ramfs: replace inode uid,gid,mode initialization with helper function
[linux-2.6.git] / mm / shmem.c
1 /*
2  * Resizable virtual memory filesystem for Linux.
3  *
4  * Copyright (C) 2000 Linus Torvalds.
5  *               2000 Transmeta Corp.
6  *               2000-2001 Christoph Rohland
7  *               2000-2001 SAP AG
8  *               2002 Red Hat Inc.
9  * Copyright (C) 2002-2005 Hugh Dickins.
10  * Copyright (C) 2002-2005 VERITAS Software Corporation.
11  * Copyright (C) 2004 Andi Kleen, SuSE Labs
12  *
13  * Extended attribute support for tmpfs:
14  * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
15  * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
16  *
17  * tiny-shmem:
18  * Copyright (c) 2004, 2008 Matt Mackall <mpm@selenic.com>
19  *
20  * This file is released under the GPL.
21  */
22
23 #include <linux/fs.h>
24 #include <linux/init.h>
25 #include <linux/vfs.h>
26 #include <linux/mount.h>
27 #include <linux/pagemap.h>
28 #include <linux/file.h>
29 #include <linux/mm.h>
30 #include <linux/module.h>
31 #include <linux/swap.h>
32
33 static struct vfsmount *shm_mnt;
34
35 #ifdef CONFIG_SHMEM
36 /*
37  * This virtual memory filesystem is heavily based on the ramfs. It
38  * extends ramfs by the ability to use swap and honor resource limits
39  * which makes it a completely usable filesystem.
40  */
41
42 #include <linux/xattr.h>
43 #include <linux/exportfs.h>
44 #include <linux/posix_acl.h>
45 #include <linux/generic_acl.h>
46 #include <linux/mman.h>
47 #include <linux/string.h>
48 #include <linux/slab.h>
49 #include <linux/backing-dev.h>
50 #include <linux/shmem_fs.h>
51 #include <linux/writeback.h>
52 #include <linux/blkdev.h>
53 #include <linux/security.h>
54 #include <linux/swapops.h>
55 #include <linux/mempolicy.h>
56 #include <linux/namei.h>
57 #include <linux/ctype.h>
58 #include <linux/migrate.h>
59 #include <linux/highmem.h>
60 #include <linux/seq_file.h>
61 #include <linux/magic.h>
62
63 #include <asm/uaccess.h>
64 #include <asm/div64.h>
65 #include <asm/pgtable.h>
66
67 /*
68  * The maximum size of a shmem/tmpfs file is limited by the maximum size of
69  * its triple-indirect swap vector - see illustration at shmem_swp_entry().
70  *
71  * With 4kB page size, maximum file size is just over 2TB on a 32-bit kernel,
72  * but one eighth of that on a 64-bit kernel.  With 8kB page size, maximum
73  * file size is just over 4TB on a 64-bit kernel, but 16TB on a 32-bit kernel,
74  * MAX_LFS_FILESIZE being then more restrictive than swap vector layout.
75  *
76  * We use / and * instead of shifts in the definitions below, so that the swap
77  * vector can be tested with small even values (e.g. 20) for ENTRIES_PER_PAGE.
78  */
79 #define ENTRIES_PER_PAGE (PAGE_CACHE_SIZE/sizeof(unsigned long))
80 #define ENTRIES_PER_PAGEPAGE ((unsigned long long)ENTRIES_PER_PAGE*ENTRIES_PER_PAGE)
81
82 #define SHMSWP_MAX_INDEX (SHMEM_NR_DIRECT + (ENTRIES_PER_PAGEPAGE/2) * (ENTRIES_PER_PAGE+1))
83 #define SHMSWP_MAX_BYTES (SHMSWP_MAX_INDEX << PAGE_CACHE_SHIFT)
84
85 #define SHMEM_MAX_BYTES  min_t(unsigned long long, SHMSWP_MAX_BYTES, MAX_LFS_FILESIZE)
86 #define SHMEM_MAX_INDEX  ((unsigned long)((SHMEM_MAX_BYTES+1) >> PAGE_CACHE_SHIFT))
87
88 #define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
89 #define VM_ACCT(size)    (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
90
91 /* info->flags needs VM_flags to handle pagein/truncate races efficiently */
92 #define SHMEM_PAGEIN     VM_READ
93 #define SHMEM_TRUNCATE   VM_WRITE
94
95 /* Definition to limit shmem_truncate's steps between cond_rescheds */
96 #define LATENCY_LIMIT    64
97
98 /* Pretend that each entry is of this size in directory's i_size */
99 #define BOGO_DIRENT_SIZE 20
100
101 /* Flag allocation requirements to shmem_getpage and shmem_swp_alloc */
102 enum sgp_type {
103         SGP_READ,       /* don't exceed i_size, don't allocate page */
104         SGP_CACHE,      /* don't exceed i_size, may allocate page */
105         SGP_DIRTY,      /* like SGP_CACHE, but set new page dirty */
106         SGP_WRITE,      /* may exceed i_size, may allocate page */
107 };
108
109 #ifdef CONFIG_TMPFS
110 static unsigned long shmem_default_max_blocks(void)
111 {
112         return totalram_pages / 2;
113 }
114
115 static unsigned long shmem_default_max_inodes(void)
116 {
117         return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
118 }
119 #endif
120
121 static int shmem_getpage(struct inode *inode, unsigned long idx,
122                          struct page **pagep, enum sgp_type sgp, int *type);
123
124 static inline struct page *shmem_dir_alloc(gfp_t gfp_mask)
125 {
126         /*
127          * The above definition of ENTRIES_PER_PAGE, and the use of
128          * BLOCKS_PER_PAGE on indirect pages, assume PAGE_CACHE_SIZE:
129          * might be reconsidered if it ever diverges from PAGE_SIZE.
130          *
131          * Mobility flags are masked out as swap vectors cannot move
132          */
133         return alloc_pages((gfp_mask & ~GFP_MOVABLE_MASK) | __GFP_ZERO,
134                                 PAGE_CACHE_SHIFT-PAGE_SHIFT);
135 }
136
137 static inline void shmem_dir_free(struct page *page)
138 {
139         __free_pages(page, PAGE_CACHE_SHIFT-PAGE_SHIFT);
140 }
141
142 static struct page **shmem_dir_map(struct page *page)
143 {
144         return (struct page **)kmap_atomic(page, KM_USER0);
145 }
146
147 static inline void shmem_dir_unmap(struct page **dir)
148 {
149         kunmap_atomic(dir, KM_USER0);
150 }
151
152 static swp_entry_t *shmem_swp_map(struct page *page)
153 {
154         return (swp_entry_t *)kmap_atomic(page, KM_USER1);
155 }
156
157 static inline void shmem_swp_balance_unmap(void)
158 {
159         /*
160          * When passing a pointer to an i_direct entry, to code which
161          * also handles indirect entries and so will shmem_swp_unmap,
162          * we must arrange for the preempt count to remain in balance.
163          * What kmap_atomic of a lowmem page does depends on config
164          * and architecture, so pretend to kmap_atomic some lowmem page.
165          */
166         (void) kmap_atomic(ZERO_PAGE(0), KM_USER1);
167 }
168
169 static inline void shmem_swp_unmap(swp_entry_t *entry)
170 {
171         kunmap_atomic(entry, KM_USER1);
172 }
173
174 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
175 {
176         return sb->s_fs_info;
177 }
178
179 /*
180  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
181  * for shared memory and for shared anonymous (/dev/zero) mappings
182  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
183  * consistent with the pre-accounting of private mappings ...
184  */
185 static inline int shmem_acct_size(unsigned long flags, loff_t size)
186 {
187         return (flags & VM_NORESERVE) ?
188                 0 : security_vm_enough_memory_kern(VM_ACCT(size));
189 }
190
191 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
192 {
193         if (!(flags & VM_NORESERVE))
194                 vm_unacct_memory(VM_ACCT(size));
195 }
196
197 /*
198  * ... whereas tmpfs objects are accounted incrementally as
199  * pages are allocated, in order to allow huge sparse files.
200  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
201  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
202  */
203 static inline int shmem_acct_block(unsigned long flags)
204 {
205         return (flags & VM_NORESERVE) ?
206                 security_vm_enough_memory_kern(VM_ACCT(PAGE_CACHE_SIZE)) : 0;
207 }
208
209 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
210 {
211         if (flags & VM_NORESERVE)
212                 vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
213 }
214
215 static const struct super_operations shmem_ops;
216 static const struct address_space_operations shmem_aops;
217 static const struct file_operations shmem_file_operations;
218 static const struct inode_operations shmem_inode_operations;
219 static const struct inode_operations shmem_dir_inode_operations;
220 static const struct inode_operations shmem_special_inode_operations;
221 static const struct vm_operations_struct shmem_vm_ops;
222
223 static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
224         .ra_pages       = 0,    /* No readahead */
225         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
226         .unplug_io_fn   = default_unplug_io_fn,
227 };
228
229 static LIST_HEAD(shmem_swaplist);
230 static DEFINE_MUTEX(shmem_swaplist_mutex);
231
232 static void shmem_free_blocks(struct inode *inode, long pages)
233 {
234         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
235         if (sbinfo->max_blocks) {
236                 spin_lock(&sbinfo->stat_lock);
237                 sbinfo->free_blocks += pages;
238                 inode->i_blocks -= pages*BLOCKS_PER_PAGE;
239                 spin_unlock(&sbinfo->stat_lock);
240         }
241 }
242
243 static int shmem_reserve_inode(struct super_block *sb)
244 {
245         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
246         if (sbinfo->max_inodes) {
247                 spin_lock(&sbinfo->stat_lock);
248                 if (!sbinfo->free_inodes) {
249                         spin_unlock(&sbinfo->stat_lock);
250                         return -ENOSPC;
251                 }
252                 sbinfo->free_inodes--;
253                 spin_unlock(&sbinfo->stat_lock);
254         }
255         return 0;
256 }
257
258 static void shmem_free_inode(struct super_block *sb)
259 {
260         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
261         if (sbinfo->max_inodes) {
262                 spin_lock(&sbinfo->stat_lock);
263                 sbinfo->free_inodes++;
264                 spin_unlock(&sbinfo->stat_lock);
265         }
266 }
267
268 /**
269  * shmem_recalc_inode - recalculate the size of an inode
270  * @inode: inode to recalc
271  *
272  * We have to calculate the free blocks since the mm can drop
273  * undirtied hole pages behind our back.
274  *
275  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
276  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
277  *
278  * It has to be called with the spinlock held.
279  */
280 static void shmem_recalc_inode(struct inode *inode)
281 {
282         struct shmem_inode_info *info = SHMEM_I(inode);
283         long freed;
284
285         freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
286         if (freed > 0) {
287                 info->alloced -= freed;
288                 shmem_unacct_blocks(info->flags, freed);
289                 shmem_free_blocks(inode, freed);
290         }
291 }
292
293 /**
294  * shmem_swp_entry - find the swap vector position in the info structure
295  * @info:  info structure for the inode
296  * @index: index of the page to find
297  * @page:  optional page to add to the structure. Has to be preset to
298  *         all zeros
299  *
300  * If there is no space allocated yet it will return NULL when
301  * page is NULL, else it will use the page for the needed block,
302  * setting it to NULL on return to indicate that it has been used.
303  *
304  * The swap vector is organized the following way:
305  *
306  * There are SHMEM_NR_DIRECT entries directly stored in the
307  * shmem_inode_info structure. So small files do not need an addional
308  * allocation.
309  *
310  * For pages with index > SHMEM_NR_DIRECT there is the pointer
311  * i_indirect which points to a page which holds in the first half
312  * doubly indirect blocks, in the second half triple indirect blocks:
313  *
314  * For an artificial ENTRIES_PER_PAGE = 4 this would lead to the
315  * following layout (for SHMEM_NR_DIRECT == 16):
316  *
317  * i_indirect -> dir --> 16-19
318  *            |      +-> 20-23
319  *            |
320  *            +-->dir2 --> 24-27
321  *            |        +-> 28-31
322  *            |        +-> 32-35
323  *            |        +-> 36-39
324  *            |
325  *            +-->dir3 --> 40-43
326  *                     +-> 44-47
327  *                     +-> 48-51
328  *                     +-> 52-55
329  */
330 static swp_entry_t *shmem_swp_entry(struct shmem_inode_info *info, unsigned long index, struct page **page)
331 {
332         unsigned long offset;
333         struct page **dir;
334         struct page *subdir;
335
336         if (index < SHMEM_NR_DIRECT) {
337                 shmem_swp_balance_unmap();
338                 return info->i_direct+index;
339         }
340         if (!info->i_indirect) {
341                 if (page) {
342                         info->i_indirect = *page;
343                         *page = NULL;
344                 }
345                 return NULL;                    /* need another page */
346         }
347
348         index -= SHMEM_NR_DIRECT;
349         offset = index % ENTRIES_PER_PAGE;
350         index /= ENTRIES_PER_PAGE;
351         dir = shmem_dir_map(info->i_indirect);
352
353         if (index >= ENTRIES_PER_PAGE/2) {
354                 index -= ENTRIES_PER_PAGE/2;
355                 dir += ENTRIES_PER_PAGE/2 + index/ENTRIES_PER_PAGE;
356                 index %= ENTRIES_PER_PAGE;
357                 subdir = *dir;
358                 if (!subdir) {
359                         if (page) {
360                                 *dir = *page;
361                                 *page = NULL;
362                         }
363                         shmem_dir_unmap(dir);
364                         return NULL;            /* need another page */
365                 }
366                 shmem_dir_unmap(dir);
367                 dir = shmem_dir_map(subdir);
368         }
369
370         dir += index;
371         subdir = *dir;
372         if (!subdir) {
373                 if (!page || !(subdir = *page)) {
374                         shmem_dir_unmap(dir);
375                         return NULL;            /* need a page */
376                 }
377                 *dir = subdir;
378                 *page = NULL;
379         }
380         shmem_dir_unmap(dir);
381         return shmem_swp_map(subdir) + offset;
382 }
383
384 static void shmem_swp_set(struct shmem_inode_info *info, swp_entry_t *entry, unsigned long value)
385 {
386         long incdec = value? 1: -1;
387
388         entry->val = value;
389         info->swapped += incdec;
390         if ((unsigned long)(entry - info->i_direct) >= SHMEM_NR_DIRECT) {
391                 struct page *page = kmap_atomic_to_page(entry);
392                 set_page_private(page, page_private(page) + incdec);
393         }
394 }
395
396 /**
397  * shmem_swp_alloc - get the position of the swap entry for the page.
398  * @info:       info structure for the inode
399  * @index:      index of the page to find
400  * @sgp:        check and recheck i_size? skip allocation?
401  *
402  * If the entry does not exist, allocate it.
403  */
404 static swp_entry_t *shmem_swp_alloc(struct shmem_inode_info *info, unsigned long index, enum sgp_type sgp)
405 {
406         struct inode *inode = &info->vfs_inode;
407         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
408         struct page *page = NULL;
409         swp_entry_t *entry;
410
411         if (sgp != SGP_WRITE &&
412             ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode))
413                 return ERR_PTR(-EINVAL);
414
415         while (!(entry = shmem_swp_entry(info, index, &page))) {
416                 if (sgp == SGP_READ)
417                         return shmem_swp_map(ZERO_PAGE(0));
418                 /*
419                  * Test free_blocks against 1 not 0, since we have 1 data
420                  * page (and perhaps indirect index pages) yet to allocate:
421                  * a waste to allocate index if we cannot allocate data.
422                  */
423                 if (sbinfo->max_blocks) {
424                         spin_lock(&sbinfo->stat_lock);
425                         if (sbinfo->free_blocks <= 1) {
426                                 spin_unlock(&sbinfo->stat_lock);
427                                 return ERR_PTR(-ENOSPC);
428                         }
429                         sbinfo->free_blocks--;
430                         inode->i_blocks += BLOCKS_PER_PAGE;
431                         spin_unlock(&sbinfo->stat_lock);
432                 }
433
434                 spin_unlock(&info->lock);
435                 page = shmem_dir_alloc(mapping_gfp_mask(inode->i_mapping));
436                 if (page)
437                         set_page_private(page, 0);
438                 spin_lock(&info->lock);
439
440                 if (!page) {
441                         shmem_free_blocks(inode, 1);
442                         return ERR_PTR(-ENOMEM);
443                 }
444                 if (sgp != SGP_WRITE &&
445                     ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
446                         entry = ERR_PTR(-EINVAL);
447                         break;
448                 }
449                 if (info->next_index <= index)
450                         info->next_index = index + 1;
451         }
452         if (page) {
453                 /* another task gave its page, or truncated the file */
454                 shmem_free_blocks(inode, 1);
455                 shmem_dir_free(page);
456         }
457         if (info->next_index <= index && !IS_ERR(entry))
458                 info->next_index = index + 1;
459         return entry;
460 }
461
462 /**
463  * shmem_free_swp - free some swap entries in a directory
464  * @dir:        pointer to the directory
465  * @edir:       pointer after last entry of the directory
466  * @punch_lock: pointer to spinlock when needed for the holepunch case
467  */
468 static int shmem_free_swp(swp_entry_t *dir, swp_entry_t *edir,
469                                                 spinlock_t *punch_lock)
470 {
471         spinlock_t *punch_unlock = NULL;
472         swp_entry_t *ptr;
473         int freed = 0;
474
475         for (ptr = dir; ptr < edir; ptr++) {
476                 if (ptr->val) {
477                         if (unlikely(punch_lock)) {
478                                 punch_unlock = punch_lock;
479                                 punch_lock = NULL;
480                                 spin_lock(punch_unlock);
481                                 if (!ptr->val)
482                                         continue;
483                         }
484                         free_swap_and_cache(*ptr);
485                         *ptr = (swp_entry_t){0};
486                         freed++;
487                 }
488         }
489         if (punch_unlock)
490                 spin_unlock(punch_unlock);
491         return freed;
492 }
493
494 static int shmem_map_and_free_swp(struct page *subdir, int offset,
495                 int limit, struct page ***dir, spinlock_t *punch_lock)
496 {
497         swp_entry_t *ptr;
498         int freed = 0;
499
500         ptr = shmem_swp_map(subdir);
501         for (; offset < limit; offset += LATENCY_LIMIT) {
502                 int size = limit - offset;
503                 if (size > LATENCY_LIMIT)
504                         size = LATENCY_LIMIT;
505                 freed += shmem_free_swp(ptr+offset, ptr+offset+size,
506                                                         punch_lock);
507                 if (need_resched()) {
508                         shmem_swp_unmap(ptr);
509                         if (*dir) {
510                                 shmem_dir_unmap(*dir);
511                                 *dir = NULL;
512                         }
513                         cond_resched();
514                         ptr = shmem_swp_map(subdir);
515                 }
516         }
517         shmem_swp_unmap(ptr);
518         return freed;
519 }
520
521 static void shmem_free_pages(struct list_head *next)
522 {
523         struct page *page;
524         int freed = 0;
525
526         do {
527                 page = container_of(next, struct page, lru);
528                 next = next->next;
529                 shmem_dir_free(page);
530                 freed++;
531                 if (freed >= LATENCY_LIMIT) {
532                         cond_resched();
533                         freed = 0;
534                 }
535         } while (next);
536 }
537
538 static void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end)
539 {
540         struct shmem_inode_info *info = SHMEM_I(inode);
541         unsigned long idx;
542         unsigned long size;
543         unsigned long limit;
544         unsigned long stage;
545         unsigned long diroff;
546         struct page **dir;
547         struct page *topdir;
548         struct page *middir;
549         struct page *subdir;
550         swp_entry_t *ptr;
551         LIST_HEAD(pages_to_free);
552         long nr_pages_to_free = 0;
553         long nr_swaps_freed = 0;
554         int offset;
555         int freed;
556         int punch_hole;
557         spinlock_t *needs_lock;
558         spinlock_t *punch_lock;
559         unsigned long upper_limit;
560
561         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
562         idx = (start + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
563         if (idx >= info->next_index)
564                 return;
565
566         spin_lock(&info->lock);
567         info->flags |= SHMEM_TRUNCATE;
568         if (likely(end == (loff_t) -1)) {
569                 limit = info->next_index;
570                 upper_limit = SHMEM_MAX_INDEX;
571                 info->next_index = idx;
572                 needs_lock = NULL;
573                 punch_hole = 0;
574         } else {
575                 if (end + 1 >= inode->i_size) { /* we may free a little more */
576                         limit = (inode->i_size + PAGE_CACHE_SIZE - 1) >>
577                                                         PAGE_CACHE_SHIFT;
578                         upper_limit = SHMEM_MAX_INDEX;
579                 } else {
580                         limit = (end + 1) >> PAGE_CACHE_SHIFT;
581                         upper_limit = limit;
582                 }
583                 needs_lock = &info->lock;
584                 punch_hole = 1;
585         }
586
587         topdir = info->i_indirect;
588         if (topdir && idx <= SHMEM_NR_DIRECT && !punch_hole) {
589                 info->i_indirect = NULL;
590                 nr_pages_to_free++;
591                 list_add(&topdir->lru, &pages_to_free);
592         }
593         spin_unlock(&info->lock);
594
595         if (info->swapped && idx < SHMEM_NR_DIRECT) {
596                 ptr = info->i_direct;
597                 size = limit;
598                 if (size > SHMEM_NR_DIRECT)
599                         size = SHMEM_NR_DIRECT;
600                 nr_swaps_freed = shmem_free_swp(ptr+idx, ptr+size, needs_lock);
601         }
602
603         /*
604          * If there are no indirect blocks or we are punching a hole
605          * below indirect blocks, nothing to be done.
606          */
607         if (!topdir || limit <= SHMEM_NR_DIRECT)
608                 goto done2;
609
610         /*
611          * The truncation case has already dropped info->lock, and we're safe
612          * because i_size and next_index have already been lowered, preventing
613          * access beyond.  But in the punch_hole case, we still need to take
614          * the lock when updating the swap directory, because there might be
615          * racing accesses by shmem_getpage(SGP_CACHE), shmem_unuse_inode or
616          * shmem_writepage.  However, whenever we find we can remove a whole
617          * directory page (not at the misaligned start or end of the range),
618          * we first NULLify its pointer in the level above, and then have no
619          * need to take the lock when updating its contents: needs_lock and
620          * punch_lock (either pointing to info->lock or NULL) manage this.
621          */
622
623         upper_limit -= SHMEM_NR_DIRECT;
624         limit -= SHMEM_NR_DIRECT;
625         idx = (idx > SHMEM_NR_DIRECT)? (idx - SHMEM_NR_DIRECT): 0;
626         offset = idx % ENTRIES_PER_PAGE;
627         idx -= offset;
628
629         dir = shmem_dir_map(topdir);
630         stage = ENTRIES_PER_PAGEPAGE/2;
631         if (idx < ENTRIES_PER_PAGEPAGE/2) {
632                 middir = topdir;
633                 diroff = idx/ENTRIES_PER_PAGE;
634         } else {
635                 dir += ENTRIES_PER_PAGE/2;
636                 dir += (idx - ENTRIES_PER_PAGEPAGE/2)/ENTRIES_PER_PAGEPAGE;
637                 while (stage <= idx)
638                         stage += ENTRIES_PER_PAGEPAGE;
639                 middir = *dir;
640                 if (*dir) {
641                         diroff = ((idx - ENTRIES_PER_PAGEPAGE/2) %
642                                 ENTRIES_PER_PAGEPAGE) / ENTRIES_PER_PAGE;
643                         if (!diroff && !offset && upper_limit >= stage) {
644                                 if (needs_lock) {
645                                         spin_lock(needs_lock);
646                                         *dir = NULL;
647                                         spin_unlock(needs_lock);
648                                         needs_lock = NULL;
649                                 } else
650                                         *dir = NULL;
651                                 nr_pages_to_free++;
652                                 list_add(&middir->lru, &pages_to_free);
653                         }
654                         shmem_dir_unmap(dir);
655                         dir = shmem_dir_map(middir);
656                 } else {
657                         diroff = 0;
658                         offset = 0;
659                         idx = stage;
660                 }
661         }
662
663         for (; idx < limit; idx += ENTRIES_PER_PAGE, diroff++) {
664                 if (unlikely(idx == stage)) {
665                         shmem_dir_unmap(dir);
666                         dir = shmem_dir_map(topdir) +
667                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
668                         while (!*dir) {
669                                 dir++;
670                                 idx += ENTRIES_PER_PAGEPAGE;
671                                 if (idx >= limit)
672                                         goto done1;
673                         }
674                         stage = idx + ENTRIES_PER_PAGEPAGE;
675                         middir = *dir;
676                         if (punch_hole)
677                                 needs_lock = &info->lock;
678                         if (upper_limit >= stage) {
679                                 if (needs_lock) {
680                                         spin_lock(needs_lock);
681                                         *dir = NULL;
682                                         spin_unlock(needs_lock);
683                                         needs_lock = NULL;
684                                 } else
685                                         *dir = NULL;
686                                 nr_pages_to_free++;
687                                 list_add(&middir->lru, &pages_to_free);
688                         }
689                         shmem_dir_unmap(dir);
690                         cond_resched();
691                         dir = shmem_dir_map(middir);
692                         diroff = 0;
693                 }
694                 punch_lock = needs_lock;
695                 subdir = dir[diroff];
696                 if (subdir && !offset && upper_limit-idx >= ENTRIES_PER_PAGE) {
697                         if (needs_lock) {
698                                 spin_lock(needs_lock);
699                                 dir[diroff] = NULL;
700                                 spin_unlock(needs_lock);
701                                 punch_lock = NULL;
702                         } else
703                                 dir[diroff] = NULL;
704                         nr_pages_to_free++;
705                         list_add(&subdir->lru, &pages_to_free);
706                 }
707                 if (subdir && page_private(subdir) /* has swap entries */) {
708                         size = limit - idx;
709                         if (size > ENTRIES_PER_PAGE)
710                                 size = ENTRIES_PER_PAGE;
711                         freed = shmem_map_and_free_swp(subdir,
712                                         offset, size, &dir, punch_lock);
713                         if (!dir)
714                                 dir = shmem_dir_map(middir);
715                         nr_swaps_freed += freed;
716                         if (offset || punch_lock) {
717                                 spin_lock(&info->lock);
718                                 set_page_private(subdir,
719                                         page_private(subdir) - freed);
720                                 spin_unlock(&info->lock);
721                         } else
722                                 BUG_ON(page_private(subdir) != freed);
723                 }
724                 offset = 0;
725         }
726 done1:
727         shmem_dir_unmap(dir);
728 done2:
729         if (inode->i_mapping->nrpages && (info->flags & SHMEM_PAGEIN)) {
730                 /*
731                  * Call truncate_inode_pages again: racing shmem_unuse_inode
732                  * may have swizzled a page in from swap since vmtruncate or
733                  * generic_delete_inode did it, before we lowered next_index.
734                  * Also, though shmem_getpage checks i_size before adding to
735                  * cache, no recheck after: so fix the narrow window there too.
736                  *
737                  * Recalling truncate_inode_pages_range and unmap_mapping_range
738                  * every time for punch_hole (which never got a chance to clear
739                  * SHMEM_PAGEIN at the start of vmtruncate_range) is expensive,
740                  * yet hardly ever necessary: try to optimize them out later.
741                  */
742                 truncate_inode_pages_range(inode->i_mapping, start, end);
743                 if (punch_hole)
744                         unmap_mapping_range(inode->i_mapping, start,
745                                                         end - start, 1);
746         }
747
748         spin_lock(&info->lock);
749         info->flags &= ~SHMEM_TRUNCATE;
750         info->swapped -= nr_swaps_freed;
751         if (nr_pages_to_free)
752                 shmem_free_blocks(inode, nr_pages_to_free);
753         shmem_recalc_inode(inode);
754         spin_unlock(&info->lock);
755
756         /*
757          * Empty swap vector directory pages to be freed?
758          */
759         if (!list_empty(&pages_to_free)) {
760                 pages_to_free.prev->next = NULL;
761                 shmem_free_pages(pages_to_free.next);
762         }
763 }
764
765 static void shmem_truncate(struct inode *inode)
766 {
767         shmem_truncate_range(inode, inode->i_size, (loff_t)-1);
768 }
769
770 static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
771 {
772         struct inode *inode = dentry->d_inode;
773         struct page *page = NULL;
774         int error;
775
776         if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
777                 if (attr->ia_size < inode->i_size) {
778                         /*
779                          * If truncating down to a partial page, then
780                          * if that page is already allocated, hold it
781                          * in memory until the truncation is over, so
782                          * truncate_partial_page cannnot miss it were
783                          * it assigned to swap.
784                          */
785                         if (attr->ia_size & (PAGE_CACHE_SIZE-1)) {
786                                 (void) shmem_getpage(inode,
787                                         attr->ia_size>>PAGE_CACHE_SHIFT,
788                                                 &page, SGP_READ, NULL);
789                                 if (page)
790                                         unlock_page(page);
791                         }
792                         /*
793                          * Reset SHMEM_PAGEIN flag so that shmem_truncate can
794                          * detect if any pages might have been added to cache
795                          * after truncate_inode_pages.  But we needn't bother
796                          * if it's being fully truncated to zero-length: the
797                          * nrpages check is efficient enough in that case.
798                          */
799                         if (attr->ia_size) {
800                                 struct shmem_inode_info *info = SHMEM_I(inode);
801                                 spin_lock(&info->lock);
802                                 info->flags &= ~SHMEM_PAGEIN;
803                                 spin_unlock(&info->lock);
804                         }
805                 }
806         }
807
808         error = inode_change_ok(inode, attr);
809         if (!error)
810                 error = inode_setattr(inode, attr);
811 #ifdef CONFIG_TMPFS_POSIX_ACL
812         if (!error && (attr->ia_valid & ATTR_MODE))
813                 error = generic_acl_chmod(inode);
814 #endif
815         if (page)
816                 page_cache_release(page);
817         return error;
818 }
819
820 static void shmem_delete_inode(struct inode *inode)
821 {
822         struct shmem_inode_info *info = SHMEM_I(inode);
823
824         if (inode->i_op->truncate == shmem_truncate) {
825                 truncate_inode_pages(inode->i_mapping, 0);
826                 shmem_unacct_size(info->flags, inode->i_size);
827                 inode->i_size = 0;
828                 shmem_truncate(inode);
829                 if (!list_empty(&info->swaplist)) {
830                         mutex_lock(&shmem_swaplist_mutex);
831                         list_del_init(&info->swaplist);
832                         mutex_unlock(&shmem_swaplist_mutex);
833                 }
834         }
835         BUG_ON(inode->i_blocks);
836         shmem_free_inode(inode->i_sb);
837         clear_inode(inode);
838 }
839
840 static inline int shmem_find_swp(swp_entry_t entry, swp_entry_t *dir, swp_entry_t *edir)
841 {
842         swp_entry_t *ptr;
843
844         for (ptr = dir; ptr < edir; ptr++) {
845                 if (ptr->val == entry.val)
846                         return ptr - dir;
847         }
848         return -1;
849 }
850
851 static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t entry, struct page *page)
852 {
853         struct inode *inode;
854         unsigned long idx;
855         unsigned long size;
856         unsigned long limit;
857         unsigned long stage;
858         struct page **dir;
859         struct page *subdir;
860         swp_entry_t *ptr;
861         int offset;
862         int error;
863
864         idx = 0;
865         ptr = info->i_direct;
866         spin_lock(&info->lock);
867         if (!info->swapped) {
868                 list_del_init(&info->swaplist);
869                 goto lost2;
870         }
871         limit = info->next_index;
872         size = limit;
873         if (size > SHMEM_NR_DIRECT)
874                 size = SHMEM_NR_DIRECT;
875         offset = shmem_find_swp(entry, ptr, ptr+size);
876         if (offset >= 0)
877                 goto found;
878         if (!info->i_indirect)
879                 goto lost2;
880
881         dir = shmem_dir_map(info->i_indirect);
882         stage = SHMEM_NR_DIRECT + ENTRIES_PER_PAGEPAGE/2;
883
884         for (idx = SHMEM_NR_DIRECT; idx < limit; idx += ENTRIES_PER_PAGE, dir++) {
885                 if (unlikely(idx == stage)) {
886                         shmem_dir_unmap(dir-1);
887                         if (cond_resched_lock(&info->lock)) {
888                                 /* check it has not been truncated */
889                                 if (limit > info->next_index) {
890                                         limit = info->next_index;
891                                         if (idx >= limit)
892                                                 goto lost2;
893                                 }
894                         }
895                         dir = shmem_dir_map(info->i_indirect) +
896                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
897                         while (!*dir) {
898                                 dir++;
899                                 idx += ENTRIES_PER_PAGEPAGE;
900                                 if (idx >= limit)
901                                         goto lost1;
902                         }
903                         stage = idx + ENTRIES_PER_PAGEPAGE;
904                         subdir = *dir;
905                         shmem_dir_unmap(dir);
906                         dir = shmem_dir_map(subdir);
907                 }
908                 subdir = *dir;
909                 if (subdir && page_private(subdir)) {
910                         ptr = shmem_swp_map(subdir);
911                         size = limit - idx;
912                         if (size > ENTRIES_PER_PAGE)
913                                 size = ENTRIES_PER_PAGE;
914                         offset = shmem_find_swp(entry, ptr, ptr+size);
915                         shmem_swp_unmap(ptr);
916                         if (offset >= 0) {
917                                 shmem_dir_unmap(dir);
918                                 goto found;
919                         }
920                 }
921         }
922 lost1:
923         shmem_dir_unmap(dir-1);
924 lost2:
925         spin_unlock(&info->lock);
926         return 0;
927 found:
928         idx += offset;
929         inode = igrab(&info->vfs_inode);
930         spin_unlock(&info->lock);
931
932         /*
933          * Move _head_ to start search for next from here.
934          * But be careful: shmem_delete_inode checks list_empty without taking
935          * mutex, and there's an instant in list_move_tail when info->swaplist
936          * would appear empty, if it were the only one on shmem_swaplist.  We
937          * could avoid doing it if inode NULL; or use this minor optimization.
938          */
939         if (shmem_swaplist.next != &info->swaplist)
940                 list_move_tail(&shmem_swaplist, &info->swaplist);
941         mutex_unlock(&shmem_swaplist_mutex);
942
943         error = 1;
944         if (!inode)
945                 goto out;
946         /*
947          * Charge page using GFP_KERNEL while we can wait.
948          * Charged back to the user(not to caller) when swap account is used.
949          * add_to_page_cache() will be called with GFP_NOWAIT.
950          */
951         error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL);
952         if (error)
953                 goto out;
954         error = radix_tree_preload(GFP_KERNEL);
955         if (error) {
956                 mem_cgroup_uncharge_cache_page(page);
957                 goto out;
958         }
959         error = 1;
960
961         spin_lock(&info->lock);
962         ptr = shmem_swp_entry(info, idx, NULL);
963         if (ptr && ptr->val == entry.val) {
964                 error = add_to_page_cache_locked(page, inode->i_mapping,
965                                                 idx, GFP_NOWAIT);
966                 /* does mem_cgroup_uncharge_cache_page on error */
967         } else  /* we must compensate for our precharge above */
968                 mem_cgroup_uncharge_cache_page(page);
969
970         if (error == -EEXIST) {
971                 struct page *filepage = find_get_page(inode->i_mapping, idx);
972                 error = 1;
973                 if (filepage) {
974                         /*
975                          * There might be a more uptodate page coming down
976                          * from a stacked writepage: forget our swappage if so.
977                          */
978                         if (PageUptodate(filepage))
979                                 error = 0;
980                         page_cache_release(filepage);
981                 }
982         }
983         if (!error) {
984                 delete_from_swap_cache(page);
985                 set_page_dirty(page);
986                 info->flags |= SHMEM_PAGEIN;
987                 shmem_swp_set(info, ptr, 0);
988                 swap_free(entry);
989                 error = 1;      /* not an error, but entry was found */
990         }
991         if (ptr)
992                 shmem_swp_unmap(ptr);
993         spin_unlock(&info->lock);
994         radix_tree_preload_end();
995 out:
996         unlock_page(page);
997         page_cache_release(page);
998         iput(inode);            /* allows for NULL */
999         return error;
1000 }
1001
1002 /*
1003  * shmem_unuse() search for an eventually swapped out shmem page.
1004  */
1005 int shmem_unuse(swp_entry_t entry, struct page *page)
1006 {
1007         struct list_head *p, *next;
1008         struct shmem_inode_info *info;
1009         int found = 0;
1010
1011         mutex_lock(&shmem_swaplist_mutex);
1012         list_for_each_safe(p, next, &shmem_swaplist) {
1013                 info = list_entry(p, struct shmem_inode_info, swaplist);
1014                 found = shmem_unuse_inode(info, entry, page);
1015                 cond_resched();
1016                 if (found)
1017                         goto out;
1018         }
1019         mutex_unlock(&shmem_swaplist_mutex);
1020         /*
1021          * Can some race bring us here?  We've been holding page lock,
1022          * so I think not; but would rather try again later than BUG()
1023          */
1024         unlock_page(page);
1025         page_cache_release(page);
1026 out:
1027         return (found < 0) ? found : 0;
1028 }
1029
1030 /*
1031  * Move the page from the page cache to the swap cache.
1032  */
1033 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
1034 {
1035         struct shmem_inode_info *info;
1036         swp_entry_t *entry, swap;
1037         struct address_space *mapping;
1038         unsigned long index;
1039         struct inode *inode;
1040
1041         BUG_ON(!PageLocked(page));
1042         mapping = page->mapping;
1043         index = page->index;
1044         inode = mapping->host;
1045         info = SHMEM_I(inode);
1046         if (info->flags & VM_LOCKED)
1047                 goto redirty;
1048         if (!total_swap_pages)
1049                 goto redirty;
1050
1051         /*
1052          * shmem_backing_dev_info's capabilities prevent regular writeback or
1053          * sync from ever calling shmem_writepage; but a stacking filesystem
1054          * may use the ->writepage of its underlying filesystem, in which case
1055          * tmpfs should write out to swap only in response to memory pressure,
1056          * and not for the writeback threads or sync.  However, in those cases,
1057          * we do still want to check if there's a redundant swappage to be
1058          * discarded.
1059          */
1060         if (wbc->for_reclaim)
1061                 swap = get_swap_page();
1062         else
1063                 swap.val = 0;
1064
1065         spin_lock(&info->lock);
1066         if (index >= info->next_index) {
1067                 BUG_ON(!(info->flags & SHMEM_TRUNCATE));
1068                 goto unlock;
1069         }
1070         entry = shmem_swp_entry(info, index, NULL);
1071         if (entry->val) {
1072                 /*
1073                  * The more uptodate page coming down from a stacked
1074                  * writepage should replace our old swappage.
1075                  */
1076                 free_swap_and_cache(*entry);
1077                 shmem_swp_set(info, entry, 0);
1078         }
1079         shmem_recalc_inode(inode);
1080
1081         if (swap.val && add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
1082                 remove_from_page_cache(page);
1083                 shmem_swp_set(info, entry, swap.val);
1084                 shmem_swp_unmap(entry);
1085                 if (list_empty(&info->swaplist))
1086                         inode = igrab(inode);
1087                 else
1088                         inode = NULL;
1089                 spin_unlock(&info->lock);
1090                 swap_shmem_alloc(swap);
1091                 BUG_ON(page_mapped(page));
1092                 page_cache_release(page);       /* pagecache ref */
1093                 swap_writepage(page, wbc);
1094                 if (inode) {
1095                         mutex_lock(&shmem_swaplist_mutex);
1096                         /* move instead of add in case we're racing */
1097                         list_move_tail(&info->swaplist, &shmem_swaplist);
1098                         mutex_unlock(&shmem_swaplist_mutex);
1099                         iput(inode);
1100                 }
1101                 return 0;
1102         }
1103
1104         shmem_swp_unmap(entry);
1105 unlock:
1106         spin_unlock(&info->lock);
1107         /*
1108          * add_to_swap_cache() doesn't return -EEXIST, so we can safely
1109          * clear SWAP_HAS_CACHE flag.
1110          */
1111         swapcache_free(swap, NULL);
1112 redirty:
1113         set_page_dirty(page);
1114         if (wbc->for_reclaim)
1115                 return AOP_WRITEPAGE_ACTIVATE;  /* Return with page locked */
1116         unlock_page(page);
1117         return 0;
1118 }
1119
1120 #ifdef CONFIG_NUMA
1121 #ifdef CONFIG_TMPFS
1122 static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1123 {
1124         char buffer[64];
1125
1126         if (!mpol || mpol->mode == MPOL_DEFAULT)
1127                 return;         /* show nothing */
1128
1129         mpol_to_str(buffer, sizeof(buffer), mpol, 1);
1130
1131         seq_printf(seq, ",mpol=%s", buffer);
1132 }
1133
1134 static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1135 {
1136         struct mempolicy *mpol = NULL;
1137         if (sbinfo->mpol) {
1138                 spin_lock(&sbinfo->stat_lock);  /* prevent replace/use races */
1139                 mpol = sbinfo->mpol;
1140                 mpol_get(mpol);
1141                 spin_unlock(&sbinfo->stat_lock);
1142         }
1143         return mpol;
1144 }
1145 #endif /* CONFIG_TMPFS */
1146
1147 static struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
1148                         struct shmem_inode_info *info, unsigned long idx)
1149 {
1150         struct mempolicy mpol, *spol;
1151         struct vm_area_struct pvma;
1152         struct page *page;
1153
1154         spol = mpol_cond_copy(&mpol,
1155                                 mpol_shared_policy_lookup(&info->policy, idx));
1156
1157         /* Create a pseudo vma that just contains the policy */
1158         pvma.vm_start = 0;
1159         pvma.vm_pgoff = idx;
1160         pvma.vm_ops = NULL;
1161         pvma.vm_policy = spol;
1162         page = swapin_readahead(entry, gfp, &pvma, 0);
1163         return page;
1164 }
1165
1166 static struct page *shmem_alloc_page(gfp_t gfp,
1167                         struct shmem_inode_info *info, unsigned long idx)
1168 {
1169         struct vm_area_struct pvma;
1170
1171         /* Create a pseudo vma that just contains the policy */
1172         pvma.vm_start = 0;
1173         pvma.vm_pgoff = idx;
1174         pvma.vm_ops = NULL;
1175         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
1176
1177         /*
1178          * alloc_page_vma() will drop the shared policy reference
1179          */
1180         return alloc_page_vma(gfp, &pvma, 0);
1181 }
1182 #else /* !CONFIG_NUMA */
1183 #ifdef CONFIG_TMPFS
1184 static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *p)
1185 {
1186 }
1187 #endif /* CONFIG_TMPFS */
1188
1189 static inline struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
1190                         struct shmem_inode_info *info, unsigned long idx)
1191 {
1192         return swapin_readahead(entry, gfp, NULL, 0);
1193 }
1194
1195 static inline struct page *shmem_alloc_page(gfp_t gfp,
1196                         struct shmem_inode_info *info, unsigned long idx)
1197 {
1198         return alloc_page(gfp);
1199 }
1200 #endif /* CONFIG_NUMA */
1201
1202 #if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS)
1203 static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1204 {
1205         return NULL;
1206 }
1207 #endif
1208
1209 /*
1210  * shmem_getpage - either get the page from swap or allocate a new one
1211  *
1212  * If we allocate a new one we do not mark it dirty. That's up to the
1213  * vm. If we swap it in we mark it dirty since we also free the swap
1214  * entry since a page cannot live in both the swap and page cache
1215  */
1216 static int shmem_getpage(struct inode *inode, unsigned long idx,
1217                         struct page **pagep, enum sgp_type sgp, int *type)
1218 {
1219         struct address_space *mapping = inode->i_mapping;
1220         struct shmem_inode_info *info = SHMEM_I(inode);
1221         struct shmem_sb_info *sbinfo;
1222         struct page *filepage = *pagep;
1223         struct page *swappage;
1224         swp_entry_t *entry;
1225         swp_entry_t swap;
1226         gfp_t gfp;
1227         int error;
1228
1229         if (idx >= SHMEM_MAX_INDEX)
1230                 return -EFBIG;
1231
1232         if (type)
1233                 *type = 0;
1234
1235         /*
1236          * Normally, filepage is NULL on entry, and either found
1237          * uptodate immediately, or allocated and zeroed, or read
1238          * in under swappage, which is then assigned to filepage.
1239          * But shmem_readpage (required for splice) passes in a locked
1240          * filepage, which may be found not uptodate by other callers
1241          * too, and may need to be copied from the swappage read in.
1242          */
1243 repeat:
1244         if (!filepage)
1245                 filepage = find_lock_page(mapping, idx);
1246         if (filepage && PageUptodate(filepage))
1247                 goto done;
1248         error = 0;
1249         gfp = mapping_gfp_mask(mapping);
1250         if (!filepage) {
1251                 /*
1252                  * Try to preload while we can wait, to not make a habit of
1253                  * draining atomic reserves; but don't latch on to this cpu.
1254                  */
1255                 error = radix_tree_preload(gfp & ~__GFP_HIGHMEM);
1256                 if (error)
1257                         goto failed;
1258                 radix_tree_preload_end();
1259         }
1260
1261         spin_lock(&info->lock);
1262         shmem_recalc_inode(inode);
1263         entry = shmem_swp_alloc(info, idx, sgp);
1264         if (IS_ERR(entry)) {
1265                 spin_unlock(&info->lock);
1266                 error = PTR_ERR(entry);
1267                 goto failed;
1268         }
1269         swap = *entry;
1270
1271         if (swap.val) {
1272                 /* Look it up and read it in.. */
1273                 swappage = lookup_swap_cache(swap);
1274                 if (!swappage) {
1275                         shmem_swp_unmap(entry);
1276                         /* here we actually do the io */
1277                         if (type && !(*type & VM_FAULT_MAJOR)) {
1278                                 __count_vm_event(PGMAJFAULT);
1279                                 *type |= VM_FAULT_MAJOR;
1280                         }
1281                         spin_unlock(&info->lock);
1282                         swappage = shmem_swapin(swap, gfp, info, idx);
1283                         if (!swappage) {
1284                                 spin_lock(&info->lock);
1285                                 entry = shmem_swp_alloc(info, idx, sgp);
1286                                 if (IS_ERR(entry))
1287                                         error = PTR_ERR(entry);
1288                                 else {
1289                                         if (entry->val == swap.val)
1290                                                 error = -ENOMEM;
1291                                         shmem_swp_unmap(entry);
1292                                 }
1293                                 spin_unlock(&info->lock);
1294                                 if (error)
1295                                         goto failed;
1296                                 goto repeat;
1297                         }
1298                         wait_on_page_locked(swappage);
1299                         page_cache_release(swappage);
1300                         goto repeat;
1301                 }
1302
1303                 /* We have to do this with page locked to prevent races */
1304                 if (!trylock_page(swappage)) {
1305                         shmem_swp_unmap(entry);
1306                         spin_unlock(&info->lock);
1307                         wait_on_page_locked(swappage);
1308                         page_cache_release(swappage);
1309                         goto repeat;
1310                 }
1311                 if (PageWriteback(swappage)) {
1312                         shmem_swp_unmap(entry);
1313                         spin_unlock(&info->lock);
1314                         wait_on_page_writeback(swappage);
1315                         unlock_page(swappage);
1316                         page_cache_release(swappage);
1317                         goto repeat;
1318                 }
1319                 if (!PageUptodate(swappage)) {
1320                         shmem_swp_unmap(entry);
1321                         spin_unlock(&info->lock);
1322                         unlock_page(swappage);
1323                         page_cache_release(swappage);
1324                         error = -EIO;
1325                         goto failed;
1326                 }
1327
1328                 if (filepage) {
1329                         shmem_swp_set(info, entry, 0);
1330                         shmem_swp_unmap(entry);
1331                         delete_from_swap_cache(swappage);
1332                         spin_unlock(&info->lock);
1333                         copy_highpage(filepage, swappage);
1334                         unlock_page(swappage);
1335                         page_cache_release(swappage);
1336                         flush_dcache_page(filepage);
1337                         SetPageUptodate(filepage);
1338                         set_page_dirty(filepage);
1339                         swap_free(swap);
1340                 } else if (!(error = add_to_page_cache_locked(swappage, mapping,
1341                                         idx, GFP_NOWAIT))) {
1342                         info->flags |= SHMEM_PAGEIN;
1343                         shmem_swp_set(info, entry, 0);
1344                         shmem_swp_unmap(entry);
1345                         delete_from_swap_cache(swappage);
1346                         spin_unlock(&info->lock);
1347                         filepage = swappage;
1348                         set_page_dirty(filepage);
1349                         swap_free(swap);
1350                 } else {
1351                         shmem_swp_unmap(entry);
1352                         spin_unlock(&info->lock);
1353                         if (error == -ENOMEM) {
1354                                 /*
1355                                  * reclaim from proper memory cgroup and
1356                                  * call memcg's OOM if needed.
1357                                  */
1358                                 error = mem_cgroup_shmem_charge_fallback(
1359                                                                 swappage,
1360                                                                 current->mm,
1361                                                                 gfp);
1362                                 if (error) {
1363                                         unlock_page(swappage);
1364                                         page_cache_release(swappage);
1365                                         goto failed;
1366                                 }
1367                         }
1368                         unlock_page(swappage);
1369                         page_cache_release(swappage);
1370                         goto repeat;
1371                 }
1372         } else if (sgp == SGP_READ && !filepage) {
1373                 shmem_swp_unmap(entry);
1374                 filepage = find_get_page(mapping, idx);
1375                 if (filepage &&
1376                     (!PageUptodate(filepage) || !trylock_page(filepage))) {
1377                         spin_unlock(&info->lock);
1378                         wait_on_page_locked(filepage);
1379                         page_cache_release(filepage);
1380                         filepage = NULL;
1381                         goto repeat;
1382                 }
1383                 spin_unlock(&info->lock);
1384         } else {
1385                 shmem_swp_unmap(entry);
1386                 sbinfo = SHMEM_SB(inode->i_sb);
1387                 if (sbinfo->max_blocks) {
1388                         spin_lock(&sbinfo->stat_lock);
1389                         if (sbinfo->free_blocks == 0 ||
1390                             shmem_acct_block(info->flags)) {
1391                                 spin_unlock(&sbinfo->stat_lock);
1392                                 spin_unlock(&info->lock);
1393                                 error = -ENOSPC;
1394                                 goto failed;
1395                         }
1396                         sbinfo->free_blocks--;
1397                         inode->i_blocks += BLOCKS_PER_PAGE;
1398                         spin_unlock(&sbinfo->stat_lock);
1399                 } else if (shmem_acct_block(info->flags)) {
1400                         spin_unlock(&info->lock);
1401                         error = -ENOSPC;
1402                         goto failed;
1403                 }
1404
1405                 if (!filepage) {
1406                         int ret;
1407
1408                         spin_unlock(&info->lock);
1409                         filepage = shmem_alloc_page(gfp, info, idx);
1410                         if (!filepage) {
1411                                 shmem_unacct_blocks(info->flags, 1);
1412                                 shmem_free_blocks(inode, 1);
1413                                 error = -ENOMEM;
1414                                 goto failed;
1415                         }
1416                         SetPageSwapBacked(filepage);
1417
1418                         /* Precharge page while we can wait, compensate after */
1419                         error = mem_cgroup_cache_charge(filepage, current->mm,
1420                                         GFP_KERNEL);
1421                         if (error) {
1422                                 page_cache_release(filepage);
1423                                 shmem_unacct_blocks(info->flags, 1);
1424                                 shmem_free_blocks(inode, 1);
1425                                 filepage = NULL;
1426                                 goto failed;
1427                         }
1428
1429                         spin_lock(&info->lock);
1430                         entry = shmem_swp_alloc(info, idx, sgp);
1431                         if (IS_ERR(entry))
1432                                 error = PTR_ERR(entry);
1433                         else {
1434                                 swap = *entry;
1435                                 shmem_swp_unmap(entry);
1436                         }
1437                         ret = error || swap.val;
1438                         if (ret)
1439                                 mem_cgroup_uncharge_cache_page(filepage);
1440                         else
1441                                 ret = add_to_page_cache_lru(filepage, mapping,
1442                                                 idx, GFP_NOWAIT);
1443                         /*
1444                          * At add_to_page_cache_lru() failure, uncharge will
1445                          * be done automatically.
1446                          */
1447                         if (ret) {
1448                                 spin_unlock(&info->lock);
1449                                 page_cache_release(filepage);
1450                                 shmem_unacct_blocks(info->flags, 1);
1451                                 shmem_free_blocks(inode, 1);
1452                                 filepage = NULL;
1453                                 if (error)
1454                                         goto failed;
1455                                 goto repeat;
1456                         }
1457                         info->flags |= SHMEM_PAGEIN;
1458                 }
1459
1460                 info->alloced++;
1461                 spin_unlock(&info->lock);
1462                 clear_highpage(filepage);
1463                 flush_dcache_page(filepage);
1464                 SetPageUptodate(filepage);
1465                 if (sgp == SGP_DIRTY)
1466                         set_page_dirty(filepage);
1467         }
1468 done:
1469         *pagep = filepage;
1470         return 0;
1471
1472 failed:
1473         if (*pagep != filepage) {
1474                 unlock_page(filepage);
1475                 page_cache_release(filepage);
1476         }
1477         return error;
1478 }
1479
1480 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1481 {
1482         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1483         int error;
1484         int ret;
1485
1486         if (((loff_t)vmf->pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
1487                 return VM_FAULT_SIGBUS;
1488
1489         error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
1490         if (error)
1491                 return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1492
1493         return ret | VM_FAULT_LOCKED;
1494 }
1495
1496 #ifdef CONFIG_NUMA
1497 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *new)
1498 {
1499         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1500         return mpol_set_shared_policy(&SHMEM_I(i)->policy, vma, new);
1501 }
1502
1503 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
1504                                           unsigned long addr)
1505 {
1506         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1507         unsigned long idx;
1508
1509         idx = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1510         return mpol_shared_policy_lookup(&SHMEM_I(i)->policy, idx);
1511 }
1512 #endif
1513
1514 int shmem_lock(struct file *file, int lock, struct user_struct *user)
1515 {
1516         struct inode *inode = file->f_path.dentry->d_inode;
1517         struct shmem_inode_info *info = SHMEM_I(inode);
1518         int retval = -ENOMEM;
1519
1520         spin_lock(&info->lock);
1521         if (lock && !(info->flags & VM_LOCKED)) {
1522                 if (!user_shm_lock(inode->i_size, user))
1523                         goto out_nomem;
1524                 info->flags |= VM_LOCKED;
1525                 mapping_set_unevictable(file->f_mapping);
1526         }
1527         if (!lock && (info->flags & VM_LOCKED) && user) {
1528                 user_shm_unlock(inode->i_size, user);
1529                 info->flags &= ~VM_LOCKED;
1530                 mapping_clear_unevictable(file->f_mapping);
1531                 scan_mapping_unevictable_pages(file->f_mapping);
1532         }
1533         retval = 0;
1534
1535 out_nomem:
1536         spin_unlock(&info->lock);
1537         return retval;
1538 }
1539
1540 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1541 {
1542         file_accessed(file);
1543         vma->vm_ops = &shmem_vm_ops;
1544         vma->vm_flags |= VM_CAN_NONLINEAR;
1545         return 0;
1546 }
1547
1548 static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
1549                                      int mode, dev_t dev, unsigned long flags)
1550 {
1551         struct inode *inode;
1552         struct shmem_inode_info *info;
1553         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1554
1555         if (shmem_reserve_inode(sb))
1556                 return NULL;
1557
1558         inode = new_inode(sb);
1559         if (inode) {
1560                 inode_init_owner(inode, dir, mode);
1561                 inode->i_blocks = 0;
1562                 inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1563                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1564                 inode->i_generation = get_seconds();
1565                 info = SHMEM_I(inode);
1566                 memset(info, 0, (char *)inode - (char *)info);
1567                 spin_lock_init(&info->lock);
1568                 info->flags = flags & VM_NORESERVE;
1569                 INIT_LIST_HEAD(&info->swaplist);
1570                 cache_no_acl(inode);
1571
1572                 switch (mode & S_IFMT) {
1573                 default:
1574                         inode->i_op = &shmem_special_inode_operations;
1575                         init_special_inode(inode, mode, dev);
1576                         break;
1577                 case S_IFREG:
1578                         inode->i_mapping->a_ops = &shmem_aops;
1579                         inode->i_op = &shmem_inode_operations;
1580                         inode->i_fop = &shmem_file_operations;
1581                         mpol_shared_policy_init(&info->policy,
1582                                                  shmem_get_sbmpol(sbinfo));
1583                         break;
1584                 case S_IFDIR:
1585                         inc_nlink(inode);
1586                         /* Some things misbehave if size == 0 on a directory */
1587                         inode->i_size = 2 * BOGO_DIRENT_SIZE;
1588                         inode->i_op = &shmem_dir_inode_operations;
1589                         inode->i_fop = &simple_dir_operations;
1590                         break;
1591                 case S_IFLNK:
1592                         /*
1593                          * Must not load anything in the rbtree,
1594                          * mpol_free_shared_policy will not be called.
1595                          */
1596                         mpol_shared_policy_init(&info->policy, NULL);
1597                         break;
1598                 }
1599         } else
1600                 shmem_free_inode(sb);
1601         return inode;
1602 }
1603
1604 #ifdef CONFIG_TMPFS
1605 static const struct inode_operations shmem_symlink_inode_operations;
1606 static const struct inode_operations shmem_symlink_inline_operations;
1607
1608 /*
1609  * Normally tmpfs avoids the use of shmem_readpage and shmem_write_begin;
1610  * but providing them allows a tmpfs file to be used for splice, sendfile, and
1611  * below the loop driver, in the generic fashion that many filesystems support.
1612  */
1613 static int shmem_readpage(struct file *file, struct page *page)
1614 {
1615         struct inode *inode = page->mapping->host;
1616         int error = shmem_getpage(inode, page->index, &page, SGP_CACHE, NULL);
1617         unlock_page(page);
1618         return error;
1619 }
1620
1621 static int
1622 shmem_write_begin(struct file *file, struct address_space *mapping,
1623                         loff_t pos, unsigned len, unsigned flags,
1624                         struct page **pagep, void **fsdata)
1625 {
1626         struct inode *inode = mapping->host;
1627         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1628         *pagep = NULL;
1629         return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
1630 }
1631
1632 static int
1633 shmem_write_end(struct file *file, struct address_space *mapping,
1634                         loff_t pos, unsigned len, unsigned copied,
1635                         struct page *page, void *fsdata)
1636 {
1637         struct inode *inode = mapping->host;
1638
1639         if (pos + copied > inode->i_size)
1640                 i_size_write(inode, pos + copied);
1641
1642         set_page_dirty(page);
1643         unlock_page(page);
1644         page_cache_release(page);
1645
1646         return copied;
1647 }
1648
1649 static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1650 {
1651         struct inode *inode = filp->f_path.dentry->d_inode;
1652         struct address_space *mapping = inode->i_mapping;
1653         unsigned long index, offset;
1654         enum sgp_type sgp = SGP_READ;
1655
1656         /*
1657          * Might this read be for a stacking filesystem?  Then when reading
1658          * holes of a sparse file, we actually need to allocate those pages,
1659          * and even mark them dirty, so it cannot exceed the max_blocks limit.
1660          */
1661         if (segment_eq(get_fs(), KERNEL_DS))
1662                 sgp = SGP_DIRTY;
1663
1664         index = *ppos >> PAGE_CACHE_SHIFT;
1665         offset = *ppos & ~PAGE_CACHE_MASK;
1666
1667         for (;;) {
1668                 struct page *page = NULL;
1669                 unsigned long end_index, nr, ret;
1670                 loff_t i_size = i_size_read(inode);
1671
1672                 end_index = i_size >> PAGE_CACHE_SHIFT;
1673                 if (index > end_index)
1674                         break;
1675                 if (index == end_index) {
1676                         nr = i_size & ~PAGE_CACHE_MASK;
1677                         if (nr <= offset)
1678                                 break;
1679                 }
1680
1681                 desc->error = shmem_getpage(inode, index, &page, sgp, NULL);
1682                 if (desc->error) {
1683                         if (desc->error == -EINVAL)
1684                                 desc->error = 0;
1685                         break;
1686                 }
1687                 if (page)
1688                         unlock_page(page);
1689
1690                 /*
1691                  * We must evaluate after, since reads (unlike writes)
1692                  * are called without i_mutex protection against truncate
1693                  */
1694                 nr = PAGE_CACHE_SIZE;
1695                 i_size = i_size_read(inode);
1696                 end_index = i_size >> PAGE_CACHE_SHIFT;
1697                 if (index == end_index) {
1698                         nr = i_size & ~PAGE_CACHE_MASK;
1699                         if (nr <= offset) {
1700                                 if (page)
1701                                         page_cache_release(page);
1702                                 break;
1703                         }
1704                 }
1705                 nr -= offset;
1706
1707                 if (page) {
1708                         /*
1709                          * If users can be writing to this page using arbitrary
1710                          * virtual addresses, take care about potential aliasing
1711                          * before reading the page on the kernel side.
1712                          */
1713                         if (mapping_writably_mapped(mapping))
1714                                 flush_dcache_page(page);
1715                         /*
1716                          * Mark the page accessed if we read the beginning.
1717                          */
1718                         if (!offset)
1719                                 mark_page_accessed(page);
1720                 } else {
1721                         page = ZERO_PAGE(0);
1722                         page_cache_get(page);
1723                 }
1724
1725                 /*
1726                  * Ok, we have the page, and it's up-to-date, so
1727                  * now we can copy it to user space...
1728                  *
1729                  * The actor routine returns how many bytes were actually used..
1730                  * NOTE! This may not be the same as how much of a user buffer
1731                  * we filled up (we may be padding etc), so we can only update
1732                  * "pos" here (the actor routine has to update the user buffer
1733                  * pointers and the remaining count).
1734                  */
1735                 ret = actor(desc, page, offset, nr);
1736                 offset += ret;
1737                 index += offset >> PAGE_CACHE_SHIFT;
1738                 offset &= ~PAGE_CACHE_MASK;
1739
1740                 page_cache_release(page);
1741                 if (ret != nr || !desc->count)
1742                         break;
1743
1744                 cond_resched();
1745         }
1746
1747         *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1748         file_accessed(filp);
1749 }
1750
1751 static ssize_t shmem_file_aio_read(struct kiocb *iocb,
1752                 const struct iovec *iov, unsigned long nr_segs, loff_t pos)
1753 {
1754         struct file *filp = iocb->ki_filp;
1755         ssize_t retval;
1756         unsigned long seg;
1757         size_t count;
1758         loff_t *ppos = &iocb->ki_pos;
1759
1760         retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1761         if (retval)
1762                 return retval;
1763
1764         for (seg = 0; seg < nr_segs; seg++) {
1765                 read_descriptor_t desc;
1766
1767                 desc.written = 0;
1768                 desc.arg.buf = iov[seg].iov_base;
1769                 desc.count = iov[seg].iov_len;
1770                 if (desc.count == 0)
1771                         continue;
1772                 desc.error = 0;
1773                 do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1774                 retval += desc.written;
1775                 if (desc.error) {
1776                         retval = retval ?: desc.error;
1777                         break;
1778                 }
1779                 if (desc.count > 0)
1780                         break;
1781         }
1782         return retval;
1783 }
1784
1785 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1786 {
1787         struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1788
1789         buf->f_type = TMPFS_MAGIC;
1790         buf->f_bsize = PAGE_CACHE_SIZE;
1791         buf->f_namelen = NAME_MAX;
1792         spin_lock(&sbinfo->stat_lock);
1793         if (sbinfo->max_blocks) {
1794                 buf->f_blocks = sbinfo->max_blocks;
1795                 buf->f_bavail = buf->f_bfree = sbinfo->free_blocks;
1796         }
1797         if (sbinfo->max_inodes) {
1798                 buf->f_files = sbinfo->max_inodes;
1799                 buf->f_ffree = sbinfo->free_inodes;
1800         }
1801         /* else leave those fields 0 like simple_statfs */
1802         spin_unlock(&sbinfo->stat_lock);
1803         return 0;
1804 }
1805
1806 /*
1807  * File creation. Allocate an inode, and we're done..
1808  */
1809 static int
1810 shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
1811 {
1812         struct inode *inode;
1813         int error = -ENOSPC;
1814
1815         inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
1816         if (inode) {
1817                 error = security_inode_init_security(inode, dir, NULL, NULL,
1818                                                      NULL);
1819                 if (error) {
1820                         if (error != -EOPNOTSUPP) {
1821                                 iput(inode);
1822                                 return error;
1823                         }
1824                 }
1825 #ifdef CONFIG_TMPFS_POSIX_ACL
1826                 error = generic_acl_init(inode, dir);
1827                 if (error) {
1828                         iput(inode);
1829                         return error;
1830                 }
1831 #else
1832                 error = 0;
1833 #endif
1834                 dir->i_size += BOGO_DIRENT_SIZE;
1835                 dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1836                 d_instantiate(dentry, inode);
1837                 dget(dentry); /* Extra count - pin the dentry in core */
1838         }
1839         return error;
1840 }
1841
1842 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, int mode)
1843 {
1844         int error;
1845
1846         if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1847                 return error;
1848         inc_nlink(dir);
1849         return 0;
1850 }
1851
1852 static int shmem_create(struct inode *dir, struct dentry *dentry, int mode,
1853                 struct nameidata *nd)
1854 {
1855         return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1856 }
1857
1858 /*
1859  * Link a file..
1860  */
1861 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1862 {
1863         struct inode *inode = old_dentry->d_inode;
1864         int ret;
1865
1866         /*
1867          * No ordinary (disk based) filesystem counts links as inodes;
1868          * but each new link needs a new dentry, pinning lowmem, and
1869          * tmpfs dentries cannot be pruned until they are unlinked.
1870          */
1871         ret = shmem_reserve_inode(inode->i_sb);
1872         if (ret)
1873                 goto out;
1874
1875         dir->i_size += BOGO_DIRENT_SIZE;
1876         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1877         inc_nlink(inode);
1878         atomic_inc(&inode->i_count);    /* New dentry reference */
1879         dget(dentry);           /* Extra pinning count for the created dentry */
1880         d_instantiate(dentry, inode);
1881 out:
1882         return ret;
1883 }
1884
1885 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
1886 {
1887         struct inode *inode = dentry->d_inode;
1888
1889         if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
1890                 shmem_free_inode(inode->i_sb);
1891
1892         dir->i_size -= BOGO_DIRENT_SIZE;
1893         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1894         drop_nlink(inode);
1895         dput(dentry);   /* Undo the count from "create" - this does all the work */
1896         return 0;
1897 }
1898
1899 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
1900 {
1901         if (!simple_empty(dentry))
1902                 return -ENOTEMPTY;
1903
1904         drop_nlink(dentry->d_inode);
1905         drop_nlink(dir);
1906         return shmem_unlink(dir, dentry);
1907 }
1908
1909 /*
1910  * The VFS layer already does all the dentry stuff for rename,
1911  * we just have to decrement the usage count for the target if
1912  * it exists so that the VFS layer correctly free's it when it
1913  * gets overwritten.
1914  */
1915 static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
1916 {
1917         struct inode *inode = old_dentry->d_inode;
1918         int they_are_dirs = S_ISDIR(inode->i_mode);
1919
1920         if (!simple_empty(new_dentry))
1921                 return -ENOTEMPTY;
1922
1923         if (new_dentry->d_inode) {
1924                 (void) shmem_unlink(new_dir, new_dentry);
1925                 if (they_are_dirs)
1926                         drop_nlink(old_dir);
1927         } else if (they_are_dirs) {
1928                 drop_nlink(old_dir);
1929                 inc_nlink(new_dir);
1930         }
1931
1932         old_dir->i_size -= BOGO_DIRENT_SIZE;
1933         new_dir->i_size += BOGO_DIRENT_SIZE;
1934         old_dir->i_ctime = old_dir->i_mtime =
1935         new_dir->i_ctime = new_dir->i_mtime =
1936         inode->i_ctime = CURRENT_TIME;
1937         return 0;
1938 }
1939
1940 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
1941 {
1942         int error;
1943         int len;
1944         struct inode *inode;
1945         struct page *page = NULL;
1946         char *kaddr;
1947         struct shmem_inode_info *info;
1948
1949         len = strlen(symname) + 1;
1950         if (len > PAGE_CACHE_SIZE)
1951                 return -ENAMETOOLONG;
1952
1953         inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE);
1954         if (!inode)
1955                 return -ENOSPC;
1956
1957         error = security_inode_init_security(inode, dir, NULL, NULL,
1958                                              NULL);
1959         if (error) {
1960                 if (error != -EOPNOTSUPP) {
1961                         iput(inode);
1962                         return error;
1963                 }
1964                 error = 0;
1965         }
1966
1967         info = SHMEM_I(inode);
1968         inode->i_size = len-1;
1969         if (len <= (char *)inode - (char *)info) {
1970                 /* do it inline */
1971                 memcpy(info, symname, len);
1972                 inode->i_op = &shmem_symlink_inline_operations;
1973         } else {
1974                 error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
1975                 if (error) {
1976                         iput(inode);
1977                         return error;
1978                 }
1979                 inode->i_mapping->a_ops = &shmem_aops;
1980                 inode->i_op = &shmem_symlink_inode_operations;
1981                 kaddr = kmap_atomic(page, KM_USER0);
1982                 memcpy(kaddr, symname, len);
1983                 kunmap_atomic(kaddr, KM_USER0);
1984                 set_page_dirty(page);
1985                 unlock_page(page);
1986                 page_cache_release(page);
1987         }
1988         dir->i_size += BOGO_DIRENT_SIZE;
1989         dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1990         d_instantiate(dentry, inode);
1991         dget(dentry);
1992         return 0;
1993 }
1994
1995 static void *shmem_follow_link_inline(struct dentry *dentry, struct nameidata *nd)
1996 {
1997         nd_set_link(nd, (char *)SHMEM_I(dentry->d_inode));
1998         return NULL;
1999 }
2000
2001 static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
2002 {
2003         struct page *page = NULL;
2004         int res = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
2005         nd_set_link(nd, res ? ERR_PTR(res) : kmap(page));
2006         if (page)
2007                 unlock_page(page);
2008         return page;
2009 }
2010
2011 static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
2012 {
2013         if (!IS_ERR(nd_get_link(nd))) {
2014                 struct page *page = cookie;
2015                 kunmap(page);
2016                 mark_page_accessed(page);
2017                 page_cache_release(page);
2018         }
2019 }
2020
2021 static const struct inode_operations shmem_symlink_inline_operations = {
2022         .readlink       = generic_readlink,
2023         .follow_link    = shmem_follow_link_inline,
2024 };
2025
2026 static const struct inode_operations shmem_symlink_inode_operations = {
2027         .truncate       = shmem_truncate,
2028         .readlink       = generic_readlink,
2029         .follow_link    = shmem_follow_link,
2030         .put_link       = shmem_put_link,
2031 };
2032
2033 #ifdef CONFIG_TMPFS_POSIX_ACL
2034 /*
2035  * Superblocks without xattr inode operations will get security.* xattr
2036  * support from the VFS "for free". As soon as we have any other xattrs
2037  * like ACLs, we also need to implement the security.* handlers at
2038  * filesystem level, though.
2039  */
2040
2041 static size_t shmem_xattr_security_list(struct dentry *dentry, char *list,
2042                                         size_t list_len, const char *name,
2043                                         size_t name_len, int handler_flags)
2044 {
2045         return security_inode_listsecurity(dentry->d_inode, list, list_len);
2046 }
2047
2048 static int shmem_xattr_security_get(struct dentry *dentry, const char *name,
2049                 void *buffer, size_t size, int handler_flags)
2050 {
2051         if (strcmp(name, "") == 0)
2052                 return -EINVAL;
2053         return xattr_getsecurity(dentry->d_inode, name, buffer, size);
2054 }
2055
2056 static int shmem_xattr_security_set(struct dentry *dentry, const char *name,
2057                 const void *value, size_t size, int flags, int handler_flags)
2058 {
2059         if (strcmp(name, "") == 0)
2060                 return -EINVAL;
2061         return security_inode_setsecurity(dentry->d_inode, name, value,
2062                                           size, flags);
2063 }
2064
2065 static const struct xattr_handler shmem_xattr_security_handler = {
2066         .prefix = XATTR_SECURITY_PREFIX,
2067         .list   = shmem_xattr_security_list,
2068         .get    = shmem_xattr_security_get,
2069         .set    = shmem_xattr_security_set,
2070 };
2071
2072 static const struct xattr_handler *shmem_xattr_handlers[] = {
2073         &generic_acl_access_handler,
2074         &generic_acl_default_handler,
2075         &shmem_xattr_security_handler,
2076         NULL
2077 };
2078 #endif
2079
2080 static struct dentry *shmem_get_parent(struct dentry *child)
2081 {
2082         return ERR_PTR(-ESTALE);
2083 }
2084
2085 static int shmem_match(struct inode *ino, void *vfh)
2086 {
2087         __u32 *fh = vfh;
2088         __u64 inum = fh[2];
2089         inum = (inum << 32) | fh[1];
2090         return ino->i_ino == inum && fh[0] == ino->i_generation;
2091 }
2092
2093 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
2094                 struct fid *fid, int fh_len, int fh_type)
2095 {
2096         struct inode *inode;
2097         struct dentry *dentry = NULL;
2098         u64 inum = fid->raw[2];
2099         inum = (inum << 32) | fid->raw[1];
2100
2101         if (fh_len < 3)
2102                 return NULL;
2103
2104         inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
2105                         shmem_match, fid->raw);
2106         if (inode) {
2107                 dentry = d_find_alias(inode);
2108                 iput(inode);
2109         }
2110
2111         return dentry;
2112 }
2113
2114 static int shmem_encode_fh(struct dentry *dentry, __u32 *fh, int *len,
2115                                 int connectable)
2116 {
2117         struct inode *inode = dentry->d_inode;
2118
2119         if (*len < 3)
2120                 return 255;
2121
2122         if (hlist_unhashed(&inode->i_hash)) {
2123                 /* Unfortunately insert_inode_hash is not idempotent,
2124                  * so as we hash inodes here rather than at creation
2125                  * time, we need a lock to ensure we only try
2126                  * to do it once
2127                  */
2128                 static DEFINE_SPINLOCK(lock);
2129                 spin_lock(&lock);
2130                 if (hlist_unhashed(&inode->i_hash))
2131                         __insert_inode_hash(inode,
2132                                             inode->i_ino + inode->i_generation);
2133                 spin_unlock(&lock);
2134         }
2135
2136         fh[0] = inode->i_generation;
2137         fh[1] = inode->i_ino;
2138         fh[2] = ((__u64)inode->i_ino) >> 32;
2139
2140         *len = 3;
2141         return 1;
2142 }
2143
2144 static const struct export_operations shmem_export_ops = {
2145         .get_parent     = shmem_get_parent,
2146         .encode_fh      = shmem_encode_fh,
2147         .fh_to_dentry   = shmem_fh_to_dentry,
2148 };
2149
2150 static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
2151                                bool remount)
2152 {
2153         char *this_char, *value, *rest;
2154
2155         while (options != NULL) {
2156                 this_char = options;
2157                 for (;;) {
2158                         /*
2159                          * NUL-terminate this option: unfortunately,
2160                          * mount options form a comma-separated list,
2161                          * but mpol's nodelist may also contain commas.
2162                          */
2163                         options = strchr(options, ',');
2164                         if (options == NULL)
2165                                 break;
2166                         options++;
2167                         if (!isdigit(*options)) {
2168                                 options[-1] = '\0';
2169                                 break;
2170                         }
2171                 }
2172                 if (!*this_char)
2173                         continue;
2174                 if ((value = strchr(this_char,'=')) != NULL) {
2175                         *value++ = 0;
2176                 } else {
2177                         printk(KERN_ERR
2178                             "tmpfs: No value for mount option '%s'\n",
2179                             this_char);
2180                         return 1;
2181                 }
2182
2183                 if (!strcmp(this_char,"size")) {
2184                         unsigned long long size;
2185                         size = memparse(value,&rest);
2186                         if (*rest == '%') {
2187                                 size <<= PAGE_SHIFT;
2188                                 size *= totalram_pages;
2189                                 do_div(size, 100);
2190                                 rest++;
2191                         }
2192                         if (*rest)
2193                                 goto bad_val;
2194                         sbinfo->max_blocks =
2195                                 DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
2196                 } else if (!strcmp(this_char,"nr_blocks")) {
2197                         sbinfo->max_blocks = memparse(value, &rest);
2198                         if (*rest)
2199                                 goto bad_val;
2200                 } else if (!strcmp(this_char,"nr_inodes")) {
2201                         sbinfo->max_inodes = memparse(value, &rest);
2202                         if (*rest)
2203                                 goto bad_val;
2204                 } else if (!strcmp(this_char,"mode")) {
2205                         if (remount)
2206                                 continue;
2207                         sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
2208                         if (*rest)
2209                                 goto bad_val;
2210                 } else if (!strcmp(this_char,"uid")) {
2211                         if (remount)
2212                                 continue;
2213                         sbinfo->uid = simple_strtoul(value, &rest, 0);
2214                         if (*rest)
2215                                 goto bad_val;
2216                 } else if (!strcmp(this_char,"gid")) {
2217                         if (remount)
2218                                 continue;
2219                         sbinfo->gid = simple_strtoul(value, &rest, 0);
2220                         if (*rest)
2221                                 goto bad_val;
2222                 } else if (!strcmp(this_char,"mpol")) {
2223                         if (mpol_parse_str(value, &sbinfo->mpol, 1))
2224                                 goto bad_val;
2225                 } else {
2226                         printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2227                                this_char);
2228                         return 1;
2229                 }
2230         }
2231         return 0;
2232
2233 bad_val:
2234         printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2235                value, this_char);
2236         return 1;
2237
2238 }
2239
2240 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2241 {
2242         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2243         struct shmem_sb_info config = *sbinfo;
2244         unsigned long blocks;
2245         unsigned long inodes;
2246         int error = -EINVAL;
2247
2248         if (shmem_parse_options(data, &config, true))
2249                 return error;
2250
2251         spin_lock(&sbinfo->stat_lock);
2252         blocks = sbinfo->max_blocks - sbinfo->free_blocks;
2253         inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2254         if (config.max_blocks < blocks)
2255                 goto out;
2256         if (config.max_inodes < inodes)
2257                 goto out;
2258         /*
2259          * Those tests also disallow limited->unlimited while any are in
2260          * use, so i_blocks will always be zero when max_blocks is zero;
2261          * but we must separately disallow unlimited->limited, because
2262          * in that case we have no record of how much is already in use.
2263          */
2264         if (config.max_blocks && !sbinfo->max_blocks)
2265                 goto out;
2266         if (config.max_inodes && !sbinfo->max_inodes)
2267                 goto out;
2268
2269         error = 0;
2270         sbinfo->max_blocks  = config.max_blocks;
2271         sbinfo->free_blocks = config.max_blocks - blocks;
2272         sbinfo->max_inodes  = config.max_inodes;
2273         sbinfo->free_inodes = config.max_inodes - inodes;
2274
2275         mpol_put(sbinfo->mpol);
2276         sbinfo->mpol        = config.mpol;      /* transfers initial ref */
2277 out:
2278         spin_unlock(&sbinfo->stat_lock);
2279         return error;
2280 }
2281
2282 static int shmem_show_options(struct seq_file *seq, struct vfsmount *vfs)
2283 {
2284         struct shmem_sb_info *sbinfo = SHMEM_SB(vfs->mnt_sb);
2285
2286         if (sbinfo->max_blocks != shmem_default_max_blocks())
2287                 seq_printf(seq, ",size=%luk",
2288                         sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
2289         if (sbinfo->max_inodes != shmem_default_max_inodes())
2290                 seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
2291         if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
2292                 seq_printf(seq, ",mode=%03o", sbinfo->mode);
2293         if (sbinfo->uid != 0)
2294                 seq_printf(seq, ",uid=%u", sbinfo->uid);
2295         if (sbinfo->gid != 0)
2296                 seq_printf(seq, ",gid=%u", sbinfo->gid);
2297         shmem_show_mpol(seq, sbinfo->mpol);
2298         return 0;
2299 }
2300 #endif /* CONFIG_TMPFS */
2301
2302 static void shmem_put_super(struct super_block *sb)
2303 {
2304         kfree(sb->s_fs_info);
2305         sb->s_fs_info = NULL;
2306 }
2307
2308 int shmem_fill_super(struct super_block *sb, void *data, int silent)
2309 {
2310         struct inode *inode;
2311         struct dentry *root;
2312         struct shmem_sb_info *sbinfo;
2313         int err = -ENOMEM;
2314
2315         /* Round up to L1_CACHE_BYTES to resist false sharing */
2316         sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
2317                                 L1_CACHE_BYTES), GFP_KERNEL);
2318         if (!sbinfo)
2319                 return -ENOMEM;
2320
2321         sbinfo->mode = S_IRWXUGO | S_ISVTX;
2322         sbinfo->uid = current_fsuid();
2323         sbinfo->gid = current_fsgid();
2324         sb->s_fs_info = sbinfo;
2325
2326 #ifdef CONFIG_TMPFS
2327         /*
2328          * Per default we only allow half of the physical ram per
2329          * tmpfs instance, limiting inodes to one per page of lowmem;
2330          * but the internal instance is left unlimited.
2331          */
2332         if (!(sb->s_flags & MS_NOUSER)) {
2333                 sbinfo->max_blocks = shmem_default_max_blocks();
2334                 sbinfo->max_inodes = shmem_default_max_inodes();
2335                 if (shmem_parse_options(data, sbinfo, false)) {
2336                         err = -EINVAL;
2337                         goto failed;
2338                 }
2339         }
2340         sb->s_export_op = &shmem_export_ops;
2341 #else
2342         sb->s_flags |= MS_NOUSER;
2343 #endif
2344
2345         spin_lock_init(&sbinfo->stat_lock);
2346         sbinfo->free_blocks = sbinfo->max_blocks;
2347         sbinfo->free_inodes = sbinfo->max_inodes;
2348
2349         sb->s_maxbytes = SHMEM_MAX_BYTES;
2350         sb->s_blocksize = PAGE_CACHE_SIZE;
2351         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2352         sb->s_magic = TMPFS_MAGIC;
2353         sb->s_op = &shmem_ops;
2354         sb->s_time_gran = 1;
2355 #ifdef CONFIG_TMPFS_POSIX_ACL
2356         sb->s_xattr = shmem_xattr_handlers;
2357         sb->s_flags |= MS_POSIXACL;
2358 #endif
2359
2360         inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
2361         if (!inode)
2362                 goto failed;
2363         inode->i_uid = sbinfo->uid;
2364         inode->i_gid = sbinfo->gid;
2365         root = d_alloc_root(inode);
2366         if (!root)
2367                 goto failed_iput;
2368         sb->s_root = root;
2369         return 0;
2370
2371 failed_iput:
2372         iput(inode);
2373 failed:
2374         shmem_put_super(sb);
2375         return err;
2376 }
2377
2378 static struct kmem_cache *shmem_inode_cachep;
2379
2380 static struct inode *shmem_alloc_inode(struct super_block *sb)
2381 {
2382         struct shmem_inode_info *p;
2383         p = (struct shmem_inode_info *)kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2384         if (!p)
2385                 return NULL;
2386         return &p->vfs_inode;
2387 }
2388
2389 static void shmem_destroy_inode(struct inode *inode)
2390 {
2391         if ((inode->i_mode & S_IFMT) == S_IFREG) {
2392                 /* only struct inode is valid if it's an inline symlink */
2393                 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2394         }
2395         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2396 }
2397
2398 static void init_once(void *foo)
2399 {
2400         struct shmem_inode_info *p = (struct shmem_inode_info *) foo;
2401
2402         inode_init_once(&p->vfs_inode);
2403 }
2404
2405 static int init_inodecache(void)
2406 {
2407         shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2408                                 sizeof(struct shmem_inode_info),
2409                                 0, SLAB_PANIC, init_once);
2410         return 0;
2411 }
2412
2413 static void destroy_inodecache(void)
2414 {
2415         kmem_cache_destroy(shmem_inode_cachep);
2416 }
2417
2418 static const struct address_space_operations shmem_aops = {
2419         .writepage      = shmem_writepage,
2420         .set_page_dirty = __set_page_dirty_no_writeback,
2421 #ifdef CONFIG_TMPFS
2422         .readpage       = shmem_readpage,
2423         .write_begin    = shmem_write_begin,
2424         .write_end      = shmem_write_end,
2425 #endif
2426         .migratepage    = migrate_page,
2427         .error_remove_page = generic_error_remove_page,
2428 };
2429
2430 static const struct file_operations shmem_file_operations = {
2431         .mmap           = shmem_mmap,
2432 #ifdef CONFIG_TMPFS
2433         .llseek         = generic_file_llseek,
2434         .read           = do_sync_read,
2435         .write          = do_sync_write,
2436         .aio_read       = shmem_file_aio_read,
2437         .aio_write      = generic_file_aio_write,
2438         .fsync          = simple_sync_file,
2439         .splice_read    = generic_file_splice_read,
2440         .splice_write   = generic_file_splice_write,
2441 #endif
2442 };
2443
2444 static const struct inode_operations shmem_inode_operations = {
2445         .truncate       = shmem_truncate,
2446         .setattr        = shmem_notify_change,
2447         .truncate_range = shmem_truncate_range,
2448 #ifdef CONFIG_TMPFS_POSIX_ACL
2449         .setxattr       = generic_setxattr,
2450         .getxattr       = generic_getxattr,
2451         .listxattr      = generic_listxattr,
2452         .removexattr    = generic_removexattr,
2453         .check_acl      = generic_check_acl,
2454 #endif
2455
2456 };
2457
2458 static const struct inode_operations shmem_dir_inode_operations = {
2459 #ifdef CONFIG_TMPFS
2460         .create         = shmem_create,
2461         .lookup         = simple_lookup,
2462         .link           = shmem_link,
2463         .unlink         = shmem_unlink,
2464         .symlink        = shmem_symlink,
2465         .mkdir          = shmem_mkdir,
2466         .rmdir          = shmem_rmdir,
2467         .mknod          = shmem_mknod,
2468         .rename         = shmem_rename,
2469 #endif
2470 #ifdef CONFIG_TMPFS_POSIX_ACL
2471         .setattr        = shmem_notify_change,
2472         .setxattr       = generic_setxattr,
2473         .getxattr       = generic_getxattr,
2474         .listxattr      = generic_listxattr,
2475         .removexattr    = generic_removexattr,
2476         .check_acl      = generic_check_acl,
2477 #endif
2478 };
2479
2480 static const struct inode_operations shmem_special_inode_operations = {
2481 #ifdef CONFIG_TMPFS_POSIX_ACL
2482         .setattr        = shmem_notify_change,
2483         .setxattr       = generic_setxattr,
2484         .getxattr       = generic_getxattr,
2485         .listxattr      = generic_listxattr,
2486         .removexattr    = generic_removexattr,
2487         .check_acl      = generic_check_acl,
2488 #endif
2489 };
2490
2491 static const struct super_operations shmem_ops = {
2492         .alloc_inode    = shmem_alloc_inode,
2493         .destroy_inode  = shmem_destroy_inode,
2494 #ifdef CONFIG_TMPFS
2495         .statfs         = shmem_statfs,
2496         .remount_fs     = shmem_remount_fs,
2497         .show_options   = shmem_show_options,
2498 #endif
2499         .delete_inode   = shmem_delete_inode,
2500         .drop_inode     = generic_delete_inode,
2501         .put_super      = shmem_put_super,
2502 };
2503
2504 static const struct vm_operations_struct shmem_vm_ops = {
2505         .fault          = shmem_fault,
2506 #ifdef CONFIG_NUMA
2507         .set_policy     = shmem_set_policy,
2508         .get_policy     = shmem_get_policy,
2509 #endif
2510 };
2511
2512
2513 static int shmem_get_sb(struct file_system_type *fs_type,
2514         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
2515 {
2516         return get_sb_nodev(fs_type, flags, data, shmem_fill_super, mnt);
2517 }
2518
2519 static struct file_system_type tmpfs_fs_type = {
2520         .owner          = THIS_MODULE,
2521         .name           = "tmpfs",
2522         .get_sb         = shmem_get_sb,
2523         .kill_sb        = kill_litter_super,
2524 };
2525
2526 int __init init_tmpfs(void)
2527 {
2528         int error;
2529
2530         error = bdi_init(&shmem_backing_dev_info);
2531         if (error)
2532                 goto out4;
2533
2534         error = init_inodecache();
2535         if (error)
2536                 goto out3;
2537
2538         error = register_filesystem(&tmpfs_fs_type);
2539         if (error) {
2540                 printk(KERN_ERR "Could not register tmpfs\n");
2541                 goto out2;
2542         }
2543
2544         shm_mnt = vfs_kern_mount(&tmpfs_fs_type, MS_NOUSER,
2545                                 tmpfs_fs_type.name, NULL);
2546         if (IS_ERR(shm_mnt)) {
2547                 error = PTR_ERR(shm_mnt);
2548                 printk(KERN_ERR "Could not kern_mount tmpfs\n");
2549                 goto out1;
2550         }
2551         return 0;
2552
2553 out1:
2554         unregister_filesystem(&tmpfs_fs_type);
2555 out2:
2556         destroy_inodecache();
2557 out3:
2558         bdi_destroy(&shmem_backing_dev_info);
2559 out4:
2560         shm_mnt = ERR_PTR(error);
2561         return error;
2562 }
2563
2564 #else /* !CONFIG_SHMEM */
2565
2566 /*
2567  * tiny-shmem: simple shmemfs and tmpfs using ramfs code
2568  *
2569  * This is intended for small system where the benefits of the full
2570  * shmem code (swap-backed and resource-limited) are outweighed by
2571  * their complexity. On systems without swap this code should be
2572  * effectively equivalent, but much lighter weight.
2573  */
2574
2575 #include <linux/ramfs.h>
2576
2577 static struct file_system_type tmpfs_fs_type = {
2578         .name           = "tmpfs",
2579         .get_sb         = ramfs_get_sb,
2580         .kill_sb        = kill_litter_super,
2581 };
2582
2583 int __init init_tmpfs(void)
2584 {
2585         BUG_ON(register_filesystem(&tmpfs_fs_type) != 0);
2586
2587         shm_mnt = kern_mount(&tmpfs_fs_type);
2588         BUG_ON(IS_ERR(shm_mnt));
2589
2590         return 0;
2591 }
2592
2593 int shmem_unuse(swp_entry_t entry, struct page *page)
2594 {
2595         return 0;
2596 }
2597
2598 int shmem_lock(struct file *file, int lock, struct user_struct *user)
2599 {
2600         return 0;
2601 }
2602
2603 #define shmem_vm_ops                            generic_file_vm_ops
2604 #define shmem_file_operations                   ramfs_file_operations
2605 #define shmem_get_inode(sb, dir, mode, dev, flags)      ramfs_get_inode(sb, dir, mode, dev)
2606 #define shmem_acct_size(flags, size)            0
2607 #define shmem_unacct_size(flags, size)          do {} while (0)
2608 #define SHMEM_MAX_BYTES                         MAX_LFS_FILESIZE
2609
2610 #endif /* CONFIG_SHMEM */
2611
2612 /* common code */
2613
2614 /**
2615  * shmem_file_setup - get an unlinked file living in tmpfs
2616  * @name: name for dentry (to be seen in /proc/<pid>/maps
2617  * @size: size to be set for the file
2618  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
2619  */
2620 struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
2621 {
2622         int error;
2623         struct file *file;
2624         struct inode *inode;
2625         struct path path;
2626         struct dentry *root;
2627         struct qstr this;
2628
2629         if (IS_ERR(shm_mnt))
2630                 return (void *)shm_mnt;
2631
2632         if (size < 0 || size > SHMEM_MAX_BYTES)
2633                 return ERR_PTR(-EINVAL);
2634
2635         if (shmem_acct_size(flags, size))
2636                 return ERR_PTR(-ENOMEM);
2637
2638         error = -ENOMEM;
2639         this.name = name;
2640         this.len = strlen(name);
2641         this.hash = 0; /* will go */
2642         root = shm_mnt->mnt_root;
2643         path.dentry = d_alloc(root, &this);
2644         if (!path.dentry)
2645                 goto put_memory;
2646         path.mnt = mntget(shm_mnt);
2647
2648         error = -ENOSPC;
2649         inode = shmem_get_inode(root->d_sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
2650         if (!inode)
2651                 goto put_dentry;
2652
2653         d_instantiate(path.dentry, inode);
2654         inode->i_size = size;
2655         inode->i_nlink = 0;     /* It is unlinked */
2656 #ifndef CONFIG_MMU
2657         error = ramfs_nommu_expand_for_mapping(inode, size);
2658         if (error)
2659                 goto put_dentry;
2660 #endif
2661
2662         error = -ENFILE;
2663         file = alloc_file(&path, FMODE_WRITE | FMODE_READ,
2664                   &shmem_file_operations);
2665         if (!file)
2666                 goto put_dentry;
2667
2668         return file;
2669
2670 put_dentry:
2671         path_put(&path);
2672 put_memory:
2673         shmem_unacct_size(flags, size);
2674         return ERR_PTR(error);
2675 }
2676 EXPORT_SYMBOL_GPL(shmem_file_setup);
2677
2678 /**
2679  * shmem_zero_setup - setup a shared anonymous mapping
2680  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2681  */
2682 int shmem_zero_setup(struct vm_area_struct *vma)
2683 {
2684         struct file *file;
2685         loff_t size = vma->vm_end - vma->vm_start;
2686
2687         file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2688         if (IS_ERR(file))
2689                 return PTR_ERR(file);
2690
2691         if (vma->vm_file)
2692                 fput(vma->vm_file);
2693         vma->vm_file = file;
2694         vma->vm_ops = &shmem_vm_ops;
2695         return 0;
2696 }