tmpfs: simplify unuse and writepage
[linux-2.6.git] / mm / shmem.c
1 /*
2  * Resizable virtual memory filesystem for Linux.
3  *
4  * Copyright (C) 2000 Linus Torvalds.
5  *               2000 Transmeta Corp.
6  *               2000-2001 Christoph Rohland
7  *               2000-2001 SAP AG
8  *               2002 Red Hat Inc.
9  * Copyright (C) 2002-2005 Hugh Dickins.
10  * Copyright (C) 2002-2005 VERITAS Software Corporation.
11  * Copyright (C) 2004 Andi Kleen, SuSE Labs
12  *
13  * Extended attribute support for tmpfs:
14  * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
15  * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
16  *
17  * tiny-shmem:
18  * Copyright (c) 2004, 2008 Matt Mackall <mpm@selenic.com>
19  *
20  * This file is released under the GPL.
21  */
22
23 #include <linux/fs.h>
24 #include <linux/init.h>
25 #include <linux/vfs.h>
26 #include <linux/mount.h>
27 #include <linux/pagemap.h>
28 #include <linux/file.h>
29 #include <linux/mm.h>
30 #include <linux/module.h>
31 #include <linux/percpu_counter.h>
32 #include <linux/swap.h>
33
34 static struct vfsmount *shm_mnt;
35
36 #ifdef CONFIG_SHMEM
37 /*
38  * This virtual memory filesystem is heavily based on the ramfs. It
39  * extends ramfs by the ability to use swap and honor resource limits
40  * which makes it a completely usable filesystem.
41  */
42
43 #include <linux/xattr.h>
44 #include <linux/exportfs.h>
45 #include <linux/posix_acl.h>
46 #include <linux/generic_acl.h>
47 #include <linux/mman.h>
48 #include <linux/string.h>
49 #include <linux/slab.h>
50 #include <linux/backing-dev.h>
51 #include <linux/shmem_fs.h>
52 #include <linux/writeback.h>
53 #include <linux/blkdev.h>
54 #include <linux/splice.h>
55 #include <linux/security.h>
56 #include <linux/swapops.h>
57 #include <linux/mempolicy.h>
58 #include <linux/namei.h>
59 #include <linux/ctype.h>
60 #include <linux/migrate.h>
61 #include <linux/highmem.h>
62 #include <linux/seq_file.h>
63 #include <linux/magic.h>
64
65 #include <asm/uaccess.h>
66 #include <asm/div64.h>
67 #include <asm/pgtable.h>
68
69 /*
70  * The maximum size of a shmem/tmpfs file is limited by the maximum size of
71  * its triple-indirect swap vector - see illustration at shmem_swp_entry().
72  *
73  * With 4kB page size, maximum file size is just over 2TB on a 32-bit kernel,
74  * but one eighth of that on a 64-bit kernel.  With 8kB page size, maximum
75  * file size is just over 4TB on a 64-bit kernel, but 16TB on a 32-bit kernel,
76  * MAX_LFS_FILESIZE being then more restrictive than swap vector layout.
77  *
78  * We use / and * instead of shifts in the definitions below, so that the swap
79  * vector can be tested with small even values (e.g. 20) for ENTRIES_PER_PAGE.
80  */
81 #define ENTRIES_PER_PAGE (PAGE_CACHE_SIZE/sizeof(unsigned long))
82 #define ENTRIES_PER_PAGEPAGE ((unsigned long long)ENTRIES_PER_PAGE*ENTRIES_PER_PAGE)
83
84 #define SHMSWP_MAX_INDEX (SHMEM_NR_DIRECT + (ENTRIES_PER_PAGEPAGE/2) * (ENTRIES_PER_PAGE+1))
85 #define SHMSWP_MAX_BYTES (SHMSWP_MAX_INDEX << PAGE_CACHE_SHIFT)
86
87 #define SHMEM_MAX_BYTES  min_t(unsigned long long, SHMSWP_MAX_BYTES, MAX_LFS_FILESIZE)
88 #define SHMEM_MAX_INDEX  ((unsigned long)((SHMEM_MAX_BYTES+1) >> PAGE_CACHE_SHIFT))
89
90 #define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
91 #define VM_ACCT(size)    (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
92
93 /* info->flags needs VM_flags to handle pagein/truncate races efficiently */
94 #define SHMEM_PAGEIN     VM_READ
95 #define SHMEM_TRUNCATE   VM_WRITE
96
97 /* Definition to limit shmem_truncate's steps between cond_rescheds */
98 #define LATENCY_LIMIT    64
99
100 /* Pretend that each entry is of this size in directory's i_size */
101 #define BOGO_DIRENT_SIZE 20
102
103 struct shmem_xattr {
104         struct list_head list;  /* anchored by shmem_inode_info->xattr_list */
105         char *name;             /* xattr name */
106         size_t size;
107         char value[0];
108 };
109
110 /* Flag allocation requirements to shmem_getpage and shmem_swp_alloc */
111 enum sgp_type {
112         SGP_READ,       /* don't exceed i_size, don't allocate page */
113         SGP_CACHE,      /* don't exceed i_size, may allocate page */
114         SGP_DIRTY,      /* like SGP_CACHE, but set new page dirty */
115         SGP_WRITE,      /* may exceed i_size, may allocate page */
116 };
117
118 #ifdef CONFIG_TMPFS
119 static unsigned long shmem_default_max_blocks(void)
120 {
121         return totalram_pages / 2;
122 }
123
124 static unsigned long shmem_default_max_inodes(void)
125 {
126         return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
127 }
128 #endif
129
130 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
131         struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type);
132
133 static inline int shmem_getpage(struct inode *inode, pgoff_t index,
134         struct page **pagep, enum sgp_type sgp, int *fault_type)
135 {
136         return shmem_getpage_gfp(inode, index, pagep, sgp,
137                         mapping_gfp_mask(inode->i_mapping), fault_type);
138 }
139
140 static inline struct page *shmem_dir_alloc(gfp_t gfp_mask)
141 {
142         /*
143          * The above definition of ENTRIES_PER_PAGE, and the use of
144          * BLOCKS_PER_PAGE on indirect pages, assume PAGE_CACHE_SIZE:
145          * might be reconsidered if it ever diverges from PAGE_SIZE.
146          *
147          * Mobility flags are masked out as swap vectors cannot move
148          */
149         return alloc_pages((gfp_mask & ~GFP_MOVABLE_MASK) | __GFP_ZERO,
150                                 PAGE_CACHE_SHIFT-PAGE_SHIFT);
151 }
152
153 static inline void shmem_dir_free(struct page *page)
154 {
155         __free_pages(page, PAGE_CACHE_SHIFT-PAGE_SHIFT);
156 }
157
158 static struct page **shmem_dir_map(struct page *page)
159 {
160         return (struct page **)kmap_atomic(page, KM_USER0);
161 }
162
163 static inline void shmem_dir_unmap(struct page **dir)
164 {
165         kunmap_atomic(dir, KM_USER0);
166 }
167
168 static swp_entry_t *shmem_swp_map(struct page *page)
169 {
170         return (swp_entry_t *)kmap_atomic(page, KM_USER1);
171 }
172
173 static inline void shmem_swp_balance_unmap(void)
174 {
175         /*
176          * When passing a pointer to an i_direct entry, to code which
177          * also handles indirect entries and so will shmem_swp_unmap,
178          * we must arrange for the preempt count to remain in balance.
179          * What kmap_atomic of a lowmem page does depends on config
180          * and architecture, so pretend to kmap_atomic some lowmem page.
181          */
182         (void) kmap_atomic(ZERO_PAGE(0), KM_USER1);
183 }
184
185 static inline void shmem_swp_unmap(swp_entry_t *entry)
186 {
187         kunmap_atomic(entry, KM_USER1);
188 }
189
190 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
191 {
192         return sb->s_fs_info;
193 }
194
195 /*
196  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
197  * for shared memory and for shared anonymous (/dev/zero) mappings
198  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
199  * consistent with the pre-accounting of private mappings ...
200  */
201 static inline int shmem_acct_size(unsigned long flags, loff_t size)
202 {
203         return (flags & VM_NORESERVE) ?
204                 0 : security_vm_enough_memory_kern(VM_ACCT(size));
205 }
206
207 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
208 {
209         if (!(flags & VM_NORESERVE))
210                 vm_unacct_memory(VM_ACCT(size));
211 }
212
213 /*
214  * ... whereas tmpfs objects are accounted incrementally as
215  * pages are allocated, in order to allow huge sparse files.
216  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
217  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
218  */
219 static inline int shmem_acct_block(unsigned long flags)
220 {
221         return (flags & VM_NORESERVE) ?
222                 security_vm_enough_memory_kern(VM_ACCT(PAGE_CACHE_SIZE)) : 0;
223 }
224
225 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
226 {
227         if (flags & VM_NORESERVE)
228                 vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
229 }
230
231 static const struct super_operations shmem_ops;
232 static const struct address_space_operations shmem_aops;
233 static const struct file_operations shmem_file_operations;
234 static const struct inode_operations shmem_inode_operations;
235 static const struct inode_operations shmem_dir_inode_operations;
236 static const struct inode_operations shmem_special_inode_operations;
237 static const struct vm_operations_struct shmem_vm_ops;
238
239 static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
240         .ra_pages       = 0,    /* No readahead */
241         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
242 };
243
244 static LIST_HEAD(shmem_swaplist);
245 static DEFINE_MUTEX(shmem_swaplist_mutex);
246
247 static void shmem_free_blocks(struct inode *inode, long pages)
248 {
249         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
250         if (sbinfo->max_blocks) {
251                 percpu_counter_add(&sbinfo->used_blocks, -pages);
252                 inode->i_blocks -= pages*BLOCKS_PER_PAGE;
253         }
254 }
255
256 static int shmem_reserve_inode(struct super_block *sb)
257 {
258         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
259         if (sbinfo->max_inodes) {
260                 spin_lock(&sbinfo->stat_lock);
261                 if (!sbinfo->free_inodes) {
262                         spin_unlock(&sbinfo->stat_lock);
263                         return -ENOSPC;
264                 }
265                 sbinfo->free_inodes--;
266                 spin_unlock(&sbinfo->stat_lock);
267         }
268         return 0;
269 }
270
271 static void shmem_free_inode(struct super_block *sb)
272 {
273         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
274         if (sbinfo->max_inodes) {
275                 spin_lock(&sbinfo->stat_lock);
276                 sbinfo->free_inodes++;
277                 spin_unlock(&sbinfo->stat_lock);
278         }
279 }
280
281 /**
282  * shmem_recalc_inode - recalculate the size of an inode
283  * @inode: inode to recalc
284  *
285  * We have to calculate the free blocks since the mm can drop
286  * undirtied hole pages behind our back.
287  *
288  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
289  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
290  *
291  * It has to be called with the spinlock held.
292  */
293 static void shmem_recalc_inode(struct inode *inode)
294 {
295         struct shmem_inode_info *info = SHMEM_I(inode);
296         long freed;
297
298         freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
299         if (freed > 0) {
300                 info->alloced -= freed;
301                 shmem_unacct_blocks(info->flags, freed);
302                 shmem_free_blocks(inode, freed);
303         }
304 }
305
306 /**
307  * shmem_swp_entry - find the swap vector position in the info structure
308  * @info:  info structure for the inode
309  * @index: index of the page to find
310  * @page:  optional page to add to the structure. Has to be preset to
311  *         all zeros
312  *
313  * If there is no space allocated yet it will return NULL when
314  * page is NULL, else it will use the page for the needed block,
315  * setting it to NULL on return to indicate that it has been used.
316  *
317  * The swap vector is organized the following way:
318  *
319  * There are SHMEM_NR_DIRECT entries directly stored in the
320  * shmem_inode_info structure. So small files do not need an addional
321  * allocation.
322  *
323  * For pages with index > SHMEM_NR_DIRECT there is the pointer
324  * i_indirect which points to a page which holds in the first half
325  * doubly indirect blocks, in the second half triple indirect blocks:
326  *
327  * For an artificial ENTRIES_PER_PAGE = 4 this would lead to the
328  * following layout (for SHMEM_NR_DIRECT == 16):
329  *
330  * i_indirect -> dir --> 16-19
331  *            |      +-> 20-23
332  *            |
333  *            +-->dir2 --> 24-27
334  *            |        +-> 28-31
335  *            |        +-> 32-35
336  *            |        +-> 36-39
337  *            |
338  *            +-->dir3 --> 40-43
339  *                     +-> 44-47
340  *                     +-> 48-51
341  *                     +-> 52-55
342  */
343 static swp_entry_t *shmem_swp_entry(struct shmem_inode_info *info, unsigned long index, struct page **page)
344 {
345         unsigned long offset;
346         struct page **dir;
347         struct page *subdir;
348
349         if (index < SHMEM_NR_DIRECT) {
350                 shmem_swp_balance_unmap();
351                 return info->i_direct+index;
352         }
353         if (!info->i_indirect) {
354                 if (page) {
355                         info->i_indirect = *page;
356                         *page = NULL;
357                 }
358                 return NULL;                    /* need another page */
359         }
360
361         index -= SHMEM_NR_DIRECT;
362         offset = index % ENTRIES_PER_PAGE;
363         index /= ENTRIES_PER_PAGE;
364         dir = shmem_dir_map(info->i_indirect);
365
366         if (index >= ENTRIES_PER_PAGE/2) {
367                 index -= ENTRIES_PER_PAGE/2;
368                 dir += ENTRIES_PER_PAGE/2 + index/ENTRIES_PER_PAGE;
369                 index %= ENTRIES_PER_PAGE;
370                 subdir = *dir;
371                 if (!subdir) {
372                         if (page) {
373                                 *dir = *page;
374                                 *page = NULL;
375                         }
376                         shmem_dir_unmap(dir);
377                         return NULL;            /* need another page */
378                 }
379                 shmem_dir_unmap(dir);
380                 dir = shmem_dir_map(subdir);
381         }
382
383         dir += index;
384         subdir = *dir;
385         if (!subdir) {
386                 if (!page || !(subdir = *page)) {
387                         shmem_dir_unmap(dir);
388                         return NULL;            /* need a page */
389                 }
390                 *dir = subdir;
391                 *page = NULL;
392         }
393         shmem_dir_unmap(dir);
394         return shmem_swp_map(subdir) + offset;
395 }
396
397 static void shmem_swp_set(struct shmem_inode_info *info, swp_entry_t *entry, unsigned long value)
398 {
399         long incdec = value? 1: -1;
400
401         entry->val = value;
402         info->swapped += incdec;
403         if ((unsigned long)(entry - info->i_direct) >= SHMEM_NR_DIRECT) {
404                 struct page *page = kmap_atomic_to_page(entry);
405                 set_page_private(page, page_private(page) + incdec);
406         }
407 }
408
409 /**
410  * shmem_swp_alloc - get the position of the swap entry for the page.
411  * @info:       info structure for the inode
412  * @index:      index of the page to find
413  * @sgp:        check and recheck i_size? skip allocation?
414  * @gfp:        gfp mask to use for any page allocation
415  *
416  * If the entry does not exist, allocate it.
417  */
418 static swp_entry_t *shmem_swp_alloc(struct shmem_inode_info *info,
419                         unsigned long index, enum sgp_type sgp, gfp_t gfp)
420 {
421         struct inode *inode = &info->vfs_inode;
422         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
423         struct page *page = NULL;
424         swp_entry_t *entry;
425
426         if (sgp != SGP_WRITE &&
427             ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode))
428                 return ERR_PTR(-EINVAL);
429
430         while (!(entry = shmem_swp_entry(info, index, &page))) {
431                 if (sgp == SGP_READ)
432                         return shmem_swp_map(ZERO_PAGE(0));
433                 /*
434                  * Test used_blocks against 1 less max_blocks, since we have 1 data
435                  * page (and perhaps indirect index pages) yet to allocate:
436                  * a waste to allocate index if we cannot allocate data.
437                  */
438                 if (sbinfo->max_blocks) {
439                         if (percpu_counter_compare(&sbinfo->used_blocks,
440                                                 sbinfo->max_blocks - 1) >= 0)
441                                 return ERR_PTR(-ENOSPC);
442                         percpu_counter_inc(&sbinfo->used_blocks);
443                         inode->i_blocks += BLOCKS_PER_PAGE;
444                 }
445
446                 spin_unlock(&info->lock);
447                 page = shmem_dir_alloc(gfp);
448                 spin_lock(&info->lock);
449
450                 if (!page) {
451                         shmem_free_blocks(inode, 1);
452                         return ERR_PTR(-ENOMEM);
453                 }
454                 if (sgp != SGP_WRITE &&
455                     ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
456                         entry = ERR_PTR(-EINVAL);
457                         break;
458                 }
459                 if (info->next_index <= index)
460                         info->next_index = index + 1;
461         }
462         if (page) {
463                 /* another task gave its page, or truncated the file */
464                 shmem_free_blocks(inode, 1);
465                 shmem_dir_free(page);
466         }
467         if (info->next_index <= index && !IS_ERR(entry))
468                 info->next_index = index + 1;
469         return entry;
470 }
471
472 /**
473  * shmem_free_swp - free some swap entries in a directory
474  * @dir:        pointer to the directory
475  * @edir:       pointer after last entry of the directory
476  * @punch_lock: pointer to spinlock when needed for the holepunch case
477  */
478 static int shmem_free_swp(swp_entry_t *dir, swp_entry_t *edir,
479                                                 spinlock_t *punch_lock)
480 {
481         spinlock_t *punch_unlock = NULL;
482         swp_entry_t *ptr;
483         int freed = 0;
484
485         for (ptr = dir; ptr < edir; ptr++) {
486                 if (ptr->val) {
487                         if (unlikely(punch_lock)) {
488                                 punch_unlock = punch_lock;
489                                 punch_lock = NULL;
490                                 spin_lock(punch_unlock);
491                                 if (!ptr->val)
492                                         continue;
493                         }
494                         free_swap_and_cache(*ptr);
495                         *ptr = (swp_entry_t){0};
496                         freed++;
497                 }
498         }
499         if (punch_unlock)
500                 spin_unlock(punch_unlock);
501         return freed;
502 }
503
504 static int shmem_map_and_free_swp(struct page *subdir, int offset,
505                 int limit, struct page ***dir, spinlock_t *punch_lock)
506 {
507         swp_entry_t *ptr;
508         int freed = 0;
509
510         ptr = shmem_swp_map(subdir);
511         for (; offset < limit; offset += LATENCY_LIMIT) {
512                 int size = limit - offset;
513                 if (size > LATENCY_LIMIT)
514                         size = LATENCY_LIMIT;
515                 freed += shmem_free_swp(ptr+offset, ptr+offset+size,
516                                                         punch_lock);
517                 if (need_resched()) {
518                         shmem_swp_unmap(ptr);
519                         if (*dir) {
520                                 shmem_dir_unmap(*dir);
521                                 *dir = NULL;
522                         }
523                         cond_resched();
524                         ptr = shmem_swp_map(subdir);
525                 }
526         }
527         shmem_swp_unmap(ptr);
528         return freed;
529 }
530
531 static void shmem_free_pages(struct list_head *next)
532 {
533         struct page *page;
534         int freed = 0;
535
536         do {
537                 page = container_of(next, struct page, lru);
538                 next = next->next;
539                 shmem_dir_free(page);
540                 freed++;
541                 if (freed >= LATENCY_LIMIT) {
542                         cond_resched();
543                         freed = 0;
544                 }
545         } while (next);
546 }
547
548 void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end)
549 {
550         struct shmem_inode_info *info = SHMEM_I(inode);
551         unsigned long idx;
552         unsigned long size;
553         unsigned long limit;
554         unsigned long stage;
555         unsigned long diroff;
556         struct page **dir;
557         struct page *topdir;
558         struct page *middir;
559         struct page *subdir;
560         swp_entry_t *ptr;
561         LIST_HEAD(pages_to_free);
562         long nr_pages_to_free = 0;
563         long nr_swaps_freed = 0;
564         int offset;
565         int freed;
566         int punch_hole;
567         spinlock_t *needs_lock;
568         spinlock_t *punch_lock;
569         unsigned long upper_limit;
570
571         truncate_inode_pages_range(inode->i_mapping, start, end);
572
573         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
574         idx = (start + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
575         if (idx >= info->next_index)
576                 return;
577
578         spin_lock(&info->lock);
579         info->flags |= SHMEM_TRUNCATE;
580         if (likely(end == (loff_t) -1)) {
581                 limit = info->next_index;
582                 upper_limit = SHMEM_MAX_INDEX;
583                 info->next_index = idx;
584                 needs_lock = NULL;
585                 punch_hole = 0;
586         } else {
587                 if (end + 1 >= inode->i_size) { /* we may free a little more */
588                         limit = (inode->i_size + PAGE_CACHE_SIZE - 1) >>
589                                                         PAGE_CACHE_SHIFT;
590                         upper_limit = SHMEM_MAX_INDEX;
591                 } else {
592                         limit = (end + 1) >> PAGE_CACHE_SHIFT;
593                         upper_limit = limit;
594                 }
595                 needs_lock = &info->lock;
596                 punch_hole = 1;
597         }
598
599         topdir = info->i_indirect;
600         if (topdir && idx <= SHMEM_NR_DIRECT && !punch_hole) {
601                 info->i_indirect = NULL;
602                 nr_pages_to_free++;
603                 list_add(&topdir->lru, &pages_to_free);
604         }
605         spin_unlock(&info->lock);
606
607         if (info->swapped && idx < SHMEM_NR_DIRECT) {
608                 ptr = info->i_direct;
609                 size = limit;
610                 if (size > SHMEM_NR_DIRECT)
611                         size = SHMEM_NR_DIRECT;
612                 nr_swaps_freed = shmem_free_swp(ptr+idx, ptr+size, needs_lock);
613         }
614
615         /*
616          * If there are no indirect blocks or we are punching a hole
617          * below indirect blocks, nothing to be done.
618          */
619         if (!topdir || limit <= SHMEM_NR_DIRECT)
620                 goto done2;
621
622         /*
623          * The truncation case has already dropped info->lock, and we're safe
624          * because i_size and next_index have already been lowered, preventing
625          * access beyond.  But in the punch_hole case, we still need to take
626          * the lock when updating the swap directory, because there might be
627          * racing accesses by shmem_getpage(SGP_CACHE), shmem_unuse_inode or
628          * shmem_writepage.  However, whenever we find we can remove a whole
629          * directory page (not at the misaligned start or end of the range),
630          * we first NULLify its pointer in the level above, and then have no
631          * need to take the lock when updating its contents: needs_lock and
632          * punch_lock (either pointing to info->lock or NULL) manage this.
633          */
634
635         upper_limit -= SHMEM_NR_DIRECT;
636         limit -= SHMEM_NR_DIRECT;
637         idx = (idx > SHMEM_NR_DIRECT)? (idx - SHMEM_NR_DIRECT): 0;
638         offset = idx % ENTRIES_PER_PAGE;
639         idx -= offset;
640
641         dir = shmem_dir_map(topdir);
642         stage = ENTRIES_PER_PAGEPAGE/2;
643         if (idx < ENTRIES_PER_PAGEPAGE/2) {
644                 middir = topdir;
645                 diroff = idx/ENTRIES_PER_PAGE;
646         } else {
647                 dir += ENTRIES_PER_PAGE/2;
648                 dir += (idx - ENTRIES_PER_PAGEPAGE/2)/ENTRIES_PER_PAGEPAGE;
649                 while (stage <= idx)
650                         stage += ENTRIES_PER_PAGEPAGE;
651                 middir = *dir;
652                 if (*dir) {
653                         diroff = ((idx - ENTRIES_PER_PAGEPAGE/2) %
654                                 ENTRIES_PER_PAGEPAGE) / ENTRIES_PER_PAGE;
655                         if (!diroff && !offset && upper_limit >= stage) {
656                                 if (needs_lock) {
657                                         spin_lock(needs_lock);
658                                         *dir = NULL;
659                                         spin_unlock(needs_lock);
660                                         needs_lock = NULL;
661                                 } else
662                                         *dir = NULL;
663                                 nr_pages_to_free++;
664                                 list_add(&middir->lru, &pages_to_free);
665                         }
666                         shmem_dir_unmap(dir);
667                         dir = shmem_dir_map(middir);
668                 } else {
669                         diroff = 0;
670                         offset = 0;
671                         idx = stage;
672                 }
673         }
674
675         for (; idx < limit; idx += ENTRIES_PER_PAGE, diroff++) {
676                 if (unlikely(idx == stage)) {
677                         shmem_dir_unmap(dir);
678                         dir = shmem_dir_map(topdir) +
679                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
680                         while (!*dir) {
681                                 dir++;
682                                 idx += ENTRIES_PER_PAGEPAGE;
683                                 if (idx >= limit)
684                                         goto done1;
685                         }
686                         stage = idx + ENTRIES_PER_PAGEPAGE;
687                         middir = *dir;
688                         if (punch_hole)
689                                 needs_lock = &info->lock;
690                         if (upper_limit >= stage) {
691                                 if (needs_lock) {
692                                         spin_lock(needs_lock);
693                                         *dir = NULL;
694                                         spin_unlock(needs_lock);
695                                         needs_lock = NULL;
696                                 } else
697                                         *dir = NULL;
698                                 nr_pages_to_free++;
699                                 list_add(&middir->lru, &pages_to_free);
700                         }
701                         shmem_dir_unmap(dir);
702                         cond_resched();
703                         dir = shmem_dir_map(middir);
704                         diroff = 0;
705                 }
706                 punch_lock = needs_lock;
707                 subdir = dir[diroff];
708                 if (subdir && !offset && upper_limit-idx >= ENTRIES_PER_PAGE) {
709                         if (needs_lock) {
710                                 spin_lock(needs_lock);
711                                 dir[diroff] = NULL;
712                                 spin_unlock(needs_lock);
713                                 punch_lock = NULL;
714                         } else
715                                 dir[diroff] = NULL;
716                         nr_pages_to_free++;
717                         list_add(&subdir->lru, &pages_to_free);
718                 }
719                 if (subdir && page_private(subdir) /* has swap entries */) {
720                         size = limit - idx;
721                         if (size > ENTRIES_PER_PAGE)
722                                 size = ENTRIES_PER_PAGE;
723                         freed = shmem_map_and_free_swp(subdir,
724                                         offset, size, &dir, punch_lock);
725                         if (!dir)
726                                 dir = shmem_dir_map(middir);
727                         nr_swaps_freed += freed;
728                         if (offset || punch_lock) {
729                                 spin_lock(&info->lock);
730                                 set_page_private(subdir,
731                                         page_private(subdir) - freed);
732                                 spin_unlock(&info->lock);
733                         } else
734                                 BUG_ON(page_private(subdir) != freed);
735                 }
736                 offset = 0;
737         }
738 done1:
739         shmem_dir_unmap(dir);
740 done2:
741         if (inode->i_mapping->nrpages && (info->flags & SHMEM_PAGEIN)) {
742                 /*
743                  * Call truncate_inode_pages again: racing shmem_unuse_inode
744                  * may have swizzled a page in from swap since
745                  * truncate_pagecache or generic_delete_inode did it, before we
746                  * lowered next_index.  Also, though shmem_getpage checks
747                  * i_size before adding to cache, no recheck after: so fix the
748                  * narrow window there too.
749                  */
750                 truncate_inode_pages_range(inode->i_mapping, start, end);
751         }
752
753         spin_lock(&info->lock);
754         info->flags &= ~SHMEM_TRUNCATE;
755         info->swapped -= nr_swaps_freed;
756         if (nr_pages_to_free)
757                 shmem_free_blocks(inode, nr_pages_to_free);
758         shmem_recalc_inode(inode);
759         spin_unlock(&info->lock);
760
761         /*
762          * Empty swap vector directory pages to be freed?
763          */
764         if (!list_empty(&pages_to_free)) {
765                 pages_to_free.prev->next = NULL;
766                 shmem_free_pages(pages_to_free.next);
767         }
768 }
769 EXPORT_SYMBOL_GPL(shmem_truncate_range);
770
771 static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
772 {
773         struct inode *inode = dentry->d_inode;
774         int error;
775
776         error = inode_change_ok(inode, attr);
777         if (error)
778                 return error;
779
780         if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
781                 loff_t oldsize = inode->i_size;
782                 loff_t newsize = attr->ia_size;
783                 struct page *page = NULL;
784
785                 if (newsize < oldsize) {
786                         /*
787                          * If truncating down to a partial page, then
788                          * if that page is already allocated, hold it
789                          * in memory until the truncation is over, so
790                          * truncate_partial_page cannot miss it were
791                          * it assigned to swap.
792                          */
793                         if (newsize & (PAGE_CACHE_SIZE-1)) {
794                                 (void) shmem_getpage(inode,
795                                         newsize >> PAGE_CACHE_SHIFT,
796                                                 &page, SGP_READ, NULL);
797                                 if (page)
798                                         unlock_page(page);
799                         }
800                         /*
801                          * Reset SHMEM_PAGEIN flag so that shmem_truncate can
802                          * detect if any pages might have been added to cache
803                          * after truncate_inode_pages.  But we needn't bother
804                          * if it's being fully truncated to zero-length: the
805                          * nrpages check is efficient enough in that case.
806                          */
807                         if (newsize) {
808                                 struct shmem_inode_info *info = SHMEM_I(inode);
809                                 spin_lock(&info->lock);
810                                 info->flags &= ~SHMEM_PAGEIN;
811                                 spin_unlock(&info->lock);
812                         }
813                 }
814                 if (newsize != oldsize) {
815                         i_size_write(inode, newsize);
816                         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
817                 }
818                 if (newsize < oldsize) {
819                         loff_t holebegin = round_up(newsize, PAGE_SIZE);
820                         unmap_mapping_range(inode->i_mapping, holebegin, 0, 1);
821                         shmem_truncate_range(inode, newsize, (loff_t)-1);
822                         /* unmap again to remove racily COWed private pages */
823                         unmap_mapping_range(inode->i_mapping, holebegin, 0, 1);
824                 }
825                 if (page)
826                         page_cache_release(page);
827         }
828
829         setattr_copy(inode, attr);
830 #ifdef CONFIG_TMPFS_POSIX_ACL
831         if (attr->ia_valid & ATTR_MODE)
832                 error = generic_acl_chmod(inode);
833 #endif
834         return error;
835 }
836
837 static void shmem_evict_inode(struct inode *inode)
838 {
839         struct shmem_inode_info *info = SHMEM_I(inode);
840         struct shmem_xattr *xattr, *nxattr;
841
842         if (inode->i_mapping->a_ops == &shmem_aops) {
843                 shmem_unacct_size(info->flags, inode->i_size);
844                 inode->i_size = 0;
845                 shmem_truncate_range(inode, 0, (loff_t)-1);
846                 if (!list_empty(&info->swaplist)) {
847                         mutex_lock(&shmem_swaplist_mutex);
848                         list_del_init(&info->swaplist);
849                         mutex_unlock(&shmem_swaplist_mutex);
850                 }
851         }
852
853         list_for_each_entry_safe(xattr, nxattr, &info->xattr_list, list) {
854                 kfree(xattr->name);
855                 kfree(xattr);
856         }
857         BUG_ON(inode->i_blocks);
858         shmem_free_inode(inode->i_sb);
859         end_writeback(inode);
860 }
861
862 static inline int shmem_find_swp(swp_entry_t entry, swp_entry_t *dir, swp_entry_t *edir)
863 {
864         swp_entry_t *ptr;
865
866         for (ptr = dir; ptr < edir; ptr++) {
867                 if (ptr->val == entry.val)
868                         return ptr - dir;
869         }
870         return -1;
871 }
872
873 static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t entry, struct page *page)
874 {
875         struct address_space *mapping;
876         unsigned long idx;
877         unsigned long size;
878         unsigned long limit;
879         unsigned long stage;
880         struct page **dir;
881         struct page *subdir;
882         swp_entry_t *ptr;
883         int offset;
884         int error;
885
886         idx = 0;
887         ptr = info->i_direct;
888         spin_lock(&info->lock);
889         if (!info->swapped) {
890                 list_del_init(&info->swaplist);
891                 goto lost2;
892         }
893         limit = info->next_index;
894         size = limit;
895         if (size > SHMEM_NR_DIRECT)
896                 size = SHMEM_NR_DIRECT;
897         offset = shmem_find_swp(entry, ptr, ptr+size);
898         if (offset >= 0) {
899                 shmem_swp_balance_unmap();
900                 goto found;
901         }
902         if (!info->i_indirect)
903                 goto lost2;
904
905         dir = shmem_dir_map(info->i_indirect);
906         stage = SHMEM_NR_DIRECT + ENTRIES_PER_PAGEPAGE/2;
907
908         for (idx = SHMEM_NR_DIRECT; idx < limit; idx += ENTRIES_PER_PAGE, dir++) {
909                 if (unlikely(idx == stage)) {
910                         shmem_dir_unmap(dir-1);
911                         if (cond_resched_lock(&info->lock)) {
912                                 /* check it has not been truncated */
913                                 if (limit > info->next_index) {
914                                         limit = info->next_index;
915                                         if (idx >= limit)
916                                                 goto lost2;
917                                 }
918                         }
919                         dir = shmem_dir_map(info->i_indirect) +
920                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
921                         while (!*dir) {
922                                 dir++;
923                                 idx += ENTRIES_PER_PAGEPAGE;
924                                 if (idx >= limit)
925                                         goto lost1;
926                         }
927                         stage = idx + ENTRIES_PER_PAGEPAGE;
928                         subdir = *dir;
929                         shmem_dir_unmap(dir);
930                         dir = shmem_dir_map(subdir);
931                 }
932                 subdir = *dir;
933                 if (subdir && page_private(subdir)) {
934                         ptr = shmem_swp_map(subdir);
935                         size = limit - idx;
936                         if (size > ENTRIES_PER_PAGE)
937                                 size = ENTRIES_PER_PAGE;
938                         offset = shmem_find_swp(entry, ptr, ptr+size);
939                         shmem_swp_unmap(ptr);
940                         if (offset >= 0) {
941                                 shmem_dir_unmap(dir);
942                                 ptr = shmem_swp_map(subdir);
943                                 goto found;
944                         }
945                 }
946         }
947 lost1:
948         shmem_dir_unmap(dir-1);
949 lost2:
950         spin_unlock(&info->lock);
951         return 0;
952 found:
953         idx += offset;
954         ptr += offset;
955
956         /*
957          * Move _head_ to start search for next from here.
958          * But be careful: shmem_evict_inode checks list_empty without taking
959          * mutex, and there's an instant in list_move_tail when info->swaplist
960          * would appear empty, if it were the only one on shmem_swaplist.  We
961          * could avoid doing it if inode NULL; or use this minor optimization.
962          */
963         if (shmem_swaplist.next != &info->swaplist)
964                 list_move_tail(&shmem_swaplist, &info->swaplist);
965
966         /*
967          * We rely on shmem_swaplist_mutex, not only to protect the swaplist,
968          * but also to hold up shmem_evict_inode(): so inode cannot be freed
969          * beneath us (pagelock doesn't help until the page is in pagecache).
970          */
971         mapping = info->vfs_inode.i_mapping;
972         error = add_to_page_cache_locked(page, mapping, idx, GFP_NOWAIT);
973         /* which does mem_cgroup_uncharge_cache_page on error */
974
975         if (error != -ENOMEM) {
976                 delete_from_swap_cache(page);
977                 set_page_dirty(page);
978                 info->flags |= SHMEM_PAGEIN;
979                 shmem_swp_set(info, ptr, 0);
980                 swap_free(entry);
981                 error = 1;      /* not an error, but entry was found */
982         }
983         shmem_swp_unmap(ptr);
984         spin_unlock(&info->lock);
985         return error;
986 }
987
988 /*
989  * shmem_unuse() search for an eventually swapped out shmem page.
990  */
991 int shmem_unuse(swp_entry_t entry, struct page *page)
992 {
993         struct list_head *p, *next;
994         struct shmem_inode_info *info;
995         int found = 0;
996         int error;
997
998         /*
999          * Charge page using GFP_KERNEL while we can wait, before taking
1000          * the shmem_swaplist_mutex which might hold up shmem_writepage().
1001          * Charged back to the user (not to caller) when swap account is used.
1002          * add_to_page_cache() will be called with GFP_NOWAIT.
1003          */
1004         error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL);
1005         if (error)
1006                 goto out;
1007         /*
1008          * Try to preload while we can wait, to not make a habit of
1009          * draining atomic reserves; but don't latch on to this cpu,
1010          * it's okay if sometimes we get rescheduled after this.
1011          */
1012         error = radix_tree_preload(GFP_KERNEL);
1013         if (error)
1014                 goto uncharge;
1015         radix_tree_preload_end();
1016
1017         mutex_lock(&shmem_swaplist_mutex);
1018         list_for_each_safe(p, next, &shmem_swaplist) {
1019                 info = list_entry(p, struct shmem_inode_info, swaplist);
1020                 found = shmem_unuse_inode(info, entry, page);
1021                 cond_resched();
1022                 if (found)
1023                         break;
1024         }
1025         mutex_unlock(&shmem_swaplist_mutex);
1026
1027 uncharge:
1028         if (!found)
1029                 mem_cgroup_uncharge_cache_page(page);
1030         if (found < 0)
1031                 error = found;
1032 out:
1033         unlock_page(page);
1034         page_cache_release(page);
1035         return error;
1036 }
1037
1038 /*
1039  * Move the page from the page cache to the swap cache.
1040  */
1041 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
1042 {
1043         struct shmem_inode_info *info;
1044         swp_entry_t *entry, swap;
1045         struct address_space *mapping;
1046         unsigned long index;
1047         struct inode *inode;
1048
1049         BUG_ON(!PageLocked(page));
1050         mapping = page->mapping;
1051         index = page->index;
1052         inode = mapping->host;
1053         info = SHMEM_I(inode);
1054         if (info->flags & VM_LOCKED)
1055                 goto redirty;
1056         if (!total_swap_pages)
1057                 goto redirty;
1058
1059         /*
1060          * shmem_backing_dev_info's capabilities prevent regular writeback or
1061          * sync from ever calling shmem_writepage; but a stacking filesystem
1062          * might use ->writepage of its underlying filesystem, in which case
1063          * tmpfs should write out to swap only in response to memory pressure,
1064          * and not for the writeback threads or sync.
1065          */
1066         if (!wbc->for_reclaim) {
1067                 WARN_ON_ONCE(1);        /* Still happens? Tell us about it! */
1068                 goto redirty;
1069         }
1070         swap = get_swap_page();
1071         if (!swap.val)
1072                 goto redirty;
1073
1074         /*
1075          * Add inode to shmem_unuse()'s list of swapped-out inodes,
1076          * if it's not already there.  Do it now because we cannot take
1077          * mutex while holding spinlock, and must do so before the page
1078          * is moved to swap cache, when its pagelock no longer protects
1079          * the inode from eviction.  But don't unlock the mutex until
1080          * we've taken the spinlock, because shmem_unuse_inode() will
1081          * prune a !swapped inode from the swaplist under both locks.
1082          */
1083         mutex_lock(&shmem_swaplist_mutex);
1084         if (list_empty(&info->swaplist))
1085                 list_add_tail(&info->swaplist, &shmem_swaplist);
1086
1087         spin_lock(&info->lock);
1088         mutex_unlock(&shmem_swaplist_mutex);
1089
1090         if (index >= info->next_index) {
1091                 BUG_ON(!(info->flags & SHMEM_TRUNCATE));
1092                 goto unlock;
1093         }
1094         entry = shmem_swp_entry(info, index, NULL);
1095         if (entry->val) {
1096                 WARN_ON_ONCE(1);        /* Still happens? Tell us about it! */
1097                 free_swap_and_cache(*entry);
1098                 shmem_swp_set(info, entry, 0);
1099         }
1100         shmem_recalc_inode(inode);
1101
1102         if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
1103                 delete_from_page_cache(page);
1104                 shmem_swp_set(info, entry, swap.val);
1105                 shmem_swp_unmap(entry);
1106                 swap_shmem_alloc(swap);
1107                 spin_unlock(&info->lock);
1108                 BUG_ON(page_mapped(page));
1109                 swap_writepage(page, wbc);
1110                 return 0;
1111         }
1112
1113         shmem_swp_unmap(entry);
1114 unlock:
1115         spin_unlock(&info->lock);
1116         /*
1117          * add_to_swap_cache() doesn't return -EEXIST, so we can safely
1118          * clear SWAP_HAS_CACHE flag.
1119          */
1120         swapcache_free(swap, NULL);
1121 redirty:
1122         set_page_dirty(page);
1123         if (wbc->for_reclaim)
1124                 return AOP_WRITEPAGE_ACTIVATE;  /* Return with page locked */
1125         unlock_page(page);
1126         return 0;
1127 }
1128
1129 #ifdef CONFIG_NUMA
1130 #ifdef CONFIG_TMPFS
1131 static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1132 {
1133         char buffer[64];
1134
1135         if (!mpol || mpol->mode == MPOL_DEFAULT)
1136                 return;         /* show nothing */
1137
1138         mpol_to_str(buffer, sizeof(buffer), mpol, 1);
1139
1140         seq_printf(seq, ",mpol=%s", buffer);
1141 }
1142
1143 static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1144 {
1145         struct mempolicy *mpol = NULL;
1146         if (sbinfo->mpol) {
1147                 spin_lock(&sbinfo->stat_lock);  /* prevent replace/use races */
1148                 mpol = sbinfo->mpol;
1149                 mpol_get(mpol);
1150                 spin_unlock(&sbinfo->stat_lock);
1151         }
1152         return mpol;
1153 }
1154 #endif /* CONFIG_TMPFS */
1155
1156 static struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
1157                         struct shmem_inode_info *info, unsigned long idx)
1158 {
1159         struct mempolicy mpol, *spol;
1160         struct vm_area_struct pvma;
1161         struct page *page;
1162
1163         spol = mpol_cond_copy(&mpol,
1164                                 mpol_shared_policy_lookup(&info->policy, idx));
1165
1166         /* Create a pseudo vma that just contains the policy */
1167         pvma.vm_start = 0;
1168         pvma.vm_pgoff = idx;
1169         pvma.vm_ops = NULL;
1170         pvma.vm_policy = spol;
1171         page = swapin_readahead(entry, gfp, &pvma, 0);
1172         return page;
1173 }
1174
1175 static struct page *shmem_alloc_page(gfp_t gfp,
1176                         struct shmem_inode_info *info, unsigned long idx)
1177 {
1178         struct vm_area_struct pvma;
1179
1180         /* Create a pseudo vma that just contains the policy */
1181         pvma.vm_start = 0;
1182         pvma.vm_pgoff = idx;
1183         pvma.vm_ops = NULL;
1184         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
1185
1186         /*
1187          * alloc_page_vma() will drop the shared policy reference
1188          */
1189         return alloc_page_vma(gfp, &pvma, 0);
1190 }
1191 #else /* !CONFIG_NUMA */
1192 #ifdef CONFIG_TMPFS
1193 static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *p)
1194 {
1195 }
1196 #endif /* CONFIG_TMPFS */
1197
1198 static inline struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
1199                         struct shmem_inode_info *info, unsigned long idx)
1200 {
1201         return swapin_readahead(entry, gfp, NULL, 0);
1202 }
1203
1204 static inline struct page *shmem_alloc_page(gfp_t gfp,
1205                         struct shmem_inode_info *info, unsigned long idx)
1206 {
1207         return alloc_page(gfp);
1208 }
1209 #endif /* CONFIG_NUMA */
1210
1211 #if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS)
1212 static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1213 {
1214         return NULL;
1215 }
1216 #endif
1217
1218 /*
1219  * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
1220  *
1221  * If we allocate a new one we do not mark it dirty. That's up to the
1222  * vm. If we swap it in we mark it dirty since we also free the swap
1223  * entry since a page cannot live in both the swap and page cache
1224  */
1225 static int shmem_getpage_gfp(struct inode *inode, pgoff_t idx,
1226         struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type)
1227 {
1228         struct address_space *mapping = inode->i_mapping;
1229         struct shmem_inode_info *info = SHMEM_I(inode);
1230         struct shmem_sb_info *sbinfo;
1231         struct page *page;
1232         struct page *prealloc_page = NULL;
1233         swp_entry_t *entry;
1234         swp_entry_t swap;
1235         int error;
1236         int ret;
1237
1238         if (idx >= SHMEM_MAX_INDEX)
1239                 return -EFBIG;
1240 repeat:
1241         page = find_lock_page(mapping, idx);
1242         if (page) {
1243                 /*
1244                  * Once we can get the page lock, it must be uptodate:
1245                  * if there were an error in reading back from swap,
1246                  * the page would not be inserted into the filecache.
1247                  */
1248                 BUG_ON(!PageUptodate(page));
1249                 goto done;
1250         }
1251
1252         /*
1253          * Try to preload while we can wait, to not make a habit of
1254          * draining atomic reserves; but don't latch on to this cpu.
1255          */
1256         error = radix_tree_preload(gfp & GFP_RECLAIM_MASK);
1257         if (error)
1258                 goto out;
1259         radix_tree_preload_end();
1260
1261         if (sgp != SGP_READ && !prealloc_page) {
1262                 prealloc_page = shmem_alloc_page(gfp, info, idx);
1263                 if (prealloc_page) {
1264                         SetPageSwapBacked(prealloc_page);
1265                         if (mem_cgroup_cache_charge(prealloc_page,
1266                                         current->mm, GFP_KERNEL)) {
1267                                 page_cache_release(prealloc_page);
1268                                 prealloc_page = NULL;
1269                         }
1270                 }
1271         }
1272
1273         spin_lock(&info->lock);
1274         shmem_recalc_inode(inode);
1275         entry = shmem_swp_alloc(info, idx, sgp, gfp);
1276         if (IS_ERR(entry)) {
1277                 spin_unlock(&info->lock);
1278                 error = PTR_ERR(entry);
1279                 goto out;
1280         }
1281         swap = *entry;
1282
1283         if (swap.val) {
1284                 /* Look it up and read it in.. */
1285                 page = lookup_swap_cache(swap);
1286                 if (!page) {
1287                         shmem_swp_unmap(entry);
1288                         spin_unlock(&info->lock);
1289                         /* here we actually do the io */
1290                         if (fault_type)
1291                                 *fault_type |= VM_FAULT_MAJOR;
1292                         page = shmem_swapin(swap, gfp, info, idx);
1293                         if (!page) {
1294                                 spin_lock(&info->lock);
1295                                 entry = shmem_swp_alloc(info, idx, sgp, gfp);
1296                                 if (IS_ERR(entry))
1297                                         error = PTR_ERR(entry);
1298                                 else {
1299                                         if (entry->val == swap.val)
1300                                                 error = -ENOMEM;
1301                                         shmem_swp_unmap(entry);
1302                                 }
1303                                 spin_unlock(&info->lock);
1304                                 if (error)
1305                                         goto out;
1306                                 goto repeat;
1307                         }
1308                         wait_on_page_locked(page);
1309                         page_cache_release(page);
1310                         goto repeat;
1311                 }
1312
1313                 /* We have to do this with page locked to prevent races */
1314                 if (!trylock_page(page)) {
1315                         shmem_swp_unmap(entry);
1316                         spin_unlock(&info->lock);
1317                         wait_on_page_locked(page);
1318                         page_cache_release(page);
1319                         goto repeat;
1320                 }
1321                 if (PageWriteback(page)) {
1322                         shmem_swp_unmap(entry);
1323                         spin_unlock(&info->lock);
1324                         wait_on_page_writeback(page);
1325                         unlock_page(page);
1326                         page_cache_release(page);
1327                         goto repeat;
1328                 }
1329                 if (!PageUptodate(page)) {
1330                         shmem_swp_unmap(entry);
1331                         spin_unlock(&info->lock);
1332                         unlock_page(page);
1333                         page_cache_release(page);
1334                         error = -EIO;
1335                         goto out;
1336                 }
1337
1338                 error = add_to_page_cache_locked(page, mapping,
1339                                                  idx, GFP_NOWAIT);
1340                 if (error) {
1341                         shmem_swp_unmap(entry);
1342                         spin_unlock(&info->lock);
1343                         if (error == -ENOMEM) {
1344                                 /*
1345                                  * reclaim from proper memory cgroup and
1346                                  * call memcg's OOM if needed.
1347                                  */
1348                                 error = mem_cgroup_shmem_charge_fallback(
1349                                                 page, current->mm, gfp);
1350                                 if (error) {
1351                                         unlock_page(page);
1352                                         page_cache_release(page);
1353                                         goto out;
1354                                 }
1355                         }
1356                         unlock_page(page);
1357                         page_cache_release(page);
1358                         goto repeat;
1359                 }
1360
1361                 info->flags |= SHMEM_PAGEIN;
1362                 shmem_swp_set(info, entry, 0);
1363                 shmem_swp_unmap(entry);
1364                 delete_from_swap_cache(page);
1365                 spin_unlock(&info->lock);
1366                 set_page_dirty(page);
1367                 swap_free(swap);
1368
1369         } else if (sgp == SGP_READ) {
1370                 shmem_swp_unmap(entry);
1371                 page = find_get_page(mapping, idx);
1372                 if (page && !trylock_page(page)) {
1373                         spin_unlock(&info->lock);
1374                         wait_on_page_locked(page);
1375                         page_cache_release(page);
1376                         goto repeat;
1377                 }
1378                 spin_unlock(&info->lock);
1379
1380         } else if (prealloc_page) {
1381                 shmem_swp_unmap(entry);
1382                 sbinfo = SHMEM_SB(inode->i_sb);
1383                 if (sbinfo->max_blocks) {
1384                         if (percpu_counter_compare(&sbinfo->used_blocks,
1385                                                 sbinfo->max_blocks) >= 0 ||
1386                             shmem_acct_block(info->flags))
1387                                 goto nospace;
1388                         percpu_counter_inc(&sbinfo->used_blocks);
1389                         inode->i_blocks += BLOCKS_PER_PAGE;
1390                 } else if (shmem_acct_block(info->flags))
1391                         goto nospace;
1392
1393                 page = prealloc_page;
1394                 prealloc_page = NULL;
1395
1396                 entry = shmem_swp_alloc(info, idx, sgp, gfp);
1397                 if (IS_ERR(entry))
1398                         error = PTR_ERR(entry);
1399                 else {
1400                         swap = *entry;
1401                         shmem_swp_unmap(entry);
1402                 }
1403                 ret = error || swap.val;
1404                 if (ret)
1405                         mem_cgroup_uncharge_cache_page(page);
1406                 else
1407                         ret = add_to_page_cache_lru(page, mapping,
1408                                                 idx, GFP_NOWAIT);
1409                 /*
1410                  * At add_to_page_cache_lru() failure,
1411                  * uncharge will be done automatically.
1412                  */
1413                 if (ret) {
1414                         shmem_unacct_blocks(info->flags, 1);
1415                         shmem_free_blocks(inode, 1);
1416                         spin_unlock(&info->lock);
1417                         page_cache_release(page);
1418                         if (error)
1419                                 goto out;
1420                         goto repeat;
1421                 }
1422
1423                 info->flags |= SHMEM_PAGEIN;
1424                 info->alloced++;
1425                 spin_unlock(&info->lock);
1426                 clear_highpage(page);
1427                 flush_dcache_page(page);
1428                 SetPageUptodate(page);
1429                 if (sgp == SGP_DIRTY)
1430                         set_page_dirty(page);
1431
1432         } else {
1433                 spin_unlock(&info->lock);
1434                 error = -ENOMEM;
1435                 goto out;
1436         }
1437 done:
1438         *pagep = page;
1439         error = 0;
1440 out:
1441         if (prealloc_page) {
1442                 mem_cgroup_uncharge_cache_page(prealloc_page);
1443                 page_cache_release(prealloc_page);
1444         }
1445         return error;
1446
1447 nospace:
1448         /*
1449          * Perhaps the page was brought in from swap between find_lock_page
1450          * and taking info->lock?  We allow for that at add_to_page_cache_lru,
1451          * but must also avoid reporting a spurious ENOSPC while working on a
1452          * full tmpfs.
1453          */
1454         page = find_get_page(mapping, idx);
1455         spin_unlock(&info->lock);
1456         if (page) {
1457                 page_cache_release(page);
1458                 goto repeat;
1459         }
1460         error = -ENOSPC;
1461         goto out;
1462 }
1463
1464 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1465 {
1466         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1467         int error;
1468         int ret = VM_FAULT_LOCKED;
1469
1470         if (((loff_t)vmf->pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
1471                 return VM_FAULT_SIGBUS;
1472
1473         error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
1474         if (error)
1475                 return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1476
1477         if (ret & VM_FAULT_MAJOR) {
1478                 count_vm_event(PGMAJFAULT);
1479                 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1480         }
1481         return ret;
1482 }
1483
1484 #ifdef CONFIG_NUMA
1485 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *new)
1486 {
1487         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1488         return mpol_set_shared_policy(&SHMEM_I(i)->policy, vma, new);
1489 }
1490
1491 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
1492                                           unsigned long addr)
1493 {
1494         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1495         unsigned long idx;
1496
1497         idx = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1498         return mpol_shared_policy_lookup(&SHMEM_I(i)->policy, idx);
1499 }
1500 #endif
1501
1502 int shmem_lock(struct file *file, int lock, struct user_struct *user)
1503 {
1504         struct inode *inode = file->f_path.dentry->d_inode;
1505         struct shmem_inode_info *info = SHMEM_I(inode);
1506         int retval = -ENOMEM;
1507
1508         spin_lock(&info->lock);
1509         if (lock && !(info->flags & VM_LOCKED)) {
1510                 if (!user_shm_lock(inode->i_size, user))
1511                         goto out_nomem;
1512                 info->flags |= VM_LOCKED;
1513                 mapping_set_unevictable(file->f_mapping);
1514         }
1515         if (!lock && (info->flags & VM_LOCKED) && user) {
1516                 user_shm_unlock(inode->i_size, user);
1517                 info->flags &= ~VM_LOCKED;
1518                 mapping_clear_unevictable(file->f_mapping);
1519                 scan_mapping_unevictable_pages(file->f_mapping);
1520         }
1521         retval = 0;
1522
1523 out_nomem:
1524         spin_unlock(&info->lock);
1525         return retval;
1526 }
1527
1528 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1529 {
1530         file_accessed(file);
1531         vma->vm_ops = &shmem_vm_ops;
1532         vma->vm_flags |= VM_CAN_NONLINEAR;
1533         return 0;
1534 }
1535
1536 static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
1537                                      int mode, dev_t dev, unsigned long flags)
1538 {
1539         struct inode *inode;
1540         struct shmem_inode_info *info;
1541         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1542
1543         if (shmem_reserve_inode(sb))
1544                 return NULL;
1545
1546         inode = new_inode(sb);
1547         if (inode) {
1548                 inode->i_ino = get_next_ino();
1549                 inode_init_owner(inode, dir, mode);
1550                 inode->i_blocks = 0;
1551                 inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1552                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1553                 inode->i_generation = get_seconds();
1554                 info = SHMEM_I(inode);
1555                 memset(info, 0, (char *)inode - (char *)info);
1556                 spin_lock_init(&info->lock);
1557                 info->flags = flags & VM_NORESERVE;
1558                 INIT_LIST_HEAD(&info->swaplist);
1559                 INIT_LIST_HEAD(&info->xattr_list);
1560                 cache_no_acl(inode);
1561
1562                 switch (mode & S_IFMT) {
1563                 default:
1564                         inode->i_op = &shmem_special_inode_operations;
1565                         init_special_inode(inode, mode, dev);
1566                         break;
1567                 case S_IFREG:
1568                         inode->i_mapping->a_ops = &shmem_aops;
1569                         inode->i_op = &shmem_inode_operations;
1570                         inode->i_fop = &shmem_file_operations;
1571                         mpol_shared_policy_init(&info->policy,
1572                                                  shmem_get_sbmpol(sbinfo));
1573                         break;
1574                 case S_IFDIR:
1575                         inc_nlink(inode);
1576                         /* Some things misbehave if size == 0 on a directory */
1577                         inode->i_size = 2 * BOGO_DIRENT_SIZE;
1578                         inode->i_op = &shmem_dir_inode_operations;
1579                         inode->i_fop = &simple_dir_operations;
1580                         break;
1581                 case S_IFLNK:
1582                         /*
1583                          * Must not load anything in the rbtree,
1584                          * mpol_free_shared_policy will not be called.
1585                          */
1586                         mpol_shared_policy_init(&info->policy, NULL);
1587                         break;
1588                 }
1589         } else
1590                 shmem_free_inode(sb);
1591         return inode;
1592 }
1593
1594 #ifdef CONFIG_TMPFS
1595 static const struct inode_operations shmem_symlink_inode_operations;
1596 static const struct inode_operations shmem_symlink_inline_operations;
1597
1598 static int
1599 shmem_write_begin(struct file *file, struct address_space *mapping,
1600                         loff_t pos, unsigned len, unsigned flags,
1601                         struct page **pagep, void **fsdata)
1602 {
1603         struct inode *inode = mapping->host;
1604         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1605         return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
1606 }
1607
1608 static int
1609 shmem_write_end(struct file *file, struct address_space *mapping,
1610                         loff_t pos, unsigned len, unsigned copied,
1611                         struct page *page, void *fsdata)
1612 {
1613         struct inode *inode = mapping->host;
1614
1615         if (pos + copied > inode->i_size)
1616                 i_size_write(inode, pos + copied);
1617
1618         set_page_dirty(page);
1619         unlock_page(page);
1620         page_cache_release(page);
1621
1622         return copied;
1623 }
1624
1625 static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1626 {
1627         struct inode *inode = filp->f_path.dentry->d_inode;
1628         struct address_space *mapping = inode->i_mapping;
1629         unsigned long index, offset;
1630         enum sgp_type sgp = SGP_READ;
1631
1632         /*
1633          * Might this read be for a stacking filesystem?  Then when reading
1634          * holes of a sparse file, we actually need to allocate those pages,
1635          * and even mark them dirty, so it cannot exceed the max_blocks limit.
1636          */
1637         if (segment_eq(get_fs(), KERNEL_DS))
1638                 sgp = SGP_DIRTY;
1639
1640         index = *ppos >> PAGE_CACHE_SHIFT;
1641         offset = *ppos & ~PAGE_CACHE_MASK;
1642
1643         for (;;) {
1644                 struct page *page = NULL;
1645                 unsigned long end_index, nr, ret;
1646                 loff_t i_size = i_size_read(inode);
1647
1648                 end_index = i_size >> PAGE_CACHE_SHIFT;
1649                 if (index > end_index)
1650                         break;
1651                 if (index == end_index) {
1652                         nr = i_size & ~PAGE_CACHE_MASK;
1653                         if (nr <= offset)
1654                                 break;
1655                 }
1656
1657                 desc->error = shmem_getpage(inode, index, &page, sgp, NULL);
1658                 if (desc->error) {
1659                         if (desc->error == -EINVAL)
1660                                 desc->error = 0;
1661                         break;
1662                 }
1663                 if (page)
1664                         unlock_page(page);
1665
1666                 /*
1667                  * We must evaluate after, since reads (unlike writes)
1668                  * are called without i_mutex protection against truncate
1669                  */
1670                 nr = PAGE_CACHE_SIZE;
1671                 i_size = i_size_read(inode);
1672                 end_index = i_size >> PAGE_CACHE_SHIFT;
1673                 if (index == end_index) {
1674                         nr = i_size & ~PAGE_CACHE_MASK;
1675                         if (nr <= offset) {
1676                                 if (page)
1677                                         page_cache_release(page);
1678                                 break;
1679                         }
1680                 }
1681                 nr -= offset;
1682
1683                 if (page) {
1684                         /*
1685                          * If users can be writing to this page using arbitrary
1686                          * virtual addresses, take care about potential aliasing
1687                          * before reading the page on the kernel side.
1688                          */
1689                         if (mapping_writably_mapped(mapping))
1690                                 flush_dcache_page(page);
1691                         /*
1692                          * Mark the page accessed if we read the beginning.
1693                          */
1694                         if (!offset)
1695                                 mark_page_accessed(page);
1696                 } else {
1697                         page = ZERO_PAGE(0);
1698                         page_cache_get(page);
1699                 }
1700
1701                 /*
1702                  * Ok, we have the page, and it's up-to-date, so
1703                  * now we can copy it to user space...
1704                  *
1705                  * The actor routine returns how many bytes were actually used..
1706                  * NOTE! This may not be the same as how much of a user buffer
1707                  * we filled up (we may be padding etc), so we can only update
1708                  * "pos" here (the actor routine has to update the user buffer
1709                  * pointers and the remaining count).
1710                  */
1711                 ret = actor(desc, page, offset, nr);
1712                 offset += ret;
1713                 index += offset >> PAGE_CACHE_SHIFT;
1714                 offset &= ~PAGE_CACHE_MASK;
1715
1716                 page_cache_release(page);
1717                 if (ret != nr || !desc->count)
1718                         break;
1719
1720                 cond_resched();
1721         }
1722
1723         *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1724         file_accessed(filp);
1725 }
1726
1727 static ssize_t shmem_file_aio_read(struct kiocb *iocb,
1728                 const struct iovec *iov, unsigned long nr_segs, loff_t pos)
1729 {
1730         struct file *filp = iocb->ki_filp;
1731         ssize_t retval;
1732         unsigned long seg;
1733         size_t count;
1734         loff_t *ppos = &iocb->ki_pos;
1735
1736         retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1737         if (retval)
1738                 return retval;
1739
1740         for (seg = 0; seg < nr_segs; seg++) {
1741                 read_descriptor_t desc;
1742
1743                 desc.written = 0;
1744                 desc.arg.buf = iov[seg].iov_base;
1745                 desc.count = iov[seg].iov_len;
1746                 if (desc.count == 0)
1747                         continue;
1748                 desc.error = 0;
1749                 do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1750                 retval += desc.written;
1751                 if (desc.error) {
1752                         retval = retval ?: desc.error;
1753                         break;
1754                 }
1755                 if (desc.count > 0)
1756                         break;
1757         }
1758         return retval;
1759 }
1760
1761 static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
1762                                 struct pipe_inode_info *pipe, size_t len,
1763                                 unsigned int flags)
1764 {
1765         struct address_space *mapping = in->f_mapping;
1766         struct inode *inode = mapping->host;
1767         unsigned int loff, nr_pages, req_pages;
1768         struct page *pages[PIPE_DEF_BUFFERS];
1769         struct partial_page partial[PIPE_DEF_BUFFERS];
1770         struct page *page;
1771         pgoff_t index, end_index;
1772         loff_t isize, left;
1773         int error, page_nr;
1774         struct splice_pipe_desc spd = {
1775                 .pages = pages,
1776                 .partial = partial,
1777                 .flags = flags,
1778                 .ops = &page_cache_pipe_buf_ops,
1779                 .spd_release = spd_release_page,
1780         };
1781
1782         isize = i_size_read(inode);
1783         if (unlikely(*ppos >= isize))
1784                 return 0;
1785
1786         left = isize - *ppos;
1787         if (unlikely(left < len))
1788                 len = left;
1789
1790         if (splice_grow_spd(pipe, &spd))
1791                 return -ENOMEM;
1792
1793         index = *ppos >> PAGE_CACHE_SHIFT;
1794         loff = *ppos & ~PAGE_CACHE_MASK;
1795         req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1796         nr_pages = min(req_pages, pipe->buffers);
1797
1798         spd.nr_pages = find_get_pages_contig(mapping, index,
1799                                                 nr_pages, spd.pages);
1800         index += spd.nr_pages;
1801         error = 0;
1802
1803         while (spd.nr_pages < nr_pages) {
1804                 error = shmem_getpage(inode, index, &page, SGP_CACHE, NULL);
1805                 if (error)
1806                         break;
1807                 unlock_page(page);
1808                 spd.pages[spd.nr_pages++] = page;
1809                 index++;
1810         }
1811
1812         index = *ppos >> PAGE_CACHE_SHIFT;
1813         nr_pages = spd.nr_pages;
1814         spd.nr_pages = 0;
1815
1816         for (page_nr = 0; page_nr < nr_pages; page_nr++) {
1817                 unsigned int this_len;
1818
1819                 if (!len)
1820                         break;
1821
1822                 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
1823                 page = spd.pages[page_nr];
1824
1825                 if (!PageUptodate(page) || page->mapping != mapping) {
1826                         error = shmem_getpage(inode, index, &page,
1827                                                         SGP_CACHE, NULL);
1828                         if (error)
1829                                 break;
1830                         unlock_page(page);
1831                         page_cache_release(spd.pages[page_nr]);
1832                         spd.pages[page_nr] = page;
1833                 }
1834
1835                 isize = i_size_read(inode);
1836                 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1837                 if (unlikely(!isize || index > end_index))
1838                         break;
1839
1840                 if (end_index == index) {
1841                         unsigned int plen;
1842
1843                         plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1844                         if (plen <= loff)
1845                                 break;
1846
1847                         this_len = min(this_len, plen - loff);
1848                         len = this_len;
1849                 }
1850
1851                 spd.partial[page_nr].offset = loff;
1852                 spd.partial[page_nr].len = this_len;
1853                 len -= this_len;
1854                 loff = 0;
1855                 spd.nr_pages++;
1856                 index++;
1857         }
1858
1859         while (page_nr < nr_pages)
1860                 page_cache_release(spd.pages[page_nr++]);
1861
1862         if (spd.nr_pages)
1863                 error = splice_to_pipe(pipe, &spd);
1864
1865         splice_shrink_spd(pipe, &spd);
1866
1867         if (error > 0) {
1868                 *ppos += error;
1869                 file_accessed(in);
1870         }
1871         return error;
1872 }
1873
1874 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1875 {
1876         struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1877
1878         buf->f_type = TMPFS_MAGIC;
1879         buf->f_bsize = PAGE_CACHE_SIZE;
1880         buf->f_namelen = NAME_MAX;
1881         if (sbinfo->max_blocks) {
1882                 buf->f_blocks = sbinfo->max_blocks;
1883                 buf->f_bavail = buf->f_bfree =
1884                                 sbinfo->max_blocks - percpu_counter_sum(&sbinfo->used_blocks);
1885         }
1886         if (sbinfo->max_inodes) {
1887                 buf->f_files = sbinfo->max_inodes;
1888                 buf->f_ffree = sbinfo->free_inodes;
1889         }
1890         /* else leave those fields 0 like simple_statfs */
1891         return 0;
1892 }
1893
1894 /*
1895  * File creation. Allocate an inode, and we're done..
1896  */
1897 static int
1898 shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
1899 {
1900         struct inode *inode;
1901         int error = -ENOSPC;
1902
1903         inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
1904         if (inode) {
1905                 error = security_inode_init_security(inode, dir,
1906                                                      &dentry->d_name, NULL,
1907                                                      NULL, NULL);
1908                 if (error) {
1909                         if (error != -EOPNOTSUPP) {
1910                                 iput(inode);
1911                                 return error;
1912                         }
1913                 }
1914 #ifdef CONFIG_TMPFS_POSIX_ACL
1915                 error = generic_acl_init(inode, dir);
1916                 if (error) {
1917                         iput(inode);
1918                         return error;
1919                 }
1920 #else
1921                 error = 0;
1922 #endif
1923                 dir->i_size += BOGO_DIRENT_SIZE;
1924                 dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1925                 d_instantiate(dentry, inode);
1926                 dget(dentry); /* Extra count - pin the dentry in core */
1927         }
1928         return error;
1929 }
1930
1931 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, int mode)
1932 {
1933         int error;
1934
1935         if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1936                 return error;
1937         inc_nlink(dir);
1938         return 0;
1939 }
1940
1941 static int shmem_create(struct inode *dir, struct dentry *dentry, int mode,
1942                 struct nameidata *nd)
1943 {
1944         return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1945 }
1946
1947 /*
1948  * Link a file..
1949  */
1950 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1951 {
1952         struct inode *inode = old_dentry->d_inode;
1953         int ret;
1954
1955         /*
1956          * No ordinary (disk based) filesystem counts links as inodes;
1957          * but each new link needs a new dentry, pinning lowmem, and
1958          * tmpfs dentries cannot be pruned until they are unlinked.
1959          */
1960         ret = shmem_reserve_inode(inode->i_sb);
1961         if (ret)
1962                 goto out;
1963
1964         dir->i_size += BOGO_DIRENT_SIZE;
1965         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1966         inc_nlink(inode);
1967         ihold(inode);   /* New dentry reference */
1968         dget(dentry);           /* Extra pinning count for the created dentry */
1969         d_instantiate(dentry, inode);
1970 out:
1971         return ret;
1972 }
1973
1974 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
1975 {
1976         struct inode *inode = dentry->d_inode;
1977
1978         if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
1979                 shmem_free_inode(inode->i_sb);
1980
1981         dir->i_size -= BOGO_DIRENT_SIZE;
1982         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1983         drop_nlink(inode);
1984         dput(dentry);   /* Undo the count from "create" - this does all the work */
1985         return 0;
1986 }
1987
1988 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
1989 {
1990         if (!simple_empty(dentry))
1991                 return -ENOTEMPTY;
1992
1993         drop_nlink(dentry->d_inode);
1994         drop_nlink(dir);
1995         return shmem_unlink(dir, dentry);
1996 }
1997
1998 /*
1999  * The VFS layer already does all the dentry stuff for rename,
2000  * we just have to decrement the usage count for the target if
2001  * it exists so that the VFS layer correctly free's it when it
2002  * gets overwritten.
2003  */
2004 static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
2005 {
2006         struct inode *inode = old_dentry->d_inode;
2007         int they_are_dirs = S_ISDIR(inode->i_mode);
2008
2009         if (!simple_empty(new_dentry))
2010                 return -ENOTEMPTY;
2011
2012         if (new_dentry->d_inode) {
2013                 (void) shmem_unlink(new_dir, new_dentry);
2014                 if (they_are_dirs)
2015                         drop_nlink(old_dir);
2016         } else if (they_are_dirs) {
2017                 drop_nlink(old_dir);
2018                 inc_nlink(new_dir);
2019         }
2020
2021         old_dir->i_size -= BOGO_DIRENT_SIZE;
2022         new_dir->i_size += BOGO_DIRENT_SIZE;
2023         old_dir->i_ctime = old_dir->i_mtime =
2024         new_dir->i_ctime = new_dir->i_mtime =
2025         inode->i_ctime = CURRENT_TIME;
2026         return 0;
2027 }
2028
2029 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
2030 {
2031         int error;
2032         int len;
2033         struct inode *inode;
2034         struct page *page;
2035         char *kaddr;
2036         struct shmem_inode_info *info;
2037
2038         len = strlen(symname) + 1;
2039         if (len > PAGE_CACHE_SIZE)
2040                 return -ENAMETOOLONG;
2041
2042         inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE);
2043         if (!inode)
2044                 return -ENOSPC;
2045
2046         error = security_inode_init_security(inode, dir, &dentry->d_name, NULL,
2047                                              NULL, NULL);
2048         if (error) {
2049                 if (error != -EOPNOTSUPP) {
2050                         iput(inode);
2051                         return error;
2052                 }
2053                 error = 0;
2054         }
2055
2056         info = SHMEM_I(inode);
2057         inode->i_size = len-1;
2058         if (len <= SHMEM_SYMLINK_INLINE_LEN) {
2059                 /* do it inline */
2060                 memcpy(info->inline_symlink, symname, len);
2061                 inode->i_op = &shmem_symlink_inline_operations;
2062         } else {
2063                 error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
2064                 if (error) {
2065                         iput(inode);
2066                         return error;
2067                 }
2068                 inode->i_mapping->a_ops = &shmem_aops;
2069                 inode->i_op = &shmem_symlink_inode_operations;
2070                 kaddr = kmap_atomic(page, KM_USER0);
2071                 memcpy(kaddr, symname, len);
2072                 kunmap_atomic(kaddr, KM_USER0);
2073                 set_page_dirty(page);
2074                 unlock_page(page);
2075                 page_cache_release(page);
2076         }
2077         dir->i_size += BOGO_DIRENT_SIZE;
2078         dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2079         d_instantiate(dentry, inode);
2080         dget(dentry);
2081         return 0;
2082 }
2083
2084 static void *shmem_follow_link_inline(struct dentry *dentry, struct nameidata *nd)
2085 {
2086         nd_set_link(nd, SHMEM_I(dentry->d_inode)->inline_symlink);
2087         return NULL;
2088 }
2089
2090 static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
2091 {
2092         struct page *page = NULL;
2093         int res = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
2094         nd_set_link(nd, res ? ERR_PTR(res) : kmap(page));
2095         if (page)
2096                 unlock_page(page);
2097         return page;
2098 }
2099
2100 static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
2101 {
2102         if (!IS_ERR(nd_get_link(nd))) {
2103                 struct page *page = cookie;
2104                 kunmap(page);
2105                 mark_page_accessed(page);
2106                 page_cache_release(page);
2107         }
2108 }
2109
2110 #ifdef CONFIG_TMPFS_XATTR
2111 /*
2112  * Superblocks without xattr inode operations may get some security.* xattr
2113  * support from the LSM "for free". As soon as we have any other xattrs
2114  * like ACLs, we also need to implement the security.* handlers at
2115  * filesystem level, though.
2116  */
2117
2118 static int shmem_xattr_get(struct dentry *dentry, const char *name,
2119                            void *buffer, size_t size)
2120 {
2121         struct shmem_inode_info *info;
2122         struct shmem_xattr *xattr;
2123         int ret = -ENODATA;
2124
2125         info = SHMEM_I(dentry->d_inode);
2126
2127         spin_lock(&info->lock);
2128         list_for_each_entry(xattr, &info->xattr_list, list) {
2129                 if (strcmp(name, xattr->name))
2130                         continue;
2131
2132                 ret = xattr->size;
2133                 if (buffer) {
2134                         if (size < xattr->size)
2135                                 ret = -ERANGE;
2136                         else
2137                                 memcpy(buffer, xattr->value, xattr->size);
2138                 }
2139                 break;
2140         }
2141         spin_unlock(&info->lock);
2142         return ret;
2143 }
2144
2145 static int shmem_xattr_set(struct dentry *dentry, const char *name,
2146                            const void *value, size_t size, int flags)
2147 {
2148         struct inode *inode = dentry->d_inode;
2149         struct shmem_inode_info *info = SHMEM_I(inode);
2150         struct shmem_xattr *xattr;
2151         struct shmem_xattr *new_xattr = NULL;
2152         size_t len;
2153         int err = 0;
2154
2155         /* value == NULL means remove */
2156         if (value) {
2157                 /* wrap around? */
2158                 len = sizeof(*new_xattr) + size;
2159                 if (len <= sizeof(*new_xattr))
2160                         return -ENOMEM;
2161
2162                 new_xattr = kmalloc(len, GFP_KERNEL);
2163                 if (!new_xattr)
2164                         return -ENOMEM;
2165
2166                 new_xattr->name = kstrdup(name, GFP_KERNEL);
2167                 if (!new_xattr->name) {
2168                         kfree(new_xattr);
2169                         return -ENOMEM;
2170                 }
2171
2172                 new_xattr->size = size;
2173                 memcpy(new_xattr->value, value, size);
2174         }
2175
2176         spin_lock(&info->lock);
2177         list_for_each_entry(xattr, &info->xattr_list, list) {
2178                 if (!strcmp(name, xattr->name)) {
2179                         if (flags & XATTR_CREATE) {
2180                                 xattr = new_xattr;
2181                                 err = -EEXIST;
2182                         } else if (new_xattr) {
2183                                 list_replace(&xattr->list, &new_xattr->list);
2184                         } else {
2185                                 list_del(&xattr->list);
2186                         }
2187                         goto out;
2188                 }
2189         }
2190         if (flags & XATTR_REPLACE) {
2191                 xattr = new_xattr;
2192                 err = -ENODATA;
2193         } else {
2194                 list_add(&new_xattr->list, &info->xattr_list);
2195                 xattr = NULL;
2196         }
2197 out:
2198         spin_unlock(&info->lock);
2199         if (xattr)
2200                 kfree(xattr->name);
2201         kfree(xattr);
2202         return err;
2203 }
2204
2205
2206 static const struct xattr_handler *shmem_xattr_handlers[] = {
2207 #ifdef CONFIG_TMPFS_POSIX_ACL
2208         &generic_acl_access_handler,
2209         &generic_acl_default_handler,
2210 #endif
2211         NULL
2212 };
2213
2214 static int shmem_xattr_validate(const char *name)
2215 {
2216         struct { const char *prefix; size_t len; } arr[] = {
2217                 { XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN },
2218                 { XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN }
2219         };
2220         int i;
2221
2222         for (i = 0; i < ARRAY_SIZE(arr); i++) {
2223                 size_t preflen = arr[i].len;
2224                 if (strncmp(name, arr[i].prefix, preflen) == 0) {
2225                         if (!name[preflen])
2226                                 return -EINVAL;
2227                         return 0;
2228                 }
2229         }
2230         return -EOPNOTSUPP;
2231 }
2232
2233 static ssize_t shmem_getxattr(struct dentry *dentry, const char *name,
2234                               void *buffer, size_t size)
2235 {
2236         int err;
2237
2238         /*
2239          * If this is a request for a synthetic attribute in the system.*
2240          * namespace use the generic infrastructure to resolve a handler
2241          * for it via sb->s_xattr.
2242          */
2243         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2244                 return generic_getxattr(dentry, name, buffer, size);
2245
2246         err = shmem_xattr_validate(name);
2247         if (err)
2248                 return err;
2249
2250         return shmem_xattr_get(dentry, name, buffer, size);
2251 }
2252
2253 static int shmem_setxattr(struct dentry *dentry, const char *name,
2254                           const void *value, size_t size, int flags)
2255 {
2256         int err;
2257
2258         /*
2259          * If this is a request for a synthetic attribute in the system.*
2260          * namespace use the generic infrastructure to resolve a handler
2261          * for it via sb->s_xattr.
2262          */
2263         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2264                 return generic_setxattr(dentry, name, value, size, flags);
2265
2266         err = shmem_xattr_validate(name);
2267         if (err)
2268                 return err;
2269
2270         if (size == 0)
2271                 value = "";  /* empty EA, do not remove */
2272
2273         return shmem_xattr_set(dentry, name, value, size, flags);
2274
2275 }
2276
2277 static int shmem_removexattr(struct dentry *dentry, const char *name)
2278 {
2279         int err;
2280
2281         /*
2282          * If this is a request for a synthetic attribute in the system.*
2283          * namespace use the generic infrastructure to resolve a handler
2284          * for it via sb->s_xattr.
2285          */
2286         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2287                 return generic_removexattr(dentry, name);
2288
2289         err = shmem_xattr_validate(name);
2290         if (err)
2291                 return err;
2292
2293         return shmem_xattr_set(dentry, name, NULL, 0, XATTR_REPLACE);
2294 }
2295
2296 static bool xattr_is_trusted(const char *name)
2297 {
2298         return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
2299 }
2300
2301 static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
2302 {
2303         bool trusted = capable(CAP_SYS_ADMIN);
2304         struct shmem_xattr *xattr;
2305         struct shmem_inode_info *info;
2306         size_t used = 0;
2307
2308         info = SHMEM_I(dentry->d_inode);
2309
2310         spin_lock(&info->lock);
2311         list_for_each_entry(xattr, &info->xattr_list, list) {
2312                 size_t len;
2313
2314                 /* skip "trusted." attributes for unprivileged callers */
2315                 if (!trusted && xattr_is_trusted(xattr->name))
2316                         continue;
2317
2318                 len = strlen(xattr->name) + 1;
2319                 used += len;
2320                 if (buffer) {
2321                         if (size < used) {
2322                                 used = -ERANGE;
2323                                 break;
2324                         }
2325                         memcpy(buffer, xattr->name, len);
2326                         buffer += len;
2327                 }
2328         }
2329         spin_unlock(&info->lock);
2330
2331         return used;
2332 }
2333 #endif /* CONFIG_TMPFS_XATTR */
2334
2335 static const struct inode_operations shmem_symlink_inline_operations = {
2336         .readlink       = generic_readlink,
2337         .follow_link    = shmem_follow_link_inline,
2338 #ifdef CONFIG_TMPFS_XATTR
2339         .setxattr       = shmem_setxattr,
2340         .getxattr       = shmem_getxattr,
2341         .listxattr      = shmem_listxattr,
2342         .removexattr    = shmem_removexattr,
2343 #endif
2344 };
2345
2346 static const struct inode_operations shmem_symlink_inode_operations = {
2347         .readlink       = generic_readlink,
2348         .follow_link    = shmem_follow_link,
2349         .put_link       = shmem_put_link,
2350 #ifdef CONFIG_TMPFS_XATTR
2351         .setxattr       = shmem_setxattr,
2352         .getxattr       = shmem_getxattr,
2353         .listxattr      = shmem_listxattr,
2354         .removexattr    = shmem_removexattr,
2355 #endif
2356 };
2357
2358 static struct dentry *shmem_get_parent(struct dentry *child)
2359 {
2360         return ERR_PTR(-ESTALE);
2361 }
2362
2363 static int shmem_match(struct inode *ino, void *vfh)
2364 {
2365         __u32 *fh = vfh;
2366         __u64 inum = fh[2];
2367         inum = (inum << 32) | fh[1];
2368         return ino->i_ino == inum && fh[0] == ino->i_generation;
2369 }
2370
2371 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
2372                 struct fid *fid, int fh_len, int fh_type)
2373 {
2374         struct inode *inode;
2375         struct dentry *dentry = NULL;
2376         u64 inum = fid->raw[2];
2377         inum = (inum << 32) | fid->raw[1];
2378
2379         if (fh_len < 3)
2380                 return NULL;
2381
2382         inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
2383                         shmem_match, fid->raw);
2384         if (inode) {
2385                 dentry = d_find_alias(inode);
2386                 iput(inode);
2387         }
2388
2389         return dentry;
2390 }
2391
2392 static int shmem_encode_fh(struct dentry *dentry, __u32 *fh, int *len,
2393                                 int connectable)
2394 {
2395         struct inode *inode = dentry->d_inode;
2396
2397         if (*len < 3) {
2398                 *len = 3;
2399                 return 255;
2400         }
2401
2402         if (inode_unhashed(inode)) {
2403                 /* Unfortunately insert_inode_hash is not idempotent,
2404                  * so as we hash inodes here rather than at creation
2405                  * time, we need a lock to ensure we only try
2406                  * to do it once
2407                  */
2408                 static DEFINE_SPINLOCK(lock);
2409                 spin_lock(&lock);
2410                 if (inode_unhashed(inode))
2411                         __insert_inode_hash(inode,
2412                                             inode->i_ino + inode->i_generation);
2413                 spin_unlock(&lock);
2414         }
2415
2416         fh[0] = inode->i_generation;
2417         fh[1] = inode->i_ino;
2418         fh[2] = ((__u64)inode->i_ino) >> 32;
2419
2420         *len = 3;
2421         return 1;
2422 }
2423
2424 static const struct export_operations shmem_export_ops = {
2425         .get_parent     = shmem_get_parent,
2426         .encode_fh      = shmem_encode_fh,
2427         .fh_to_dentry   = shmem_fh_to_dentry,
2428 };
2429
2430 static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
2431                                bool remount)
2432 {
2433         char *this_char, *value, *rest;
2434
2435         while (options != NULL) {
2436                 this_char = options;
2437                 for (;;) {
2438                         /*
2439                          * NUL-terminate this option: unfortunately,
2440                          * mount options form a comma-separated list,
2441                          * but mpol's nodelist may also contain commas.
2442                          */
2443                         options = strchr(options, ',');
2444                         if (options == NULL)
2445                                 break;
2446                         options++;
2447                         if (!isdigit(*options)) {
2448                                 options[-1] = '\0';
2449                                 break;
2450                         }
2451                 }
2452                 if (!*this_char)
2453                         continue;
2454                 if ((value = strchr(this_char,'=')) != NULL) {
2455                         *value++ = 0;
2456                 } else {
2457                         printk(KERN_ERR
2458                             "tmpfs: No value for mount option '%s'\n",
2459                             this_char);
2460                         return 1;
2461                 }
2462
2463                 if (!strcmp(this_char,"size")) {
2464                         unsigned long long size;
2465                         size = memparse(value,&rest);
2466                         if (*rest == '%') {
2467                                 size <<= PAGE_SHIFT;
2468                                 size *= totalram_pages;
2469                                 do_div(size, 100);
2470                                 rest++;
2471                         }
2472                         if (*rest)
2473                                 goto bad_val;
2474                         sbinfo->max_blocks =
2475                                 DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
2476                 } else if (!strcmp(this_char,"nr_blocks")) {
2477                         sbinfo->max_blocks = memparse(value, &rest);
2478                         if (*rest)
2479                                 goto bad_val;
2480                 } else if (!strcmp(this_char,"nr_inodes")) {
2481                         sbinfo->max_inodes = memparse(value, &rest);
2482                         if (*rest)
2483                                 goto bad_val;
2484                 } else if (!strcmp(this_char,"mode")) {
2485                         if (remount)
2486                                 continue;
2487                         sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
2488                         if (*rest)
2489                                 goto bad_val;
2490                 } else if (!strcmp(this_char,"uid")) {
2491                         if (remount)
2492                                 continue;
2493                         sbinfo->uid = simple_strtoul(value, &rest, 0);
2494                         if (*rest)
2495                                 goto bad_val;
2496                 } else if (!strcmp(this_char,"gid")) {
2497                         if (remount)
2498                                 continue;
2499                         sbinfo->gid = simple_strtoul(value, &rest, 0);
2500                         if (*rest)
2501                                 goto bad_val;
2502                 } else if (!strcmp(this_char,"mpol")) {
2503                         if (mpol_parse_str(value, &sbinfo->mpol, 1))
2504                                 goto bad_val;
2505                 } else {
2506                         printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2507                                this_char);
2508                         return 1;
2509                 }
2510         }
2511         return 0;
2512
2513 bad_val:
2514         printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2515                value, this_char);
2516         return 1;
2517
2518 }
2519
2520 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2521 {
2522         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2523         struct shmem_sb_info config = *sbinfo;
2524         unsigned long inodes;
2525         int error = -EINVAL;
2526
2527         if (shmem_parse_options(data, &config, true))
2528                 return error;
2529
2530         spin_lock(&sbinfo->stat_lock);
2531         inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2532         if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0)
2533                 goto out;
2534         if (config.max_inodes < inodes)
2535                 goto out;
2536         /*
2537          * Those tests also disallow limited->unlimited while any are in
2538          * use, so i_blocks will always be zero when max_blocks is zero;
2539          * but we must separately disallow unlimited->limited, because
2540          * in that case we have no record of how much is already in use.
2541          */
2542         if (config.max_blocks && !sbinfo->max_blocks)
2543                 goto out;
2544         if (config.max_inodes && !sbinfo->max_inodes)
2545                 goto out;
2546
2547         error = 0;
2548         sbinfo->max_blocks  = config.max_blocks;
2549         sbinfo->max_inodes  = config.max_inodes;
2550         sbinfo->free_inodes = config.max_inodes - inodes;
2551
2552         mpol_put(sbinfo->mpol);
2553         sbinfo->mpol        = config.mpol;      /* transfers initial ref */
2554 out:
2555         spin_unlock(&sbinfo->stat_lock);
2556         return error;
2557 }
2558
2559 static int shmem_show_options(struct seq_file *seq, struct vfsmount *vfs)
2560 {
2561         struct shmem_sb_info *sbinfo = SHMEM_SB(vfs->mnt_sb);
2562
2563         if (sbinfo->max_blocks != shmem_default_max_blocks())
2564                 seq_printf(seq, ",size=%luk",
2565                         sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
2566         if (sbinfo->max_inodes != shmem_default_max_inodes())
2567                 seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
2568         if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
2569                 seq_printf(seq, ",mode=%03o", sbinfo->mode);
2570         if (sbinfo->uid != 0)
2571                 seq_printf(seq, ",uid=%u", sbinfo->uid);
2572         if (sbinfo->gid != 0)
2573                 seq_printf(seq, ",gid=%u", sbinfo->gid);
2574         shmem_show_mpol(seq, sbinfo->mpol);
2575         return 0;
2576 }
2577 #endif /* CONFIG_TMPFS */
2578
2579 static void shmem_put_super(struct super_block *sb)
2580 {
2581         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2582
2583         percpu_counter_destroy(&sbinfo->used_blocks);
2584         kfree(sbinfo);
2585         sb->s_fs_info = NULL;
2586 }
2587
2588 int shmem_fill_super(struct super_block *sb, void *data, int silent)
2589 {
2590         struct inode *inode;
2591         struct dentry *root;
2592         struct shmem_sb_info *sbinfo;
2593         int err = -ENOMEM;
2594
2595         /* Round up to L1_CACHE_BYTES to resist false sharing */
2596         sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
2597                                 L1_CACHE_BYTES), GFP_KERNEL);
2598         if (!sbinfo)
2599                 return -ENOMEM;
2600
2601         sbinfo->mode = S_IRWXUGO | S_ISVTX;
2602         sbinfo->uid = current_fsuid();
2603         sbinfo->gid = current_fsgid();
2604         sb->s_fs_info = sbinfo;
2605
2606 #ifdef CONFIG_TMPFS
2607         /*
2608          * Per default we only allow half of the physical ram per
2609          * tmpfs instance, limiting inodes to one per page of lowmem;
2610          * but the internal instance is left unlimited.
2611          */
2612         if (!(sb->s_flags & MS_NOUSER)) {
2613                 sbinfo->max_blocks = shmem_default_max_blocks();
2614                 sbinfo->max_inodes = shmem_default_max_inodes();
2615                 if (shmem_parse_options(data, sbinfo, false)) {
2616                         err = -EINVAL;
2617                         goto failed;
2618                 }
2619         }
2620         sb->s_export_op = &shmem_export_ops;
2621 #else
2622         sb->s_flags |= MS_NOUSER;
2623 #endif
2624
2625         spin_lock_init(&sbinfo->stat_lock);
2626         if (percpu_counter_init(&sbinfo->used_blocks, 0))
2627                 goto failed;
2628         sbinfo->free_inodes = sbinfo->max_inodes;
2629
2630         sb->s_maxbytes = SHMEM_MAX_BYTES;
2631         sb->s_blocksize = PAGE_CACHE_SIZE;
2632         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2633         sb->s_magic = TMPFS_MAGIC;
2634         sb->s_op = &shmem_ops;
2635         sb->s_time_gran = 1;
2636 #ifdef CONFIG_TMPFS_XATTR
2637         sb->s_xattr = shmem_xattr_handlers;
2638 #endif
2639 #ifdef CONFIG_TMPFS_POSIX_ACL
2640         sb->s_flags |= MS_POSIXACL;
2641 #endif
2642
2643         inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
2644         if (!inode)
2645                 goto failed;
2646         inode->i_uid = sbinfo->uid;
2647         inode->i_gid = sbinfo->gid;
2648         root = d_alloc_root(inode);
2649         if (!root)
2650                 goto failed_iput;
2651         sb->s_root = root;
2652         return 0;
2653
2654 failed_iput:
2655         iput(inode);
2656 failed:
2657         shmem_put_super(sb);
2658         return err;
2659 }
2660
2661 static struct kmem_cache *shmem_inode_cachep;
2662
2663 static struct inode *shmem_alloc_inode(struct super_block *sb)
2664 {
2665         struct shmem_inode_info *p;
2666         p = (struct shmem_inode_info *)kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2667         if (!p)
2668                 return NULL;
2669         return &p->vfs_inode;
2670 }
2671
2672 static void shmem_i_callback(struct rcu_head *head)
2673 {
2674         struct inode *inode = container_of(head, struct inode, i_rcu);
2675         INIT_LIST_HEAD(&inode->i_dentry);
2676         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2677 }
2678
2679 static void shmem_destroy_inode(struct inode *inode)
2680 {
2681         if ((inode->i_mode & S_IFMT) == S_IFREG) {
2682                 /* only struct inode is valid if it's an inline symlink */
2683                 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2684         }
2685         call_rcu(&inode->i_rcu, shmem_i_callback);
2686 }
2687
2688 static void init_once(void *foo)
2689 {
2690         struct shmem_inode_info *p = (struct shmem_inode_info *) foo;
2691
2692         inode_init_once(&p->vfs_inode);
2693 }
2694
2695 static int init_inodecache(void)
2696 {
2697         shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2698                                 sizeof(struct shmem_inode_info),
2699                                 0, SLAB_PANIC, init_once);
2700         return 0;
2701 }
2702
2703 static void destroy_inodecache(void)
2704 {
2705         kmem_cache_destroy(shmem_inode_cachep);
2706 }
2707
2708 static const struct address_space_operations shmem_aops = {
2709         .writepage      = shmem_writepage,
2710         .set_page_dirty = __set_page_dirty_no_writeback,
2711 #ifdef CONFIG_TMPFS
2712         .write_begin    = shmem_write_begin,
2713         .write_end      = shmem_write_end,
2714 #endif
2715         .migratepage    = migrate_page,
2716         .error_remove_page = generic_error_remove_page,
2717 };
2718
2719 static const struct file_operations shmem_file_operations = {
2720         .mmap           = shmem_mmap,
2721 #ifdef CONFIG_TMPFS
2722         .llseek         = generic_file_llseek,
2723         .read           = do_sync_read,
2724         .write          = do_sync_write,
2725         .aio_read       = shmem_file_aio_read,
2726         .aio_write      = generic_file_aio_write,
2727         .fsync          = noop_fsync,
2728         .splice_read    = shmem_file_splice_read,
2729         .splice_write   = generic_file_splice_write,
2730 #endif
2731 };
2732
2733 static const struct inode_operations shmem_inode_operations = {
2734         .setattr        = shmem_setattr,
2735         .truncate_range = shmem_truncate_range,
2736 #ifdef CONFIG_TMPFS_XATTR
2737         .setxattr       = shmem_setxattr,
2738         .getxattr       = shmem_getxattr,
2739         .listxattr      = shmem_listxattr,
2740         .removexattr    = shmem_removexattr,
2741 #endif
2742 #ifdef CONFIG_TMPFS_POSIX_ACL
2743         .check_acl      = generic_check_acl,
2744 #endif
2745
2746 };
2747
2748 static const struct inode_operations shmem_dir_inode_operations = {
2749 #ifdef CONFIG_TMPFS
2750         .create         = shmem_create,
2751         .lookup         = simple_lookup,
2752         .link           = shmem_link,
2753         .unlink         = shmem_unlink,
2754         .symlink        = shmem_symlink,
2755         .mkdir          = shmem_mkdir,
2756         .rmdir          = shmem_rmdir,
2757         .mknod          = shmem_mknod,
2758         .rename         = shmem_rename,
2759 #endif
2760 #ifdef CONFIG_TMPFS_XATTR
2761         .setxattr       = shmem_setxattr,
2762         .getxattr       = shmem_getxattr,
2763         .listxattr      = shmem_listxattr,
2764         .removexattr    = shmem_removexattr,
2765 #endif
2766 #ifdef CONFIG_TMPFS_POSIX_ACL
2767         .setattr        = shmem_setattr,
2768         .check_acl      = generic_check_acl,
2769 #endif
2770 };
2771
2772 static const struct inode_operations shmem_special_inode_operations = {
2773 #ifdef CONFIG_TMPFS_XATTR
2774         .setxattr       = shmem_setxattr,
2775         .getxattr       = shmem_getxattr,
2776         .listxattr      = shmem_listxattr,
2777         .removexattr    = shmem_removexattr,
2778 #endif
2779 #ifdef CONFIG_TMPFS_POSIX_ACL
2780         .setattr        = shmem_setattr,
2781         .check_acl      = generic_check_acl,
2782 #endif
2783 };
2784
2785 static const struct super_operations shmem_ops = {
2786         .alloc_inode    = shmem_alloc_inode,
2787         .destroy_inode  = shmem_destroy_inode,
2788 #ifdef CONFIG_TMPFS
2789         .statfs         = shmem_statfs,
2790         .remount_fs     = shmem_remount_fs,
2791         .show_options   = shmem_show_options,
2792 #endif
2793         .evict_inode    = shmem_evict_inode,
2794         .drop_inode     = generic_delete_inode,
2795         .put_super      = shmem_put_super,
2796 };
2797
2798 static const struct vm_operations_struct shmem_vm_ops = {
2799         .fault          = shmem_fault,
2800 #ifdef CONFIG_NUMA
2801         .set_policy     = shmem_set_policy,
2802         .get_policy     = shmem_get_policy,
2803 #endif
2804 };
2805
2806
2807 static struct dentry *shmem_mount(struct file_system_type *fs_type,
2808         int flags, const char *dev_name, void *data)
2809 {
2810         return mount_nodev(fs_type, flags, data, shmem_fill_super);
2811 }
2812
2813 static struct file_system_type tmpfs_fs_type = {
2814         .owner          = THIS_MODULE,
2815         .name           = "tmpfs",
2816         .mount          = shmem_mount,
2817         .kill_sb        = kill_litter_super,
2818 };
2819
2820 int __init init_tmpfs(void)
2821 {
2822         int error;
2823
2824         error = bdi_init(&shmem_backing_dev_info);
2825         if (error)
2826                 goto out4;
2827
2828         error = init_inodecache();
2829         if (error)
2830                 goto out3;
2831
2832         error = register_filesystem(&tmpfs_fs_type);
2833         if (error) {
2834                 printk(KERN_ERR "Could not register tmpfs\n");
2835                 goto out2;
2836         }
2837
2838         shm_mnt = vfs_kern_mount(&tmpfs_fs_type, MS_NOUSER,
2839                                 tmpfs_fs_type.name, NULL);
2840         if (IS_ERR(shm_mnt)) {
2841                 error = PTR_ERR(shm_mnt);
2842                 printk(KERN_ERR "Could not kern_mount tmpfs\n");
2843                 goto out1;
2844         }
2845         return 0;
2846
2847 out1:
2848         unregister_filesystem(&tmpfs_fs_type);
2849 out2:
2850         destroy_inodecache();
2851 out3:
2852         bdi_destroy(&shmem_backing_dev_info);
2853 out4:
2854         shm_mnt = ERR_PTR(error);
2855         return error;
2856 }
2857
2858 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2859 /**
2860  * mem_cgroup_get_shmem_target - find a page or entry assigned to the shmem file
2861  * @inode: the inode to be searched
2862  * @pgoff: the offset to be searched
2863  * @pagep: the pointer for the found page to be stored
2864  * @ent: the pointer for the found swap entry to be stored
2865  *
2866  * If a page is found, refcount of it is incremented. Callers should handle
2867  * these refcount.
2868  */
2869 void mem_cgroup_get_shmem_target(struct inode *inode, pgoff_t pgoff,
2870                                         struct page **pagep, swp_entry_t *ent)
2871 {
2872         swp_entry_t entry = { .val = 0 }, *ptr;
2873         struct page *page = NULL;
2874         struct shmem_inode_info *info = SHMEM_I(inode);
2875
2876         if ((pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
2877                 goto out;
2878
2879         spin_lock(&info->lock);
2880         ptr = shmem_swp_entry(info, pgoff, NULL);
2881 #ifdef CONFIG_SWAP
2882         if (ptr && ptr->val) {
2883                 entry.val = ptr->val;
2884                 page = find_get_page(&swapper_space, entry.val);
2885         } else
2886 #endif
2887                 page = find_get_page(inode->i_mapping, pgoff);
2888         if (ptr)
2889                 shmem_swp_unmap(ptr);
2890         spin_unlock(&info->lock);
2891 out:
2892         *pagep = page;
2893         *ent = entry;
2894 }
2895 #endif
2896
2897 #else /* !CONFIG_SHMEM */
2898
2899 /*
2900  * tiny-shmem: simple shmemfs and tmpfs using ramfs code
2901  *
2902  * This is intended for small system where the benefits of the full
2903  * shmem code (swap-backed and resource-limited) are outweighed by
2904  * their complexity. On systems without swap this code should be
2905  * effectively equivalent, but much lighter weight.
2906  */
2907
2908 #include <linux/ramfs.h>
2909
2910 static struct file_system_type tmpfs_fs_type = {
2911         .name           = "tmpfs",
2912         .mount          = ramfs_mount,
2913         .kill_sb        = kill_litter_super,
2914 };
2915
2916 int __init init_tmpfs(void)
2917 {
2918         BUG_ON(register_filesystem(&tmpfs_fs_type) != 0);
2919
2920         shm_mnt = kern_mount(&tmpfs_fs_type);
2921         BUG_ON(IS_ERR(shm_mnt));
2922
2923         return 0;
2924 }
2925
2926 int shmem_unuse(swp_entry_t entry, struct page *page)
2927 {
2928         return 0;
2929 }
2930
2931 int shmem_lock(struct file *file, int lock, struct user_struct *user)
2932 {
2933         return 0;
2934 }
2935
2936 void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end)
2937 {
2938         truncate_inode_pages_range(inode->i_mapping, start, end);
2939 }
2940 EXPORT_SYMBOL_GPL(shmem_truncate_range);
2941
2942 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2943 /**
2944  * mem_cgroup_get_shmem_target - find a page or entry assigned to the shmem file
2945  * @inode: the inode to be searched
2946  * @pgoff: the offset to be searched
2947  * @pagep: the pointer for the found page to be stored
2948  * @ent: the pointer for the found swap entry to be stored
2949  *
2950  * If a page is found, refcount of it is incremented. Callers should handle
2951  * these refcount.
2952  */
2953 void mem_cgroup_get_shmem_target(struct inode *inode, pgoff_t pgoff,
2954                                         struct page **pagep, swp_entry_t *ent)
2955 {
2956         struct page *page = NULL;
2957
2958         if ((pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
2959                 goto out;
2960         page = find_get_page(inode->i_mapping, pgoff);
2961 out:
2962         *pagep = page;
2963         *ent = (swp_entry_t){ .val = 0 };
2964 }
2965 #endif
2966
2967 #define shmem_vm_ops                            generic_file_vm_ops
2968 #define shmem_file_operations                   ramfs_file_operations
2969 #define shmem_get_inode(sb, dir, mode, dev, flags)      ramfs_get_inode(sb, dir, mode, dev)
2970 #define shmem_acct_size(flags, size)            0
2971 #define shmem_unacct_size(flags, size)          do {} while (0)
2972 #define SHMEM_MAX_BYTES                         MAX_LFS_FILESIZE
2973
2974 #endif /* CONFIG_SHMEM */
2975
2976 /* common code */
2977
2978 /**
2979  * shmem_file_setup - get an unlinked file living in tmpfs
2980  * @name: name for dentry (to be seen in /proc/<pid>/maps
2981  * @size: size to be set for the file
2982  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
2983  */
2984 struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
2985 {
2986         int error;
2987         struct file *file;
2988         struct inode *inode;
2989         struct path path;
2990         struct dentry *root;
2991         struct qstr this;
2992
2993         if (IS_ERR(shm_mnt))
2994                 return (void *)shm_mnt;
2995
2996         if (size < 0 || size > SHMEM_MAX_BYTES)
2997                 return ERR_PTR(-EINVAL);
2998
2999         if (shmem_acct_size(flags, size))
3000                 return ERR_PTR(-ENOMEM);
3001
3002         error = -ENOMEM;
3003         this.name = name;
3004         this.len = strlen(name);
3005         this.hash = 0; /* will go */
3006         root = shm_mnt->mnt_root;
3007         path.dentry = d_alloc(root, &this);
3008         if (!path.dentry)
3009                 goto put_memory;
3010         path.mnt = mntget(shm_mnt);
3011
3012         error = -ENOSPC;
3013         inode = shmem_get_inode(root->d_sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
3014         if (!inode)
3015                 goto put_dentry;
3016
3017         d_instantiate(path.dentry, inode);
3018         inode->i_size = size;
3019         inode->i_nlink = 0;     /* It is unlinked */
3020 #ifndef CONFIG_MMU
3021         error = ramfs_nommu_expand_for_mapping(inode, size);
3022         if (error)
3023                 goto put_dentry;
3024 #endif
3025
3026         error = -ENFILE;
3027         file = alloc_file(&path, FMODE_WRITE | FMODE_READ,
3028                   &shmem_file_operations);
3029         if (!file)
3030                 goto put_dentry;
3031
3032         return file;
3033
3034 put_dentry:
3035         path_put(&path);
3036 put_memory:
3037         shmem_unacct_size(flags, size);
3038         return ERR_PTR(error);
3039 }
3040 EXPORT_SYMBOL_GPL(shmem_file_setup);
3041
3042 /**
3043  * shmem_zero_setup - setup a shared anonymous mapping
3044  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
3045  */
3046 int shmem_zero_setup(struct vm_area_struct *vma)
3047 {
3048         struct file *file;
3049         loff_t size = vma->vm_end - vma->vm_start;
3050
3051         file = shmem_file_setup("dev/zero", size, vma->vm_flags);
3052         if (IS_ERR(file))
3053                 return PTR_ERR(file);
3054
3055         if (vma->vm_file)
3056                 fput(vma->vm_file);
3057         vma->vm_file = file;
3058         vma->vm_ops = &shmem_vm_ops;
3059         vma->vm_flags |= VM_CAN_NONLINEAR;
3060         return 0;
3061 }
3062
3063 /**
3064  * shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags.
3065  * @mapping:    the page's address_space
3066  * @index:      the page index
3067  * @gfp:        the page allocator flags to use if allocating
3068  *
3069  * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)",
3070  * with any new page allocations done using the specified allocation flags.
3071  * But read_cache_page_gfp() uses the ->readpage() method: which does not
3072  * suit tmpfs, since it may have pages in swapcache, and needs to find those
3073  * for itself; although drivers/gpu/drm i915 and ttm rely upon this support.
3074  *
3075  * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in
3076  * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily.
3077  */
3078 struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
3079                                          pgoff_t index, gfp_t gfp)
3080 {
3081 #ifdef CONFIG_SHMEM
3082         struct inode *inode = mapping->host;
3083         struct page *page;
3084         int error;
3085
3086         BUG_ON(mapping->a_ops != &shmem_aops);
3087         error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE, gfp, NULL);
3088         if (error)
3089                 page = ERR_PTR(error);
3090         else
3091                 unlock_page(page);
3092         return page;
3093 #else
3094         /*
3095          * The tiny !SHMEM case uses ramfs without swap
3096          */
3097         return read_cache_page_gfp(mapping, index, gfp);
3098 #endif
3099 }
3100 EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);