new helper: inode_unhashed()
[linux-2.6.git] / 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) 2002-2005 Hugh Dickins.
10  * Copyright (C) 2002-2005 VERITAS Software Corporation.
11  * Copyright (C) 2004 Andi Kleen, SuSE Labs
12  *
13  * Extended attribute support for tmpfs:
14  * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
15  * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
16  *
17  * tiny-shmem:
18  * Copyright (c) 2004, 2008 Matt Mackall <mpm@selenic.com>
19  *
20  * This file is released under the GPL.
21  */
22
23 #include <linux/fs.h>
24 #include <linux/init.h>
25 #include <linux/vfs.h>
26 #include <linux/mount.h>
27 #include <linux/pagemap.h>
28 #include <linux/file.h>
29 #include <linux/mm.h>
30 #include <linux/module.h>
31 #include <linux/percpu_counter.h>
32 #include <linux/swap.h>
33
34 static struct vfsmount *shm_mnt;
35
36 #ifdef CONFIG_SHMEM
37 /*
38  * This virtual memory filesystem is heavily based on the ramfs. It
39  * extends ramfs by the ability to use swap and honor resource limits
40  * which makes it a completely usable filesystem.
41  */
42
43 #include <linux/xattr.h>
44 #include <linux/exportfs.h>
45 #include <linux/posix_acl.h>
46 #include <linux/generic_acl.h>
47 #include <linux/mman.h>
48 #include <linux/string.h>
49 #include <linux/slab.h>
50 #include <linux/backing-dev.h>
51 #include <linux/shmem_fs.h>
52 #include <linux/writeback.h>
53 #include <linux/blkdev.h>
54 #include <linux/security.h>
55 #include <linux/swapops.h>
56 #include <linux/mempolicy.h>
57 #include <linux/namei.h>
58 #include <linux/ctype.h>
59 #include <linux/migrate.h>
60 #include <linux/highmem.h>
61 #include <linux/seq_file.h>
62 #include <linux/magic.h>
63
64 #include <asm/uaccess.h>
65 #include <asm/div64.h>
66 #include <asm/pgtable.h>
67
68 /*
69  * The maximum size of a shmem/tmpfs file is limited by the maximum size of
70  * its triple-indirect swap vector - see illustration at shmem_swp_entry().
71  *
72  * With 4kB page size, maximum file size is just over 2TB on a 32-bit kernel,
73  * but one eighth of that on a 64-bit kernel.  With 8kB page size, maximum
74  * file size is just over 4TB on a 64-bit kernel, but 16TB on a 32-bit kernel,
75  * MAX_LFS_FILESIZE being then more restrictive than swap vector layout.
76  *
77  * We use / and * instead of shifts in the definitions below, so that the swap
78  * vector can be tested with small even values (e.g. 20) for ENTRIES_PER_PAGE.
79  */
80 #define ENTRIES_PER_PAGE (PAGE_CACHE_SIZE/sizeof(unsigned long))
81 #define ENTRIES_PER_PAGEPAGE ((unsigned long long)ENTRIES_PER_PAGE*ENTRIES_PER_PAGE)
82
83 #define SHMSWP_MAX_INDEX (SHMEM_NR_DIRECT + (ENTRIES_PER_PAGEPAGE/2) * (ENTRIES_PER_PAGE+1))
84 #define SHMSWP_MAX_BYTES (SHMSWP_MAX_INDEX << PAGE_CACHE_SHIFT)
85
86 #define SHMEM_MAX_BYTES  min_t(unsigned long long, SHMSWP_MAX_BYTES, MAX_LFS_FILESIZE)
87 #define SHMEM_MAX_INDEX  ((unsigned long)((SHMEM_MAX_BYTES+1) >> PAGE_CACHE_SHIFT))
88
89 #define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
90 #define VM_ACCT(size)    (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
91
92 /* info->flags needs VM_flags to handle pagein/truncate races efficiently */
93 #define SHMEM_PAGEIN     VM_READ
94 #define SHMEM_TRUNCATE   VM_WRITE
95
96 /* Definition to limit shmem_truncate's steps between cond_rescheds */
97 #define LATENCY_LIMIT    64
98
99 /* Pretend that each entry is of this size in directory's i_size */
100 #define BOGO_DIRENT_SIZE 20
101
102 /* Flag allocation requirements to shmem_getpage and shmem_swp_alloc */
103 enum sgp_type {
104         SGP_READ,       /* don't exceed i_size, don't allocate page */
105         SGP_CACHE,      /* don't exceed i_size, may allocate page */
106         SGP_DIRTY,      /* like SGP_CACHE, but set new page dirty */
107         SGP_WRITE,      /* may exceed i_size, may allocate page */
108 };
109
110 #ifdef CONFIG_TMPFS
111 static unsigned long shmem_default_max_blocks(void)
112 {
113         return totalram_pages / 2;
114 }
115
116 static unsigned long shmem_default_max_inodes(void)
117 {
118         return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
119 }
120 #endif
121
122 static int shmem_getpage(struct inode *inode, unsigned long idx,
123                          struct page **pagep, enum sgp_type sgp, int *type);
124
125 static inline struct page *shmem_dir_alloc(gfp_t gfp_mask)
126 {
127         /*
128          * The above definition of ENTRIES_PER_PAGE, and the use of
129          * BLOCKS_PER_PAGE on indirect pages, assume PAGE_CACHE_SIZE:
130          * might be reconsidered if it ever diverges from PAGE_SIZE.
131          *
132          * Mobility flags are masked out as swap vectors cannot move
133          */
134         return alloc_pages((gfp_mask & ~GFP_MOVABLE_MASK) | __GFP_ZERO,
135                                 PAGE_CACHE_SHIFT-PAGE_SHIFT);
136 }
137
138 static inline void shmem_dir_free(struct page *page)
139 {
140         __free_pages(page, PAGE_CACHE_SHIFT-PAGE_SHIFT);
141 }
142
143 static struct page **shmem_dir_map(struct page *page)
144 {
145         return (struct page **)kmap_atomic(page, KM_USER0);
146 }
147
148 static inline void shmem_dir_unmap(struct page **dir)
149 {
150         kunmap_atomic(dir, KM_USER0);
151 }
152
153 static swp_entry_t *shmem_swp_map(struct page *page)
154 {
155         return (swp_entry_t *)kmap_atomic(page, KM_USER1);
156 }
157
158 static inline void shmem_swp_balance_unmap(void)
159 {
160         /*
161          * When passing a pointer to an i_direct entry, to code which
162          * also handles indirect entries and so will shmem_swp_unmap,
163          * we must arrange for the preempt count to remain in balance.
164          * What kmap_atomic of a lowmem page does depends on config
165          * and architecture, so pretend to kmap_atomic some lowmem page.
166          */
167         (void) kmap_atomic(ZERO_PAGE(0), KM_USER1);
168 }
169
170 static inline void shmem_swp_unmap(swp_entry_t *entry)
171 {
172         kunmap_atomic(entry, KM_USER1);
173 }
174
175 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
176 {
177         return sb->s_fs_info;
178 }
179
180 /*
181  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
182  * for shared memory and for shared anonymous (/dev/zero) mappings
183  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
184  * consistent with the pre-accounting of private mappings ...
185  */
186 static inline int shmem_acct_size(unsigned long flags, loff_t size)
187 {
188         return (flags & VM_NORESERVE) ?
189                 0 : security_vm_enough_memory_kern(VM_ACCT(size));
190 }
191
192 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
193 {
194         if (!(flags & VM_NORESERVE))
195                 vm_unacct_memory(VM_ACCT(size));
196 }
197
198 /*
199  * ... whereas tmpfs objects are accounted incrementally as
200  * pages are allocated, in order to allow huge sparse files.
201  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
202  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
203  */
204 static inline int shmem_acct_block(unsigned long flags)
205 {
206         return (flags & VM_NORESERVE) ?
207                 security_vm_enough_memory_kern(VM_ACCT(PAGE_CACHE_SIZE)) : 0;
208 }
209
210 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
211 {
212         if (flags & VM_NORESERVE)
213                 vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
214 }
215
216 static const struct super_operations shmem_ops;
217 static const struct address_space_operations shmem_aops;
218 static const struct file_operations shmem_file_operations;
219 static const struct inode_operations shmem_inode_operations;
220 static const struct inode_operations shmem_dir_inode_operations;
221 static const struct inode_operations shmem_special_inode_operations;
222 static const struct vm_operations_struct shmem_vm_ops;
223
224 static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
225         .ra_pages       = 0,    /* No readahead */
226         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
227         .unplug_io_fn   = default_unplug_io_fn,
228 };
229
230 static LIST_HEAD(shmem_swaplist);
231 static DEFINE_MUTEX(shmem_swaplist_mutex);
232
233 static void shmem_free_blocks(struct inode *inode, long pages)
234 {
235         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
236         if (sbinfo->max_blocks) {
237                 percpu_counter_add(&sbinfo->used_blocks, -pages);
238                 spin_lock(&inode->i_lock);
239                 inode->i_blocks -= pages*BLOCKS_PER_PAGE;
240                 spin_unlock(&inode->i_lock);
241         }
242 }
243
244 static int shmem_reserve_inode(struct super_block *sb)
245 {
246         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
247         if (sbinfo->max_inodes) {
248                 spin_lock(&sbinfo->stat_lock);
249                 if (!sbinfo->free_inodes) {
250                         spin_unlock(&sbinfo->stat_lock);
251                         return -ENOSPC;
252                 }
253                 sbinfo->free_inodes--;
254                 spin_unlock(&sbinfo->stat_lock);
255         }
256         return 0;
257 }
258
259 static void shmem_free_inode(struct super_block *sb)
260 {
261         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
262         if (sbinfo->max_inodes) {
263                 spin_lock(&sbinfo->stat_lock);
264                 sbinfo->free_inodes++;
265                 spin_unlock(&sbinfo->stat_lock);
266         }
267 }
268
269 /**
270  * shmem_recalc_inode - recalculate the size of an inode
271  * @inode: inode to recalc
272  *
273  * We have to calculate the free blocks since the mm can drop
274  * undirtied hole pages behind our back.
275  *
276  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
277  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
278  *
279  * It has to be called with the spinlock held.
280  */
281 static void shmem_recalc_inode(struct inode *inode)
282 {
283         struct shmem_inode_info *info = SHMEM_I(inode);
284         long freed;
285
286         freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
287         if (freed > 0) {
288                 info->alloced -= freed;
289                 shmem_unacct_blocks(info->flags, freed);
290                 shmem_free_blocks(inode, freed);
291         }
292 }
293
294 /**
295  * shmem_swp_entry - find the swap vector position in the info structure
296  * @info:  info structure for the inode
297  * @index: index of the page to find
298  * @page:  optional page to add to the structure. Has to be preset to
299  *         all zeros
300  *
301  * If there is no space allocated yet it will return NULL when
302  * page is NULL, else it will use the page for the needed block,
303  * setting it to NULL on return to indicate that it has been used.
304  *
305  * The swap vector is organized the following way:
306  *
307  * There are SHMEM_NR_DIRECT entries directly stored in the
308  * shmem_inode_info structure. So small files do not need an addional
309  * allocation.
310  *
311  * For pages with index > SHMEM_NR_DIRECT there is the pointer
312  * i_indirect which points to a page which holds in the first half
313  * doubly indirect blocks, in the second half triple indirect blocks:
314  *
315  * For an artificial ENTRIES_PER_PAGE = 4 this would lead to the
316  * following layout (for SHMEM_NR_DIRECT == 16):
317  *
318  * i_indirect -> dir --> 16-19
319  *            |      +-> 20-23
320  *            |
321  *            +-->dir2 --> 24-27
322  *            |        +-> 28-31
323  *            |        +-> 32-35
324  *            |        +-> 36-39
325  *            |
326  *            +-->dir3 --> 40-43
327  *                     +-> 44-47
328  *                     +-> 48-51
329  *                     +-> 52-55
330  */
331 static swp_entry_t *shmem_swp_entry(struct shmem_inode_info *info, unsigned long index, struct page **page)
332 {
333         unsigned long offset;
334         struct page **dir;
335         struct page *subdir;
336
337         if (index < SHMEM_NR_DIRECT) {
338                 shmem_swp_balance_unmap();
339                 return info->i_direct+index;
340         }
341         if (!info->i_indirect) {
342                 if (page) {
343                         info->i_indirect = *page;
344                         *page = NULL;
345                 }
346                 return NULL;                    /* need another page */
347         }
348
349         index -= SHMEM_NR_DIRECT;
350         offset = index % ENTRIES_PER_PAGE;
351         index /= ENTRIES_PER_PAGE;
352         dir = shmem_dir_map(info->i_indirect);
353
354         if (index >= ENTRIES_PER_PAGE/2) {
355                 index -= ENTRIES_PER_PAGE/2;
356                 dir += ENTRIES_PER_PAGE/2 + index/ENTRIES_PER_PAGE;
357                 index %= ENTRIES_PER_PAGE;
358                 subdir = *dir;
359                 if (!subdir) {
360                         if (page) {
361                                 *dir = *page;
362                                 *page = NULL;
363                         }
364                         shmem_dir_unmap(dir);
365                         return NULL;            /* need another page */
366                 }
367                 shmem_dir_unmap(dir);
368                 dir = shmem_dir_map(subdir);
369         }
370
371         dir += index;
372         subdir = *dir;
373         if (!subdir) {
374                 if (!page || !(subdir = *page)) {
375                         shmem_dir_unmap(dir);
376                         return NULL;            /* need a page */
377                 }
378                 *dir = subdir;
379                 *page = NULL;
380         }
381         shmem_dir_unmap(dir);
382         return shmem_swp_map(subdir) + offset;
383 }
384
385 static void shmem_swp_set(struct shmem_inode_info *info, swp_entry_t *entry, unsigned long value)
386 {
387         long incdec = value? 1: -1;
388
389         entry->val = value;
390         info->swapped += incdec;
391         if ((unsigned long)(entry - info->i_direct) >= SHMEM_NR_DIRECT) {
392                 struct page *page = kmap_atomic_to_page(entry);
393                 set_page_private(page, page_private(page) + incdec);
394         }
395 }
396
397 /**
398  * shmem_swp_alloc - get the position of the swap entry for the page.
399  * @info:       info structure for the inode
400  * @index:      index of the page to find
401  * @sgp:        check and recheck i_size? skip allocation?
402  *
403  * If the entry does not exist, allocate it.
404  */
405 static swp_entry_t *shmem_swp_alloc(struct shmem_inode_info *info, unsigned long index, enum sgp_type sgp)
406 {
407         struct inode *inode = &info->vfs_inode;
408         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
409         struct page *page = NULL;
410         swp_entry_t *entry;
411
412         if (sgp != SGP_WRITE &&
413             ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode))
414                 return ERR_PTR(-EINVAL);
415
416         while (!(entry = shmem_swp_entry(info, index, &page))) {
417                 if (sgp == SGP_READ)
418                         return shmem_swp_map(ZERO_PAGE(0));
419                 /*
420                  * Test used_blocks against 1 less max_blocks, since we have 1 data
421                  * page (and perhaps indirect index pages) yet to allocate:
422                  * a waste to allocate index if we cannot allocate data.
423                  */
424                 if (sbinfo->max_blocks) {
425                         if (percpu_counter_compare(&sbinfo->used_blocks, (sbinfo->max_blocks - 1)) > 0)
426                                 return ERR_PTR(-ENOSPC);
427                         percpu_counter_inc(&sbinfo->used_blocks);
428                         spin_lock(&inode->i_lock);
429                         inode->i_blocks += BLOCKS_PER_PAGE;
430                         spin_unlock(&inode->i_lock);
431                 }
432
433                 spin_unlock(&info->lock);
434                 page = shmem_dir_alloc(mapping_gfp_mask(inode->i_mapping));
435                 spin_lock(&info->lock);
436
437                 if (!page) {
438                         shmem_free_blocks(inode, 1);
439                         return ERR_PTR(-ENOMEM);
440                 }
441                 if (sgp != SGP_WRITE &&
442                     ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
443                         entry = ERR_PTR(-EINVAL);
444                         break;
445                 }
446                 if (info->next_index <= index)
447                         info->next_index = index + 1;
448         }
449         if (page) {
450                 /* another task gave its page, or truncated the file */
451                 shmem_free_blocks(inode, 1);
452                 shmem_dir_free(page);
453         }
454         if (info->next_index <= index && !IS_ERR(entry))
455                 info->next_index = index + 1;
456         return entry;
457 }
458
459 /**
460  * shmem_free_swp - free some swap entries in a directory
461  * @dir:        pointer to the directory
462  * @edir:       pointer after last entry of the directory
463  * @punch_lock: pointer to spinlock when needed for the holepunch case
464  */
465 static int shmem_free_swp(swp_entry_t *dir, swp_entry_t *edir,
466                                                 spinlock_t *punch_lock)
467 {
468         spinlock_t *punch_unlock = NULL;
469         swp_entry_t *ptr;
470         int freed = 0;
471
472         for (ptr = dir; ptr < edir; ptr++) {
473                 if (ptr->val) {
474                         if (unlikely(punch_lock)) {
475                                 punch_unlock = punch_lock;
476                                 punch_lock = NULL;
477                                 spin_lock(punch_unlock);
478                                 if (!ptr->val)
479                                         continue;
480                         }
481                         free_swap_and_cache(*ptr);
482                         *ptr = (swp_entry_t){0};
483                         freed++;
484                 }
485         }
486         if (punch_unlock)
487                 spin_unlock(punch_unlock);
488         return freed;
489 }
490
491 static int shmem_map_and_free_swp(struct page *subdir, int offset,
492                 int limit, struct page ***dir, spinlock_t *punch_lock)
493 {
494         swp_entry_t *ptr;
495         int freed = 0;
496
497         ptr = shmem_swp_map(subdir);
498         for (; offset < limit; offset += LATENCY_LIMIT) {
499                 int size = limit - offset;
500                 if (size > LATENCY_LIMIT)
501                         size = LATENCY_LIMIT;
502                 freed += shmem_free_swp(ptr+offset, ptr+offset+size,
503                                                         punch_lock);
504                 if (need_resched()) {
505                         shmem_swp_unmap(ptr);
506                         if (*dir) {
507                                 shmem_dir_unmap(*dir);
508                                 *dir = NULL;
509                         }
510                         cond_resched();
511                         ptr = shmem_swp_map(subdir);
512                 }
513         }
514         shmem_swp_unmap(ptr);
515         return freed;
516 }
517
518 static void shmem_free_pages(struct list_head *next)
519 {
520         struct page *page;
521         int freed = 0;
522
523         do {
524                 page = container_of(next, struct page, lru);
525                 next = next->next;
526                 shmem_dir_free(page);
527                 freed++;
528                 if (freed >= LATENCY_LIMIT) {
529                         cond_resched();
530                         freed = 0;
531                 }
532         } while (next);
533 }
534
535 static void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end)
536 {
537         struct shmem_inode_info *info = SHMEM_I(inode);
538         unsigned long idx;
539         unsigned long size;
540         unsigned long limit;
541         unsigned long stage;
542         unsigned long diroff;
543         struct page **dir;
544         struct page *topdir;
545         struct page *middir;
546         struct page *subdir;
547         swp_entry_t *ptr;
548         LIST_HEAD(pages_to_free);
549         long nr_pages_to_free = 0;
550         long nr_swaps_freed = 0;
551         int offset;
552         int freed;
553         int punch_hole;
554         spinlock_t *needs_lock;
555         spinlock_t *punch_lock;
556         unsigned long upper_limit;
557
558         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
559         idx = (start + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
560         if (idx >= info->next_index)
561                 return;
562
563         spin_lock(&info->lock);
564         info->flags |= SHMEM_TRUNCATE;
565         if (likely(end == (loff_t) -1)) {
566                 limit = info->next_index;
567                 upper_limit = SHMEM_MAX_INDEX;
568                 info->next_index = idx;
569                 needs_lock = NULL;
570                 punch_hole = 0;
571         } else {
572                 if (end + 1 >= inode->i_size) { /* we may free a little more */
573                         limit = (inode->i_size + PAGE_CACHE_SIZE - 1) >>
574                                                         PAGE_CACHE_SHIFT;
575                         upper_limit = SHMEM_MAX_INDEX;
576                 } else {
577                         limit = (end + 1) >> PAGE_CACHE_SHIFT;
578                         upper_limit = limit;
579                 }
580                 needs_lock = &info->lock;
581                 punch_hole = 1;
582         }
583
584         topdir = info->i_indirect;
585         if (topdir && idx <= SHMEM_NR_DIRECT && !punch_hole) {
586                 info->i_indirect = NULL;
587                 nr_pages_to_free++;
588                 list_add(&topdir->lru, &pages_to_free);
589         }
590         spin_unlock(&info->lock);
591
592         if (info->swapped && idx < SHMEM_NR_DIRECT) {
593                 ptr = info->i_direct;
594                 size = limit;
595                 if (size > SHMEM_NR_DIRECT)
596                         size = SHMEM_NR_DIRECT;
597                 nr_swaps_freed = shmem_free_swp(ptr+idx, ptr+size, needs_lock);
598         }
599
600         /*
601          * If there are no indirect blocks or we are punching a hole
602          * below indirect blocks, nothing to be done.
603          */
604         if (!topdir || limit <= SHMEM_NR_DIRECT)
605                 goto done2;
606
607         /*
608          * The truncation case has already dropped info->lock, and we're safe
609          * because i_size and next_index have already been lowered, preventing
610          * access beyond.  But in the punch_hole case, we still need to take
611          * the lock when updating the swap directory, because there might be
612          * racing accesses by shmem_getpage(SGP_CACHE), shmem_unuse_inode or
613          * shmem_writepage.  However, whenever we find we can remove a whole
614          * directory page (not at the misaligned start or end of the range),
615          * we first NULLify its pointer in the level above, and then have no
616          * need to take the lock when updating its contents: needs_lock and
617          * punch_lock (either pointing to info->lock or NULL) manage this.
618          */
619
620         upper_limit -= SHMEM_NR_DIRECT;
621         limit -= SHMEM_NR_DIRECT;
622         idx = (idx > SHMEM_NR_DIRECT)? (idx - SHMEM_NR_DIRECT): 0;
623         offset = idx % ENTRIES_PER_PAGE;
624         idx -= offset;
625
626         dir = shmem_dir_map(topdir);
627         stage = ENTRIES_PER_PAGEPAGE/2;
628         if (idx < ENTRIES_PER_PAGEPAGE/2) {
629                 middir = topdir;
630                 diroff = idx/ENTRIES_PER_PAGE;
631         } else {
632                 dir += ENTRIES_PER_PAGE/2;
633                 dir += (idx - ENTRIES_PER_PAGEPAGE/2)/ENTRIES_PER_PAGEPAGE;
634                 while (stage <= idx)
635                         stage += ENTRIES_PER_PAGEPAGE;
636                 middir = *dir;
637                 if (*dir) {
638                         diroff = ((idx - ENTRIES_PER_PAGEPAGE/2) %
639                                 ENTRIES_PER_PAGEPAGE) / ENTRIES_PER_PAGE;
640                         if (!diroff && !offset && upper_limit >= stage) {
641                                 if (needs_lock) {
642                                         spin_lock(needs_lock);
643                                         *dir = NULL;
644                                         spin_unlock(needs_lock);
645                                         needs_lock = NULL;
646                                 } else
647                                         *dir = NULL;
648                                 nr_pages_to_free++;
649                                 list_add(&middir->lru, &pages_to_free);
650                         }
651                         shmem_dir_unmap(dir);
652                         dir = shmem_dir_map(middir);
653                 } else {
654                         diroff = 0;
655                         offset = 0;
656                         idx = stage;
657                 }
658         }
659
660         for (; idx < limit; idx += ENTRIES_PER_PAGE, diroff++) {
661                 if (unlikely(idx == stage)) {
662                         shmem_dir_unmap(dir);
663                         dir = shmem_dir_map(topdir) +
664                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
665                         while (!*dir) {
666                                 dir++;
667                                 idx += ENTRIES_PER_PAGEPAGE;
668                                 if (idx >= limit)
669                                         goto done1;
670                         }
671                         stage = idx + ENTRIES_PER_PAGEPAGE;
672                         middir = *dir;
673                         if (punch_hole)
674                                 needs_lock = &info->lock;
675                         if (upper_limit >= stage) {
676                                 if (needs_lock) {
677                                         spin_lock(needs_lock);
678                                         *dir = NULL;
679                                         spin_unlock(needs_lock);
680                                         needs_lock = NULL;
681                                 } else
682                                         *dir = NULL;
683                                 nr_pages_to_free++;
684                                 list_add(&middir->lru, &pages_to_free);
685                         }
686                         shmem_dir_unmap(dir);
687                         cond_resched();
688                         dir = shmem_dir_map(middir);
689                         diroff = 0;
690                 }
691                 punch_lock = needs_lock;
692                 subdir = dir[diroff];
693                 if (subdir && !offset && upper_limit-idx >= ENTRIES_PER_PAGE) {
694                         if (needs_lock) {
695                                 spin_lock(needs_lock);
696                                 dir[diroff] = NULL;
697                                 spin_unlock(needs_lock);
698                                 punch_lock = NULL;
699                         } else
700                                 dir[diroff] = NULL;
701                         nr_pages_to_free++;
702                         list_add(&subdir->lru, &pages_to_free);
703                 }
704                 if (subdir && page_private(subdir) /* has swap entries */) {
705                         size = limit - idx;
706                         if (size > ENTRIES_PER_PAGE)
707                                 size = ENTRIES_PER_PAGE;
708                         freed = shmem_map_and_free_swp(subdir,
709                                         offset, size, &dir, punch_lock);
710                         if (!dir)
711                                 dir = shmem_dir_map(middir);
712                         nr_swaps_freed += freed;
713                         if (offset || punch_lock) {
714                                 spin_lock(&info->lock);
715                                 set_page_private(subdir,
716                                         page_private(subdir) - freed);
717                                 spin_unlock(&info->lock);
718                         } else
719                                 BUG_ON(page_private(subdir) != freed);
720                 }
721                 offset = 0;
722         }
723 done1:
724         shmem_dir_unmap(dir);
725 done2:
726         if (inode->i_mapping->nrpages && (info->flags & SHMEM_PAGEIN)) {
727                 /*
728                  * Call truncate_inode_pages again: racing shmem_unuse_inode
729                  * may have swizzled a page in from swap since
730                  * truncate_pagecache or generic_delete_inode did it, before we
731                  * lowered next_index.  Also, though shmem_getpage checks
732                  * i_size before adding to cache, no recheck after: so fix the
733                  * narrow window there too.
734                  *
735                  * Recalling truncate_inode_pages_range and unmap_mapping_range
736                  * every time for punch_hole (which never got a chance to clear
737                  * SHMEM_PAGEIN at the start of vmtruncate_range) is expensive,
738                  * yet hardly ever necessary: try to optimize them out later.
739                  */
740                 truncate_inode_pages_range(inode->i_mapping, start, end);
741                 if (punch_hole)
742                         unmap_mapping_range(inode->i_mapping, start,
743                                                         end - start, 1);
744         }
745
746         spin_lock(&info->lock);
747         info->flags &= ~SHMEM_TRUNCATE;
748         info->swapped -= nr_swaps_freed;
749         if (nr_pages_to_free)
750                 shmem_free_blocks(inode, nr_pages_to_free);
751         shmem_recalc_inode(inode);
752         spin_unlock(&info->lock);
753
754         /*
755          * Empty swap vector directory pages to be freed?
756          */
757         if (!list_empty(&pages_to_free)) {
758                 pages_to_free.prev->next = NULL;
759                 shmem_free_pages(pages_to_free.next);
760         }
761 }
762
763 static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
764 {
765         struct inode *inode = dentry->d_inode;
766         loff_t newsize = attr->ia_size;
767         int error;
768
769         error = inode_change_ok(inode, attr);
770         if (error)
771                 return error;
772
773         if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)
774                                         && newsize != inode->i_size) {
775                 struct page *page = NULL;
776
777                 if (newsize < inode->i_size) {
778                         /*
779                          * If truncating down to a partial page, then
780                          * if that page is already allocated, hold it
781                          * in memory until the truncation is over, so
782                          * truncate_partial_page cannnot miss it were
783                          * it assigned to swap.
784                          */
785                         if (newsize & (PAGE_CACHE_SIZE-1)) {
786                                 (void) shmem_getpage(inode,
787                                         newsize >> PAGE_CACHE_SHIFT,
788                                                 &page, SGP_READ, NULL);
789                                 if (page)
790                                         unlock_page(page);
791                         }
792                         /*
793                          * Reset SHMEM_PAGEIN flag so that shmem_truncate can
794                          * detect if any pages might have been added to cache
795                          * after truncate_inode_pages.  But we needn't bother
796                          * if it's being fully truncated to zero-length: the
797                          * nrpages check is efficient enough in that case.
798                          */
799                         if (newsize) {
800                                 struct shmem_inode_info *info = SHMEM_I(inode);
801                                 spin_lock(&info->lock);
802                                 info->flags &= ~SHMEM_PAGEIN;
803                                 spin_unlock(&info->lock);
804                         }
805                 }
806
807                 /* XXX(truncate): truncate_setsize should be called last */
808                 truncate_setsize(inode, newsize);
809                 if (page)
810                         page_cache_release(page);
811                 shmem_truncate_range(inode, newsize, (loff_t)-1);
812         }
813
814         setattr_copy(inode, attr);
815 #ifdef CONFIG_TMPFS_POSIX_ACL
816         if (attr->ia_valid & ATTR_MODE)
817                 error = generic_acl_chmod(inode);
818 #endif
819         return error;
820 }
821
822 static void shmem_evict_inode(struct inode *inode)
823 {
824         struct shmem_inode_info *info = SHMEM_I(inode);
825
826         if (inode->i_mapping->a_ops == &shmem_aops) {
827                 truncate_inode_pages(inode->i_mapping, 0);
828                 shmem_unacct_size(info->flags, inode->i_size);
829                 inode->i_size = 0;
830                 shmem_truncate_range(inode, 0, (loff_t)-1);
831                 if (!list_empty(&info->swaplist)) {
832                         mutex_lock(&shmem_swaplist_mutex);
833                         list_del_init(&info->swaplist);
834                         mutex_unlock(&shmem_swaplist_mutex);
835                 }
836         }
837         BUG_ON(inode->i_blocks);
838         shmem_free_inode(inode->i_sb);
839         end_writeback(inode);
840 }
841
842 static inline int shmem_find_swp(swp_entry_t entry, swp_entry_t *dir, swp_entry_t *edir)
843 {
844         swp_entry_t *ptr;
845
846         for (ptr = dir; ptr < edir; ptr++) {
847                 if (ptr->val == entry.val)
848                         return ptr - dir;
849         }
850         return -1;
851 }
852
853 static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t entry, struct page *page)
854 {
855         struct inode *inode;
856         unsigned long idx;
857         unsigned long size;
858         unsigned long limit;
859         unsigned long stage;
860         struct page **dir;
861         struct page *subdir;
862         swp_entry_t *ptr;
863         int offset;
864         int error;
865
866         idx = 0;
867         ptr = info->i_direct;
868         spin_lock(&info->lock);
869         if (!info->swapped) {
870                 list_del_init(&info->swaplist);
871                 goto lost2;
872         }
873         limit = info->next_index;
874         size = limit;
875         if (size > SHMEM_NR_DIRECT)
876                 size = SHMEM_NR_DIRECT;
877         offset = shmem_find_swp(entry, ptr, ptr+size);
878         if (offset >= 0)
879                 goto found;
880         if (!info->i_indirect)
881                 goto lost2;
882
883         dir = shmem_dir_map(info->i_indirect);
884         stage = SHMEM_NR_DIRECT + ENTRIES_PER_PAGEPAGE/2;
885
886         for (idx = SHMEM_NR_DIRECT; idx < limit; idx += ENTRIES_PER_PAGE, dir++) {
887                 if (unlikely(idx == stage)) {
888                         shmem_dir_unmap(dir-1);
889                         if (cond_resched_lock(&info->lock)) {
890                                 /* check it has not been truncated */
891                                 if (limit > info->next_index) {
892                                         limit = info->next_index;
893                                         if (idx >= limit)
894                                                 goto lost2;
895                                 }
896                         }
897                         dir = shmem_dir_map(info->i_indirect) +
898                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
899                         while (!*dir) {
900                                 dir++;
901                                 idx += ENTRIES_PER_PAGEPAGE;
902                                 if (idx >= limit)
903                                         goto lost1;
904                         }
905                         stage = idx + ENTRIES_PER_PAGEPAGE;
906                         subdir = *dir;
907                         shmem_dir_unmap(dir);
908                         dir = shmem_dir_map(subdir);
909                 }
910                 subdir = *dir;
911                 if (subdir && page_private(subdir)) {
912                         ptr = shmem_swp_map(subdir);
913                         size = limit - idx;
914                         if (size > ENTRIES_PER_PAGE)
915                                 size = ENTRIES_PER_PAGE;
916                         offset = shmem_find_swp(entry, ptr, ptr+size);
917                         shmem_swp_unmap(ptr);
918                         if (offset >= 0) {
919                                 shmem_dir_unmap(dir);
920                                 goto found;
921                         }
922                 }
923         }
924 lost1:
925         shmem_dir_unmap(dir-1);
926 lost2:
927         spin_unlock(&info->lock);
928         return 0;
929 found:
930         idx += offset;
931         inode = igrab(&info->vfs_inode);
932         spin_unlock(&info->lock);
933
934         /*
935          * Move _head_ to start search for next from here.
936          * But be careful: shmem_evict_inode checks list_empty without taking
937          * mutex, and there's an instant in list_move_tail when info->swaplist
938          * would appear empty, if it were the only one on shmem_swaplist.  We
939          * could avoid doing it if inode NULL; or use this minor optimization.
940          */
941         if (shmem_swaplist.next != &info->swaplist)
942                 list_move_tail(&shmem_swaplist, &info->swaplist);
943         mutex_unlock(&shmem_swaplist_mutex);
944
945         error = 1;
946         if (!inode)
947                 goto out;
948         /*
949          * Charge page using GFP_KERNEL while we can wait.
950          * Charged back to the user(not to caller) when swap account is used.
951          * add_to_page_cache() will be called with GFP_NOWAIT.
952          */
953         error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL);
954         if (error)
955                 goto out;
956         error = radix_tree_preload(GFP_KERNEL);
957         if (error) {
958                 mem_cgroup_uncharge_cache_page(page);
959                 goto out;
960         }
961         error = 1;
962
963         spin_lock(&info->lock);
964         ptr = shmem_swp_entry(info, idx, NULL);
965         if (ptr && ptr->val == entry.val) {
966                 error = add_to_page_cache_locked(page, inode->i_mapping,
967                                                 idx, GFP_NOWAIT);
968                 /* does mem_cgroup_uncharge_cache_page on error */
969         } else  /* we must compensate for our precharge above */
970                 mem_cgroup_uncharge_cache_page(page);
971
972         if (error == -EEXIST) {
973                 struct page *filepage = find_get_page(inode->i_mapping, idx);
974                 error = 1;
975                 if (filepage) {
976                         /*
977                          * There might be a more uptodate page coming down
978                          * from a stacked writepage: forget our swappage if so.
979                          */
980                         if (PageUptodate(filepage))
981                                 error = 0;
982                         page_cache_release(filepage);
983                 }
984         }
985         if (!error) {
986                 delete_from_swap_cache(page);
987                 set_page_dirty(page);
988                 info->flags |= SHMEM_PAGEIN;
989                 shmem_swp_set(info, ptr, 0);
990                 swap_free(entry);
991                 error = 1;      /* not an error, but entry was found */
992         }
993         if (ptr)
994                 shmem_swp_unmap(ptr);
995         spin_unlock(&info->lock);
996         radix_tree_preload_end();
997 out:
998         unlock_page(page);
999         page_cache_release(page);
1000         iput(inode);            /* allows for NULL */
1001         return error;
1002 }
1003
1004 /*
1005  * shmem_unuse() search for an eventually swapped out shmem page.
1006  */
1007 int shmem_unuse(swp_entry_t entry, struct page *page)
1008 {
1009         struct list_head *p, *next;
1010         struct shmem_inode_info *info;
1011         int found = 0;
1012
1013         mutex_lock(&shmem_swaplist_mutex);
1014         list_for_each_safe(p, next, &shmem_swaplist) {
1015                 info = list_entry(p, struct shmem_inode_info, swaplist);
1016                 found = shmem_unuse_inode(info, entry, page);
1017                 cond_resched();
1018                 if (found)
1019                         goto out;
1020         }
1021         mutex_unlock(&shmem_swaplist_mutex);
1022         /*
1023          * Can some race bring us here?  We've been holding page lock,
1024          * so I think not; but would rather try again later than BUG()
1025          */
1026         unlock_page(page);
1027         page_cache_release(page);
1028 out:
1029         return (found < 0) ? found : 0;
1030 }
1031
1032 /*
1033  * Move the page from the page cache to the swap cache.
1034  */
1035 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
1036 {
1037         struct shmem_inode_info *info;
1038         swp_entry_t *entry, swap;
1039         struct address_space *mapping;
1040         unsigned long index;
1041         struct inode *inode;
1042
1043         BUG_ON(!PageLocked(page));
1044         mapping = page->mapping;
1045         index = page->index;
1046         inode = mapping->host;
1047         info = SHMEM_I(inode);
1048         if (info->flags & VM_LOCKED)
1049                 goto redirty;
1050         if (!total_swap_pages)
1051                 goto redirty;
1052
1053         /*
1054          * shmem_backing_dev_info's capabilities prevent regular writeback or
1055          * sync from ever calling shmem_writepage; but a stacking filesystem
1056          * may use the ->writepage of its underlying filesystem, in which case
1057          * tmpfs should write out to swap only in response to memory pressure,
1058          * and not for the writeback threads or sync.  However, in those cases,
1059          * we do still want to check if there's a redundant swappage to be
1060          * discarded.
1061          */
1062         if (wbc->for_reclaim)
1063                 swap = get_swap_page();
1064         else
1065                 swap.val = 0;
1066
1067         spin_lock(&info->lock);
1068         if (index >= info->next_index) {
1069                 BUG_ON(!(info->flags & SHMEM_TRUNCATE));
1070                 goto unlock;
1071         }
1072         entry = shmem_swp_entry(info, index, NULL);
1073         if (entry->val) {
1074                 /*
1075                  * The more uptodate page coming down from a stacked
1076                  * writepage should replace our old swappage.
1077                  */
1078                 free_swap_and_cache(*entry);
1079                 shmem_swp_set(info, entry, 0);
1080         }
1081         shmem_recalc_inode(inode);
1082
1083         if (swap.val && add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
1084                 remove_from_page_cache(page);
1085                 shmem_swp_set(info, entry, swap.val);
1086                 shmem_swp_unmap(entry);
1087                 if (list_empty(&info->swaplist))
1088                         inode = igrab(inode);
1089                 else
1090                         inode = NULL;
1091                 spin_unlock(&info->lock);
1092                 swap_shmem_alloc(swap);
1093                 BUG_ON(page_mapped(page));
1094                 page_cache_release(page);       /* pagecache ref */
1095                 swap_writepage(page, wbc);
1096                 if (inode) {
1097                         mutex_lock(&shmem_swaplist_mutex);
1098                         /* move instead of add in case we're racing */
1099                         list_move_tail(&info->swaplist, &shmem_swaplist);
1100                         mutex_unlock(&shmem_swaplist_mutex);
1101                         iput(inode);
1102                 }
1103                 return 0;
1104         }
1105
1106         shmem_swp_unmap(entry);
1107 unlock:
1108         spin_unlock(&info->lock);
1109         /*
1110          * add_to_swap_cache() doesn't return -EEXIST, so we can safely
1111          * clear SWAP_HAS_CACHE flag.
1112          */
1113         swapcache_free(swap, NULL);
1114 redirty:
1115         set_page_dirty(page);
1116         if (wbc->for_reclaim)
1117                 return AOP_WRITEPAGE_ACTIVATE;  /* Return with page locked */
1118         unlock_page(page);
1119         return 0;
1120 }
1121
1122 #ifdef CONFIG_NUMA
1123 #ifdef CONFIG_TMPFS
1124 static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1125 {
1126         char buffer[64];
1127
1128         if (!mpol || mpol->mode == MPOL_DEFAULT)
1129                 return;         /* show nothing */
1130
1131         mpol_to_str(buffer, sizeof(buffer), mpol, 1);
1132
1133         seq_printf(seq, ",mpol=%s", buffer);
1134 }
1135
1136 static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1137 {
1138         struct mempolicy *mpol = NULL;
1139         if (sbinfo->mpol) {
1140                 spin_lock(&sbinfo->stat_lock);  /* prevent replace/use races */
1141                 mpol = sbinfo->mpol;
1142                 mpol_get(mpol);
1143                 spin_unlock(&sbinfo->stat_lock);
1144         }
1145         return mpol;
1146 }
1147 #endif /* CONFIG_TMPFS */
1148
1149 static struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
1150                         struct shmem_inode_info *info, unsigned long idx)
1151 {
1152         struct mempolicy mpol, *spol;
1153         struct vm_area_struct pvma;
1154         struct page *page;
1155
1156         spol = mpol_cond_copy(&mpol,
1157                                 mpol_shared_policy_lookup(&info->policy, idx));
1158
1159         /* Create a pseudo vma that just contains the policy */
1160         pvma.vm_start = 0;
1161         pvma.vm_pgoff = idx;
1162         pvma.vm_ops = NULL;
1163         pvma.vm_policy = spol;
1164         page = swapin_readahead(entry, gfp, &pvma, 0);
1165         return page;
1166 }
1167
1168 static struct page *shmem_alloc_page(gfp_t gfp,
1169                         struct shmem_inode_info *info, unsigned long idx)
1170 {
1171         struct vm_area_struct pvma;
1172
1173         /* Create a pseudo vma that just contains the policy */
1174         pvma.vm_start = 0;
1175         pvma.vm_pgoff = idx;
1176         pvma.vm_ops = NULL;
1177         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
1178
1179         /*
1180          * alloc_page_vma() will drop the shared policy reference
1181          */
1182         return alloc_page_vma(gfp, &pvma, 0);
1183 }
1184 #else /* !CONFIG_NUMA */
1185 #ifdef CONFIG_TMPFS
1186 static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *p)
1187 {
1188 }
1189 #endif /* CONFIG_TMPFS */
1190
1191 static inline struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
1192                         struct shmem_inode_info *info, unsigned long idx)
1193 {
1194         return swapin_readahead(entry, gfp, NULL, 0);
1195 }
1196
1197 static inline struct page *shmem_alloc_page(gfp_t gfp,
1198                         struct shmem_inode_info *info, unsigned long idx)
1199 {
1200         return alloc_page(gfp);
1201 }
1202 #endif /* CONFIG_NUMA */
1203
1204 #if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS)
1205 static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1206 {
1207         return NULL;
1208 }
1209 #endif
1210
1211 /*
1212  * shmem_getpage - either get the page from swap or allocate a new one
1213  *
1214  * If we allocate a new one we do not mark it dirty. That's up to the
1215  * vm. If we swap it in we mark it dirty since we also free the swap
1216  * entry since a page cannot live in both the swap and page cache
1217  */
1218 static int shmem_getpage(struct inode *inode, unsigned long idx,
1219                         struct page **pagep, enum sgp_type sgp, int *type)
1220 {
1221         struct address_space *mapping = inode->i_mapping;
1222         struct shmem_inode_info *info = SHMEM_I(inode);
1223         struct shmem_sb_info *sbinfo;
1224         struct page *filepage = *pagep;
1225         struct page *swappage;
1226         struct page *prealloc_page = NULL;
1227         swp_entry_t *entry;
1228         swp_entry_t swap;
1229         gfp_t gfp;
1230         int error;
1231
1232         if (idx >= SHMEM_MAX_INDEX)
1233                 return -EFBIG;
1234
1235         if (type)
1236                 *type = 0;
1237
1238         /*
1239          * Normally, filepage is NULL on entry, and either found
1240          * uptodate immediately, or allocated and zeroed, or read
1241          * in under swappage, which is then assigned to filepage.
1242          * But shmem_readpage (required for splice) passes in a locked
1243          * filepage, which may be found not uptodate by other callers
1244          * too, and may need to be copied from the swappage read in.
1245          */
1246 repeat:
1247         if (!filepage)
1248                 filepage = find_lock_page(mapping, idx);
1249         if (filepage && PageUptodate(filepage))
1250                 goto done;
1251         gfp = mapping_gfp_mask(mapping);
1252         if (!filepage) {
1253                 /*
1254                  * Try to preload while we can wait, to not make a habit of
1255                  * draining atomic reserves; but don't latch on to this cpu.
1256                  */
1257                 error = radix_tree_preload(gfp & ~__GFP_HIGHMEM);
1258                 if (error)
1259                         goto failed;
1260                 radix_tree_preload_end();
1261                 if (sgp != SGP_READ && !prealloc_page) {
1262                         /* We don't care if this fails */
1263                         prealloc_page = shmem_alloc_page(gfp, info, idx);
1264                         if (prealloc_page) {
1265                                 if (mem_cgroup_cache_charge(prealloc_page,
1266                                                 current->mm, GFP_KERNEL)) {
1267                                         page_cache_release(prealloc_page);
1268                                         prealloc_page = NULL;
1269                                 }
1270                         }
1271                 }
1272         }
1273         error = 0;
1274
1275         spin_lock(&info->lock);
1276         shmem_recalc_inode(inode);
1277         entry = shmem_swp_alloc(info, idx, sgp);
1278         if (IS_ERR(entry)) {
1279                 spin_unlock(&info->lock);
1280                 error = PTR_ERR(entry);
1281                 goto failed;
1282         }
1283         swap = *entry;
1284
1285         if (swap.val) {
1286                 /* Look it up and read it in.. */
1287                 swappage = lookup_swap_cache(swap);
1288                 if (!swappage) {
1289                         shmem_swp_unmap(entry);
1290                         /* here we actually do the io */
1291                         if (type && !(*type & VM_FAULT_MAJOR)) {
1292                                 __count_vm_event(PGMAJFAULT);
1293                                 *type |= VM_FAULT_MAJOR;
1294                         }
1295                         spin_unlock(&info->lock);
1296                         swappage = shmem_swapin(swap, gfp, info, idx);
1297                         if (!swappage) {
1298                                 spin_lock(&info->lock);
1299                                 entry = shmem_swp_alloc(info, idx, sgp);
1300                                 if (IS_ERR(entry))
1301                                         error = PTR_ERR(entry);
1302                                 else {
1303                                         if (entry->val == swap.val)
1304                                                 error = -ENOMEM;
1305                                         shmem_swp_unmap(entry);
1306                                 }
1307                                 spin_unlock(&info->lock);
1308                                 if (error)
1309                                         goto failed;
1310                                 goto repeat;
1311                         }
1312                         wait_on_page_locked(swappage);
1313                         page_cache_release(swappage);
1314                         goto repeat;
1315                 }
1316
1317                 /* We have to do this with page locked to prevent races */
1318                 if (!trylock_page(swappage)) {
1319                         shmem_swp_unmap(entry);
1320                         spin_unlock(&info->lock);
1321                         wait_on_page_locked(swappage);
1322                         page_cache_release(swappage);
1323                         goto repeat;
1324                 }
1325                 if (PageWriteback(swappage)) {
1326                         shmem_swp_unmap(entry);
1327                         spin_unlock(&info->lock);
1328                         wait_on_page_writeback(swappage);
1329                         unlock_page(swappage);
1330                         page_cache_release(swappage);
1331                         goto repeat;
1332                 }
1333                 if (!PageUptodate(swappage)) {
1334                         shmem_swp_unmap(entry);
1335                         spin_unlock(&info->lock);
1336                         unlock_page(swappage);
1337                         page_cache_release(swappage);
1338                         error = -EIO;
1339                         goto failed;
1340                 }
1341
1342                 if (filepage) {
1343                         shmem_swp_set(info, entry, 0);
1344                         shmem_swp_unmap(entry);
1345                         delete_from_swap_cache(swappage);
1346                         spin_unlock(&info->lock);
1347                         copy_highpage(filepage, swappage);
1348                         unlock_page(swappage);
1349                         page_cache_release(swappage);
1350                         flush_dcache_page(filepage);
1351                         SetPageUptodate(filepage);
1352                         set_page_dirty(filepage);
1353                         swap_free(swap);
1354                 } else if (!(error = add_to_page_cache_locked(swappage, mapping,
1355                                         idx, GFP_NOWAIT))) {
1356                         info->flags |= SHMEM_PAGEIN;
1357                         shmem_swp_set(info, entry, 0);
1358                         shmem_swp_unmap(entry);
1359                         delete_from_swap_cache(swappage);
1360                         spin_unlock(&info->lock);
1361                         filepage = swappage;
1362                         set_page_dirty(filepage);
1363                         swap_free(swap);
1364                 } else {
1365                         shmem_swp_unmap(entry);
1366                         spin_unlock(&info->lock);
1367                         if (error == -ENOMEM) {
1368                                 /*
1369                                  * reclaim from proper memory cgroup and
1370                                  * call memcg's OOM if needed.
1371                                  */
1372                                 error = mem_cgroup_shmem_charge_fallback(
1373                                                                 swappage,
1374                                                                 current->mm,
1375                                                                 gfp);
1376                                 if (error) {
1377                                         unlock_page(swappage);
1378                                         page_cache_release(swappage);
1379                                         goto failed;
1380                                 }
1381                         }
1382                         unlock_page(swappage);
1383                         page_cache_release(swappage);
1384                         goto repeat;
1385                 }
1386         } else if (sgp == SGP_READ && !filepage) {
1387                 shmem_swp_unmap(entry);
1388                 filepage = find_get_page(mapping, idx);
1389                 if (filepage &&
1390                     (!PageUptodate(filepage) || !trylock_page(filepage))) {
1391                         spin_unlock(&info->lock);
1392                         wait_on_page_locked(filepage);
1393                         page_cache_release(filepage);
1394                         filepage = NULL;
1395                         goto repeat;
1396                 }
1397                 spin_unlock(&info->lock);
1398         } else {
1399                 shmem_swp_unmap(entry);
1400                 sbinfo = SHMEM_SB(inode->i_sb);
1401                 if (sbinfo->max_blocks) {
1402                         if ((percpu_counter_compare(&sbinfo->used_blocks, sbinfo->max_blocks) > 0) ||
1403                             shmem_acct_block(info->flags)) {
1404                                 spin_unlock(&info->lock);
1405                                 error = -ENOSPC;
1406                                 goto failed;
1407                         }
1408                         percpu_counter_inc(&sbinfo->used_blocks);
1409                         spin_lock(&inode->i_lock);
1410                         inode->i_blocks += BLOCKS_PER_PAGE;
1411                         spin_unlock(&inode->i_lock);
1412                 } else if (shmem_acct_block(info->flags)) {
1413                         spin_unlock(&info->lock);
1414                         error = -ENOSPC;
1415                         goto failed;
1416                 }
1417
1418                 if (!filepage) {
1419                         int ret;
1420
1421                         if (!prealloc_page) {
1422                                 spin_unlock(&info->lock);
1423                                 filepage = shmem_alloc_page(gfp, info, idx);
1424                                 if (!filepage) {
1425                                         shmem_unacct_blocks(info->flags, 1);
1426                                         shmem_free_blocks(inode, 1);
1427                                         error = -ENOMEM;
1428                                         goto failed;
1429                                 }
1430                                 SetPageSwapBacked(filepage);
1431
1432                                 /*
1433                                  * Precharge page while we can wait, compensate
1434                                  * after
1435                                  */
1436                                 error = mem_cgroup_cache_charge(filepage,
1437                                         current->mm, GFP_KERNEL);
1438                                 if (error) {
1439                                         page_cache_release(filepage);
1440                                         shmem_unacct_blocks(info->flags, 1);
1441                                         shmem_free_blocks(inode, 1);
1442                                         filepage = NULL;
1443                                         goto failed;
1444                                 }
1445
1446                                 spin_lock(&info->lock);
1447                         } else {
1448                                 filepage = prealloc_page;
1449                                 prealloc_page = NULL;
1450                                 SetPageSwapBacked(filepage);
1451                         }
1452
1453                         entry = shmem_swp_alloc(info, idx, sgp);
1454                         if (IS_ERR(entry))
1455                                 error = PTR_ERR(entry);
1456                         else {
1457                                 swap = *entry;
1458                                 shmem_swp_unmap(entry);
1459                         }
1460                         ret = error || swap.val;
1461                         if (ret)
1462                                 mem_cgroup_uncharge_cache_page(filepage);
1463                         else
1464                                 ret = add_to_page_cache_lru(filepage, mapping,
1465                                                 idx, GFP_NOWAIT);
1466                         /*
1467                          * At add_to_page_cache_lru() failure, uncharge will
1468                          * be done automatically.
1469                          */
1470                         if (ret) {
1471                                 spin_unlock(&info->lock);
1472                                 page_cache_release(filepage);
1473                                 shmem_unacct_blocks(info->flags, 1);
1474                                 shmem_free_blocks(inode, 1);
1475                                 filepage = NULL;
1476                                 if (error)
1477                                         goto failed;
1478                                 goto repeat;
1479                         }
1480                         info->flags |= SHMEM_PAGEIN;
1481                 }
1482
1483                 info->alloced++;
1484                 spin_unlock(&info->lock);
1485                 clear_highpage(filepage);
1486                 flush_dcache_page(filepage);
1487                 SetPageUptodate(filepage);
1488                 if (sgp == SGP_DIRTY)
1489                         set_page_dirty(filepage);
1490         }
1491 done:
1492         *pagep = filepage;
1493         error = 0;
1494         goto out;
1495
1496 failed:
1497         if (*pagep != filepage) {
1498                 unlock_page(filepage);
1499                 page_cache_release(filepage);
1500         }
1501 out:
1502         if (prealloc_page) {
1503                 mem_cgroup_uncharge_cache_page(prealloc_page);
1504                 page_cache_release(prealloc_page);
1505         }
1506         return error;
1507 }
1508
1509 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1510 {
1511         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1512         int error;
1513         int ret;
1514
1515         if (((loff_t)vmf->pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
1516                 return VM_FAULT_SIGBUS;
1517
1518         error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
1519         if (error)
1520                 return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1521
1522         return ret | VM_FAULT_LOCKED;
1523 }
1524
1525 #ifdef CONFIG_NUMA
1526 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *new)
1527 {
1528         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1529         return mpol_set_shared_policy(&SHMEM_I(i)->policy, vma, new);
1530 }
1531
1532 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
1533                                           unsigned long addr)
1534 {
1535         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1536         unsigned long idx;
1537
1538         idx = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1539         return mpol_shared_policy_lookup(&SHMEM_I(i)->policy, idx);
1540 }
1541 #endif
1542
1543 int shmem_lock(struct file *file, int lock, struct user_struct *user)
1544 {
1545         struct inode *inode = file->f_path.dentry->d_inode;
1546         struct shmem_inode_info *info = SHMEM_I(inode);
1547         int retval = -ENOMEM;
1548
1549         spin_lock(&info->lock);
1550         if (lock && !(info->flags & VM_LOCKED)) {
1551                 if (!user_shm_lock(inode->i_size, user))
1552                         goto out_nomem;
1553                 info->flags |= VM_LOCKED;
1554                 mapping_set_unevictable(file->f_mapping);
1555         }
1556         if (!lock && (info->flags & VM_LOCKED) && user) {
1557                 user_shm_unlock(inode->i_size, user);
1558                 info->flags &= ~VM_LOCKED;
1559                 mapping_clear_unevictable(file->f_mapping);
1560                 scan_mapping_unevictable_pages(file->f_mapping);
1561         }
1562         retval = 0;
1563
1564 out_nomem:
1565         spin_unlock(&info->lock);
1566         return retval;
1567 }
1568
1569 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1570 {
1571         file_accessed(file);
1572         vma->vm_ops = &shmem_vm_ops;
1573         vma->vm_flags |= VM_CAN_NONLINEAR;
1574         return 0;
1575 }
1576
1577 static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
1578                                      int mode, dev_t dev, unsigned long flags)
1579 {
1580         struct inode *inode;
1581         struct shmem_inode_info *info;
1582         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1583
1584         if (shmem_reserve_inode(sb))
1585                 return NULL;
1586
1587         inode = new_inode(sb);
1588         if (inode) {
1589                 inode_init_owner(inode, dir, mode);
1590                 inode->i_blocks = 0;
1591                 inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1592                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1593                 inode->i_generation = get_seconds();
1594                 info = SHMEM_I(inode);
1595                 memset(info, 0, (char *)inode - (char *)info);
1596                 spin_lock_init(&info->lock);
1597                 info->flags = flags & VM_NORESERVE;
1598                 INIT_LIST_HEAD(&info->swaplist);
1599                 cache_no_acl(inode);
1600
1601                 switch (mode & S_IFMT) {
1602                 default:
1603                         inode->i_op = &shmem_special_inode_operations;
1604                         init_special_inode(inode, mode, dev);
1605                         break;
1606                 case S_IFREG:
1607                         inode->i_mapping->a_ops = &shmem_aops;
1608                         inode->i_op = &shmem_inode_operations;
1609                         inode->i_fop = &shmem_file_operations;
1610                         mpol_shared_policy_init(&info->policy,
1611                                                  shmem_get_sbmpol(sbinfo));
1612                         break;
1613                 case S_IFDIR:
1614                         inc_nlink(inode);
1615                         /* Some things misbehave if size == 0 on a directory */
1616                         inode->i_size = 2 * BOGO_DIRENT_SIZE;
1617                         inode->i_op = &shmem_dir_inode_operations;
1618                         inode->i_fop = &simple_dir_operations;
1619                         break;
1620                 case S_IFLNK:
1621                         /*
1622                          * Must not load anything in the rbtree,
1623                          * mpol_free_shared_policy will not be called.
1624                          */
1625                         mpol_shared_policy_init(&info->policy, NULL);
1626                         break;
1627                 }
1628         } else
1629                 shmem_free_inode(sb);
1630         return inode;
1631 }
1632
1633 #ifdef CONFIG_TMPFS
1634 static const struct inode_operations shmem_symlink_inode_operations;
1635 static const struct inode_operations shmem_symlink_inline_operations;
1636
1637 /*
1638  * Normally tmpfs avoids the use of shmem_readpage and shmem_write_begin;
1639  * but providing them allows a tmpfs file to be used for splice, sendfile, and
1640  * below the loop driver, in the generic fashion that many filesystems support.
1641  */
1642 static int shmem_readpage(struct file *file, struct page *page)
1643 {
1644         struct inode *inode = page->mapping->host;
1645         int error = shmem_getpage(inode, page->index, &page, SGP_CACHE, NULL);
1646         unlock_page(page);
1647         return error;
1648 }
1649
1650 static int
1651 shmem_write_begin(struct file *file, struct address_space *mapping,
1652                         loff_t pos, unsigned len, unsigned flags,
1653                         struct page **pagep, void **fsdata)
1654 {
1655         struct inode *inode = mapping->host;
1656         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1657         *pagep = NULL;
1658         return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
1659 }
1660
1661 static int
1662 shmem_write_end(struct file *file, struct address_space *mapping,
1663                         loff_t pos, unsigned len, unsigned copied,
1664                         struct page *page, void *fsdata)
1665 {
1666         struct inode *inode = mapping->host;
1667
1668         if (pos + copied > inode->i_size)
1669                 i_size_write(inode, pos + copied);
1670
1671         set_page_dirty(page);
1672         unlock_page(page);
1673         page_cache_release(page);
1674
1675         return copied;
1676 }
1677
1678 static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1679 {
1680         struct inode *inode = filp->f_path.dentry->d_inode;
1681         struct address_space *mapping = inode->i_mapping;
1682         unsigned long index, offset;
1683         enum sgp_type sgp = SGP_READ;
1684
1685         /*
1686          * Might this read be for a stacking filesystem?  Then when reading
1687          * holes of a sparse file, we actually need to allocate those pages,
1688          * and even mark them dirty, so it cannot exceed the max_blocks limit.
1689          */
1690         if (segment_eq(get_fs(), KERNEL_DS))
1691                 sgp = SGP_DIRTY;
1692
1693         index = *ppos >> PAGE_CACHE_SHIFT;
1694         offset = *ppos & ~PAGE_CACHE_MASK;
1695
1696         for (;;) {
1697                 struct page *page = NULL;
1698                 unsigned long end_index, nr, ret;
1699                 loff_t i_size = i_size_read(inode);
1700
1701                 end_index = i_size >> PAGE_CACHE_SHIFT;
1702                 if (index > end_index)
1703                         break;
1704                 if (index == end_index) {
1705                         nr = i_size & ~PAGE_CACHE_MASK;
1706                         if (nr <= offset)
1707                                 break;
1708                 }
1709
1710                 desc->error = shmem_getpage(inode, index, &page, sgp, NULL);
1711                 if (desc->error) {
1712                         if (desc->error == -EINVAL)
1713                                 desc->error = 0;
1714                         break;
1715                 }
1716                 if (page)
1717                         unlock_page(page);
1718
1719                 /*
1720                  * We must evaluate after, since reads (unlike writes)
1721                  * are called without i_mutex protection against truncate
1722                  */
1723                 nr = PAGE_CACHE_SIZE;
1724                 i_size = i_size_read(inode);
1725                 end_index = i_size >> PAGE_CACHE_SHIFT;
1726                 if (index == end_index) {
1727                         nr = i_size & ~PAGE_CACHE_MASK;
1728                         if (nr <= offset) {
1729                                 if (page)
1730                                         page_cache_release(page);
1731                                 break;
1732                         }
1733                 }
1734                 nr -= offset;
1735
1736                 if (page) {
1737                         /*
1738                          * If users can be writing to this page using arbitrary
1739                          * virtual addresses, take care about potential aliasing
1740                          * before reading the page on the kernel side.
1741                          */
1742                         if (mapping_writably_mapped(mapping))
1743                                 flush_dcache_page(page);
1744                         /*
1745                          * Mark the page accessed if we read the beginning.
1746                          */
1747                         if (!offset)
1748                                 mark_page_accessed(page);
1749                 } else {
1750                         page = ZERO_PAGE(0);
1751                         page_cache_get(page);
1752                 }
1753
1754                 /*
1755                  * Ok, we have the page, and it's up-to-date, so
1756                  * now we can copy it to user space...
1757                  *
1758                  * The actor routine returns how many bytes were actually used..
1759                  * NOTE! This may not be the same as how much of a user buffer
1760                  * we filled up (we may be padding etc), so we can only update
1761                  * "pos" here (the actor routine has to update the user buffer
1762                  * pointers and the remaining count).
1763                  */
1764                 ret = actor(desc, page, offset, nr);
1765                 offset += ret;
1766                 index += offset >> PAGE_CACHE_SHIFT;
1767                 offset &= ~PAGE_CACHE_MASK;
1768
1769                 page_cache_release(page);
1770                 if (ret != nr || !desc->count)
1771                         break;
1772
1773                 cond_resched();
1774         }
1775
1776         *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1777         file_accessed(filp);
1778 }
1779
1780 static ssize_t shmem_file_aio_read(struct kiocb *iocb,
1781                 const struct iovec *iov, unsigned long nr_segs, loff_t pos)
1782 {
1783         struct file *filp = iocb->ki_filp;
1784         ssize_t retval;
1785         unsigned long seg;
1786         size_t count;
1787         loff_t *ppos = &iocb->ki_pos;
1788
1789         retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1790         if (retval)
1791                 return retval;
1792
1793         for (seg = 0; seg < nr_segs; seg++) {
1794                 read_descriptor_t desc;
1795
1796                 desc.written = 0;
1797                 desc.arg.buf = iov[seg].iov_base;
1798                 desc.count = iov[seg].iov_len;
1799                 if (desc.count == 0)
1800                         continue;
1801                 desc.error = 0;
1802                 do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1803                 retval += desc.written;
1804                 if (desc.error) {
1805                         retval = retval ?: desc.error;
1806                         break;
1807                 }
1808                 if (desc.count > 0)
1809                         break;
1810         }
1811         return retval;
1812 }
1813
1814 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1815 {
1816         struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1817
1818         buf->f_type = TMPFS_MAGIC;
1819         buf->f_bsize = PAGE_CACHE_SIZE;
1820         buf->f_namelen = NAME_MAX;
1821         if (sbinfo->max_blocks) {
1822                 buf->f_blocks = sbinfo->max_blocks;
1823                 buf->f_bavail = buf->f_bfree =
1824                                 sbinfo->max_blocks - percpu_counter_sum(&sbinfo->used_blocks);
1825         }
1826         if (sbinfo->max_inodes) {
1827                 buf->f_files = sbinfo->max_inodes;
1828                 buf->f_ffree = sbinfo->free_inodes;
1829         }
1830         /* else leave those fields 0 like simple_statfs */
1831         return 0;
1832 }
1833
1834 /*
1835  * File creation. Allocate an inode, and we're done..
1836  */
1837 static int
1838 shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
1839 {
1840         struct inode *inode;
1841         int error = -ENOSPC;
1842
1843         inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
1844         if (inode) {
1845                 error = security_inode_init_security(inode, dir, NULL, NULL,
1846                                                      NULL);
1847                 if (error) {
1848                         if (error != -EOPNOTSUPP) {
1849                                 iput(inode);
1850                                 return error;
1851                         }
1852                 }
1853 #ifdef CONFIG_TMPFS_POSIX_ACL
1854                 error = generic_acl_init(inode, dir);
1855                 if (error) {
1856                         iput(inode);
1857                         return error;
1858                 }
1859 #else
1860                 error = 0;
1861 #endif
1862                 dir->i_size += BOGO_DIRENT_SIZE;
1863                 dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1864                 d_instantiate(dentry, inode);
1865                 dget(dentry); /* Extra count - pin the dentry in core */
1866         }
1867         return error;
1868 }
1869
1870 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, int mode)
1871 {
1872         int error;
1873
1874         if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1875                 return error;
1876         inc_nlink(dir);
1877         return 0;
1878 }
1879
1880 static int shmem_create(struct inode *dir, struct dentry *dentry, int mode,
1881                 struct nameidata *nd)
1882 {
1883         return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1884 }
1885
1886 /*
1887  * Link a file..
1888  */
1889 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1890 {
1891         struct inode *inode = old_dentry->d_inode;
1892         int ret;
1893
1894         /*
1895          * No ordinary (disk based) filesystem counts links as inodes;
1896          * but each new link needs a new dentry, pinning lowmem, and
1897          * tmpfs dentries cannot be pruned until they are unlinked.
1898          */
1899         ret = shmem_reserve_inode(inode->i_sb);
1900         if (ret)
1901                 goto out;
1902
1903         dir->i_size += BOGO_DIRENT_SIZE;
1904         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1905         inc_nlink(inode);
1906         atomic_inc(&inode->i_count);    /* New dentry reference */
1907         dget(dentry);           /* Extra pinning count for the created dentry */
1908         d_instantiate(dentry, inode);
1909 out:
1910         return ret;
1911 }
1912
1913 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
1914 {
1915         struct inode *inode = dentry->d_inode;
1916
1917         if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
1918                 shmem_free_inode(inode->i_sb);
1919
1920         dir->i_size -= BOGO_DIRENT_SIZE;
1921         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1922         drop_nlink(inode);
1923         dput(dentry);   /* Undo the count from "create" - this does all the work */
1924         return 0;
1925 }
1926
1927 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
1928 {
1929         if (!simple_empty(dentry))
1930                 return -ENOTEMPTY;
1931
1932         drop_nlink(dentry->d_inode);
1933         drop_nlink(dir);
1934         return shmem_unlink(dir, dentry);
1935 }
1936
1937 /*
1938  * The VFS layer already does all the dentry stuff for rename,
1939  * we just have to decrement the usage count for the target if
1940  * it exists so that the VFS layer correctly free's it when it
1941  * gets overwritten.
1942  */
1943 static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
1944 {
1945         struct inode *inode = old_dentry->d_inode;
1946         int they_are_dirs = S_ISDIR(inode->i_mode);
1947
1948         if (!simple_empty(new_dentry))
1949                 return -ENOTEMPTY;
1950
1951         if (new_dentry->d_inode) {
1952                 (void) shmem_unlink(new_dir, new_dentry);
1953                 if (they_are_dirs)
1954                         drop_nlink(old_dir);
1955         } else if (they_are_dirs) {
1956                 drop_nlink(old_dir);
1957                 inc_nlink(new_dir);
1958         }
1959
1960         old_dir->i_size -= BOGO_DIRENT_SIZE;
1961         new_dir->i_size += BOGO_DIRENT_SIZE;
1962         old_dir->i_ctime = old_dir->i_mtime =
1963         new_dir->i_ctime = new_dir->i_mtime =
1964         inode->i_ctime = CURRENT_TIME;
1965         return 0;
1966 }
1967
1968 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
1969 {
1970         int error;
1971         int len;
1972         struct inode *inode;
1973         struct page *page = NULL;
1974         char *kaddr;
1975         struct shmem_inode_info *info;
1976
1977         len = strlen(symname) + 1;
1978         if (len > PAGE_CACHE_SIZE)
1979                 return -ENAMETOOLONG;
1980
1981         inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE);
1982         if (!inode)
1983                 return -ENOSPC;
1984
1985         error = security_inode_init_security(inode, dir, NULL, NULL,
1986                                              NULL);
1987         if (error) {
1988                 if (error != -EOPNOTSUPP) {
1989                         iput(inode);
1990                         return error;
1991                 }
1992                 error = 0;
1993         }
1994
1995         info = SHMEM_I(inode);
1996         inode->i_size = len-1;
1997         if (len <= (char *)inode - (char *)info) {
1998                 /* do it inline */
1999                 memcpy(info, symname, len);
2000                 inode->i_op = &shmem_symlink_inline_operations;
2001         } else {
2002                 error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
2003                 if (error) {
2004                         iput(inode);
2005                         return error;
2006                 }
2007                 inode->i_mapping->a_ops = &shmem_aops;
2008                 inode->i_op = &shmem_symlink_inode_operations;
2009                 kaddr = kmap_atomic(page, KM_USER0);
2010                 memcpy(kaddr, symname, len);
2011                 kunmap_atomic(kaddr, KM_USER0);
2012                 set_page_dirty(page);
2013                 unlock_page(page);
2014                 page_cache_release(page);
2015         }
2016         dir->i_size += BOGO_DIRENT_SIZE;
2017         dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2018         d_instantiate(dentry, inode);
2019         dget(dentry);
2020         return 0;
2021 }
2022
2023 static void *shmem_follow_link_inline(struct dentry *dentry, struct nameidata *nd)
2024 {
2025         nd_set_link(nd, (char *)SHMEM_I(dentry->d_inode));
2026         return NULL;
2027 }
2028
2029 static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
2030 {
2031         struct page *page = NULL;
2032         int res = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
2033         nd_set_link(nd, res ? ERR_PTR(res) : kmap(page));
2034         if (page)
2035                 unlock_page(page);
2036         return page;
2037 }
2038
2039 static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
2040 {
2041         if (!IS_ERR(nd_get_link(nd))) {
2042                 struct page *page = cookie;
2043                 kunmap(page);
2044                 mark_page_accessed(page);
2045                 page_cache_release(page);
2046         }
2047 }
2048
2049 static const struct inode_operations shmem_symlink_inline_operations = {
2050         .readlink       = generic_readlink,
2051         .follow_link    = shmem_follow_link_inline,
2052 };
2053
2054 static const struct inode_operations shmem_symlink_inode_operations = {
2055         .readlink       = generic_readlink,
2056         .follow_link    = shmem_follow_link,
2057         .put_link       = shmem_put_link,
2058 };
2059
2060 #ifdef CONFIG_TMPFS_POSIX_ACL
2061 /*
2062  * Superblocks without xattr inode operations will get security.* xattr
2063  * support from the VFS "for free". As soon as we have any other xattrs
2064  * like ACLs, we also need to implement the security.* handlers at
2065  * filesystem level, though.
2066  */
2067
2068 static size_t shmem_xattr_security_list(struct dentry *dentry, char *list,
2069                                         size_t list_len, const char *name,
2070                                         size_t name_len, int handler_flags)
2071 {
2072         return security_inode_listsecurity(dentry->d_inode, list, list_len);
2073 }
2074
2075 static int shmem_xattr_security_get(struct dentry *dentry, const char *name,
2076                 void *buffer, size_t size, int handler_flags)
2077 {
2078         if (strcmp(name, "") == 0)
2079                 return -EINVAL;
2080         return xattr_getsecurity(dentry->d_inode, name, buffer, size);
2081 }
2082
2083 static int shmem_xattr_security_set(struct dentry *dentry, const char *name,
2084                 const void *value, size_t size, int flags, int handler_flags)
2085 {
2086         if (strcmp(name, "") == 0)
2087                 return -EINVAL;
2088         return security_inode_setsecurity(dentry->d_inode, name, value,
2089                                           size, flags);
2090 }
2091
2092 static const struct xattr_handler shmem_xattr_security_handler = {
2093         .prefix = XATTR_SECURITY_PREFIX,
2094         .list   = shmem_xattr_security_list,
2095         .get    = shmem_xattr_security_get,
2096         .set    = shmem_xattr_security_set,
2097 };
2098
2099 static const struct xattr_handler *shmem_xattr_handlers[] = {
2100         &generic_acl_access_handler,
2101         &generic_acl_default_handler,
2102         &shmem_xattr_security_handler,
2103         NULL
2104 };
2105 #endif
2106
2107 static struct dentry *shmem_get_parent(struct dentry *child)
2108 {
2109         return ERR_PTR(-ESTALE);
2110 }
2111
2112 static int shmem_match(struct inode *ino, void *vfh)
2113 {
2114         __u32 *fh = vfh;
2115         __u64 inum = fh[2];
2116         inum = (inum << 32) | fh[1];
2117         return ino->i_ino == inum && fh[0] == ino->i_generation;
2118 }
2119
2120 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
2121                 struct fid *fid, int fh_len, int fh_type)
2122 {
2123         struct inode *inode;
2124         struct dentry *dentry = NULL;
2125         u64 inum = fid->raw[2];
2126         inum = (inum << 32) | fid->raw[1];
2127
2128         if (fh_len < 3)
2129                 return NULL;
2130
2131         inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
2132                         shmem_match, fid->raw);
2133         if (inode) {
2134                 dentry = d_find_alias(inode);
2135                 iput(inode);
2136         }
2137
2138         return dentry;
2139 }
2140
2141 static int shmem_encode_fh(struct dentry *dentry, __u32 *fh, int *len,
2142                                 int connectable)
2143 {
2144         struct inode *inode = dentry->d_inode;
2145
2146         if (*len < 3)
2147                 return 255;
2148
2149         if (inode_unhashed(inode)) {
2150                 /* Unfortunately insert_inode_hash is not idempotent,
2151                  * so as we hash inodes here rather than at creation
2152                  * time, we need a lock to ensure we only try
2153                  * to do it once
2154                  */
2155                 static DEFINE_SPINLOCK(lock);
2156                 spin_lock(&lock);
2157                 if (inode_unhashed(inode))
2158                         __insert_inode_hash(inode,
2159                                             inode->i_ino + inode->i_generation);
2160                 spin_unlock(&lock);
2161         }
2162
2163         fh[0] = inode->i_generation;
2164         fh[1] = inode->i_ino;
2165         fh[2] = ((__u64)inode->i_ino) >> 32;
2166
2167         *len = 3;
2168         return 1;
2169 }
2170
2171 static const struct export_operations shmem_export_ops = {
2172         .get_parent     = shmem_get_parent,
2173         .encode_fh      = shmem_encode_fh,
2174         .fh_to_dentry   = shmem_fh_to_dentry,
2175 };
2176
2177 static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
2178                                bool remount)
2179 {
2180         char *this_char, *value, *rest;
2181
2182         while (options != NULL) {
2183                 this_char = options;
2184                 for (;;) {
2185                         /*
2186                          * NUL-terminate this option: unfortunately,
2187                          * mount options form a comma-separated list,
2188                          * but mpol's nodelist may also contain commas.
2189                          */
2190                         options = strchr(options, ',');
2191                         if (options == NULL)
2192                                 break;
2193                         options++;
2194                         if (!isdigit(*options)) {
2195                                 options[-1] = '\0';
2196                                 break;
2197                         }
2198                 }
2199                 if (!*this_char)
2200                         continue;
2201                 if ((value = strchr(this_char,'=')) != NULL) {
2202                         *value++ = 0;
2203                 } else {
2204                         printk(KERN_ERR
2205                             "tmpfs: No value for mount option '%s'\n",
2206                             this_char);
2207                         return 1;
2208                 }
2209
2210                 if (!strcmp(this_char,"size")) {
2211                         unsigned long long size;
2212                         size = memparse(value,&rest);
2213                         if (*rest == '%') {
2214                                 size <<= PAGE_SHIFT;
2215                                 size *= totalram_pages;
2216                                 do_div(size, 100);
2217                                 rest++;
2218                         }
2219                         if (*rest)
2220                                 goto bad_val;
2221                         sbinfo->max_blocks =
2222                                 DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
2223                 } else if (!strcmp(this_char,"nr_blocks")) {
2224                         sbinfo->max_blocks = memparse(value, &rest);
2225                         if (*rest)
2226                                 goto bad_val;
2227                 } else if (!strcmp(this_char,"nr_inodes")) {
2228                         sbinfo->max_inodes = memparse(value, &rest);
2229                         if (*rest)
2230                                 goto bad_val;
2231                 } else if (!strcmp(this_char,"mode")) {
2232                         if (remount)
2233                                 continue;
2234                         sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
2235                         if (*rest)
2236                                 goto bad_val;
2237                 } else if (!strcmp(this_char,"uid")) {
2238                         if (remount)
2239                                 continue;
2240                         sbinfo->uid = simple_strtoul(value, &rest, 0);
2241                         if (*rest)
2242                                 goto bad_val;
2243                 } else if (!strcmp(this_char,"gid")) {
2244                         if (remount)
2245                                 continue;
2246                         sbinfo->gid = simple_strtoul(value, &rest, 0);
2247                         if (*rest)
2248                                 goto bad_val;
2249                 } else if (!strcmp(this_char,"mpol")) {
2250                         if (mpol_parse_str(value, &sbinfo->mpol, 1))
2251                                 goto bad_val;
2252                 } else {
2253                         printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2254                                this_char);
2255                         return 1;
2256                 }
2257         }
2258         return 0;
2259
2260 bad_val:
2261         printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2262                value, this_char);
2263         return 1;
2264
2265 }
2266
2267 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2268 {
2269         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2270         struct shmem_sb_info config = *sbinfo;
2271         unsigned long inodes;
2272         int error = -EINVAL;
2273
2274         if (shmem_parse_options(data, &config, true))
2275                 return error;
2276
2277         spin_lock(&sbinfo->stat_lock);
2278         inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2279         if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0)
2280                 goto out;
2281         if (config.max_inodes < inodes)
2282                 goto out;
2283         /*
2284          * Those tests also disallow limited->unlimited while any are in
2285          * use, so i_blocks will always be zero when max_blocks is zero;
2286          * but we must separately disallow unlimited->limited, because
2287          * in that case we have no record of how much is already in use.
2288          */
2289         if (config.max_blocks && !sbinfo->max_blocks)
2290                 goto out;
2291         if (config.max_inodes && !sbinfo->max_inodes)
2292                 goto out;
2293
2294         error = 0;
2295         sbinfo->max_blocks  = config.max_blocks;
2296         sbinfo->max_inodes  = config.max_inodes;
2297         sbinfo->free_inodes = config.max_inodes - inodes;
2298
2299         mpol_put(sbinfo->mpol);
2300         sbinfo->mpol        = config.mpol;      /* transfers initial ref */
2301 out:
2302         spin_unlock(&sbinfo->stat_lock);
2303         return error;
2304 }
2305
2306 static int shmem_show_options(struct seq_file *seq, struct vfsmount *vfs)
2307 {
2308         struct shmem_sb_info *sbinfo = SHMEM_SB(vfs->mnt_sb);
2309
2310         if (sbinfo->max_blocks != shmem_default_max_blocks())
2311                 seq_printf(seq, ",size=%luk",
2312                         sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
2313         if (sbinfo->max_inodes != shmem_default_max_inodes())
2314                 seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
2315         if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
2316                 seq_printf(seq, ",mode=%03o", sbinfo->mode);
2317         if (sbinfo->uid != 0)
2318                 seq_printf(seq, ",uid=%u", sbinfo->uid);
2319         if (sbinfo->gid != 0)
2320                 seq_printf(seq, ",gid=%u", sbinfo->gid);
2321         shmem_show_mpol(seq, sbinfo->mpol);
2322         return 0;
2323 }
2324 #endif /* CONFIG_TMPFS */
2325
2326 static void shmem_put_super(struct super_block *sb)
2327 {
2328         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2329
2330         percpu_counter_destroy(&sbinfo->used_blocks);
2331         kfree(sbinfo);
2332         sb->s_fs_info = NULL;
2333 }
2334
2335 int shmem_fill_super(struct super_block *sb, void *data, int silent)
2336 {
2337         struct inode *inode;
2338         struct dentry *root;
2339         struct shmem_sb_info *sbinfo;
2340         int err = -ENOMEM;
2341
2342         /* Round up to L1_CACHE_BYTES to resist false sharing */
2343         sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
2344                                 L1_CACHE_BYTES), GFP_KERNEL);
2345         if (!sbinfo)
2346                 return -ENOMEM;
2347
2348         sbinfo->mode = S_IRWXUGO | S_ISVTX;
2349         sbinfo->uid = current_fsuid();
2350         sbinfo->gid = current_fsgid();
2351         sb->s_fs_info = sbinfo;
2352
2353 #ifdef CONFIG_TMPFS
2354         /*
2355          * Per default we only allow half of the physical ram per
2356          * tmpfs instance, limiting inodes to one per page of lowmem;
2357          * but the internal instance is left unlimited.
2358          */
2359         if (!(sb->s_flags & MS_NOUSER)) {
2360                 sbinfo->max_blocks = shmem_default_max_blocks();
2361                 sbinfo->max_inodes = shmem_default_max_inodes();
2362                 if (shmem_parse_options(data, sbinfo, false)) {
2363                         err = -EINVAL;
2364                         goto failed;
2365                 }
2366         }
2367         sb->s_export_op = &shmem_export_ops;
2368 #else
2369         sb->s_flags |= MS_NOUSER;
2370 #endif
2371
2372         spin_lock_init(&sbinfo->stat_lock);
2373         if (percpu_counter_init(&sbinfo->used_blocks, 0))
2374                 goto failed;
2375         sbinfo->free_inodes = sbinfo->max_inodes;
2376
2377         sb->s_maxbytes = SHMEM_MAX_BYTES;
2378         sb->s_blocksize = PAGE_CACHE_SIZE;
2379         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2380         sb->s_magic = TMPFS_MAGIC;
2381         sb->s_op = &shmem_ops;
2382         sb->s_time_gran = 1;
2383 #ifdef CONFIG_TMPFS_POSIX_ACL
2384         sb->s_xattr = shmem_xattr_handlers;
2385         sb->s_flags |= MS_POSIXACL;
2386 #endif
2387
2388         inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
2389         if (!inode)
2390                 goto failed;
2391         inode->i_uid = sbinfo->uid;
2392         inode->i_gid = sbinfo->gid;
2393         root = d_alloc_root(inode);
2394         if (!root)
2395                 goto failed_iput;
2396         sb->s_root = root;
2397         return 0;
2398
2399 failed_iput:
2400         iput(inode);
2401 failed:
2402         shmem_put_super(sb);
2403         return err;
2404 }
2405
2406 static struct kmem_cache *shmem_inode_cachep;
2407
2408 static struct inode *shmem_alloc_inode(struct super_block *sb)
2409 {
2410         struct shmem_inode_info *p;
2411         p = (struct shmem_inode_info *)kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2412         if (!p)
2413                 return NULL;
2414         return &p->vfs_inode;
2415 }
2416
2417 static void shmem_destroy_inode(struct inode *inode)
2418 {
2419         if ((inode->i_mode & S_IFMT) == S_IFREG) {
2420                 /* only struct inode is valid if it's an inline symlink */
2421                 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2422         }
2423         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2424 }
2425
2426 static void init_once(void *foo)
2427 {
2428         struct shmem_inode_info *p = (struct shmem_inode_info *) foo;
2429
2430         inode_init_once(&p->vfs_inode);
2431 }
2432
2433 static int init_inodecache(void)
2434 {
2435         shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2436                                 sizeof(struct shmem_inode_info),
2437                                 0, SLAB_PANIC, init_once);
2438         return 0;
2439 }
2440
2441 static void destroy_inodecache(void)
2442 {
2443         kmem_cache_destroy(shmem_inode_cachep);
2444 }
2445
2446 static const struct address_space_operations shmem_aops = {
2447         .writepage      = shmem_writepage,
2448         .set_page_dirty = __set_page_dirty_no_writeback,
2449 #ifdef CONFIG_TMPFS
2450         .readpage       = shmem_readpage,
2451         .write_begin    = shmem_write_begin,
2452         .write_end      = shmem_write_end,
2453 #endif
2454         .migratepage    = migrate_page,
2455         .error_remove_page = generic_error_remove_page,
2456 };
2457
2458 static const struct file_operations shmem_file_operations = {
2459         .mmap           = shmem_mmap,
2460 #ifdef CONFIG_TMPFS
2461         .llseek         = generic_file_llseek,
2462         .read           = do_sync_read,
2463         .write          = do_sync_write,
2464         .aio_read       = shmem_file_aio_read,
2465         .aio_write      = generic_file_aio_write,
2466         .fsync          = noop_fsync,
2467         .splice_read    = generic_file_splice_read,
2468         .splice_write   = generic_file_splice_write,
2469 #endif
2470 };
2471
2472 static const struct inode_operations shmem_inode_operations = {
2473         .setattr        = shmem_notify_change,
2474         .truncate_range = shmem_truncate_range,
2475 #ifdef CONFIG_TMPFS_POSIX_ACL
2476         .setxattr       = generic_setxattr,
2477         .getxattr       = generic_getxattr,
2478         .listxattr      = generic_listxattr,
2479         .removexattr    = generic_removexattr,
2480         .check_acl      = generic_check_acl,
2481 #endif
2482
2483 };
2484
2485 static const struct inode_operations shmem_dir_inode_operations = {
2486 #ifdef CONFIG_TMPFS
2487         .create         = shmem_create,
2488         .lookup         = simple_lookup,
2489         .link           = shmem_link,
2490         .unlink         = shmem_unlink,
2491         .symlink        = shmem_symlink,
2492         .mkdir          = shmem_mkdir,
2493         .rmdir          = shmem_rmdir,
2494         .mknod          = shmem_mknod,
2495         .rename         = shmem_rename,
2496 #endif
2497 #ifdef CONFIG_TMPFS_POSIX_ACL
2498         .setattr        = shmem_notify_change,
2499         .setxattr       = generic_setxattr,
2500         .getxattr       = generic_getxattr,
2501         .listxattr      = generic_listxattr,
2502         .removexattr    = generic_removexattr,
2503         .check_acl      = generic_check_acl,
2504 #endif
2505 };
2506
2507 static const struct inode_operations shmem_special_inode_operations = {
2508 #ifdef CONFIG_TMPFS_POSIX_ACL
2509         .setattr        = shmem_notify_change,
2510         .setxattr       = generic_setxattr,
2511         .getxattr       = generic_getxattr,
2512         .listxattr      = generic_listxattr,
2513         .removexattr    = generic_removexattr,
2514         .check_acl      = generic_check_acl,
2515 #endif
2516 };
2517
2518 static const struct super_operations shmem_ops = {
2519         .alloc_inode    = shmem_alloc_inode,
2520         .destroy_inode  = shmem_destroy_inode,
2521 #ifdef CONFIG_TMPFS
2522         .statfs         = shmem_statfs,
2523         .remount_fs     = shmem_remount_fs,
2524         .show_options   = shmem_show_options,
2525 #endif
2526         .evict_inode    = shmem_evict_inode,
2527         .drop_inode     = generic_delete_inode,
2528         .put_super      = shmem_put_super,
2529 };
2530
2531 static const struct vm_operations_struct shmem_vm_ops = {
2532         .fault          = shmem_fault,
2533 #ifdef CONFIG_NUMA
2534         .set_policy     = shmem_set_policy,
2535         .get_policy     = shmem_get_policy,
2536 #endif
2537 };
2538
2539
2540 static int shmem_get_sb(struct file_system_type *fs_type,
2541         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
2542 {
2543         return get_sb_nodev(fs_type, flags, data, shmem_fill_super, mnt);
2544 }
2545
2546 static struct file_system_type tmpfs_fs_type = {
2547         .owner          = THIS_MODULE,
2548         .name           = "tmpfs",
2549         .get_sb         = shmem_get_sb,
2550         .kill_sb        = kill_litter_super,
2551 };
2552
2553 int __init init_tmpfs(void)
2554 {
2555         int error;
2556
2557         error = bdi_init(&shmem_backing_dev_info);
2558         if (error)
2559                 goto out4;
2560
2561         error = init_inodecache();
2562         if (error)
2563                 goto out3;
2564
2565         error = register_filesystem(&tmpfs_fs_type);
2566         if (error) {
2567                 printk(KERN_ERR "Could not register tmpfs\n");
2568                 goto out2;
2569         }
2570
2571         shm_mnt = vfs_kern_mount(&tmpfs_fs_type, MS_NOUSER,
2572                                 tmpfs_fs_type.name, NULL);
2573         if (IS_ERR(shm_mnt)) {
2574                 error = PTR_ERR(shm_mnt);
2575                 printk(KERN_ERR "Could not kern_mount tmpfs\n");
2576                 goto out1;
2577         }
2578         return 0;
2579
2580 out1:
2581         unregister_filesystem(&tmpfs_fs_type);
2582 out2:
2583         destroy_inodecache();
2584 out3:
2585         bdi_destroy(&shmem_backing_dev_info);
2586 out4:
2587         shm_mnt = ERR_PTR(error);
2588         return error;
2589 }
2590
2591 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2592 /**
2593  * mem_cgroup_get_shmem_target - find a page or entry assigned to the shmem file
2594  * @inode: the inode to be searched
2595  * @pgoff: the offset to be searched
2596  * @pagep: the pointer for the found page to be stored
2597  * @ent: the pointer for the found swap entry to be stored
2598  *
2599  * If a page is found, refcount of it is incremented. Callers should handle
2600  * these refcount.
2601  */
2602 void mem_cgroup_get_shmem_target(struct inode *inode, pgoff_t pgoff,
2603                                         struct page **pagep, swp_entry_t *ent)
2604 {
2605         swp_entry_t entry = { .val = 0 }, *ptr;
2606         struct page *page = NULL;
2607         struct shmem_inode_info *info = SHMEM_I(inode);
2608
2609         if ((pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
2610                 goto out;
2611
2612         spin_lock(&info->lock);
2613         ptr = shmem_swp_entry(info, pgoff, NULL);
2614 #ifdef CONFIG_SWAP
2615         if (ptr && ptr->val) {
2616                 entry.val = ptr->val;
2617                 page = find_get_page(&swapper_space, entry.val);
2618         } else
2619 #endif
2620                 page = find_get_page(inode->i_mapping, pgoff);
2621         if (ptr)
2622                 shmem_swp_unmap(ptr);
2623         spin_unlock(&info->lock);
2624 out:
2625         *pagep = page;
2626         *ent = entry;
2627 }
2628 #endif
2629
2630 #else /* !CONFIG_SHMEM */
2631
2632 /*
2633  * tiny-shmem: simple shmemfs and tmpfs using ramfs code
2634  *
2635  * This is intended for small system where the benefits of the full
2636  * shmem code (swap-backed and resource-limited) are outweighed by
2637  * their complexity. On systems without swap this code should be
2638  * effectively equivalent, but much lighter weight.
2639  */
2640
2641 #include <linux/ramfs.h>
2642
2643 static struct file_system_type tmpfs_fs_type = {
2644         .name           = "tmpfs",
2645         .get_sb         = ramfs_get_sb,
2646         .kill_sb        = kill_litter_super,
2647 };
2648
2649 int __init init_tmpfs(void)
2650 {
2651         BUG_ON(register_filesystem(&tmpfs_fs_type) != 0);
2652
2653         shm_mnt = kern_mount(&tmpfs_fs_type);
2654         BUG_ON(IS_ERR(shm_mnt));
2655
2656         return 0;
2657 }
2658
2659 int shmem_unuse(swp_entry_t entry, struct page *page)
2660 {
2661         return 0;
2662 }
2663
2664 int shmem_lock(struct file *file, int lock, struct user_struct *user)
2665 {
2666         return 0;
2667 }
2668
2669 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2670 /**
2671  * mem_cgroup_get_shmem_target - find a page or entry assigned to the shmem file
2672  * @inode: the inode to be searched
2673  * @pgoff: the offset to be searched
2674  * @pagep: the pointer for the found page to be stored
2675  * @ent: the pointer for the found swap entry to be stored
2676  *
2677  * If a page is found, refcount of it is incremented. Callers should handle
2678  * these refcount.
2679  */
2680 void mem_cgroup_get_shmem_target(struct inode *inode, pgoff_t pgoff,
2681                                         struct page **pagep, swp_entry_t *ent)
2682 {
2683         struct page *page = NULL;
2684
2685         if ((pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
2686                 goto out;
2687         page = find_get_page(inode->i_mapping, pgoff);
2688 out:
2689         *pagep = page;
2690         *ent = (swp_entry_t){ .val = 0 };
2691 }
2692 #endif
2693
2694 #define shmem_vm_ops                            generic_file_vm_ops
2695 #define shmem_file_operations                   ramfs_file_operations
2696 #define shmem_get_inode(sb, dir, mode, dev, flags)      ramfs_get_inode(sb, dir, mode, dev)
2697 #define shmem_acct_size(flags, size)            0
2698 #define shmem_unacct_size(flags, size)          do {} while (0)
2699 #define SHMEM_MAX_BYTES                         MAX_LFS_FILESIZE
2700
2701 #endif /* CONFIG_SHMEM */
2702
2703 /* common code */
2704
2705 /**
2706  * shmem_file_setup - get an unlinked file living in tmpfs
2707  * @name: name for dentry (to be seen in /proc/<pid>/maps
2708  * @size: size to be set for the file
2709  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
2710  */
2711 struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
2712 {
2713         int error;
2714         struct file *file;
2715         struct inode *inode;
2716         struct path path;
2717         struct dentry *root;
2718         struct qstr this;
2719
2720         if (IS_ERR(shm_mnt))
2721                 return (void *)shm_mnt;
2722
2723         if (size < 0 || size > SHMEM_MAX_BYTES)
2724                 return ERR_PTR(-EINVAL);
2725
2726         if (shmem_acct_size(flags, size))
2727                 return ERR_PTR(-ENOMEM);
2728
2729         error = -ENOMEM;
2730         this.name = name;
2731         this.len = strlen(name);
2732         this.hash = 0; /* will go */
2733         root = shm_mnt->mnt_root;
2734         path.dentry = d_alloc(root, &this);
2735         if (!path.dentry)
2736                 goto put_memory;
2737         path.mnt = mntget(shm_mnt);
2738
2739         error = -ENOSPC;
2740         inode = shmem_get_inode(root->d_sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
2741         if (!inode)
2742                 goto put_dentry;
2743
2744         d_instantiate(path.dentry, inode);
2745         inode->i_size = size;
2746         inode->i_nlink = 0;     /* It is unlinked */
2747 #ifndef CONFIG_MMU
2748         error = ramfs_nommu_expand_for_mapping(inode, size);
2749         if (error)
2750                 goto put_dentry;
2751 #endif
2752
2753         error = -ENFILE;
2754         file = alloc_file(&path, FMODE_WRITE | FMODE_READ,
2755                   &shmem_file_operations);
2756         if (!file)
2757                 goto put_dentry;
2758
2759         return file;
2760
2761 put_dentry:
2762         path_put(&path);
2763 put_memory:
2764         shmem_unacct_size(flags, size);
2765         return ERR_PTR(error);
2766 }
2767 EXPORT_SYMBOL_GPL(shmem_file_setup);
2768
2769 /**
2770  * shmem_zero_setup - setup a shared anonymous mapping
2771  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2772  */
2773 int shmem_zero_setup(struct vm_area_struct *vma)
2774 {
2775         struct file *file;
2776         loff_t size = vma->vm_end - vma->vm_start;
2777
2778         file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2779         if (IS_ERR(file))
2780                 return PTR_ERR(file);
2781
2782         if (vma->vm_file)
2783                 fput(vma->vm_file);
2784         vma->vm_file = file;
2785         vma->vm_ops = &shmem_vm_ops;
2786         return 0;
2787 }