f65f84062db554ed2b3e9452cc787f8ab4f1b0d3
[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/swap.h>
32
33 static struct vfsmount *shm_mnt;
34
35 #ifdef CONFIG_SHMEM
36 /*
37  * This virtual memory filesystem is heavily based on the ramfs. It
38  * extends ramfs by the ability to use swap and honor resource limits
39  * which makes it a completely usable filesystem.
40  */
41
42 #include <linux/xattr.h>
43 #include <linux/exportfs.h>
44 #include <linux/posix_acl.h>
45 #include <linux/generic_acl.h>
46 #include <linux/mman.h>
47 #include <linux/string.h>
48 #include <linux/slab.h>
49 #include <linux/backing-dev.h>
50 #include <linux/shmem_fs.h>
51 #include <linux/writeback.h>
52 #include <linux/blkdev.h>
53 #include <linux/security.h>
54 #include <linux/swapops.h>
55 #include <linux/mempolicy.h>
56 #include <linux/namei.h>
57 #include <linux/ctype.h>
58 #include <linux/migrate.h>
59 #include <linux/highmem.h>
60 #include <linux/seq_file.h>
61 #include <linux/magic.h>
62
63 #include <asm/uaccess.h>
64 #include <asm/div64.h>
65 #include <asm/pgtable.h>
66
67 /*
68  * The maximum size of a shmem/tmpfs file is limited by the maximum size of
69  * its triple-indirect swap vector - see illustration at shmem_swp_entry().
70  *
71  * With 4kB page size, maximum file size is just over 2TB on a 32-bit kernel,
72  * but one eighth of that on a 64-bit kernel.  With 8kB page size, maximum
73  * file size is just over 4TB on a 64-bit kernel, but 16TB on a 32-bit kernel,
74  * MAX_LFS_FILESIZE being then more restrictive than swap vector layout.
75  *
76  * We use / and * instead of shifts in the definitions below, so that the swap
77  * vector can be tested with small even values (e.g. 20) for ENTRIES_PER_PAGE.
78  */
79 #define ENTRIES_PER_PAGE (PAGE_CACHE_SIZE/sizeof(unsigned long))
80 #define ENTRIES_PER_PAGEPAGE ((unsigned long long)ENTRIES_PER_PAGE*ENTRIES_PER_PAGE)
81
82 #define SHMSWP_MAX_INDEX (SHMEM_NR_DIRECT + (ENTRIES_PER_PAGEPAGE/2) * (ENTRIES_PER_PAGE+1))
83 #define SHMSWP_MAX_BYTES (SHMSWP_MAX_INDEX << PAGE_CACHE_SHIFT)
84
85 #define SHMEM_MAX_BYTES  min_t(unsigned long long, SHMSWP_MAX_BYTES, MAX_LFS_FILESIZE)
86 #define SHMEM_MAX_INDEX  ((unsigned long)((SHMEM_MAX_BYTES+1) >> PAGE_CACHE_SHIFT))
87
88 #define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
89 #define VM_ACCT(size)    (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
90
91 /* info->flags needs VM_flags to handle pagein/truncate races efficiently */
92 #define SHMEM_PAGEIN     VM_READ
93 #define SHMEM_TRUNCATE   VM_WRITE
94
95 /* Definition to limit shmem_truncate's steps between cond_rescheds */
96 #define LATENCY_LIMIT    64
97
98 /* Pretend that each entry is of this size in directory's i_size */
99 #define BOGO_DIRENT_SIZE 20
100
101 /* Flag allocation requirements to shmem_getpage and shmem_swp_alloc */
102 enum sgp_type {
103         SGP_READ,       /* don't exceed i_size, don't allocate page */
104         SGP_CACHE,      /* don't exceed i_size, may allocate page */
105         SGP_DIRTY,      /* like SGP_CACHE, but set new page dirty */
106         SGP_WRITE,      /* may exceed i_size, may allocate page */
107 };
108
109 #ifdef CONFIG_TMPFS
110 static unsigned long shmem_default_max_blocks(void)
111 {
112         return totalram_pages / 2;
113 }
114
115 static unsigned long shmem_default_max_inodes(void)
116 {
117         return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
118 }
119 #endif
120
121 static int shmem_getpage(struct inode *inode, unsigned long idx,
122                          struct page **pagep, enum sgp_type sgp, int *type);
123
124 static inline struct page *shmem_dir_alloc(gfp_t gfp_mask)
125 {
126         /*
127          * The above definition of ENTRIES_PER_PAGE, and the use of
128          * BLOCKS_PER_PAGE on indirect pages, assume PAGE_CACHE_SIZE:
129          * might be reconsidered if it ever diverges from PAGE_SIZE.
130          *
131          * Mobility flags are masked out as swap vectors cannot move
132          */
133         return alloc_pages((gfp_mask & ~GFP_MOVABLE_MASK) | __GFP_ZERO,
134                                 PAGE_CACHE_SHIFT-PAGE_SHIFT);
135 }
136
137 static inline void shmem_dir_free(struct page *page)
138 {
139         __free_pages(page, PAGE_CACHE_SHIFT-PAGE_SHIFT);
140 }
141
142 static struct page **shmem_dir_map(struct page *page)
143 {
144         return (struct page **)kmap_atomic(page, KM_USER0);
145 }
146
147 static inline void shmem_dir_unmap(struct page **dir)
148 {
149         kunmap_atomic(dir, KM_USER0);
150 }
151
152 static swp_entry_t *shmem_swp_map(struct page *page)
153 {
154         return (swp_entry_t *)kmap_atomic(page, KM_USER1);
155 }
156
157 static inline void shmem_swp_balance_unmap(void)
158 {
159         /*
160          * When passing a pointer to an i_direct entry, to code which
161          * also handles indirect entries and so will shmem_swp_unmap,
162          * we must arrange for the preempt count to remain in balance.
163          * What kmap_atomic of a lowmem page does depends on config
164          * and architecture, so pretend to kmap_atomic some lowmem page.
165          */
166         (void) kmap_atomic(ZERO_PAGE(0), KM_USER1);
167 }
168
169 static inline void shmem_swp_unmap(swp_entry_t *entry)
170 {
171         kunmap_atomic(entry, KM_USER1);
172 }
173
174 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
175 {
176         return sb->s_fs_info;
177 }
178
179 /*
180  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
181  * for shared memory and for shared anonymous (/dev/zero) mappings
182  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
183  * consistent with the pre-accounting of private mappings ...
184  */
185 static inline int shmem_acct_size(unsigned long flags, loff_t size)
186 {
187         return (flags & VM_NORESERVE) ?
188                 0 : security_vm_enough_memory_kern(VM_ACCT(size));
189 }
190
191 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
192 {
193         if (!(flags & VM_NORESERVE))
194                 vm_unacct_memory(VM_ACCT(size));
195 }
196
197 /*
198  * ... whereas tmpfs objects are accounted incrementally as
199  * pages are allocated, in order to allow huge sparse files.
200  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
201  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
202  */
203 static inline int shmem_acct_block(unsigned long flags)
204 {
205         return (flags & VM_NORESERVE) ?
206                 security_vm_enough_memory_kern(VM_ACCT(PAGE_CACHE_SIZE)) : 0;
207 }
208
209 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
210 {
211         if (flags & VM_NORESERVE)
212                 vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
213 }
214
215 static const struct super_operations shmem_ops;
216 static const struct address_space_operations shmem_aops;
217 static const struct file_operations shmem_file_operations;
218 static const struct inode_operations shmem_inode_operations;
219 static const struct inode_operations shmem_dir_inode_operations;
220 static const struct inode_operations shmem_special_inode_operations;
221 static const struct vm_operations_struct shmem_vm_ops;
222
223 static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
224         .ra_pages       = 0,    /* No readahead */
225         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
226         .unplug_io_fn   = default_unplug_io_fn,
227 };
228
229 static LIST_HEAD(shmem_swaplist);
230 static DEFINE_MUTEX(shmem_swaplist_mutex);
231
232 static void shmem_free_blocks(struct inode *inode, long pages)
233 {
234         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
235         if (sbinfo->max_blocks) {
236                 spin_lock(&sbinfo->stat_lock);
237                 sbinfo->free_blocks += pages;
238                 inode->i_blocks -= pages*BLOCKS_PER_PAGE;
239                 spin_unlock(&sbinfo->stat_lock);
240         }
241 }
242
243 static int shmem_reserve_inode(struct super_block *sb)
244 {
245         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
246         if (sbinfo->max_inodes) {
247                 spin_lock(&sbinfo->stat_lock);
248                 if (!sbinfo->free_inodes) {
249                         spin_unlock(&sbinfo->stat_lock);
250                         return -ENOSPC;
251                 }
252                 sbinfo->free_inodes--;
253                 spin_unlock(&sbinfo->stat_lock);
254         }
255         return 0;
256 }
257
258 static void shmem_free_inode(struct super_block *sb)
259 {
260         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
261         if (sbinfo->max_inodes) {
262                 spin_lock(&sbinfo->stat_lock);
263                 sbinfo->free_inodes++;
264                 spin_unlock(&sbinfo->stat_lock);
265         }
266 }
267
268 /**
269  * shmem_recalc_inode - recalculate the size of an inode
270  * @inode: inode to recalc
271  *
272  * We have to calculate the free blocks since the mm can drop
273  * undirtied hole pages behind our back.
274  *
275  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
276  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
277  *
278  * It has to be called with the spinlock held.
279  */
280 static void shmem_recalc_inode(struct inode *inode)
281 {
282         struct shmem_inode_info *info = SHMEM_I(inode);
283         long freed;
284
285         freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
286         if (freed > 0) {
287                 info->alloced -= freed;
288                 shmem_unacct_blocks(info->flags, freed);
289                 shmem_free_blocks(inode, freed);
290         }
291 }
292
293 /**
294  * shmem_swp_entry - find the swap vector position in the info structure
295  * @info:  info structure for the inode
296  * @index: index of the page to find
297  * @page:  optional page to add to the structure. Has to be preset to
298  *         all zeros
299  *
300  * If there is no space allocated yet it will return NULL when
301  * page is NULL, else it will use the page for the needed block,
302  * setting it to NULL on return to indicate that it has been used.
303  *
304  * The swap vector is organized the following way:
305  *
306  * There are SHMEM_NR_DIRECT entries directly stored in the
307  * shmem_inode_info structure. So small files do not need an addional
308  * allocation.
309  *
310  * For pages with index > SHMEM_NR_DIRECT there is the pointer
311  * i_indirect which points to a page which holds in the first half
312  * doubly indirect blocks, in the second half triple indirect blocks:
313  *
314  * For an artificial ENTRIES_PER_PAGE = 4 this would lead to the
315  * following layout (for SHMEM_NR_DIRECT == 16):
316  *
317  * i_indirect -> dir --> 16-19
318  *            |      +-> 20-23
319  *            |
320  *            +-->dir2 --> 24-27
321  *            |        +-> 28-31
322  *            |        +-> 32-35
323  *            |        +-> 36-39
324  *            |
325  *            +-->dir3 --> 40-43
326  *                     +-> 44-47
327  *                     +-> 48-51
328  *                     +-> 52-55
329  */
330 static swp_entry_t *shmem_swp_entry(struct shmem_inode_info *info, unsigned long index, struct page **page)
331 {
332         unsigned long offset;
333         struct page **dir;
334         struct page *subdir;
335
336         if (index < SHMEM_NR_DIRECT) {
337                 shmem_swp_balance_unmap();
338                 return info->i_direct+index;
339         }
340         if (!info->i_indirect) {
341                 if (page) {
342                         info->i_indirect = *page;
343                         *page = NULL;
344                 }
345                 return NULL;                    /* need another page */
346         }
347
348         index -= SHMEM_NR_DIRECT;
349         offset = index % ENTRIES_PER_PAGE;
350         index /= ENTRIES_PER_PAGE;
351         dir = shmem_dir_map(info->i_indirect);
352
353         if (index >= ENTRIES_PER_PAGE/2) {
354                 index -= ENTRIES_PER_PAGE/2;
355                 dir += ENTRIES_PER_PAGE/2 + index/ENTRIES_PER_PAGE;
356                 index %= ENTRIES_PER_PAGE;
357                 subdir = *dir;
358                 if (!subdir) {
359                         if (page) {
360                                 *dir = *page;
361                                 *page = NULL;
362                         }
363                         shmem_dir_unmap(dir);
364                         return NULL;            /* need another page */
365                 }
366                 shmem_dir_unmap(dir);
367                 dir = shmem_dir_map(subdir);
368         }
369
370         dir += index;
371         subdir = *dir;
372         if (!subdir) {
373                 if (!page || !(subdir = *page)) {
374                         shmem_dir_unmap(dir);
375                         return NULL;            /* need a page */
376                 }
377                 *dir = subdir;
378                 *page = NULL;
379         }
380         shmem_dir_unmap(dir);
381         return shmem_swp_map(subdir) + offset;
382 }
383
384 static void shmem_swp_set(struct shmem_inode_info *info, swp_entry_t *entry, unsigned long value)
385 {
386         long incdec = value? 1: -1;
387
388         entry->val = value;
389         info->swapped += incdec;
390         if ((unsigned long)(entry - info->i_direct) >= SHMEM_NR_DIRECT) {
391                 struct page *page = kmap_atomic_to_page(entry);
392                 set_page_private(page, page_private(page) + incdec);
393         }
394 }
395
396 /**
397  * shmem_swp_alloc - get the position of the swap entry for the page.
398  * @info:       info structure for the inode
399  * @index:      index of the page to find
400  * @sgp:        check and recheck i_size? skip allocation?
401  *
402  * If the entry does not exist, allocate it.
403  */
404 static swp_entry_t *shmem_swp_alloc(struct shmem_inode_info *info, unsigned long index, enum sgp_type sgp)
405 {
406         struct inode *inode = &info->vfs_inode;
407         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
408         struct page *page = NULL;
409         swp_entry_t *entry;
410
411         if (sgp != SGP_WRITE &&
412             ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode))
413                 return ERR_PTR(-EINVAL);
414
415         while (!(entry = shmem_swp_entry(info, index, &page))) {
416                 if (sgp == SGP_READ)
417                         return shmem_swp_map(ZERO_PAGE(0));
418                 /*
419                  * Test free_blocks against 1 not 0, since we have 1 data
420                  * page (and perhaps indirect index pages) yet to allocate:
421                  * a waste to allocate index if we cannot allocate data.
422                  */
423                 if (sbinfo->max_blocks) {
424                         spin_lock(&sbinfo->stat_lock);
425                         if (sbinfo->free_blocks <= 1) {
426                                 spin_unlock(&sbinfo->stat_lock);
427                                 return ERR_PTR(-ENOSPC);
428                         }
429                         sbinfo->free_blocks--;
430                         inode->i_blocks += BLOCKS_PER_PAGE;
431                         spin_unlock(&sbinfo->stat_lock);
432                 }
433
434                 spin_unlock(&info->lock);
435                 page = shmem_dir_alloc(mapping_gfp_mask(inode->i_mapping));
436                 spin_lock(&info->lock);
437
438                 if (!page) {
439                         shmem_free_blocks(inode, 1);
440                         return ERR_PTR(-ENOMEM);
441                 }
442                 if (sgp != SGP_WRITE &&
443                     ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
444                         entry = ERR_PTR(-EINVAL);
445                         break;
446                 }
447                 if (info->next_index <= index)
448                         info->next_index = index + 1;
449         }
450         if (page) {
451                 /* another task gave its page, or truncated the file */
452                 shmem_free_blocks(inode, 1);
453                 shmem_dir_free(page);
454         }
455         if (info->next_index <= index && !IS_ERR(entry))
456                 info->next_index = index + 1;
457         return entry;
458 }
459
460 /**
461  * shmem_free_swp - free some swap entries in a directory
462  * @dir:        pointer to the directory
463  * @edir:       pointer after last entry of the directory
464  * @punch_lock: pointer to spinlock when needed for the holepunch case
465  */
466 static int shmem_free_swp(swp_entry_t *dir, swp_entry_t *edir,
467                                                 spinlock_t *punch_lock)
468 {
469         spinlock_t *punch_unlock = NULL;
470         swp_entry_t *ptr;
471         int freed = 0;
472
473         for (ptr = dir; ptr < edir; ptr++) {
474                 if (ptr->val) {
475                         if (unlikely(punch_lock)) {
476                                 punch_unlock = punch_lock;
477                                 punch_lock = NULL;
478                                 spin_lock(punch_unlock);
479                                 if (!ptr->val)
480                                         continue;
481                         }
482                         free_swap_and_cache(*ptr);
483                         *ptr = (swp_entry_t){0};
484                         freed++;
485                 }
486         }
487         if (punch_unlock)
488                 spin_unlock(punch_unlock);
489         return freed;
490 }
491
492 static int shmem_map_and_free_swp(struct page *subdir, int offset,
493                 int limit, struct page ***dir, spinlock_t *punch_lock)
494 {
495         swp_entry_t *ptr;
496         int freed = 0;
497
498         ptr = shmem_swp_map(subdir);
499         for (; offset < limit; offset += LATENCY_LIMIT) {
500                 int size = limit - offset;
501                 if (size > LATENCY_LIMIT)
502                         size = LATENCY_LIMIT;
503                 freed += shmem_free_swp(ptr+offset, ptr+offset+size,
504                                                         punch_lock);
505                 if (need_resched()) {
506                         shmem_swp_unmap(ptr);
507                         if (*dir) {
508                                 shmem_dir_unmap(*dir);
509                                 *dir = NULL;
510                         }
511                         cond_resched();
512                         ptr = shmem_swp_map(subdir);
513                 }
514         }
515         shmem_swp_unmap(ptr);
516         return freed;
517 }
518
519 static void shmem_free_pages(struct list_head *next)
520 {
521         struct page *page;
522         int freed = 0;
523
524         do {
525                 page = container_of(next, struct page, lru);
526                 next = next->next;
527                 shmem_dir_free(page);
528                 freed++;
529                 if (freed >= LATENCY_LIMIT) {
530                         cond_resched();
531                         freed = 0;
532                 }
533         } while (next);
534 }
535
536 static void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end)
537 {
538         struct shmem_inode_info *info = SHMEM_I(inode);
539         unsigned long idx;
540         unsigned long size;
541         unsigned long limit;
542         unsigned long stage;
543         unsigned long diroff;
544         struct page **dir;
545         struct page *topdir;
546         struct page *middir;
547         struct page *subdir;
548         swp_entry_t *ptr;
549         LIST_HEAD(pages_to_free);
550         long nr_pages_to_free = 0;
551         long nr_swaps_freed = 0;
552         int offset;
553         int freed;
554         int punch_hole;
555         spinlock_t *needs_lock;
556         spinlock_t *punch_lock;
557         unsigned long upper_limit;
558
559         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
560         idx = (start + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
561         if (idx >= info->next_index)
562                 return;
563
564         spin_lock(&info->lock);
565         info->flags |= SHMEM_TRUNCATE;
566         if (likely(end == (loff_t) -1)) {
567                 limit = info->next_index;
568                 upper_limit = SHMEM_MAX_INDEX;
569                 info->next_index = idx;
570                 needs_lock = NULL;
571                 punch_hole = 0;
572         } else {
573                 if (end + 1 >= inode->i_size) { /* we may free a little more */
574                         limit = (inode->i_size + PAGE_CACHE_SIZE - 1) >>
575                                                         PAGE_CACHE_SHIFT;
576                         upper_limit = SHMEM_MAX_INDEX;
577                 } else {
578                         limit = (end + 1) >> PAGE_CACHE_SHIFT;
579                         upper_limit = limit;
580                 }
581                 needs_lock = &info->lock;
582                 punch_hole = 1;
583         }
584
585         topdir = info->i_indirect;
586         if (topdir && idx <= SHMEM_NR_DIRECT && !punch_hole) {
587                 info->i_indirect = NULL;
588                 nr_pages_to_free++;
589                 list_add(&topdir->lru, &pages_to_free);
590         }
591         spin_unlock(&info->lock);
592
593         if (info->swapped && idx < SHMEM_NR_DIRECT) {
594                 ptr = info->i_direct;
595                 size = limit;
596                 if (size > SHMEM_NR_DIRECT)
597                         size = SHMEM_NR_DIRECT;
598                 nr_swaps_freed = shmem_free_swp(ptr+idx, ptr+size, needs_lock);
599         }
600
601         /*
602          * If there are no indirect blocks or we are punching a hole
603          * below indirect blocks, nothing to be done.
604          */
605         if (!topdir || limit <= SHMEM_NR_DIRECT)
606                 goto done2;
607
608         /*
609          * The truncation case has already dropped info->lock, and we're safe
610          * because i_size and next_index have already been lowered, preventing
611          * access beyond.  But in the punch_hole case, we still need to take
612          * the lock when updating the swap directory, because there might be
613          * racing accesses by shmem_getpage(SGP_CACHE), shmem_unuse_inode or
614          * shmem_writepage.  However, whenever we find we can remove a whole
615          * directory page (not at the misaligned start or end of the range),
616          * we first NULLify its pointer in the level above, and then have no
617          * need to take the lock when updating its contents: needs_lock and
618          * punch_lock (either pointing to info->lock or NULL) manage this.
619          */
620
621         upper_limit -= SHMEM_NR_DIRECT;
622         limit -= SHMEM_NR_DIRECT;
623         idx = (idx > SHMEM_NR_DIRECT)? (idx - SHMEM_NR_DIRECT): 0;
624         offset = idx % ENTRIES_PER_PAGE;
625         idx -= offset;
626
627         dir = shmem_dir_map(topdir);
628         stage = ENTRIES_PER_PAGEPAGE/2;
629         if (idx < ENTRIES_PER_PAGEPAGE/2) {
630                 middir = topdir;
631                 diroff = idx/ENTRIES_PER_PAGE;
632         } else {
633                 dir += ENTRIES_PER_PAGE/2;
634                 dir += (idx - ENTRIES_PER_PAGEPAGE/2)/ENTRIES_PER_PAGEPAGE;
635                 while (stage <= idx)
636                         stage += ENTRIES_PER_PAGEPAGE;
637                 middir = *dir;
638                 if (*dir) {
639                         diroff = ((idx - ENTRIES_PER_PAGEPAGE/2) %
640                                 ENTRIES_PER_PAGEPAGE) / ENTRIES_PER_PAGE;
641                         if (!diroff && !offset && upper_limit >= stage) {
642                                 if (needs_lock) {
643                                         spin_lock(needs_lock);
644                                         *dir = NULL;
645                                         spin_unlock(needs_lock);
646                                         needs_lock = NULL;
647                                 } else
648                                         *dir = NULL;
649                                 nr_pages_to_free++;
650                                 list_add(&middir->lru, &pages_to_free);
651                         }
652                         shmem_dir_unmap(dir);
653                         dir = shmem_dir_map(middir);
654                 } else {
655                         diroff = 0;
656                         offset = 0;
657                         idx = stage;
658                 }
659         }
660
661         for (; idx < limit; idx += ENTRIES_PER_PAGE, diroff++) {
662                 if (unlikely(idx == stage)) {
663                         shmem_dir_unmap(dir);
664                         dir = shmem_dir_map(topdir) +
665                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
666                         while (!*dir) {
667                                 dir++;
668                                 idx += ENTRIES_PER_PAGEPAGE;
669                                 if (idx >= limit)
670                                         goto done1;
671                         }
672                         stage = idx + ENTRIES_PER_PAGEPAGE;
673                         middir = *dir;
674                         if (punch_hole)
675                                 needs_lock = &info->lock;
676                         if (upper_limit >= stage) {
677                                 if (needs_lock) {
678                                         spin_lock(needs_lock);
679                                         *dir = NULL;
680                                         spin_unlock(needs_lock);
681                                         needs_lock = NULL;
682                                 } else
683                                         *dir = NULL;
684                                 nr_pages_to_free++;
685                                 list_add(&middir->lru, &pages_to_free);
686                         }
687                         shmem_dir_unmap(dir);
688                         cond_resched();
689                         dir = shmem_dir_map(middir);
690                         diroff = 0;
691                 }
692                 punch_lock = needs_lock;
693                 subdir = dir[diroff];
694                 if (subdir && !offset && upper_limit-idx >= ENTRIES_PER_PAGE) {
695                         if (needs_lock) {
696                                 spin_lock(needs_lock);
697                                 dir[diroff] = NULL;
698                                 spin_unlock(needs_lock);
699                                 punch_lock = NULL;
700                         } else
701                                 dir[diroff] = NULL;
702                         nr_pages_to_free++;
703                         list_add(&subdir->lru, &pages_to_free);
704                 }
705                 if (subdir && page_private(subdir) /* has swap entries */) {
706                         size = limit - idx;
707                         if (size > ENTRIES_PER_PAGE)
708                                 size = ENTRIES_PER_PAGE;
709                         freed = shmem_map_and_free_swp(subdir,
710                                         offset, size, &dir, punch_lock);
711                         if (!dir)
712                                 dir = shmem_dir_map(middir);
713                         nr_swaps_freed += freed;
714                         if (offset || punch_lock) {
715                                 spin_lock(&info->lock);
716                                 set_page_private(subdir,
717                                         page_private(subdir) - freed);
718                                 spin_unlock(&info->lock);
719                         } else
720                                 BUG_ON(page_private(subdir) != freed);
721                 }
722                 offset = 0;
723         }
724 done1:
725         shmem_dir_unmap(dir);
726 done2:
727         if (inode->i_mapping->nrpages && (info->flags & SHMEM_PAGEIN)) {
728                 /*
729                  * Call truncate_inode_pages again: racing shmem_unuse_inode
730                  * may have swizzled a page in from swap since
731                  * truncate_pagecache or generic_delete_inode did it, before we
732                  * lowered next_index.  Also, though shmem_getpage checks
733                  * i_size before adding to cache, no recheck after: so fix the
734                  * narrow window there too.
735                  *
736                  * Recalling truncate_inode_pages_range and unmap_mapping_range
737                  * every time for punch_hole (which never got a chance to clear
738                  * SHMEM_PAGEIN at the start of vmtruncate_range) is expensive,
739                  * yet hardly ever necessary: try to optimize them out later.
740                  */
741                 truncate_inode_pages_range(inode->i_mapping, start, end);
742                 if (punch_hole)
743                         unmap_mapping_range(inode->i_mapping, start,
744                                                         end - start, 1);
745         }
746
747         spin_lock(&info->lock);
748         info->flags &= ~SHMEM_TRUNCATE;
749         info->swapped -= nr_swaps_freed;
750         if (nr_pages_to_free)
751                 shmem_free_blocks(inode, nr_pages_to_free);
752         shmem_recalc_inode(inode);
753         spin_unlock(&info->lock);
754
755         /*
756          * Empty swap vector directory pages to be freed?
757          */
758         if (!list_empty(&pages_to_free)) {
759                 pages_to_free.prev->next = NULL;
760                 shmem_free_pages(pages_to_free.next);
761         }
762 }
763
764 static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
765 {
766         struct inode *inode = dentry->d_inode;
767         loff_t newsize = attr->ia_size;
768         int error;
769
770         if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)
771                                         && newsize != inode->i_size) {
772                 struct page *page = NULL;
773
774                 if (newsize < inode->i_size) {
775                         /*
776                          * If truncating down to a partial page, then
777                          * if that page is already allocated, hold it
778                          * in memory until the truncation is over, so
779                          * truncate_partial_page cannnot miss it were
780                          * it assigned to swap.
781                          */
782                         if (newsize & (PAGE_CACHE_SIZE-1)) {
783                                 (void) shmem_getpage(inode,
784                                         newsize >> PAGE_CACHE_SHIFT,
785                                                 &page, SGP_READ, NULL);
786                                 if (page)
787                                         unlock_page(page);
788                         }
789                         /*
790                          * Reset SHMEM_PAGEIN flag so that shmem_truncate can
791                          * detect if any pages might have been added to cache
792                          * after truncate_inode_pages.  But we needn't bother
793                          * if it's being fully truncated to zero-length: the
794                          * nrpages check is efficient enough in that case.
795                          */
796                         if (newsize) {
797                                 struct shmem_inode_info *info = SHMEM_I(inode);
798                                 spin_lock(&info->lock);
799                                 info->flags &= ~SHMEM_PAGEIN;
800                                 spin_unlock(&info->lock);
801                         }
802                 }
803
804                 error = simple_setsize(inode, newsize);
805                 if (page)
806                         page_cache_release(page);
807                 if (error)
808                         return error;
809                 shmem_truncate_range(inode, newsize, (loff_t)-1);
810         }
811
812         error = inode_change_ok(inode, attr);
813         if (!error)
814                 generic_setattr(inode, attr);
815 #ifdef CONFIG_TMPFS_POSIX_ACL
816         if (!error && (attr->ia_valid & ATTR_MODE))
817                 error = generic_acl_chmod(inode);
818 #endif
819         return error;
820 }
821
822 static void shmem_delete_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         clear_inode(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_delete_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         swp_entry_t *entry;
1227         swp_entry_t swap;
1228         gfp_t gfp;
1229         int error;
1230
1231         if (idx >= SHMEM_MAX_INDEX)
1232                 return -EFBIG;
1233
1234         if (type)
1235                 *type = 0;
1236
1237         /*
1238          * Normally, filepage is NULL on entry, and either found
1239          * uptodate immediately, or allocated and zeroed, or read
1240          * in under swappage, which is then assigned to filepage.
1241          * But shmem_readpage (required for splice) passes in a locked
1242          * filepage, which may be found not uptodate by other callers
1243          * too, and may need to be copied from the swappage read in.
1244          */
1245 repeat:
1246         if (!filepage)
1247                 filepage = find_lock_page(mapping, idx);
1248         if (filepage && PageUptodate(filepage))
1249                 goto done;
1250         error = 0;
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         }
1262
1263         spin_lock(&info->lock);
1264         shmem_recalc_inode(inode);
1265         entry = shmem_swp_alloc(info, idx, sgp);
1266         if (IS_ERR(entry)) {
1267                 spin_unlock(&info->lock);
1268                 error = PTR_ERR(entry);
1269                 goto failed;
1270         }
1271         swap = *entry;
1272
1273         if (swap.val) {
1274                 /* Look it up and read it in.. */
1275                 swappage = lookup_swap_cache(swap);
1276                 if (!swappage) {
1277                         shmem_swp_unmap(entry);
1278                         /* here we actually do the io */
1279                         if (type && !(*type & VM_FAULT_MAJOR)) {
1280                                 __count_vm_event(PGMAJFAULT);
1281                                 *type |= VM_FAULT_MAJOR;
1282                         }
1283                         spin_unlock(&info->lock);
1284                         swappage = shmem_swapin(swap, gfp, info, idx);
1285                         if (!swappage) {
1286                                 spin_lock(&info->lock);
1287                                 entry = shmem_swp_alloc(info, idx, sgp);
1288                                 if (IS_ERR(entry))
1289                                         error = PTR_ERR(entry);
1290                                 else {
1291                                         if (entry->val == swap.val)
1292                                                 error = -ENOMEM;
1293                                         shmem_swp_unmap(entry);
1294                                 }
1295                                 spin_unlock(&info->lock);
1296                                 if (error)
1297                                         goto failed;
1298                                 goto repeat;
1299                         }
1300                         wait_on_page_locked(swappage);
1301                         page_cache_release(swappage);
1302                         goto repeat;
1303                 }
1304
1305                 /* We have to do this with page locked to prevent races */
1306                 if (!trylock_page(swappage)) {
1307                         shmem_swp_unmap(entry);
1308                         spin_unlock(&info->lock);
1309                         wait_on_page_locked(swappage);
1310                         page_cache_release(swappage);
1311                         goto repeat;
1312                 }
1313                 if (PageWriteback(swappage)) {
1314                         shmem_swp_unmap(entry);
1315                         spin_unlock(&info->lock);
1316                         wait_on_page_writeback(swappage);
1317                         unlock_page(swappage);
1318                         page_cache_release(swappage);
1319                         goto repeat;
1320                 }
1321                 if (!PageUptodate(swappage)) {
1322                         shmem_swp_unmap(entry);
1323                         spin_unlock(&info->lock);
1324                         unlock_page(swappage);
1325                         page_cache_release(swappage);
1326                         error = -EIO;
1327                         goto failed;
1328                 }
1329
1330                 if (filepage) {
1331                         shmem_swp_set(info, entry, 0);
1332                         shmem_swp_unmap(entry);
1333                         delete_from_swap_cache(swappage);
1334                         spin_unlock(&info->lock);
1335                         copy_highpage(filepage, swappage);
1336                         unlock_page(swappage);
1337                         page_cache_release(swappage);
1338                         flush_dcache_page(filepage);
1339                         SetPageUptodate(filepage);
1340                         set_page_dirty(filepage);
1341                         swap_free(swap);
1342                 } else if (!(error = add_to_page_cache_locked(swappage, mapping,
1343                                         idx, GFP_NOWAIT))) {
1344                         info->flags |= SHMEM_PAGEIN;
1345                         shmem_swp_set(info, entry, 0);
1346                         shmem_swp_unmap(entry);
1347                         delete_from_swap_cache(swappage);
1348                         spin_unlock(&info->lock);
1349                         filepage = swappage;
1350                         set_page_dirty(filepage);
1351                         swap_free(swap);
1352                 } else {
1353                         shmem_swp_unmap(entry);
1354                         spin_unlock(&info->lock);
1355                         if (error == -ENOMEM) {
1356                                 /*
1357                                  * reclaim from proper memory cgroup and
1358                                  * call memcg's OOM if needed.
1359                                  */
1360                                 error = mem_cgroup_shmem_charge_fallback(
1361                                                                 swappage,
1362                                                                 current->mm,
1363                                                                 gfp);
1364                                 if (error) {
1365                                         unlock_page(swappage);
1366                                         page_cache_release(swappage);
1367                                         goto failed;
1368                                 }
1369                         }
1370                         unlock_page(swappage);
1371                         page_cache_release(swappage);
1372                         goto repeat;
1373                 }
1374         } else if (sgp == SGP_READ && !filepage) {
1375                 shmem_swp_unmap(entry);
1376                 filepage = find_get_page(mapping, idx);
1377                 if (filepage &&
1378                     (!PageUptodate(filepage) || !trylock_page(filepage))) {
1379                         spin_unlock(&info->lock);
1380                         wait_on_page_locked(filepage);
1381                         page_cache_release(filepage);
1382                         filepage = NULL;
1383                         goto repeat;
1384                 }
1385                 spin_unlock(&info->lock);
1386         } else {
1387                 shmem_swp_unmap(entry);
1388                 sbinfo = SHMEM_SB(inode->i_sb);
1389                 if (sbinfo->max_blocks) {
1390                         spin_lock(&sbinfo->stat_lock);
1391                         if (sbinfo->free_blocks == 0 ||
1392                             shmem_acct_block(info->flags)) {
1393                                 spin_unlock(&sbinfo->stat_lock);
1394                                 spin_unlock(&info->lock);
1395                                 error = -ENOSPC;
1396                                 goto failed;
1397                         }
1398                         sbinfo->free_blocks--;
1399                         inode->i_blocks += BLOCKS_PER_PAGE;
1400                         spin_unlock(&sbinfo->stat_lock);
1401                 } else if (shmem_acct_block(info->flags)) {
1402                         spin_unlock(&info->lock);
1403                         error = -ENOSPC;
1404                         goto failed;
1405                 }
1406
1407                 if (!filepage) {
1408                         int ret;
1409
1410                         spin_unlock(&info->lock);
1411                         filepage = shmem_alloc_page(gfp, info, idx);
1412                         if (!filepage) {
1413                                 shmem_unacct_blocks(info->flags, 1);
1414                                 shmem_free_blocks(inode, 1);
1415                                 error = -ENOMEM;
1416                                 goto failed;
1417                         }
1418                         SetPageSwapBacked(filepage);
1419
1420                         /* Precharge page while we can wait, compensate after */
1421                         error = mem_cgroup_cache_charge(filepage, current->mm,
1422                                         GFP_KERNEL);
1423                         if (error) {
1424                                 page_cache_release(filepage);
1425                                 shmem_unacct_blocks(info->flags, 1);
1426                                 shmem_free_blocks(inode, 1);
1427                                 filepage = NULL;
1428                                 goto failed;
1429                         }
1430
1431                         spin_lock(&info->lock);
1432                         entry = shmem_swp_alloc(info, idx, sgp);
1433                         if (IS_ERR(entry))
1434                                 error = PTR_ERR(entry);
1435                         else {
1436                                 swap = *entry;
1437                                 shmem_swp_unmap(entry);
1438                         }
1439                         ret = error || swap.val;
1440                         if (ret)
1441                                 mem_cgroup_uncharge_cache_page(filepage);
1442                         else
1443                                 ret = add_to_page_cache_lru(filepage, mapping,
1444                                                 idx, GFP_NOWAIT);
1445                         /*
1446                          * At add_to_page_cache_lru() failure, uncharge will
1447                          * be done automatically.
1448                          */
1449                         if (ret) {
1450                                 spin_unlock(&info->lock);
1451                                 page_cache_release(filepage);
1452                                 shmem_unacct_blocks(info->flags, 1);
1453                                 shmem_free_blocks(inode, 1);
1454                                 filepage = NULL;
1455                                 if (error)
1456                                         goto failed;
1457                                 goto repeat;
1458                         }
1459                         info->flags |= SHMEM_PAGEIN;
1460                 }
1461
1462                 info->alloced++;
1463                 spin_unlock(&info->lock);
1464                 clear_highpage(filepage);
1465                 flush_dcache_page(filepage);
1466                 SetPageUptodate(filepage);
1467                 if (sgp == SGP_DIRTY)
1468                         set_page_dirty(filepage);
1469         }
1470 done:
1471         *pagep = filepage;
1472         return 0;
1473
1474 failed:
1475         if (*pagep != filepage) {
1476                 unlock_page(filepage);
1477                 page_cache_release(filepage);
1478         }
1479         return error;
1480 }
1481
1482 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1483 {
1484         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1485         int error;
1486         int ret;
1487
1488         if (((loff_t)vmf->pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
1489                 return VM_FAULT_SIGBUS;
1490
1491         error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
1492         if (error)
1493                 return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1494
1495         return ret | VM_FAULT_LOCKED;
1496 }
1497
1498 #ifdef CONFIG_NUMA
1499 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *new)
1500 {
1501         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1502         return mpol_set_shared_policy(&SHMEM_I(i)->policy, vma, new);
1503 }
1504
1505 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
1506                                           unsigned long addr)
1507 {
1508         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1509         unsigned long idx;
1510
1511         idx = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1512         return mpol_shared_policy_lookup(&SHMEM_I(i)->policy, idx);
1513 }
1514 #endif
1515
1516 int shmem_lock(struct file *file, int lock, struct user_struct *user)
1517 {
1518         struct inode *inode = file->f_path.dentry->d_inode;
1519         struct shmem_inode_info *info = SHMEM_I(inode);
1520         int retval = -ENOMEM;
1521
1522         spin_lock(&info->lock);
1523         if (lock && !(info->flags & VM_LOCKED)) {
1524                 if (!user_shm_lock(inode->i_size, user))
1525                         goto out_nomem;
1526                 info->flags |= VM_LOCKED;
1527                 mapping_set_unevictable(file->f_mapping);
1528         }
1529         if (!lock && (info->flags & VM_LOCKED) && user) {
1530                 user_shm_unlock(inode->i_size, user);
1531                 info->flags &= ~VM_LOCKED;
1532                 mapping_clear_unevictable(file->f_mapping);
1533                 scan_mapping_unevictable_pages(file->f_mapping);
1534         }
1535         retval = 0;
1536
1537 out_nomem:
1538         spin_unlock(&info->lock);
1539         return retval;
1540 }
1541
1542 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1543 {
1544         file_accessed(file);
1545         vma->vm_ops = &shmem_vm_ops;
1546         vma->vm_flags |= VM_CAN_NONLINEAR;
1547         return 0;
1548 }
1549
1550 static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
1551                                      int mode, dev_t dev, unsigned long flags)
1552 {
1553         struct inode *inode;
1554         struct shmem_inode_info *info;
1555         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1556
1557         if (shmem_reserve_inode(sb))
1558                 return NULL;
1559
1560         inode = new_inode(sb);
1561         if (inode) {
1562                 inode_init_owner(inode, dir, mode);
1563                 inode->i_blocks = 0;
1564                 inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1565                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1566                 inode->i_generation = get_seconds();
1567                 info = SHMEM_I(inode);
1568                 memset(info, 0, (char *)inode - (char *)info);
1569                 spin_lock_init(&info->lock);
1570                 info->flags = flags & VM_NORESERVE;
1571                 INIT_LIST_HEAD(&info->swaplist);
1572                 cache_no_acl(inode);
1573
1574                 switch (mode & S_IFMT) {
1575                 default:
1576                         inode->i_op = &shmem_special_inode_operations;
1577                         init_special_inode(inode, mode, dev);
1578                         break;
1579                 case S_IFREG:
1580                         inode->i_mapping->a_ops = &shmem_aops;
1581                         inode->i_op = &shmem_inode_operations;
1582                         inode->i_fop = &shmem_file_operations;
1583                         mpol_shared_policy_init(&info->policy,
1584                                                  shmem_get_sbmpol(sbinfo));
1585                         break;
1586                 case S_IFDIR:
1587                         inc_nlink(inode);
1588                         /* Some things misbehave if size == 0 on a directory */
1589                         inode->i_size = 2 * BOGO_DIRENT_SIZE;
1590                         inode->i_op = &shmem_dir_inode_operations;
1591                         inode->i_fop = &simple_dir_operations;
1592                         break;
1593                 case S_IFLNK:
1594                         /*
1595                          * Must not load anything in the rbtree,
1596                          * mpol_free_shared_policy will not be called.
1597                          */
1598                         mpol_shared_policy_init(&info->policy, NULL);
1599                         break;
1600                 }
1601         } else
1602                 shmem_free_inode(sb);
1603         return inode;
1604 }
1605
1606 #ifdef CONFIG_TMPFS
1607 static const struct inode_operations shmem_symlink_inode_operations;
1608 static const struct inode_operations shmem_symlink_inline_operations;
1609
1610 /*
1611  * Normally tmpfs avoids the use of shmem_readpage and shmem_write_begin;
1612  * but providing them allows a tmpfs file to be used for splice, sendfile, and
1613  * below the loop driver, in the generic fashion that many filesystems support.
1614  */
1615 static int shmem_readpage(struct file *file, struct page *page)
1616 {
1617         struct inode *inode = page->mapping->host;
1618         int error = shmem_getpage(inode, page->index, &page, SGP_CACHE, NULL);
1619         unlock_page(page);
1620         return error;
1621 }
1622
1623 static int
1624 shmem_write_begin(struct file *file, struct address_space *mapping,
1625                         loff_t pos, unsigned len, unsigned flags,
1626                         struct page **pagep, void **fsdata)
1627 {
1628         struct inode *inode = mapping->host;
1629         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1630         *pagep = NULL;
1631         return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
1632 }
1633
1634 static int
1635 shmem_write_end(struct file *file, struct address_space *mapping,
1636                         loff_t pos, unsigned len, unsigned copied,
1637                         struct page *page, void *fsdata)
1638 {
1639         struct inode *inode = mapping->host;
1640
1641         if (pos + copied > inode->i_size)
1642                 i_size_write(inode, pos + copied);
1643
1644         set_page_dirty(page);
1645         unlock_page(page);
1646         page_cache_release(page);
1647
1648         return copied;
1649 }
1650
1651 static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1652 {
1653         struct inode *inode = filp->f_path.dentry->d_inode;
1654         struct address_space *mapping = inode->i_mapping;
1655         unsigned long index, offset;
1656         enum sgp_type sgp = SGP_READ;
1657
1658         /*
1659          * Might this read be for a stacking filesystem?  Then when reading
1660          * holes of a sparse file, we actually need to allocate those pages,
1661          * and even mark them dirty, so it cannot exceed the max_blocks limit.
1662          */
1663         if (segment_eq(get_fs(), KERNEL_DS))
1664                 sgp = SGP_DIRTY;
1665
1666         index = *ppos >> PAGE_CACHE_SHIFT;
1667         offset = *ppos & ~PAGE_CACHE_MASK;
1668
1669         for (;;) {
1670                 struct page *page = NULL;
1671                 unsigned long end_index, nr, ret;
1672                 loff_t i_size = i_size_read(inode);
1673
1674                 end_index = i_size >> PAGE_CACHE_SHIFT;
1675                 if (index > end_index)
1676                         break;
1677                 if (index == end_index) {
1678                         nr = i_size & ~PAGE_CACHE_MASK;
1679                         if (nr <= offset)
1680                                 break;
1681                 }
1682
1683                 desc->error = shmem_getpage(inode, index, &page, sgp, NULL);
1684                 if (desc->error) {
1685                         if (desc->error == -EINVAL)
1686                                 desc->error = 0;
1687                         break;
1688                 }
1689                 if (page)
1690                         unlock_page(page);
1691
1692                 /*
1693                  * We must evaluate after, since reads (unlike writes)
1694                  * are called without i_mutex protection against truncate
1695                  */
1696                 nr = PAGE_CACHE_SIZE;
1697                 i_size = i_size_read(inode);
1698                 end_index = i_size >> PAGE_CACHE_SHIFT;
1699                 if (index == end_index) {
1700                         nr = i_size & ~PAGE_CACHE_MASK;
1701                         if (nr <= offset) {
1702                                 if (page)
1703                                         page_cache_release(page);
1704                                 break;
1705                         }
1706                 }
1707                 nr -= offset;
1708
1709                 if (page) {
1710                         /*
1711                          * If users can be writing to this page using arbitrary
1712                          * virtual addresses, take care about potential aliasing
1713                          * before reading the page on the kernel side.
1714                          */
1715                         if (mapping_writably_mapped(mapping))
1716                                 flush_dcache_page(page);
1717                         /*
1718                          * Mark the page accessed if we read the beginning.
1719                          */
1720                         if (!offset)
1721                                 mark_page_accessed(page);
1722                 } else {
1723                         page = ZERO_PAGE(0);
1724                         page_cache_get(page);
1725                 }
1726
1727                 /*
1728                  * Ok, we have the page, and it's up-to-date, so
1729                  * now we can copy it to user space...
1730                  *
1731                  * The actor routine returns how many bytes were actually used..
1732                  * NOTE! This may not be the same as how much of a user buffer
1733                  * we filled up (we may be padding etc), so we can only update
1734                  * "pos" here (the actor routine has to update the user buffer
1735                  * pointers and the remaining count).
1736                  */
1737                 ret = actor(desc, page, offset, nr);
1738                 offset += ret;
1739                 index += offset >> PAGE_CACHE_SHIFT;
1740                 offset &= ~PAGE_CACHE_MASK;
1741
1742                 page_cache_release(page);
1743                 if (ret != nr || !desc->count)
1744                         break;
1745
1746                 cond_resched();
1747         }
1748
1749         *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1750         file_accessed(filp);
1751 }
1752
1753 static ssize_t shmem_file_aio_read(struct kiocb *iocb,
1754                 const struct iovec *iov, unsigned long nr_segs, loff_t pos)
1755 {
1756         struct file *filp = iocb->ki_filp;
1757         ssize_t retval;
1758         unsigned long seg;
1759         size_t count;
1760         loff_t *ppos = &iocb->ki_pos;
1761
1762         retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1763         if (retval)
1764                 return retval;
1765
1766         for (seg = 0; seg < nr_segs; seg++) {
1767                 read_descriptor_t desc;
1768
1769                 desc.written = 0;
1770                 desc.arg.buf = iov[seg].iov_base;
1771                 desc.count = iov[seg].iov_len;
1772                 if (desc.count == 0)
1773                         continue;
1774                 desc.error = 0;
1775                 do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1776                 retval += desc.written;
1777                 if (desc.error) {
1778                         retval = retval ?: desc.error;
1779                         break;
1780                 }
1781                 if (desc.count > 0)
1782                         break;
1783         }
1784         return retval;
1785 }
1786
1787 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1788 {
1789         struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1790
1791         buf->f_type = TMPFS_MAGIC;
1792         buf->f_bsize = PAGE_CACHE_SIZE;
1793         buf->f_namelen = NAME_MAX;
1794         spin_lock(&sbinfo->stat_lock);
1795         if (sbinfo->max_blocks) {
1796                 buf->f_blocks = sbinfo->max_blocks;
1797                 buf->f_bavail = buf->f_bfree = sbinfo->free_blocks;
1798         }
1799         if (sbinfo->max_inodes) {
1800                 buf->f_files = sbinfo->max_inodes;
1801                 buf->f_ffree = sbinfo->free_inodes;
1802         }
1803         /* else leave those fields 0 like simple_statfs */
1804         spin_unlock(&sbinfo->stat_lock);
1805         return 0;
1806 }
1807
1808 /*
1809  * File creation. Allocate an inode, and we're done..
1810  */
1811 static int
1812 shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
1813 {
1814         struct inode *inode;
1815         int error = -ENOSPC;
1816
1817         inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
1818         if (inode) {
1819                 error = security_inode_init_security(inode, dir, NULL, NULL,
1820                                                      NULL);
1821                 if (error) {
1822                         if (error != -EOPNOTSUPP) {
1823                                 iput(inode);
1824                                 return error;
1825                         }
1826                 }
1827 #ifdef CONFIG_TMPFS_POSIX_ACL
1828                 error = generic_acl_init(inode, dir);
1829                 if (error) {
1830                         iput(inode);
1831                         return error;
1832                 }
1833 #else
1834                 error = 0;
1835 #endif
1836                 dir->i_size += BOGO_DIRENT_SIZE;
1837                 dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1838                 d_instantiate(dentry, inode);
1839                 dget(dentry); /* Extra count - pin the dentry in core */
1840         }
1841         return error;
1842 }
1843
1844 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, int mode)
1845 {
1846         int error;
1847
1848         if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1849                 return error;
1850         inc_nlink(dir);
1851         return 0;
1852 }
1853
1854 static int shmem_create(struct inode *dir, struct dentry *dentry, int mode,
1855                 struct nameidata *nd)
1856 {
1857         return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1858 }
1859
1860 /*
1861  * Link a file..
1862  */
1863 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1864 {
1865         struct inode *inode = old_dentry->d_inode;
1866         int ret;
1867
1868         /*
1869          * No ordinary (disk based) filesystem counts links as inodes;
1870          * but each new link needs a new dentry, pinning lowmem, and
1871          * tmpfs dentries cannot be pruned until they are unlinked.
1872          */
1873         ret = shmem_reserve_inode(inode->i_sb);
1874         if (ret)
1875                 goto out;
1876
1877         dir->i_size += BOGO_DIRENT_SIZE;
1878         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1879         inc_nlink(inode);
1880         atomic_inc(&inode->i_count);    /* New dentry reference */
1881         dget(dentry);           /* Extra pinning count for the created dentry */
1882         d_instantiate(dentry, inode);
1883 out:
1884         return ret;
1885 }
1886
1887 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
1888 {
1889         struct inode *inode = dentry->d_inode;
1890
1891         if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
1892                 shmem_free_inode(inode->i_sb);
1893
1894         dir->i_size -= BOGO_DIRENT_SIZE;
1895         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1896         drop_nlink(inode);
1897         dput(dentry);   /* Undo the count from "create" - this does all the work */
1898         return 0;
1899 }
1900
1901 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
1902 {
1903         if (!simple_empty(dentry))
1904                 return -ENOTEMPTY;
1905
1906         drop_nlink(dentry->d_inode);
1907         drop_nlink(dir);
1908         return shmem_unlink(dir, dentry);
1909 }
1910
1911 /*
1912  * The VFS layer already does all the dentry stuff for rename,
1913  * we just have to decrement the usage count for the target if
1914  * it exists so that the VFS layer correctly free's it when it
1915  * gets overwritten.
1916  */
1917 static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
1918 {
1919         struct inode *inode = old_dentry->d_inode;
1920         int they_are_dirs = S_ISDIR(inode->i_mode);
1921
1922         if (!simple_empty(new_dentry))
1923                 return -ENOTEMPTY;
1924
1925         if (new_dentry->d_inode) {
1926                 (void) shmem_unlink(new_dir, new_dentry);
1927                 if (they_are_dirs)
1928                         drop_nlink(old_dir);
1929         } else if (they_are_dirs) {
1930                 drop_nlink(old_dir);
1931                 inc_nlink(new_dir);
1932         }
1933
1934         old_dir->i_size -= BOGO_DIRENT_SIZE;
1935         new_dir->i_size += BOGO_DIRENT_SIZE;
1936         old_dir->i_ctime = old_dir->i_mtime =
1937         new_dir->i_ctime = new_dir->i_mtime =
1938         inode->i_ctime = CURRENT_TIME;
1939         return 0;
1940 }
1941
1942 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
1943 {
1944         int error;
1945         int len;
1946         struct inode *inode;
1947         struct page *page = NULL;
1948         char *kaddr;
1949         struct shmem_inode_info *info;
1950
1951         len = strlen(symname) + 1;
1952         if (len > PAGE_CACHE_SIZE)
1953                 return -ENAMETOOLONG;
1954
1955         inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE);
1956         if (!inode)
1957                 return -ENOSPC;
1958
1959         error = security_inode_init_security(inode, dir, NULL, NULL,
1960                                              NULL);
1961         if (error) {
1962                 if (error != -EOPNOTSUPP) {
1963                         iput(inode);
1964                         return error;
1965                 }
1966                 error = 0;
1967         }
1968
1969         info = SHMEM_I(inode);
1970         inode->i_size = len-1;
1971         if (len <= (char *)inode - (char *)info) {
1972                 /* do it inline */
1973                 memcpy(info, symname, len);
1974                 inode->i_op = &shmem_symlink_inline_operations;
1975         } else {
1976                 error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
1977                 if (error) {
1978                         iput(inode);
1979                         return error;
1980                 }
1981                 inode->i_mapping->a_ops = &shmem_aops;
1982                 inode->i_op = &shmem_symlink_inode_operations;
1983                 kaddr = kmap_atomic(page, KM_USER0);
1984                 memcpy(kaddr, symname, len);
1985                 kunmap_atomic(kaddr, KM_USER0);
1986                 set_page_dirty(page);
1987                 unlock_page(page);
1988                 page_cache_release(page);
1989         }
1990         dir->i_size += BOGO_DIRENT_SIZE;
1991         dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1992         d_instantiate(dentry, inode);
1993         dget(dentry);
1994         return 0;
1995 }
1996
1997 static void *shmem_follow_link_inline(struct dentry *dentry, struct nameidata *nd)
1998 {
1999         nd_set_link(nd, (char *)SHMEM_I(dentry->d_inode));
2000         return NULL;
2001 }
2002
2003 static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
2004 {
2005         struct page *page = NULL;
2006         int res = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
2007         nd_set_link(nd, res ? ERR_PTR(res) : kmap(page));
2008         if (page)
2009                 unlock_page(page);
2010         return page;
2011 }
2012
2013 static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
2014 {
2015         if (!IS_ERR(nd_get_link(nd))) {
2016                 struct page *page = cookie;
2017                 kunmap(page);
2018                 mark_page_accessed(page);
2019                 page_cache_release(page);
2020         }
2021 }
2022
2023 static const struct inode_operations shmem_symlink_inline_operations = {
2024         .readlink       = generic_readlink,
2025         .follow_link    = shmem_follow_link_inline,
2026 };
2027
2028 static const struct inode_operations shmem_symlink_inode_operations = {
2029         .readlink       = generic_readlink,
2030         .follow_link    = shmem_follow_link,
2031         .put_link       = shmem_put_link,
2032 };
2033
2034 #ifdef CONFIG_TMPFS_POSIX_ACL
2035 /*
2036  * Superblocks without xattr inode operations will get security.* xattr
2037  * support from the VFS "for free". As soon as we have any other xattrs
2038  * like ACLs, we also need to implement the security.* handlers at
2039  * filesystem level, though.
2040  */
2041
2042 static size_t shmem_xattr_security_list(struct dentry *dentry, char *list,
2043                                         size_t list_len, const char *name,
2044                                         size_t name_len, int handler_flags)
2045 {
2046         return security_inode_listsecurity(dentry->d_inode, list, list_len);
2047 }
2048
2049 static int shmem_xattr_security_get(struct dentry *dentry, const char *name,
2050                 void *buffer, size_t size, int handler_flags)
2051 {
2052         if (strcmp(name, "") == 0)
2053                 return -EINVAL;
2054         return xattr_getsecurity(dentry->d_inode, name, buffer, size);
2055 }
2056
2057 static int shmem_xattr_security_set(struct dentry *dentry, const char *name,
2058                 const void *value, size_t size, int flags, int handler_flags)
2059 {
2060         if (strcmp(name, "") == 0)
2061                 return -EINVAL;
2062         return security_inode_setsecurity(dentry->d_inode, name, value,
2063                                           size, flags);
2064 }
2065
2066 static const struct xattr_handler shmem_xattr_security_handler = {
2067         .prefix = XATTR_SECURITY_PREFIX,
2068         .list   = shmem_xattr_security_list,
2069         .get    = shmem_xattr_security_get,
2070         .set    = shmem_xattr_security_set,
2071 };
2072
2073 static const struct xattr_handler *shmem_xattr_handlers[] = {
2074         &generic_acl_access_handler,
2075         &generic_acl_default_handler,
2076         &shmem_xattr_security_handler,
2077         NULL
2078 };
2079 #endif
2080
2081 static struct dentry *shmem_get_parent(struct dentry *child)
2082 {
2083         return ERR_PTR(-ESTALE);
2084 }
2085
2086 static int shmem_match(struct inode *ino, void *vfh)
2087 {
2088         __u32 *fh = vfh;
2089         __u64 inum = fh[2];
2090         inum = (inum << 32) | fh[1];
2091         return ino->i_ino == inum && fh[0] == ino->i_generation;
2092 }
2093
2094 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
2095                 struct fid *fid, int fh_len, int fh_type)
2096 {
2097         struct inode *inode;
2098         struct dentry *dentry = NULL;
2099         u64 inum = fid->raw[2];
2100         inum = (inum << 32) | fid->raw[1];
2101
2102         if (fh_len < 3)
2103                 return NULL;
2104
2105         inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
2106                         shmem_match, fid->raw);
2107         if (inode) {
2108                 dentry = d_find_alias(inode);
2109                 iput(inode);
2110         }
2111
2112         return dentry;
2113 }
2114
2115 static int shmem_encode_fh(struct dentry *dentry, __u32 *fh, int *len,
2116                                 int connectable)
2117 {
2118         struct inode *inode = dentry->d_inode;
2119
2120         if (*len < 3)
2121                 return 255;
2122
2123         if (hlist_unhashed(&inode->i_hash)) {
2124                 /* Unfortunately insert_inode_hash is not idempotent,
2125                  * so as we hash inodes here rather than at creation
2126                  * time, we need a lock to ensure we only try
2127                  * to do it once
2128                  */
2129                 static DEFINE_SPINLOCK(lock);
2130                 spin_lock(&lock);
2131                 if (hlist_unhashed(&inode->i_hash))
2132                         __insert_inode_hash(inode,
2133                                             inode->i_ino + inode->i_generation);
2134                 spin_unlock(&lock);
2135         }
2136
2137         fh[0] = inode->i_generation;
2138         fh[1] = inode->i_ino;
2139         fh[2] = ((__u64)inode->i_ino) >> 32;
2140
2141         *len = 3;
2142         return 1;
2143 }
2144
2145 static const struct export_operations shmem_export_ops = {
2146         .get_parent     = shmem_get_parent,
2147         .encode_fh      = shmem_encode_fh,
2148         .fh_to_dentry   = shmem_fh_to_dentry,
2149 };
2150
2151 static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
2152                                bool remount)
2153 {
2154         char *this_char, *value, *rest;
2155
2156         while (options != NULL) {
2157                 this_char = options;
2158                 for (;;) {
2159                         /*
2160                          * NUL-terminate this option: unfortunately,
2161                          * mount options form a comma-separated list,
2162                          * but mpol's nodelist may also contain commas.
2163                          */
2164                         options = strchr(options, ',');
2165                         if (options == NULL)
2166                                 break;
2167                         options++;
2168                         if (!isdigit(*options)) {
2169                                 options[-1] = '\0';
2170                                 break;
2171                         }
2172                 }
2173                 if (!*this_char)
2174                         continue;
2175                 if ((value = strchr(this_char,'=')) != NULL) {
2176                         *value++ = 0;
2177                 } else {
2178                         printk(KERN_ERR
2179                             "tmpfs: No value for mount option '%s'\n",
2180                             this_char);
2181                         return 1;
2182                 }
2183
2184                 if (!strcmp(this_char,"size")) {
2185                         unsigned long long size;
2186                         size = memparse(value,&rest);
2187                         if (*rest == '%') {
2188                                 size <<= PAGE_SHIFT;
2189                                 size *= totalram_pages;
2190                                 do_div(size, 100);
2191                                 rest++;
2192                         }
2193                         if (*rest)
2194                                 goto bad_val;
2195                         sbinfo->max_blocks =
2196                                 DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
2197                 } else if (!strcmp(this_char,"nr_blocks")) {
2198                         sbinfo->max_blocks = memparse(value, &rest);
2199                         if (*rest)
2200                                 goto bad_val;
2201                 } else if (!strcmp(this_char,"nr_inodes")) {
2202                         sbinfo->max_inodes = memparse(value, &rest);
2203                         if (*rest)
2204                                 goto bad_val;
2205                 } else if (!strcmp(this_char,"mode")) {
2206                         if (remount)
2207                                 continue;
2208                         sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
2209                         if (*rest)
2210                                 goto bad_val;
2211                 } else if (!strcmp(this_char,"uid")) {
2212                         if (remount)
2213                                 continue;
2214                         sbinfo->uid = simple_strtoul(value, &rest, 0);
2215                         if (*rest)
2216                                 goto bad_val;
2217                 } else if (!strcmp(this_char,"gid")) {
2218                         if (remount)
2219                                 continue;
2220                         sbinfo->gid = simple_strtoul(value, &rest, 0);
2221                         if (*rest)
2222                                 goto bad_val;
2223                 } else if (!strcmp(this_char,"mpol")) {
2224                         if (mpol_parse_str(value, &sbinfo->mpol, 1))
2225                                 goto bad_val;
2226                 } else {
2227                         printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2228                                this_char);
2229                         return 1;
2230                 }
2231         }
2232         return 0;
2233
2234 bad_val:
2235         printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2236                value, this_char);
2237         return 1;
2238
2239 }
2240
2241 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2242 {
2243         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2244         struct shmem_sb_info config = *sbinfo;
2245         unsigned long blocks;
2246         unsigned long inodes;
2247         int error = -EINVAL;
2248
2249         if (shmem_parse_options(data, &config, true))
2250                 return error;
2251
2252         spin_lock(&sbinfo->stat_lock);
2253         blocks = sbinfo->max_blocks - sbinfo->free_blocks;
2254         inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2255         if (config.max_blocks < blocks)
2256                 goto out;
2257         if (config.max_inodes < inodes)
2258                 goto out;
2259         /*
2260          * Those tests also disallow limited->unlimited while any are in
2261          * use, so i_blocks will always be zero when max_blocks is zero;
2262          * but we must separately disallow unlimited->limited, because
2263          * in that case we have no record of how much is already in use.
2264          */
2265         if (config.max_blocks && !sbinfo->max_blocks)
2266                 goto out;
2267         if (config.max_inodes && !sbinfo->max_inodes)
2268                 goto out;
2269
2270         error = 0;
2271         sbinfo->max_blocks  = config.max_blocks;
2272         sbinfo->free_blocks = config.max_blocks - blocks;
2273         sbinfo->max_inodes  = config.max_inodes;
2274         sbinfo->free_inodes = config.max_inodes - inodes;
2275
2276         mpol_put(sbinfo->mpol);
2277         sbinfo->mpol        = config.mpol;      /* transfers initial ref */
2278 out:
2279         spin_unlock(&sbinfo->stat_lock);
2280         return error;
2281 }
2282
2283 static int shmem_show_options(struct seq_file *seq, struct vfsmount *vfs)
2284 {
2285         struct shmem_sb_info *sbinfo = SHMEM_SB(vfs->mnt_sb);
2286
2287         if (sbinfo->max_blocks != shmem_default_max_blocks())
2288                 seq_printf(seq, ",size=%luk",
2289                         sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
2290         if (sbinfo->max_inodes != shmem_default_max_inodes())
2291                 seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
2292         if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
2293                 seq_printf(seq, ",mode=%03o", sbinfo->mode);
2294         if (sbinfo->uid != 0)
2295                 seq_printf(seq, ",uid=%u", sbinfo->uid);
2296         if (sbinfo->gid != 0)
2297                 seq_printf(seq, ",gid=%u", sbinfo->gid);
2298         shmem_show_mpol(seq, sbinfo->mpol);
2299         return 0;
2300 }
2301 #endif /* CONFIG_TMPFS */
2302
2303 static void shmem_put_super(struct super_block *sb)
2304 {
2305         kfree(sb->s_fs_info);
2306         sb->s_fs_info = NULL;
2307 }
2308
2309 int shmem_fill_super(struct super_block *sb, void *data, int silent)
2310 {
2311         struct inode *inode;
2312         struct dentry *root;
2313         struct shmem_sb_info *sbinfo;
2314         int err = -ENOMEM;
2315
2316         /* Round up to L1_CACHE_BYTES to resist false sharing */
2317         sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
2318                                 L1_CACHE_BYTES), GFP_KERNEL);
2319         if (!sbinfo)
2320                 return -ENOMEM;
2321
2322         sbinfo->mode = S_IRWXUGO | S_ISVTX;
2323         sbinfo->uid = current_fsuid();
2324         sbinfo->gid = current_fsgid();
2325         sb->s_fs_info = sbinfo;
2326
2327 #ifdef CONFIG_TMPFS
2328         /*
2329          * Per default we only allow half of the physical ram per
2330          * tmpfs instance, limiting inodes to one per page of lowmem;
2331          * but the internal instance is left unlimited.
2332          */
2333         if (!(sb->s_flags & MS_NOUSER)) {
2334                 sbinfo->max_blocks = shmem_default_max_blocks();
2335                 sbinfo->max_inodes = shmem_default_max_inodes();
2336                 if (shmem_parse_options(data, sbinfo, false)) {
2337                         err = -EINVAL;
2338                         goto failed;
2339                 }
2340         }
2341         sb->s_export_op = &shmem_export_ops;
2342 #else
2343         sb->s_flags |= MS_NOUSER;
2344 #endif
2345
2346         spin_lock_init(&sbinfo->stat_lock);
2347         sbinfo->free_blocks = sbinfo->max_blocks;
2348         sbinfo->free_inodes = sbinfo->max_inodes;
2349
2350         sb->s_maxbytes = SHMEM_MAX_BYTES;
2351         sb->s_blocksize = PAGE_CACHE_SIZE;
2352         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2353         sb->s_magic = TMPFS_MAGIC;
2354         sb->s_op = &shmem_ops;
2355         sb->s_time_gran = 1;
2356 #ifdef CONFIG_TMPFS_POSIX_ACL
2357         sb->s_xattr = shmem_xattr_handlers;
2358         sb->s_flags |= MS_POSIXACL;
2359 #endif
2360
2361         inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
2362         if (!inode)
2363                 goto failed;
2364         inode->i_uid = sbinfo->uid;
2365         inode->i_gid = sbinfo->gid;
2366         root = d_alloc_root(inode);
2367         if (!root)
2368                 goto failed_iput;
2369         sb->s_root = root;
2370         return 0;
2371
2372 failed_iput:
2373         iput(inode);
2374 failed:
2375         shmem_put_super(sb);
2376         return err;
2377 }
2378
2379 static struct kmem_cache *shmem_inode_cachep;
2380
2381 static struct inode *shmem_alloc_inode(struct super_block *sb)
2382 {
2383         struct shmem_inode_info *p;
2384         p = (struct shmem_inode_info *)kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2385         if (!p)
2386                 return NULL;
2387         return &p->vfs_inode;
2388 }
2389
2390 static void shmem_destroy_inode(struct inode *inode)
2391 {
2392         if ((inode->i_mode & S_IFMT) == S_IFREG) {
2393                 /* only struct inode is valid if it's an inline symlink */
2394                 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2395         }
2396         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2397 }
2398
2399 static void init_once(void *foo)
2400 {
2401         struct shmem_inode_info *p = (struct shmem_inode_info *) foo;
2402
2403         inode_init_once(&p->vfs_inode);
2404 }
2405
2406 static int init_inodecache(void)
2407 {
2408         shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2409                                 sizeof(struct shmem_inode_info),
2410                                 0, SLAB_PANIC, init_once);
2411         return 0;
2412 }
2413
2414 static void destroy_inodecache(void)
2415 {
2416         kmem_cache_destroy(shmem_inode_cachep);
2417 }
2418
2419 static const struct address_space_operations shmem_aops = {
2420         .writepage      = shmem_writepage,
2421         .set_page_dirty = __set_page_dirty_no_writeback,
2422 #ifdef CONFIG_TMPFS
2423         .readpage       = shmem_readpage,
2424         .write_begin    = shmem_write_begin,
2425         .write_end      = shmem_write_end,
2426 #endif
2427         .migratepage    = migrate_page,
2428         .error_remove_page = generic_error_remove_page,
2429 };
2430
2431 static const struct file_operations shmem_file_operations = {
2432         .mmap           = shmem_mmap,
2433 #ifdef CONFIG_TMPFS
2434         .llseek         = generic_file_llseek,
2435         .read           = do_sync_read,
2436         .write          = do_sync_write,
2437         .aio_read       = shmem_file_aio_read,
2438         .aio_write      = generic_file_aio_write,
2439         .fsync          = noop_fsync,
2440         .splice_read    = generic_file_splice_read,
2441         .splice_write   = generic_file_splice_write,
2442 #endif
2443 };
2444
2445 static const struct inode_operations shmem_inode_operations = {
2446         .setattr        = shmem_notify_change,
2447         .truncate_range = shmem_truncate_range,
2448 #ifdef CONFIG_TMPFS_POSIX_ACL
2449         .setxattr       = generic_setxattr,
2450         .getxattr       = generic_getxattr,
2451         .listxattr      = generic_listxattr,
2452         .removexattr    = generic_removexattr,
2453         .check_acl      = generic_check_acl,
2454 #endif
2455
2456 };
2457
2458 static const struct inode_operations shmem_dir_inode_operations = {
2459 #ifdef CONFIG_TMPFS
2460         .create         = shmem_create,
2461         .lookup         = simple_lookup,
2462         .link           = shmem_link,
2463         .unlink         = shmem_unlink,
2464         .symlink        = shmem_symlink,
2465         .mkdir          = shmem_mkdir,
2466         .rmdir          = shmem_rmdir,
2467         .mknod          = shmem_mknod,
2468         .rename         = shmem_rename,
2469 #endif
2470 #ifdef CONFIG_TMPFS_POSIX_ACL
2471         .setattr        = shmem_notify_change,
2472         .setxattr       = generic_setxattr,
2473         .getxattr       = generic_getxattr,
2474         .listxattr      = generic_listxattr,
2475         .removexattr    = generic_removexattr,
2476         .check_acl      = generic_check_acl,
2477 #endif
2478 };
2479
2480 static const struct inode_operations shmem_special_inode_operations = {
2481 #ifdef CONFIG_TMPFS_POSIX_ACL
2482         .setattr        = shmem_notify_change,
2483         .setxattr       = generic_setxattr,
2484         .getxattr       = generic_getxattr,
2485         .listxattr      = generic_listxattr,
2486         .removexattr    = generic_removexattr,
2487         .check_acl      = generic_check_acl,
2488 #endif
2489 };
2490
2491 static const struct super_operations shmem_ops = {
2492         .alloc_inode    = shmem_alloc_inode,
2493         .destroy_inode  = shmem_destroy_inode,
2494 #ifdef CONFIG_TMPFS
2495         .statfs         = shmem_statfs,
2496         .remount_fs     = shmem_remount_fs,
2497         .show_options   = shmem_show_options,
2498 #endif
2499         .delete_inode   = shmem_delete_inode,
2500         .drop_inode     = generic_delete_inode,
2501         .put_super      = shmem_put_super,
2502 };
2503
2504 static const struct vm_operations_struct shmem_vm_ops = {
2505         .fault          = shmem_fault,
2506 #ifdef CONFIG_NUMA
2507         .set_policy     = shmem_set_policy,
2508         .get_policy     = shmem_get_policy,
2509 #endif
2510 };
2511
2512
2513 static int shmem_get_sb(struct file_system_type *fs_type,
2514         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
2515 {
2516         return get_sb_nodev(fs_type, flags, data, shmem_fill_super, mnt);
2517 }
2518
2519 static struct file_system_type tmpfs_fs_type = {
2520         .owner          = THIS_MODULE,
2521         .name           = "tmpfs",
2522         .get_sb         = shmem_get_sb,
2523         .kill_sb        = kill_litter_super,
2524 };
2525
2526 int __init init_tmpfs(void)
2527 {
2528         int error;
2529
2530         error = bdi_init(&shmem_backing_dev_info);
2531         if (error)
2532                 goto out4;
2533
2534         error = init_inodecache();
2535         if (error)
2536                 goto out3;
2537
2538         error = register_filesystem(&tmpfs_fs_type);
2539         if (error) {
2540                 printk(KERN_ERR "Could not register tmpfs\n");
2541                 goto out2;
2542         }
2543
2544         shm_mnt = vfs_kern_mount(&tmpfs_fs_type, MS_NOUSER,
2545                                 tmpfs_fs_type.name, NULL);
2546         if (IS_ERR(shm_mnt)) {
2547                 error = PTR_ERR(shm_mnt);
2548                 printk(KERN_ERR "Could not kern_mount tmpfs\n");
2549                 goto out1;
2550         }
2551         return 0;
2552
2553 out1:
2554         unregister_filesystem(&tmpfs_fs_type);
2555 out2:
2556         destroy_inodecache();
2557 out3:
2558         bdi_destroy(&shmem_backing_dev_info);
2559 out4:
2560         shm_mnt = ERR_PTR(error);
2561         return error;
2562 }
2563
2564 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2565 /**
2566  * mem_cgroup_get_shmem_target - find a page or entry assigned to the shmem file
2567  * @inode: the inode to be searched
2568  * @pgoff: the offset to be searched
2569  * @pagep: the pointer for the found page to be stored
2570  * @ent: the pointer for the found swap entry to be stored
2571  *
2572  * If a page is found, refcount of it is incremented. Callers should handle
2573  * these refcount.
2574  */
2575 void mem_cgroup_get_shmem_target(struct inode *inode, pgoff_t pgoff,
2576                                         struct page **pagep, swp_entry_t *ent)
2577 {
2578         swp_entry_t entry = { .val = 0 }, *ptr;
2579         struct page *page = NULL;
2580         struct shmem_inode_info *info = SHMEM_I(inode);
2581
2582         if ((pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
2583                 goto out;
2584
2585         spin_lock(&info->lock);
2586         ptr = shmem_swp_entry(info, pgoff, NULL);
2587 #ifdef CONFIG_SWAP
2588         if (ptr && ptr->val) {
2589                 entry.val = ptr->val;
2590                 page = find_get_page(&swapper_space, entry.val);
2591         } else
2592 #endif
2593                 page = find_get_page(inode->i_mapping, pgoff);
2594         if (ptr)
2595                 shmem_swp_unmap(ptr);
2596         spin_unlock(&info->lock);
2597 out:
2598         *pagep = page;
2599         *ent = entry;
2600 }
2601 #endif
2602
2603 #else /* !CONFIG_SHMEM */
2604
2605 /*
2606  * tiny-shmem: simple shmemfs and tmpfs using ramfs code
2607  *
2608  * This is intended for small system where the benefits of the full
2609  * shmem code (swap-backed and resource-limited) are outweighed by
2610  * their complexity. On systems without swap this code should be
2611  * effectively equivalent, but much lighter weight.
2612  */
2613
2614 #include <linux/ramfs.h>
2615
2616 static struct file_system_type tmpfs_fs_type = {
2617         .name           = "tmpfs",
2618         .get_sb         = ramfs_get_sb,
2619         .kill_sb        = kill_litter_super,
2620 };
2621
2622 int __init init_tmpfs(void)
2623 {
2624         BUG_ON(register_filesystem(&tmpfs_fs_type) != 0);
2625
2626         shm_mnt = kern_mount(&tmpfs_fs_type);
2627         BUG_ON(IS_ERR(shm_mnt));
2628
2629         return 0;
2630 }
2631
2632 int shmem_unuse(swp_entry_t entry, struct page *page)
2633 {
2634         return 0;
2635 }
2636
2637 int shmem_lock(struct file *file, int lock, struct user_struct *user)
2638 {
2639         return 0;
2640 }
2641
2642 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2643 /**
2644  * mem_cgroup_get_shmem_target - find a page or entry assigned to the shmem file
2645  * @inode: the inode to be searched
2646  * @pgoff: the offset to be searched
2647  * @pagep: the pointer for the found page to be stored
2648  * @ent: the pointer for the found swap entry to be stored
2649  *
2650  * If a page is found, refcount of it is incremented. Callers should handle
2651  * these refcount.
2652  */
2653 void mem_cgroup_get_shmem_target(struct inode *inode, pgoff_t pgoff,
2654                                         struct page **pagep, swp_entry_t *ent)
2655 {
2656         struct page *page = NULL;
2657
2658         if ((pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
2659                 goto out;
2660         page = find_get_page(inode->i_mapping, pgoff);
2661 out:
2662         *pagep = page;
2663         *ent = (swp_entry_t){ .val = 0 };
2664 }
2665 #endif
2666
2667 #define shmem_vm_ops                            generic_file_vm_ops
2668 #define shmem_file_operations                   ramfs_file_operations
2669 #define shmem_get_inode(sb, dir, mode, dev, flags)      ramfs_get_inode(sb, dir, mode, dev)
2670 #define shmem_acct_size(flags, size)            0
2671 #define shmem_unacct_size(flags, size)          do {} while (0)
2672 #define SHMEM_MAX_BYTES                         MAX_LFS_FILESIZE
2673
2674 #endif /* CONFIG_SHMEM */
2675
2676 /* common code */
2677
2678 /**
2679  * shmem_file_setup - get an unlinked file living in tmpfs
2680  * @name: name for dentry (to be seen in /proc/<pid>/maps
2681  * @size: size to be set for the file
2682  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
2683  */
2684 struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
2685 {
2686         int error;
2687         struct file *file;
2688         struct inode *inode;
2689         struct path path;
2690         struct dentry *root;
2691         struct qstr this;
2692
2693         if (IS_ERR(shm_mnt))
2694                 return (void *)shm_mnt;
2695
2696         if (size < 0 || size > SHMEM_MAX_BYTES)
2697                 return ERR_PTR(-EINVAL);
2698
2699         if (shmem_acct_size(flags, size))
2700                 return ERR_PTR(-ENOMEM);
2701
2702         error = -ENOMEM;
2703         this.name = name;
2704         this.len = strlen(name);
2705         this.hash = 0; /* will go */
2706         root = shm_mnt->mnt_root;
2707         path.dentry = d_alloc(root, &this);
2708         if (!path.dentry)
2709                 goto put_memory;
2710         path.mnt = mntget(shm_mnt);
2711
2712         error = -ENOSPC;
2713         inode = shmem_get_inode(root->d_sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
2714         if (!inode)
2715                 goto put_dentry;
2716
2717         d_instantiate(path.dentry, inode);
2718         inode->i_size = size;
2719         inode->i_nlink = 0;     /* It is unlinked */
2720 #ifndef CONFIG_MMU
2721         error = ramfs_nommu_expand_for_mapping(inode, size);
2722         if (error)
2723                 goto put_dentry;
2724 #endif
2725
2726         error = -ENFILE;
2727         file = alloc_file(&path, FMODE_WRITE | FMODE_READ,
2728                   &shmem_file_operations);
2729         if (!file)
2730                 goto put_dentry;
2731
2732         return file;
2733
2734 put_dentry:
2735         path_put(&path);
2736 put_memory:
2737         shmem_unacct_size(flags, size);
2738         return ERR_PTR(error);
2739 }
2740 EXPORT_SYMBOL_GPL(shmem_file_setup);
2741
2742 /**
2743  * shmem_zero_setup - setup a shared anonymous mapping
2744  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2745  */
2746 int shmem_zero_setup(struct vm_area_struct *vma)
2747 {
2748         struct file *file;
2749         loff_t size = vma->vm_end - vma->vm_start;
2750
2751         file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2752         if (IS_ERR(file))
2753                 return PTR_ERR(file);
2754
2755         if (vma->vm_file)
2756                 fput(vma->vm_file);
2757         vma->vm_file = file;
2758         vma->vm_ops = &shmem_vm_ops;
2759         return 0;
2760 }