solved */
3227         vmf->pte -= (vmf->address >> PAGE_SHIFT) - (address >> PAGE_SHIFT);
3228         if (!pte_none(*vmf->pte))
3229                 ret = VM_FAULT_NOPAGE;
3230         pte_unmap_unlock(vmf->pte, vmf->ptl);
3231 out:
3232         vmf->address = address;
3233         vmf->pte = NULL;
3234         return ret;
3235 }
3236 
3237 static int do_read_fault(struct vm_fault *vmf)
3238 {
3239         struct vm_area_struct *vma = vmf->vma;
3240         int ret = 0;
3241 
3242         /*
3243          * Let's call ->map_pages() first and use ->fault() as fallback
3244          * if page by the offset is not ready to be mapped (cold cache or
3245          * something).
3246          */
3247         if (vma->vm_ops->map_pages && fault_around_bytes >> PAGE_SHIFT > 1) {
3248                 ret = do_fault_around(vmf);
3249                 if (ret)
3250                         return ret;
3251         }
3252 
3253         ret = __do_fault(vmf);
3254         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
3255                 return ret;
3256 
3257         ret |= finish_fault(vmf);
3258         unlock_page(vmf->page);
3259         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
3260                 put_page(vmf->page);
3261         return ret;
3262 }
3263 
3264 static int do_cow_fault(struct vm_fault *vmf)
3265 {
3266         struct vm_area_struct *vma = vmf->vma;
3267         int ret;
3268 
3269         if (unlikely(anon_vma_prepare(vma)))
3270                 return VM_FAULT_OOM;
3271 
3272         vmf->cow_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vmf->address);
3273         if (!vmf->cow_page)
3274                 return VM_FAULT_OOM;
3275 
3276         if (mem_cgroup_try_charge(vmf->cow_page, vma->vm_mm, GFP_KERNEL,
3277                                 &vmf->memcg, false)) {
3278                 put_page(vmf->cow_page);
3279                 return VM_FAULT_OOM;
3280         }
3281 
3282         ret = __do_fault(vmf);
3283         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
3284                 goto uncharge_out;
3285         if (ret & VM_FAULT_DONE_COW)
3286                 return ret;
3287 
3288         copy_user_highpage(vmf->cow_page, vmf->page, vmf->address, vma);
3289         __SetPageUptodate(vmf->cow_page);
3290 
3291         ret |= finish_fault(vmf);
3292         unlock_page(vmf->page);
3293         put_page(vmf->page);
3294         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
3295                 goto uncharge_out;
3296         return ret;
3297 uncharge_out:
3298         mem_cgroup_cancel_charge(vmf->cow_page, vmf->memcg, false);
3299         put_page(vmf->cow_page);
3300         return ret;
3301 }
3302 
3303 static int do_shared_fault(struct vm_fault *vmf)
3304 {
3305         struct vm_area_struct *vma = vmf->vma;
3306         int ret, tmp;
3307 
3308         ret = __do_fault(vmf);
3309         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
3310                 return ret;
3311 
3312         /*
3313          * Check if the backing address space wants to know that the page is
3314          * about to become writable
3315          */
3316         if (vma->vm_ops->page_mkwrite) {
3317                 unlock_page(vmf->page);
3318                 tmp = do_page_mkwrite(vmf);
3319                 if (unlikely(!tmp ||
3320                                 (tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
3321                         put_page(vmf->page);
3322                         return tmp;
3323                 }
3324         }
3325 
3326         ret |= finish_fault(vmf);
3327         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE |
3328                                         VM_FAULT_RETRY))) {
3329                 unlock_page(vmf->page);
3330                 put_page(vmf->page);
3331                 return ret;
3332         }
3333 
3334         fault_dirty_shared_page(vma, vmf->page);
3335         return ret;
3336 }
3337 
3338 /*
3339  * We enter with non-exclusive mmap_sem (to exclude vma changes,
3340  * but allow concurrent faults).
3341  * The mmap_sem may have been released depending on flags and our
3342  * return value.  See filemap_fault() and __lock_page_or_retry().
3343  */
3344 static int do_fault(struct vm_fault *vmf)
3345 {
3346         struct vm_area_struct *vma = vmf->vma;
3347         int ret;
3348 
3349         /* The VMA was not fully populated on mmap() or missing VM_DONTEXPAND */
3350         if (!vma->vm_ops->fault)
3351                 ret = VM_FAULT_SIGBUS;
3352         else if (!(vmf->flags & FAULT_FLAG_WRITE))
3353                 ret = do_read_fault(vmf);
3354         else if (!(vma->vm_flags & VM_SHARED))
3355                 ret = do_cow_fault(vmf);
3356         else
3357                 ret = do_shared_fault(vmf);
3358 
3359         /* preallocated pagetable is unused: free it */
3360         if (vmf->prealloc_pte) {
3361                 pte_free(vma->vm_mm, vmf->prealloc_pte);
3362                 vmf->prealloc_pte = 0;
3363         }
3364         return ret;
3365 }
3366 
3367 static int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,
3368                                 unsigned long addr, int page_nid,
3369                                 int *flags)
3370 {
3371         get_page(page);
3372 
3373         count_vm_numa_event(NUMA_HINT_FAULTS);
3374         if (page_nid == numa_node_id()) {
3375                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
3376                 *flags |= TNF_FAULT_LOCAL;
3377         }
3378 
3379         return mpol_misplaced(page, vma, addr);
3380 }
3381 
3382 static int do_numa_page(struct vm_fault *vmf)
3383 {
3384         struct vm_area_struct *vma = vmf->vma;
3385         struct page *page = NULL;
3386         int page_nid = -1;
3387         int last_cpupid;
3388         int target_nid;
3389         bool migrated = false;
3390         pte_t pte = vmf->orig_pte;
3391         bool was_writable = pte_write(pte);
3392         int flags = 0;
3393 
3394         /*
3395         * The "pte" at this point cannot be used safely without
3396         * validation through pte_unmap_same(). It's of NUMA type but
3397         * the pfn may be screwed if the read is non atomic.
3398         *
3399         * We can safely just do a "set_pte_at()", because the old
3400         * page table entry is not accessible, so there would be no
3401         * concurrent hardware modifications to the PTE.
3402         */
3403         vmf->ptl = pte_lockptr(vma->vm_mm, vmf->pmd);
3404         spin_lock(vmf->ptl);
3405         if (unlikely(!pte_same(*vmf->pte, pte))) {
3406                 pte_unmap_unlock(vmf->pte, vmf->ptl);
3407                 goto out;
3408         }
3409 
3410         /* Make it present again */
3411         pte = pte_modify(pte, vma->vm_page_prot);
3412         pte = pte_mkyoung(pte);
3413         if (was_writable)
3414                 pte = pte_mkwrite(pte);
3415         set_pte_at(vma->vm_mm, vmf->address, vmf->pte, pte);
3416         update_mmu_cache(vma, vmf->address, vmf->pte);
3417 
3418         page = vm_normal_page(vma, vmf->address, pte);
3419         if (!page) {
3420                 pte_unmap_unlock(vmf->pte, vmf->ptl);
3421                 return 0;
3422         }
3423 
3424         /* TODO: handle PTE-mapped THP */
3425         if (PageCompound(page)) {
3426                 pte_unmap_unlock(vmf->pte, vmf->ptl);
3427                 return 0;
3428         }
3429 
3430         /*
3431          * Avoid grouping on RO pages in general. RO pages shouldn't hurt as
3432          * much anyway since they can be in shared cache state. This misses
3433          * the case where a mapping is writable but the process never writes
3434          * to it but pte_write gets cleared during protection updates and
3435          * pte_dirty has unpredictable behaviour between PTE scan updates,
3436          * background writeback, dirty balancing and application behaviour.
3437          */
3438         if (!pte_write(pte))
3439                 flags |= TNF_NO_GROUP;
3440 
3441         /*
3442          * Flag if the page is shared between multiple address spaces. This
3443          * is later used when determining whether to group tasks together
3444          */
3445         if (page_mapcount(page) > 1 && (vma->vm_flags & VM_SHARED))
3446                 flags |= TNF_SHARED;
3447 
3448         last_cpupid = page_cpupid_last(page);
3449         page_nid = page_to_nid(page);
3450         target_nid = numa_migrate_prep(page, vma, vmf->address, page_nid,
3451                         &flags);
3452         pte_unmap_unlock(vmf->pte, vmf->ptl);
3453         if (target_nid == -1) {
3454                 put_page(page);
3455                 goto out;
3456         }
3457 
3458         /* Migrate to the requested node */
3459         migrated = migrate_misplaced_page(page, vma, target_nid);
3460         if (migrated) {
3461                 page_nid = target_nid;
3462                 flags |= TNF_MIGRATED;
3463         } else
3464                 flags |= TNF_MIGRATE_FAIL;
3465 
3466 out:
3467         if (page_nid != -1)
3468                 task_numa_fault(last_cpupid, page_nid, 1, flags);
3469         return 0;
3470 }
3471 
3472 static int create_huge_pmd(struct vm_fault *vmf)
3473 {
3474         struct vm_area_struct *vma = vmf->vma;
3475         if (vma_is_anonymous(vma))
3476                 return do_huge_pmd_anonymous_page(vmf);
3477         if (vma->vm_ops->pmd_fault)
3478                 return vma->vm_ops->pmd_fault(vma, vmf->address, vmf->pmd,
3479                                 vmf->flags);
3480         return VM_FAULT_FALLBACK;
3481 }
3482 
3483 static int wp_huge_pmd(struct vm_fault *vmf, pmd_t orig_pmd)
3484 {
3485         if (vma_is_anonymous(vmf->vma))
3486                 return do_huge_pmd_wp_page(vmf, orig_pmd);
3487         if (vmf->vma->vm_ops->pmd_fault)
3488                 return vmf->vma->vm_ops->pmd_fault(vmf->vma, vmf->address,
3489                                                    vmf->pmd, vmf->flags);
3490 
3491         /* COW handled on pte level: split pmd */
3492         VM_BUG_ON_VMA(vmf->vma->vm_flags & VM_SHARED, vmf->vma);
3493         __split_huge_pmd(vmf->vma, vmf->pmd, vmf->address, false, NULL);
3494 
3495         return VM_FAULT_FALLBACK;
3496 }
3497 
3498 static inline bool vma_is_accessible(struct vm_area_struct *vma)
3499 {
3500         return vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE);
3501 }
3502 
3503 /*
3504  * These routines also need to handle stuff like marking pages dirty
3505  * and/or accessed for architectures that don't do it in hardware (most
3506  * RISC architectures).  The early dirtying is also good on the i386.
3507  *
3508  * There is also a hook called "update_mmu_cache()" that architectures
3509  * with external mmu caches can use to update those (ie the Sparc or
3510  * PowerPC hashed page tables that act as extended TLBs).
3511  *
3512  * We enter with non-exclusive mmap_sem (to exclude vma changes, but allow
3513  * concurrent faults).
3514  *
3515  * The mmap_sem may have been released depending on flags and our return value.
3516  * See filemap_fault() and __lock_page_or_retry().
3517  */
3518 static int handle_pte_fault(struct vm_fault *vmf)
3519 {
3520         pte_t entry;
3521 
3522         if (unlikely(pmd_none(*vmf->pmd))) {
3523                 /*
3524                  * Leave __pte_alloc() until later: because vm_ops->fault may
3525                  * want to allocate huge page, and if we expose page table
3526                  * for an instant, it will be difficult to retract from
3527                  * concurrent faults and from rmap lookups.
3528                  */
3529                 vmf->pte = NULL;
3530         } else {
3531                 /* See comment in pte_alloc_one_map() */
3532                 if (pmd_trans_unstable(vmf->pmd) || pmd_devmap(*vmf->pmd))
3533                         return 0;
3534                 /*
3535                  * A regular pmd is established and it can't morph into a huge
3536                  * pmd from under us anymore at this point because we hold the
3537                  * mmap_sem read mode and khugepaged takes it in write mode.
3538                  * So now it's safe to run pte_offset_map().
3539                  */
3540                 vmf->pte = pte_offset_map(vmf->pmd, vmf->address);
3541                 vmf->orig_pte = *vmf->pte;
3542 
3543                 /*
3544                  * some architectures can have larger ptes than wordsize,
3545                  * e.g.ppc44x-defconfig has CONFIG_PTE_64BIT=y and
3546                  * CONFIG_32BIT=y, so READ_ONCE or ACCESS_ONCE cannot guarantee
3547                  * atomic accesses.  The code below just needs a consistent
3548                  * view for the ifs and we later double check anyway with the
3549                  * ptl lock held. So here a barrier will do.
3550                  */
3551                 barrier();
3552                 if (pte_none(vmf->orig_pte)) {
3553                         pte_unmap(vmf->pte);
3554                         vmf->pte = NULL;
3555                 }
3556         }
3557 
3558         if (!vmf->pte) {
3559                 if (vma_is_anonymous(vmf->vma))
3560                         return do_anonymous_page(vmf);
3561                 else
3562                         return do_fault(vmf);
3563         }
3564 
3565         if (!pte_present(vmf->orig_pte))
3566                 return do_swap_page(vmf);
3567 
3568         if (pte_protnone(vmf->orig_pte) && vma_is_accessible(vmf->vma))
3569                 return do_numa_page(vmf);
3570 
3571         vmf->ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd);
3572         spin_lock(vmf->ptl);
3573         entry = vmf->orig_pte;
3574         if (unlikely(!pte_same(*vmf->pte, entry)))
3575                 goto unlock;
3576         if (vmf->flags & FAULT_FLAG_WRITE) {
3577                 if (!pte_write(entry))
3578                         return do_wp_page(vmf);
3579                 entry = pte_mkdirty(entry);
3580         }
3581         entry = pte_mkyoung(entry);
3582         if (ptep_set_access_flags(vmf->vma, vmf->address, vmf->pte, entry,
3583                                 vmf->flags & FAULT_FLAG_WRITE)) {
3584                 update_mmu_cache(vmf->vma, vmf->address, vmf->pte);
3585         } else {
3586                 /*
3587                  * This is needed only for protection faults but the arch code
3588                  * is not yet telling us if this is a protection fault or not.
3589                  * This still avoids useless tlb flushes for .text page faults
3590                  * with threads.
3591                  */
3592                 if (vmf->flags & FAULT_FLAG_WRITE)
3593                         flush_tlb_fix_spurious_fault(vmf->vma, vmf->address);
3594         }
3595 unlock:
3596         pte_unmap_unlock(vmf->pte, vmf->ptl);
3597         return 0;
3598 }
3599 
3600 /*
3601  * By the time we get here, we already hold the mm semaphore
3602  *
3603  * The mmap_sem may have been released depending on flags and our
3604  * return value.  See filemap_fault() and __lock_page_or_retry().
3605  */
3606 static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
3607                 unsigned int flags)
3608 {
3609         struct vm_fault vmf = {
3610                 .vma = vma,
3611                 .address = address & PAGE_MASK,
3612                 .flags = flags,
3613                 .pgoff = linear_page_index(vma, address),
3614                 .gfp_mask = __get_fault_gfp_mask(vma),
3615         };
3616         struct mm_struct *mm = vma->vm_mm;
3617         pgd_t *pgd;
3618         pud_t *pud;
3619 
3620         pgd = pgd_offset(mm, address);
3621         pud = pud_alloc(mm, pgd, address);
3622         if (!pud)
3623                 return VM_FAULT_OOM;
3624         vmf.pmd = pmd_alloc(mm, pud, address);
3625         if (!vmf.pmd)
3626                 return VM_FAULT_OOM;
3627         if (pmd_none(*vmf.pmd) && transparent_hugepage_enabled(vma)) {
3628                 int ret = create_huge_pmd(&vmf);
3629                 if (!(ret & VM_FAULT_FALLBACK))
3630                         return ret;
3631         } else {
3632                 pmd_t orig_pmd = *vmf.pmd;
3633                 int ret;
3634 
3635                 barrier();
3636                 if (pmd_trans_huge(orig_pmd) || pmd_devmap(orig_pmd)) {
3637                         if (pmd_protnone(orig_pmd) && vma_is_accessible(vma))
3638                                 return do_huge_pmd_numa_page(&vmf, orig_pmd);
3639 
3640                         if ((vmf.flags & FAULT_FLAG_WRITE) &&
3641                                         !pmd_write(orig_pmd)) {
3642                                 ret = wp_huge_pmd(&vmf, orig_pmd);
3643                                 if (!(ret & VM_FAULT_FALLBACK))
3644                                         return ret;
3645                         } else {
3646                                 huge_pmd_set_accessed(&vmf, orig_pmd);
3647                                 return 0;
3648                         }
3649                 }
3650         }
3651 
3652         return handle_pte_fault(&vmf);
3653 }
3654 
3655 /*
3656  * By the time we get here, we already hold the mm semaphore
3657  *
3658  * The mmap_sem may have been released depending on flags and our
3659  * return value.  See filemap_fault() and __lock_page_or_retry().
3660  */
3661 int handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
3662                 unsigned int flags)
3663 {
3664         int ret;
3665 
3666         __set_current_state(TASK_RUNNING);
3667 
3668         count_vm_event(PGFAULT);
3669         mem_cgroup_count_vm_event(vma->vm_mm, PGFAULT);
3670 
3671         /* do counter updates before entering really critical section. */
3672         check_sync_rss_stat(current);
3673 
3674         /*
3675          * Enable the memcg OOM handling for faults triggered in user
3676          * space.  Kernel faults are handled more gracefully.
3677          */
3678         if (flags & FAULT_FLAG_USER)
3679                 mem_cgroup_oom_enable();
3680 
3681         if (!arch_vma_access_permitted(vma, flags & FAULT_FLAG_WRITE,
3682                                             flags & FAULT_FLAG_INSTRUCTION,
3683                                             flags & FAULT_FLAG_REMOTE))
3684                 return VM_FAULT_SIGSEGV;
3685 
3686         if (unlikely(is_vm_hugetlb_page(vma)))
3687                 ret = hugetlb_fault(vma->vm_mm, vma, address, flags);
3688         else
3689                 ret = __handle_mm_fault(vma, address, flags);
3690 
3691         if (flags & FAULT_FLAG_USER) {
3692                 mem_cgroup_oom_disable();
3693                 /*
3694                  * The task may have entered a memcg OOM situation but
3695                  * if the allocation error was handled gracefully (no
3696                  * VM_FAULT_OOM), there is no need to kill anything.
3697                  * Just clean up the OOM state peacefully.
3698                  */
3699                 if (task_in_memcg_oom(current) && !(ret & VM_FAULT_OOM))
3700                         mem_cgroup_oom_synchronize(false);
3701         }
3702 
3703         /*
3704          * This mm has been already reaped by the oom reaper and so the
3705          * refault cannot be trusted in general. Anonymous refaults would
3706          * lose data and give a zero page instead e.g. This is especially
3707          * problem for use_mm() because regular tasks will just die and
3708          * the corrupted data will not be visible anywhere while kthread
3709          * will outlive the oom victim and potentially propagate the date
3710          * further.
3711          */
3712         if (unlikely((current->flags & PF_KTHREAD) && !(ret & VM_FAULT_ERROR)
3713                                 && test_bit(MMF_UNSTABLE, &vma->vm_mm->flags)))
3714                 ret = VM_FAULT_SIGBUS;
3715 
3716         return ret;
3717 }
3718 EXPORT_SYMBOL_GPL(handle_mm_fault);
3719 
3720 #ifndef __PAGETABLE_PUD_FOLDED
3721 /*
3722  * Allocate page upper directory.
3723  * We've already handled the fast-path in-line.
3724  */
3725 int __pud_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address)
3726 {
3727         pud_t *new = pud_alloc_one(mm, address);
3728         if (!new)
3729                 return -ENOMEM;
3730 
3731         smp_wmb(); /* See comment in __pte_alloc */
3732 
3733         spin_lock(&mm->page_table_lock);
3734         if (pgd_present(*pgd))          /* Another has populated it */
3735                 pud_free(mm, new);
3736         else
3737                 pgd_populate(mm, pgd, new);
3738         spin_unlock(&mm->page_table_lock);
3739         return 0;
3740 }
3741 #endif /* __PAGETABLE_PUD_FOLDED */
3742 
3743 #ifndef __PAGETABLE_PMD_FOLDED
3744 /*
3745  * Allocate page middle directory.
3746  * We've already handled the fast-path in-line.
3747  */
3748 int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address)
3749 {
3750         pmd_t *new = pmd_alloc_one(mm, address);
3751         if (!new)
3752                 return -ENOMEM;
3753 
3754         smp_wmb(); /* See comment in __pte_alloc */
3755 
3756         spin_lock(&mm->page_table_lock);
3757 #ifndef __ARCH_HAS_4LEVEL_HACK
3758         if (!pud_present(*pud)) {
3759                 mm_inc_nr_pmds(mm);
3760                 pud_populate(mm, pud, new);
3761         } else  /* Another has populated it */
3762                 pmd_free(mm, new);
3763 #else
3764         if (!pgd_present(*pud)) {
3765                 mm_inc_nr_pmds(mm);
3766                 pgd_populate(mm, pud, new);
3767         } else /* Another has populated it */
3768                 pmd_free(mm, new);
3769 #endif /* __ARCH_HAS_4LEVEL_HACK */
3770         spin_unlock(&mm->page_table_lock);
3771         return 0;
3772 }
3773 #endif /* __PAGETABLE_PMD_FOLDED */
3774 
3775 static int __follow_pte_pmd(struct mm_struct *mm, unsigned long address,
3776                 pte_t **ptepp, pmd_t **pmdpp, spinlock_t **ptlp)
3777 {
3778         pgd_t *pgd;
3779         pud_t *pud;
3780         pmd_t *pmd;
3781         pte_t *ptep;
3782 
3783         pgd = pgd_offset(mm, address);
3784         if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
3785                 goto out;
3786 
3787         pud = pud_offset(pgd, address);
3788         if (pud_none(*pud) || unlikely(pud_bad(*pud)))
3789                 goto out;
3790 
3791         pmd = pmd_offset(pud, address);
3792         VM_BUG_ON(pmd_trans_huge(*pmd));
3793 
3794         if (pmd_huge(*pmd)) {
3795                 if (!pmdpp)
3796                         goto out;
3797 
3798                 *ptlp = pmd_lock(mm, pmd);
3799                 if (pmd_huge(*pmd)) {
3800                         *pmdpp = pmd;
3801                         return 0;
3802                 }
3803                 spin_unlock(*ptlp);
3804         }
3805 
3806         if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
3807                 goto out;
3808 
3809         ptep = pte_offset_map_lock(mm, pmd, address, ptlp);
3810         if (!ptep)
3811                 goto out;
3812         if (!pte_present(*ptep))
3813                 goto unlock;
3814         *ptepp = ptep;
3815         return 0;
3816 unlock:
3817         pte_unmap_unlock(ptep, *ptlp);
3818 out:
3819         return -EINVAL;
3820 }
3821 
3822 static inline int follow_pte(struct mm_struct *mm, unsigned long address,
3823                              pte_t **ptepp, spinlock_t **ptlp)
3824 {
3825         int res;
3826 
3827         /* (void) is needed to make gcc happy */
3828         (void) __cond_lock(*ptlp,
3829                            !(res = __follow_pte_pmd(mm, address, ptepp, NULL,
3830                                            ptlp)));
3831         return res;
3832 }
3833 
3834 int follow_pte_pmd(struct mm_struct *mm, unsigned long address,
3835                              pte_t **ptepp, pmd_t **pmdpp, spinlock_t **ptlp)
3836 {
3837         int res;
3838 
3839         /* (void) is needed to make gcc happy */
3840         (void) __cond_lock(*ptlp,
3841                            !(res = __follow_pte_pmd(mm, address, ptepp, pmdpp,
3842                                            ptlp)));
3843         return res;
3844 }
3845 EXPORT_SYMBOL(follow_pte_pmd);
3846 
3847 /**
3848  * follow_pfn - look up PFN at a user virtual address
3849  * @vma: memory mapping
3850  * @address: user virtual address
3851  * @pfn: location to store found PFN
3852  *
3853  * Only IO mappings and raw PFN mappings are allowed.
3854  *
3855  * Returns zero and the pfn at @pfn on success, -ve otherwise.
3856  */
3857 int follow_pfn(struct vm_area_struct *vma, unsigned long address,
3858         unsigned long *pfn)
3859 {
3860         int ret = -EINVAL;
3861         spinlock_t *ptl;
3862         pte_t *ptep;
3863 
3864         if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
3865                 return ret;
3866 
3867         ret = follow_pte(vma->vm_mm, address, &ptep, &ptl);
3868         if (ret)
3869                 return ret;
3870         *pfn = pte_pfn(*ptep);
3871         pte_unmap_unlock(ptep, ptl);
3872         return 0;
3873 }
3874 EXPORT_SYMBOL(follow_pfn);
3875 
3876 #ifdef CONFIG_HAVE_IOREMAP_PROT
3877 int follow_phys(struct vm_area_struct *vma,
3878                 unsigned long address, unsigned int flags,
3879                 unsigned long *prot, resource_size_t *phys)
3880 {
3881         int ret = -EINVAL;
3882         pte_t *ptep, pte;
3883         spinlock_t *ptl;
3884 
3885         if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
3886                 goto out;
3887 
3888         if (follow_pte(vma->vm_mm, address, &ptep, &ptl))
3889                 goto out;
3890         pte = *ptep;
3891 
3892         if ((flags & FOLL_WRITE) && !pte_write(pte))
3893                 goto unlock;
3894 
3895         *prot = pgprot_val(pte_pgprot(pte));
3896         *phys = (resource_size_t)pte_pfn(pte) << PAGE_SHIFT;
3897 
3898         ret = 0;
3899 unlock:
3900         pte_unmap_unlock(ptep, ptl);
3901 out:
3902         return ret;
3903 }
3904 
3905 int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
3906                         void *buf, int len, int write)
3907 {
3908         resource_size_t phys_addr;
3909         unsigned long prot = 0;
3910         void __iomem *maddr;
3911         int offset = addr & (PAGE_SIZE-1);
3912 
3913         if (follow_phys(vma, addr, write, &prot, &phys_addr))
3914                 return -EINVAL;
3915 
3916         maddr = ioremap_prot(phys_addr, PAGE_ALIGN(len + offset), prot);
3917         if (write)
3918                 memcpy_toio(maddr + offset, buf, len);
3919         else
3920                 memcpy_fromio(buf, maddr + offset, len);
3921         iounmap(maddr);
3922 
3923         return len;
3924 }
3925 EXPORT_SYMBOL_GPL(generic_access_phys);
3926 #endif
3927 
3928 /*
3929  * Access another process' address space as given in mm.  If non-NULL, use the
3930  * given task for page fault accounting.
3931  */
3932 int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
3933                 unsigned long addr, void *buf, int len, unsigned int gup_flags)
3934 {
3935         struct vm_area_struct *vma;
3936         void *old_buf = buf;
3937         int write = gup_flags & FOLL_WRITE;
3938 
3939         down_read(&mm->mmap_sem);
3940         /* ignore errors, just check how much was successfully transferred */
3941         while (len) {
3942                 int bytes, ret, offset;
3943                 void *maddr;
3944                 struct page *page = NULL;
3945 
3946                 ret = get_user_pages_remote(tsk, mm, addr, 1,
3947                                 gup_flags, &page, &vma, NULL);
3948                 if (ret <= 0) {
3949 #ifndef CONFIG_HAVE_IOREMAP_PROT
3950                         break;
3951 #else
3952                         /*
3953                          * Check if this is a VM_IO | VM_PFNMAP VMA, which
3954                          * we can access using slightly different code.
3955                          */
3956                         vma = find_vma(mm, addr);
3957                         if (!vma || vma->vm_start > addr)
3958                                 break;
3959                         if (vma->vm_ops && vma->vm_ops->access)
3960                                 ret = vma->vm_ops->access(vma, addr, buf,
3961                                                           len, write);
3962                         if (ret <= 0)
3963                                 break;
3964                         bytes = ret;
3965 #endif
3966                 } else {
3967                         bytes = len;
3968                         offset = addr & (PAGE_SIZE-1);
3969                         if (bytes > PAGE_SIZE-offset)
3970                                 bytes = PAGE_SIZE-offset;
3971 
3972                         maddr = kmap(page);
3973                         if (write) {
3974                                 copy_to_user_page(vma, page, addr,
3975                                                   maddr + offset, buf, bytes);
3976                                 set_page_dirty_lock(page);
3977                         } else {
3978                                 copy_from_user_page(vma, page, addr,
3979                                                     buf, maddr + offset, bytes);
3980                         }
3981                         kunmap(page);
3982                         put_page(page);
3983                 }
3984                 len -= bytes;
3985                 buf += bytes;
3986                 addr += bytes;
3987         }
3988         up_read(&mm->mmap_sem);
3989 
3990         return buf - old_buf;
3991 }
3992 
3993 /**
3994  * access_remote_vm - access another process' address space
3995  * @mm:         the mm_struct of the target address space
3996  * @addr:       start address to access
3997  * @buf:        source or destination buffer
3998  * @len:        number of bytes to transfer
3999  * @gup_flags:  flags modifying lookup behaviour
4000  *
4001  * The caller must hold a reference on @mm.
4002  */
4003 int access_remote_vm(struct mm_struct *mm, unsigned long addr,
4004                 void *buf, int len, unsigned int gup_flags)
4005 {
4006         return __access_remote_vm(NULL, mm, addr, buf, len, gup_flags);
4007 }
4008 
4009 /*
4010  * Access another process' address space.
4011  * Source/target buffer must be kernel space,
4012  * Do not walk the page table directly, use get_user_pages
4013  */
4014 int access_process_vm(struct task_struct *tsk, unsigned long addr,
4015                 void *buf, int len, unsigned int gup_flags)
4016 {
4017         struct mm_struct *mm;
4018         int ret;
4019 
4020         mm = get_task_mm(tsk);
4021         if (!mm)
4022                 return 0;
4023 
4024         ret = __access_remote_vm(tsk, mm, addr, buf, len, gup_flags);
4025 
4026         mmput(mm);
4027 
4028         return ret;
4029 }
4030 EXPORT_SYMBOL_GPL(access_process_vm);
4031 
4032 /*
4033  * Print the name of a VMA.
4034  */
4035 void print_vma_addr(char *prefix, unsigned long ip)
4036 {
4037         struct mm_struct *mm = current->mm;
4038         struct vm_area_struct *vma;
4039 
4040         /*
4041          * Do not print if we are in atomic
4042          * contexts (in exception stacks, etc.):
4043          */
4044         if (preempt_count())
4045                 return;
4046 
4047         down_read(&mm->mmap_sem);
4048         vma = find_vma(mm, ip);
4049         if (vma && vma->vm_file) {
4050                 struct file *f = vma->vm_file;
4051                 char *buf = (char *)__get_free_page(GFP_KERNEL);
4052                 if (buf) {
4053                         char *p;
4054 
4055                         p = file_path(f, buf, PAGE_SIZE);
4056                         if (IS_ERR(p))
4057                                 p = "?";
4058                         printk("%s%s[%lx+%lx]", prefix, kbasename(p),
4059                                         vma->vm_start,
4060                                         vma->vm_end - vma->vm_start);
4061                         free_page((unsigned long)buf);
4062                 }
4063         }
4064         up_read(&mm->mmap_sem);
4065 }
4066 
4067 #if defined(CONFIG_PROVE_LOCKING) || defined(CONFIG_DEBUG_ATOMIC_SLEEP)
4068 void __might_fault(const char *file, int line)
4069 {
4070         /*
4071          * Some code (nfs/sunrpc) uses socket ops on kernel memory while
4072          * holding the mmap_sem, this is safe because kernel memory doesn't
4073          * get paged out, therefore we'll never actually fault, and the
4074          * below annotations will generate false positives.
4075          */
4076         if (segment_eq(get_fs(), KERNEL_DS))
4077                 return;
4078         if (pagefault_disabled())
4079                 return;
4080         __might_sleep(file, line, 0);
4081 #if defined(CONFIG_DEBUG_ATOMIC_SLEEP)
4082         if (current->mm)
4083                 might_lock_read(&current->mm->mmap_sem);
4084 #endif
4085 }
4086 EXPORT_SYMBOL(__might_fault);
4087 #endif
4088 
4089 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HUGETLBFS)
4090 static void clear_gigantic_page(struct page *page,
4091                                 unsigned long addr,
4092                                 unsigned int pages_per_huge_page)
4093 {
4094         int i;
4095         struct page *p = page;
4096 
4097         might_sleep();
4098         for (i = 0; i < pages_per_huge_page;
4099              i++, p = mem_map_next(p, page, i)) {
4100                 cond_resched();
4101                 clear_user_highpage(p, addr + i * PAGE_SIZE);
4102         }
4103 }
4104 void clear_huge_page(struct page *page,
4105                      unsigned long addr, unsigned int pages_per_huge_page)
4106 {
4107         int i;
4108 
4109         if (unlikely(pages_per_huge_page > MAX_ORDER_NR_PAGES)) {
4110                 clear_gigantic_page(page, addr, pages_per_huge_page);
4111                 return;
4112         }
4113 
4114         might_sleep();
4115         for (i = 0; i < pages_per_huge_page; i++) {
4116                 cond_resched();
4117                 clear_user_highpage(page + i, addr + i * PAGE_SIZE);
4118         }
4119 }
4120 
4121 static void copy_user_gigantic_page(struct page *dst, struct page *src,
4122                                     unsigned long addr,
4123                                     struct vm_area_struct *vma,
4124                                     unsigned int pages_per_huge_page)
4125 {
4126         int i;
4127         struct page *dst_base = dst;
4128         struct page *src_base = src;
4129 
4130         for (i = 0; i < pages_per_huge_page; ) {
4131                 cond_resched();
4132                 copy_user_highpage(dst, src, addr + i*PAGE_SIZE, vma);
4133 
4134                 i++;
4135                 dst = mem_map_next(dst, dst_base, i);
4136                 src = mem_map_next(src, src_base, i);
4137         }
4138 }
4139 
4140 void copy_user_huge_page(struct page *dst, struct page *src,
4141                          unsigned long addr, struct vm_area_struct *vma,
4142                          unsigned int pages_per_huge_page)
4143 {
4144         int i;
4145 
4146         if (unlikely(pages_per_huge_page > MAX_ORDER_NR_PAGES)) {
4147                 copy_user_gigantic_page(dst, src, addr, vma,
4148                                         pages_per_huge_page);
4149                 return;
4150         }
4151 
4152         might_sleep();
4153         for (i = 0; i < pages_per_huge_page; i++) {
4154                 cond_resched();
4155                 copy_user_highpage(dst + i, src + i, addr + i*PAGE_SIZE, vma);
4156         }
4157 }
4158 #endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */
4159 
4160 #if USE_SPLIT_PTE_PTLOCKS && ALLOC_SPLIT_PTLOCKS
4161 
4162 static struct kmem_cache *page_ptl_cachep;
4163 
4164 void __init ptlock_cache_init(void)
4165 {
4166         page_ptl_cachep = kmem_cache_create("page->ptl", sizeof(spinlock_t), 0,
4167                         SLAB_PANIC, NULL);
4168 }
4169 
4170 bool ptlock_alloc(struct page *page)
4171 {
4172         spinlock_t *ptl;
4173 
4174         ptl = kmem_cache_alloc(page_ptl_cachep, GFP_KERNEL);
4175         if (!ptl)
4176                 return false;
4177         page->ptl = ptl;
4178         return true;
4179 }
4180 
4181 void ptlock_free(struct page *page)
4182 {
4183         kmem_cache_free(page_ptl_cachep, page->ptl);
4184 }
4185 #endif
4186 

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