Version:  2.0.40 2.2.26 2.4.37 2.6.39 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15

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/aio.h>
 35 
 36 static struct vfsmount *shm_mnt;
 37 
 38 #ifdef CONFIG_SHMEM
 39 /*
 40  * This virtual memory filesystem is heavily based on the ramfs. It
 41  * extends ramfs by the ability to use swap and honor resource limits
 42  * which makes it a completely usable filesystem.
 43  */
 44 
 45 #include <linux/xattr.h>
 46 #include <linux/exportfs.h>
 47 #include <linux/posix_acl.h>
 48 #include <linux/posix_acl_xattr.h>
 49 #include <linux/mman.h>
 50 #include <linux/string.h>
 51 #include <linux/slab.h>
 52 #include <linux/backing-dev.h>
 53 #include <linux/shmem_fs.h>
 54 #include <linux/writeback.h>
 55 #include <linux/blkdev.h>
 56 #include <linux/pagevec.h>
 57 #include <linux/percpu_counter.h>
 58 #include <linux/falloc.h>
 59 #include <linux/splice.h>
 60 #include <linux/security.h>
 61 #include <linux/swapops.h>
 62 #include <linux/mempolicy.h>
 63 #include <linux/namei.h>
 64 #include <linux/ctype.h>
 65 #include <linux/migrate.h>
 66 #include <linux/highmem.h>
 67 #include <linux/seq_file.h>
 68 #include <linux/magic.h>
 69 
 70 #include <asm/uaccess.h>
 71 #include <asm/pgtable.h>
 72 
 73 #define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
 74 #define VM_ACCT(size)    (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
 75 
 76 /* Pretend that each entry is of this size in directory's i_size */
 77 #define BOGO_DIRENT_SIZE 20
 78 
 79 /* Symlink up to this size is kmalloc'ed instead of using a swappable page */
 80 #define SHORT_SYMLINK_LEN 128
 81 
 82 /*
 83  * shmem_fallocate and shmem_writepage communicate via inode->i_private
 84  * (with i_mutex making sure that it has only one user at a time):
 85  * we would prefer not to enlarge the shmem inode just for that.
 86  */
 87 struct shmem_falloc {
 88         pgoff_t start;          /* start of range currently being fallocated */
 89         pgoff_t next;           /* the next page offset to be fallocated */
 90         pgoff_t nr_falloced;    /* how many new pages have been fallocated */
 91         pgoff_t nr_unswapped;   /* how often writepage refused to swap out */
 92 };
 93 
 94 /* Flag allocation requirements to shmem_getpage */
 95 enum sgp_type {
 96         SGP_READ,       /* don't exceed i_size, don't allocate page */
 97         SGP_CACHE,      /* don't exceed i_size, may allocate page */
 98         SGP_DIRTY,      /* like SGP_CACHE, but set new page dirty */
 99         SGP_WRITE,      /* may exceed i_size, may allocate !Uptodate page */
100         SGP_FALLOC,     /* like SGP_WRITE, but make existing page Uptodate */
101 };
102 
103 #ifdef CONFIG_TMPFS
104 static unsigned long shmem_default_max_blocks(void)
105 {
106         return totalram_pages / 2;
107 }
108 
109 static unsigned long shmem_default_max_inodes(void)
110 {
111         return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
112 }
113 #endif
114 
115 static bool shmem_should_replace_page(struct page *page, gfp_t gfp);
116 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
117                                 struct shmem_inode_info *info, pgoff_t index);
118 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
119         struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type);
120 
121 static inline int shmem_getpage(struct inode *inode, pgoff_t index,
122         struct page **pagep, enum sgp_type sgp, int *fault_type)
123 {
124         return shmem_getpage_gfp(inode, index, pagep, sgp,
125                         mapping_gfp_mask(inode->i_mapping), fault_type);
126 }
127 
128 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
129 {
130         return sb->s_fs_info;
131 }
132 
133 /*
134  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
135  * for shared memory and for shared anonymous (/dev/zero) mappings
136  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
137  * consistent with the pre-accounting of private mappings ...
138  */
139 static inline int shmem_acct_size(unsigned long flags, loff_t size)
140 {
141         return (flags & VM_NORESERVE) ?
142                 0 : security_vm_enough_memory_mm(current->mm, VM_ACCT(size));
143 }
144 
145 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
146 {
147         if (!(flags & VM_NORESERVE))
148                 vm_unacct_memory(VM_ACCT(size));
149 }
150 
151 /*
152  * ... whereas tmpfs objects are accounted incrementally as
153  * pages are allocated, in order to allow huge sparse files.
154  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
155  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
156  */
157 static inline int shmem_acct_block(unsigned long flags)
158 {
159         return (flags & VM_NORESERVE) ?
160                 security_vm_enough_memory_mm(current->mm, VM_ACCT(PAGE_CACHE_SIZE)) : 0;
161 }
162 
163 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
164 {
165         if (flags & VM_NORESERVE)
166                 vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
167 }
168 
169 static const struct super_operations shmem_ops;
170 static const struct address_space_operations shmem_aops;
171 static const struct file_operations shmem_file_operations;
172 static const struct inode_operations shmem_inode_operations;
173 static const struct inode_operations shmem_dir_inode_operations;
174 static const struct inode_operations shmem_special_inode_operations;
175 static const struct vm_operations_struct shmem_vm_ops;
176 
177 static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
178         .ra_pages       = 0,    /* No readahead */
179         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
180 };
181 
182 static LIST_HEAD(shmem_swaplist);
183 static DEFINE_MUTEX(shmem_swaplist_mutex);
184 
185 static int shmem_reserve_inode(struct super_block *sb)
186 {
187         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
188         if (sbinfo->max_inodes) {
189                 spin_lock(&sbinfo->stat_lock);
190                 if (!sbinfo->free_inodes) {
191                         spin_unlock(&sbinfo->stat_lock);
192                         return -ENOSPC;
193                 }
194                 sbinfo->free_inodes--;
195                 spin_unlock(&sbinfo->stat_lock);
196         }
197         return 0;
198 }
199 
200 static void shmem_free_inode(struct super_block *sb)
201 {
202         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
203         if (sbinfo->max_inodes) {
204                 spin_lock(&sbinfo->stat_lock);
205                 sbinfo->free_inodes++;
206                 spin_unlock(&sbinfo->stat_lock);
207         }
208 }
209 
210 /**
211  * shmem_recalc_inode - recalculate the block usage of an inode
212  * @inode: inode to recalc
213  *
214  * We have to calculate the free blocks since the mm can drop
215  * undirtied hole pages behind our back.
216  *
217  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
218  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
219  *
220  * It has to be called with the spinlock held.
221  */
222 static void shmem_recalc_inode(struct inode *inode)
223 {
224         struct shmem_inode_info *info = SHMEM_I(inode);
225         long freed;
226 
227         freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
228         if (freed > 0) {
229                 struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
230                 if (sbinfo->max_blocks)
231                         percpu_counter_add(&sbinfo->used_blocks, -freed);
232                 info->alloced -= freed;
233                 inode->i_blocks -= freed * BLOCKS_PER_PAGE;
234                 shmem_unacct_blocks(info->flags, freed);
235         }
236 }
237 
238 /*
239  * Replace item expected in radix tree by a new item, while holding tree lock.
240  */
241 static int shmem_radix_tree_replace(struct address_space *mapping,
242                         pgoff_t index, void *expected, void *replacement)
243 {
244         void **pslot;
245         void *item;
246 
247         VM_BUG_ON(!expected);
248         VM_BUG_ON(!replacement);
249         pslot = radix_tree_lookup_slot(&mapping->page_tree, index);
250         if (!pslot)
251                 return -ENOENT;
252         item = radix_tree_deref_slot_protected(pslot, &mapping->tree_lock);
253         if (item != expected)
254                 return -ENOENT;
255         radix_tree_replace_slot(pslot, replacement);
256         return 0;
257 }
258 
259 /*
260  * Sometimes, before we decide whether to proceed or to fail, we must check
261  * that an entry was not already brought back from swap by a racing thread.
262  *
263  * Checking page is not enough: by the time a SwapCache page is locked, it
264  * might be reused, and again be SwapCache, using the same swap as before.
265  */
266 static bool shmem_confirm_swap(struct address_space *mapping,
267                                pgoff_t index, swp_entry_t swap)
268 {
269         void *item;
270 
271         rcu_read_lock();
272         item = radix_tree_lookup(&mapping->page_tree, index);
273         rcu_read_unlock();
274         return item == swp_to_radix_entry(swap);
275 }
276 
277 /*
278  * Like add_to_page_cache_locked, but error if expected item has gone.
279  */
280 static int shmem_add_to_page_cache(struct page *page,
281                                    struct address_space *mapping,
282                                    pgoff_t index, gfp_t gfp, void *expected)
283 {
284         int error;
285 
286         VM_BUG_ON_PAGE(!PageLocked(page), page);
287         VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
288 
289         page_cache_get(page);
290         page->mapping = mapping;
291         page->index = index;
292 
293         spin_lock_irq(&mapping->tree_lock);
294         if (!expected)
295                 error = radix_tree_insert(&mapping->page_tree, index, page);
296         else
297                 error = shmem_radix_tree_replace(mapping, index, expected,
298                                                                  page);
299         if (!error) {
300                 mapping->nrpages++;
301                 __inc_zone_page_state(page, NR_FILE_PAGES);
302                 __inc_zone_page_state(page, NR_SHMEM);
303                 spin_unlock_irq(&mapping->tree_lock);
304         } else {
305                 page->mapping = NULL;
306                 spin_unlock_irq(&mapping->tree_lock);
307                 page_cache_release(page);
308         }
309         return error;
310 }
311 
312 /*
313  * Like delete_from_page_cache, but substitutes swap for page.
314  */
315 static void shmem_delete_from_page_cache(struct page *page, void *radswap)
316 {
317         struct address_space *mapping = page->mapping;
318         int error;
319 
320         spin_lock_irq(&mapping->tree_lock);
321         error = shmem_radix_tree_replace(mapping, page->index, page, radswap);
322         page->mapping = NULL;
323         mapping->nrpages--;
324         __dec_zone_page_state(page, NR_FILE_PAGES);
325         __dec_zone_page_state(page, NR_SHMEM);
326         spin_unlock_irq(&mapping->tree_lock);
327         page_cache_release(page);
328         BUG_ON(error);
329 }
330 
331 /*
332  * Remove swap entry from radix tree, free the swap and its page cache.
333  */
334 static int shmem_free_swap(struct address_space *mapping,
335                            pgoff_t index, void *radswap)
336 {
337         void *old;
338 
339         spin_lock_irq(&mapping->tree_lock);
340         old = radix_tree_delete_item(&mapping->page_tree, index, radswap);
341         spin_unlock_irq(&mapping->tree_lock);
342         if (old != radswap)
343                 return -ENOENT;
344         free_swap_and_cache(radix_to_swp_entry(radswap));
345         return 0;
346 }
347 
348 /*
349  * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists.
350  */
351 void shmem_unlock_mapping(struct address_space *mapping)
352 {
353         struct pagevec pvec;
354         pgoff_t indices[PAGEVEC_SIZE];
355         pgoff_t index = 0;
356 
357         pagevec_init(&pvec, 0);
358         /*
359          * Minor point, but we might as well stop if someone else SHM_LOCKs it.
360          */
361         while (!mapping_unevictable(mapping)) {
362                 /*
363                  * Avoid pagevec_lookup(): find_get_pages() returns 0 as if it
364                  * has finished, if it hits a row of PAGEVEC_SIZE swap entries.
365                  */
366                 pvec.nr = find_get_entries(mapping, index,
367                                            PAGEVEC_SIZE, pvec.pages, indices);
368                 if (!pvec.nr)
369                         break;
370                 index = indices[pvec.nr - 1] + 1;
371                 pagevec_remove_exceptionals(&pvec);
372                 check_move_unevictable_pages(pvec.pages, pvec.nr);
373                 pagevec_release(&pvec);
374                 cond_resched();
375         }
376 }
377 
378 /*
379  * Remove range of pages and swap entries from radix tree, and free them.
380  * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.
381  */
382 static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
383                                                                  bool unfalloc)
384 {
385         struct address_space *mapping = inode->i_mapping;
386         struct shmem_inode_info *info = SHMEM_I(inode);
387         pgoff_t start = (lstart + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
388         pgoff_t end = (lend + 1) >> PAGE_CACHE_SHIFT;
389         unsigned int partial_start = lstart & (PAGE_CACHE_SIZE - 1);
390         unsigned int partial_end = (lend + 1) & (PAGE_CACHE_SIZE - 1);
391         struct pagevec pvec;
392         pgoff_t indices[PAGEVEC_SIZE];
393         long nr_swaps_freed = 0;
394         pgoff_t index;
395         int i;
396 
397         if (lend == -1)
398                 end = -1;       /* unsigned, so actually very big */
399 
400         pagevec_init(&pvec, 0);
401         index = start;
402         while (index < end) {
403                 pvec.nr = find_get_entries(mapping, index,
404                         min(end - index, (pgoff_t)PAGEVEC_SIZE),
405                         pvec.pages, indices);
406                 if (!pvec.nr)
407                         break;
408                 mem_cgroup_uncharge_start();
409                 for (i = 0; i < pagevec_count(&pvec); i++) {
410                         struct page *page = pvec.pages[i];
411 
412                         index = indices[i];
413                         if (index >= end)
414                                 break;
415 
416                         if (radix_tree_exceptional_entry(page)) {
417                                 if (unfalloc)
418                                         continue;
419                                 nr_swaps_freed += !shmem_free_swap(mapping,
420                                                                 index, page);
421                                 continue;
422                         }
423 
424                         if (!trylock_page(page))
425                                 continue;
426                         if (!unfalloc || !PageUptodate(page)) {
427                                 if (page->mapping == mapping) {
428                                         VM_BUG_ON_PAGE(PageWriteback(page), page);
429                                         truncate_inode_page(mapping, page);
430                                 }
431                         }
432                         unlock_page(page);
433                 }
434                 pagevec_remove_exceptionals(&pvec);
435                 pagevec_release(&pvec);
436                 mem_cgroup_uncharge_end();
437                 cond_resched();
438                 index++;
439         }
440 
441         if (partial_start) {
442                 struct page *page = NULL;
443                 shmem_getpage(inode, start - 1, &page, SGP_READ, NULL);
444                 if (page) {
445                         unsigned int top = PAGE_CACHE_SIZE;
446                         if (start > end) {
447                                 top = partial_end;
448                                 partial_end = 0;
449                         }
450                         zero_user_segment(page, partial_start, top);
451                         set_page_dirty(page);
452                         unlock_page(page);
453                         page_cache_release(page);
454                 }
455         }
456         if (partial_end) {
457                 struct page *page = NULL;
458                 shmem_getpage(inode, end, &page, SGP_READ, NULL);
459                 if (page) {
460                         zero_user_segment(page, 0, partial_end);
461                         set_page_dirty(page);
462                         unlock_page(page);
463                         page_cache_release(page);
464                 }
465         }
466         if (start >= end)
467                 return;
468 
469         index = start;
470         for ( ; ; ) {
471                 cond_resched();
472 
473                 pvec.nr = find_get_entries(mapping, index,
474                                 min(end - index, (pgoff_t)PAGEVEC_SIZE),
475                                 pvec.pages, indices);
476                 if (!pvec.nr) {
477                         if (index == start || unfalloc)
478                                 break;
479                         index = start;
480                         continue;
481                 }
482                 if ((index == start || unfalloc) && indices[0] >= end) {
483                         pagevec_remove_exceptionals(&pvec);
484                         pagevec_release(&pvec);
485                         break;
486                 }
487                 mem_cgroup_uncharge_start();
488                 for (i = 0; i < pagevec_count(&pvec); i++) {
489                         struct page *page = pvec.pages[i];
490 
491                         index = indices[i];
492                         if (index >= end)
493                                 break;
494 
495                         if (radix_tree_exceptional_entry(page)) {
496                                 if (unfalloc)
497                                         continue;
498                                 nr_swaps_freed += !shmem_free_swap(mapping,
499                                                                 index, page);
500                                 continue;
501                         }
502 
503                         lock_page(page);
504                         if (!unfalloc || !PageUptodate(page)) {
505                                 if (page->mapping == mapping) {
506                                         VM_BUG_ON_PAGE(PageWriteback(page), page);
507                                         truncate_inode_page(mapping, page);
508                                 }
509                         }
510                         unlock_page(page);
511                 }
512                 pagevec_remove_exceptionals(&pvec);
513                 pagevec_release(&pvec);
514                 mem_cgroup_uncharge_end();
515                 index++;
516         }
517 
518         spin_lock(&info->lock);
519         info->swapped -= nr_swaps_freed;
520         shmem_recalc_inode(inode);
521         spin_unlock(&info->lock);
522 }
523 
524 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
525 {
526         shmem_undo_range(inode, lstart, lend, false);
527         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
528 }
529 EXPORT_SYMBOL_GPL(shmem_truncate_range);
530 
531 static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
532 {
533         struct inode *inode = dentry->d_inode;
534         int error;
535 
536         error = inode_change_ok(inode, attr);
537         if (error)
538                 return error;
539 
540         if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
541                 loff_t oldsize = inode->i_size;
542                 loff_t newsize = attr->ia_size;
543 
544                 if (newsize != oldsize) {
545                         i_size_write(inode, newsize);
546                         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
547                 }
548                 if (newsize < oldsize) {
549                         loff_t holebegin = round_up(newsize, PAGE_SIZE);
550                         unmap_mapping_range(inode->i_mapping, holebegin, 0, 1);
551                         shmem_truncate_range(inode, newsize, (loff_t)-1);
552                         /* unmap again to remove racily COWed private pages */
553                         unmap_mapping_range(inode->i_mapping, holebegin, 0, 1);
554                 }
555         }
556 
557         setattr_copy(inode, attr);
558         if (attr->ia_valid & ATTR_MODE)
559                 error = posix_acl_chmod(inode, inode->i_mode);
560         return error;
561 }
562 
563 static void shmem_evict_inode(struct inode *inode)
564 {
565         struct shmem_inode_info *info = SHMEM_I(inode);
566 
567         if (inode->i_mapping->a_ops == &shmem_aops) {
568                 shmem_unacct_size(info->flags, inode->i_size);
569                 inode->i_size = 0;
570                 shmem_truncate_range(inode, 0, (loff_t)-1);
571                 if (!list_empty(&info->swaplist)) {
572                         mutex_lock(&shmem_swaplist_mutex);
573                         list_del_init(&info->swaplist);
574                         mutex_unlock(&shmem_swaplist_mutex);
575                 }
576         } else
577                 kfree(info->symlink);
578 
579         simple_xattrs_free(&info->xattrs);
580         WARN_ON(inode->i_blocks);
581         shmem_free_inode(inode->i_sb);
582         clear_inode(inode);
583 }
584 
585 /*
586  * If swap found in inode, free it and move page from swapcache to filecache.
587  */
588 static int shmem_unuse_inode(struct shmem_inode_info *info,
589                              swp_entry_t swap, struct page **pagep)
590 {
591         struct address_space *mapping = info->vfs_inode.i_mapping;
592         void *radswap;
593         pgoff_t index;
594         gfp_t gfp;
595         int error = 0;
596 
597         radswap = swp_to_radix_entry(swap);
598         index = radix_tree_locate_item(&mapping->page_tree, radswap);
599         if (index == -1)
600                 return 0;
601 
602         /*
603          * Move _head_ to start search for next from here.
604          * But be careful: shmem_evict_inode checks list_empty without taking
605          * mutex, and there's an instant in list_move_tail when info->swaplist
606          * would appear empty, if it were the only one on shmem_swaplist.
607          */
608         if (shmem_swaplist.next != &info->swaplist)
609                 list_move_tail(&shmem_swaplist, &info->swaplist);
610 
611         gfp = mapping_gfp_mask(mapping);
612         if (shmem_should_replace_page(*pagep, gfp)) {
613                 mutex_unlock(&shmem_swaplist_mutex);
614                 error = shmem_replace_page(pagep, gfp, info, index);
615                 mutex_lock(&shmem_swaplist_mutex);
616                 /*
617                  * We needed to drop mutex to make that restrictive page
618                  * allocation, but the inode might have been freed while we
619                  * dropped it: although a racing shmem_evict_inode() cannot
620                  * complete without emptying the radix_tree, our page lock
621                  * on this swapcache page is not enough to prevent that -
622                  * free_swap_and_cache() of our swap entry will only
623                  * trylock_page(), removing swap from radix_tree whatever.
624                  *
625                  * We must not proceed to shmem_add_to_page_cache() if the
626                  * inode has been freed, but of course we cannot rely on
627                  * inode or mapping or info to check that.  However, we can
628                  * safely check if our swap entry is still in use (and here
629                  * it can't have got reused for another page): if it's still
630                  * in use, then the inode cannot have been freed yet, and we
631                  * can safely proceed (if it's no longer in use, that tells
632                  * nothing about the inode, but we don't need to unuse swap).
633                  */
634                 if (!page_swapcount(*pagep))
635                         error = -ENOENT;
636         }
637 
638         /*
639          * We rely on shmem_swaplist_mutex, not only to protect the swaplist,
640          * but also to hold up shmem_evict_inode(): so inode cannot be freed
641          * beneath us (pagelock doesn't help until the page is in pagecache).
642          */
643         if (!error)
644                 error = shmem_add_to_page_cache(*pagep, mapping, index,
645                                                 GFP_NOWAIT, radswap);
646         if (error != -ENOMEM) {
647                 /*
648                  * Truncation and eviction use free_swap_and_cache(), which
649                  * only does trylock page: if we raced, best clean up here.
650                  */
651                 delete_from_swap_cache(*pagep);
652                 set_page_dirty(*pagep);
653                 if (!error) {
654                         spin_lock(&info->lock);
655                         info->swapped--;
656                         spin_unlock(&info->lock);
657                         swap_free(swap);
658                 }
659                 error = 1;      /* not an error, but entry was found */
660         }
661         return error;
662 }
663 
664 /*
665  * Search through swapped inodes to find and replace swap by page.
666  */
667 int shmem_unuse(swp_entry_t swap, struct page *page)
668 {
669         struct list_head *this, *next;
670         struct shmem_inode_info *info;
671         int found = 0;
672         int error = 0;
673 
674         /*
675          * There's a faint possibility that swap page was replaced before
676          * caller locked it: caller will come back later with the right page.
677          */
678         if (unlikely(!PageSwapCache(page) || page_private(page) != swap.val))
679                 goto out;
680 
681         /*
682          * Charge page using GFP_KERNEL while we can wait, before taking
683          * the shmem_swaplist_mutex which might hold up shmem_writepage().
684          * Charged back to the user (not to caller) when swap account is used.
685          */
686         error = mem_cgroup_charge_file(page, current->mm, GFP_KERNEL);
687         if (error)
688                 goto out;
689         /* No radix_tree_preload: swap entry keeps a place for page in tree */
690 
691         mutex_lock(&shmem_swaplist_mutex);
692         list_for_each_safe(this, next, &shmem_swaplist) {
693                 info = list_entry(this, struct shmem_inode_info, swaplist);
694                 if (info->swapped)
695                         found = shmem_unuse_inode(info, swap, &page);
696                 else
697                         list_del_init(&info->swaplist);
698                 cond_resched();
699                 if (found)
700                         break;
701         }
702         mutex_unlock(&shmem_swaplist_mutex);
703 
704         if (found < 0)
705                 error = found;
706 out:
707         unlock_page(page);
708         page_cache_release(page);
709         return error;
710 }
711 
712 /*
713  * Move the page from the page cache to the swap cache.
714  */
715 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
716 {
717         struct shmem_inode_info *info;
718         struct address_space *mapping;
719         struct inode *inode;
720         swp_entry_t swap;
721         pgoff_t index;
722 
723         BUG_ON(!PageLocked(page));
724         mapping = page->mapping;
725         index = page->index;
726         inode = mapping->host;
727         info = SHMEM_I(inode);
728         if (info->flags & VM_LOCKED)
729                 goto redirty;
730         if (!total_swap_pages)
731                 goto redirty;
732 
733         /*
734          * shmem_backing_dev_info's capabilities prevent regular writeback or
735          * sync from ever calling shmem_writepage; but a stacking filesystem
736          * might use ->writepage of its underlying filesystem, in which case
737          * tmpfs should write out to swap only in response to memory pressure,
738          * and not for the writeback threads or sync.
739          */
740         if (!wbc->for_reclaim) {
741                 WARN_ON_ONCE(1);        /* Still happens? Tell us about it! */
742                 goto redirty;
743         }
744 
745         /*
746          * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC
747          * value into swapfile.c, the only way we can correctly account for a
748          * fallocated page arriving here is now to initialize it and write it.
749          *
750          * That's okay for a page already fallocated earlier, but if we have
751          * not yet completed the fallocation, then (a) we want to keep track
752          * of this page in case we have to undo it, and (b) it may not be a
753          * good idea to continue anyway, once we're pushing into swap.  So
754          * reactivate the page, and let shmem_fallocate() quit when too many.
755          */
756         if (!PageUptodate(page)) {
757                 if (inode->i_private) {
758                         struct shmem_falloc *shmem_falloc;
759                         spin_lock(&inode->i_lock);
760                         shmem_falloc = inode->i_private;
761                         if (shmem_falloc &&
762                             index >= shmem_falloc->start &&
763                             index < shmem_falloc->next)
764                                 shmem_falloc->nr_unswapped++;
765                         else
766                                 shmem_falloc = NULL;
767                         spin_unlock(&inode->i_lock);
768                         if (shmem_falloc)
769                                 goto redirty;
770                 }
771                 clear_highpage(page);
772                 flush_dcache_page(page);
773                 SetPageUptodate(page);
774         }
775 
776         swap = get_swap_page();
777         if (!swap.val)
778                 goto redirty;
779 
780         /*
781          * Add inode to shmem_unuse()'s list of swapped-out inodes,
782          * if it's not already there.  Do it now before the page is
783          * moved to swap cache, when its pagelock no longer protects
784          * the inode from eviction.  But don't unlock the mutex until
785          * we've incremented swapped, because shmem_unuse_inode() will
786          * prune a !swapped inode from the swaplist under this mutex.
787          */
788         mutex_lock(&shmem_swaplist_mutex);
789         if (list_empty(&info->swaplist))
790                 list_add_tail(&info->swaplist, &shmem_swaplist);
791 
792         if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
793                 swap_shmem_alloc(swap);
794                 shmem_delete_from_page_cache(page, swp_to_radix_entry(swap));
795 
796                 spin_lock(&info->lock);
797                 info->swapped++;
798                 shmem_recalc_inode(inode);
799                 spin_unlock(&info->lock);
800 
801                 mutex_unlock(&shmem_swaplist_mutex);
802                 BUG_ON(page_mapped(page));
803                 swap_writepage(page, wbc);
804                 return 0;
805         }
806 
807         mutex_unlock(&shmem_swaplist_mutex);
808         swapcache_free(swap, NULL);
809 redirty:
810         set_page_dirty(page);
811         if (wbc->for_reclaim)
812                 return AOP_WRITEPAGE_ACTIVATE;  /* Return with page locked */
813         unlock_page(page);
814         return 0;
815 }
816 
817 #ifdef CONFIG_NUMA
818 #ifdef CONFIG_TMPFS
819 static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
820 {
821         char buffer[64];
822 
823         if (!mpol || mpol->mode == MPOL_DEFAULT)
824                 return;         /* show nothing */
825 
826         mpol_to_str(buffer, sizeof(buffer), mpol);
827 
828         seq_printf(seq, ",mpol=%s", buffer);
829 }
830 
831 static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
832 {
833         struct mempolicy *mpol = NULL;
834         if (sbinfo->mpol) {
835                 spin_lock(&sbinfo->stat_lock);  /* prevent replace/use races */
836                 mpol = sbinfo->mpol;
837                 mpol_get(mpol);
838                 spin_unlock(&sbinfo->stat_lock);
839         }
840         return mpol;
841 }
842 #endif /* CONFIG_TMPFS */
843 
844 static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
845                         struct shmem_inode_info *info, pgoff_t index)
846 {
847         struct vm_area_struct pvma;
848         struct page *page;
849 
850         /* Create a pseudo vma that just contains the policy */
851         pvma.vm_start = 0;
852         /* Bias interleave by inode number to distribute better across nodes */
853         pvma.vm_pgoff = index + info->vfs_inode.i_ino;
854         pvma.vm_ops = NULL;
855         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
856 
857         page = swapin_readahead(swap, gfp, &pvma, 0);
858 
859         /* Drop reference taken by mpol_shared_policy_lookup() */
860         mpol_cond_put(pvma.vm_policy);
861 
862         return page;
863 }
864 
865 static struct page *shmem_alloc_page(gfp_t gfp,
866                         struct shmem_inode_info *info, pgoff_t index)
867 {
868         struct vm_area_struct pvma;
869         struct page *page;
870 
871         /* Create a pseudo vma that just contains the policy */
872         pvma.vm_start = 0;
873         /* Bias interleave by inode number to distribute better across nodes */
874         pvma.vm_pgoff = index + info->vfs_inode.i_ino;
875         pvma.vm_ops = NULL;
876         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
877 
878         page = alloc_page_vma(gfp, &pvma, 0);
879 
880         /* Drop reference taken by mpol_shared_policy_lookup() */
881         mpol_cond_put(pvma.vm_policy);
882 
883         return page;
884 }
885 #else /* !CONFIG_NUMA */
886 #ifdef CONFIG_TMPFS
887 static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
888 {
889 }
890 #endif /* CONFIG_TMPFS */
891 
892 static inline struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
893                         struct shmem_inode_info *info, pgoff_t index)
894 {
895         return swapin_readahead(swap, gfp, NULL, 0);
896 }
897 
898 static inline struct page *shmem_alloc_page(gfp_t gfp,
899                         struct shmem_inode_info *info, pgoff_t index)
900 {
901         return alloc_page(gfp);
902 }
903 #endif /* CONFIG_NUMA */
904 
905 #if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS)
906 static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
907 {
908         return NULL;
909 }
910 #endif
911 
912 /*
913  * When a page is moved from swapcache to shmem filecache (either by the
914  * usual swapin of shmem_getpage_gfp(), or by the less common swapoff of
915  * shmem_unuse_inode()), it may have been read in earlier from swap, in
916  * ignorance of the mapping it belongs to.  If that mapping has special
917  * constraints (like the gma500 GEM driver, which requires RAM below 4GB),
918  * we may need to copy to a suitable page before moving to filecache.
919  *
920  * In a future release, this may well be extended to respect cpuset and
921  * NUMA mempolicy, and applied also to anonymous pages in do_swap_page();
922  * but for now it is a simple matter of zone.
923  */
924 static bool shmem_should_replace_page(struct page *page, gfp_t gfp)
925 {
926         return page_zonenum(page) > gfp_zone(gfp);
927 }
928 
929 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
930                                 struct shmem_inode_info *info, pgoff_t index)
931 {
932         struct page *oldpage, *newpage;
933         struct address_space *swap_mapping;
934         pgoff_t swap_index;
935         int error;
936 
937         oldpage = *pagep;
938         swap_index = page_private(oldpage);
939         swap_mapping = page_mapping(oldpage);
940 
941         /*
942          * We have arrived here because our zones are constrained, so don't
943          * limit chance of success by further cpuset and node constraints.
944          */
945         gfp &= ~GFP_CONSTRAINT_MASK;
946         newpage = shmem_alloc_page(gfp, info, index);
947         if (!newpage)
948                 return -ENOMEM;
949 
950         page_cache_get(newpage);
951         copy_highpage(newpage, oldpage);
952         flush_dcache_page(newpage);
953 
954         __set_page_locked(newpage);
955         SetPageUptodate(newpage);
956         SetPageSwapBacked(newpage);
957         set_page_private(newpage, swap_index);
958         SetPageSwapCache(newpage);
959 
960         /*
961          * Our caller will very soon move newpage out of swapcache, but it's
962          * a nice clean interface for us to replace oldpage by newpage there.
963          */
964         spin_lock_irq(&swap_mapping->tree_lock);
965         error = shmem_radix_tree_replace(swap_mapping, swap_index, oldpage,
966                                                                    newpage);
967         if (!error) {
968                 __inc_zone_page_state(newpage, NR_FILE_PAGES);
969                 __dec_zone_page_state(oldpage, NR_FILE_PAGES);
970         }
971         spin_unlock_irq(&swap_mapping->tree_lock);
972 
973         if (unlikely(error)) {
974                 /*
975                  * Is this possible?  I think not, now that our callers check
976                  * both PageSwapCache and page_private after getting page lock;
977                  * but be defensive.  Reverse old to newpage for clear and free.
978                  */
979                 oldpage = newpage;
980         } else {
981                 mem_cgroup_replace_page_cache(oldpage, newpage);
982                 lru_cache_add_anon(newpage);
983                 *pagep = newpage;
984         }
985 
986         ClearPageSwapCache(oldpage);
987         set_page_private(oldpage, 0);
988 
989         unlock_page(oldpage);
990         page_cache_release(oldpage);
991         page_cache_release(oldpage);
992         return error;
993 }
994 
995 /*
996  * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
997  *
998  * If we allocate a new one we do not mark it dirty. That's up to the
999  * vm. If we swap it in we mark it dirty since we also free the swap
1000  * entry since a page cannot live in both the swap and page cache
1001  */
1002 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
1003         struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type)
1004 {
1005         struct address_space *mapping = inode->i_mapping;
1006         struct shmem_inode_info *info;
1007         struct shmem_sb_info *sbinfo;
1008         struct page *page;
1009         swp_entry_t swap;
1010         int error;
1011         int once = 0;
1012         int alloced = 0;
1013 
1014         if (index > (MAX_LFS_FILESIZE >> PAGE_CACHE_SHIFT))
1015                 return -EFBIG;
1016 repeat:
1017         swap.val = 0;
1018         page = find_lock_entry(mapping, index);
1019         if (radix_tree_exceptional_entry(page)) {
1020                 swap = radix_to_swp_entry(page);
1021                 page = NULL;
1022         }
1023 
1024         if (sgp != SGP_WRITE && sgp != SGP_FALLOC &&
1025             ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
1026                 error = -EINVAL;
1027                 goto failed;
1028         }
1029 
1030         /* fallocated page? */
1031         if (page && !PageUptodate(page)) {
1032                 if (sgp != SGP_READ)
1033                         goto clear;
1034                 unlock_page(page);
1035                 page_cache_release(page);
1036                 page = NULL;
1037         }
1038         if (page || (sgp == SGP_READ && !swap.val)) {
1039                 *pagep = page;
1040                 return 0;
1041         }
1042 
1043         /*
1044          * Fast cache lookup did not find it:
1045          * bring it back from swap or allocate.
1046          */
1047         info = SHMEM_I(inode);
1048         sbinfo = SHMEM_SB(inode->i_sb);
1049 
1050         if (swap.val) {
1051                 /* Look it up and read it in.. */
1052                 page = lookup_swap_cache(swap);
1053                 if (!page) {
1054                         /* here we actually do the io */
1055                         if (fault_type)
1056                                 *fault_type |= VM_FAULT_MAJOR;
1057                         page = shmem_swapin(swap, gfp, info, index);
1058                         if (!page) {
1059                                 error = -ENOMEM;
1060                                 goto failed;
1061                         }
1062                 }
1063 
1064                 /* We have to do this with page locked to prevent races */
1065                 lock_page(page);
1066                 if (!PageSwapCache(page) || page_private(page) != swap.val ||
1067                     !shmem_confirm_swap(mapping, index, swap)) {
1068                         error = -EEXIST;        /* try again */
1069                         goto unlock;
1070                 }
1071                 if (!PageUptodate(page)) {
1072                         error = -EIO;
1073                         goto failed;
1074                 }
1075                 wait_on_page_writeback(page);
1076 
1077                 if (shmem_should_replace_page(page, gfp)) {
1078                         error = shmem_replace_page(&page, gfp, info, index);
1079                         if (error)
1080                                 goto failed;
1081                 }
1082 
1083                 error = mem_cgroup_charge_file(page, current->mm,
1084                                                 gfp & GFP_RECLAIM_MASK);
1085                 if (!error) {
1086                         error = shmem_add_to_page_cache(page, mapping, index,
1087                                                 gfp, swp_to_radix_entry(swap));
1088                         /*
1089                          * We already confirmed swap under page lock, and make
1090                          * no memory allocation here, so usually no possibility
1091                          * of error; but free_swap_and_cache() only trylocks a
1092                          * page, so it is just possible that the entry has been
1093                          * truncated or holepunched since swap was confirmed.
1094                          * shmem_undo_range() will have done some of the
1095                          * unaccounting, now delete_from_swap_cache() will do
1096                          * the rest (including mem_cgroup_uncharge_swapcache).
1097                          * Reset swap.val? No, leave it so "failed" goes back to
1098                          * "repeat": reading a hole and writing should succeed.
1099                          */
1100                         if (error)
1101                                 delete_from_swap_cache(page);
1102                 }
1103                 if (error)
1104                         goto failed;
1105 
1106                 spin_lock(&info->lock);
1107                 info->swapped--;
1108                 shmem_recalc_inode(inode);
1109                 spin_unlock(&info->lock);
1110 
1111                 delete_from_swap_cache(page);
1112                 set_page_dirty(page);
1113                 swap_free(swap);
1114 
1115         } else {
1116                 if (shmem_acct_block(info->flags)) {
1117                         error = -ENOSPC;
1118                         goto failed;
1119                 }
1120                 if (sbinfo->max_blocks) {
1121                         if (percpu_counter_compare(&sbinfo->used_blocks,
1122                                                 sbinfo->max_blocks) >= 0) {
1123                                 error = -ENOSPC;
1124                                 goto unacct;
1125                         }
1126                         percpu_counter_inc(&sbinfo->used_blocks);
1127                 }
1128 
1129                 page = shmem_alloc_page(gfp, info, index);
1130                 if (!page) {
1131                         error = -ENOMEM;
1132                         goto decused;
1133                 }
1134 
1135                 SetPageSwapBacked(page);
1136                 __set_page_locked(page);
1137                 error = mem_cgroup_charge_file(page, current->mm,
1138                                                 gfp & GFP_RECLAIM_MASK);
1139                 if (error)
1140                         goto decused;
1141                 error = radix_tree_maybe_preload(gfp & GFP_RECLAIM_MASK);
1142                 if (!error) {
1143                         error = shmem_add_to_page_cache(page, mapping, index,
1144                                                         gfp, NULL);
1145                         radix_tree_preload_end();
1146                 }
1147                 if (error) {
1148                         mem_cgroup_uncharge_cache_page(page);
1149                         goto decused;
1150                 }
1151                 lru_cache_add_anon(page);
1152 
1153                 spin_lock(&info->lock);
1154                 info->alloced++;
1155                 inode->i_blocks += BLOCKS_PER_PAGE;
1156                 shmem_recalc_inode(inode);
1157                 spin_unlock(&info->lock);
1158                 alloced = true;
1159 
1160                 /*
1161                  * Let SGP_FALLOC use the SGP_WRITE optimization on a new page.
1162                  */
1163                 if (sgp == SGP_FALLOC)
1164                         sgp = SGP_WRITE;
1165 clear:
1166                 /*
1167                  * Let SGP_WRITE caller clear ends if write does not fill page;
1168                  * but SGP_FALLOC on a page fallocated earlier must initialize
1169                  * it now, lest undo on failure cancel our earlier guarantee.
1170                  */
1171                 if (sgp != SGP_WRITE) {
1172                         clear_highpage(page);
1173                         flush_dcache_page(page);
1174                         SetPageUptodate(page);
1175                 }
1176                 if (sgp == SGP_DIRTY)
1177                         set_page_dirty(page);
1178         }
1179 
1180         /* Perhaps the file has been truncated since we checked */
1181         if (sgp != SGP_WRITE && sgp != SGP_FALLOC &&
1182             ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
1183                 error = -EINVAL;
1184                 if (alloced)
1185                         goto trunc;
1186                 else
1187                         goto failed;
1188         }
1189         *pagep = page;
1190         return 0;
1191 
1192         /*
1193          * Error recovery.
1194          */
1195 trunc:
1196         info = SHMEM_I(inode);
1197         ClearPageDirty(page);
1198         delete_from_page_cache(page);
1199         spin_lock(&info->lock);
1200         info->alloced--;
1201         inode->i_blocks -= BLOCKS_PER_PAGE;
1202         spin_unlock(&info->lock);
1203 decused:
1204         sbinfo = SHMEM_SB(inode->i_sb);
1205         if (sbinfo->max_blocks)
1206                 percpu_counter_add(&sbinfo->used_blocks, -1);
1207 unacct:
1208         shmem_unacct_blocks(info->flags, 1);
1209 failed:
1210         if (swap.val && error != -EINVAL &&
1211             !shmem_confirm_swap(mapping, index, swap))
1212                 error = -EEXIST;
1213 unlock:
1214         if (page) {
1215                 unlock_page(page);
1216                 page_cache_release(page);
1217         }
1218         if (error == -ENOSPC && !once++) {
1219                 info = SHMEM_I(inode);
1220                 spin_lock(&info->lock);
1221                 shmem_recalc_inode(inode);
1222                 spin_unlock(&info->lock);
1223                 goto repeat;
1224         }
1225         if (error == -EEXIST)   /* from above or from radix_tree_insert */
1226                 goto repeat;
1227         return error;
1228 }
1229 
1230 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1231 {
1232         struct inode *inode = file_inode(vma->vm_file);
1233         int error;
1234         int ret = VM_FAULT_LOCKED;
1235 
1236         error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
1237         if (error)
1238                 return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1239 
1240         if (ret & VM_FAULT_MAJOR) {
1241                 count_vm_event(PGMAJFAULT);
1242                 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1243         }
1244         return ret;
1245 }
1246 
1247 #ifdef CONFIG_NUMA
1248 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol)
1249 {
1250         struct inode *inode = file_inode(vma->vm_file);
1251         return mpol_set_shared_policy(&SHMEM_I(inode)->policy, vma, mpol);
1252 }
1253 
1254 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
1255                                           unsigned long addr)
1256 {
1257         struct inode *inode = file_inode(vma->vm_file);
1258         pgoff_t index;
1259 
1260         index = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1261         return mpol_shared_policy_lookup(&SHMEM_I(inode)->policy, index);
1262 }
1263 #endif
1264 
1265 int shmem_lock(struct file *file, int lock, struct user_struct *user)
1266 {
1267         struct inode *inode = file_inode(file);
1268         struct shmem_inode_info *info = SHMEM_I(inode);
1269         int retval = -ENOMEM;
1270 
1271         spin_lock(&info->lock);
1272         if (lock && !(info->flags & VM_LOCKED)) {
1273                 if (!user_shm_lock(inode->i_size, user))
1274                         goto out_nomem;
1275                 info->flags |= VM_LOCKED;
1276                 mapping_set_unevictable(file->f_mapping);
1277         }
1278         if (!lock && (info->flags & VM_LOCKED) && user) {
1279                 user_shm_unlock(inode->i_size, user);
1280                 info->flags &= ~VM_LOCKED;
1281                 mapping_clear_unevictable(file->f_mapping);
1282         }
1283         retval = 0;
1284 
1285 out_nomem:
1286         spin_unlock(&info->lock);
1287         return retval;
1288 }
1289 
1290 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1291 {
1292         file_accessed(file);
1293         vma->vm_ops = &shmem_vm_ops;
1294         return 0;
1295 }
1296 
1297 static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
1298                                      umode_t mode, dev_t dev, unsigned long flags)
1299 {
1300         struct inode *inode;
1301         struct shmem_inode_info *info;
1302         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1303 
1304         if (shmem_reserve_inode(sb))
1305                 return NULL;
1306 
1307         inode = new_inode(sb);
1308         if (inode) {
1309                 inode->i_ino = get_next_ino();
1310                 inode_init_owner(inode, dir, mode);
1311                 inode->i_blocks = 0;
1312                 inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1313                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1314                 inode->i_generation = get_seconds();
1315                 info = SHMEM_I(inode);
1316                 memset(info, 0, (char *)inode - (char *)info);
1317                 spin_lock_init(&info->lock);
1318                 info->flags = flags & VM_NORESERVE;
1319                 INIT_LIST_HEAD(&info->swaplist);
1320                 simple_xattrs_init(&info->xattrs);
1321                 cache_no_acl(inode);
1322 
1323                 switch (mode & S_IFMT) {
1324                 default:
1325                         inode->i_op = &shmem_special_inode_operations;
1326                         init_special_inode(inode, mode, dev);
1327                         break;
1328                 case S_IFREG:
1329                         inode->i_mapping->a_ops = &shmem_aops;
1330                         inode->i_op = &shmem_inode_operations;
1331                         inode->i_fop = &shmem_file_operations;
1332                         mpol_shared_policy_init(&info->policy,
1333                                                  shmem_get_sbmpol(sbinfo));
1334                         break;
1335                 case S_IFDIR:
1336                         inc_nlink(inode);
1337                         /* Some things misbehave if size == 0 on a directory */
1338                         inode->i_size = 2 * BOGO_DIRENT_SIZE;
1339                         inode->i_op = &shmem_dir_inode_operations;
1340                         inode->i_fop = &simple_dir_operations;
1341                         break;
1342                 case S_IFLNK:
1343                         /*
1344                          * Must not load anything in the rbtree,
1345                          * mpol_free_shared_policy will not be called.
1346                          */
1347                         mpol_shared_policy_init(&info->policy, NULL);
1348                         break;
1349                 }
1350         } else
1351                 shmem_free_inode(sb);
1352         return inode;
1353 }
1354 
1355 bool shmem_mapping(struct address_space *mapping)
1356 {
1357         return mapping->backing_dev_info == &shmem_backing_dev_info;
1358 }
1359 
1360 #ifdef CONFIG_TMPFS
1361 static const struct inode_operations shmem_symlink_inode_operations;
1362 static const struct inode_operations shmem_short_symlink_operations;
1363 
1364 #ifdef CONFIG_TMPFS_XATTR
1365 static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
1366 #else
1367 #define shmem_initxattrs NULL
1368 #endif
1369 
1370 static int
1371 shmem_write_begin(struct file *file, struct address_space *mapping,
1372                         loff_t pos, unsigned len, unsigned flags,
1373                         struct page **pagep, void **fsdata)
1374 {
1375         struct inode *inode = mapping->host;
1376         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1377         return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
1378 }
1379 
1380 static int
1381 shmem_write_end(struct file *file, struct address_space *mapping,
1382                         loff_t pos, unsigned len, unsigned copied,
1383                         struct page *page, void *fsdata)
1384 {
1385         struct inode *inode = mapping->host;
1386 
1387         if (pos + copied > inode->i_size)
1388                 i_size_write(inode, pos + copied);
1389 
1390         if (!PageUptodate(page)) {
1391                 if (copied < PAGE_CACHE_SIZE) {
1392                         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
1393                         zero_user_segments(page, 0, from,
1394                                         from + copied, PAGE_CACHE_SIZE);
1395                 }
1396                 SetPageUptodate(page);
1397         }
1398         set_page_dirty(page);
1399         unlock_page(page);
1400         page_cache_release(page);
1401 
1402         return copied;
1403 }
1404 
1405 static ssize_t shmem_file_aio_read(struct kiocb *iocb,
1406                 const struct iovec *iov, unsigned long nr_segs, loff_t pos)
1407 {
1408         struct file *file = iocb->ki_filp;
1409         struct inode *inode = file_inode(file);
1410         struct address_space *mapping = inode->i_mapping;
1411         pgoff_t index;
1412         unsigned long offset;
1413         enum sgp_type sgp = SGP_READ;
1414         int error = 0;
1415         ssize_t retval;
1416         size_t count;
1417         loff_t *ppos = &iocb->ki_pos;
1418         struct iov_iter iter;
1419 
1420         retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1421         if (retval)
1422                 return retval;
1423         iov_iter_init(&iter, iov, nr_segs, count, 0);
1424 
1425         /*
1426          * Might this read be for a stacking filesystem?  Then when reading
1427          * holes of a sparse file, we actually need to allocate those pages,
1428          * and even mark them dirty, so it cannot exceed the max_blocks limit.
1429          */
1430         if (segment_eq(get_fs(), KERNEL_DS))
1431                 sgp = SGP_DIRTY;
1432 
1433         index = *ppos >> PAGE_CACHE_SHIFT;
1434         offset = *ppos & ~PAGE_CACHE_MASK;
1435 
1436         for (;;) {
1437                 struct page *page = NULL;
1438                 pgoff_t end_index;
1439                 unsigned long nr, ret;
1440                 loff_t i_size = i_size_read(inode);
1441 
1442                 end_index = i_size >> PAGE_CACHE_SHIFT;
1443                 if (index > end_index)
1444                         break;
1445                 if (index == end_index) {
1446                         nr = i_size & ~PAGE_CACHE_MASK;
1447                         if (nr <= offset)
1448                                 break;
1449                 }
1450 
1451                 error = shmem_getpage(inode, index, &page, sgp, NULL);
1452                 if (error) {
1453                         if (error == -EINVAL)
1454                                 error = 0;
1455                         break;
1456                 }
1457                 if (page)
1458                         unlock_page(page);
1459 
1460                 /*
1461                  * We must evaluate after, since reads (unlike writes)
1462                  * are called without i_mutex protection against truncate
1463                  */
1464                 nr = PAGE_CACHE_SIZE;
1465                 i_size = i_size_read(inode);
1466                 end_index = i_size >> PAGE_CACHE_SHIFT;
1467                 if (index == end_index) {
1468                         nr = i_size & ~PAGE_CACHE_MASK;
1469                         if (nr <= offset) {
1470                                 if (page)
1471                                         page_cache_release(page);
1472                                 break;
1473                         }
1474                 }
1475                 nr -= offset;
1476 
1477                 if (page) {
1478                         /*
1479                          * If users can be writing to this page using arbitrary
1480                          * virtual addresses, take care about potential aliasing
1481                          * before reading the page on the kernel side.
1482                          */
1483                         if (mapping_writably_mapped(mapping))
1484                                 flush_dcache_page(page);
1485                         /*
1486                          * Mark the page accessed if we read the beginning.
1487                          */
1488                         if (!offset)
1489                                 mark_page_accessed(page);
1490                 } else {
1491                         page = ZERO_PAGE(0);
1492                         page_cache_get(page);
1493                 }
1494 
1495                 /*
1496                  * Ok, we have the page, and it's up-to-date, so
1497                  * now we can copy it to user space...
1498                  */
1499                 ret = copy_page_to_iter(page, offset, nr, &iter);
1500                 retval += ret;
1501                 offset += ret;
1502                 index += offset >> PAGE_CACHE_SHIFT;
1503                 offset &= ~PAGE_CACHE_MASK;
1504 
1505                 page_cache_release(page);
1506                 if (!iov_iter_count(&iter))
1507                         break;
1508                 if (ret < nr) {
1509                         error = -EFAULT;
1510                         break;
1511                 }
1512                 cond_resched();
1513         }
1514 
1515         *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1516         file_accessed(file);
1517         return retval ? retval : error;
1518 }
1519 
1520 static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
1521                                 struct pipe_inode_info *pipe, size_t len,
1522                                 unsigned int flags)
1523 {
1524         struct address_space *mapping = in->f_mapping;
1525         struct inode *inode = mapping->host;
1526         unsigned int loff, nr_pages, req_pages;
1527         struct page *pages[PIPE_DEF_BUFFERS];
1528         struct partial_page partial[PIPE_DEF_BUFFERS];
1529         struct page *page;
1530         pgoff_t index, end_index;
1531         loff_t isize, left;
1532         int error, page_nr;
1533         struct splice_pipe_desc spd = {
1534                 .pages = pages,
1535                 .partial = partial,
1536                 .nr_pages_max = PIPE_DEF_BUFFERS,
1537                 .flags = flags,
1538                 .ops = &page_cache_pipe_buf_ops,
1539                 .spd_release = spd_release_page,
1540         };
1541 
1542         isize = i_size_read(inode);
1543         if (unlikely(*ppos >= isize))
1544                 return 0;
1545 
1546         left = isize - *ppos;
1547         if (unlikely(left < len))
1548                 len = left;
1549 
1550         if (splice_grow_spd(pipe, &spd))
1551                 return -ENOMEM;
1552 
1553         index = *ppos >> PAGE_CACHE_SHIFT;
1554         loff = *ppos & ~PAGE_CACHE_MASK;
1555         req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1556         nr_pages = min(req_pages, spd.nr_pages_max);
1557 
1558         spd.nr_pages = find_get_pages_contig(mapping, index,
1559                                                 nr_pages, spd.pages);
1560         index += spd.nr_pages;
1561         error = 0;
1562 
1563         while (spd.nr_pages < nr_pages) {
1564                 error = shmem_getpage(inode, index, &page, SGP_CACHE, NULL);
1565                 if (error)
1566                         break;
1567                 unlock_page(page);
1568                 spd.pages[spd.nr_pages++] = page;
1569                 index++;
1570         }
1571 
1572         index = *ppos >> PAGE_CACHE_SHIFT;
1573         nr_pages = spd.nr_pages;
1574         spd.nr_pages = 0;
1575 
1576         for (page_nr = 0; page_nr < nr_pages; page_nr++) {
1577                 unsigned int this_len;
1578 
1579                 if (!len)
1580                         break;
1581 
1582                 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
1583                 page = spd.pages[page_nr];
1584 
1585                 if (!PageUptodate(page) || page->mapping != mapping) {
1586                         error = shmem_getpage(inode, index, &page,
1587                                                         SGP_CACHE, NULL);
1588                         if (error)
1589                                 break;
1590                         unlock_page(page);
1591                         page_cache_release(spd.pages[page_nr]);
1592                         spd.pages[page_nr] = page;
1593                 }
1594 
1595                 isize = i_size_read(inode);
1596                 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1597                 if (unlikely(!isize || index > end_index))
1598                         break;
1599 
1600                 if (end_index == index) {
1601                         unsigned int plen;
1602 
1603                         plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1604                         if (plen <= loff)
1605                                 break;
1606 
1607                         this_len = min(this_len, plen - loff);
1608                         len = this_len;
1609                 }
1610 
1611                 spd.partial[page_nr].offset = loff;
1612                 spd.partial[page_nr].len = this_len;
1613                 len -= this_len;
1614                 loff = 0;
1615                 spd.nr_pages++;
1616                 index++;
1617         }
1618 
1619         while (page_nr < nr_pages)
1620                 page_cache_release(spd.pages[page_nr++]);
1621 
1622         if (spd.nr_pages)
1623                 error = splice_to_pipe(pipe, &spd);
1624 
1625         splice_shrink_spd(&spd);
1626 
1627         if (error > 0) {
1628                 *ppos += error;
1629                 file_accessed(in);
1630         }
1631         return error;
1632 }
1633 
1634 /*
1635  * llseek SEEK_DATA or SEEK_HOLE through the radix_tree.
1636  */
1637 static pgoff_t shmem_seek_hole_data(struct address_space *mapping,
1638                                     pgoff_t index, pgoff_t end, int whence)
1639 {
1640         struct page *page;
1641         struct pagevec pvec;
1642         pgoff_t indices[PAGEVEC_SIZE];
1643         bool done = false;
1644         int i;
1645 
1646         pagevec_init(&pvec, 0);
1647         pvec.nr = 1;            /* start small: we may be there already */
1648         while (!done) {
1649                 pvec.nr = find_get_entries(mapping, index,
1650                                         pvec.nr, pvec.pages, indices);
1651                 if (!pvec.nr) {
1652                         if (whence == SEEK_DATA)
1653                                 index = end;
1654                         break;
1655                 }
1656                 for (i = 0; i < pvec.nr; i++, index++) {
1657                         if (index < indices[i]) {
1658                                 if (whence == SEEK_HOLE) {
1659                                         done = true;
1660                                         break;
1661                                 }
1662                                 index = indices[i];
1663                         }
1664                         page = pvec.pages[i];
1665                         if (page && !radix_tree_exceptional_entry(page)) {
1666                                 if (!PageUptodate(page))
1667                                         page = NULL;
1668                         }
1669                         if (index >= end ||
1670                             (page && whence == SEEK_DATA) ||
1671                             (!page && whence == SEEK_HOLE)) {
1672                                 done = true;
1673                                 break;
1674                         }
1675                 }
1676                 pagevec_remove_exceptionals(&pvec);
1677                 pagevec_release(&pvec);
1678                 pvec.nr = PAGEVEC_SIZE;
1679                 cond_resched();
1680         }
1681         return index;
1682 }
1683 
1684 static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence)
1685 {
1686         struct address_space *mapping = file->f_mapping;
1687         struct inode *inode = mapping->host;
1688         pgoff_t start, end;
1689         loff_t new_offset;
1690 
1691         if (whence != SEEK_DATA && whence != SEEK_HOLE)
1692                 return generic_file_llseek_size(file, offset, whence,
1693                                         MAX_LFS_FILESIZE, i_size_read(inode));
1694         mutex_lock(&inode->i_mutex);
1695         /* We're holding i_mutex so we can access i_size directly */
1696 
1697         if (offset < 0)
1698                 offset = -EINVAL;
1699         else if (offset >= inode->i_size)
1700                 offset = -ENXIO;
1701         else {
1702                 start = offset >> PAGE_CACHE_SHIFT;
1703                 end = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1704                 new_offset = shmem_seek_hole_data(mapping, start, end, whence);
1705                 new_offset <<= PAGE_CACHE_SHIFT;
1706                 if (new_offset > offset) {
1707                         if (new_offset < inode->i_size)
1708                                 offset = new_offset;
1709                         else if (whence == SEEK_DATA)
1710                                 offset = -ENXIO;
1711                         else
1712                                 offset = inode->i_size;
1713                 }
1714         }
1715 
1716         if (offset >= 0)
1717                 offset = vfs_setpos(file, offset, MAX_LFS_FILESIZE);
1718         mutex_unlock(&inode->i_mutex);
1719         return offset;
1720 }
1721 
1722 static long shmem_fallocate(struct file *file, int mode, loff_t offset,
1723                                                          loff_t len)
1724 {
1725         struct inode *inode = file_inode(file);
1726         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1727         struct shmem_falloc shmem_falloc;
1728         pgoff_t start, index, end;
1729         int error;
1730 
1731         mutex_lock(&inode->i_mutex);
1732 
1733         if (mode & FALLOC_FL_PUNCH_HOLE) {
1734                 struct address_space *mapping = file->f_mapping;
1735                 loff_t unmap_start = round_up(offset, PAGE_SIZE);
1736                 loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1;
1737 
1738                 if ((u64)unmap_end > (u64)unmap_start)
1739                         unmap_mapping_range(mapping, unmap_start,
1740                                             1 + unmap_end - unmap_start, 0);
1741                 shmem_truncate_range(inode, offset, offset + len - 1);
1742                 /* No need to unmap again: hole-punching leaves COWed pages */
1743                 error = 0;
1744                 goto out;
1745         }
1746 
1747         /* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */
1748         error = inode_newsize_ok(inode, offset + len);
1749         if (error)
1750                 goto out;
1751 
1752         start = offset >> PAGE_CACHE_SHIFT;
1753         end = (offset + len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1754         /* Try to avoid a swapstorm if len is impossible to satisfy */
1755         if (sbinfo->max_blocks && end - start > sbinfo->max_blocks) {
1756                 error = -ENOSPC;
1757                 goto out;
1758         }
1759 
1760         shmem_falloc.start = start;
1761         shmem_falloc.next  = start;
1762         shmem_falloc.nr_falloced = 0;
1763         shmem_falloc.nr_unswapped = 0;
1764         spin_lock(&inode->i_lock);
1765         inode->i_private = &shmem_falloc;
1766         spin_unlock(&inode->i_lock);
1767 
1768         for (index = start; index < end; index++) {
1769                 struct page *page;
1770 
1771                 /*
1772                  * Good, the fallocate(2) manpage permits EINTR: we may have
1773                  * been interrupted because we are using up too much memory.
1774                  */
1775                 if (signal_pending(current))
1776                         error = -EINTR;
1777                 else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
1778                         error = -ENOMEM;
1779                 else
1780                         error = shmem_getpage(inode, index, &page, SGP_FALLOC,
1781                                                                         NULL);
1782                 if (error) {
1783                         /* Remove the !PageUptodate pages we added */
1784                         shmem_undo_range(inode,
1785                                 (loff_t)start << PAGE_CACHE_SHIFT,
1786                                 (loff_t)index << PAGE_CACHE_SHIFT, true);
1787                         goto undone;
1788                 }
1789 
1790                 /*
1791                  * Inform shmem_writepage() how far we have reached.
1792                  * No need for lock or barrier: we have the page lock.
1793                  */
1794                 shmem_falloc.next++;
1795                 if (!PageUptodate(page))
1796                         shmem_falloc.nr_falloced++;
1797 
1798                 /*
1799                  * If !PageUptodate, leave it that way so that freeable pages
1800                  * can be recognized if we need to rollback on error later.
1801                  * But set_page_dirty so that memory pressure will swap rather
1802                  * than free the pages we are allocating (and SGP_CACHE pages
1803                  * might still be clean: we now need to mark those dirty too).
1804                  */
1805                 set_page_dirty(page);
1806                 unlock_page(page);
1807                 page_cache_release(page);
1808                 cond_resched();
1809         }
1810 
1811         if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
1812                 i_size_write(inode, offset + len);
1813         inode->i_ctime = CURRENT_TIME;
1814 undone:
1815         spin_lock(&inode->i_lock);
1816         inode->i_private = NULL;
1817         spin_unlock(&inode->i_lock);
1818 out:
1819         mutex_unlock(&inode->i_mutex);
1820         return error;
1821 }
1822 
1823 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1824 {
1825         struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1826 
1827         buf->f_type = TMPFS_MAGIC;
1828         buf->f_bsize = PAGE_CACHE_SIZE;
1829         buf->f_namelen = NAME_MAX;
1830         if (sbinfo->max_blocks) {
1831                 buf->f_blocks = sbinfo->max_blocks;
1832                 buf->f_bavail =
1833                 buf->f_bfree  = sbinfo->max_blocks -
1834                                 percpu_counter_sum(&sbinfo->used_blocks);
1835         }
1836         if (sbinfo->max_inodes) {
1837                 buf->f_files = sbinfo->max_inodes;
1838                 buf->f_ffree = sbinfo->free_inodes;
1839         }
1840         /* else leave those fields 0 like simple_statfs */
1841         return 0;
1842 }
1843 
1844 /*
1845  * File creation. Allocate an inode, and we're done..
1846  */
1847 static int
1848 shmem_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
1849 {
1850         struct inode *inode;
1851         int error = -ENOSPC;
1852 
1853         inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
1854         if (inode) {
1855                 error = simple_acl_create(dir, inode);
1856                 if (error)
1857                         goto out_iput;
1858                 error = security_inode_init_security(inode, dir,
1859                                                      &dentry->d_name,
1860                                                      shmem_initxattrs, NULL);
1861                 if (error && error != -EOPNOTSUPP)
1862                         goto out_iput;
1863 
1864                 error = 0;
1865                 dir->i_size += BOGO_DIRENT_SIZE;
1866                 dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1867                 d_instantiate(dentry, inode);
1868                 dget(dentry); /* Extra count - pin the dentry in core */
1869         }
1870         return error;
1871 out_iput:
1872         iput(inode);
1873         return error;
1874 }
1875 
1876 static int
1877 shmem_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
1878 {
1879         struct inode *inode;
1880         int error = -ENOSPC;
1881 
1882         inode = shmem_get_inode(dir->i_sb, dir, mode, 0, VM_NORESERVE);
1883         if (inode) {
1884                 error = security_inode_init_security(inode, dir,
1885                                                      NULL,
1886                                                      shmem_initxattrs, NULL);
1887                 if (error && error != -EOPNOTSUPP)
1888                         goto out_iput;
1889                 error = simple_acl_create(dir, inode);
1890                 if (error)
1891                         goto out_iput;
1892                 d_tmpfile(dentry, inode);
1893         }
1894         return error;
1895 out_iput:
1896         iput(inode);
1897         return error;
1898 }
1899 
1900 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
1901 {
1902         int error;
1903 
1904         if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1905                 return error;
1906         inc_nlink(dir);
1907         return 0;
1908 }
1909 
1910 static int shmem_create(struct inode *dir, struct dentry *dentry, umode_t mode,
1911                 bool excl)
1912 {
1913         return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1914 }
1915 
1916 /*
1917  * Link a file..
1918  */
1919 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1920 {
1921         struct inode *inode = old_dentry->d_inode;
1922         int ret;
1923 
1924         /*
1925          * No ordinary (disk based) filesystem counts links as inodes;
1926          * but each new link needs a new dentry, pinning lowmem, and
1927          * tmpfs dentries cannot be pruned until they are unlinked.
1928          */
1929         ret = shmem_reserve_inode(inode->i_sb);
1930         if (ret)
1931                 goto out;
1932 
1933         dir->i_size += BOGO_DIRENT_SIZE;
1934         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1935         inc_nlink(inode);
1936         ihold(inode);   /* New dentry reference */
1937         dget(dentry);           /* Extra pinning count for the created dentry */
1938         d_instantiate(dentry, inode);
1939 out:
1940         return ret;
1941 }
1942 
1943 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
1944 {
1945         struct inode *inode = dentry->d_inode;
1946 
1947         if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
1948                 shmem_free_inode(inode->i_sb);
1949 
1950         dir->i_size -= BOGO_DIRENT_SIZE;
1951         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1952         drop_nlink(inode);
1953         dput(dentry);   /* Undo the count from "create" - this does all the work */
1954         return 0;
1955 }
1956 
1957 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
1958 {
1959         if (!simple_empty(dentry))
1960                 return -ENOTEMPTY;
1961 
1962         drop_nlink(dentry->d_inode);
1963         drop_nlink(dir);
1964         return shmem_unlink(dir, dentry);
1965 }
1966 
1967 /*
1968  * The VFS layer already does all the dentry stuff for rename,
1969  * we just have to decrement the usage count for the target if
1970  * it exists so that the VFS layer correctly free's it when it
1971  * gets overwritten.
1972  */
1973 static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
1974 {
1975         struct inode *inode = old_dentry->d_inode;
1976         int they_are_dirs = S_ISDIR(inode->i_mode);
1977 
1978         if (!simple_empty(new_dentry))
1979                 return -ENOTEMPTY;
1980 
1981         if (new_dentry->d_inode) {
1982                 (void) shmem_unlink(new_dir, new_dentry);
1983                 if (they_are_dirs)
1984                         drop_nlink(old_dir);
1985         } else if (they_are_dirs) {
1986                 drop_nlink(old_dir);
1987                 inc_nlink(new_dir);
1988         }
1989 
1990         old_dir->i_size -= BOGO_DIRENT_SIZE;
1991         new_dir->i_size += BOGO_DIRENT_SIZE;
1992         old_dir->i_ctime = old_dir->i_mtime =
1993         new_dir->i_ctime = new_dir->i_mtime =
1994         inode->i_ctime = CURRENT_TIME;
1995         return 0;
1996 }
1997 
1998 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
1999 {
2000         int error;
2001         int len;
2002         struct inode *inode;
2003         struct page *page;
2004         char *kaddr;
2005         struct shmem_inode_info *info;
2006 
2007         len = strlen(symname) + 1;
2008         if (len > PAGE_CACHE_SIZE)
2009                 return -ENAMETOOLONG;
2010 
2011         inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE);
2012         if (!inode)
2013                 return -ENOSPC;
2014 
2015         error = security_inode_init_security(inode, dir, &dentry->d_name,
2016                                              shmem_initxattrs, NULL);
2017         if (error) {
2018                 if (error != -EOPNOTSUPP) {
2019                         iput(inode);
2020                         return error;
2021                 }
2022                 error = 0;
2023         }
2024 
2025         info = SHMEM_I(inode);
2026         inode->i_size = len-1;
2027         if (len <= SHORT_SYMLINK_LEN) {
2028                 info->symlink = kmemdup(symname, len, GFP_KERNEL);
2029                 if (!info->symlink) {
2030                         iput(inode);
2031                         return -ENOMEM;
2032                 }
2033                 inode->i_op = &shmem_short_symlink_operations;
2034         } else {
2035                 error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
2036                 if (error) {
2037                         iput(inode);
2038                         return error;
2039                 }
2040                 inode->i_mapping->a_ops = &shmem_aops;
2041                 inode->i_op = &shmem_symlink_inode_operations;
2042                 kaddr = kmap_atomic(page);
2043                 memcpy(kaddr, symname, len);
2044                 kunmap_atomic(kaddr);
2045                 SetPageUptodate(page);
2046                 set_page_dirty(page);
2047                 unlock_page(page);
2048                 page_cache_release(page);
2049         }
2050         dir->i_size += BOGO_DIRENT_SIZE;
2051         dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2052         d_instantiate(dentry, inode);
2053         dget(dentry);
2054         return 0;
2055 }
2056 
2057 static void *shmem_follow_short_symlink(struct dentry *dentry, struct nameidata *nd)
2058 {
2059         nd_set_link(nd, SHMEM_I(dentry->d_inode)->symlink);
2060         return NULL;
2061 }
2062 
2063 static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
2064 {
2065         struct page *page = NULL;
2066         int error = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
2067         nd_set_link(nd, error ? ERR_PTR(error) : kmap(page));
2068         if (page)
2069                 unlock_page(page);
2070         return page;
2071 }
2072 
2073 static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
2074 {
2075         if (!IS_ERR(nd_get_link(nd))) {
2076                 struct page *page = cookie;
2077                 kunmap(page);
2078                 mark_page_accessed(page);
2079                 page_cache_release(page);
2080         }
2081 }
2082 
2083 #ifdef CONFIG_TMPFS_XATTR
2084 /*
2085  * Superblocks without xattr inode operations may get some security.* xattr
2086  * support from the LSM "for free". As soon as we have any other xattrs
2087  * like ACLs, we also need to implement the security.* handlers at
2088  * filesystem level, though.
2089  */
2090 
2091 /*
2092  * Callback for security_inode_init_security() for acquiring xattrs.
2093  */
2094 static int shmem_initxattrs(struct inode *inode,
2095                             const struct xattr *xattr_array,
2096                             void *fs_info)
2097 {
2098         struct shmem_inode_info *info = SHMEM_I(inode);
2099         const struct xattr *xattr;
2100         struct simple_xattr *new_xattr;
2101         size_t len;
2102 
2103         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
2104                 new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len);
2105                 if (!new_xattr)
2106                         return -ENOMEM;
2107 
2108                 len = strlen(xattr->name) + 1;
2109                 new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
2110                                           GFP_KERNEL);
2111                 if (!new_xattr->name) {
2112                         kfree(new_xattr);
2113                         return -ENOMEM;
2114                 }
2115 
2116                 memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
2117                        XATTR_SECURITY_PREFIX_LEN);
2118                 memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
2119                        xattr->name, len);
2120 
2121                 simple_xattr_list_add(&info->xattrs, new_xattr);
2122         }
2123 
2124         return 0;
2125 }
2126 
2127 static const struct xattr_handler *shmem_xattr_handlers[] = {
2128 #ifdef CONFIG_TMPFS_POSIX_ACL
2129         &posix_acl_access_xattr_handler,
2130         &posix_acl_default_xattr_handler,
2131 #endif
2132         NULL
2133 };
2134 
2135 static int shmem_xattr_validate(const char *name)
2136 {
2137         struct { const char *prefix; size_t len; } arr[] = {
2138                 { XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN },
2139                 { XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN }
2140         };
2141         int i;
2142 
2143         for (i = 0; i < ARRAY_SIZE(arr); i++) {
2144                 size_t preflen = arr[i].len;
2145                 if (strncmp(name, arr[i].prefix, preflen) == 0) {
2146                         if (!name[preflen])
2147                                 return -EINVAL;
2148                         return 0;
2149                 }
2150         }
2151         return -EOPNOTSUPP;
2152 }
2153 
2154 static ssize_t shmem_getxattr(struct dentry *dentry, const char *name,
2155                               void *buffer, size_t size)
2156 {
2157         struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2158         int err;
2159 
2160         /*
2161          * If this is a request for a synthetic attribute in the system.*
2162          * namespace use the generic infrastructure to resolve a handler
2163          * for it via sb->s_xattr.
2164          */
2165         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2166                 return generic_getxattr(dentry, name, buffer, size);
2167 
2168         err = shmem_xattr_validate(name);
2169         if (err)
2170                 return err;
2171 
2172         return simple_xattr_get(&info->xattrs, name, buffer, size);
2173 }
2174 
2175 static int shmem_setxattr(struct dentry *dentry, const char *name,
2176                           const void *value, size_t size, int flags)
2177 {
2178         struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2179         int err;
2180 
2181         /*
2182          * If this is a request for a synthetic attribute in the system.*
2183          * namespace use the generic infrastructure to resolve a handler
2184          * for it via sb->s_xattr.
2185          */
2186         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2187                 return generic_setxattr(dentry, name, value, size, flags);
2188 
2189         err = shmem_xattr_validate(name);
2190         if (err)
2191                 return err;
2192 
2193         return simple_xattr_set(&info->xattrs, name, value, size, flags);
2194 }
2195 
2196 static int shmem_removexattr(struct dentry *dentry, const char *name)
2197 {
2198         struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2199         int err;
2200 
2201         /*
2202          * If this is a request for a synthetic attribute in the system.*
2203          * namespace use the generic infrastructure to resolve a handler
2204          * for it via sb->s_xattr.
2205          */
2206         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2207                 return generic_removexattr(dentry, name);
2208 
2209         err = shmem_xattr_validate(name);
2210         if (err)
2211                 return err;
2212 
2213         return simple_xattr_remove(&info->xattrs, name);
2214 }
2215 
2216 static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
2217 {
2218         struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2219         return simple_xattr_list(&info->xattrs, buffer, size);
2220 }
2221 #endif /* CONFIG_TMPFS_XATTR */
2222 
2223 static const struct inode_operations shmem_short_symlink_operations = {
2224         .readlink       = generic_readlink,
2225         .follow_link    = shmem_follow_short_symlink,
2226 #ifdef CONFIG_TMPFS_XATTR
2227         .setxattr       = shmem_setxattr,
2228         .getxattr       = shmem_getxattr,
2229         .listxattr      = shmem_listxattr,
2230         .removexattr    = shmem_removexattr,
2231 #endif
2232 };
2233 
2234 static const struct inode_operations shmem_symlink_inode_operations = {
2235         .readlink       = generic_readlink,
2236         .follow_link    = shmem_follow_link,
2237         .put_link       = shmem_put_link,
2238 #ifdef CONFIG_TMPFS_XATTR
2239         .setxattr       = shmem_setxattr,
2240         .getxattr       = shmem_getxattr,
2241         .listxattr      = shmem_listxattr,
2242         .removexattr    = shmem_removexattr,
2243 #endif
2244 };
2245 
2246 static struct dentry *shmem_get_parent(struct dentry *child)
2247 {
2248         return ERR_PTR(-ESTALE);
2249 }
2250 
2251 static int shmem_match(struct inode *ino, void *vfh)
2252 {
2253         __u32 *fh = vfh;
2254         __u64 inum = fh[2];
2255         inum = (inum << 32) | fh[1];
2256         return ino->i_ino == inum && fh[0] == ino->i_generation;
2257 }
2258 
2259 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
2260                 struct fid *fid, int fh_len, int fh_type)
2261 {
2262         struct inode *inode;
2263         struct dentry *dentry = NULL;
2264         u64 inum;
2265 
2266         if (fh_len < 3)
2267                 return NULL;
2268 
2269         inum = fid->raw[2];
2270         inum = (inum << 32) | fid->raw[1];
2271 
2272         inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
2273                         shmem_match, fid->raw);
2274         if (inode) {
2275                 dentry = d_find_alias(inode);
2276                 iput(inode);
2277         }
2278 
2279         return dentry;
2280 }
2281 
2282 static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len,
2283                                 struct inode *parent)
2284 {
2285         if (*len < 3) {
2286                 *len = 3;
2287                 return FILEID_INVALID;
2288         }
2289 
2290         if (inode_unhashed(inode)) {
2291                 /* Unfortunately insert_inode_hash is not idempotent,
2292                  * so as we hash inodes here rather than at creation
2293                  * time, we need a lock to ensure we only try
2294                  * to do it once
2295                  */
2296                 static DEFINE_SPINLOCK(lock);
2297                 spin_lock(&lock);
2298                 if (inode_unhashed(inode))
2299                         __insert_inode_hash(inode,
2300                                             inode->i_ino + inode->i_generation);
2301                 spin_unlock(&lock);
2302         }
2303 
2304         fh[0] = inode->i_generation;
2305         fh[1] = inode->i_ino;
2306         fh[2] = ((__u64)inode->i_ino) >> 32;
2307 
2308         *len = 3;
2309         return 1;
2310 }
2311 
2312 static const struct export_operations shmem_export_ops = {
2313         .get_parent     = shmem_get_parent,
2314         .encode_fh      = shmem_encode_fh,
2315         .fh_to_dentry   = shmem_fh_to_dentry,
2316 };
2317 
2318 static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
2319                                bool remount)
2320 {
2321         char *this_char, *value, *rest;
2322         struct mempolicy *mpol = NULL;
2323         uid_t uid;
2324         gid_t gid;
2325 
2326         while (options != NULL) {
2327                 this_char = options;
2328                 for (;;) {
2329                         /*
2330                          * NUL-terminate this option: unfortunately,
2331                          * mount options form a comma-separated list,
2332                          * but mpol's nodelist may also contain commas.
2333                          */
2334                         options = strchr(options, ',');
2335                         if (options == NULL)
2336                                 break;
2337                         options++;
2338                         if (!isdigit(*options)) {
2339                                 options[-1] = '\0';
2340                                 break;
2341                         }
2342                 }
2343                 if (!*this_char)
2344                         continue;
2345                 if ((value = strchr(this_char,'=')) != NULL) {
2346                         *value++ = 0;
2347                 } else {
2348                         printk(KERN_ERR
2349                             "tmpfs: No value for mount option '%s'\n",
2350                             this_char);
2351                         goto error;
2352                 }
2353 
2354                 if (!strcmp(this_char,"size")) {
2355                         unsigned long long size;
2356                         size = memparse(value,&rest);
2357                         if (*rest == '%') {
2358                                 size <<= PAGE_SHIFT;
2359                                 size *= totalram_pages;
2360                                 do_div(size, 100);
2361                                 rest++;
2362                         }
2363                         if (*rest)
2364                                 goto bad_val;
2365                         sbinfo->max_blocks =
2366                                 DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
2367                 } else if (!strcmp(this_char,"nr_blocks")) {
2368                         sbinfo->max_blocks = memparse(value, &rest);
2369                         if (*rest)
2370                                 goto bad_val;
2371                 } else if (!strcmp(this_char,"nr_inodes")) {
2372                         sbinfo->max_inodes = memparse(value, &rest);
2373                         if (*rest)
2374                                 goto bad_val;
2375                 } else if (!strcmp(this_char,"mode")) {
2376                         if (remount)
2377                                 continue;
2378                         sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
2379                         if (*rest)
2380                                 goto bad_val;
2381                 } else if (!strcmp(this_char,"uid")) {
2382                         if (remount)
2383                                 continue;
2384                         uid = simple_strtoul(value, &rest, 0);
2385                         if (*rest)
2386                                 goto bad_val;
2387                         sbinfo->uid = make_kuid(current_user_ns(), uid);
2388                         if (!uid_valid(sbinfo->uid))
2389                                 goto bad_val;
2390                 } else if (!strcmp(this_char,"gid")) {
2391                         if (remount)
2392                                 continue;
2393                         gid = simple_strtoul(value, &rest, 0);
2394                         if (*rest)
2395                                 goto bad_val;
2396                         sbinfo->gid = make_kgid(current_user_ns(), gid);
2397                         if (!gid_valid(sbinfo->gid))
2398                                 goto bad_val;
2399                 } else if (!strcmp(this_char,"mpol")) {
2400                         mpol_put(mpol);
2401                         mpol = NULL;
2402                         if (mpol_parse_str(value, &mpol))
2403                                 goto bad_val;
2404                 } else {
2405                         printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2406                                this_char);
2407                         goto error;
2408                 }
2409         }
2410         sbinfo->mpol = mpol;
2411         return 0;
2412 
2413 bad_val:
2414         printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2415                value, this_char);
2416 error:
2417         mpol_put(mpol);
2418         return 1;
2419 
2420 }
2421 
2422 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2423 {
2424         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2425         struct shmem_sb_info config = *sbinfo;
2426         unsigned long inodes;
2427         int error = -EINVAL;
2428 
2429         config.mpol = NULL;
2430         if (shmem_parse_options(data, &config, true))
2431                 return error;
2432 
2433         spin_lock(&sbinfo->stat_lock);
2434         inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2435         if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0)
2436                 goto out;
2437         if (config.max_inodes < inodes)
2438                 goto out;
2439         /*
2440          * Those tests disallow limited->unlimited while any are in use;
2441          * but we must separately disallow unlimited->limited, because
2442          * in that case we have no record of how much is already in use.
2443          */
2444         if (config.max_blocks && !sbinfo->max_blocks)
2445                 goto out;
2446         if (config.max_inodes && !sbinfo->max_inodes)
2447                 goto out;
2448 
2449         error = 0;
2450         sbinfo->max_blocks  = config.max_blocks;
2451         sbinfo->max_inodes  = config.max_inodes;
2452         sbinfo->free_inodes = config.max_inodes - inodes;
2453 
2454         /*
2455          * Preserve previous mempolicy unless mpol remount option was specified.
2456          */
2457         if (config.mpol) {
2458                 mpol_put(sbinfo->mpol);
2459                 sbinfo->mpol = config.mpol;     /* transfers initial ref */
2460         }
2461 out:
2462         spin_unlock(&sbinfo->stat_lock);
2463         return error;
2464 }
2465 
2466 static int shmem_show_options(struct seq_file *seq, struct dentry *root)
2467 {
2468         struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb);
2469 
2470         if (sbinfo->max_blocks != shmem_default_max_blocks())
2471                 seq_printf(seq, ",size=%luk",
2472                         sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
2473         if (sbinfo->max_inodes != shmem_default_max_inodes())
2474                 seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
2475         if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
2476                 seq_printf(seq, ",mode=%03ho", sbinfo->mode);
2477         if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
2478                 seq_printf(seq, ",uid=%u",
2479                                 from_kuid_munged(&init_user_ns, sbinfo->uid));
2480         if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
2481                 seq_printf(seq, ",gid=%u",
2482                                 from_kgid_munged(&init_user_ns, sbinfo->gid));
2483         shmem_show_mpol(seq, sbinfo->mpol);
2484         return 0;
2485 }
2486 #endif /* CONFIG_TMPFS */
2487 
2488 static void shmem_put_super(struct super_block *sb)
2489 {
2490         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2491 
2492         percpu_counter_destroy(&sbinfo->used_blocks);
2493         mpol_put(sbinfo->mpol);
2494         kfree(sbinfo);
2495         sb->s_fs_info = NULL;
2496 }
2497 
2498 int shmem_fill_super(struct super_block *sb, void *data, int silent)
2499 {
2500         struct inode *inode;
2501         struct shmem_sb_info *sbinfo;
2502         int err = -ENOMEM;
2503 
2504         /* Round up to L1_CACHE_BYTES to resist false sharing */
2505         sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
2506                                 L1_CACHE_BYTES), GFP_KERNEL);
2507         if (!sbinfo)
2508                 return -ENOMEM;
2509 
2510         sbinfo->mode = S_IRWXUGO | S_ISVTX;
2511         sbinfo->uid = current_fsuid();
2512         sbinfo->gid = current_fsgid();
2513         sb->s_fs_info = sbinfo;
2514 
2515 #ifdef CONFIG_TMPFS
2516         /*
2517          * Per default we only allow half of the physical ram per
2518          * tmpfs instance, limiting inodes to one per page of lowmem;
2519          * but the internal instance is left unlimited.
2520          */
2521         if (!(sb->s_flags & MS_KERNMOUNT)) {
2522                 sbinfo->max_blocks = shmem_default_max_blocks();
2523                 sbinfo->max_inodes = shmem_default_max_inodes();
2524                 if (shmem_parse_options(data, sbinfo, false)) {
2525                         err = -EINVAL;
2526                         goto failed;
2527                 }
2528         } else {
2529                 sb->s_flags |= MS_NOUSER;
2530         }
2531         sb->s_export_op = &shmem_export_ops;
2532         sb->s_flags |= MS_NOSEC;
2533 #else
2534         sb->s_flags |= MS_NOUSER;
2535 #endif
2536 
2537         spin_lock_init(&sbinfo->stat_lock);
2538         if (percpu_counter_init(&sbinfo->used_blocks, 0))
2539                 goto failed;
2540         sbinfo->free_inodes = sbinfo->max_inodes;
2541 
2542         sb->s_maxbytes = MAX_LFS_FILESIZE;
2543         sb->s_blocksize = PAGE_CACHE_SIZE;
2544         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2545         sb->s_magic = TMPFS_MAGIC;
2546         sb->s_op = &shmem_ops;
2547         sb->s_time_gran = 1;
2548 #ifdef CONFIG_TMPFS_XATTR
2549         sb->s_xattr = shmem_xattr_handlers;
2550 #endif
2551 #ifdef CONFIG_TMPFS_POSIX_ACL
2552         sb->s_flags |= MS_POSIXACL;
2553 #endif
2554 
2555         inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
2556         if (!inode)
2557                 goto failed;
2558         inode->i_uid = sbinfo->uid;
2559         inode->i_gid = sbinfo->gid;
2560         sb->s_root = d_make_root(inode);
2561         if (!sb->s_root)
2562                 goto failed;
2563         return 0;
2564 
2565 failed:
2566         shmem_put_super(sb);
2567         return err;
2568 }
2569 
2570 static struct kmem_cache *shmem_inode_cachep;
2571 
2572 static struct inode *shmem_alloc_inode(struct super_block *sb)
2573 {
2574         struct shmem_inode_info *info;
2575         info = kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2576         if (!info)
2577                 return NULL;
2578         return &info->vfs_inode;
2579 }
2580 
2581 static void shmem_destroy_callback(struct rcu_head *head)
2582 {
2583         struct inode *inode = container_of(head, struct inode, i_rcu);
2584         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2585 }
2586 
2587 static void shmem_destroy_inode(struct inode *inode)
2588 {
2589         if (S_ISREG(inode->i_mode))
2590                 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2591         call_rcu(&inode->i_rcu, shmem_destroy_callback);
2592 }
2593 
2594 static void shmem_init_inode(void *foo)
2595 {
2596         struct shmem_inode_info *info = foo;
2597         inode_init_once(&info->vfs_inode);
2598 }
2599 
2600 static int shmem_init_inodecache(void)
2601 {
2602         shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2603                                 sizeof(struct shmem_inode_info),
2604                                 0, SLAB_PANIC, shmem_init_inode);
2605         return 0;
2606 }
2607 
2608 static void shmem_destroy_inodecache(void)
2609 {
2610         kmem_cache_destroy(shmem_inode_cachep);
2611 }
2612 
2613 static const struct address_space_operations shmem_aops = {
2614         .writepage      = shmem_writepage,
2615         .set_page_dirty = __set_page_dirty_no_writeback,
2616 #ifdef CONFIG_TMPFS
2617         .write_begin    = shmem_write_begin,
2618         .write_end      = shmem_write_end,
2619 #endif
2620         .migratepage    = migrate_page,
2621         .error_remove_page = generic_error_remove_page,
2622 };
2623 
2624 static const struct file_operations shmem_file_operations = {
2625         .mmap           = shmem_mmap,
2626 #ifdef CONFIG_TMPFS
2627         .llseek         = shmem_file_llseek,
2628         .read           = do_sync_read,
2629         .write          = do_sync_write,
2630         .aio_read       = shmem_file_aio_read,
2631         .aio_write      = generic_file_aio_write,
2632         .fsync          = noop_fsync,
2633         .splice_read    = shmem_file_splice_read,
2634         .splice_write   = generic_file_splice_write,
2635         .fallocate      = shmem_fallocate,
2636 #endif
2637 };
2638 
2639 static const struct inode_operations shmem_inode_operations = {
2640         .setattr        = shmem_setattr,
2641 #ifdef CONFIG_TMPFS_XATTR
2642         .setxattr       = shmem_setxattr,
2643         .getxattr       = shmem_getxattr,
2644         .listxattr      = shmem_listxattr,
2645         .removexattr    = shmem_removexattr,
2646         .set_acl        = simple_set_acl,
2647 #endif
2648 };
2649 
2650 static const struct inode_operations shmem_dir_inode_operations = {
2651 #ifdef CONFIG_TMPFS
2652         .create         = shmem_create,
2653         .lookup         = simple_lookup,
2654         .link           = shmem_link,
2655         .unlink         = shmem_unlink,
2656         .symlink        = shmem_symlink,
2657         .mkdir          = shmem_mkdir,
2658         .rmdir          = shmem_rmdir,
2659         .mknod          = shmem_mknod,
2660         .rename         = shmem_rename,
2661         .tmpfile        = shmem_tmpfile,
2662 #endif
2663 #ifdef CONFIG_TMPFS_XATTR
2664         .setxattr       = shmem_setxattr,
2665         .getxattr       = shmem_getxattr,
2666         .listxattr      = shmem_listxattr,
2667         .removexattr    = shmem_removexattr,
2668 #endif
2669 #ifdef CONFIG_TMPFS_POSIX_ACL
2670         .setattr        = shmem_setattr,
2671         .set_acl        = simple_set_acl,
2672 #endif
2673 };
2674 
2675 static const struct inode_operations shmem_special_inode_operations = {
2676 #ifdef CONFIG_TMPFS_XATTR
2677         .setxattr       = shmem_setxattr,
2678         .getxattr       = shmem_getxattr,
2679         .listxattr      = shmem_listxattr,
2680         .removexattr    = shmem_removexattr,
2681 #endif
2682 #ifdef CONFIG_TMPFS_POSIX_ACL
2683         .setattr        = shmem_setattr,
2684         .set_acl        = simple_set_acl,
2685 #endif
2686 };
2687 
2688 static const struct super_operations shmem_ops = {
2689         .alloc_inode    = shmem_alloc_inode,
2690         .destroy_inode  = shmem_destroy_inode,
2691 #ifdef CONFIG_TMPFS
2692         .statfs         = shmem_statfs,
2693         .remount_fs     = shmem_remount_fs,
2694         .show_options   = shmem_show_options,
2695 #endif
2696         .evict_inode    = shmem_evict_inode,
2697         .drop_inode     = generic_delete_inode,
2698         .put_super      = shmem_put_super,
2699 };
2700 
2701 static const struct vm_operations_struct shmem_vm_ops = {
2702         .fault          = shmem_fault,
2703         .map_pages      = filemap_map_pages,
2704 #ifdef CONFIG_NUMA
2705         .set_policy     = shmem_set_policy,
2706         .get_policy     = shmem_get_policy,
2707 #endif
2708         .remap_pages    = generic_file_remap_pages,
2709 };
2710 
2711 static struct dentry *shmem_mount(struct file_system_type *fs_type,
2712         int flags, const char *dev_name, void *data)
2713 {
2714         return mount_nodev(fs_type, flags, data, shmem_fill_super);
2715 }
2716 
2717 static struct file_system_type shmem_fs_type = {
2718         .owner          = THIS_MODULE,
2719         .name           = "tmpfs",
2720         .mount          = shmem_mount,
2721         .kill_sb        = kill_litter_super,
2722         .fs_flags       = FS_USERNS_MOUNT,
2723 };
2724 
2725 int __init shmem_init(void)
2726 {
2727         int error;
2728 
2729         /* If rootfs called this, don't re-init */
2730         if (shmem_inode_cachep)
2731                 return 0;
2732 
2733         error = bdi_init(&shmem_backing_dev_info);
2734         if (error)
2735                 goto out4;
2736 
2737         error = shmem_init_inodecache();
2738         if (error)
2739                 goto out3;
2740 
2741         error = register_filesystem(&shmem_fs_type);
2742         if (error) {
2743                 printk(KERN_ERR "Could not register tmpfs\n");
2744                 goto out2;
2745         }
2746 
2747         shm_mnt = kern_mount(&shmem_fs_type);
2748         if (IS_ERR(shm_mnt)) {
2749                 error = PTR_ERR(shm_mnt);
2750                 printk(KERN_ERR "Could not kern_mount tmpfs\n");
2751                 goto out1;
2752         }
2753         return 0;
2754 
2755 out1:
2756         unregister_filesystem(&shmem_fs_type);
2757 out2:
2758         shmem_destroy_inodecache();
2759 out3:
2760         bdi_destroy(&shmem_backing_dev_info);
2761 out4:
2762         shm_mnt = ERR_PTR(error);
2763         return error;
2764 }
2765 
2766 #else /* !CONFIG_SHMEM */
2767 
2768 /*
2769  * tiny-shmem: simple shmemfs and tmpfs using ramfs code
2770  *
2771  * This is intended for small system where the benefits of the full
2772  * shmem code (swap-backed and resource-limited) are outweighed by
2773  * their complexity. On systems without swap this code should be
2774  * effectively equivalent, but much lighter weight.
2775  */
2776 
2777 static struct file_system_type shmem_fs_type = {
2778         .name           = "tmpfs",
2779         .mount          = ramfs_mount,
2780         .kill_sb        = kill_litter_super,
2781         .fs_flags       = FS_USERNS_MOUNT,
2782 };
2783 
2784 int __init shmem_init(void)
2785 {
2786         BUG_ON(register_filesystem(&shmem_fs_type) != 0);
2787 
2788         shm_mnt = kern_mount(&shmem_fs_type);
2789         BUG_ON(IS_ERR(shm_mnt));
2790 
2791         return 0;
2792 }
2793 
2794 int shmem_unuse(swp_entry_t swap, struct page *page)
2795 {
2796         return 0;
2797 }
2798 
2799 int shmem_lock(struct file *file, int lock, struct user_struct *user)
2800 {
2801         return 0;
2802 }
2803 
2804 void shmem_unlock_mapping(struct address_space *mapping)
2805 {
2806 }
2807 
2808 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
2809 {
2810         truncate_inode_pages_range(inode->i_mapping, lstart, lend);
2811 }
2812 EXPORT_SYMBOL_GPL(shmem_truncate_range);
2813 
2814 #define shmem_vm_ops                            generic_file_vm_ops
2815 #define shmem_file_operations                   ramfs_file_operations
2816 #define shmem_get_inode(sb, dir, mode, dev, flags)      ramfs_get_inode(sb, dir, mode, dev)
2817 #define shmem_acct_size(flags, size)            0
2818 #define shmem_unacct_size(flags, size)          do {} while (0)
2819 
2820 #endif /* CONFIG_SHMEM */
2821 
2822 /* common code */
2823 
2824 static struct dentry_operations anon_ops = {
2825         .d_dname = simple_dname
2826 };
2827 
2828 static struct file *__shmem_file_setup(const char *name, loff_t size,
2829                                        unsigned long flags, unsigned int i_flags)
2830 {
2831         struct file *res;
2832         struct inode *inode;
2833         struct path path;
2834         struct super_block *sb;
2835         struct qstr this;
2836 
2837         if (IS_ERR(shm_mnt))
2838                 return ERR_CAST(shm_mnt);
2839 
2840         if (size < 0 || size > MAX_LFS_FILESIZE)
2841                 return ERR_PTR(-EINVAL);
2842 
2843         if (shmem_acct_size(flags, size))
2844                 return ERR_PTR(-ENOMEM);
2845 
2846         res = ERR_PTR(-ENOMEM);
2847         this.name = name;
2848         this.len = strlen(name);
2849         this.hash = 0; /* will go */
2850         sb = shm_mnt->mnt_sb;
2851         path.dentry = d_alloc_pseudo(sb, &this);
2852         if (!path.dentry)
2853                 goto put_memory;
2854         d_set_d_op(path.dentry, &anon_ops);
2855         path.mnt = mntget(shm_mnt);
2856 
2857         res = ERR_PTR(-ENOSPC);
2858         inode = shmem_get_inode(sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
2859         if (!inode)
2860                 goto put_dentry;
2861 
2862         inode->i_flags |= i_flags;
2863         d_instantiate(path.dentry, inode);
2864         inode->i_size = size;
2865         clear_nlink(inode);     /* It is unlinked */
2866         res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size));
2867         if (IS_ERR(res))
2868                 goto put_dentry;
2869 
2870         res = alloc_file(&path, FMODE_WRITE | FMODE_READ,
2871                   &shmem_file_operations);
2872         if (IS_ERR(res))
2873                 goto put_dentry;
2874 
2875         return res;
2876 
2877 put_dentry:
2878         path_put(&path);
2879 put_memory:
2880         shmem_unacct_size(flags, size);
2881         return res;
2882 }
2883 
2884 /**
2885  * shmem_kernel_file_setup - get an unlinked file living in tmpfs which must be
2886  *      kernel internal.  There will be NO LSM permission checks against the
2887  *      underlying inode.  So users of this interface must do LSM checks at a
2888  *      higher layer.  The one user is the big_key implementation.  LSM checks
2889  *      are provided at the key level rather than the inode level.
2890  * @name: name for dentry (to be seen in /proc/<pid>/maps
2891  * @size: size to be set for the file
2892  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
2893  */
2894 struct file *shmem_kernel_file_setup(const char *name, loff_t size, unsigned long flags)
2895 {
2896         return __shmem_file_setup(name, size, flags, S_PRIVATE);
2897 }
2898 
2899 /**
2900  * shmem_file_setup - get an unlinked file living in tmpfs
2901  * @name: name for dentry (to be seen in /proc/<pid>/maps
2902  * @size: size to be set for the file
2903  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
2904  */
2905 struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
2906 {
2907         return __shmem_file_setup(name, size, flags, 0);
2908 }
2909 EXPORT_SYMBOL_GPL(shmem_file_setup);
2910 
2911 /**
2912  * shmem_zero_setup - setup a shared anonymous mapping
2913  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2914  */
2915 int shmem_zero_setup(struct vm_area_struct *vma)
2916 {
2917         struct file *file;
2918         loff_t size = vma->vm_end - vma->vm_start;
2919 
2920         file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2921         if (IS_ERR(file))
2922                 return PTR_ERR(file);
2923 
2924         if (vma->vm_file)
2925                 fput(vma->vm_file);
2926         vma->vm_file = file;
2927         vma->vm_ops = &shmem_vm_ops;
2928         return 0;
2929 }
2930 
2931 /**
2932  * shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags.
2933  * @mapping:    the page's address_space
2934  * @index:      the page index
2935  * @gfp:        the page allocator flags to use if allocating
2936  *
2937  * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)",
2938  * with any new page allocations done using the specified allocation flags.
2939  * But read_cache_page_gfp() uses the ->readpage() method: which does not
2940  * suit tmpfs, since it may have pages in swapcache, and needs to find those
2941  * for itself; although drivers/gpu/drm i915 and ttm rely upon this support.
2942  *
2943  * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in
2944  * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily.
2945  */
2946 struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
2947                                          pgoff_t index, gfp_t gfp)
2948 {
2949 #ifdef CONFIG_SHMEM
2950         struct inode *inode = mapping->host;
2951         struct page *page;
2952         int error;
2953 
2954         BUG_ON(mapping->a_ops != &shmem_aops);
2955         error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE, gfp, NULL);
2956         if (error)
2957                 page = ERR_PTR(error);
2958         else
2959                 unlock_page(page);
2960         return page;
2961 #else
2962         /*
2963          * The tiny !SHMEM case uses ramfs without swap
2964          */
2965         return read_cache_page_gfp(mapping, index, gfp);
2966 #endif
2967 }
2968 EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);
2969 

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