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