177c7a7d2bb38c8e3a52719e3f1e0ca8f9c4deb8
[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  * This file is released under the GPL.
18  */
19
20 /*
21  * This virtual memory filesystem is heavily based on the ramfs. It
22  * extends ramfs by the ability to use swap and honor resource limits
23  * which makes it a completely usable filesystem.
24  */
25
26 #include <linux/module.h>
27 #include <linux/init.h>
28 #include <linux/fs.h>
29 #include <linux/xattr.h>
30 #include <linux/exportfs.h>
31 #include <linux/generic_acl.h>
32 #include <linux/mm.h>
33 #include <linux/mman.h>
34 #include <linux/file.h>
35 #include <linux/swap.h>
36 #include <linux/pagemap.h>
37 #include <linux/string.h>
38 #include <linux/slab.h>
39 #include <linux/backing-dev.h>
40 #include <linux/shmem_fs.h>
41 #include <linux/mount.h>
42 #include <linux/writeback.h>
43 #include <linux/vfs.h>
44 #include <linux/blkdev.h>
45 #include <linux/security.h>
46 #include <linux/swapops.h>
47 #include <linux/mempolicy.h>
48 #include <linux/namei.h>
49 #include <linux/ctype.h>
50 #include <linux/migrate.h>
51 #include <linux/highmem.h>
52 #include <linux/seq_file.h>
53
54 #include <asm/uaccess.h>
55 #include <asm/div64.h>
56 #include <asm/pgtable.h>
57
58 /* This magic number is used in glibc for posix shared memory */
59 #define TMPFS_MAGIC     0x01021994
60
61 #define ENTRIES_PER_PAGE (PAGE_CACHE_SIZE/sizeof(unsigned long))
62 #define ENTRIES_PER_PAGEPAGE (ENTRIES_PER_PAGE*ENTRIES_PER_PAGE)
63 #define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
64
65 #define SHMEM_MAX_INDEX  (SHMEM_NR_DIRECT + (ENTRIES_PER_PAGEPAGE/2) * (ENTRIES_PER_PAGE+1))
66 #define SHMEM_MAX_BYTES  ((unsigned long long)SHMEM_MAX_INDEX << PAGE_CACHE_SHIFT)
67
68 #define VM_ACCT(size)    (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
69
70 /* info->flags needs VM_flags to handle pagein/truncate races efficiently */
71 #define SHMEM_PAGEIN     VM_READ
72 #define SHMEM_TRUNCATE   VM_WRITE
73
74 /* Definition to limit shmem_truncate's steps between cond_rescheds */
75 #define LATENCY_LIMIT    64
76
77 /* Pretend that each entry is of this size in directory's i_size */
78 #define BOGO_DIRENT_SIZE 20
79
80 /* Flag allocation requirements to shmem_getpage and shmem_swp_alloc */
81 enum sgp_type {
82         SGP_READ,       /* don't exceed i_size, don't allocate page */
83         SGP_CACHE,      /* don't exceed i_size, may allocate page */
84         SGP_DIRTY,      /* like SGP_CACHE, but set new page dirty */
85         SGP_WRITE,      /* may exceed i_size, may allocate page */
86 };
87
88 #ifdef CONFIG_TMPFS
89 static unsigned long shmem_default_max_blocks(void)
90 {
91         return totalram_pages / 2;
92 }
93
94 static unsigned long shmem_default_max_inodes(void)
95 {
96         return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
97 }
98 #endif
99
100 static int shmem_getpage(struct inode *inode, unsigned long idx,
101                          struct page **pagep, enum sgp_type sgp, int *type);
102
103 static inline struct page *shmem_dir_alloc(gfp_t gfp_mask)
104 {
105         /*
106          * The above definition of ENTRIES_PER_PAGE, and the use of
107          * BLOCKS_PER_PAGE on indirect pages, assume PAGE_CACHE_SIZE:
108          * might be reconsidered if it ever diverges from PAGE_SIZE.
109          *
110          * Mobility flags are masked out as swap vectors cannot move
111          */
112         return alloc_pages((gfp_mask & ~GFP_MOVABLE_MASK) | __GFP_ZERO,
113                                 PAGE_CACHE_SHIFT-PAGE_SHIFT);
114 }
115
116 static inline void shmem_dir_free(struct page *page)
117 {
118         __free_pages(page, PAGE_CACHE_SHIFT-PAGE_SHIFT);
119 }
120
121 static struct page **shmem_dir_map(struct page *page)
122 {
123         return (struct page **)kmap_atomic(page, KM_USER0);
124 }
125
126 static inline void shmem_dir_unmap(struct page **dir)
127 {
128         kunmap_atomic(dir, KM_USER0);
129 }
130
131 static swp_entry_t *shmem_swp_map(struct page *page)
132 {
133         return (swp_entry_t *)kmap_atomic(page, KM_USER1);
134 }
135
136 static inline void shmem_swp_balance_unmap(void)
137 {
138         /*
139          * When passing a pointer to an i_direct entry, to code which
140          * also handles indirect entries and so will shmem_swp_unmap,
141          * we must arrange for the preempt count to remain in balance.
142          * What kmap_atomic of a lowmem page does depends on config
143          * and architecture, so pretend to kmap_atomic some lowmem page.
144          */
145         (void) kmap_atomic(ZERO_PAGE(0), KM_USER1);
146 }
147
148 static inline void shmem_swp_unmap(swp_entry_t *entry)
149 {
150         kunmap_atomic(entry, KM_USER1);
151 }
152
153 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
154 {
155         return sb->s_fs_info;
156 }
157
158 /*
159  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
160  * for shared memory and for shared anonymous (/dev/zero) mappings
161  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
162  * consistent with the pre-accounting of private mappings ...
163  */
164 static inline int shmem_acct_size(unsigned long flags, loff_t size)
165 {
166         return (flags & VM_ACCOUNT)?
167                 security_vm_enough_memory(VM_ACCT(size)): 0;
168 }
169
170 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
171 {
172         if (flags & VM_ACCOUNT)
173                 vm_unacct_memory(VM_ACCT(size));
174 }
175
176 /*
177  * ... whereas tmpfs objects are accounted incrementally as
178  * pages are allocated, in order to allow huge sparse files.
179  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
180  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
181  */
182 static inline int shmem_acct_block(unsigned long flags)
183 {
184         return (flags & VM_ACCOUNT)?
185                 0: security_vm_enough_memory(VM_ACCT(PAGE_CACHE_SIZE));
186 }
187
188 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
189 {
190         if (!(flags & VM_ACCOUNT))
191                 vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
192 }
193
194 static const struct super_operations shmem_ops;
195 static const struct address_space_operations shmem_aops;
196 static const struct file_operations shmem_file_operations;
197 static const struct inode_operations shmem_inode_operations;
198 static const struct inode_operations shmem_dir_inode_operations;
199 static const struct inode_operations shmem_special_inode_operations;
200 static struct vm_operations_struct shmem_vm_ops;
201
202 static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
203         .ra_pages       = 0,    /* No readahead */
204         .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
205         .unplug_io_fn   = default_unplug_io_fn,
206 };
207
208 static LIST_HEAD(shmem_swaplist);
209 static DEFINE_MUTEX(shmem_swaplist_mutex);
210
211 static void shmem_free_blocks(struct inode *inode, long pages)
212 {
213         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
214         if (sbinfo->max_blocks) {
215                 spin_lock(&sbinfo->stat_lock);
216                 sbinfo->free_blocks += pages;
217                 inode->i_blocks -= pages*BLOCKS_PER_PAGE;
218                 spin_unlock(&sbinfo->stat_lock);
219         }
220 }
221
222 static int shmem_reserve_inode(struct super_block *sb)
223 {
224         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
225         if (sbinfo->max_inodes) {
226                 spin_lock(&sbinfo->stat_lock);
227                 if (!sbinfo->free_inodes) {
228                         spin_unlock(&sbinfo->stat_lock);
229                         return -ENOSPC;
230                 }
231                 sbinfo->free_inodes--;
232                 spin_unlock(&sbinfo->stat_lock);
233         }
234         return 0;
235 }
236
237 static void shmem_free_inode(struct super_block *sb)
238 {
239         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
240         if (sbinfo->max_inodes) {
241                 spin_lock(&sbinfo->stat_lock);
242                 sbinfo->free_inodes++;
243                 spin_unlock(&sbinfo->stat_lock);
244         }
245 }
246
247 /**
248  * shmem_recalc_inode - recalculate the size of an inode
249  * @inode: inode to recalc
250  *
251  * We have to calculate the free blocks since the mm can drop
252  * undirtied hole pages behind our back.
253  *
254  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
255  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
256  *
257  * It has to be called with the spinlock held.
258  */
259 static void shmem_recalc_inode(struct inode *inode)
260 {
261         struct shmem_inode_info *info = SHMEM_I(inode);
262         long freed;
263
264         freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
265         if (freed > 0) {
266                 info->alloced -= freed;
267                 shmem_unacct_blocks(info->flags, freed);
268                 shmem_free_blocks(inode, freed);
269         }
270 }
271
272 /**
273  * shmem_swp_entry - find the swap vector position in the info structure
274  * @info:  info structure for the inode
275  * @index: index of the page to find
276  * @page:  optional page to add to the structure. Has to be preset to
277  *         all zeros
278  *
279  * If there is no space allocated yet it will return NULL when
280  * page is NULL, else it will use the page for the needed block,
281  * setting it to NULL on return to indicate that it has been used.
282  *
283  * The swap vector is organized the following way:
284  *
285  * There are SHMEM_NR_DIRECT entries directly stored in the
286  * shmem_inode_info structure. So small files do not need an addional
287  * allocation.
288  *
289  * For pages with index > SHMEM_NR_DIRECT there is the pointer
290  * i_indirect which points to a page which holds in the first half
291  * doubly indirect blocks, in the second half triple indirect blocks:
292  *
293  * For an artificial ENTRIES_PER_PAGE = 4 this would lead to the
294  * following layout (for SHMEM_NR_DIRECT == 16):
295  *
296  * i_indirect -> dir --> 16-19
297  *            |      +-> 20-23
298  *            |
299  *            +-->dir2 --> 24-27
300  *            |        +-> 28-31
301  *            |        +-> 32-35
302  *            |        +-> 36-39
303  *            |
304  *            +-->dir3 --> 40-43
305  *                     +-> 44-47
306  *                     +-> 48-51
307  *                     +-> 52-55
308  */
309 static swp_entry_t *shmem_swp_entry(struct shmem_inode_info *info, unsigned long index, struct page **page)
310 {
311         unsigned long offset;
312         struct page **dir;
313         struct page *subdir;
314
315         if (index < SHMEM_NR_DIRECT) {
316                 shmem_swp_balance_unmap();
317                 return info->i_direct+index;
318         }
319         if (!info->i_indirect) {
320                 if (page) {
321                         info->i_indirect = *page;
322                         *page = NULL;
323                 }
324                 return NULL;                    /* need another page */
325         }
326
327         index -= SHMEM_NR_DIRECT;
328         offset = index % ENTRIES_PER_PAGE;
329         index /= ENTRIES_PER_PAGE;
330         dir = shmem_dir_map(info->i_indirect);
331
332         if (index >= ENTRIES_PER_PAGE/2) {
333                 index -= ENTRIES_PER_PAGE/2;
334                 dir += ENTRIES_PER_PAGE/2 + index/ENTRIES_PER_PAGE;
335                 index %= ENTRIES_PER_PAGE;
336                 subdir = *dir;
337                 if (!subdir) {
338                         if (page) {
339                                 *dir = *page;
340                                 *page = NULL;
341                         }
342                         shmem_dir_unmap(dir);
343                         return NULL;            /* need another page */
344                 }
345                 shmem_dir_unmap(dir);
346                 dir = shmem_dir_map(subdir);
347         }
348
349         dir += index;
350         subdir = *dir;
351         if (!subdir) {
352                 if (!page || !(subdir = *page)) {
353                         shmem_dir_unmap(dir);
354                         return NULL;            /* need a page */
355                 }
356                 *dir = subdir;
357                 *page = NULL;
358         }
359         shmem_dir_unmap(dir);
360         return shmem_swp_map(subdir) + offset;
361 }
362
363 static void shmem_swp_set(struct shmem_inode_info *info, swp_entry_t *entry, unsigned long value)
364 {
365         long incdec = value? 1: -1;
366
367         entry->val = value;
368         info->swapped += incdec;
369         if ((unsigned long)(entry - info->i_direct) >= SHMEM_NR_DIRECT) {
370                 struct page *page = kmap_atomic_to_page(entry);
371                 set_page_private(page, page_private(page) + incdec);
372         }
373 }
374
375 /**
376  * shmem_swp_alloc - get the position of the swap entry for the page.
377  * @info:       info structure for the inode
378  * @index:      index of the page to find
379  * @sgp:        check and recheck i_size? skip allocation?
380  *
381  * If the entry does not exist, allocate it.
382  */
383 static swp_entry_t *shmem_swp_alloc(struct shmem_inode_info *info, unsigned long index, enum sgp_type sgp)
384 {
385         struct inode *inode = &info->vfs_inode;
386         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
387         struct page *page = NULL;
388         swp_entry_t *entry;
389
390         if (sgp != SGP_WRITE &&
391             ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode))
392                 return ERR_PTR(-EINVAL);
393
394         while (!(entry = shmem_swp_entry(info, index, &page))) {
395                 if (sgp == SGP_READ)
396                         return shmem_swp_map(ZERO_PAGE(0));
397                 /*
398                  * Test free_blocks against 1 not 0, since we have 1 data
399                  * page (and perhaps indirect index pages) yet to allocate:
400                  * a waste to allocate index if we cannot allocate data.
401                  */
402                 if (sbinfo->max_blocks) {
403                         spin_lock(&sbinfo->stat_lock);
404                         if (sbinfo->free_blocks <= 1) {
405                                 spin_unlock(&sbinfo->stat_lock);
406                                 return ERR_PTR(-ENOSPC);
407                         }
408                         sbinfo->free_blocks--;
409                         inode->i_blocks += BLOCKS_PER_PAGE;
410                         spin_unlock(&sbinfo->stat_lock);
411                 }
412
413                 spin_unlock(&info->lock);
414                 page = shmem_dir_alloc(mapping_gfp_mask(inode->i_mapping));
415                 if (page)
416                         set_page_private(page, 0);
417                 spin_lock(&info->lock);
418
419                 if (!page) {
420                         shmem_free_blocks(inode, 1);
421                         return ERR_PTR(-ENOMEM);
422                 }
423                 if (sgp != SGP_WRITE &&
424                     ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
425                         entry = ERR_PTR(-EINVAL);
426                         break;
427                 }
428                 if (info->next_index <= index)
429                         info->next_index = index + 1;
430         }
431         if (page) {
432                 /* another task gave its page, or truncated the file */
433                 shmem_free_blocks(inode, 1);
434                 shmem_dir_free(page);
435         }
436         if (info->next_index <= index && !IS_ERR(entry))
437                 info->next_index = index + 1;
438         return entry;
439 }
440
441 /**
442  * shmem_free_swp - free some swap entries in a directory
443  * @dir:        pointer to the directory
444  * @edir:       pointer after last entry of the directory
445  * @punch_lock: pointer to spinlock when needed for the holepunch case
446  */
447 static int shmem_free_swp(swp_entry_t *dir, swp_entry_t *edir,
448                                                 spinlock_t *punch_lock)
449 {
450         spinlock_t *punch_unlock = NULL;
451         swp_entry_t *ptr;
452         int freed = 0;
453
454         for (ptr = dir; ptr < edir; ptr++) {
455                 if (ptr->val) {
456                         if (unlikely(punch_lock)) {
457                                 punch_unlock = punch_lock;
458                                 punch_lock = NULL;
459                                 spin_lock(punch_unlock);
460                                 if (!ptr->val)
461                                         continue;
462                         }
463                         free_swap_and_cache(*ptr);
464                         *ptr = (swp_entry_t){0};
465                         freed++;
466                 }
467         }
468         if (punch_unlock)
469                 spin_unlock(punch_unlock);
470         return freed;
471 }
472
473 static int shmem_map_and_free_swp(struct page *subdir, int offset,
474                 int limit, struct page ***dir, spinlock_t *punch_lock)
475 {
476         swp_entry_t *ptr;
477         int freed = 0;
478
479         ptr = shmem_swp_map(subdir);
480         for (; offset < limit; offset += LATENCY_LIMIT) {
481                 int size = limit - offset;
482                 if (size > LATENCY_LIMIT)
483                         size = LATENCY_LIMIT;
484                 freed += shmem_free_swp(ptr+offset, ptr+offset+size,
485                                                         punch_lock);
486                 if (need_resched()) {
487                         shmem_swp_unmap(ptr);
488                         if (*dir) {
489                                 shmem_dir_unmap(*dir);
490                                 *dir = NULL;
491                         }
492                         cond_resched();
493                         ptr = shmem_swp_map(subdir);
494                 }
495         }
496         shmem_swp_unmap(ptr);
497         return freed;
498 }
499
500 static void shmem_free_pages(struct list_head *next)
501 {
502         struct page *page;
503         int freed = 0;
504
505         do {
506                 page = container_of(next, struct page, lru);
507                 next = next->next;
508                 shmem_dir_free(page);
509                 freed++;
510                 if (freed >= LATENCY_LIMIT) {
511                         cond_resched();
512                         freed = 0;
513                 }
514         } while (next);
515 }
516
517 static void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end)
518 {
519         struct shmem_inode_info *info = SHMEM_I(inode);
520         unsigned long idx;
521         unsigned long size;
522         unsigned long limit;
523         unsigned long stage;
524         unsigned long diroff;
525         struct page **dir;
526         struct page *topdir;
527         struct page *middir;
528         struct page *subdir;
529         swp_entry_t *ptr;
530         LIST_HEAD(pages_to_free);
531         long nr_pages_to_free = 0;
532         long nr_swaps_freed = 0;
533         int offset;
534         int freed;
535         int punch_hole;
536         spinlock_t *needs_lock;
537         spinlock_t *punch_lock;
538         unsigned long upper_limit;
539
540         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
541         idx = (start + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
542         if (idx >= info->next_index)
543                 return;
544
545         spin_lock(&info->lock);
546         info->flags |= SHMEM_TRUNCATE;
547         if (likely(end == (loff_t) -1)) {
548                 limit = info->next_index;
549                 upper_limit = SHMEM_MAX_INDEX;
550                 info->next_index = idx;
551                 needs_lock = NULL;
552                 punch_hole = 0;
553         } else {
554                 if (end + 1 >= inode->i_size) { /* we may free a little more */
555                         limit = (inode->i_size + PAGE_CACHE_SIZE - 1) >>
556                                                         PAGE_CACHE_SHIFT;
557                         upper_limit = SHMEM_MAX_INDEX;
558                 } else {
559                         limit = (end + 1) >> PAGE_CACHE_SHIFT;
560                         upper_limit = limit;
561                 }
562                 needs_lock = &info->lock;
563                 punch_hole = 1;
564         }
565
566         topdir = info->i_indirect;
567         if (topdir && idx <= SHMEM_NR_DIRECT && !punch_hole) {
568                 info->i_indirect = NULL;
569                 nr_pages_to_free++;
570                 list_add(&topdir->lru, &pages_to_free);
571         }
572         spin_unlock(&info->lock);
573
574         if (info->swapped && idx < SHMEM_NR_DIRECT) {
575                 ptr = info->i_direct;
576                 size = limit;
577                 if (size > SHMEM_NR_DIRECT)
578                         size = SHMEM_NR_DIRECT;
579                 nr_swaps_freed = shmem_free_swp(ptr+idx, ptr+size, needs_lock);
580         }
581
582         /*
583          * If there are no indirect blocks or we are punching a hole
584          * below indirect blocks, nothing to be done.
585          */
586         if (!topdir || limit <= SHMEM_NR_DIRECT)
587                 goto done2;
588
589         /*
590          * The truncation case has already dropped info->lock, and we're safe
591          * because i_size and next_index have already been lowered, preventing
592          * access beyond.  But in the punch_hole case, we still need to take
593          * the lock when updating the swap directory, because there might be
594          * racing accesses by shmem_getpage(SGP_CACHE), shmem_unuse_inode or
595          * shmem_writepage.  However, whenever we find we can remove a whole
596          * directory page (not at the misaligned start or end of the range),
597          * we first NULLify its pointer in the level above, and then have no
598          * need to take the lock when updating its contents: needs_lock and
599          * punch_lock (either pointing to info->lock or NULL) manage this.
600          */
601
602         upper_limit -= SHMEM_NR_DIRECT;
603         limit -= SHMEM_NR_DIRECT;
604         idx = (idx > SHMEM_NR_DIRECT)? (idx - SHMEM_NR_DIRECT): 0;
605         offset = idx % ENTRIES_PER_PAGE;
606         idx -= offset;
607
608         dir = shmem_dir_map(topdir);
609         stage = ENTRIES_PER_PAGEPAGE/2;
610         if (idx < ENTRIES_PER_PAGEPAGE/2) {
611                 middir = topdir;
612                 diroff = idx/ENTRIES_PER_PAGE;
613         } else {
614                 dir += ENTRIES_PER_PAGE/2;
615                 dir += (idx - ENTRIES_PER_PAGEPAGE/2)/ENTRIES_PER_PAGEPAGE;
616                 while (stage <= idx)
617                         stage += ENTRIES_PER_PAGEPAGE;
618                 middir = *dir;
619                 if (*dir) {
620                         diroff = ((idx - ENTRIES_PER_PAGEPAGE/2) %
621                                 ENTRIES_PER_PAGEPAGE) / ENTRIES_PER_PAGE;
622                         if (!diroff && !offset && upper_limit >= stage) {
623                                 if (needs_lock) {
624                                         spin_lock(needs_lock);
625                                         *dir = NULL;
626                                         spin_unlock(needs_lock);
627                                         needs_lock = NULL;
628                                 } else
629                                         *dir = NULL;
630                                 nr_pages_to_free++;
631                                 list_add(&middir->lru, &pages_to_free);
632                         }
633                         shmem_dir_unmap(dir);
634                         dir = shmem_dir_map(middir);
635                 } else {
636                         diroff = 0;
637                         offset = 0;
638                         idx = stage;
639                 }
640         }
641
642         for (; idx < limit; idx += ENTRIES_PER_PAGE, diroff++) {
643                 if (unlikely(idx == stage)) {
644                         shmem_dir_unmap(dir);
645                         dir = shmem_dir_map(topdir) +
646                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
647                         while (!*dir) {
648                                 dir++;
649                                 idx += ENTRIES_PER_PAGEPAGE;
650                                 if (idx >= limit)
651                                         goto done1;
652                         }
653                         stage = idx + ENTRIES_PER_PAGEPAGE;
654                         middir = *dir;
655                         if (punch_hole)
656                                 needs_lock = &info->lock;
657                         if (upper_limit >= stage) {
658                                 if (needs_lock) {
659                                         spin_lock(needs_lock);
660                                         *dir = NULL;
661                                         spin_unlock(needs_lock);
662                                         needs_lock = NULL;
663                                 } else
664                                         *dir = NULL;
665                                 nr_pages_to_free++;
666                                 list_add(&middir->lru, &pages_to_free);
667                         }
668                         shmem_dir_unmap(dir);
669                         cond_resched();
670                         dir = shmem_dir_map(middir);
671                         diroff = 0;
672                 }
673                 punch_lock = needs_lock;
674                 subdir = dir[diroff];
675                 if (subdir && !offset && upper_limit-idx >= ENTRIES_PER_PAGE) {
676                         if (needs_lock) {
677                                 spin_lock(needs_lock);
678                                 dir[diroff] = NULL;
679                                 spin_unlock(needs_lock);
680                                 punch_lock = NULL;
681                         } else
682                                 dir[diroff] = NULL;
683                         nr_pages_to_free++;
684                         list_add(&subdir->lru, &pages_to_free);
685                 }
686                 if (subdir && page_private(subdir) /* has swap entries */) {
687                         size = limit - idx;
688                         if (size > ENTRIES_PER_PAGE)
689                                 size = ENTRIES_PER_PAGE;
690                         freed = shmem_map_and_free_swp(subdir,
691                                         offset, size, &dir, punch_lock);
692                         if (!dir)
693                                 dir = shmem_dir_map(middir);
694                         nr_swaps_freed += freed;
695                         if (offset || punch_lock) {
696                                 spin_lock(&info->lock);
697                                 set_page_private(subdir,
698                                         page_private(subdir) - freed);
699                                 spin_unlock(&info->lock);
700                         } else
701                                 BUG_ON(page_private(subdir) != freed);
702                 }
703                 offset = 0;
704         }
705 done1:
706         shmem_dir_unmap(dir);
707 done2:
708         if (inode->i_mapping->nrpages && (info->flags & SHMEM_PAGEIN)) {
709                 /*
710                  * Call truncate_inode_pages again: racing shmem_unuse_inode
711                  * may have swizzled a page in from swap since vmtruncate or
712                  * generic_delete_inode did it, before we lowered next_index.
713                  * Also, though shmem_getpage checks i_size before adding to
714                  * cache, no recheck after: so fix the narrow window there too.
715                  *
716                  * Recalling truncate_inode_pages_range and unmap_mapping_range
717                  * every time for punch_hole (which never got a chance to clear
718                  * SHMEM_PAGEIN at the start of vmtruncate_range) is expensive,
719                  * yet hardly ever necessary: try to optimize them out later.
720                  */
721                 truncate_inode_pages_range(inode->i_mapping, start, end);
722                 if (punch_hole)
723                         unmap_mapping_range(inode->i_mapping, start,
724                                                         end - start, 1);
725         }
726
727         spin_lock(&info->lock);
728         info->flags &= ~SHMEM_TRUNCATE;
729         info->swapped -= nr_swaps_freed;
730         if (nr_pages_to_free)
731                 shmem_free_blocks(inode, nr_pages_to_free);
732         shmem_recalc_inode(inode);
733         spin_unlock(&info->lock);
734
735         /*
736          * Empty swap vector directory pages to be freed?
737          */
738         if (!list_empty(&pages_to_free)) {
739                 pages_to_free.prev->next = NULL;
740                 shmem_free_pages(pages_to_free.next);
741         }
742 }
743
744 static void shmem_truncate(struct inode *inode)
745 {
746         shmem_truncate_range(inode, inode->i_size, (loff_t)-1);
747 }
748
749 static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
750 {
751         struct inode *inode = dentry->d_inode;
752         struct page *page = NULL;
753         int error;
754
755         if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
756                 if (attr->ia_size < inode->i_size) {
757                         /*
758                          * If truncating down to a partial page, then
759                          * if that page is already allocated, hold it
760                          * in memory until the truncation is over, so
761                          * truncate_partial_page cannnot miss it were
762                          * it assigned to swap.
763                          */
764                         if (attr->ia_size & (PAGE_CACHE_SIZE-1)) {
765                                 (void) shmem_getpage(inode,
766                                         attr->ia_size>>PAGE_CACHE_SHIFT,
767                                                 &page, SGP_READ, NULL);
768                                 if (page)
769                                         unlock_page(page);
770                         }
771                         /*
772                          * Reset SHMEM_PAGEIN flag so that shmem_truncate can
773                          * detect if any pages might have been added to cache
774                          * after truncate_inode_pages.  But we needn't bother
775                          * if it's being fully truncated to zero-length: the
776                          * nrpages check is efficient enough in that case.
777                          */
778                         if (attr->ia_size) {
779                                 struct shmem_inode_info *info = SHMEM_I(inode);
780                                 spin_lock(&info->lock);
781                                 info->flags &= ~SHMEM_PAGEIN;
782                                 spin_unlock(&info->lock);
783                         }
784                 }
785         }
786
787         error = inode_change_ok(inode, attr);
788         if (!error)
789                 error = inode_setattr(inode, attr);
790 #ifdef CONFIG_TMPFS_POSIX_ACL
791         if (!error && (attr->ia_valid & ATTR_MODE))
792                 error = generic_acl_chmod(inode, &shmem_acl_ops);
793 #endif
794         if (page)
795                 page_cache_release(page);
796         return error;
797 }
798
799 static void shmem_delete_inode(struct inode *inode)
800 {
801         struct shmem_inode_info *info = SHMEM_I(inode);
802
803         if (inode->i_op->truncate == shmem_truncate) {
804                 truncate_inode_pages(inode->i_mapping, 0);
805                 shmem_unacct_size(info->flags, inode->i_size);
806                 inode->i_size = 0;
807                 shmem_truncate(inode);
808                 if (!list_empty(&info->swaplist)) {
809                         mutex_lock(&shmem_swaplist_mutex);
810                         list_del_init(&info->swaplist);
811                         mutex_unlock(&shmem_swaplist_mutex);
812                 }
813         }
814         BUG_ON(inode->i_blocks);
815         shmem_free_inode(inode->i_sb);
816         clear_inode(inode);
817 }
818
819 static inline int shmem_find_swp(swp_entry_t entry, swp_entry_t *dir, swp_entry_t *edir)
820 {
821         swp_entry_t *ptr;
822
823         for (ptr = dir; ptr < edir; ptr++) {
824                 if (ptr->val == entry.val)
825                         return ptr - dir;
826         }
827         return -1;
828 }
829
830 static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t entry, struct page *page)
831 {
832         struct inode *inode;
833         unsigned long idx;
834         unsigned long size;
835         unsigned long limit;
836         unsigned long stage;
837         struct page **dir;
838         struct page *subdir;
839         swp_entry_t *ptr;
840         int offset;
841         int error;
842
843         idx = 0;
844         ptr = info->i_direct;
845         spin_lock(&info->lock);
846         if (!info->swapped) {
847                 list_del_init(&info->swaplist);
848                 goto lost2;
849         }
850         limit = info->next_index;
851         size = limit;
852         if (size > SHMEM_NR_DIRECT)
853                 size = SHMEM_NR_DIRECT;
854         offset = shmem_find_swp(entry, ptr, ptr+size);
855         if (offset >= 0)
856                 goto found;
857         if (!info->i_indirect)
858                 goto lost2;
859
860         dir = shmem_dir_map(info->i_indirect);
861         stage = SHMEM_NR_DIRECT + ENTRIES_PER_PAGEPAGE/2;
862
863         for (idx = SHMEM_NR_DIRECT; idx < limit; idx += ENTRIES_PER_PAGE, dir++) {
864                 if (unlikely(idx == stage)) {
865                         shmem_dir_unmap(dir-1);
866                         if (cond_resched_lock(&info->lock)) {
867                                 /* check it has not been truncated */
868                                 if (limit > info->next_index) {
869                                         limit = info->next_index;
870                                         if (idx >= limit)
871                                                 goto lost2;
872                                 }
873                         }
874                         dir = shmem_dir_map(info->i_indirect) +
875                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
876                         while (!*dir) {
877                                 dir++;
878                                 idx += ENTRIES_PER_PAGEPAGE;
879                                 if (idx >= limit)
880                                         goto lost1;
881                         }
882                         stage = idx + ENTRIES_PER_PAGEPAGE;
883                         subdir = *dir;
884                         shmem_dir_unmap(dir);
885                         dir = shmem_dir_map(subdir);
886                 }
887                 subdir = *dir;
888                 if (subdir && page_private(subdir)) {
889                         ptr = shmem_swp_map(subdir);
890                         size = limit - idx;
891                         if (size > ENTRIES_PER_PAGE)
892                                 size = ENTRIES_PER_PAGE;
893                         offset = shmem_find_swp(entry, ptr, ptr+size);
894                         shmem_swp_unmap(ptr);
895                         if (offset >= 0) {
896                                 shmem_dir_unmap(dir);
897                                 goto found;
898                         }
899                 }
900         }
901 lost1:
902         shmem_dir_unmap(dir-1);
903 lost2:
904         spin_unlock(&info->lock);
905         return 0;
906 found:
907         idx += offset;
908         inode = igrab(&info->vfs_inode);
909         spin_unlock(&info->lock);
910
911         /*
912          * Move _head_ to start search for next from here.
913          * But be careful: shmem_delete_inode checks list_empty without taking
914          * mutex, and there's an instant in list_move_tail when info->swaplist
915          * would appear empty, if it were the only one on shmem_swaplist.  We
916          * could avoid doing it if inode NULL; or use this minor optimization.
917          */
918         if (shmem_swaplist.next != &info->swaplist)
919                 list_move_tail(&shmem_swaplist, &info->swaplist);
920         mutex_unlock(&shmem_swaplist_mutex);
921
922         error = 1;
923         if (!inode)
924                 goto out;
925         /* Precharge page while we can wait, compensate afterwards */
926         error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL);
927         if (error)
928                 goto out;
929         error = radix_tree_preload(GFP_KERNEL);
930         if (error)
931                 goto uncharge;
932         error = 1;
933
934         spin_lock(&info->lock);
935         ptr = shmem_swp_entry(info, idx, NULL);
936         if (ptr && ptr->val == entry.val)
937                 error = add_to_page_cache(page, inode->i_mapping,
938                                                 idx, GFP_NOWAIT);
939         if (error == -EEXIST) {
940                 struct page *filepage = find_get_page(inode->i_mapping, idx);
941                 error = 1;
942                 if (filepage) {
943                         /*
944                          * There might be a more uptodate page coming down
945                          * from a stacked writepage: forget our swappage if so.
946                          */
947                         if (PageUptodate(filepage))
948                                 error = 0;
949                         page_cache_release(filepage);
950                 }
951         }
952         if (!error) {
953                 delete_from_swap_cache(page);
954                 set_page_dirty(page);
955                 info->flags |= SHMEM_PAGEIN;
956                 shmem_swp_set(info, ptr, 0);
957                 swap_free(entry);
958                 error = 1;      /* not an error, but entry was found */
959         }
960         if (ptr)
961                 shmem_swp_unmap(ptr);
962         spin_unlock(&info->lock);
963         radix_tree_preload_end();
964 uncharge:
965         mem_cgroup_uncharge_page(page);
966 out:
967         unlock_page(page);
968         page_cache_release(page);
969         iput(inode);            /* allows for NULL */
970         return error;
971 }
972
973 /*
974  * shmem_unuse() search for an eventually swapped out shmem page.
975  */
976 int shmem_unuse(swp_entry_t entry, struct page *page)
977 {
978         struct list_head *p, *next;
979         struct shmem_inode_info *info;
980         int found = 0;
981
982         mutex_lock(&shmem_swaplist_mutex);
983         list_for_each_safe(p, next, &shmem_swaplist) {
984                 info = list_entry(p, struct shmem_inode_info, swaplist);
985                 found = shmem_unuse_inode(info, entry, page);
986                 cond_resched();
987                 if (found)
988                         goto out;
989         }
990         mutex_unlock(&shmem_swaplist_mutex);
991 out:    return found;   /* 0 or 1 or -ENOMEM */
992 }
993
994 /*
995  * Move the page from the page cache to the swap cache.
996  */
997 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
998 {
999         struct shmem_inode_info *info;
1000         swp_entry_t *entry, swap;
1001         struct address_space *mapping;
1002         unsigned long index;
1003         struct inode *inode;
1004
1005         BUG_ON(!PageLocked(page));
1006         mapping = page->mapping;
1007         index = page->index;
1008         inode = mapping->host;
1009         info = SHMEM_I(inode);
1010         if (info->flags & VM_LOCKED)
1011                 goto redirty;
1012         if (!total_swap_pages)
1013                 goto redirty;
1014
1015         /*
1016          * shmem_backing_dev_info's capabilities prevent regular writeback or
1017          * sync from ever calling shmem_writepage; but a stacking filesystem
1018          * may use the ->writepage of its underlying filesystem, in which case
1019          * tmpfs should write out to swap only in response to memory pressure,
1020          * and not for pdflush or sync.  However, in those cases, we do still
1021          * want to check if there's a redundant swappage to be discarded.
1022          */
1023         if (wbc->for_reclaim)
1024                 swap = get_swap_page();
1025         else
1026                 swap.val = 0;
1027
1028         spin_lock(&info->lock);
1029         if (index >= info->next_index) {
1030                 BUG_ON(!(info->flags & SHMEM_TRUNCATE));
1031                 goto unlock;
1032         }
1033         entry = shmem_swp_entry(info, index, NULL);
1034         if (entry->val) {
1035                 /*
1036                  * The more uptodate page coming down from a stacked
1037                  * writepage should replace our old swappage.
1038                  */
1039                 free_swap_and_cache(*entry);
1040                 shmem_swp_set(info, entry, 0);
1041         }
1042         shmem_recalc_inode(inode);
1043
1044         if (swap.val && add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
1045                 remove_from_page_cache(page);
1046                 shmem_swp_set(info, entry, swap.val);
1047                 shmem_swp_unmap(entry);
1048                 if (list_empty(&info->swaplist))
1049                         inode = igrab(inode);
1050                 else
1051                         inode = NULL;
1052                 spin_unlock(&info->lock);
1053                 swap_duplicate(swap);
1054                 BUG_ON(page_mapped(page));
1055                 page_cache_release(page);       /* pagecache ref */
1056                 set_page_dirty(page);
1057                 unlock_page(page);
1058                 if (inode) {
1059                         mutex_lock(&shmem_swaplist_mutex);
1060                         /* move instead of add in case we're racing */
1061                         list_move_tail(&info->swaplist, &shmem_swaplist);
1062                         mutex_unlock(&shmem_swaplist_mutex);
1063                         iput(inode);
1064                 }
1065                 return 0;
1066         }
1067
1068         shmem_swp_unmap(entry);
1069 unlock:
1070         spin_unlock(&info->lock);
1071         swap_free(swap);
1072 redirty:
1073         set_page_dirty(page);
1074         if (wbc->for_reclaim)
1075                 return AOP_WRITEPAGE_ACTIVATE;  /* Return with page locked */
1076         unlock_page(page);
1077         return 0;
1078 }
1079
1080 #ifdef CONFIG_NUMA
1081 #ifdef CONFIG_TMPFS
1082 static int shmem_parse_mpol(char *value, unsigned short *policy,
1083                         unsigned short *mode_flags, nodemask_t *policy_nodes)
1084 {
1085         char *nodelist = strchr(value, ':');
1086         char *flags = strchr(value, '=');
1087         int err = 1;
1088
1089         if (nodelist) {
1090                 /* NUL-terminate policy string */
1091                 *nodelist++ = '\0';
1092                 if (nodelist_parse(nodelist, *policy_nodes))
1093                         goto out;
1094                 if (!nodes_subset(*policy_nodes, node_states[N_HIGH_MEMORY]))
1095                         goto out;
1096         }
1097         if (flags)
1098                 *flags++ = '\0';
1099         if (!strcmp(value, "default")) {
1100                 *policy = MPOL_DEFAULT;
1101                 /* Don't allow a nodelist */
1102                 if (!nodelist)
1103                         err = 0;
1104         } else if (!strcmp(value, "prefer")) {
1105                 *policy = MPOL_PREFERRED;
1106                 /* Insist on a nodelist of one node only */
1107                 if (nodelist) {
1108                         char *rest = nodelist;
1109                         while (isdigit(*rest))
1110                                 rest++;
1111                         if (!*rest)
1112                                 err = 0;
1113                 }
1114         } else if (!strcmp(value, "bind")) {
1115                 *policy = MPOL_BIND;
1116                 /* Insist on a nodelist */
1117                 if (nodelist)
1118                         err = 0;
1119         } else if (!strcmp(value, "interleave")) {
1120                 *policy = MPOL_INTERLEAVE;
1121                 /*
1122                  * Default to online nodes with memory if no nodelist
1123                  */
1124                 if (!nodelist)
1125                         *policy_nodes = node_states[N_HIGH_MEMORY];
1126                 err = 0;
1127         }
1128
1129         *mode_flags = 0;
1130         if (flags) {
1131                 /*
1132                  * Currently, we only support two mutually exclusive
1133                  * mode flags.
1134                  */
1135                 if (!strcmp(flags, "static"))
1136                         *mode_flags |= MPOL_F_STATIC_NODES;
1137                 else if (!strcmp(flags, "relative"))
1138                         *mode_flags |= MPOL_F_RELATIVE_NODES;
1139                 else
1140                         err = 1;        /* unrecognized flag */
1141         }
1142 out:
1143         /* Restore string for error message */
1144         if (nodelist)
1145                 *--nodelist = ':';
1146         if (flags)
1147                 *--flags = '=';
1148         return err;
1149 }
1150
1151 static void shmem_show_mpol(struct seq_file *seq, unsigned short policy,
1152                         unsigned short flags, const nodemask_t policy_nodes)
1153 {
1154         char *policy_string;
1155
1156         switch (policy) {
1157         case MPOL_PREFERRED:
1158                 policy_string = "prefer";
1159                 break;
1160         case MPOL_BIND:
1161                 policy_string = "bind";
1162                 break;
1163         case MPOL_INTERLEAVE:
1164                 policy_string = "interleave";
1165                 break;
1166         default:
1167                 /* MPOL_DEFAULT */
1168                 return;
1169         }
1170
1171         seq_printf(seq, ",mpol=%s", policy_string);
1172
1173         if (policy != MPOL_INTERLEAVE ||
1174             !nodes_equal(policy_nodes, node_states[N_HIGH_MEMORY])) {
1175                 char buffer[64];
1176                 int len;
1177
1178                 len = nodelist_scnprintf(buffer, sizeof(buffer), policy_nodes);
1179                 if (len < sizeof(buffer))
1180                         seq_printf(seq, ":%s", buffer);
1181                 else
1182                         seq_printf(seq, ":?");
1183         }
1184 }
1185 #endif /* CONFIG_TMPFS */
1186
1187 static struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
1188                         struct shmem_inode_info *info, unsigned long idx)
1189 {
1190         struct vm_area_struct pvma;
1191         struct page *page;
1192
1193         /* Create a pseudo vma that just contains the policy */
1194         pvma.vm_start = 0;
1195         pvma.vm_pgoff = idx;
1196         pvma.vm_ops = NULL;
1197         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
1198         page = swapin_readahead(entry, gfp, &pvma, 0);
1199         mpol_free(pvma.vm_policy);
1200         return page;
1201 }
1202
1203 static struct page *shmem_alloc_page(gfp_t gfp,
1204                         struct shmem_inode_info *info, unsigned long idx)
1205 {
1206         struct vm_area_struct pvma;
1207         struct page *page;
1208
1209         /* Create a pseudo vma that just contains the policy */
1210         pvma.vm_start = 0;
1211         pvma.vm_pgoff = idx;
1212         pvma.vm_ops = NULL;
1213         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
1214         page = alloc_page_vma(gfp, &pvma, 0);
1215         mpol_free(pvma.vm_policy);
1216         return page;
1217 }
1218 #else /* !CONFIG_NUMA */
1219 #ifdef CONFIG_TMPFS
1220 static inline int shmem_parse_mpol(char *value, unsigned short *policy,
1221                         unsigned short *mode_flags, nodemask_t *policy_nodes)
1222 {
1223         return 1;
1224 }
1225
1226 static inline void shmem_show_mpol(struct seq_file *seq, unsigned short policy,
1227                         unsigned short flags, const nodemask_t policy_nodes)
1228 {
1229 }
1230 #endif /* CONFIG_TMPFS */
1231
1232 static inline struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
1233                         struct shmem_inode_info *info, unsigned long idx)
1234 {
1235         return swapin_readahead(entry, gfp, NULL, 0);
1236 }
1237
1238 static inline struct page *shmem_alloc_page(gfp_t gfp,
1239                         struct shmem_inode_info *info, unsigned long idx)
1240 {
1241         return alloc_page(gfp);
1242 }
1243 #endif /* CONFIG_NUMA */
1244
1245 /*
1246  * shmem_getpage - either get the page from swap or allocate a new one
1247  *
1248  * If we allocate a new one we do not mark it dirty. That's up to the
1249  * vm. If we swap it in we mark it dirty since we also free the swap
1250  * entry since a page cannot live in both the swap and page cache
1251  */
1252 static int shmem_getpage(struct inode *inode, unsigned long idx,
1253                         struct page **pagep, enum sgp_type sgp, int *type)
1254 {
1255         struct address_space *mapping = inode->i_mapping;
1256         struct shmem_inode_info *info = SHMEM_I(inode);
1257         struct shmem_sb_info *sbinfo;
1258         struct page *filepage = *pagep;
1259         struct page *swappage;
1260         swp_entry_t *entry;
1261         swp_entry_t swap;
1262         gfp_t gfp;
1263         int error;
1264
1265         if (idx >= SHMEM_MAX_INDEX)
1266                 return -EFBIG;
1267
1268         if (type)
1269                 *type = 0;
1270
1271         /*
1272          * Normally, filepage is NULL on entry, and either found
1273          * uptodate immediately, or allocated and zeroed, or read
1274          * in under swappage, which is then assigned to filepage.
1275          * But shmem_readpage (required for splice) passes in a locked
1276          * filepage, which may be found not uptodate by other callers
1277          * too, and may need to be copied from the swappage read in.
1278          */
1279 repeat:
1280         if (!filepage)
1281                 filepage = find_lock_page(mapping, idx);
1282         if (filepage && PageUptodate(filepage))
1283                 goto done;
1284         error = 0;
1285         gfp = mapping_gfp_mask(mapping);
1286         if (!filepage) {
1287                 /*
1288                  * Try to preload while we can wait, to not make a habit of
1289                  * draining atomic reserves; but don't latch on to this cpu.
1290                  */
1291                 error = radix_tree_preload(gfp & ~__GFP_HIGHMEM);
1292                 if (error)
1293                         goto failed;
1294                 radix_tree_preload_end();
1295         }
1296
1297         spin_lock(&info->lock);
1298         shmem_recalc_inode(inode);
1299         entry = shmem_swp_alloc(info, idx, sgp);
1300         if (IS_ERR(entry)) {
1301                 spin_unlock(&info->lock);
1302                 error = PTR_ERR(entry);
1303                 goto failed;
1304         }
1305         swap = *entry;
1306
1307         if (swap.val) {
1308                 /* Look it up and read it in.. */
1309                 swappage = lookup_swap_cache(swap);
1310                 if (!swappage) {
1311                         shmem_swp_unmap(entry);
1312                         /* here we actually do the io */
1313                         if (type && !(*type & VM_FAULT_MAJOR)) {
1314                                 __count_vm_event(PGMAJFAULT);
1315                                 *type |= VM_FAULT_MAJOR;
1316                         }
1317                         spin_unlock(&info->lock);
1318                         swappage = shmem_swapin(swap, gfp, info, idx);
1319                         if (!swappage) {
1320                                 spin_lock(&info->lock);
1321                                 entry = shmem_swp_alloc(info, idx, sgp);
1322                                 if (IS_ERR(entry))
1323                                         error = PTR_ERR(entry);
1324                                 else {
1325                                         if (entry->val == swap.val)
1326                                                 error = -ENOMEM;
1327                                         shmem_swp_unmap(entry);
1328                                 }
1329                                 spin_unlock(&info->lock);
1330                                 if (error)
1331                                         goto failed;
1332                                 goto repeat;
1333                         }
1334                         wait_on_page_locked(swappage);
1335                         page_cache_release(swappage);
1336                         goto repeat;
1337                 }
1338
1339                 /* We have to do this with page locked to prevent races */
1340                 if (TestSetPageLocked(swappage)) {
1341                         shmem_swp_unmap(entry);
1342                         spin_unlock(&info->lock);
1343                         wait_on_page_locked(swappage);
1344                         page_cache_release(swappage);
1345                         goto repeat;
1346                 }
1347                 if (PageWriteback(swappage)) {
1348                         shmem_swp_unmap(entry);
1349                         spin_unlock(&info->lock);
1350                         wait_on_page_writeback(swappage);
1351                         unlock_page(swappage);
1352                         page_cache_release(swappage);
1353                         goto repeat;
1354                 }
1355                 if (!PageUptodate(swappage)) {
1356                         shmem_swp_unmap(entry);
1357                         spin_unlock(&info->lock);
1358                         unlock_page(swappage);
1359                         page_cache_release(swappage);
1360                         error = -EIO;
1361                         goto failed;
1362                 }
1363
1364                 if (filepage) {
1365                         shmem_swp_set(info, entry, 0);
1366                         shmem_swp_unmap(entry);
1367                         delete_from_swap_cache(swappage);
1368                         spin_unlock(&info->lock);
1369                         copy_highpage(filepage, swappage);
1370                         unlock_page(swappage);
1371                         page_cache_release(swappage);
1372                         flush_dcache_page(filepage);
1373                         SetPageUptodate(filepage);
1374                         set_page_dirty(filepage);
1375                         swap_free(swap);
1376                 } else if (!(error = add_to_page_cache(
1377                                 swappage, mapping, idx, GFP_NOWAIT))) {
1378                         info->flags |= SHMEM_PAGEIN;
1379                         shmem_swp_set(info, entry, 0);
1380                         shmem_swp_unmap(entry);
1381                         delete_from_swap_cache(swappage);
1382                         spin_unlock(&info->lock);
1383                         filepage = swappage;
1384                         set_page_dirty(filepage);
1385                         swap_free(swap);
1386                 } else {
1387                         shmem_swp_unmap(entry);
1388                         spin_unlock(&info->lock);
1389                         unlock_page(swappage);
1390                         if (error == -ENOMEM) {
1391                                 /* allow reclaim from this memory cgroup */
1392                                 error = mem_cgroup_cache_charge(swappage,
1393                                         current->mm, gfp & ~__GFP_HIGHMEM);
1394                                 if (error) {
1395                                         page_cache_release(swappage);
1396                                         goto failed;
1397                                 }
1398                                 mem_cgroup_uncharge_page(swappage);
1399                         }
1400                         page_cache_release(swappage);
1401                         goto repeat;
1402                 }
1403         } else if (sgp == SGP_READ && !filepage) {
1404                 shmem_swp_unmap(entry);
1405                 filepage = find_get_page(mapping, idx);
1406                 if (filepage &&
1407                     (!PageUptodate(filepage) || TestSetPageLocked(filepage))) {
1408                         spin_unlock(&info->lock);
1409                         wait_on_page_locked(filepage);
1410                         page_cache_release(filepage);
1411                         filepage = NULL;
1412                         goto repeat;
1413                 }
1414                 spin_unlock(&info->lock);
1415         } else {
1416                 shmem_swp_unmap(entry);
1417                 sbinfo = SHMEM_SB(inode->i_sb);
1418                 if (sbinfo->max_blocks) {
1419                         spin_lock(&sbinfo->stat_lock);
1420                         if (sbinfo->free_blocks == 0 ||
1421                             shmem_acct_block(info->flags)) {
1422                                 spin_unlock(&sbinfo->stat_lock);
1423                                 spin_unlock(&info->lock);
1424                                 error = -ENOSPC;
1425                                 goto failed;
1426                         }
1427                         sbinfo->free_blocks--;
1428                         inode->i_blocks += BLOCKS_PER_PAGE;
1429                         spin_unlock(&sbinfo->stat_lock);
1430                 } else if (shmem_acct_block(info->flags)) {
1431                         spin_unlock(&info->lock);
1432                         error = -ENOSPC;
1433                         goto failed;
1434                 }
1435
1436                 if (!filepage) {
1437                         spin_unlock(&info->lock);
1438                         filepage = shmem_alloc_page(gfp, info, idx);
1439                         if (!filepage) {
1440                                 shmem_unacct_blocks(info->flags, 1);
1441                                 shmem_free_blocks(inode, 1);
1442                                 error = -ENOMEM;
1443                                 goto failed;
1444                         }
1445
1446                         /* Precharge page while we can wait, compensate after */
1447                         error = mem_cgroup_cache_charge(filepage, current->mm,
1448                                                         gfp & ~__GFP_HIGHMEM);
1449                         if (error) {
1450                                 page_cache_release(filepage);
1451                                 shmem_unacct_blocks(info->flags, 1);
1452                                 shmem_free_blocks(inode, 1);
1453                                 filepage = NULL;
1454                                 goto failed;
1455                         }
1456
1457                         spin_lock(&info->lock);
1458                         entry = shmem_swp_alloc(info, idx, sgp);
1459                         if (IS_ERR(entry))
1460                                 error = PTR_ERR(entry);
1461                         else {
1462                                 swap = *entry;
1463                                 shmem_swp_unmap(entry);
1464                         }
1465                         if (error || swap.val || 0 != add_to_page_cache_lru(
1466                                         filepage, mapping, idx, GFP_NOWAIT)) {
1467                                 spin_unlock(&info->lock);
1468                                 mem_cgroup_uncharge_page(filepage);
1469                                 page_cache_release(filepage);
1470                                 shmem_unacct_blocks(info->flags, 1);
1471                                 shmem_free_blocks(inode, 1);
1472                                 filepage = NULL;
1473                                 if (error)
1474                                         goto failed;
1475                                 goto repeat;
1476                         }
1477                         mem_cgroup_uncharge_page(filepage);
1478                         info->flags |= SHMEM_PAGEIN;
1479                 }
1480
1481                 info->alloced++;
1482                 spin_unlock(&info->lock);
1483                 clear_highpage(filepage);
1484                 flush_dcache_page(filepage);
1485                 SetPageUptodate(filepage);
1486                 if (sgp == SGP_DIRTY)
1487                         set_page_dirty(filepage);
1488         }
1489 done:
1490         *pagep = filepage;
1491         return 0;
1492
1493 failed:
1494         if (*pagep != filepage) {
1495                 unlock_page(filepage);
1496                 page_cache_release(filepage);
1497         }
1498         return error;
1499 }
1500
1501 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1502 {
1503         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1504         int error;
1505         int ret;
1506
1507         if (((loff_t)vmf->pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
1508                 return VM_FAULT_SIGBUS;
1509
1510         error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
1511         if (error)
1512                 return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1513
1514         mark_page_accessed(vmf->page);
1515         return ret | VM_FAULT_LOCKED;
1516 }
1517
1518 #ifdef CONFIG_NUMA
1519 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *new)
1520 {
1521         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1522         return mpol_set_shared_policy(&SHMEM_I(i)->policy, vma, new);
1523 }
1524
1525 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
1526                                           unsigned long addr)
1527 {
1528         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1529         unsigned long idx;
1530
1531         idx = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1532         return mpol_shared_policy_lookup(&SHMEM_I(i)->policy, idx);
1533 }
1534 #endif
1535
1536 int shmem_lock(struct file *file, int lock, struct user_struct *user)
1537 {
1538         struct inode *inode = file->f_path.dentry->d_inode;
1539         struct shmem_inode_info *info = SHMEM_I(inode);
1540         int retval = -ENOMEM;
1541
1542         spin_lock(&info->lock);
1543         if (lock && !(info->flags & VM_LOCKED)) {
1544                 if (!user_shm_lock(inode->i_size, user))
1545                         goto out_nomem;
1546                 info->flags |= VM_LOCKED;
1547         }
1548         if (!lock && (info->flags & VM_LOCKED) && user) {
1549                 user_shm_unlock(inode->i_size, user);
1550                 info->flags &= ~VM_LOCKED;
1551         }
1552         retval = 0;
1553 out_nomem:
1554         spin_unlock(&info->lock);
1555         return retval;
1556 }
1557
1558 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1559 {
1560         file_accessed(file);
1561         vma->vm_ops = &shmem_vm_ops;
1562         vma->vm_flags |= VM_CAN_NONLINEAR;
1563         return 0;
1564 }
1565
1566 static struct inode *
1567 shmem_get_inode(struct super_block *sb, int mode, dev_t dev)
1568 {
1569         struct inode *inode;
1570         struct shmem_inode_info *info;
1571         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1572
1573         if (shmem_reserve_inode(sb))
1574                 return NULL;
1575
1576         inode = new_inode(sb);
1577         if (inode) {
1578                 inode->i_mode = mode;
1579                 inode->i_uid = current->fsuid;
1580                 inode->i_gid = current->fsgid;
1581                 inode->i_blocks = 0;
1582                 inode->i_mapping->a_ops = &shmem_aops;
1583                 inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1584                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1585                 inode->i_generation = get_seconds();
1586                 info = SHMEM_I(inode);
1587                 memset(info, 0, (char *)inode - (char *)info);
1588                 spin_lock_init(&info->lock);
1589                 INIT_LIST_HEAD(&info->swaplist);
1590
1591                 switch (mode & S_IFMT) {
1592                 default:
1593                         inode->i_op = &shmem_special_inode_operations;
1594                         init_special_inode(inode, mode, dev);
1595                         break;
1596                 case S_IFREG:
1597                         inode->i_op = &shmem_inode_operations;
1598                         inode->i_fop = &shmem_file_operations;
1599                         mpol_shared_policy_init(&info->policy, sbinfo->policy,
1600                                         sbinfo->flags, &sbinfo->policy_nodes);
1601                         break;
1602                 case S_IFDIR:
1603                         inc_nlink(inode);
1604                         /* Some things misbehave if size == 0 on a directory */
1605                         inode->i_size = 2 * BOGO_DIRENT_SIZE;
1606                         inode->i_op = &shmem_dir_inode_operations;
1607                         inode->i_fop = &simple_dir_operations;
1608                         break;
1609                 case S_IFLNK:
1610                         /*
1611                          * Must not load anything in the rbtree,
1612                          * mpol_free_shared_policy will not be called.
1613                          */
1614                         mpol_shared_policy_init(&info->policy, MPOL_DEFAULT, 0,
1615                                                 NULL);
1616                         break;
1617                 }
1618         } else
1619                 shmem_free_inode(sb);
1620         return inode;
1621 }
1622
1623 #ifdef CONFIG_TMPFS
1624 static const struct inode_operations shmem_symlink_inode_operations;
1625 static const struct inode_operations shmem_symlink_inline_operations;
1626
1627 /*
1628  * Normally tmpfs avoids the use of shmem_readpage and shmem_write_begin;
1629  * but providing them allows a tmpfs file to be used for splice, sendfile, and
1630  * below the loop driver, in the generic fashion that many filesystems support.
1631  */
1632 static int shmem_readpage(struct file *file, struct page *page)
1633 {
1634         struct inode *inode = page->mapping->host;
1635         int error = shmem_getpage(inode, page->index, &page, SGP_CACHE, NULL);
1636         unlock_page(page);
1637         return error;
1638 }
1639
1640 static int
1641 shmem_write_begin(struct file *file, struct address_space *mapping,
1642                         loff_t pos, unsigned len, unsigned flags,
1643                         struct page **pagep, void **fsdata)
1644 {
1645         struct inode *inode = mapping->host;
1646         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1647         *pagep = NULL;
1648         return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
1649 }
1650
1651 static int
1652 shmem_write_end(struct file *file, struct address_space *mapping,
1653                         loff_t pos, unsigned len, unsigned copied,
1654                         struct page *page, void *fsdata)
1655 {
1656         struct inode *inode = mapping->host;
1657
1658         if (pos + copied > inode->i_size)
1659                 i_size_write(inode, pos + copied);
1660
1661         unlock_page(page);
1662         set_page_dirty(page);
1663         page_cache_release(page);
1664
1665         return copied;
1666 }
1667
1668 static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1669 {
1670         struct inode *inode = filp->f_path.dentry->d_inode;
1671         struct address_space *mapping = inode->i_mapping;
1672         unsigned long index, offset;
1673         enum sgp_type sgp = SGP_READ;
1674
1675         /*
1676          * Might this read be for a stacking filesystem?  Then when reading
1677          * holes of a sparse file, we actually need to allocate those pages,
1678          * and even mark them dirty, so it cannot exceed the max_blocks limit.
1679          */
1680         if (segment_eq(get_fs(), KERNEL_DS))
1681                 sgp = SGP_DIRTY;
1682
1683         index = *ppos >> PAGE_CACHE_SHIFT;
1684         offset = *ppos & ~PAGE_CACHE_MASK;
1685
1686         for (;;) {
1687                 struct page *page = NULL;
1688                 unsigned long end_index, nr, ret;
1689                 loff_t i_size = i_size_read(inode);
1690
1691                 end_index = i_size >> PAGE_CACHE_SHIFT;
1692                 if (index > end_index)
1693                         break;
1694                 if (index == end_index) {
1695                         nr = i_size & ~PAGE_CACHE_MASK;
1696                         if (nr <= offset)
1697                                 break;
1698                 }
1699
1700                 desc->error = shmem_getpage(inode, index, &page, sgp, NULL);
1701                 if (desc->error) {
1702                         if (desc->error == -EINVAL)
1703                                 desc->error = 0;
1704                         break;
1705                 }
1706                 if (page)
1707                         unlock_page(page);
1708
1709                 /*
1710                  * We must evaluate after, since reads (unlike writes)
1711                  * are called without i_mutex protection against truncate
1712                  */
1713                 nr = PAGE_CACHE_SIZE;
1714                 i_size = i_size_read(inode);
1715                 end_index = i_size >> PAGE_CACHE_SHIFT;
1716                 if (index == end_index) {
1717                         nr = i_size & ~PAGE_CACHE_MASK;
1718                         if (nr <= offset) {
1719                                 if (page)
1720                                         page_cache_release(page);
1721                                 break;
1722                         }
1723                 }
1724                 nr -= offset;
1725
1726                 if (page) {
1727                         /*
1728                          * If users can be writing to this page using arbitrary
1729                          * virtual addresses, take care about potential aliasing
1730                          * before reading the page on the kernel side.
1731                          */
1732                         if (mapping_writably_mapped(mapping))
1733                                 flush_dcache_page(page);
1734                         /*
1735                          * Mark the page accessed if we read the beginning.
1736                          */
1737                         if (!offset)
1738                                 mark_page_accessed(page);
1739                 } else {
1740                         page = ZERO_PAGE(0);
1741                         page_cache_get(page);
1742                 }
1743
1744                 /*
1745                  * Ok, we have the page, and it's up-to-date, so
1746                  * now we can copy it to user space...
1747                  *
1748                  * The actor routine returns how many bytes were actually used..
1749                  * NOTE! This may not be the same as how much of a user buffer
1750                  * we filled up (we may be padding etc), so we can only update
1751                  * "pos" here (the actor routine has to update the user buffer
1752                  * pointers and the remaining count).
1753                  */
1754                 ret = actor(desc, page, offset, nr);
1755                 offset += ret;
1756                 index += offset >> PAGE_CACHE_SHIFT;
1757                 offset &= ~PAGE_CACHE_MASK;
1758
1759                 page_cache_release(page);
1760                 if (ret != nr || !desc->count)
1761                         break;
1762
1763                 cond_resched();
1764         }
1765
1766         *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1767         file_accessed(filp);
1768 }
1769
1770 static ssize_t shmem_file_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
1771 {
1772         read_descriptor_t desc;
1773
1774         if ((ssize_t) count < 0)
1775                 return -EINVAL;
1776         if (!access_ok(VERIFY_WRITE, buf, count))
1777                 return -EFAULT;
1778         if (!count)
1779                 return 0;
1780
1781         desc.written = 0;
1782         desc.count = count;
1783         desc.arg.buf = buf;
1784         desc.error = 0;
1785
1786         do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1787         if (desc.written)
1788                 return desc.written;
1789         return desc.error;
1790 }
1791
1792 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1793 {
1794         struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1795
1796         buf->f_type = TMPFS_MAGIC;
1797         buf->f_bsize = PAGE_CACHE_SIZE;
1798         buf->f_namelen = NAME_MAX;
1799         spin_lock(&sbinfo->stat_lock);
1800         if (sbinfo->max_blocks) {
1801                 buf->f_blocks = sbinfo->max_blocks;
1802                 buf->f_bavail = buf->f_bfree = sbinfo->free_blocks;
1803         }
1804         if (sbinfo->max_inodes) {
1805                 buf->f_files = sbinfo->max_inodes;
1806                 buf->f_ffree = sbinfo->free_inodes;
1807         }
1808         /* else leave those fields 0 like simple_statfs */
1809         spin_unlock(&sbinfo->stat_lock);
1810         return 0;
1811 }
1812
1813 /*
1814  * File creation. Allocate an inode, and we're done..
1815  */
1816 static int
1817 shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
1818 {
1819         struct inode *inode = shmem_get_inode(dir->i_sb, mode, dev);
1820         int error = -ENOSPC;
1821
1822         if (inode) {
1823                 error = security_inode_init_security(inode, dir, NULL, NULL,
1824                                                      NULL);
1825                 if (error) {
1826                         if (error != -EOPNOTSUPP) {
1827                                 iput(inode);
1828                                 return error;
1829                         }
1830                 }
1831                 error = shmem_acl_init(inode, dir);
1832                 if (error) {
1833                         iput(inode);
1834                         return error;
1835                 }
1836                 if (dir->i_mode & S_ISGID) {
1837                         inode->i_gid = dir->i_gid;
1838                         if (S_ISDIR(mode))
1839                                 inode->i_mode |= S_ISGID;
1840                 }
1841                 dir->i_size += BOGO_DIRENT_SIZE;
1842                 dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1843                 d_instantiate(dentry, inode);
1844                 dget(dentry); /* Extra count - pin the dentry in core */
1845         }
1846         return error;
1847 }
1848
1849 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, int mode)
1850 {
1851         int error;
1852
1853         if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1854                 return error;
1855         inc_nlink(dir);
1856         return 0;
1857 }
1858
1859 static int shmem_create(struct inode *dir, struct dentry *dentry, int mode,
1860                 struct nameidata *nd)
1861 {
1862         return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1863 }
1864
1865 /*
1866  * Link a file..
1867  */
1868 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1869 {
1870         struct inode *inode = old_dentry->d_inode;
1871         int ret;
1872
1873         /*
1874          * No ordinary (disk based) filesystem counts links as inodes;
1875          * but each new link needs a new dentry, pinning lowmem, and
1876          * tmpfs dentries cannot be pruned until they are unlinked.
1877          */
1878         ret = shmem_reserve_inode(inode->i_sb);
1879         if (ret)
1880                 goto out;
1881
1882         dir->i_size += BOGO_DIRENT_SIZE;
1883         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1884         inc_nlink(inode);
1885         atomic_inc(&inode->i_count);    /* New dentry reference */
1886         dget(dentry);           /* Extra pinning count for the created dentry */
1887         d_instantiate(dentry, inode);
1888 out:
1889         return ret;
1890 }
1891
1892 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
1893 {
1894         struct inode *inode = dentry->d_inode;
1895
1896         if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
1897                 shmem_free_inode(inode->i_sb);
1898
1899         dir->i_size -= BOGO_DIRENT_SIZE;
1900         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1901         drop_nlink(inode);
1902         dput(dentry);   /* Undo the count from "create" - this does all the work */
1903         return 0;
1904 }
1905
1906 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
1907 {
1908         if (!simple_empty(dentry))
1909                 return -ENOTEMPTY;
1910
1911         drop_nlink(dentry->d_inode);
1912         drop_nlink(dir);
1913         return shmem_unlink(dir, dentry);
1914 }
1915
1916 /*
1917  * The VFS layer already does all the dentry stuff for rename,
1918  * we just have to decrement the usage count for the target if
1919  * it exists so that the VFS layer correctly free's it when it
1920  * gets overwritten.
1921  */
1922 static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
1923 {
1924         struct inode *inode = old_dentry->d_inode;
1925         int they_are_dirs = S_ISDIR(inode->i_mode);
1926
1927         if (!simple_empty(new_dentry))
1928                 return -ENOTEMPTY;
1929
1930         if (new_dentry->d_inode) {
1931                 (void) shmem_unlink(new_dir, new_dentry);
1932                 if (they_are_dirs)
1933                         drop_nlink(old_dir);
1934         } else if (they_are_dirs) {
1935                 drop_nlink(old_dir);
1936                 inc_nlink(new_dir);
1937         }
1938
1939         old_dir->i_size -= BOGO_DIRENT_SIZE;
1940         new_dir->i_size += BOGO_DIRENT_SIZE;
1941         old_dir->i_ctime = old_dir->i_mtime =
1942         new_dir->i_ctime = new_dir->i_mtime =
1943         inode->i_ctime = CURRENT_TIME;
1944         return 0;
1945 }
1946
1947 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
1948 {
1949         int error;
1950         int len;
1951         struct inode *inode;
1952         struct page *page = NULL;
1953         char *kaddr;
1954         struct shmem_inode_info *info;
1955
1956         len = strlen(symname) + 1;
1957         if (len > PAGE_CACHE_SIZE)
1958                 return -ENAMETOOLONG;
1959
1960         inode = shmem_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
1961         if (!inode)
1962                 return -ENOSPC;
1963
1964         error = security_inode_init_security(inode, dir, NULL, NULL,
1965                                              NULL);
1966         if (error) {
1967                 if (error != -EOPNOTSUPP) {
1968                         iput(inode);
1969                         return error;
1970                 }
1971                 error = 0;
1972         }
1973
1974         info = SHMEM_I(inode);
1975         inode->i_size = len-1;
1976         if (len <= (char *)inode - (char *)info) {
1977                 /* do it inline */
1978                 memcpy(info, symname, len);
1979                 inode->i_op = &shmem_symlink_inline_operations;
1980         } else {
1981                 error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
1982                 if (error) {
1983                         iput(inode);
1984                         return error;
1985                 }
1986                 unlock_page(page);
1987                 inode->i_op = &shmem_symlink_inode_operations;
1988                 kaddr = kmap_atomic(page, KM_USER0);
1989                 memcpy(kaddr, symname, len);
1990                 kunmap_atomic(kaddr, KM_USER0);
1991                 set_page_dirty(page);
1992                 page_cache_release(page);
1993         }
1994         if (dir->i_mode & S_ISGID)
1995                 inode->i_gid = dir->i_gid;
1996         dir->i_size += BOGO_DIRENT_SIZE;
1997         dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1998         d_instantiate(dentry, inode);
1999         dget(dentry);
2000         return 0;
2001 }
2002
2003 static void *shmem_follow_link_inline(struct dentry *dentry, struct nameidata *nd)
2004 {
2005         nd_set_link(nd, (char *)SHMEM_I(dentry->d_inode));
2006         return NULL;
2007 }
2008
2009 static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
2010 {
2011         struct page *page = NULL;
2012         int res = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
2013         nd_set_link(nd, res ? ERR_PTR(res) : kmap(page));
2014         if (page)
2015                 unlock_page(page);
2016         return page;
2017 }
2018
2019 static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
2020 {
2021         if (!IS_ERR(nd_get_link(nd))) {
2022                 struct page *page = cookie;
2023                 kunmap(page);
2024                 mark_page_accessed(page);
2025                 page_cache_release(page);
2026         }
2027 }
2028
2029 static const struct inode_operations shmem_symlink_inline_operations = {
2030         .readlink       = generic_readlink,
2031         .follow_link    = shmem_follow_link_inline,
2032 };
2033
2034 static const struct inode_operations shmem_symlink_inode_operations = {
2035         .truncate       = shmem_truncate,
2036         .readlink       = generic_readlink,
2037         .follow_link    = shmem_follow_link,
2038         .put_link       = shmem_put_link,
2039 };
2040
2041 #ifdef CONFIG_TMPFS_POSIX_ACL
2042 /*
2043  * Superblocks without xattr inode operations will get security.* xattr
2044  * support from the VFS "for free". As soon as we have any other xattrs
2045  * like ACLs, we also need to implement the security.* handlers at
2046  * filesystem level, though.
2047  */
2048
2049 static size_t shmem_xattr_security_list(struct inode *inode, char *list,
2050                                         size_t list_len, const char *name,
2051                                         size_t name_len)
2052 {
2053         return security_inode_listsecurity(inode, list, list_len);
2054 }
2055
2056 static int shmem_xattr_security_get(struct inode *inode, const char *name,
2057                                     void *buffer, size_t size)
2058 {
2059         if (strcmp(name, "") == 0)
2060                 return -EINVAL;
2061         return xattr_getsecurity(inode, name, buffer, size);
2062 }
2063
2064 static int shmem_xattr_security_set(struct inode *inode, const char *name,
2065                                     const void *value, size_t size, int flags)
2066 {
2067         if (strcmp(name, "") == 0)
2068                 return -EINVAL;
2069         return security_inode_setsecurity(inode, name, value, size, flags);
2070 }
2071
2072 static struct xattr_handler shmem_xattr_security_handler = {
2073         .prefix = XATTR_SECURITY_PREFIX,
2074         .list   = shmem_xattr_security_list,
2075         .get    = shmem_xattr_security_get,
2076         .set    = shmem_xattr_security_set,
2077 };
2078
2079 static struct xattr_handler *shmem_xattr_handlers[] = {
2080         &shmem_xattr_acl_access_handler,
2081         &shmem_xattr_acl_default_handler,
2082         &shmem_xattr_security_handler,
2083         NULL
2084 };
2085 #endif
2086
2087 static struct dentry *shmem_get_parent(struct dentry *child)
2088 {
2089         return ERR_PTR(-ESTALE);
2090 }
2091
2092 static int shmem_match(struct inode *ino, void *vfh)
2093 {
2094         __u32 *fh = vfh;
2095         __u64 inum = fh[2];
2096         inum = (inum << 32) | fh[1];
2097         return ino->i_ino == inum && fh[0] == ino->i_generation;
2098 }
2099
2100 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
2101                 struct fid *fid, int fh_len, int fh_type)
2102 {
2103         struct inode *inode;
2104         struct dentry *dentry = NULL;
2105         u64 inum = fid->raw[2];
2106         inum = (inum << 32) | fid->raw[1];
2107
2108         if (fh_len < 3)
2109                 return NULL;
2110
2111         inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
2112                         shmem_match, fid->raw);
2113         if (inode) {
2114                 dentry = d_find_alias(inode);
2115                 iput(inode);
2116         }
2117
2118         return dentry;
2119 }
2120
2121 static int shmem_encode_fh(struct dentry *dentry, __u32 *fh, int *len,
2122                                 int connectable)
2123 {
2124         struct inode *inode = dentry->d_inode;
2125
2126         if (*len < 3)
2127                 return 255;
2128
2129         if (hlist_unhashed(&inode->i_hash)) {
2130                 /* Unfortunately insert_inode_hash is not idempotent,
2131                  * so as we hash inodes here rather than at creation
2132                  * time, we need a lock to ensure we only try
2133                  * to do it once
2134                  */
2135                 static DEFINE_SPINLOCK(lock);
2136                 spin_lock(&lock);
2137                 if (hlist_unhashed(&inode->i_hash))
2138                         __insert_inode_hash(inode,
2139                                             inode->i_ino + inode->i_generation);
2140                 spin_unlock(&lock);
2141         }
2142
2143         fh[0] = inode->i_generation;
2144         fh[1] = inode->i_ino;
2145         fh[2] = ((__u64)inode->i_ino) >> 32;
2146
2147         *len = 3;
2148         return 1;
2149 }
2150
2151 static const struct export_operations shmem_export_ops = {
2152         .get_parent     = shmem_get_parent,
2153         .encode_fh      = shmem_encode_fh,
2154         .fh_to_dentry   = shmem_fh_to_dentry,
2155 };
2156
2157 static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
2158                                bool remount)
2159 {
2160         char *this_char, *value, *rest;
2161
2162         while (options != NULL) {
2163                 this_char = options;
2164                 for (;;) {
2165                         /*
2166                          * NUL-terminate this option: unfortunately,
2167                          * mount options form a comma-separated list,
2168                          * but mpol's nodelist may also contain commas.
2169                          */
2170                         options = strchr(options, ',');
2171                         if (options == NULL)
2172                                 break;
2173                         options++;
2174                         if (!isdigit(*options)) {
2175                                 options[-1] = '\0';
2176                                 break;
2177                         }
2178                 }
2179                 if (!*this_char)
2180                         continue;
2181                 if ((value = strchr(this_char,'=')) != NULL) {
2182                         *value++ = 0;
2183                 } else {
2184                         printk(KERN_ERR
2185                             "tmpfs: No value for mount option '%s'\n",
2186                             this_char);
2187                         return 1;
2188                 }
2189
2190                 if (!strcmp(this_char,"size")) {
2191                         unsigned long long size;
2192                         size = memparse(value,&rest);
2193                         if (*rest == '%') {
2194                                 size <<= PAGE_SHIFT;
2195                                 size *= totalram_pages;
2196                                 do_div(size, 100);
2197                                 rest++;
2198                         }
2199                         if (*rest)
2200                                 goto bad_val;
2201                         sbinfo->max_blocks =
2202                                 DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
2203                 } else if (!strcmp(this_char,"nr_blocks")) {
2204                         sbinfo->max_blocks = memparse(value, &rest);
2205                         if (*rest)
2206                                 goto bad_val;
2207                 } else if (!strcmp(this_char,"nr_inodes")) {
2208                         sbinfo->max_inodes = memparse(value, &rest);
2209                         if (*rest)
2210                                 goto bad_val;
2211                 } else if (!strcmp(this_char,"mode")) {
2212                         if (remount)
2213                                 continue;
2214                         sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
2215                         if (*rest)
2216                                 goto bad_val;
2217                 } else if (!strcmp(this_char,"uid")) {
2218                         if (remount)
2219                                 continue;
2220                         sbinfo->uid = simple_strtoul(value, &rest, 0);
2221                         if (*rest)
2222                                 goto bad_val;
2223                 } else if (!strcmp(this_char,"gid")) {
2224                         if (remount)
2225                                 continue;
2226                         sbinfo->gid = simple_strtoul(value, &rest, 0);
2227                         if (*rest)
2228                                 goto bad_val;
2229                 } else if (!strcmp(this_char,"mpol")) {
2230                         if (shmem_parse_mpol(value, &sbinfo->policy,
2231                                 &sbinfo->flags, &sbinfo->policy_nodes))
2232                                 goto bad_val;
2233                 } else {
2234                         printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2235                                this_char);
2236                         return 1;
2237                 }
2238         }
2239         return 0;
2240
2241 bad_val:
2242         printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2243                value, this_char);
2244         return 1;
2245
2246 }
2247
2248 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2249 {
2250         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2251         struct shmem_sb_info config = *sbinfo;
2252         unsigned long blocks;
2253         unsigned long inodes;
2254         int error = -EINVAL;
2255
2256         if (shmem_parse_options(data, &config, true))
2257                 return error;
2258
2259         spin_lock(&sbinfo->stat_lock);
2260         blocks = sbinfo->max_blocks - sbinfo->free_blocks;
2261         inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2262         if (config.max_blocks < blocks)
2263                 goto out;
2264         if (config.max_inodes < inodes)
2265                 goto out;
2266         /*
2267          * Those tests also disallow limited->unlimited while any are in
2268          * use, so i_blocks will always be zero when max_blocks is zero;
2269          * but we must separately disallow unlimited->limited, because
2270          * in that case we have no record of how much is already in use.
2271          */
2272         if (config.max_blocks && !sbinfo->max_blocks)
2273                 goto out;
2274         if (config.max_inodes && !sbinfo->max_inodes)
2275                 goto out;
2276
2277         error = 0;
2278         sbinfo->max_blocks  = config.max_blocks;
2279         sbinfo->free_blocks = config.max_blocks - blocks;
2280         sbinfo->max_inodes  = config.max_inodes;
2281         sbinfo->free_inodes = config.max_inodes - inodes;
2282         sbinfo->policy      = config.policy;
2283         sbinfo->flags       = config.flags;
2284         sbinfo->policy_nodes = config.policy_nodes;
2285 out:
2286         spin_unlock(&sbinfo->stat_lock);
2287         return error;
2288 }
2289
2290 static int shmem_show_options(struct seq_file *seq, struct vfsmount *vfs)
2291 {
2292         struct shmem_sb_info *sbinfo = SHMEM_SB(vfs->mnt_sb);
2293
2294         if (sbinfo->max_blocks != shmem_default_max_blocks())
2295                 seq_printf(seq, ",size=%luk",
2296                         sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
2297         if (sbinfo->max_inodes != shmem_default_max_inodes())
2298                 seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
2299         if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
2300                 seq_printf(seq, ",mode=%03o", sbinfo->mode);
2301         if (sbinfo->uid != 0)
2302                 seq_printf(seq, ",uid=%u", sbinfo->uid);
2303         if (sbinfo->gid != 0)
2304                 seq_printf(seq, ",gid=%u", sbinfo->gid);
2305         shmem_show_mpol(seq, sbinfo->policy, sbinfo->flags,
2306                         sbinfo->policy_nodes);
2307         return 0;
2308 }
2309 #endif /* CONFIG_TMPFS */
2310
2311 static void shmem_put_super(struct super_block *sb)
2312 {
2313         kfree(sb->s_fs_info);
2314         sb->s_fs_info = NULL;
2315 }
2316
2317 static int shmem_fill_super(struct super_block *sb,
2318                             void *data, int silent)
2319 {
2320         struct inode *inode;
2321         struct dentry *root;
2322         struct shmem_sb_info *sbinfo;
2323         int err = -ENOMEM;
2324
2325         /* Round up to L1_CACHE_BYTES to resist false sharing */
2326         sbinfo = kmalloc(max((int)sizeof(struct shmem_sb_info),
2327                                 L1_CACHE_BYTES), GFP_KERNEL);
2328         if (!sbinfo)
2329                 return -ENOMEM;
2330
2331         sbinfo->max_blocks = 0;
2332         sbinfo->max_inodes = 0;
2333         sbinfo->mode = S_IRWXUGO | S_ISVTX;
2334         sbinfo->uid = current->fsuid;
2335         sbinfo->gid = current->fsgid;
2336         sbinfo->policy = MPOL_DEFAULT;
2337         sbinfo->flags = 0;
2338         sbinfo->policy_nodes = node_states[N_HIGH_MEMORY];
2339         sb->s_fs_info = sbinfo;
2340
2341 #ifdef CONFIG_TMPFS
2342         /*
2343          * Per default we only allow half of the physical ram per
2344          * tmpfs instance, limiting inodes to one per page of lowmem;
2345          * but the internal instance is left unlimited.
2346          */
2347         if (!(sb->s_flags & MS_NOUSER)) {
2348                 sbinfo->max_blocks = shmem_default_max_blocks();
2349                 sbinfo->max_inodes = shmem_default_max_inodes();
2350                 if (shmem_parse_options(data, sbinfo, false)) {
2351                         err = -EINVAL;
2352                         goto failed;
2353                 }
2354         }
2355         sb->s_export_op = &shmem_export_ops;
2356 #else
2357         sb->s_flags |= MS_NOUSER;
2358 #endif
2359
2360         spin_lock_init(&sbinfo->stat_lock);
2361         sbinfo->free_blocks = sbinfo->max_blocks;
2362         sbinfo->free_inodes = sbinfo->max_inodes;
2363
2364         sb->s_maxbytes = SHMEM_MAX_BYTES;
2365         sb->s_blocksize = PAGE_CACHE_SIZE;
2366         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2367         sb->s_magic = TMPFS_MAGIC;
2368         sb->s_op = &shmem_ops;
2369         sb->s_time_gran = 1;
2370 #ifdef CONFIG_TMPFS_POSIX_ACL
2371         sb->s_xattr = shmem_xattr_handlers;
2372         sb->s_flags |= MS_POSIXACL;
2373 #endif
2374
2375         inode = shmem_get_inode(sb, S_IFDIR | sbinfo->mode, 0);
2376         if (!inode)
2377                 goto failed;
2378         inode->i_uid = sbinfo->uid;
2379         inode->i_gid = sbinfo->gid;
2380         root = d_alloc_root(inode);
2381         if (!root)
2382                 goto failed_iput;
2383         sb->s_root = root;
2384         return 0;
2385
2386 failed_iput:
2387         iput(inode);
2388 failed:
2389         shmem_put_super(sb);
2390         return err;
2391 }
2392
2393 static struct kmem_cache *shmem_inode_cachep;
2394
2395 static struct inode *shmem_alloc_inode(struct super_block *sb)
2396 {
2397         struct shmem_inode_info *p;
2398         p = (struct shmem_inode_info *)kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2399         if (!p)
2400                 return NULL;
2401         return &p->vfs_inode;
2402 }
2403
2404 static void shmem_destroy_inode(struct inode *inode)
2405 {
2406         if ((inode->i_mode & S_IFMT) == S_IFREG) {
2407                 /* only struct inode is valid if it's an inline symlink */
2408                 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2409         }
2410         shmem_acl_destroy_inode(inode);
2411         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2412 }
2413
2414 static void init_once(struct kmem_cache *cachep, void *foo)
2415 {
2416         struct shmem_inode_info *p = (struct shmem_inode_info *) foo;
2417
2418         inode_init_once(&p->vfs_inode);
2419 #ifdef CONFIG_TMPFS_POSIX_ACL
2420         p->i_acl = NULL;
2421         p->i_default_acl = NULL;
2422 #endif
2423 }
2424
2425 static int init_inodecache(void)
2426 {
2427         shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2428                                 sizeof(struct shmem_inode_info),
2429                                 0, SLAB_PANIC, init_once);
2430         return 0;
2431 }
2432
2433 static void destroy_inodecache(void)
2434 {
2435         kmem_cache_destroy(shmem_inode_cachep);
2436 }
2437
2438 static const struct address_space_operations shmem_aops = {
2439         .writepage      = shmem_writepage,
2440         .set_page_dirty = __set_page_dirty_no_writeback,
2441 #ifdef CONFIG_TMPFS
2442         .readpage       = shmem_readpage,
2443         .write_begin    = shmem_write_begin,
2444         .write_end      = shmem_write_end,
2445 #endif
2446         .migratepage    = migrate_page,
2447 };
2448
2449 static const struct file_operations shmem_file_operations = {
2450         .mmap           = shmem_mmap,
2451 #ifdef CONFIG_TMPFS
2452         .llseek         = generic_file_llseek,
2453         .read           = shmem_file_read,
2454         .write          = do_sync_write,
2455         .aio_write      = generic_file_aio_write,
2456         .fsync          = simple_sync_file,
2457         .splice_read    = generic_file_splice_read,
2458         .splice_write   = generic_file_splice_write,
2459 #endif
2460 };
2461
2462 static const struct inode_operations shmem_inode_operations = {
2463         .truncate       = shmem_truncate,
2464         .setattr        = shmem_notify_change,
2465         .truncate_range = shmem_truncate_range,
2466 #ifdef CONFIG_TMPFS_POSIX_ACL
2467         .setxattr       = generic_setxattr,
2468         .getxattr       = generic_getxattr,
2469         .listxattr      = generic_listxattr,
2470         .removexattr    = generic_removexattr,
2471         .permission     = shmem_permission,
2472 #endif
2473
2474 };
2475
2476 static const struct inode_operations shmem_dir_inode_operations = {
2477 #ifdef CONFIG_TMPFS
2478         .create         = shmem_create,
2479         .lookup         = simple_lookup,
2480         .link           = shmem_link,
2481         .unlink         = shmem_unlink,
2482         .symlink        = shmem_symlink,
2483         .mkdir          = shmem_mkdir,
2484         .rmdir          = shmem_rmdir,
2485         .mknod          = shmem_mknod,
2486         .rename         = shmem_rename,
2487 #endif
2488 #ifdef CONFIG_TMPFS_POSIX_ACL
2489         .setattr        = shmem_notify_change,
2490         .setxattr       = generic_setxattr,
2491         .getxattr       = generic_getxattr,
2492         .listxattr      = generic_listxattr,
2493         .removexattr    = generic_removexattr,
2494         .permission     = shmem_permission,
2495 #endif
2496 };
2497
2498 static const struct inode_operations shmem_special_inode_operations = {
2499 #ifdef CONFIG_TMPFS_POSIX_ACL
2500         .setattr        = shmem_notify_change,
2501         .setxattr       = generic_setxattr,
2502         .getxattr       = generic_getxattr,
2503         .listxattr      = generic_listxattr,
2504         .removexattr    = generic_removexattr,
2505         .permission     = shmem_permission,
2506 #endif
2507 };
2508
2509 static const struct super_operations shmem_ops = {
2510         .alloc_inode    = shmem_alloc_inode,
2511         .destroy_inode  = shmem_destroy_inode,
2512 #ifdef CONFIG_TMPFS
2513         .statfs         = shmem_statfs,
2514         .remount_fs     = shmem_remount_fs,
2515         .show_options   = shmem_show_options,
2516 #endif
2517         .delete_inode   = shmem_delete_inode,
2518         .drop_inode     = generic_delete_inode,
2519         .put_super      = shmem_put_super,
2520 };
2521
2522 static struct vm_operations_struct shmem_vm_ops = {
2523         .fault          = shmem_fault,
2524 #ifdef CONFIG_NUMA
2525         .set_policy     = shmem_set_policy,
2526         .get_policy     = shmem_get_policy,
2527 #endif
2528 };
2529
2530
2531 static int shmem_get_sb(struct file_system_type *fs_type,
2532         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
2533 {
2534         return get_sb_nodev(fs_type, flags, data, shmem_fill_super, mnt);
2535 }
2536
2537 static struct file_system_type tmpfs_fs_type = {
2538         .owner          = THIS_MODULE,
2539         .name           = "tmpfs",
2540         .get_sb         = shmem_get_sb,
2541         .kill_sb        = kill_litter_super,
2542 };
2543 static struct vfsmount *shm_mnt;
2544
2545 static int __init init_tmpfs(void)
2546 {
2547         int error;
2548
2549         error = bdi_init(&shmem_backing_dev_info);
2550         if (error)
2551                 goto out4;
2552
2553         error = init_inodecache();
2554         if (error)
2555                 goto out3;
2556
2557         error = register_filesystem(&tmpfs_fs_type);
2558         if (error) {
2559                 printk(KERN_ERR "Could not register tmpfs\n");
2560                 goto out2;
2561         }
2562
2563         shm_mnt = vfs_kern_mount(&tmpfs_fs_type, MS_NOUSER,
2564                                 tmpfs_fs_type.name, NULL);
2565         if (IS_ERR(shm_mnt)) {
2566                 error = PTR_ERR(shm_mnt);
2567                 printk(KERN_ERR "Could not kern_mount tmpfs\n");
2568                 goto out1;
2569         }
2570         return 0;
2571
2572 out1:
2573         unregister_filesystem(&tmpfs_fs_type);
2574 out2:
2575         destroy_inodecache();
2576 out3:
2577         bdi_destroy(&shmem_backing_dev_info);
2578 out4:
2579         shm_mnt = ERR_PTR(error);
2580         return error;
2581 }
2582 module_init(init_tmpfs)
2583
2584 /**
2585  * shmem_file_setup - get an unlinked file living in tmpfs
2586  * @name: name for dentry (to be seen in /proc/<pid>/maps
2587  * @size: size to be set for the file
2588  * @flags: vm_flags
2589  */
2590 struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags)
2591 {
2592         int error;
2593         struct file *file;
2594         struct inode *inode;
2595         struct dentry *dentry, *root;
2596         struct qstr this;
2597
2598         if (IS_ERR(shm_mnt))
2599                 return (void *)shm_mnt;
2600
2601         if (size < 0 || size > SHMEM_MAX_BYTES)
2602                 return ERR_PTR(-EINVAL);
2603
2604         if (shmem_acct_size(flags, size))
2605                 return ERR_PTR(-ENOMEM);
2606
2607         error = -ENOMEM;
2608         this.name = name;
2609         this.len = strlen(name);
2610         this.hash = 0; /* will go */
2611         root = shm_mnt->mnt_root;
2612         dentry = d_alloc(root, &this);
2613         if (!dentry)
2614                 goto put_memory;
2615
2616         error = -ENFILE;
2617         file = get_empty_filp();
2618         if (!file)
2619                 goto put_dentry;
2620
2621         error = -ENOSPC;
2622         inode = shmem_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
2623         if (!inode)
2624                 goto close_file;
2625
2626         SHMEM_I(inode)->flags = flags & VM_ACCOUNT;
2627         d_instantiate(dentry, inode);
2628         inode->i_size = size;
2629         inode->i_nlink = 0;     /* It is unlinked */
2630         init_file(file, shm_mnt, dentry, FMODE_WRITE | FMODE_READ,
2631                         &shmem_file_operations);
2632         return file;
2633
2634 close_file:
2635         put_filp(file);
2636 put_dentry:
2637         dput(dentry);
2638 put_memory:
2639         shmem_unacct_size(flags, size);
2640         return ERR_PTR(error);
2641 }
2642
2643 /**
2644  * shmem_zero_setup - setup a shared anonymous mapping
2645  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2646  */
2647 int shmem_zero_setup(struct vm_area_struct *vma)
2648 {
2649         struct file *file;
2650         loff_t size = vma->vm_end - vma->vm_start;
2651
2652         file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2653         if (IS_ERR(file))
2654                 return PTR_ERR(file);
2655
2656         if (vma->vm_file)
2657                 fput(vma->vm_file);
2658         vma->vm_file = file;
2659         vma->vm_ops = &shmem_vm_ops;
2660         return 0;
2661 }