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Linux/mm/shmem.c

  1 /*
  2  * Resizable virtual memory filesystem for Linux.
  3  *
  4  * Copyright (C) 2000 Linus Torvalds.
  5  *               2000 Transmeta Corp.
  6  *               2000-2001 Christoph Rohland
  7  *               2000-2001 SAP AG
  8  *               2002 Red Hat Inc.
  9  * Copyright (C) 2002-2011 Hugh Dickins.
 10  * Copyright (C) 2011 Google Inc.
 11  * Copyright (C) 2002-2005 VERITAS Software Corporation.
 12  * Copyright (C) 2004 Andi Kleen, SuSE Labs
 13  *
 14  * Extended attribute support for tmpfs:
 15  * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
 16  * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
 17  *
 18  * tiny-shmem:
 19  * Copyright (c) 2004, 2008 Matt Mackall <mpm@selenic.com>
 20  *
 21  * This file is released under the GPL.
 22  */
 23 
 24 #include <linux/fs.h>
 25 #include <linux/init.h>
 26 #include <linux/vfs.h>
 27 #include <linux/mount.h>
 28 #include <linux/ramfs.h>
 29 #include <linux/pagemap.h>
 30 #include <linux/file.h>
 31 #include <linux/mm.h>
 32 #include <linux/export.h>
 33 #include <linux/swap.h>
 34 #include <linux/uio.h>
 35 #include <linux/khugepaged.h>
 36 
 37 static struct vfsmount *shm_mnt;
 38 
 39 #ifdef CONFIG_SHMEM
 40 /*
 41  * This virtual memory filesystem is heavily based on the ramfs. It
 42  * extends ramfs by the ability to use swap and honor resource limits
 43  * which makes it a completely usable filesystem.
 44  */
 45 
 46 #include <linux/xattr.h>
 47 #include <linux/exportfs.h>
 48 #include <linux/posix_acl.h>
 49 #include <linux/posix_acl_xattr.h>
 50 #include <linux/mman.h>
 51 #include <linux/string.h>
 52 #include <linux/slab.h>
 53 #include <linux/backing-dev.h>
 54 #include <linux/shmem_fs.h>
 55 #include <linux/writeback.h>
 56 #include <linux/blkdev.h>
 57 #include <linux/pagevec.h>
 58 #include <linux/percpu_counter.h>
 59 #include <linux/falloc.h>
 60 #include <linux/splice.h>
 61 #include <linux/security.h>
 62 #include <linux/swapops.h>
 63 #include <linux/mempolicy.h>
 64 #include <linux/namei.h>
 65 #include <linux/ctype.h>
 66 #include <linux/migrate.h>
 67 #include <linux/highmem.h>
 68 #include <linux/seq_file.h>
 69 #include <linux/magic.h>
 70 #include <linux/syscalls.h>
 71 #include <linux/fcntl.h>
 72 #include <uapi/linux/memfd.h>
 73 
 74 #include <linux/uaccess.h>
 75 #include <asm/pgtable.h>
 76 
 77 #include "internal.h"
 78 
 79 #define BLOCKS_PER_PAGE  (PAGE_SIZE/512)
 80 #define VM_ACCT(size)    (PAGE_ALIGN(size) >> PAGE_SHIFT)
 81 
 82 /* Pretend that each entry is of this size in directory's i_size */
 83 #define BOGO_DIRENT_SIZE 20
 84 
 85 /* Symlink up to this size is kmalloc'ed instead of using a swappable page */
 86 #define SHORT_SYMLINK_LEN 128
 87 
 88 /*
 89  * shmem_fallocate communicates with shmem_fault or shmem_writepage via
 90  * inode->i_private (with i_mutex making sure that it has only one user at
 91  * a time): we would prefer not to enlarge the shmem inode just for that.
 92  */
 93 struct shmem_falloc {
 94         wait_queue_head_t *waitq; /* faults into hole wait for punch to end */
 95         pgoff_t start;          /* start of range currently being fallocated */
 96         pgoff_t next;           /* the next page offset to be fallocated */
 97         pgoff_t nr_falloced;    /* how many new pages have been fallocated */
 98         pgoff_t nr_unswapped;   /* how often writepage refused to swap out */
 99 };
100 
101 #ifdef CONFIG_TMPFS
102 static unsigned long shmem_default_max_blocks(void)
103 {
104         return totalram_pages / 2;
105 }
106 
107 static unsigned long shmem_default_max_inodes(void)
108 {
109         return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
110 }
111 #endif
112 
113 static bool shmem_should_replace_page(struct page *page, gfp_t gfp);
114 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
115                                 struct shmem_inode_info *info, pgoff_t index);
116 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
117                 struct page **pagep, enum sgp_type sgp,
118                 gfp_t gfp, struct mm_struct *fault_mm, int *fault_type);
119 
120 int shmem_getpage(struct inode *inode, pgoff_t index,
121                 struct page **pagep, enum sgp_type sgp)
122 {
123         return shmem_getpage_gfp(inode, index, pagep, sgp,
124                 mapping_gfp_mask(inode->i_mapping), NULL, NULL);
125 }
126 
127 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
128 {
129         return sb->s_fs_info;
130 }
131 
132 /*
133  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
134  * for shared memory and for shared anonymous (/dev/zero) mappings
135  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
136  * consistent with the pre-accounting of private mappings ...
137  */
138 static inline int shmem_acct_size(unsigned long flags, loff_t size)
139 {
140         return (flags & VM_NORESERVE) ?
141                 0 : security_vm_enough_memory_mm(current->mm, VM_ACCT(size));
142 }
143 
144 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
145 {
146         if (!(flags & VM_NORESERVE))
147                 vm_unacct_memory(VM_ACCT(size));
148 }
149 
150 static inline int shmem_reacct_size(unsigned long flags,
151                 loff_t oldsize, loff_t newsize)
152 {
153         if (!(flags & VM_NORESERVE)) {
154                 if (VM_ACCT(newsize) > VM_ACCT(oldsize))
155                         return security_vm_enough_memory_mm(current->mm,
156                                         VM_ACCT(newsize) - VM_ACCT(oldsize));
157                 else if (VM_ACCT(newsize) < VM_ACCT(oldsize))
158                         vm_unacct_memory(VM_ACCT(oldsize) - VM_ACCT(newsize));
159         }
160         return 0;
161 }
162 
163 /*
164  * ... whereas tmpfs objects are accounted incrementally as
165  * pages are allocated, in order to allow large sparse files.
166  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
167  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
168  */
169 static inline int shmem_acct_block(unsigned long flags, long pages)
170 {
171         if (!(flags & VM_NORESERVE))
172                 return 0;
173 
174         return security_vm_enough_memory_mm(current->mm,
175                         pages * VM_ACCT(PAGE_SIZE));
176 }
177 
178 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
179 {
180         if (flags & VM_NORESERVE)
181                 vm_unacct_memory(pages * VM_ACCT(PAGE_SIZE));
182 }
183 
184 static const struct super_operations shmem_ops;
185 static const struct address_space_operations shmem_aops;
186 static const struct file_operations shmem_file_operations;
187 static const struct inode_operations shmem_inode_operations;
188 static const struct inode_operations shmem_dir_inode_operations;
189 static const struct inode_operations shmem_special_inode_operations;
190 static const struct vm_operations_struct shmem_vm_ops;
191 static struct file_system_type shmem_fs_type;
192 
193 static LIST_HEAD(shmem_swaplist);
194 static DEFINE_MUTEX(shmem_swaplist_mutex);
195 
196 static int shmem_reserve_inode(struct super_block *sb)
197 {
198         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
199         if (sbinfo->max_inodes) {
200                 spin_lock(&sbinfo->stat_lock);
201                 if (!sbinfo->free_inodes) {
202                         spin_unlock(&sbinfo->stat_lock);
203                         return -ENOSPC;
204                 }
205                 sbinfo->free_inodes--;
206                 spin_unlock(&sbinfo->stat_lock);
207         }
208         return 0;
209 }
210 
211 static void shmem_free_inode(struct super_block *sb)
212 {
213         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
214         if (sbinfo->max_inodes) {
215                 spin_lock(&sbinfo->stat_lock);
216                 sbinfo->free_inodes++;
217                 spin_unlock(&sbinfo->stat_lock);
218         }
219 }
220 
221 /**
222  * shmem_recalc_inode - recalculate the block usage of an inode
223  * @inode: inode to recalc
224  *
225  * We have to calculate the free blocks since the mm can drop
226  * undirtied hole pages behind our back.
227  *
228  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
229  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
230  *
231  * It has to be called with the spinlock held.
232  */
233 static void shmem_recalc_inode(struct inode *inode)
234 {
235         struct shmem_inode_info *info = SHMEM_I(inode);
236         long freed;
237 
238         freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
239         if (freed > 0) {
240                 struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
241                 if (sbinfo->max_blocks)
242                         percpu_counter_add(&sbinfo->used_blocks, -freed);
243                 info->alloced -= freed;
244                 inode->i_blocks -= freed * BLOCKS_PER_PAGE;
245                 shmem_unacct_blocks(info->flags, freed);
246         }
247 }
248 
249 bool shmem_charge(struct inode *inode, long pages)
250 {
251         struct shmem_inode_info *info = SHMEM_I(inode);
252         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
253         unsigned long flags;
254 
255         if (shmem_acct_block(info->flags, pages))
256                 return false;
257         spin_lock_irqsave(&info->lock, flags);
258         info->alloced += pages;
259         inode->i_blocks += pages * BLOCKS_PER_PAGE;
260         shmem_recalc_inode(inode);
261         spin_unlock_irqrestore(&info->lock, flags);
262         inode->i_mapping->nrpages += pages;
263 
264         if (!sbinfo->max_blocks)
265                 return true;
266         if (percpu_counter_compare(&sbinfo->used_blocks,
267                                 sbinfo->max_blocks - pages) > 0) {
268                 inode->i_mapping->nrpages -= pages;
269                 spin_lock_irqsave(&info->lock, flags);
270                 info->alloced -= pages;
271                 shmem_recalc_inode(inode);
272                 spin_unlock_irqrestore(&info->lock, flags);
273                 shmem_unacct_blocks(info->flags, pages);
274                 return false;
275         }
276         percpu_counter_add(&sbinfo->used_blocks, pages);
277         return true;
278 }
279 
280 void shmem_uncharge(struct inode *inode, long pages)
281 {
282         struct shmem_inode_info *info = SHMEM_I(inode);
283         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
284         unsigned long flags;
285 
286         spin_lock_irqsave(&info->lock, flags);
287         info->alloced -= pages;
288         inode->i_blocks -= pages * BLOCKS_PER_PAGE;
289         shmem_recalc_inode(inode);
290         spin_unlock_irqrestore(&info->lock, flags);
291 
292         if (sbinfo->max_blocks)
293                 percpu_counter_sub(&sbinfo->used_blocks, pages);
294         shmem_unacct_blocks(info->flags, pages);
295 }
296 
297 /*
298  * Replace item expected in radix tree by a new item, while holding tree lock.
299  */
300 static int shmem_radix_tree_replace(struct address_space *mapping,
301                         pgoff_t index, void *expected, void *replacement)
302 {
303         struct radix_tree_node *node;
304         void **pslot;
305         void *item;
306 
307         VM_BUG_ON(!expected);
308         VM_BUG_ON(!replacement);
309         item = __radix_tree_lookup(&mapping->page_tree, index, &node, &pslot);
310         if (!item)
311                 return -ENOENT;
312         if (item != expected)
313                 return -ENOENT;
314         __radix_tree_replace(&mapping->page_tree, node, pslot,
315                              replacement, NULL, NULL);
316         return 0;
317 }
318 
319 /*
320  * Sometimes, before we decide whether to proceed or to fail, we must check
321  * that an entry was not already brought back from swap by a racing thread.
322  *
323  * Checking page is not enough: by the time a SwapCache page is locked, it
324  * might be reused, and again be SwapCache, using the same swap as before.
325  */
326 static bool shmem_confirm_swap(struct address_space *mapping,
327                                pgoff_t index, swp_entry_t swap)
328 {
329         void *item;
330 
331         rcu_read_lock();
332         item = radix_tree_lookup(&mapping->page_tree, index);
333         rcu_read_unlock();
334         return item == swp_to_radix_entry(swap);
335 }
336 
337 /*
338  * Definitions for "huge tmpfs": tmpfs mounted with the huge= option
339  *
340  * SHMEM_HUGE_NEVER:
341  *      disables huge pages for the mount;
342  * SHMEM_HUGE_ALWAYS:
343  *      enables huge pages for the mount;
344  * SHMEM_HUGE_WITHIN_SIZE:
345  *      only allocate huge pages if the page will be fully within i_size,
346  *      also respect fadvise()/madvise() hints;
347  * SHMEM_HUGE_ADVISE:
348  *      only allocate huge pages if requested with fadvise()/madvise();
349  */
350 
351 #define SHMEM_HUGE_NEVER        0
352 #define SHMEM_HUGE_ALWAYS       1
353 #define SHMEM_HUGE_WITHIN_SIZE  2
354 #define SHMEM_HUGE_ADVISE       3
355 
356 /*
357  * Special values.
358  * Only can be set via /sys/kernel/mm/transparent_hugepage/shmem_enabled:
359  *
360  * SHMEM_HUGE_DENY:
361  *      disables huge on shm_mnt and all mounts, for emergency use;
362  * SHMEM_HUGE_FORCE:
363  *      enables huge on shm_mnt and all mounts, w/o needing option, for testing;
364  *
365  */
366 #define SHMEM_HUGE_DENY         (-1)
367 #define SHMEM_HUGE_FORCE        (-2)
368 
369 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
370 /* ifdef here to avoid bloating shmem.o when not necessary */
371 
372 int shmem_huge __read_mostly;
373 
374 #if defined(CONFIG_SYSFS) || defined(CONFIG_TMPFS)
375 static int shmem_parse_huge(const char *str)
376 {
377         if (!strcmp(str, "never"))
378                 return SHMEM_HUGE_NEVER;
379         if (!strcmp(str, "always"))
380                 return SHMEM_HUGE_ALWAYS;
381         if (!strcmp(str, "within_size"))
382                 return SHMEM_HUGE_WITHIN_SIZE;
383         if (!strcmp(str, "advise"))
384                 return SHMEM_HUGE_ADVISE;
385         if (!strcmp(str, "deny"))
386                 return SHMEM_HUGE_DENY;
387         if (!strcmp(str, "force"))
388                 return SHMEM_HUGE_FORCE;
389         return -EINVAL;
390 }
391 
392 static const char *shmem_format_huge(int huge)
393 {
394         switch (huge) {
395         case SHMEM_HUGE_NEVER:
396                 return "never";
397         case SHMEM_HUGE_ALWAYS:
398                 return "always";
399         case SHMEM_HUGE_WITHIN_SIZE:
400                 return "within_size";
401         case SHMEM_HUGE_ADVISE:
402                 return "advise";
403         case SHMEM_HUGE_DENY:
404                 return "deny";
405         case SHMEM_HUGE_FORCE:
406                 return "force";
407         default:
408                 VM_BUG_ON(1);
409                 return "bad_val";
410         }
411 }
412 #endif
413 
414 static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
415                 struct shrink_control *sc, unsigned long nr_to_split)
416 {
417         LIST_HEAD(list), *pos, *next;
418         LIST_HEAD(to_remove);
419         struct inode *inode;
420         struct shmem_inode_info *info;
421         struct page *page;
422         unsigned long batch = sc ? sc->nr_to_scan : 128;
423         int removed = 0, split = 0;
424 
425         if (list_empty(&sbinfo->shrinklist))
426                 return SHRINK_STOP;
427 
428         spin_lock(&sbinfo->shrinklist_lock);
429         list_for_each_safe(pos, next, &sbinfo->shrinklist) {
430                 info = list_entry(pos, struct shmem_inode_info, shrinklist);
431 
432                 /* pin the inode */
433                 inode = igrab(&info->vfs_inode);
434 
435                 /* inode is about to be evicted */
436                 if (!inode) {
437                         list_del_init(&info->shrinklist);
438                         removed++;
439                         goto next;
440                 }
441 
442                 /* Check if there's anything to gain */
443                 if (round_up(inode->i_size, PAGE_SIZE) ==
444                                 round_up(inode->i_size, HPAGE_PMD_SIZE)) {
445                         list_move(&info->shrinklist, &to_remove);
446                         removed++;
447                         goto next;
448                 }
449 
450                 list_move(&info->shrinklist, &list);
451 next:
452                 if (!--batch)
453                         break;
454         }
455         spin_unlock(&sbinfo->shrinklist_lock);
456 
457         list_for_each_safe(pos, next, &to_remove) {
458                 info = list_entry(pos, struct shmem_inode_info, shrinklist);
459                 inode = &info->vfs_inode;
460                 list_del_init(&info->shrinklist);
461                 iput(inode);
462         }
463 
464         list_for_each_safe(pos, next, &list) {
465                 int ret;
466 
467                 info = list_entry(pos, struct shmem_inode_info, shrinklist);
468                 inode = &info->vfs_inode;
469 
470                 if (nr_to_split && split >= nr_to_split) {
471                         iput(inode);
472                         continue;
473                 }
474 
475                 page = find_lock_page(inode->i_mapping,
476                                 (inode->i_size & HPAGE_PMD_MASK) >> PAGE_SHIFT);
477                 if (!page)
478                         goto drop;
479 
480                 if (!PageTransHuge(page)) {
481                         unlock_page(page);
482                         put_page(page);
483                         goto drop;
484                 }
485 
486                 ret = split_huge_page(page);
487                 unlock_page(page);
488                 put_page(page);
489 
490                 if (ret) {
491                         /* split failed: leave it on the list */
492                         iput(inode);
493                         continue;
494                 }
495 
496                 split++;
497 drop:
498                 list_del_init(&info->shrinklist);
499                 removed++;
500                 iput(inode);
501         }
502 
503         spin_lock(&sbinfo->shrinklist_lock);
504         list_splice_tail(&list, &sbinfo->shrinklist);
505         sbinfo->shrinklist_len -= removed;
506         spin_unlock(&sbinfo->shrinklist_lock);
507 
508         return split;
509 }
510 
511 static long shmem_unused_huge_scan(struct super_block *sb,
512                 struct shrink_control *sc)
513 {
514         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
515 
516         if (!READ_ONCE(sbinfo->shrinklist_len))
517                 return SHRINK_STOP;
518 
519         return shmem_unused_huge_shrink(sbinfo, sc, 0);
520 }
521 
522 static long shmem_unused_huge_count(struct super_block *sb,
523                 struct shrink_control *sc)
524 {
525         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
526         return READ_ONCE(sbinfo->shrinklist_len);
527 }
528 #else /* !CONFIG_TRANSPARENT_HUGE_PAGECACHE */
529 
530 #define shmem_huge SHMEM_HUGE_DENY
531 
532 static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
533                 struct shrink_control *sc, unsigned long nr_to_split)
534 {
535         return 0;
536 }
537 #endif /* CONFIG_TRANSPARENT_HUGE_PAGECACHE */
538 
539 /*
540  * Like add_to_page_cache_locked, but error if expected item has gone.
541  */
542 static int shmem_add_to_page_cache(struct page *page,
543                                    struct address_space *mapping,
544                                    pgoff_t index, void *expected)
545 {
546         int error, nr = hpage_nr_pages(page);
547 
548         VM_BUG_ON_PAGE(PageTail(page), page);
549         VM_BUG_ON_PAGE(index != round_down(index, nr), page);
550         VM_BUG_ON_PAGE(!PageLocked(page), page);
551         VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
552         VM_BUG_ON(expected && PageTransHuge(page));
553 
554         page_ref_add(page, nr);
555         page->mapping = mapping;
556         page->index = index;
557 
558         spin_lock_irq(&mapping->tree_lock);
559         if (PageTransHuge(page)) {
560                 void __rcu **results;
561                 pgoff_t idx;
562                 int i;
563 
564                 error = 0;
565                 if (radix_tree_gang_lookup_slot(&mapping->page_tree,
566                                         &results, &idx, index, 1) &&
567                                 idx < index + HPAGE_PMD_NR) {
568                         error = -EEXIST;
569                 }
570 
571                 if (!error) {
572                         for (i = 0; i < HPAGE_PMD_NR; i++) {
573                                 error = radix_tree_insert(&mapping->page_tree,
574                                                 index + i, page + i);
575                                 VM_BUG_ON(error);
576                         }
577                         count_vm_event(THP_FILE_ALLOC);
578                 }
579         } else if (!expected) {
580                 error = radix_tree_insert(&mapping->page_tree, index, page);
581         } else {
582                 error = shmem_radix_tree_replace(mapping, index, expected,
583                                                                  page);
584         }
585 
586         if (!error) {
587                 mapping->nrpages += nr;
588                 if (PageTransHuge(page))
589                         __inc_node_page_state(page, NR_SHMEM_THPS);
590                 __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr);
591                 __mod_node_page_state(page_pgdat(page), NR_SHMEM, nr);
592                 spin_unlock_irq(&mapping->tree_lock);
593         } else {
594                 page->mapping = NULL;
595                 spin_unlock_irq(&mapping->tree_lock);
596                 page_ref_sub(page, nr);
597         }
598         return error;
599 }
600 
601 /*
602  * Like delete_from_page_cache, but substitutes swap for page.
603  */
604 static void shmem_delete_from_page_cache(struct page *page, void *radswap)
605 {
606         struct address_space *mapping = page->mapping;
607         int error;
608 
609         VM_BUG_ON_PAGE(PageCompound(page), page);
610 
611         spin_lock_irq(&mapping->tree_lock);
612         error = shmem_radix_tree_replace(mapping, page->index, page, radswap);
613         page->mapping = NULL;
614         mapping->nrpages--;
615         __dec_node_page_state(page, NR_FILE_PAGES);
616         __dec_node_page_state(page, NR_SHMEM);
617         spin_unlock_irq(&mapping->tree_lock);
618         put_page(page);
619         BUG_ON(error);
620 }
621 
622 /*
623  * Remove swap entry from radix tree, free the swap and its page cache.
624  */
625 static int shmem_free_swap(struct address_space *mapping,
626                            pgoff_t index, void *radswap)
627 {
628         void *old;
629 
630         spin_lock_irq(&mapping->tree_lock);
631         old = radix_tree_delete_item(&mapping->page_tree, index, radswap);
632         spin_unlock_irq(&mapping->tree_lock);
633         if (old != radswap)
634                 return -ENOENT;
635         free_swap_and_cache(radix_to_swp_entry(radswap));
636         return 0;
637 }
638 
639 /*
640  * Determine (in bytes) how many of the shmem object's pages mapped by the
641  * given offsets are swapped out.
642  *
643  * This is safe to call without i_mutex or mapping->tree_lock thanks to RCU,
644  * as long as the inode doesn't go away and racy results are not a problem.
645  */
646 unsigned long shmem_partial_swap_usage(struct address_space *mapping,
647                                                 pgoff_t start, pgoff_t end)
648 {
649         struct radix_tree_iter iter;
650         void **slot;
651         struct page *page;
652         unsigned long swapped = 0;
653 
654         rcu_read_lock();
655 
656         radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
657                 if (iter.index >= end)
658                         break;
659 
660                 page = radix_tree_deref_slot(slot);
661 
662                 if (radix_tree_deref_retry(page)) {
663                         slot = radix_tree_iter_retry(&iter);
664                         continue;
665                 }
666 
667                 if (radix_tree_exceptional_entry(page))
668                         swapped++;
669 
670                 if (need_resched()) {
671                         slot = radix_tree_iter_resume(slot, &iter);
672                         cond_resched_rcu();
673                 }
674         }
675 
676         rcu_read_unlock();
677 
678         return swapped << PAGE_SHIFT;
679 }
680 
681 /*
682  * Determine (in bytes) how many of the shmem object's pages mapped by the
683  * given vma is swapped out.
684  *
685  * This is safe to call without i_mutex or mapping->tree_lock thanks to RCU,
686  * as long as the inode doesn't go away and racy results are not a problem.
687  */
688 unsigned long shmem_swap_usage(struct vm_area_struct *vma)
689 {
690         struct inode *inode = file_inode(vma->vm_file);
691         struct shmem_inode_info *info = SHMEM_I(inode);
692         struct address_space *mapping = inode->i_mapping;
693         unsigned long swapped;
694 
695         /* Be careful as we don't hold info->lock */
696         swapped = READ_ONCE(info->swapped);
697 
698         /*
699          * The easier cases are when the shmem object has nothing in swap, or
700          * the vma maps it whole. Then we can simply use the stats that we
701          * already track.
702          */
703         if (!swapped)
704                 return 0;
705 
706         if (!vma->vm_pgoff && vma->vm_end - vma->vm_start >= inode->i_size)
707                 return swapped << PAGE_SHIFT;
708 
709         /* Here comes the more involved part */
710         return shmem_partial_swap_usage(mapping,
711                         linear_page_index(vma, vma->vm_start),
712                         linear_page_index(vma, vma->vm_end));
713 }
714 
715 /*
716  * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists.
717  */
718 void shmem_unlock_mapping(struct address_space *mapping)
719 {
720         struct pagevec pvec;
721         pgoff_t indices[PAGEVEC_SIZE];
722         pgoff_t index = 0;
723 
724         pagevec_init(&pvec, 0);
725         /*
726          * Minor point, but we might as well stop if someone else SHM_LOCKs it.
727          */
728         while (!mapping_unevictable(mapping)) {
729                 /*
730                  * Avoid pagevec_lookup(): find_get_pages() returns 0 as if it
731                  * has finished, if it hits a row of PAGEVEC_SIZE swap entries.
732                  */
733                 pvec.nr = find_get_entries(mapping, index,
734                                            PAGEVEC_SIZE, pvec.pages, indices);
735                 if (!pvec.nr)
736                         break;
737                 index = indices[pvec.nr - 1] + 1;
738                 pagevec_remove_exceptionals(&pvec);
739                 check_move_unevictable_pages(pvec.pages, pvec.nr);
740                 pagevec_release(&pvec);
741                 cond_resched();
742         }
743 }
744 
745 /*
746  * Remove range of pages and swap entries from radix tree, and free them.
747  * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.
748  */
749 static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
750                                                                  bool unfalloc)
751 {
752         struct address_space *mapping = inode->i_mapping;
753         struct shmem_inode_info *info = SHMEM_I(inode);
754         pgoff_t start = (lstart + PAGE_SIZE - 1) >> PAGE_SHIFT;
755         pgoff_t end = (lend + 1) >> PAGE_SHIFT;
756         unsigned int partial_start = lstart & (PAGE_SIZE - 1);
757         unsigned int partial_end = (lend + 1) & (PAGE_SIZE - 1);
758         struct pagevec pvec;
759         pgoff_t indices[PAGEVEC_SIZE];
760         long nr_swaps_freed = 0;
761         pgoff_t index;
762         int i;
763 
764         if (lend == -1)
765                 end = -1;       /* unsigned, so actually very big */
766 
767         pagevec_init(&pvec, 0);
768         index = start;
769         while (index < end) {
770                 pvec.nr = find_get_entries(mapping, index,
771                         min(end - index, (pgoff_t)PAGEVEC_SIZE),
772                         pvec.pages, indices);
773                 if (!pvec.nr)
774                         break;
775                 for (i = 0; i < pagevec_count(&pvec); i++) {
776                         struct page *page = pvec.pages[i];
777 
778                         index = indices[i];
779                         if (index >= end)
780                                 break;
781 
782                         if (radix_tree_exceptional_entry(page)) {
783                                 if (unfalloc)
784                                         continue;
785                                 nr_swaps_freed += !shmem_free_swap(mapping,
786                                                                 index, page);
787                                 continue;
788                         }
789 
790                         VM_BUG_ON_PAGE(page_to_pgoff(page) != index, page);
791 
792                         if (!trylock_page(page))
793                                 continue;
794 
795                         if (PageTransTail(page)) {
796                                 /* Middle of THP: zero out the page */
797                                 clear_highpage(page);
798                                 unlock_page(page);
799                                 continue;
800                         } else if (PageTransHuge(page)) {
801                                 if (index == round_down(end, HPAGE_PMD_NR)) {
802                                         /*
803                                          * Range ends in the middle of THP:
804                                          * zero out the page
805                                          */
806                                         clear_highpage(page);
807                                         unlock_page(page);
808                                         continue;
809                                 }
810                                 index += HPAGE_PMD_NR - 1;
811                                 i += HPAGE_PMD_NR - 1;
812                         }
813 
814                         if (!unfalloc || !PageUptodate(page)) {
815                                 VM_BUG_ON_PAGE(PageTail(page), page);
816                                 if (page_mapping(page) == mapping) {
817                                         VM_BUG_ON_PAGE(PageWriteback(page), page);
818                                         truncate_inode_page(mapping, page);
819                                 }
820                         }
821                         unlock_page(page);
822                 }
823                 pagevec_remove_exceptionals(&pvec);
824                 pagevec_release(&pvec);
825                 cond_resched();
826                 index++;
827         }
828 
829         if (partial_start) {
830                 struct page *page = NULL;
831                 shmem_getpage(inode, start - 1, &page, SGP_READ);
832                 if (page) {
833                         unsigned int top = PAGE_SIZE;
834                         if (start > end) {
835                                 top = partial_end;
836                                 partial_end = 0;
837                         }
838                         zero_user_segment(page, partial_start, top);
839                         set_page_dirty(page);
840                         unlock_page(page);
841                         put_page(page);
842                 }
843         }
844         if (partial_end) {
845                 struct page *page = NULL;
846                 shmem_getpage(inode, end, &page, SGP_READ);
847                 if (page) {
848                         zero_user_segment(page, 0, partial_end);
849                         set_page_dirty(page);
850                         unlock_page(page);
851                         put_page(page);
852                 }
853         }
854         if (start >= end)
855                 return;
856 
857         index = start;
858         while (index < end) {
859                 cond_resched();
860 
861                 pvec.nr = find_get_entries(mapping, index,
862                                 min(end - index, (pgoff_t)PAGEVEC_SIZE),
863                                 pvec.pages, indices);
864                 if (!pvec.nr) {
865                         /* If all gone or hole-punch or unfalloc, we're done */
866                         if (index == start || end != -1)
867                                 break;
868                         /* But if truncating, restart to make sure all gone */
869                         index = start;
870                         continue;
871                 }
872                 for (i = 0; i < pagevec_count(&pvec); i++) {
873                         struct page *page = pvec.pages[i];
874 
875                         index = indices[i];
876                         if (index >= end)
877                                 break;
878 
879                         if (radix_tree_exceptional_entry(page)) {
880                                 if (unfalloc)
881                                         continue;
882                                 if (shmem_free_swap(mapping, index, page)) {
883                                         /* Swap was replaced by page: retry */
884                                         index--;
885                                         break;
886                                 }
887                                 nr_swaps_freed++;
888                                 continue;
889                         }
890 
891                         lock_page(page);
892 
893                         if (PageTransTail(page)) {
894                                 /* Middle of THP: zero out the page */
895                                 clear_highpage(page);
896                                 unlock_page(page);
897                                 /*
898                                  * Partial thp truncate due 'start' in middle
899                                  * of THP: don't need to look on these pages
900                                  * again on !pvec.nr restart.
901                                  */
902                                 if (index != round_down(end, HPAGE_PMD_NR))
903                                         start++;
904                                 continue;
905                         } else if (PageTransHuge(page)) {
906                                 if (index == round_down(end, HPAGE_PMD_NR)) {
907                                         /*
908                                          * Range ends in the middle of THP:
909                                          * zero out the page
910                                          */
911                                         clear_highpage(page);
912                                         unlock_page(page);
913                                         continue;
914                                 }
915                                 index += HPAGE_PMD_NR - 1;
916                                 i += HPAGE_PMD_NR - 1;
917                         }
918 
919                         if (!unfalloc || !PageUptodate(page)) {
920                                 VM_BUG_ON_PAGE(PageTail(page), page);
921                                 if (page_mapping(page) == mapping) {
922                                         VM_BUG_ON_PAGE(PageWriteback(page), page);
923                                         truncate_inode_page(mapping, page);
924                                 } else {
925                                         /* Page was replaced by swap: retry */
926                                         unlock_page(page);
927                                         index--;
928                                         break;
929                                 }
930                         }
931                         unlock_page(page);
932                 }
933                 pagevec_remove_exceptionals(&pvec);
934                 pagevec_release(&pvec);
935                 index++;
936         }
937 
938         spin_lock_irq(&info->lock);
939         info->swapped -= nr_swaps_freed;
940         shmem_recalc_inode(inode);
941         spin_unlock_irq(&info->lock);
942 }
943 
944 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
945 {
946         shmem_undo_range(inode, lstart, lend, false);
947         inode->i_ctime = inode->i_mtime = current_time(inode);
948 }
949 EXPORT_SYMBOL_GPL(shmem_truncate_range);
950 
951 static int shmem_getattr(struct vfsmount *mnt, struct dentry *dentry,
952                          struct kstat *stat)
953 {
954         struct inode *inode = dentry->d_inode;
955         struct shmem_inode_info *info = SHMEM_I(inode);
956 
957         if (info->alloced - info->swapped != inode->i_mapping->nrpages) {
958                 spin_lock_irq(&info->lock);
959                 shmem_recalc_inode(inode);
960                 spin_unlock_irq(&info->lock);
961         }
962         generic_fillattr(inode, stat);
963         return 0;
964 }
965 
966 static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
967 {
968         struct inode *inode = d_inode(dentry);
969         struct shmem_inode_info *info = SHMEM_I(inode);
970         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
971         int error;
972 
973         error = setattr_prepare(dentry, attr);
974         if (error)
975                 return error;
976 
977         if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
978                 loff_t oldsize = inode->i_size;
979                 loff_t newsize = attr->ia_size;
980 
981                 /* protected by i_mutex */
982                 if ((newsize < oldsize && (info->seals & F_SEAL_SHRINK)) ||
983                     (newsize > oldsize && (info->seals & F_SEAL_GROW)))
984                         return -EPERM;
985 
986                 if (newsize != oldsize) {
987                         error = shmem_reacct_size(SHMEM_I(inode)->flags,
988                                         oldsize, newsize);
989                         if (error)
990                                 return error;
991                         i_size_write(inode, newsize);
992                         inode->i_ctime = inode->i_mtime = current_time(inode);
993                 }
994                 if (newsize <= oldsize) {
995                         loff_t holebegin = round_up(newsize, PAGE_SIZE);
996                         if (oldsize > holebegin)
997                                 unmap_mapping_range(inode->i_mapping,
998                                                         holebegin, 0, 1);
999                         if (info->alloced)
1000                                 shmem_truncate_range(inode,
1001                                                         newsize, (loff_t)-1);
1002                         /* unmap again to remove racily COWed private pages */
1003                         if (oldsize > holebegin)
1004                                 unmap_mapping_range(inode->i_mapping,
1005                                                         holebegin, 0, 1);
1006 
1007                         /*
1008                          * Part of the huge page can be beyond i_size: subject
1009                          * to shrink under memory pressure.
1010                          */
1011                         if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE)) {
1012                                 spin_lock(&sbinfo->shrinklist_lock);
1013                                 if (list_empty(&info->shrinklist)) {
1014                                         list_add_tail(&info->shrinklist,
1015                                                         &sbinfo->shrinklist);
1016                                         sbinfo->shrinklist_len++;
1017                                 }
1018                                 spin_unlock(&sbinfo->shrinklist_lock);
1019                         }
1020                 }
1021         }
1022 
1023         setattr_copy(inode, attr);
1024         if (attr->ia_valid & ATTR_MODE)
1025                 error = posix_acl_chmod(inode, inode->i_mode);
1026         return error;
1027 }
1028 
1029 static void shmem_evict_inode(struct inode *inode)
1030 {
1031         struct shmem_inode_info *info = SHMEM_I(inode);
1032         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1033 
1034         if (inode->i_mapping->a_ops == &shmem_aops) {
1035                 shmem_unacct_size(info->flags, inode->i_size);
1036                 inode->i_size = 0;
1037                 shmem_truncate_range(inode, 0, (loff_t)-1);
1038                 if (!list_empty(&info->shrinklist)) {
1039                         spin_lock(&sbinfo->shrinklist_lock);
1040                         if (!list_empty(&info->shrinklist)) {
1041                                 list_del_init(&info->shrinklist);
1042                                 sbinfo->shrinklist_len--;
1043                         }
1044                         spin_unlock(&sbinfo->shrinklist_lock);
1045                 }
1046                 if (!list_empty(&info->swaplist)) {
1047                         mutex_lock(&shmem_swaplist_mutex);
1048                         list_del_init(&info->swaplist);
1049                         mutex_unlock(&shmem_swaplist_mutex);
1050                 }
1051         }
1052 
1053         simple_xattrs_free(&info->xattrs);
1054         WARN_ON(inode->i_blocks);
1055         shmem_free_inode(inode->i_sb);
1056         clear_inode(inode);
1057 }
1058 
1059 static unsigned long find_swap_entry(struct radix_tree_root *root, void *item)
1060 {
1061         struct radix_tree_iter iter;
1062         void **slot;
1063         unsigned long found = -1;
1064         unsigned int checked = 0;
1065 
1066         rcu_read_lock();
1067         radix_tree_for_each_slot(slot, root, &iter, 0) {
1068                 if (*slot == item) {
1069                         found = iter.index;
1070                         break;
1071                 }
1072                 checked++;
1073                 if ((checked % 4096) != 0)
1074                         continue;
1075                 slot = radix_tree_iter_resume(slot, &iter);
1076                 cond_resched_rcu();
1077         }
1078 
1079         rcu_read_unlock();
1080         return found;
1081 }
1082 
1083 /*
1084  * If swap found in inode, free it and move page from swapcache to filecache.
1085  */
1086 static int shmem_unuse_inode(struct shmem_inode_info *info,
1087                              swp_entry_t swap, struct page **pagep)
1088 {
1089         struct address_space *mapping = info->vfs_inode.i_mapping;
1090         void *radswap;
1091         pgoff_t index;
1092         gfp_t gfp;
1093         int error = 0;
1094 
1095         radswap = swp_to_radix_entry(swap);
1096         index = find_swap_entry(&mapping->page_tree, radswap);
1097         if (index == -1)
1098                 return -EAGAIN; /* tell shmem_unuse we found nothing */
1099 
1100         /*
1101          * Move _head_ to start search for next from here.
1102          * But be careful: shmem_evict_inode checks list_empty without taking
1103          * mutex, and there's an instant in list_move_tail when info->swaplist
1104          * would appear empty, if it were the only one on shmem_swaplist.
1105          */
1106         if (shmem_swaplist.next != &info->swaplist)
1107                 list_move_tail(&shmem_swaplist, &info->swaplist);
1108 
1109         gfp = mapping_gfp_mask(mapping);
1110         if (shmem_should_replace_page(*pagep, gfp)) {
1111                 mutex_unlock(&shmem_swaplist_mutex);
1112                 error = shmem_replace_page(pagep, gfp, info, index);
1113                 mutex_lock(&shmem_swaplist_mutex);
1114                 /*
1115                  * We needed to drop mutex to make that restrictive page
1116                  * allocation, but the inode might have been freed while we
1117                  * dropped it: although a racing shmem_evict_inode() cannot
1118                  * complete without emptying the radix_tree, our page lock
1119                  * on this swapcache page is not enough to prevent that -
1120                  * free_swap_and_cache() of our swap entry will only
1121                  * trylock_page(), removing swap from radix_tree whatever.
1122                  *
1123                  * We must not proceed to shmem_add_to_page_cache() if the
1124                  * inode has been freed, but of course we cannot rely on
1125                  * inode or mapping or info to check that.  However, we can
1126                  * safely check if our swap entry is still in use (and here
1127                  * it can't have got reused for another page): if it's still
1128                  * in use, then the inode cannot have been freed yet, and we
1129                  * can safely proceed (if it's no longer in use, that tells
1130                  * nothing about the inode, but we don't need to unuse swap).
1131                  */
1132                 if (!page_swapcount(*pagep))
1133                         error = -ENOENT;
1134         }
1135 
1136         /*
1137          * We rely on shmem_swaplist_mutex, not only to protect the swaplist,
1138          * but also to hold up shmem_evict_inode(): so inode cannot be freed
1139          * beneath us (pagelock doesn't help until the page is in pagecache).
1140          */
1141         if (!error)
1142                 error = shmem_add_to_page_cache(*pagep, mapping, index,
1143                                                 radswap);
1144         if (error != -ENOMEM) {
1145                 /*
1146                  * Truncation and eviction use free_swap_and_cache(), which
1147                  * only does trylock page: if we raced, best clean up here.
1148                  */
1149                 delete_from_swap_cache(*pagep);
1150                 set_page_dirty(*pagep);
1151                 if (!error) {
1152                         spin_lock_irq(&info->lock);
1153                         info->swapped--;
1154                         spin_unlock_irq(&info->lock);
1155                         swap_free(swap);
1156                 }
1157         }
1158         return error;
1159 }
1160 
1161 /*
1162  * Search through swapped inodes to find and replace swap by page.
1163  */
1164 int shmem_unuse(swp_entry_t swap, struct page *page)
1165 {
1166         struct list_head *this, *next;
1167         struct shmem_inode_info *info;
1168         struct mem_cgroup *memcg;
1169         int error = 0;
1170 
1171         /*
1172          * There's a faint possibility that swap page was replaced before
1173          * caller locked it: caller will come back later with the right page.
1174          */
1175         if (unlikely(!PageSwapCache(page) || page_private(page) != swap.val))
1176                 goto out;
1177 
1178         /*
1179          * Charge page using GFP_KERNEL while we can wait, before taking
1180          * the shmem_swaplist_mutex which might hold up shmem_writepage().
1181          * Charged back to the user (not to caller) when swap account is used.
1182          */
1183         error = mem_cgroup_try_charge(page, current->mm, GFP_KERNEL, &memcg,
1184                         false);
1185         if (error)
1186                 goto out;
1187         /* No radix_tree_preload: swap entry keeps a place for page in tree */
1188         error = -EAGAIN;
1189 
1190         mutex_lock(&shmem_swaplist_mutex);
1191         list_for_each_safe(this, next, &shmem_swaplist) {
1192                 info = list_entry(this, struct shmem_inode_info, swaplist);
1193                 if (info->swapped)
1194                         error = shmem_unuse_inode(info, swap, &page);
1195                 else
1196                         list_del_init(&info->swaplist);
1197                 cond_resched();
1198                 if (error != -EAGAIN)
1199                         break;
1200                 /* found nothing in this: move on to search the next */
1201         }
1202         mutex_unlock(&shmem_swaplist_mutex);
1203 
1204         if (error) {
1205                 if (error != -ENOMEM)
1206                         error = 0;
1207                 mem_cgroup_cancel_charge(page, memcg, false);
1208         } else
1209                 mem_cgroup_commit_charge(page, memcg, true, false);
1210 out:
1211         unlock_page(page);
1212         put_page(page);
1213         return error;
1214 }
1215 
1216 /*
1217  * Move the page from the page cache to the swap cache.
1218  */
1219 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
1220 {
1221         struct shmem_inode_info *info;
1222         struct address_space *mapping;
1223         struct inode *inode;
1224         swp_entry_t swap;
1225         pgoff_t index;
1226 
1227         VM_BUG_ON_PAGE(PageCompound(page), page);
1228         BUG_ON(!PageLocked(page));
1229         mapping = page->mapping;
1230         index = page->index;
1231         inode = mapping->host;
1232         info = SHMEM_I(inode);
1233         if (info->flags & VM_LOCKED)
1234                 goto redirty;
1235         if (!total_swap_pages)
1236                 goto redirty;
1237 
1238         /*
1239          * Our capabilities prevent regular writeback or sync from ever calling
1240          * shmem_writepage; but a stacking filesystem might use ->writepage of
1241          * its underlying filesystem, in which case tmpfs should write out to
1242          * swap only in response to memory pressure, and not for the writeback
1243          * threads or sync.
1244          */
1245         if (!wbc->for_reclaim) {
1246                 WARN_ON_ONCE(1);        /* Still happens? Tell us about it! */
1247                 goto redirty;
1248         }
1249 
1250         /*
1251          * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC
1252          * value into swapfile.c, the only way we can correctly account for a
1253          * fallocated page arriving here is now to initialize it and write it.
1254          *
1255          * That's okay for a page already fallocated earlier, but if we have
1256          * not yet completed the fallocation, then (a) we want to keep track
1257          * of this page in case we have to undo it, and (b) it may not be a
1258          * good idea to continue anyway, once we're pushing into swap.  So
1259          * reactivate the page, and let shmem_fallocate() quit when too many.
1260          */
1261         if (!PageUptodate(page)) {
1262                 if (inode->i_private) {
1263                         struct shmem_falloc *shmem_falloc;
1264                         spin_lock(&inode->i_lock);
1265                         shmem_falloc = inode->i_private;
1266                         if (shmem_falloc &&
1267                             !shmem_falloc->waitq &&
1268                             index >= shmem_falloc->start &&
1269                             index < shmem_falloc->next)
1270                                 shmem_falloc->nr_unswapped++;
1271                         else
1272                                 shmem_falloc = NULL;
1273                         spin_unlock(&inode->i_lock);
1274                         if (shmem_falloc)
1275                                 goto redirty;
1276                 }
1277                 clear_highpage(page);
1278                 flush_dcache_page(page);
1279                 SetPageUptodate(page);
1280         }
1281 
1282         swap = get_swap_page();
1283         if (!swap.val)
1284                 goto redirty;
1285 
1286         if (mem_cgroup_try_charge_swap(page, swap))
1287                 goto free_swap;
1288 
1289         /*
1290          * Add inode to shmem_unuse()'s list of swapped-out inodes,
1291          * if it's not already there.  Do it now before the page is
1292          * moved to swap cache, when its pagelock no longer protects
1293          * the inode from eviction.  But don't unlock the mutex until
1294          * we've incremented swapped, because shmem_unuse_inode() will
1295          * prune a !swapped inode from the swaplist under this mutex.
1296          */
1297         mutex_lock(&shmem_swaplist_mutex);
1298         if (list_empty(&info->swaplist))
1299                 list_add_tail(&info->swaplist, &shmem_swaplist);
1300 
1301         if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
1302                 spin_lock_irq(&info->lock);
1303                 shmem_recalc_inode(inode);
1304                 info->swapped++;
1305                 spin_unlock_irq(&info->lock);
1306 
1307                 swap_shmem_alloc(swap);
1308                 shmem_delete_from_page_cache(page, swp_to_radix_entry(swap));
1309 
1310                 mutex_unlock(&shmem_swaplist_mutex);
1311                 BUG_ON(page_mapped(page));
1312                 swap_writepage(page, wbc);
1313                 return 0;
1314         }
1315 
1316         mutex_unlock(&shmem_swaplist_mutex);
1317 free_swap:
1318         swapcache_free(swap);
1319 redirty:
1320         set_page_dirty(page);
1321         if (wbc->for_reclaim)
1322                 return AOP_WRITEPAGE_ACTIVATE;  /* Return with page locked */
1323         unlock_page(page);
1324         return 0;
1325 }
1326 
1327 #if defined(CONFIG_NUMA) && defined(CONFIG_TMPFS)
1328 static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1329 {
1330         char buffer[64];
1331 
1332         if (!mpol || mpol->mode == MPOL_DEFAULT)
1333                 return;         /* show nothing */
1334 
1335         mpol_to_str(buffer, sizeof(buffer), mpol);
1336 
1337         seq_printf(seq, ",mpol=%s", buffer);
1338 }
1339 
1340 static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1341 {
1342         struct mempolicy *mpol = NULL;
1343         if (sbinfo->mpol) {
1344                 spin_lock(&sbinfo->stat_lock);  /* prevent replace/use races */
1345                 mpol = sbinfo->mpol;
1346                 mpol_get(mpol);
1347                 spin_unlock(&sbinfo->stat_lock);
1348         }
1349         return mpol;
1350 }
1351 #else /* !CONFIG_NUMA || !CONFIG_TMPFS */
1352 static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1353 {
1354 }
1355 static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1356 {
1357         return NULL;
1358 }
1359 #endif /* CONFIG_NUMA && CONFIG_TMPFS */
1360 #ifndef CONFIG_NUMA
1361 #define vm_policy vm_private_data
1362 #endif
1363 
1364 static void shmem_pseudo_vma_init(struct vm_area_struct *vma,
1365                 struct shmem_inode_info *info, pgoff_t index)
1366 {
1367         /* Create a pseudo vma that just contains the policy */
1368         vma->vm_start = 0;
1369         /* Bias interleave by inode number to distribute better across nodes */
1370         vma->vm_pgoff = index + info->vfs_inode.i_ino;
1371         vma->vm_ops = NULL;
1372         vma->vm_policy = mpol_shared_policy_lookup(&info->policy, index);
1373 }
1374 
1375 static void shmem_pseudo_vma_destroy(struct vm_area_struct *vma)
1376 {
1377         /* Drop reference taken by mpol_shared_policy_lookup() */
1378         mpol_cond_put(vma->vm_policy);
1379 }
1380 
1381 static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
1382                         struct shmem_inode_info *info, pgoff_t index)
1383 {
1384         struct vm_area_struct pvma;
1385         struct page *page;
1386 
1387         shmem_pseudo_vma_init(&pvma, info, index);
1388         page = swapin_readahead(swap, gfp, &pvma, 0);
1389         shmem_pseudo_vma_destroy(&pvma);
1390 
1391         return page;
1392 }
1393 
1394 static struct page *shmem_alloc_hugepage(gfp_t gfp,
1395                 struct shmem_inode_info *info, pgoff_t index)
1396 {
1397         struct vm_area_struct pvma;
1398         struct inode *inode = &info->vfs_inode;
1399         struct address_space *mapping = inode->i_mapping;
1400         pgoff_t idx, hindex;
1401         void __rcu **results;
1402         struct page *page;
1403 
1404         if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
1405                 return NULL;
1406 
1407         hindex = round_down(index, HPAGE_PMD_NR);
1408         rcu_read_lock();
1409         if (radix_tree_gang_lookup_slot(&mapping->page_tree, &results, &idx,
1410                                 hindex, 1) && idx < hindex + HPAGE_PMD_NR) {
1411                 rcu_read_unlock();
1412                 return NULL;
1413         }
1414         rcu_read_unlock();
1415 
1416         shmem_pseudo_vma_init(&pvma, info, hindex);
1417         page = alloc_pages_vma(gfp | __GFP_COMP | __GFP_NORETRY | __GFP_NOWARN,
1418                         HPAGE_PMD_ORDER, &pvma, 0, numa_node_id(), true);
1419         shmem_pseudo_vma_destroy(&pvma);
1420         if (page)
1421                 prep_transhuge_page(page);
1422         return page;
1423 }
1424 
1425 static struct page *shmem_alloc_page(gfp_t gfp,
1426                         struct shmem_inode_info *info, pgoff_t index)
1427 {
1428         struct vm_area_struct pvma;
1429         struct page *page;
1430 
1431         shmem_pseudo_vma_init(&pvma, info, index);
1432         page = alloc_page_vma(gfp, &pvma, 0);
1433         shmem_pseudo_vma_destroy(&pvma);
1434 
1435         return page;
1436 }
1437 
1438 static struct page *shmem_alloc_and_acct_page(gfp_t gfp,
1439                 struct shmem_inode_info *info, struct shmem_sb_info *sbinfo,
1440                 pgoff_t index, bool huge)
1441 {
1442         struct page *page;
1443         int nr;
1444         int err = -ENOSPC;
1445 
1446         if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
1447                 huge = false;
1448         nr = huge ? HPAGE_PMD_NR : 1;
1449 
1450         if (shmem_acct_block(info->flags, nr))
1451                 goto failed;
1452         if (sbinfo->max_blocks) {
1453                 if (percpu_counter_compare(&sbinfo->used_blocks,
1454                                         sbinfo->max_blocks - nr) > 0)
1455                         goto unacct;
1456                 percpu_counter_add(&sbinfo->used_blocks, nr);
1457         }
1458 
1459         if (huge)
1460                 page = shmem_alloc_hugepage(gfp, info, index);
1461         else
1462                 page = shmem_alloc_page(gfp, info, index);
1463         if (page) {
1464                 __SetPageLocked(page);
1465                 __SetPageSwapBacked(page);
1466                 return page;
1467         }
1468 
1469         err = -ENOMEM;
1470         if (sbinfo->max_blocks)
1471                 percpu_counter_add(&sbinfo->used_blocks, -nr);
1472 unacct:
1473         shmem_unacct_blocks(info->flags, nr);
1474 failed:
1475         return ERR_PTR(err);
1476 }
1477 
1478 /*
1479  * When a page is moved from swapcache to shmem filecache (either by the
1480  * usual swapin of shmem_getpage_gfp(), or by the less common swapoff of
1481  * shmem_unuse_inode()), it may have been read in earlier from swap, in
1482  * ignorance of the mapping it belongs to.  If that mapping has special
1483  * constraints (like the gma500 GEM driver, which requires RAM below 4GB),
1484  * we may need to copy to a suitable page before moving to filecache.
1485  *
1486  * In a future release, this may well be extended to respect cpuset and
1487  * NUMA mempolicy, and applied also to anonymous pages in do_swap_page();
1488  * but for now it is a simple matter of zone.
1489  */
1490 static bool shmem_should_replace_page(struct page *page, gfp_t gfp)
1491 {
1492         return page_zonenum(page) > gfp_zone(gfp);
1493 }
1494 
1495 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
1496                                 struct shmem_inode_info *info, pgoff_t index)
1497 {
1498         struct page *oldpage, *newpage;
1499         struct address_space *swap_mapping;
1500         pgoff_t swap_index;
1501         int error;
1502 
1503         oldpage = *pagep;
1504         swap_index = page_private(oldpage);
1505         swap_mapping = page_mapping(oldpage);
1506 
1507         /*
1508          * We have arrived here because our zones are constrained, so don't
1509          * limit chance of success by further cpuset and node constraints.
1510          */
1511         gfp &= ~GFP_CONSTRAINT_MASK;
1512         newpage = shmem_alloc_page(gfp, info, index);
1513         if (!newpage)
1514                 return -ENOMEM;
1515 
1516         get_page(newpage);
1517         copy_highpage(newpage, oldpage);
1518         flush_dcache_page(newpage);
1519 
1520         __SetPageLocked(newpage);
1521         __SetPageSwapBacked(newpage);
1522         SetPageUptodate(newpage);
1523         set_page_private(newpage, swap_index);
1524         SetPageSwapCache(newpage);
1525 
1526         /*
1527          * Our caller will very soon move newpage out of swapcache, but it's
1528          * a nice clean interface for us to replace oldpage by newpage there.
1529          */
1530         spin_lock_irq(&swap_mapping->tree_lock);
1531         error = shmem_radix_tree_replace(swap_mapping, swap_index, oldpage,
1532                                                                    newpage);
1533         if (!error) {
1534                 __inc_node_page_state(newpage, NR_FILE_PAGES);
1535                 __dec_node_page_state(oldpage, NR_FILE_PAGES);
1536         }
1537         spin_unlock_irq(&swap_mapping->tree_lock);
1538 
1539         if (unlikely(error)) {
1540                 /*
1541                  * Is this possible?  I think not, now that our callers check
1542                  * both PageSwapCache and page_private after getting page lock;
1543                  * but be defensive.  Reverse old to newpage for clear and free.
1544                  */
1545                 oldpage = newpage;
1546         } else {
1547                 mem_cgroup_migrate(oldpage, newpage);
1548                 lru_cache_add_anon(newpage);
1549                 *pagep = newpage;
1550         }
1551 
1552         ClearPageSwapCache(oldpage);
1553         set_page_private(oldpage, 0);
1554 
1555         unlock_page(oldpage);
1556         put_page(oldpage);
1557         put_page(oldpage);
1558         return error;
1559 }
1560 
1561 /*
1562  * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
1563  *
1564  * If we allocate a new one we do not mark it dirty. That's up to the
1565  * vm. If we swap it in we mark it dirty since we also free the swap
1566  * entry since a page cannot live in both the swap and page cache.
1567  *
1568  * fault_mm and fault_type are only supplied by shmem_fault:
1569  * otherwise they are NULL.
1570  */
1571 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
1572         struct page **pagep, enum sgp_type sgp, gfp_t gfp,
1573         struct mm_struct *fault_mm, int *fault_type)
1574 {
1575         struct address_space *mapping = inode->i_mapping;
1576         struct shmem_inode_info *info = SHMEM_I(inode);
1577         struct shmem_sb_info *sbinfo;
1578         struct mm_struct *charge_mm;
1579         struct mem_cgroup *memcg;
1580         struct page *page;
1581         swp_entry_t swap;
1582         enum sgp_type sgp_huge = sgp;
1583         pgoff_t hindex = index;
1584         int error;
1585         int once = 0;
1586         int alloced = 0;
1587 
1588         if (index > (MAX_LFS_FILESIZE >> PAGE_SHIFT))
1589                 return -EFBIG;
1590         if (sgp == SGP_NOHUGE || sgp == SGP_HUGE)
1591                 sgp = SGP_CACHE;
1592 repeat:
1593         swap.val = 0;
1594         page = find_lock_entry(mapping, index);
1595         if (radix_tree_exceptional_entry(page)) {
1596                 swap = radix_to_swp_entry(page);
1597                 page = NULL;
1598         }
1599 
1600         if (sgp <= SGP_CACHE &&
1601             ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) {
1602                 error = -EINVAL;
1603                 goto unlock;
1604         }
1605 
1606         if (page && sgp == SGP_WRITE)
1607                 mark_page_accessed(page);
1608 
1609         /* fallocated page? */
1610         if (page && !PageUptodate(page)) {
1611                 if (sgp != SGP_READ)
1612                         goto clear;
1613                 unlock_page(page);
1614                 put_page(page);
1615                 page = NULL;
1616         }
1617         if (page || (sgp == SGP_READ && !swap.val)) {
1618                 *pagep = page;
1619                 return 0;
1620         }
1621 
1622         /*
1623          * Fast cache lookup did not find it:
1624          * bring it back from swap or allocate.
1625          */
1626         sbinfo = SHMEM_SB(inode->i_sb);
1627         charge_mm = fault_mm ? : current->mm;
1628 
1629         if (swap.val) {
1630                 /* Look it up and read it in.. */
1631                 page = lookup_swap_cache(swap);
1632                 if (!page) {
1633                         /* Or update major stats only when swapin succeeds?? */
1634                         if (fault_type) {
1635                                 *fault_type |= VM_FAULT_MAJOR;
1636                                 count_vm_event(PGMAJFAULT);
1637                                 mem_cgroup_count_vm_event(fault_mm, PGMAJFAULT);
1638                         }
1639                         /* Here we actually start the io */
1640                         page = shmem_swapin(swap, gfp, info, index);
1641                         if (!page) {
1642                                 error = -ENOMEM;
1643                                 goto failed;
1644                         }
1645                 }
1646 
1647                 /* We have to do this with page locked to prevent races */
1648                 lock_page(page);
1649                 if (!PageSwapCache(page) || page_private(page) != swap.val ||
1650                     !shmem_confirm_swap(mapping, index, swap)) {
1651                         error = -EEXIST;        /* try again */
1652                         goto unlock;
1653                 }
1654                 if (!PageUptodate(page)) {
1655                         error = -EIO;
1656                         goto failed;
1657                 }
1658                 wait_on_page_writeback(page);
1659 
1660                 if (shmem_should_replace_page(page, gfp)) {
1661                         error = shmem_replace_page(&page, gfp, info, index);
1662                         if (error)
1663                                 goto failed;
1664                 }
1665 
1666                 error = mem_cgroup_try_charge(page, charge_mm, gfp, &memcg,
1667                                 false);
1668                 if (!error) {
1669                         error = shmem_add_to_page_cache(page, mapping, index,
1670                                                 swp_to_radix_entry(swap));
1671                         /*
1672                          * We already confirmed swap under page lock, and make
1673                          * no memory allocation here, so usually no possibility
1674                          * of error; but free_swap_and_cache() only trylocks a
1675                          * page, so it is just possible that the entry has been
1676                          * truncated or holepunched since swap was confirmed.
1677                          * shmem_undo_range() will have done some of the
1678                          * unaccounting, now delete_from_swap_cache() will do
1679                          * the rest.
1680                          * Reset swap.val? No, leave it so "failed" goes back to
1681                          * "repeat": reading a hole and writing should succeed.
1682                          */
1683                         if (error) {
1684                                 mem_cgroup_cancel_charge(page, memcg, false);
1685                                 delete_from_swap_cache(page);
1686                         }
1687                 }
1688                 if (error)
1689                         goto failed;
1690 
1691                 mem_cgroup_commit_charge(page, memcg, true, false);
1692 
1693                 spin_lock_irq(&info->lock);
1694                 info->swapped--;
1695                 shmem_recalc_inode(inode);
1696                 spin_unlock_irq(&info->lock);
1697 
1698                 if (sgp == SGP_WRITE)
1699                         mark_page_accessed(page);
1700 
1701                 delete_from_swap_cache(page);
1702                 set_page_dirty(page);
1703                 swap_free(swap);
1704 
1705         } else {
1706                 /* shmem_symlink() */
1707                 if (mapping->a_ops != &shmem_aops)
1708                         goto alloc_nohuge;
1709                 if (shmem_huge == SHMEM_HUGE_DENY || sgp_huge == SGP_NOHUGE)
1710                         goto alloc_nohuge;
1711                 if (shmem_huge == SHMEM_HUGE_FORCE)
1712                         goto alloc_huge;
1713                 switch (sbinfo->huge) {
1714                         loff_t i_size;
1715                         pgoff_t off;
1716                 case SHMEM_HUGE_NEVER:
1717                         goto alloc_nohuge;
1718                 case SHMEM_HUGE_WITHIN_SIZE:
1719                         off = round_up(index, HPAGE_PMD_NR);
1720                         i_size = round_up(i_size_read(inode), PAGE_SIZE);
1721                         if (i_size >= HPAGE_PMD_SIZE &&
1722                                         i_size >> PAGE_SHIFT >= off)
1723                                 goto alloc_huge;
1724                         /* fallthrough */
1725                 case SHMEM_HUGE_ADVISE:
1726                         if (sgp_huge == SGP_HUGE)
1727                                 goto alloc_huge;
1728                         /* TODO: implement fadvise() hints */
1729                         goto alloc_nohuge;
1730                 }
1731 
1732 alloc_huge:
1733                 page = shmem_alloc_and_acct_page(gfp, info, sbinfo,
1734                                 index, true);
1735                 if (IS_ERR(page)) {
1736 alloc_nohuge:           page = shmem_alloc_and_acct_page(gfp, info, sbinfo,
1737                                         index, false);
1738                 }
1739                 if (IS_ERR(page)) {
1740                         int retry = 5;
1741                         error = PTR_ERR(page);
1742                         page = NULL;
1743                         if (error != -ENOSPC)
1744                                 goto failed;
1745                         /*
1746                          * Try to reclaim some spece by splitting a huge page
1747                          * beyond i_size on the filesystem.
1748                          */
1749                         while (retry--) {
1750                                 int ret;
1751                                 ret = shmem_unused_huge_shrink(sbinfo, NULL, 1);
1752                                 if (ret == SHRINK_STOP)
1753                                         break;
1754                                 if (ret)
1755                                         goto alloc_nohuge;
1756                         }
1757                         goto failed;
1758                 }
1759 
1760                 if (PageTransHuge(page))
1761                         hindex = round_down(index, HPAGE_PMD_NR);
1762                 else
1763                         hindex = index;
1764 
1765                 if (sgp == SGP_WRITE)
1766                         __SetPageReferenced(page);
1767 
1768                 error = mem_cgroup_try_charge(page, charge_mm, gfp, &memcg,
1769                                 PageTransHuge(page));
1770                 if (error)
1771                         goto unacct;
1772                 error = radix_tree_maybe_preload_order(gfp & GFP_RECLAIM_MASK,
1773                                 compound_order(page));
1774                 if (!error) {
1775                         error = shmem_add_to_page_cache(page, mapping, hindex,
1776                                                         NULL);
1777                         radix_tree_preload_end();
1778                 }
1779                 if (error) {
1780                         mem_cgroup_cancel_charge(page, memcg,
1781                                         PageTransHuge(page));
1782                         goto unacct;
1783                 }
1784                 mem_cgroup_commit_charge(page, memcg, false,
1785                                 PageTransHuge(page));
1786                 lru_cache_add_anon(page);
1787 
1788                 spin_lock_irq(&info->lock);
1789                 info->alloced += 1 << compound_order(page);
1790                 inode->i_blocks += BLOCKS_PER_PAGE << compound_order(page);
1791                 shmem_recalc_inode(inode);
1792                 spin_unlock_irq(&info->lock);
1793                 alloced = true;
1794 
1795                 if (PageTransHuge(page) &&
1796                                 DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE) <
1797                                 hindex + HPAGE_PMD_NR - 1) {
1798                         /*
1799                          * Part of the huge page is beyond i_size: subject
1800                          * to shrink under memory pressure.
1801                          */
1802                         spin_lock(&sbinfo->shrinklist_lock);
1803                         if (list_empty(&info->shrinklist)) {
1804                                 list_add_tail(&info->shrinklist,
1805                                                 &sbinfo->shrinklist);
1806                                 sbinfo->shrinklist_len++;
1807                         }
1808                         spin_unlock(&sbinfo->shrinklist_lock);
1809                 }
1810 
1811                 /*
1812                  * Let SGP_FALLOC use the SGP_WRITE optimization on a new page.
1813                  */
1814                 if (sgp == SGP_FALLOC)
1815                         sgp = SGP_WRITE;
1816 clear:
1817                 /*
1818                  * Let SGP_WRITE caller clear ends if write does not fill page;
1819                  * but SGP_FALLOC on a page fallocated earlier must initialize
1820                  * it now, lest undo on failure cancel our earlier guarantee.
1821                  */
1822                 if (sgp != SGP_WRITE && !PageUptodate(page)) {
1823                         struct page *head = compound_head(page);
1824                         int i;
1825 
1826                         for (i = 0; i < (1 << compound_order(head)); i++) {
1827                                 clear_highpage(head + i);
1828                                 flush_dcache_page(head + i);
1829                         }
1830                         SetPageUptodate(head);
1831                 }
1832         }
1833 
1834         /* Perhaps the file has been truncated since we checked */
1835         if (sgp <= SGP_CACHE &&
1836             ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) {
1837                 if (alloced) {
1838                         ClearPageDirty(page);
1839                         delete_from_page_cache(page);
1840                         spin_lock_irq(&info->lock);
1841                         shmem_recalc_inode(inode);
1842                         spin_unlock_irq(&info->lock);
1843                 }
1844                 error = -EINVAL;
1845                 goto unlock;
1846         }
1847         *pagep = page + index - hindex;
1848         return 0;
1849 
1850         /*
1851          * Error recovery.
1852          */
1853 unacct:
1854         if (sbinfo->max_blocks)
1855                 percpu_counter_sub(&sbinfo->used_blocks,
1856                                 1 << compound_order(page));
1857         shmem_unacct_blocks(info->flags, 1 << compound_order(page));
1858 
1859         if (PageTransHuge(page)) {
1860                 unlock_page(page);
1861                 put_page(page);
1862                 goto alloc_nohuge;
1863         }
1864 failed:
1865         if (swap.val && !shmem_confirm_swap(mapping, index, swap))
1866                 error = -EEXIST;
1867 unlock:
1868         if (page) {
1869                 unlock_page(page);
1870                 put_page(page);
1871         }
1872         if (error == -ENOSPC && !once++) {
1873                 spin_lock_irq(&info->lock);
1874                 shmem_recalc_inode(inode);
1875                 spin_unlock_irq(&info->lock);
1876                 goto repeat;
1877         }
1878         if (error == -EEXIST)   /* from above or from radix_tree_insert */
1879                 goto repeat;
1880         return error;
1881 }
1882 
1883 /*
1884  * This is like autoremove_wake_function, but it removes the wait queue
1885  * entry unconditionally - even if something else had already woken the
1886  * target.
1887  */
1888 static int synchronous_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key)
1889 {
1890         int ret = default_wake_function(wait, mode, sync, key);
1891         list_del_init(&wait->task_list);
1892         return ret;
1893 }
1894 
1895 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1896 {
1897         struct inode *inode = file_inode(vma->vm_file);
1898         gfp_t gfp = mapping_gfp_mask(inode->i_mapping);
1899         enum sgp_type sgp;
1900         int error;
1901         int ret = VM_FAULT_LOCKED;
1902 
1903         /*
1904          * Trinity finds that probing a hole which tmpfs is punching can
1905          * prevent the hole-punch from ever completing: which in turn
1906          * locks writers out with its hold on i_mutex.  So refrain from
1907          * faulting pages into the hole while it's being punched.  Although
1908          * shmem_undo_range() does remove the additions, it may be unable to
1909          * keep up, as each new page needs its own unmap_mapping_range() call,
1910          * and the i_mmap tree grows ever slower to scan if new vmas are added.
1911          *
1912          * It does not matter if we sometimes reach this check just before the
1913          * hole-punch begins, so that one fault then races with the punch:
1914          * we just need to make racing faults a rare case.
1915          *
1916          * The implementation below would be much simpler if we just used a
1917          * standard mutex or completion: but we cannot take i_mutex in fault,
1918          * and bloating every shmem inode for this unlikely case would be sad.
1919          */
1920         if (unlikely(inode->i_private)) {
1921                 struct shmem_falloc *shmem_falloc;
1922 
1923                 spin_lock(&inode->i_lock);
1924                 shmem_falloc = inode->i_private;
1925                 if (shmem_falloc &&
1926                     shmem_falloc->waitq &&
1927                     vmf->pgoff >= shmem_falloc->start &&
1928                     vmf->pgoff < shmem_falloc->next) {
1929                         wait_queue_head_t *shmem_falloc_waitq;
1930                         DEFINE_WAIT_FUNC(shmem_fault_wait, synchronous_wake_function);
1931 
1932                         ret = VM_FAULT_NOPAGE;
1933                         if ((vmf->flags & FAULT_FLAG_ALLOW_RETRY) &&
1934                            !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT)) {
1935                                 /* It's polite to up mmap_sem if we can */
1936                                 up_read(&vma->vm_mm->mmap_sem);
1937                                 ret = VM_FAULT_RETRY;
1938                         }
1939 
1940                         shmem_falloc_waitq = shmem_falloc->waitq;
1941                         prepare_to_wait(shmem_falloc_waitq, &shmem_fault_wait,
1942                                         TASK_UNINTERRUPTIBLE);
1943                         spin_unlock(&inode->i_lock);
1944                         schedule();
1945 
1946                         /*
1947                          * shmem_falloc_waitq points into the shmem_fallocate()
1948                          * stack of the hole-punching task: shmem_falloc_waitq
1949                          * is usually invalid by the time we reach here, but
1950                          * finish_wait() does not dereference it in that case;
1951                          * though i_lock needed lest racing with wake_up_all().
1952                          */
1953                         spin_lock(&inode->i_lock);
1954                         finish_wait(shmem_falloc_waitq, &shmem_fault_wait);
1955                         spin_unlock(&inode->i_lock);
1956                         return ret;
1957                 }
1958                 spin_unlock(&inode->i_lock);
1959         }
1960 
1961         sgp = SGP_CACHE;
1962         if (vma->vm_flags & VM_HUGEPAGE)
1963                 sgp = SGP_HUGE;
1964         else if (vma->vm_flags & VM_NOHUGEPAGE)
1965                 sgp = SGP_NOHUGE;
1966 
1967         error = shmem_getpage_gfp(inode, vmf->pgoff, &vmf->page, sgp,
1968                                   gfp, vma->vm_mm, &ret);
1969         if (error)
1970                 return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1971         return ret;
1972 }
1973 
1974 unsigned long shmem_get_unmapped_area(struct file *file,
1975                                       unsigned long uaddr, unsigned long len,
1976                                       unsigned long pgoff, unsigned long flags)
1977 {
1978         unsigned long (*get_area)(struct file *,
1979                 unsigned long, unsigned long, unsigned long, unsigned long);
1980         unsigned long addr;
1981         unsigned long offset;
1982         unsigned long inflated_len;
1983         unsigned long inflated_addr;
1984         unsigned long inflated_offset;
1985 
1986         if (len > TASK_SIZE)
1987                 return -ENOMEM;
1988 
1989         get_area = current->mm->get_unmapped_area;
1990         addr = get_area(file, uaddr, len, pgoff, flags);
1991 
1992         if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
1993                 return addr;
1994         if (IS_ERR_VALUE(addr))
1995                 return addr;
1996         if (addr & ~PAGE_MASK)
1997                 return addr;
1998         if (addr > TASK_SIZE - len)
1999                 return addr;
2000 
2001         if (shmem_huge == SHMEM_HUGE_DENY)
2002                 return addr;
2003         if (len < HPAGE_PMD_SIZE)
2004                 return addr;
2005         if (flags & MAP_FIXED)
2006                 return addr;
2007         /*
2008          * Our priority is to support MAP_SHARED mapped hugely;
2009          * and support MAP_PRIVATE mapped hugely too, until it is COWed.
2010          * But if caller specified an address hint, respect that as before.
2011          */
2012         if (uaddr)
2013                 return addr;
2014 
2015         if (shmem_huge != SHMEM_HUGE_FORCE) {
2016                 struct super_block *sb;
2017 
2018                 if (file) {
2019                         VM_BUG_ON(file->f_op != &shmem_file_operations);
2020                         sb = file_inode(file)->i_sb;
2021                 } else {
2022                         /*
2023                          * Called directly from mm/mmap.c, or drivers/char/mem.c
2024                          * for "/dev/zero", to create a shared anonymous object.
2025                          */
2026                         if (IS_ERR(shm_mnt))
2027                                 return addr;
2028                         sb = shm_mnt->mnt_sb;
2029                 }
2030                 if (SHMEM_SB(sb)->huge == SHMEM_HUGE_NEVER)
2031                         return addr;
2032         }
2033 
2034         offset = (pgoff << PAGE_SHIFT) & (HPAGE_PMD_SIZE-1);
2035         if (offset && offset + len < 2 * HPAGE_PMD_SIZE)
2036                 return addr;
2037         if ((addr & (HPAGE_PMD_SIZE-1)) == offset)
2038                 return addr;
2039 
2040         inflated_len = len + HPAGE_PMD_SIZE - PAGE_SIZE;
2041         if (inflated_len > TASK_SIZE)
2042                 return addr;
2043         if (inflated_len < len)
2044                 return addr;
2045 
2046         inflated_addr = get_area(NULL, 0, inflated_len, 0, flags);
2047         if (IS_ERR_VALUE(inflated_addr))
2048                 return addr;
2049         if (inflated_addr & ~PAGE_MASK)
2050                 return addr;
2051 
2052         inflated_offset = inflated_addr & (HPAGE_PMD_SIZE-1);
2053         inflated_addr += offset - inflated_offset;
2054         if (inflated_offset > offset)
2055                 inflated_addr += HPAGE_PMD_SIZE;
2056 
2057         if (inflated_addr > TASK_SIZE - len)
2058                 return addr;
2059         return inflated_addr;
2060 }
2061 
2062 #ifdef CONFIG_NUMA
2063 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol)
2064 {
2065         struct inode *inode = file_inode(vma->vm_file);
2066         return mpol_set_shared_policy(&SHMEM_I(inode)->policy, vma, mpol);
2067 }
2068 
2069 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
2070                                           unsigned long addr)
2071 {
2072         struct inode *inode = file_inode(vma->vm_file);
2073         pgoff_t index;
2074 
2075         index = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
2076         return mpol_shared_policy_lookup(&SHMEM_I(inode)->policy, index);
2077 }
2078 #endif
2079 
2080 int shmem_lock(struct file *file, int lock, struct user_struct *user)
2081 {
2082         struct inode *inode = file_inode(file);
2083         struct shmem_inode_info *info = SHMEM_I(inode);
2084         int retval = -ENOMEM;
2085 
2086         spin_lock_irq(&info->lock);
2087         if (lock && !(info->flags & VM_LOCKED)) {
2088                 if (!user_shm_lock(inode->i_size, user))
2089                         goto out_nomem;
2090                 info->flags |= VM_LOCKED;
2091                 mapping_set_unevictable(file->f_mapping);
2092         }
2093         if (!lock && (info->flags & VM_LOCKED) && user) {
2094                 user_shm_unlock(inode->i_size, user);
2095                 info->flags &= ~VM_LOCKED;
2096                 mapping_clear_unevictable(file->f_mapping);
2097         }
2098         retval = 0;
2099 
2100 out_nomem:
2101         spin_unlock_irq(&info->lock);
2102         return retval;
2103 }
2104 
2105 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
2106 {
2107         file_accessed(file);
2108         vma->vm_ops = &shmem_vm_ops;
2109         if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE) &&
2110                         ((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) <
2111                         (vma->vm_end & HPAGE_PMD_MASK)) {
2112                 khugepaged_enter(vma, vma->vm_flags);
2113         }
2114         return 0;
2115 }
2116 
2117 static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
2118                                      umode_t mode, dev_t dev, unsigned long flags)
2119 {
2120         struct inode *inode;
2121         struct shmem_inode_info *info;
2122         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2123 
2124         if (shmem_reserve_inode(sb))
2125                 return NULL;
2126 
2127         inode = new_inode(sb);
2128         if (inode) {
2129                 inode->i_ino = get_next_ino();
2130                 inode_init_owner(inode, dir, mode);
2131                 inode->i_blocks = 0;
2132                 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
2133                 inode->i_generation = get_seconds();
2134                 info = SHMEM_I(inode);
2135                 memset(info, 0, (char *)inode - (char *)info);
2136                 spin_lock_init(&info->lock);
2137                 info->seals = F_SEAL_SEAL;
2138                 info->flags = flags & VM_NORESERVE;
2139                 INIT_LIST_HEAD(&info->shrinklist);
2140                 INIT_LIST_HEAD(&info->swaplist);
2141                 simple_xattrs_init(&info->xattrs);
2142                 cache_no_acl(inode);
2143 
2144                 switch (mode & S_IFMT) {
2145                 default:
2146                         inode->i_op = &shmem_special_inode_operations;
2147                         init_special_inode(inode, mode, dev);
2148                         break;
2149                 case S_IFREG:
2150                         inode->i_mapping->a_ops = &shmem_aops;
2151                         inode->i_op = &shmem_inode_operations;
2152                         inode->i_fop = &shmem_file_operations;
2153                         mpol_shared_policy_init(&info->policy,
2154                                                  shmem_get_sbmpol(sbinfo));
2155                         break;
2156                 case S_IFDIR:
2157                         inc_nlink(inode);
2158                         /* Some things misbehave if size == 0 on a directory */
2159                         inode->i_size = 2 * BOGO_DIRENT_SIZE;
2160                         inode->i_op = &shmem_dir_inode_operations;
2161                         inode->i_fop = &simple_dir_operations;
2162                         break;
2163                 case S_IFLNK:
2164                         /*
2165                          * Must not load anything in the rbtree,
2166                          * mpol_free_shared_policy will not be called.
2167                          */
2168                         mpol_shared_policy_init(&info->policy, NULL);
2169                         break;
2170                 }
2171         } else
2172                 shmem_free_inode(sb);
2173         return inode;
2174 }
2175 
2176 bool shmem_mapping(struct address_space *mapping)
2177 {
2178         if (!mapping->host)
2179                 return false;
2180 
2181         return mapping->host->i_sb->s_op == &shmem_ops;
2182 }
2183 
2184 #ifdef CONFIG_TMPFS
2185 static const struct inode_operations shmem_symlink_inode_operations;
2186 static const struct inode_operations shmem_short_symlink_operations;
2187 
2188 #ifdef CONFIG_TMPFS_XATTR
2189 static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
2190 #else
2191 #define shmem_initxattrs NULL
2192 #endif
2193 
2194 static int
2195 shmem_write_begin(struct file *file, struct address_space *mapping,
2196                         loff_t pos, unsigned len, unsigned flags,
2197                         struct page **pagep, void **fsdata)
2198 {
2199         struct inode *inode = mapping->host;
2200         struct shmem_inode_info *info = SHMEM_I(inode);
2201         pgoff_t index = pos >> PAGE_SHIFT;
2202 
2203         /* i_mutex is held by caller */
2204         if (unlikely(info->seals)) {
2205                 if (info->seals & F_SEAL_WRITE)
2206                         return -EPERM;
2207                 if ((info->seals & F_SEAL_GROW) && pos + len > inode->i_size)
2208                         return -EPERM;
2209         }
2210 
2211         return shmem_getpage(inode, index, pagep, SGP_WRITE);
2212 }
2213 
2214 static int
2215 shmem_write_end(struct file *file, struct address_space *mapping,
2216                         loff_t pos, unsigned len, unsigned copied,
2217                         struct page *page, void *fsdata)
2218 {
2219         struct inode *inode = mapping->host;
2220 
2221         if (pos + copied > inode->i_size)
2222                 i_size_write(inode, pos + copied);
2223 
2224         if (!PageUptodate(page)) {
2225                 struct page *head = compound_head(page);
2226                 if (PageTransCompound(page)) {
2227                         int i;
2228 
2229                         for (i = 0; i < HPAGE_PMD_NR; i++) {
2230                                 if (head + i == page)
2231                                         continue;
2232                                 clear_highpage(head + i);
2233                                 flush_dcache_page(head + i);
2234                         }
2235                 }
2236                 if (copied < PAGE_SIZE) {
2237                         unsigned from = pos & (PAGE_SIZE - 1);
2238                         zero_user_segments(page, 0, from,
2239                                         from + copied, PAGE_SIZE);
2240                 }
2241                 SetPageUptodate(head);
2242         }
2243         set_page_dirty(page);
2244         unlock_page(page);
2245         put_page(page);
2246 
2247         return copied;
2248 }
2249 
2250 static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
2251 {
2252         struct file *file = iocb->ki_filp;
2253         struct inode *inode = file_inode(file);
2254         struct address_space *mapping = inode->i_mapping;
2255         pgoff_t index;
2256         unsigned long offset;
2257         enum sgp_type sgp = SGP_READ;
2258         int error = 0;
2259         ssize_t retval = 0;
2260         loff_t *ppos = &iocb->ki_pos;
2261 
2262         /*
2263          * Might this read be for a stacking filesystem?  Then when reading
2264          * holes of a sparse file, we actually need to allocate those pages,
2265          * and even mark them dirty, so it cannot exceed the max_blocks limit.
2266          */
2267         if (!iter_is_iovec(to))
2268                 sgp = SGP_CACHE;
2269 
2270         index = *ppos >> PAGE_SHIFT;
2271         offset = *ppos & ~PAGE_MASK;
2272 
2273         for (;;) {
2274                 struct page *page = NULL;
2275                 pgoff_t end_index;
2276                 unsigned long nr, ret;
2277                 loff_t i_size = i_size_read(inode);
2278 
2279                 end_index = i_size >> PAGE_SHIFT;
2280                 if (index > end_index)
2281                         break;
2282                 if (index == end_index) {
2283                         nr = i_size & ~PAGE_MASK;
2284                         if (nr <= offset)
2285                                 break;
2286                 }
2287 
2288                 error = shmem_getpage(inode, index, &page, sgp);
2289                 if (error) {
2290                         if (error == -EINVAL)
2291                                 error = 0;
2292                         break;
2293                 }
2294                 if (page) {
2295                         if (sgp == SGP_CACHE)
2296                                 set_page_dirty(page);
2297                         unlock_page(page);
2298                 }
2299 
2300                 /*
2301                  * We must evaluate after, since reads (unlike writes)
2302                  * are called without i_mutex protection against truncate
2303                  */
2304                 nr = PAGE_SIZE;
2305                 i_size = i_size_read(inode);
2306                 end_index = i_size >> PAGE_SHIFT;
2307                 if (index == end_index) {
2308                         nr = i_size & ~PAGE_MASK;
2309                         if (nr <= offset) {
2310                                 if (page)
2311                                         put_page(page);
2312                                 break;
2313                         }
2314                 }
2315                 nr -= offset;
2316 
2317                 if (page) {
2318                         /*
2319                          * If users can be writing to this page using arbitrary
2320                          * virtual addresses, take care about potential aliasing
2321                          * before reading the page on the kernel side.
2322                          */
2323                         if (mapping_writably_mapped(mapping))
2324                                 flush_dcache_page(page);
2325                         /*
2326                          * Mark the page accessed if we read the beginning.
2327                          */
2328                         if (!offset)
2329                                 mark_page_accessed(page);
2330                 } else {
2331                         page = ZERO_PAGE(0);
2332                         get_page(page);
2333                 }
2334 
2335                 /*
2336                  * Ok, we have the page, and it's up-to-date, so
2337                  * now we can copy it to user space...
2338                  */
2339                 ret = copy_page_to_iter(page, offset, nr, to);
2340                 retval += ret;
2341                 offset += ret;
2342                 index += offset >> PAGE_SHIFT;
2343                 offset &= ~PAGE_MASK;
2344 
2345                 put_page(page);
2346                 if (!iov_iter_count(to))
2347                         break;
2348                 if (ret < nr) {
2349                         error = -EFAULT;
2350                         break;
2351                 }
2352                 cond_resched();
2353         }
2354 
2355         *ppos = ((loff_t) index << PAGE_SHIFT) + offset;
2356         file_accessed(file);
2357         return retval ? retval : error;
2358 }
2359 
2360 /*
2361  * llseek SEEK_DATA or SEEK_HOLE through the radix_tree.
2362  */
2363 static pgoff_t shmem_seek_hole_data(struct address_space *mapping,
2364                                     pgoff_t index, pgoff_t end, int whence)
2365 {
2366         struct page *page;
2367         struct pagevec pvec;
2368         pgoff_t indices[PAGEVEC_SIZE];
2369         bool done = false;
2370         int i;
2371 
2372         pagevec_init(&pvec, 0);
2373         pvec.nr = 1;            /* start small: we may be there already */
2374         while (!done) {
2375                 pvec.nr = find_get_entries(mapping, index,
2376                                         pvec.nr, pvec.pages, indices);
2377                 if (!pvec.nr) {
2378                         if (whence == SEEK_DATA)
2379                                 index = end;
2380                         break;
2381                 }
2382                 for (i = 0; i < pvec.nr; i++, index++) {
2383                         if (index < indices[i]) {
2384                                 if (whence == SEEK_HOLE) {
2385                                         done = true;
2386                                         break;
2387                                 }
2388                                 index = indices[i];
2389                         }
2390                         page = pvec.pages[i];
2391                         if (page && !radix_tree_exceptional_entry(page)) {
2392                                 if (!PageUptodate(page))
2393                                         page = NULL;
2394                         }
2395                         if (index >= end ||
2396                             (page && whence == SEEK_DATA) ||
2397                             (!page && whence == SEEK_HOLE)) {
2398                                 done = true;
2399                                 break;
2400                         }
2401                 }
2402                 pagevec_remove_exceptionals(&pvec);
2403                 pagevec_release(&pvec);
2404                 pvec.nr = PAGEVEC_SIZE;
2405                 cond_resched();
2406         }
2407         return index;
2408 }
2409 
2410 static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence)
2411 {
2412         struct address_space *mapping = file->f_mapping;
2413         struct inode *inode = mapping->host;
2414         pgoff_t start, end;
2415         loff_t new_offset;
2416 
2417         if (whence != SEEK_DATA && whence != SEEK_HOLE)
2418                 return generic_file_llseek_size(file, offset, whence,
2419                                         MAX_LFS_FILESIZE, i_size_read(inode));
2420         inode_lock(inode);
2421         /* We're holding i_mutex so we can access i_size directly */
2422 
2423         if (offset < 0)
2424                 offset = -EINVAL;
2425         else if (offset >= inode->i_size)
2426                 offset = -ENXIO;
2427         else {
2428                 start = offset >> PAGE_SHIFT;
2429                 end = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
2430                 new_offset = shmem_seek_hole_data(mapping, start, end, whence);
2431                 new_offset <<= PAGE_SHIFT;
2432                 if (new_offset > offset) {
2433                         if (new_offset < inode->i_size)
2434                                 offset = new_offset;
2435                         else if (whence == SEEK_DATA)
2436                                 offset = -ENXIO;
2437                         else
2438                                 offset = inode->i_size;
2439                 }
2440         }
2441 
2442         if (offset >= 0)
2443                 offset = vfs_setpos(file, offset, MAX_LFS_FILESIZE);
2444         inode_unlock(inode);
2445         return offset;
2446 }
2447 
2448 /*
2449  * We need a tag: a new tag would expand every radix_tree_node by 8 bytes,
2450  * so reuse a tag which we firmly believe is never set or cleared on shmem.
2451  */
2452 #define SHMEM_TAG_PINNED        PAGECACHE_TAG_TOWRITE
2453 #define LAST_SCAN               4       /* about 150ms max */
2454 
2455 static void shmem_tag_pins(struct address_space *mapping)
2456 {
2457         struct radix_tree_iter iter;
2458         void **slot;
2459         pgoff_t start;
2460         struct page *page;
2461 
2462         lru_add_drain();
2463         start = 0;
2464         rcu_read_lock();
2465 
2466         radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
2467                 page = radix_tree_deref_slot(slot);
2468                 if (!page || radix_tree_exception(page)) {
2469                         if (radix_tree_deref_retry(page)) {
2470                                 slot = radix_tree_iter_retry(&iter);
2471                                 continue;
2472                         }
2473                 } else if (page_count(page) - page_mapcount(page) > 1) {
2474                         spin_lock_irq(&mapping->tree_lock);
2475                         radix_tree_tag_set(&mapping->page_tree, iter.index,
2476                                            SHMEM_TAG_PINNED);
2477                         spin_unlock_irq(&mapping->tree_lock);
2478                 }
2479 
2480                 if (need_resched()) {
2481                         slot = radix_tree_iter_resume(slot, &iter);
2482                         cond_resched_rcu();
2483                 }
2484         }
2485         rcu_read_unlock();
2486 }
2487 
2488 /*
2489  * Setting SEAL_WRITE requires us to verify there's no pending writer. However,
2490  * via get_user_pages(), drivers might have some pending I/O without any active
2491  * user-space mappings (eg., direct-IO, AIO). Therefore, we look at all pages
2492  * and see whether it has an elevated ref-count. If so, we tag them and wait for
2493  * them to be dropped.
2494  * The caller must guarantee that no new user will acquire writable references
2495  * to those pages to avoid races.
2496  */
2497 static int shmem_wait_for_pins(struct address_space *mapping)
2498 {
2499         struct radix_tree_iter iter;
2500         void **slot;
2501         pgoff_t start;
2502         struct page *page;
2503         int error, scan;
2504 
2505         shmem_tag_pins(mapping);
2506 
2507         error = 0;
2508         for (scan = 0; scan <= LAST_SCAN; scan++) {
2509                 if (!radix_tree_tagged(&mapping->page_tree, SHMEM_TAG_PINNED))
2510                         break;
2511 
2512                 if (!scan)
2513                         lru_add_drain_all();
2514                 else if (schedule_timeout_killable((HZ << scan) / 200))
2515                         scan = LAST_SCAN;
2516 
2517                 start = 0;
2518                 rcu_read_lock();
2519                 radix_tree_for_each_tagged(slot, &mapping->page_tree, &iter,
2520                                            start, SHMEM_TAG_PINNED) {
2521 
2522                         page = radix_tree_deref_slot(slot);
2523                         if (radix_tree_exception(page)) {
2524                                 if (radix_tree_deref_retry(page)) {
2525                                         slot = radix_tree_iter_retry(&iter);
2526                                         continue;
2527                                 }
2528 
2529                                 page = NULL;
2530                         }
2531 
2532                         if (page &&
2533                             page_count(page) - page_mapcount(page) != 1) {
2534                                 if (scan < LAST_SCAN)
2535                                         goto continue_resched;
2536 
2537                                 /*
2538                                  * On the last scan, we clean up all those tags
2539                                  * we inserted; but make a note that we still
2540                                  * found pages pinned.
2541                                  */
2542                                 error = -EBUSY;
2543                         }
2544 
2545                         spin_lock_irq(&mapping->tree_lock);
2546                         radix_tree_tag_clear(&mapping->page_tree,
2547                                              iter.index, SHMEM_TAG_PINNED);
2548                         spin_unlock_irq(&mapping->tree_lock);
2549 continue_resched:
2550                         if (need_resched()) {
2551                                 slot = radix_tree_iter_resume(slot, &iter);
2552                                 cond_resched_rcu();
2553                         }
2554                 }
2555                 rcu_read_unlock();
2556         }
2557 
2558         return error;
2559 }
2560 
2561 #define F_ALL_SEALS (F_SEAL_SEAL | \
2562                      F_SEAL_SHRINK | \
2563                      F_SEAL_GROW | \
2564                      F_SEAL_WRITE)
2565 
2566 int shmem_add_seals(struct file *file, unsigned int seals)
2567 {
2568         struct inode *inode = file_inode(file);
2569         struct shmem_inode_info *info = SHMEM_I(inode);
2570         int error;
2571 
2572         /*
2573          * SEALING
2574          * Sealing allows multiple parties to share a shmem-file but restrict
2575          * access to a specific subset of file operations. Seals can only be
2576          * added, but never removed. This way, mutually untrusted parties can
2577          * share common memory regions with a well-defined policy. A malicious
2578          * peer can thus never perform unwanted operations on a shared object.
2579          *
2580          * Seals are only supported on special shmem-files and always affect
2581          * the whole underlying inode. Once a seal is set, it may prevent some
2582          * kinds of access to the file. Currently, the following seals are
2583          * defined:
2584          *   SEAL_SEAL: Prevent further seals from being set on this file
2585          *   SEAL_SHRINK: Prevent the file from shrinking
2586          *   SEAL_GROW: Prevent the file from growing
2587          *   SEAL_WRITE: Prevent write access to the file
2588          *
2589          * As we don't require any trust relationship between two parties, we
2590          * must prevent seals from being removed. Therefore, sealing a file
2591          * only adds a given set of seals to the file, it never touches
2592          * existing seals. Furthermore, the "setting seals"-operation can be
2593          * sealed itself, which basically prevents any further seal from being
2594          * added.
2595          *
2596          * Semantics of sealing are only defined on volatile files. Only
2597          * anonymous shmem files support sealing. More importantly, seals are
2598          * never written to disk. Therefore, there's no plan to support it on
2599          * other file types.
2600          */
2601 
2602         if (file->f_op != &shmem_file_operations)
2603                 return -EINVAL;
2604         if (!(file->f_mode & FMODE_WRITE))
2605                 return -EPERM;
2606         if (seals & ~(unsigned int)F_ALL_SEALS)
2607                 return -EINVAL;
2608 
2609         inode_lock(inode);
2610 
2611         if (info->seals & F_SEAL_SEAL) {
2612                 error = -EPERM;
2613                 goto unlock;
2614         }
2615 
2616         if ((seals & F_SEAL_WRITE) && !(info->seals & F_SEAL_WRITE)) {
2617                 error = mapping_deny_writable(file->f_mapping);
2618                 if (error)
2619                         goto unlock;
2620 
2621                 error = shmem_wait_for_pins(file->f_mapping);
2622                 if (error) {
2623                         mapping_allow_writable(file->f_mapping);
2624                         goto unlock;
2625                 }
2626         }
2627 
2628         info->seals |= seals;
2629         error = 0;
2630 
2631 unlock:
2632         inode_unlock(inode);
2633         return error;
2634 }
2635 EXPORT_SYMBOL_GPL(shmem_add_seals);
2636 
2637 int shmem_get_seals(struct file *file)
2638 {
2639         if (file->f_op != &shmem_file_operations)
2640                 return -EINVAL;
2641 
2642         return SHMEM_I(file_inode(file))->seals;
2643 }
2644 EXPORT_SYMBOL_GPL(shmem_get_seals);
2645 
2646 long shmem_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
2647 {
2648         long error;
2649 
2650         switch (cmd) {
2651         case F_ADD_SEALS:
2652                 /* disallow upper 32bit */
2653                 if (arg > UINT_MAX)
2654                         return -EINVAL;
2655 
2656                 error = shmem_add_seals(file, arg);
2657                 break;
2658         case F_GET_SEALS:
2659                 error = shmem_get_seals(file);
2660                 break;
2661         default:
2662                 error = -EINVAL;
2663                 break;
2664         }
2665 
2666         return error;
2667 }
2668 
2669 static long shmem_fallocate(struct file *file, int mode, loff_t offset,
2670                                                          loff_t len)
2671 {
2672         struct inode *inode = file_inode(file);
2673         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
2674         struct shmem_inode_info *info = SHMEM_I(inode);
2675         struct shmem_falloc shmem_falloc;
2676         pgoff_t start, index, end;
2677         int error;
2678 
2679         if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
2680                 return -EOPNOTSUPP;
2681 
2682         inode_lock(inode);
2683 
2684         if (mode & FALLOC_FL_PUNCH_HOLE) {
2685                 struct address_space *mapping = file->f_mapping;
2686                 loff_t unmap_start = round_up(offset, PAGE_SIZE);
2687                 loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1;
2688                 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(shmem_falloc_waitq);
2689 
2690                 /* protected by i_mutex */
2691                 if (info->seals & F_SEAL_WRITE) {
2692                         error = -EPERM;
2693                         goto out;
2694                 }
2695 
2696                 shmem_falloc.waitq = &shmem_falloc_waitq;
2697                 shmem_falloc.start = unmap_start >> PAGE_SHIFT;
2698                 shmem_falloc.next = (unmap_end + 1) >> PAGE_SHIFT;
2699                 spin_lock(&inode->i_lock);
2700                 inode->i_private = &shmem_falloc;
2701                 spin_unlock(&inode->i_lock);
2702 
2703                 if ((u64)unmap_end > (u64)unmap_start)
2704                         unmap_mapping_range(mapping, unmap_start,
2705                                             1 + unmap_end - unmap_start, 0);
2706                 shmem_truncate_range(inode, offset, offset + len - 1);
2707                 /* No need to unmap again: hole-punching leaves COWed pages */
2708 
2709                 spin_lock(&inode->i_lock);
2710                 inode->i_private = NULL;
2711                 wake_up_all(&shmem_falloc_waitq);
2712                 WARN_ON_ONCE(!list_empty(&shmem_falloc_waitq.task_list));
2713                 spin_unlock(&inode->i_lock);
2714                 error = 0;
2715                 goto out;
2716         }
2717 
2718         /* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */
2719         error = inode_newsize_ok(inode, offset + len);
2720         if (error)
2721                 goto out;
2722 
2723         if ((info->seals & F_SEAL_GROW) && offset + len > inode->i_size) {
2724                 error = -EPERM;
2725                 goto out;
2726         }
2727 
2728         start = offset >> PAGE_SHIFT;
2729         end = (offset + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
2730         /* Try to avoid a swapstorm if len is impossible to satisfy */
2731         if (sbinfo->max_blocks && end - start > sbinfo->max_blocks) {
2732                 error = -ENOSPC;
2733                 goto out;
2734         }
2735 
2736         shmem_falloc.waitq = NULL;
2737         shmem_falloc.start = start;
2738         shmem_falloc.next  = start;
2739         shmem_falloc.nr_falloced = 0;
2740         shmem_falloc.nr_unswapped = 0;
2741         spin_lock(&inode->i_lock);
2742         inode->i_private = &shmem_falloc;
2743         spin_unlock(&inode->i_lock);
2744 
2745         for (index = start; index < end; index++) {
2746                 struct page *page;
2747 
2748                 /*
2749                  * Good, the fallocate(2) manpage permits EINTR: we may have
2750                  * been interrupted because we are using up too much memory.
2751                  */
2752                 if (signal_pending(current))
2753                         error = -EINTR;
2754                 else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
2755                         error = -ENOMEM;
2756                 else
2757                         error = shmem_getpage(inode, index, &page, SGP_FALLOC);
2758                 if (error) {
2759                         /* Remove the !PageUptodate pages we added */
2760                         if (index > start) {
2761                                 shmem_undo_range(inode,
2762                                     (loff_t)start << PAGE_SHIFT,
2763                                     ((loff_t)index << PAGE_SHIFT) - 1, true);
2764                         }
2765                         goto undone;
2766                 }
2767 
2768                 /*
2769                  * Inform shmem_writepage() how far we have reached.
2770                  * No need for lock or barrier: we have the page lock.
2771                  */
2772                 shmem_falloc.next++;
2773                 if (!PageUptodate(page))
2774                         shmem_falloc.nr_falloced++;
2775 
2776                 /*
2777                  * If !PageUptodate, leave it that way so that freeable pages
2778                  * can be recognized if we need to rollback on error later.
2779                  * But set_page_dirty so that memory pressure will swap rather
2780                  * than free the pages we are allocating (and SGP_CACHE pages
2781                  * might still be clean: we now need to mark those dirty too).
2782                  */
2783                 set_page_dirty(page);
2784                 unlock_page(page);
2785                 put_page(page);
2786                 cond_resched();
2787         }
2788 
2789         if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
2790                 i_size_write(inode, offset + len);
2791         inode->i_ctime = current_time(inode);
2792 undone:
2793         spin_lock(&inode->i_lock);
2794         inode->i_private = NULL;
2795         spin_unlock(&inode->i_lock);
2796 out:
2797         inode_unlock(inode);
2798         return error;
2799 }
2800 
2801 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
2802 {
2803         struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
2804 
2805         buf->f_type = TMPFS_MAGIC;
2806         buf->f_bsize = PAGE_SIZE;
2807         buf->f_namelen = NAME_MAX;
2808         if (sbinfo->max_blocks) {
2809                 buf->f_blocks = sbinfo->max_blocks;
2810                 buf->f_bavail =
2811                 buf->f_bfree  = sbinfo->max_blocks -
2812                                 percpu_counter_sum(&sbinfo->used_blocks);
2813         }
2814         if (sbinfo->max_inodes) {
2815                 buf->f_files = sbinfo->max_inodes;
2816                 buf->f_ffree = sbinfo->free_inodes;
2817         }
2818         /* else leave those fields 0 like simple_statfs */
2819         return 0;
2820 }
2821 
2822 /*
2823  * File creation. Allocate an inode, and we're done..
2824  */
2825 static int
2826 shmem_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
2827 {
2828         struct inode *inode;
2829         int error = -ENOSPC;
2830 
2831         inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
2832         if (inode) {
2833                 error = simple_acl_create(dir, inode);
2834                 if (error)
2835                         goto out_iput;
2836                 error = security_inode_init_security(inode, dir,
2837                                                      &dentry->d_name,
2838                                                      shmem_initxattrs, NULL);
2839                 if (error && error != -EOPNOTSUPP)
2840                         goto out_iput;
2841 
2842                 error = 0;
2843                 dir->i_size += BOGO_DIRENT_SIZE;
2844                 dir->i_ctime = dir->i_mtime = current_time(dir);
2845                 d_instantiate(dentry, inode);
2846                 dget(dentry); /* Extra count - pin the dentry in core */
2847         }
2848         return error;
2849 out_iput:
2850         iput(inode);
2851         return error;
2852 }
2853 
2854 static int
2855 shmem_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
2856 {
2857         struct inode *inode;
2858         int error = -ENOSPC;
2859 
2860         inode = shmem_get_inode(dir->i_sb, dir, mode, 0, VM_NORESERVE);
2861         if (inode) {
2862                 error = security_inode_init_security(inode, dir,
2863                                                      NULL,
2864                                                      shmem_initxattrs, NULL);
2865                 if (error && error != -EOPNOTSUPP)
2866                         goto out_iput;
2867                 error = simple_acl_create(dir, inode);
2868                 if (error)
2869                         goto out_iput;
2870                 d_tmpfile(dentry, inode);
2871         }
2872         return error;
2873 out_iput:
2874         iput(inode);
2875         return error;
2876 }
2877 
2878 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
2879 {
2880         int error;
2881 
2882         if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
2883                 return error;
2884         inc_nlink(dir);
2885         return 0;
2886 }
2887 
2888 static int shmem_create(struct inode *dir, struct dentry *dentry, umode_t mode,
2889                 bool excl)
2890 {
2891         return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
2892 }
2893 
2894 /*
2895  * Link a file..
2896  */
2897 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
2898 {
2899         struct inode *inode = d_inode(old_dentry);
2900         int ret;
2901 
2902         /*
2903          * No ordinary (disk based) filesystem counts links as inodes;
2904          * but each new link needs a new dentry, pinning lowmem, and
2905          * tmpfs dentries cannot be pruned until they are unlinked.
2906          */
2907         ret = shmem_reserve_inode(inode->i_sb);
2908         if (ret)
2909                 goto out;
2910 
2911         dir->i_size += BOGO_DIRENT_SIZE;
2912         inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
2913         inc_nlink(inode);
2914         ihold(inode);   /* New dentry reference */
2915         dget(dentry);           /* Extra pinning count for the created dentry */
2916         d_instantiate(dentry, inode);
2917 out:
2918         return ret;
2919 }
2920 
2921 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
2922 {
2923         struct inode *inode = d_inode(dentry);
2924 
2925         if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
2926                 shmem_free_inode(inode->i_sb);
2927 
2928         dir->i_size -= BOGO_DIRENT_SIZE;
2929         inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
2930         drop_nlink(inode);
2931         dput(dentry);   /* Undo the count from "create" - this does all the work */
2932         return 0;
2933 }
2934 
2935 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
2936 {
2937         if (!simple_empty(dentry))
2938                 return -ENOTEMPTY;
2939 
2940         drop_nlink(d_inode(dentry));
2941         drop_nlink(dir);
2942         return shmem_unlink(dir, dentry);
2943 }
2944 
2945 static int shmem_exchange(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
2946 {
2947         bool old_is_dir = d_is_dir(old_dentry);
2948         bool new_is_dir = d_is_dir(new_dentry);
2949 
2950         if (old_dir != new_dir && old_is_dir != new_is_dir) {
2951                 if (old_is_dir) {
2952                         drop_nlink(old_dir);
2953                         inc_nlink(new_dir);
2954                 } else {
2955                         drop_nlink(new_dir);
2956                         inc_nlink(old_dir);
2957                 }
2958         }
2959         old_dir->i_ctime = old_dir->i_mtime =
2960         new_dir->i_ctime = new_dir->i_mtime =
2961         d_inode(old_dentry)->i_ctime =
2962         d_inode(new_dentry)->i_ctime = current_time(old_dir);
2963 
2964         return 0;
2965 }
2966 
2967 static int shmem_whiteout(struct inode *old_dir, struct dentry *old_dentry)
2968 {
2969         struct dentry *whiteout;
2970         int error;
2971 
2972         whiteout = d_alloc(old_dentry->d_parent, &old_dentry->d_name);
2973         if (!whiteout)
2974                 return -ENOMEM;
2975 
2976         error = shmem_mknod(old_dir, whiteout,
2977                             S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
2978         dput(whiteout);
2979         if (error)
2980                 return error;
2981 
2982         /*
2983          * Cheat and hash the whiteout while the old dentry is still in
2984          * place, instead of playing games with FS_RENAME_DOES_D_MOVE.
2985          *
2986          * d_lookup() will consistently find one of them at this point,
2987          * not sure which one, but that isn't even important.
2988          */
2989         d_rehash(whiteout);
2990         return 0;
2991 }
2992 
2993 /*
2994  * The VFS layer already does all the dentry stuff for rename,
2995  * we just have to decrement the usage count for the target if
2996  * it exists so that the VFS layer correctly free's it when it
2997  * gets overwritten.
2998  */
2999 static int shmem_rename2(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry, unsigned int flags)
3000 {
3001         struct inode *inode = d_inode(old_dentry);
3002         int they_are_dirs = S_ISDIR(inode->i_mode);
3003 
3004         if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
3005                 return -EINVAL;
3006 
3007         if (flags & RENAME_EXCHANGE)
3008                 return shmem_exchange(old_dir, old_dentry, new_dir, new_dentry);
3009 
3010         if (!simple_empty(new_dentry))
3011                 return -ENOTEMPTY;
3012 
3013         if (flags & RENAME_WHITEOUT) {
3014                 int error;
3015 
3016                 error = shmem_whiteout(old_dir, old_dentry);
3017                 if (error)
3018                         return error;
3019         }
3020 
3021         if (d_really_is_positive(new_dentry)) {
3022                 (void) shmem_unlink(new_dir, new_dentry);
3023                 if (they_are_dirs) {
3024                         drop_nlink(d_inode(new_dentry));
3025                         drop_nlink(old_dir);
3026                 }
3027         } else if (they_are_dirs) {
3028                 drop_nlink(old_dir);
3029                 inc_nlink(new_dir);
3030         }
3031 
3032         old_dir->i_size -= BOGO_DIRENT_SIZE;
3033         new_dir->i_size += BOGO_DIRENT_SIZE;
3034         old_dir->i_ctime = old_dir->i_mtime =
3035         new_dir->i_ctime = new_dir->i_mtime =
3036         inode->i_ctime = current_time(old_dir);
3037         return 0;
3038 }
3039 
3040 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
3041 {
3042         int error;
3043         int len;
3044         struct inode *inode;
3045         struct page *page;
3046         struct shmem_inode_info *info;
3047 
3048         len = strlen(symname) + 1;
3049         if (len > PAGE_SIZE)
3050                 return -ENAMETOOLONG;
3051 
3052         inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE);
3053         if (!inode)
3054                 return -ENOSPC;
3055 
3056         error = security_inode_init_security(inode, dir, &dentry->d_name,
3057                                              shmem_initxattrs, NULL);
3058         if (error) {
3059                 if (error != -EOPNOTSUPP) {
3060                         iput(inode);
3061                         return error;
3062                 }
3063                 error = 0;
3064         }
3065 
3066         info = SHMEM_I(inode);
3067         inode->i_size = len-1;
3068         if (len <= SHORT_SYMLINK_LEN) {
3069                 inode->i_link = kmemdup(symname, len, GFP_KERNEL);
3070                 if (!inode->i_link) {
3071                         iput(inode);
3072                         return -ENOMEM;
3073                 }
3074                 inode->i_op = &shmem_short_symlink_operations;
3075         } else {
3076                 inode_nohighmem(inode);
3077                 error = shmem_getpage(inode, 0, &page, SGP_WRITE);
3078                 if (error) {
3079                         iput(inode);
3080                         return error;
3081                 }
3082                 inode->i_mapping->a_ops = &shmem_aops;
3083                 inode->i_op = &shmem_symlink_inode_operations;
3084                 memcpy(page_address(page), symname, len);
3085                 SetPageUptodate(page);
3086                 set_page_dirty(page);
3087                 unlock_page(page);
3088                 put_page(page);
3089         }
3090         dir->i_size += BOGO_DIRENT_SIZE;
3091         dir->i_ctime = dir->i_mtime = current_time(dir);
3092         d_instantiate(dentry, inode);
3093         dget(dentry);
3094         return 0;
3095 }
3096 
3097 static void shmem_put_link(void *arg)
3098 {
3099         mark_page_accessed(arg);
3100         put_page(arg);
3101 }
3102 
3103 static const char *shmem_get_link(struct dentry *dentry,
3104                                   struct inode *inode,
3105                                   struct delayed_call *done)
3106 {
3107         struct page *page = NULL;
3108         int error;
3109         if (!dentry) {
3110                 page = find_get_page(inode->i_mapping, 0);
3111                 if (!page)
3112                         return ERR_PTR(-ECHILD);
3113                 if (!PageUptodate(page)) {
3114                         put_page(page);
3115                         return ERR_PTR(-ECHILD);
3116                 }
3117         } else {
3118                 error = shmem_getpage(inode, 0, &page, SGP_READ);
3119                 if (error)
3120                         return ERR_PTR(error);
3121                 unlock_page(page);
3122         }
3123         set_delayed_call(done, shmem_put_link, page);
3124         return page_address(page);
3125 }
3126 
3127 #ifdef CONFIG_TMPFS_XATTR
3128 /*
3129  * Superblocks without xattr inode operations may get some security.* xattr
3130  * support from the LSM "for free". As soon as we have any other xattrs
3131  * like ACLs, we also need to implement the security.* handlers at
3132  * filesystem level, though.
3133  */
3134 
3135 /*
3136  * Callback for security_inode_init_security() for acquiring xattrs.
3137  */
3138 static int shmem_initxattrs(struct inode *inode,
3139                             const struct xattr *xattr_array,
3140                             void *fs_info)
3141 {
3142         struct shmem_inode_info *info = SHMEM_I(inode);
3143         const struct xattr *xattr;
3144         struct simple_xattr *new_xattr;
3145         size_t len;
3146 
3147         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
3148                 new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len);
3149                 if (!new_xattr)
3150                         return -ENOMEM;
3151 
3152                 len = strlen(xattr->name) + 1;
3153                 new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
3154                                           GFP_KERNEL);
3155                 if (!new_xattr->name) {
3156                         kfree(new_xattr);
3157                         return -ENOMEM;
3158                 }
3159 
3160                 memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
3161                        XATTR_SECURITY_PREFIX_LEN);
3162                 memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
3163                        xattr->name, len);
3164 
3165                 simple_xattr_list_add(&info->xattrs, new_xattr);
3166         }
3167 
3168         return 0;
3169 }
3170 
3171 static int shmem_xattr_handler_get(const struct xattr_handler *handler,
3172                                    struct dentry *unused, struct inode *inode,
3173                                    const char *name, void *buffer, size_t size)
3174 {
3175         struct shmem_inode_info *info = SHMEM_I(inode);
3176 
3177         name = xattr_full_name(handler, name);
3178         return simple_xattr_get(&info->xattrs, name, buffer, size);
3179 }
3180 
3181 static int shmem_xattr_handler_set(const struct xattr_handler *handler,
3182                                    struct dentry *unused, struct inode *inode,
3183                                    const char *name, const void *value,
3184                                    size_t size, int flags)
3185 {
3186         struct shmem_inode_info *info = SHMEM_I(inode);
3187 
3188         name = xattr_full_name(handler, name);
3189         return simple_xattr_set(&info->xattrs, name, value, size, flags);
3190 }
3191 
3192 static const struct xattr_handler shmem_security_xattr_handler = {
3193         .prefix = XATTR_SECURITY_PREFIX,
3194         .get = shmem_xattr_handler_get,
3195         .set = shmem_xattr_handler_set,
3196 };
3197 
3198 static const struct xattr_handler shmem_trusted_xattr_handler = {
3199         .prefix = XATTR_TRUSTED_PREFIX,
3200         .get = shmem_xattr_handler_get,
3201         .set = shmem_xattr_handler_set,
3202 };
3203 
3204 static const struct xattr_handler *shmem_xattr_handlers[] = {
3205 #ifdef CONFIG_TMPFS_POSIX_ACL
3206         &posix_acl_access_xattr_handler,
3207         &posix_acl_default_xattr_handler,
3208 #endif
3209         &shmem_security_xattr_handler,
3210         &shmem_trusted_xattr_handler,
3211         NULL
3212 };
3213 
3214 static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
3215 {
3216         struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
3217         return simple_xattr_list(d_inode(dentry), &info->xattrs, buffer, size);
3218 }
3219 #endif /* CONFIG_TMPFS_XATTR */
3220 
3221 static const struct inode_operations shmem_short_symlink_operations = {
3222         .get_link       = simple_get_link,
3223 #ifdef CONFIG_TMPFS_XATTR
3224         .listxattr      = shmem_listxattr,
3225 #endif
3226 };
3227 
3228 static const struct inode_operations shmem_symlink_inode_operations = {
3229         .get_link       = shmem_get_link,
3230 #ifdef CONFIG_TMPFS_XATTR
3231         .listxattr      = shmem_listxattr,
3232 #endif
3233 };
3234 
3235 static struct dentry *shmem_get_parent(struct dentry *child)
3236 {
3237         return ERR_PTR(-ESTALE);
3238 }
3239 
3240 static int shmem_match(struct inode *ino, void *vfh)
3241 {
3242         __u32 *fh = vfh;
3243         __u64 inum = fh[2];
3244         inum = (inum << 32) | fh[1];
3245         return ino->i_ino == inum && fh[0] == ino->i_generation;
3246 }
3247 
3248 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
3249                 struct fid *fid, int fh_len, int fh_type)
3250 {
3251         struct inode *inode;
3252         struct dentry *dentry = NULL;
3253         u64 inum;
3254 
3255         if (fh_len < 3)
3256                 return NULL;
3257 
3258         inum = fid->raw[2];
3259         inum = (inum << 32) | fid->raw[1];
3260 
3261         inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
3262                         shmem_match, fid->raw);
3263         if (inode) {
3264                 dentry = d_find_alias(inode);
3265                 iput(inode);
3266         }
3267 
3268         return dentry;
3269 }
3270 
3271 static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len,
3272                                 struct inode *parent)
3273 {
3274         if (*len < 3) {
3275                 *len = 3;
3276                 return FILEID_INVALID;
3277         }
3278 
3279         if (inode_unhashed(inode)) {
3280                 /* Unfortunately insert_inode_hash is not idempotent,
3281                  * so as we hash inodes here rather than at creation
3282                  * time, we need a lock to ensure we only try
3283                  * to do it once
3284                  */
3285                 static DEFINE_SPINLOCK(lock);
3286                 spin_lock(&lock);
3287                 if (inode_unhashed(inode))
3288                         __insert_inode_hash(inode,
3289                                             inode->i_ino + inode->i_generation);
3290                 spin_unlock(&lock);
3291         }
3292 
3293         fh[0] = inode->i_generation;
3294         fh[1] = inode->i_ino;
3295         fh[2] = ((__u64)inode->i_ino) >> 32;
3296 
3297         *len = 3;
3298         return 1;
3299 }
3300 
3301 static const struct export_operations shmem_export_ops = {
3302         .get_parent     = shmem_get_parent,
3303         .encode_fh      = shmem_encode_fh,
3304         .fh_to_dentry   = shmem_fh_to_dentry,
3305 };
3306 
3307 static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
3308                                bool remount)
3309 {
3310         char *this_char, *value, *rest;
3311         struct mempolicy *mpol = NULL;
3312         uid_t uid;
3313         gid_t gid;
3314 
3315         while (options != NULL) {
3316                 this_char = options;
3317                 for (;;) {
3318                         /*
3319                          * NUL-terminate this option: unfortunately,
3320                          * mount options form a comma-separated list,
3321                          * but mpol's nodelist may also contain commas.
3322                          */
3323                         options = strchr(options, ',');
3324                         if (options == NULL)
3325                                 break;
3326                         options++;
3327                         if (!isdigit(*options)) {
3328                                 options[-1] = '\0';
3329                                 break;
3330                         }
3331                 }
3332                 if (!*this_char)
3333                         continue;
3334                 if ((value = strchr(this_char,'=')) != NULL) {
3335                         *value++ = 0;
3336                 } else {
3337                         pr_err("tmpfs: No value for mount option '%s'\n",
3338                                this_char);
3339                         goto error;
3340                 }
3341 
3342                 if (!strcmp(this_char,"size")) {
3343                         unsigned long long size;
3344                         size = memparse(value,&rest);
3345                         if (*rest == '%') {
3346                                 size <<= PAGE_SHIFT;
3347                                 size *= totalram_pages;
3348                                 do_div(size, 100);
3349                                 rest++;
3350                         }
3351                         if (*rest)
3352                                 goto bad_val;
3353                         sbinfo->max_blocks =
3354                                 DIV_ROUND_UP(size, PAGE_SIZE);
3355                 } else if (!strcmp(this_char,"nr_blocks")) {
3356                         sbinfo->max_blocks = memparse(value, &rest);
3357                         if (*rest)
3358                                 goto bad_val;
3359                 } else if (!strcmp(this_char,"nr_inodes")) {
3360                         sbinfo->max_inodes = memparse(value, &rest);
3361                         if (*rest)
3362                                 goto bad_val;
3363                 } else if (!strcmp(this_char,"mode")) {
3364                         if (remount)
3365                                 continue;
3366                         sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
3367                         if (*rest)
3368                                 goto bad_val;
3369                 } else if (!strcmp(this_char,"uid")) {
3370                         if (remount)
3371                                 continue;
3372                         uid = simple_strtoul(value, &rest, 0);
3373                         if (*rest)
3374                                 goto bad_val;
3375                         sbinfo->uid = make_kuid(current_user_ns(), uid);
3376                         if (!uid_valid(sbinfo->uid))
3377                                 goto bad_val;
3378                 } else if (!strcmp(this_char,"gid")) {
3379                         if (remount)
3380                                 continue;
3381                         gid = simple_strtoul(value, &rest, 0);
3382                         if (*rest)
3383                                 goto bad_val;
3384                         sbinfo->gid = make_kgid(current_user_ns(), gid);
3385                         if (!gid_valid(sbinfo->gid))
3386                                 goto bad_val;
3387 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
3388                 } else if (!strcmp(this_char, "huge")) {
3389                         int huge;
3390                         huge = shmem_parse_huge(value);
3391                         if (huge < 0)
3392                                 goto bad_val;
3393                         if (!has_transparent_hugepage() &&
3394                                         huge != SHMEM_HUGE_NEVER)
3395                                 goto bad_val;
3396                         sbinfo->huge = huge;
3397 #endif
3398 #ifdef CONFIG_NUMA
3399                 } else if (!strcmp(this_char,"mpol")) {
3400                         mpol_put(mpol);
3401                         mpol = NULL;
3402                         if (mpol_parse_str(value, &mpol))
3403                                 goto bad_val;
3404 #endif
3405                 } else {
3406                         pr_err("tmpfs: Bad mount option %s\n", this_char);
3407                         goto error;
3408                 }
3409         }
3410         sbinfo->mpol = mpol;
3411         return 0;
3412 
3413 bad_val:
3414         pr_err("tmpfs: Bad value '%s' for mount option '%s'\n",
3415                value, this_char);
3416 error:
3417         mpol_put(mpol);
3418         return 1;
3419 
3420 }
3421 
3422 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
3423 {
3424         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
3425         struct shmem_sb_info config = *sbinfo;
3426         unsigned long inodes;
3427         int error = -EINVAL;
3428 
3429         config.mpol = NULL;
3430         if (shmem_parse_options(data, &config, true))
3431                 return error;
3432 
3433         spin_lock(&sbinfo->stat_lock);
3434         inodes = sbinfo->max_inodes - sbinfo->free_inodes;
3435         if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0)
3436                 goto out;
3437         if (config.max_inodes < inodes)
3438                 goto out;
3439         /*
3440          * Those tests disallow limited->unlimited while any are in use;
3441          * but we must separately disallow unlimited->limited, because
3442          * in that case we have no record of how much is already in use.
3443          */
3444         if (config.max_blocks && !sbinfo->max_blocks)
3445                 goto out;
3446         if (config.max_inodes && !sbinfo->max_inodes)
3447                 goto out;
3448 
3449         error = 0;
3450         sbinfo->huge = config.huge;
3451         sbinfo->max_blocks  = config.max_blocks;
3452         sbinfo->max_inodes  = config.max_inodes;
3453         sbinfo->free_inodes = config.max_inodes - inodes;
3454 
3455         /*
3456          * Preserve previous mempolicy unless mpol remount option was specified.
3457          */
3458         if (config.mpol) {
3459                 mpol_put(sbinfo->mpol);
3460                 sbinfo->mpol = config.mpol;     /* transfers initial ref */
3461         }
3462 out:
3463         spin_unlock(&sbinfo->stat_lock);
3464         return error;
3465 }
3466 
3467 static int shmem_show_options(struct seq_file *seq, struct dentry *root)
3468 {
3469         struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb);
3470 
3471         if (sbinfo->max_blocks != shmem_default_max_blocks())
3472                 seq_printf(seq, ",size=%luk",
3473                         sbinfo->max_blocks << (PAGE_SHIFT - 10));
3474         if (sbinfo->max_inodes != shmem_default_max_inodes())
3475                 seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
3476         if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
3477                 seq_printf(seq, ",mode=%03ho", sbinfo->mode);
3478         if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
3479                 seq_printf(seq, ",uid=%u",
3480                                 from_kuid_munged(&init_user_ns, sbinfo->uid));
3481         if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
3482                 seq_printf(seq, ",gid=%u",
3483                                 from_kgid_munged(&init_user_ns, sbinfo->gid));
3484 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
3485         /* Rightly or wrongly, show huge mount option unmasked by shmem_huge */
3486         if (sbinfo->huge)
3487                 seq_printf(seq, ",huge=%s", shmem_format_huge(sbinfo->huge));
3488 #endif
3489         shmem_show_mpol(seq, sbinfo->mpol);
3490         return 0;
3491 }
3492 
3493 #define MFD_NAME_PREFIX "memfd:"
3494 #define MFD_NAME_PREFIX_LEN (sizeof(MFD_NAME_PREFIX) - 1)
3495 #define MFD_NAME_MAX_LEN (NAME_MAX - MFD_NAME_PREFIX_LEN)
3496 
3497 #define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING)
3498 
3499 SYSCALL_DEFINE2(memfd_create,
3500                 const char __user *, uname,
3501                 unsigned int, flags)
3502 {
3503         struct shmem_inode_info *info;
3504         struct file *file;
3505         int fd, error;
3506         char *name;
3507         long len;
3508 
3509         if (flags & ~(unsigned int)MFD_ALL_FLAGS)
3510                 return -EINVAL;
3511 
3512         /* length includes terminating zero */
3513         len = strnlen_user(uname, MFD_NAME_MAX_LEN + 1);
3514         if (len <= 0)
3515                 return -EFAULT;
3516         if (len > MFD_NAME_MAX_LEN + 1)
3517                 return -EINVAL;
3518 
3519         name = kmalloc(len + MFD_NAME_PREFIX_LEN, GFP_TEMPORARY);
3520         if (!name)
3521                 return -ENOMEM;
3522 
3523         strcpy(name, MFD_NAME_PREFIX);
3524         if (copy_from_user(&name[MFD_NAME_PREFIX_LEN], uname, len)) {
3525                 error = -EFAULT;
3526                 goto err_name;
3527         }
3528 
3529         /* terminating-zero may have changed after strnlen_user() returned */
3530         if (name[len + MFD_NAME_PREFIX_LEN - 1]) {
3531                 error = -EFAULT;
3532                 goto err_name;
3533         }
3534 
3535         fd = get_unused_fd_flags((flags & MFD_CLOEXEC) ? O_CLOEXEC : 0);
3536         if (fd < 0) {
3537                 error = fd;
3538                 goto err_name;
3539         }
3540 
3541         file = shmem_file_setup(name, 0, VM_NORESERVE);
3542         if (IS_ERR(file)) {
3543                 error = PTR_ERR(file);
3544                 goto err_fd;
3545         }
3546         info = SHMEM_I(file_inode(file));
3547         file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
3548         file->f_flags |= O_RDWR | O_LARGEFILE;
3549         if (flags & MFD_ALLOW_SEALING)
3550                 info->seals &= ~F_SEAL_SEAL;
3551 
3552         fd_install(fd, file);
3553         kfree(name);
3554         return fd;
3555 
3556 err_fd:
3557         put_unused_fd(fd);
3558 err_name:
3559         kfree(name);
3560         return error;
3561 }
3562 
3563 #endif /* CONFIG_TMPFS */
3564 
3565 static void shmem_put_super(struct super_block *sb)
3566 {
3567         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
3568 
3569         percpu_counter_destroy(&sbinfo->used_blocks);
3570         mpol_put(sbinfo->mpol);
3571         kfree(sbinfo);
3572         sb->s_fs_info = NULL;
3573 }
3574 
3575 int shmem_fill_super(struct super_block *sb, void *data, int silent)
3576 {
3577         struct inode *inode;
3578         struct shmem_sb_info *sbinfo;
3579         int err = -ENOMEM;
3580 
3581         /* Round up to L1_CACHE_BYTES to resist false sharing */
3582         sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
3583                                 L1_CACHE_BYTES), GFP_KERNEL);
3584         if (!sbinfo)
3585                 return -ENOMEM;
3586 
3587         sbinfo->mode = S_IRWXUGO | S_ISVTX;
3588         sbinfo->uid = current_fsuid();
3589         sbinfo->gid = current_fsgid();
3590         sb->s_fs_info = sbinfo;
3591 
3592 #ifdef CONFIG_TMPFS
3593         /*
3594          * Per default we only allow half of the physical ram per
3595          * tmpfs instance, limiting inodes to one per page of lowmem;
3596          * but the internal instance is left unlimited.
3597          */
3598         if (!(sb->s_flags & MS_KERNMOUNT)) {
3599                 sbinfo->max_blocks = shmem_default_max_blocks();
3600                 sbinfo->max_inodes = shmem_default_max_inodes();
3601                 if (shmem_parse_options(data, sbinfo, false)) {
3602                         err = -EINVAL;
3603                         goto failed;
3604                 }
3605         } else {
3606                 sb->s_flags |= MS_NOUSER;
3607         }
3608         sb->s_export_op = &shmem_export_ops;
3609         sb->s_flags |= MS_NOSEC;
3610 #else
3611         sb->s_flags |= MS_NOUSER;
3612 #endif
3613 
3614         spin_lock_init(&sbinfo->stat_lock);
3615         if (percpu_counter_init(&sbinfo->used_blocks, 0, GFP_KERNEL))
3616                 goto failed;
3617         sbinfo->free_inodes = sbinfo->max_inodes;
3618         spin_lock_init(&sbinfo->shrinklist_lock);
3619         INIT_LIST_HEAD(&sbinfo->shrinklist);
3620 
3621         sb->s_maxbytes = MAX_LFS_FILESIZE;
3622         sb->s_blocksize = PAGE_SIZE;
3623         sb->s_blocksize_bits = PAGE_SHIFT;
3624         sb->s_magic = TMPFS_MAGIC;
3625         sb->s_op = &shmem_ops;
3626         sb->s_time_gran = 1;
3627 #ifdef CONFIG_TMPFS_XATTR
3628         sb->s_xattr = shmem_xattr_handlers;
3629 #endif
3630 #ifdef CONFIG_TMPFS_POSIX_ACL
3631         sb->s_flags |= MS_POSIXACL;
3632 #endif
3633 
3634         inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
3635         if (!inode)
3636                 goto failed;
3637         inode->i_uid = sbinfo->uid;
3638         inode->i_gid = sbinfo->gid;
3639         sb->s_root = d_make_root(inode);
3640         if (!sb->s_root)
3641                 goto failed;
3642         return 0;
3643 
3644 failed:
3645         shmem_put_super(sb);
3646         return err;
3647 }
3648 
3649 static struct kmem_cache *shmem_inode_cachep;
3650 
3651 static struct inode *shmem_alloc_inode(struct super_block *sb)
3652 {
3653         struct shmem_inode_info *info;
3654         info = kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
3655         if (!info)
3656                 return NULL;
3657         return &info->vfs_inode;
3658 }
3659 
3660 static void shmem_destroy_callback(struct rcu_head *head)
3661 {
3662         struct inode *inode = container_of(head, struct inode, i_rcu);
3663         if (S_ISLNK(inode->i_mode))
3664                 kfree(inode->i_link);
3665         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
3666 }
3667 
3668 static void shmem_destroy_inode(struct inode *inode)
3669 {
3670         if (S_ISREG(inode->i_mode))
3671                 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
3672         call_rcu(&inode->i_rcu, shmem_destroy_callback);
3673 }
3674 
3675 static void shmem_init_inode(void *foo)
3676 {
3677         struct shmem_inode_info *info = foo;
3678         inode_init_once(&info->vfs_inode);
3679 }
3680 
3681 static int shmem_init_inodecache(void)
3682 {
3683         shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
3684                                 sizeof(struct shmem_inode_info),
3685                                 0, SLAB_PANIC|SLAB_ACCOUNT, shmem_init_inode);
3686         return 0;
3687 }
3688 
3689 static void shmem_destroy_inodecache(void)
3690 {
3691         kmem_cache_destroy(shmem_inode_cachep);
3692 }
3693 
3694 static const struct address_space_operations shmem_aops = {
3695         .writepage      = shmem_writepage,
3696         .set_page_dirty = __set_page_dirty_no_writeback,
3697 #ifdef CONFIG_TMPFS
3698         .write_begin    = shmem_write_begin,
3699         .write_end      = shmem_write_end,
3700 #endif
3701 #ifdef CONFIG_MIGRATION
3702         .migratepage    = migrate_page,
3703 #endif
3704         .error_remove_page = generic_error_remove_page,
3705 };
3706 
3707 static const struct file_operations shmem_file_operations = {
3708         .mmap           = shmem_mmap,
3709         .get_unmapped_area = shmem_get_unmapped_area,
3710 #ifdef CONFIG_TMPFS
3711         .llseek         = shmem_file_llseek,
3712         .read_iter      = shmem_file_read_iter,
3713         .write_iter     = generic_file_write_iter,
3714         .fsync          = noop_fsync,
3715         .splice_read    = generic_file_splice_read,
3716         .splice_write   = iter_file_splice_write,
3717         .fallocate      = shmem_fallocate,
3718 #endif
3719 };
3720 
3721 static const struct inode_operations shmem_inode_operations = {
3722         .getattr        = shmem_getattr,
3723         .setattr        = shmem_setattr,
3724 #ifdef CONFIG_TMPFS_XATTR
3725         .listxattr      = shmem_listxattr,
3726         .set_acl        = simple_set_acl,
3727 #endif
3728 };
3729 
3730 static const struct inode_operations shmem_dir_inode_operations = {
3731 #ifdef CONFIG_TMPFS
3732         .create         = shmem_create,
3733         .lookup         = simple_lookup,
3734         .link           = shmem_link,
3735         .unlink         = shmem_unlink,
3736         .symlink        = shmem_symlink,
3737         .mkdir          = shmem_mkdir,
3738         .rmdir          = shmem_rmdir,
3739         .mknod          = shmem_mknod,
3740         .rename         = shmem_rename2,
3741         .tmpfile        = shmem_tmpfile,
3742 #endif
3743 #ifdef CONFIG_TMPFS_XATTR
3744         .listxattr      = shmem_listxattr,
3745 #endif
3746 #ifdef CONFIG_TMPFS_POSIX_ACL
3747         .setattr        = shmem_setattr,
3748         .set_acl        = simple_set_acl,
3749 #endif
3750 };
3751 
3752 static const struct inode_operations shmem_special_inode_operations = {
3753 #ifdef CONFIG_TMPFS_XATTR
3754         .listxattr      = shmem_listxattr,
3755 #endif
3756 #ifdef CONFIG_TMPFS_POSIX_ACL
3757         .setattr        = shmem_setattr,
3758         .set_acl        = simple_set_acl,
3759 #endif
3760 };
3761 
3762 static const struct super_operations shmem_ops = {
3763         .alloc_inode    = shmem_alloc_inode,
3764         .destroy_inode  = shmem_destroy_inode,
3765 #ifdef CONFIG_TMPFS
3766         .statfs         = shmem_statfs,
3767         .remount_fs     = shmem_remount_fs,
3768         .show_options   = shmem_show_options,
3769 #endif
3770         .evict_inode    = shmem_evict_inode,
3771         .drop_inode     = generic_delete_inode,
3772         .put_super      = shmem_put_super,
3773 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
3774         .nr_cached_objects      = shmem_unused_huge_count,
3775         .free_cached_objects    = shmem_unused_huge_scan,
3776 #endif
3777 };
3778 
3779 static const struct vm_operations_struct shmem_vm_ops = {
3780         .fault          = shmem_fault,
3781         .map_pages      = filemap_map_pages,
3782 #ifdef CONFIG_NUMA
3783         .set_policy     = shmem_set_policy,
3784         .get_policy     = shmem_get_policy,
3785 #endif
3786 };
3787 
3788 static struct dentry *shmem_mount(struct file_system_type *fs_type,
3789         int flags, const char *dev_name, void *data)
3790 {
3791         return mount_nodev(fs_type, flags, data, shmem_fill_super);
3792 }
3793 
3794 static struct file_system_type shmem_fs_type = {
3795         .owner          = THIS_MODULE,
3796         .name           = "tmpfs",
3797         .mount          = shmem_mount,
3798         .kill_sb        = kill_litter_super,
3799         .fs_flags       = FS_USERNS_MOUNT,
3800 };
3801 
3802 int __init shmem_init(void)
3803 {
3804         int error;
3805 
3806         /* If rootfs called this, don't re-init */
3807         if (shmem_inode_cachep)
3808                 return 0;
3809 
3810         error = shmem_init_inodecache();
3811         if (error)
3812                 goto out3;
3813 
3814         error = register_filesystem(&shmem_fs_type);
3815         if (error) {
3816                 pr_err("Could not register tmpfs\n");
3817                 goto out2;
3818         }
3819 
3820         shm_mnt = kern_mount(&shmem_fs_type);
3821         if (IS_ERR(shm_mnt)) {
3822                 error = PTR_ERR(shm_mnt);
3823                 pr_err("Could not kern_mount tmpfs\n");
3824                 goto out1;
3825         }
3826 
3827 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
3828         if (has_transparent_hugepage() && shmem_huge < SHMEM_HUGE_DENY)
3829                 SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
3830         else
3831                 shmem_huge = 0; /* just in case it was patched */
3832 #endif
3833         return 0;
3834 
3835 out1:
3836         unregister_filesystem(&shmem_fs_type);
3837 out2:
3838         shmem_destroy_inodecache();
3839 out3:
3840         shm_mnt = ERR_PTR(error);
3841         return error;
3842 }
3843 
3844 #if defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE) && defined(CONFIG_SYSFS)
3845 static ssize_t shmem_enabled_show(struct kobject *kobj,
3846                 struct kobj_attribute *attr, char *buf)
3847 {
3848         int values[] = {
3849                 SHMEM_HUGE_ALWAYS,
3850                 SHMEM_HUGE_WITHIN_SIZE,
3851                 SHMEM_HUGE_ADVISE,
3852                 SHMEM_HUGE_NEVER,
3853                 SHMEM_HUGE_DENY,
3854                 SHMEM_HUGE_FORCE,
3855         };
3856         int i, count;
3857 
3858         for (i = 0, count = 0; i < ARRAY_SIZE(values); i++) {
3859                 const char *fmt = shmem_huge == values[i] ? "[%s] " : "%s ";
3860 
3861                 count += sprintf(buf + count, fmt,
3862                                 shmem_format_huge(values[i]));
3863         }
3864         buf[count - 1] = '\n';
3865         return count;
3866 }
3867 
3868 static ssize_t shmem_enabled_store(struct kobject *kobj,
3869                 struct kobj_attribute *attr, const char *buf, size_t count)
3870 {
3871         char tmp[16];
3872         int huge;
3873 
3874         if (count + 1 > sizeof(tmp))
3875                 return -EINVAL;
3876         memcpy(tmp, buf, count);
3877         tmp[count] = '\0';
3878         if (count && tmp[count - 1] == '\n')
3879                 tmp[count - 1] = '\0';
3880 
3881         huge = shmem_parse_huge(tmp);
3882         if (huge == -EINVAL)
3883                 return -EINVAL;
3884         if (!has_transparent_hugepage() &&
3885                         huge != SHMEM_HUGE_NEVER && huge != SHMEM_HUGE_DENY)
3886                 return -EINVAL;
3887 
3888         shmem_huge = huge;
3889         if (shmem_huge < SHMEM_HUGE_DENY)
3890                 SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
3891         return count;
3892 }
3893 
3894 struct kobj_attribute shmem_enabled_attr =
3895         __ATTR(shmem_enabled, 0644, shmem_enabled_show, shmem_enabled_store);
3896 #endif /* CONFIG_TRANSPARENT_HUGE_PAGECACHE && CONFIG_SYSFS */
3897 
3898 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
3899 bool shmem_huge_enabled(struct vm_area_struct *vma)
3900 {
3901         struct inode *inode = file_inode(vma->vm_file);
3902         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
3903         loff_t i_size;
3904         pgoff_t off;
3905 
3906         if (shmem_huge == SHMEM_HUGE_FORCE)
3907                 return true;
3908         if (shmem_huge == SHMEM_HUGE_DENY)
3909                 return false;
3910         switch (sbinfo->huge) {
3911                 case SHMEM_HUGE_NEVER:
3912                         return false;
3913                 case SHMEM_HUGE_ALWAYS:
3914                         return true;
3915                 case SHMEM_HUGE_WITHIN_SIZE:
3916                         off = round_up(vma->vm_pgoff, HPAGE_PMD_NR);
3917                         i_size = round_up(i_size_read(inode), PAGE_SIZE);
3918                         if (i_size >= HPAGE_PMD_SIZE &&
3919                                         i_size >> PAGE_SHIFT >= off)
3920                                 return true;
3921                 case SHMEM_HUGE_ADVISE:
3922                         /* TODO: implement fadvise() hints */
3923                         return (vma->vm_flags & VM_HUGEPAGE);
3924                 default:
3925                         VM_BUG_ON(1);
3926                         return false;
3927         }
3928 }
3929 #endif /* CONFIG_TRANSPARENT_HUGE_PAGECACHE */
3930 
3931 #else /* !CONFIG_SHMEM */
3932 
3933 /*
3934  * tiny-shmem: simple shmemfs and tmpfs using ramfs code
3935  *
3936  * This is intended for small system where the benefits of the full
3937  * shmem code (swap-backed and resource-limited) are outweighed by
3938  * their complexity. On systems without swap this code should be
3939  * effectively equivalent, but much lighter weight.
3940  */
3941 
3942 static struct file_system_type shmem_fs_type = {
3943         .name           = "tmpfs",
3944         .mount          = ramfs_mount,
3945         .kill_sb        = kill_litter_super,
3946         .fs_flags       = FS_USERNS_MOUNT,
3947 };
3948 
3949 int __init shmem_init(void)
3950 {
3951         BUG_ON(register_filesystem(&shmem_fs_type) != 0);
3952 
3953         shm_mnt = kern_mount(&shmem_fs_type);
3954         BUG_ON(IS_ERR(shm_mnt));
3955 
3956         return 0;
3957 }
3958 
3959 int shmem_unuse(swp_entry_t swap, struct page *page)
3960 {
3961         return 0;
3962 }
3963 
3964 int shmem_lock(struct file *file, int lock, struct user_struct *user)
3965 {
3966         return 0;
3967 }
3968 
3969 void shmem_unlock_mapping(struct address_space *mapping)
3970 {
3971 }
3972 
3973 #ifdef CONFIG_MMU
3974 unsigned long shmem_get_unmapped_area(struct file *file,
3975                                       unsigned long addr, unsigned long len,
3976                                       unsigned long pgoff, unsigned long flags)
3977 {
3978         return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
3979 }
3980 #endif
3981 
3982 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
3983 {
3984         truncate_inode_pages_range(inode->i_mapping, lstart, lend);
3985 }
3986 EXPORT_SYMBOL_GPL(shmem_truncate_range);
3987 
3988 #define shmem_vm_ops                            generic_file_vm_ops
3989 #define shmem_file_operations                   ramfs_file_operations
3990 #define shmem_get_inode(sb, dir, mode, dev, flags)      ramfs_get_inode(sb, dir, mode, dev)
3991 #define shmem_acct_size(flags, size)            0
3992 #define shmem_unacct_size(flags, size)          do {} while (0)
3993 
3994 #endif /* CONFIG_SHMEM */
3995 
3996 /* common code */
3997 
3998 static const struct dentry_operations anon_ops = {
3999         .d_dname = simple_dname
4000 };
4001 
4002 static struct file *__shmem_file_setup(const char *name, loff_t size,
4003                                        unsigned long flags, unsigned int i_flags)
4004 {
4005         struct file *res;
4006         struct inode *inode;
4007         struct path path;
4008         struct super_block *sb;
4009         struct qstr this;
4010 
4011         if (IS_ERR(shm_mnt))
4012                 return ERR_CAST(shm_mnt);
4013 
4014         if (size < 0 || size > MAX_LFS_FILESIZE)
4015                 return ERR_PTR(-EINVAL);
4016 
4017         if (shmem_acct_size(flags, size))
4018                 return ERR_PTR(-ENOMEM);
4019 
4020         res = ERR_PTR(-ENOMEM);
4021         this.name = name;
4022         this.len = strlen(name);
4023         this.hash = 0; /* will go */
4024         sb = shm_mnt->mnt_sb;
4025         path.mnt = mntget(shm_mnt);
4026         path.dentry = d_alloc_pseudo(sb, &this);
4027         if (!path.dentry)
4028                 goto put_memory;
4029         d_set_d_op(path.dentry, &anon_ops);
4030 
4031         res = ERR_PTR(-ENOSPC);
4032         inode = shmem_get_inode(sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
4033         if (!inode)
4034                 goto put_memory;
4035 
4036         inode->i_flags |= i_flags;
4037         d_instantiate(path.dentry, inode);
4038         inode->i_size = size;
4039         clear_nlink(inode);     /* It is unlinked */
4040         res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size));
4041         if (IS_ERR(res))
4042                 goto put_path;
4043 
4044         res = alloc_file(&path, FMODE_WRITE | FMODE_READ,
4045                   &shmem_file_operations);
4046         if (IS_ERR(res))
4047                 goto put_path;
4048 
4049         return res;
4050 
4051 put_memory:
4052         shmem_unacct_size(flags, size);
4053 put_path:
4054         path_put(&path);
4055         return res;
4056 }
4057 
4058 /**
4059  * shmem_kernel_file_setup - get an unlinked file living in tmpfs which must be
4060  *      kernel internal.  There will be NO LSM permission checks against the
4061  *      underlying inode.  So users of this interface must do LSM checks at a
4062  *      higher layer.  The users are the big_key and shm implementations.  LSM
4063  *      checks are provided at the key or shm level rather than the inode.
4064  * @name: name for dentry (to be seen in /proc/<pid>/maps
4065  * @size: size to be set for the file
4066  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
4067  */
4068 struct file *shmem_kernel_file_setup(const char *name, loff_t size, unsigned long flags)
4069 {
4070         return __shmem_file_setup(name, size, flags, S_PRIVATE);
4071 }
4072 
4073 /**
4074  * shmem_file_setup - get an unlinked file living in tmpfs
4075  * @name: name for dentry (to be seen in /proc/<pid>/maps
4076  * @size: size to be set for the file
4077  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
4078  */
4079 struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
4080 {
4081         return __shmem_file_setup(name, size, flags, 0);
4082 }
4083 EXPORT_SYMBOL_GPL(shmem_file_setup);
4084 
4085 /**
4086  * shmem_zero_setup - setup a shared anonymous mapping
4087  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
4088  */
4089 int shmem_zero_setup(struct vm_area_struct *vma)
4090 {
4091         struct file *file;
4092         loff_t size = vma->vm_end - vma->vm_start;
4093 
4094         /*
4095          * Cloning a new file under mmap_sem leads to a lock ordering conflict
4096          * between XFS directory reading and selinux: since this file is only
4097          * accessible to the user through its mapping, use S_PRIVATE flag to
4098          * bypass file security, in the same way as shmem_kernel_file_setup().
4099          */
4100         file = __shmem_file_setup("dev/zero", size, vma->vm_flags, S_PRIVATE);
4101         if (IS_ERR(file))
4102                 return PTR_ERR(file);
4103 
4104         if (vma->vm_file)
4105                 fput(vma->vm_file);
4106         vma->vm_file = file;
4107         vma->vm_ops = &shmem_vm_ops;
4108 
4109         if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE) &&
4110                         ((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) <
4111                         (vma->vm_end & HPAGE_PMD_MASK)) {
4112                 khugepaged_enter(vma, vma->vm_flags);
4113         }
4114 
4115         return 0;
4116 }
4117 
4118 /**
4119  * shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags.
4120  * @mapping:    the page's address_space
4121  * @index:      the page index
4122  * @gfp:        the page allocator flags to use if allocating
4123  *
4124  * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)",
4125  * with any new page allocations done using the specified allocation flags.
4126  * But read_cache_page_gfp() uses the ->readpage() method: which does not
4127  * suit tmpfs, since it may have pages in swapcache, and needs to find those
4128  * for itself; although drivers/gpu/drm i915 and ttm rely upon this support.
4129  *
4130  * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in
4131  * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily.
4132  */
4133 struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
4134                                          pgoff_t index, gfp_t gfp)
4135 {
4136 #ifdef CONFIG_SHMEM
4137         struct inode *inode = mapping->host;
4138         struct page *page;
4139         int error;
4140 
4141         BUG_ON(mapping->a_ops != &shmem_aops);
4142         error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE,
4143                                   gfp, NULL, NULL);
4144         if (error)
4145                 page = ERR_PTR(error);
4146         else
4147                 unlock_page(page);
4148         return page;
4149 #else
4150         /*
4151          * The tiny !SHMEM case uses ramfs without swap
4152          */
4153         return read_cache_page_gfp(mapping, index, gfp);
4154 #endif
4155 }
4156 EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);
4157 

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