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tmpfs: fix shared mempolicy leak
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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) 2002-2011 Hugh Dickins.
10  * Copyright (C) 2011 Google Inc.
11  * Copyright (C) 2002-2005 VERITAS Software Corporation.
12  * Copyright (C) 2004 Andi Kleen, SuSE Labs
13  *
14  * Extended attribute support for tmpfs:
15  * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
16  * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
17  *
18  * tiny-shmem:
19  * Copyright (c) 2004, 2008 Matt Mackall <mpm@selenic.com>
20  *
21  * This file is released under the GPL.
22  */
23
24 #include <linux/fs.h>
25 #include <linux/init.h>
26 #include <linux/vfs.h>
27 #include <linux/mount.h>
28 #include <linux/pagemap.h>
29 #include <linux/file.h>
30 #include <linux/mm.h>
31 #include <linux/export.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/pagevec.h>
55 #include <linux/percpu_counter.h>
56 #include <linux/falloc.h>
57 #include <linux/splice.h>
58 #include <linux/security.h>
59 #include <linux/swapops.h>
60 #include <linux/mempolicy.h>
61 #include <linux/namei.h>
62 #include <linux/ctype.h>
63 #include <linux/migrate.h>
64 #include <linux/highmem.h>
65 #include <linux/seq_file.h>
66 #include <linux/magic.h>
67
68 #include <asm/uaccess.h>
69 #include <asm/pgtable.h>
70
71 #define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
72 #define VM_ACCT(size)    (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
73
74 /* Pretend that each entry is of this size in directory's i_size */
75 #define BOGO_DIRENT_SIZE 20
76
77 /* Symlink up to this size is kmalloc'ed instead of using a swappable page */
78 #define SHORT_SYMLINK_LEN 128
79
80 /*
81  * shmem_fallocate and shmem_writepage communicate via inode->i_private
82  * (with i_mutex making sure that it has only one user at a time):
83  * we would prefer not to enlarge the shmem inode just for that.
84  */
85 struct shmem_falloc {
86         pgoff_t start;          /* start of range currently being fallocated */
87         pgoff_t next;           /* the next page offset to be fallocated */
88         pgoff_t nr_falloced;    /* how many new pages have been fallocated */
89         pgoff_t nr_unswapped;   /* how often writepage refused to swap out */
90 };
91
92 /* Flag allocation requirements to shmem_getpage */
93 enum sgp_type {
94         SGP_READ,       /* don't exceed i_size, don't allocate page */
95         SGP_CACHE,      /* don't exceed i_size, may allocate page */
96         SGP_DIRTY,      /* like SGP_CACHE, but set new page dirty */
97         SGP_WRITE,      /* may exceed i_size, may allocate !Uptodate page */
98         SGP_FALLOC,     /* like SGP_WRITE, but make existing page Uptodate */
99 };
100
101 #ifdef CONFIG_TMPFS
102 static unsigned long shmem_default_max_blocks(void)
103 {
104         return totalram_pages / 2;
105 }
106
107 static unsigned long shmem_default_max_inodes(void)
108 {
109         return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
110 }
111 #endif
112
113 static bool shmem_should_replace_page(struct page *page, gfp_t gfp);
114 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
115                                 struct shmem_inode_info *info, pgoff_t index);
116 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
117         struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type);
118
119 static inline int shmem_getpage(struct inode *inode, pgoff_t index,
120         struct page **pagep, enum sgp_type sgp, int *fault_type)
121 {
122         return shmem_getpage_gfp(inode, index, pagep, sgp,
123                         mapping_gfp_mask(inode->i_mapping), fault_type);
124 }
125
126 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
127 {
128         return sb->s_fs_info;
129 }
130
131 /*
132  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
133  * for shared memory and for shared anonymous (/dev/zero) mappings
134  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
135  * consistent with the pre-accounting of private mappings ...
136  */
137 static inline int shmem_acct_size(unsigned long flags, loff_t size)
138 {
139         return (flags & VM_NORESERVE) ?
140                 0 : security_vm_enough_memory_mm(current->mm, VM_ACCT(size));
141 }
142
143 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
144 {
145         if (!(flags & VM_NORESERVE))
146                 vm_unacct_memory(VM_ACCT(size));
147 }
148
149 /*
150  * ... whereas tmpfs objects are accounted incrementally as
151  * pages are allocated, in order to allow huge sparse files.
152  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
153  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
154  */
155 static inline int shmem_acct_block(unsigned long flags)
156 {
157         return (flags & VM_NORESERVE) ?
158                 security_vm_enough_memory_mm(current->mm, VM_ACCT(PAGE_CACHE_SIZE)) : 0;
159 }
160
161 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
162 {
163         if (flags & VM_NORESERVE)
164                 vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
165 }
166
167 static const struct super_operations shmem_ops;
168 static const struct address_space_operations shmem_aops;
169 static const struct file_operations shmem_file_operations;
170 static const struct inode_operations shmem_inode_operations;
171 static const struct inode_operations shmem_dir_inode_operations;
172 static const struct inode_operations shmem_special_inode_operations;
173 static const struct vm_operations_struct shmem_vm_ops;
174
175 static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
176         .ra_pages       = 0,    /* No readahead */
177         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
178 };
179
180 static LIST_HEAD(shmem_swaplist);
181 static DEFINE_MUTEX(shmem_swaplist_mutex);
182
183 static int shmem_reserve_inode(struct super_block *sb)
184 {
185         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
186         if (sbinfo->max_inodes) {
187                 spin_lock(&sbinfo->stat_lock);
188                 if (!sbinfo->free_inodes) {
189                         spin_unlock(&sbinfo->stat_lock);
190                         return -ENOSPC;
191                 }
192                 sbinfo->free_inodes--;
193                 spin_unlock(&sbinfo->stat_lock);
194         }
195         return 0;
196 }
197
198 static void shmem_free_inode(struct super_block *sb)
199 {
200         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
201         if (sbinfo->max_inodes) {
202                 spin_lock(&sbinfo->stat_lock);
203                 sbinfo->free_inodes++;
204                 spin_unlock(&sbinfo->stat_lock);
205         }
206 }
207
208 /**
209  * shmem_recalc_inode - recalculate the block usage of an inode
210  * @inode: inode to recalc
211  *
212  * We have to calculate the free blocks since the mm can drop
213  * undirtied hole pages behind our back.
214  *
215  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
216  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
217  *
218  * It has to be called with the spinlock held.
219  */
220 static void shmem_recalc_inode(struct inode *inode)
221 {
222         struct shmem_inode_info *info = SHMEM_I(inode);
223         long freed;
224
225         freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
226         if (freed > 0) {
227                 struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
228                 if (sbinfo->max_blocks)
229                         percpu_counter_add(&sbinfo->used_blocks, -freed);
230                 info->alloced -= freed;
231                 inode->i_blocks -= freed * BLOCKS_PER_PAGE;
232                 shmem_unacct_blocks(info->flags, freed);
233         }
234 }
235
236 /*
237  * Replace item expected in radix tree by a new item, while holding tree lock.
238  */
239 static int shmem_radix_tree_replace(struct address_space *mapping,
240                         pgoff_t index, void *expected, void *replacement)
241 {
242         void **pslot;
243         void *item = NULL;
244
245         VM_BUG_ON(!expected);
246         pslot = radix_tree_lookup_slot(&mapping->page_tree, index);
247         if (pslot)
248                 item = radix_tree_deref_slot_protected(pslot,
249                                                         &mapping->tree_lock);
250         if (item != expected)
251                 return -ENOENT;
252         if (replacement)
253                 radix_tree_replace_slot(pslot, replacement);
254         else
255                 radix_tree_delete(&mapping->page_tree, index);
256         return 0;
257 }
258
259 /*
260  * Sometimes, before we decide whether to proceed or to fail, we must check
261  * that an entry was not already brought back from swap by a racing thread.
262  *
263  * Checking page is not enough: by the time a SwapCache page is locked, it
264  * might be reused, and again be SwapCache, using the same swap as before.
265  */
266 static bool shmem_confirm_swap(struct address_space *mapping,
267                                pgoff_t index, swp_entry_t swap)
268 {
269         void *item;
270
271         rcu_read_lock();
272         item = radix_tree_lookup(&mapping->page_tree, index);
273         rcu_read_unlock();
274         return item == swp_to_radix_entry(swap);
275 }
276
277 /*
278  * Like add_to_page_cache_locked, but error if expected item has gone.
279  */
280 static int shmem_add_to_page_cache(struct page *page,
281                                    struct address_space *mapping,
282                                    pgoff_t index, gfp_t gfp, void *expected)
283 {
284         int error;
285
286         VM_BUG_ON(!PageLocked(page));
287         VM_BUG_ON(!PageSwapBacked(page));
288
289         page_cache_get(page);
290         page->mapping = mapping;
291         page->index = index;
292
293         spin_lock_irq(&mapping->tree_lock);
294         if (!expected)
295                 error = radix_tree_insert(&mapping->page_tree, index, page);
296         else
297                 error = shmem_radix_tree_replace(mapping, index, expected,
298                                                                  page);
299         if (!error) {
300                 mapping->nrpages++;
301                 __inc_zone_page_state(page, NR_FILE_PAGES);
302                 __inc_zone_page_state(page, NR_SHMEM);
303                 spin_unlock_irq(&mapping->tree_lock);
304         } else {
305                 page->mapping = NULL;
306                 spin_unlock_irq(&mapping->tree_lock);
307                 page_cache_release(page);
308         }
309         return error;
310 }
311
312 /*
313  * Like delete_from_page_cache, but substitutes swap for page.
314  */
315 static void shmem_delete_from_page_cache(struct page *page, void *radswap)
316 {
317         struct address_space *mapping = page->mapping;
318         int error;
319
320         spin_lock_irq(&mapping->tree_lock);
321         error = shmem_radix_tree_replace(mapping, page->index, page, radswap);
322         page->mapping = NULL;
323         mapping->nrpages--;
324         __dec_zone_page_state(page, NR_FILE_PAGES);
325         __dec_zone_page_state(page, NR_SHMEM);
326         spin_unlock_irq(&mapping->tree_lock);
327         page_cache_release(page);
328         BUG_ON(error);
329 }
330
331 /*
332  * Like find_get_pages, but collecting swap entries as well as pages.
333  */
334 static unsigned shmem_find_get_pages_and_swap(struct address_space *mapping,
335                                         pgoff_t start, unsigned int nr_pages,
336                                         struct page **pages, pgoff_t *indices)
337 {
338         unsigned int i;
339         unsigned int ret;
340         unsigned int nr_found;
341
342         rcu_read_lock();
343 restart:
344         nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
345                                 (void ***)pages, indices, start, nr_pages);
346         ret = 0;
347         for (i = 0; i < nr_found; i++) {
348                 struct page *page;
349 repeat:
350                 page = radix_tree_deref_slot((void **)pages[i]);
351                 if (unlikely(!page))
352                         continue;
353                 if (radix_tree_exception(page)) {
354                         if (radix_tree_deref_retry(page))
355                                 goto restart;
356                         /*
357                          * Otherwise, we must be storing a swap entry
358                          * here as an exceptional entry: so return it
359                          * without attempting to raise page count.
360                          */
361                         goto export;
362                 }
363                 if (!page_cache_get_speculative(page))
364                         goto repeat;
365
366                 /* Has the page moved? */
367                 if (unlikely(page != *((void **)pages[i]))) {
368                         page_cache_release(page);
369                         goto repeat;
370                 }
371 export:
372                 indices[ret] = indices[i];
373                 pages[ret] = page;
374                 ret++;
375         }
376         if (unlikely(!ret && nr_found))
377                 goto restart;
378         rcu_read_unlock();
379         return ret;
380 }
381
382 /*
383  * Remove swap entry from radix tree, free the swap and its page cache.
384  */
385 static int shmem_free_swap(struct address_space *mapping,
386                            pgoff_t index, void *radswap)
387 {
388         int error;
389
390         spin_lock_irq(&mapping->tree_lock);
391         error = shmem_radix_tree_replace(mapping, index, radswap, NULL);
392         spin_unlock_irq(&mapping->tree_lock);
393         if (!error)
394                 free_swap_and_cache(radix_to_swp_entry(radswap));
395         return error;
396 }
397
398 /*
399  * Pagevec may contain swap entries, so shuffle up pages before releasing.
400  */
401 static void shmem_deswap_pagevec(struct pagevec *pvec)
402 {
403         int i, j;
404
405         for (i = 0, j = 0; i < pagevec_count(pvec); i++) {
406                 struct page *page = pvec->pages[i];
407                 if (!radix_tree_exceptional_entry(page))
408                         pvec->pages[j++] = page;
409         }
410         pvec->nr = j;
411 }
412
413 /*
414  * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists.
415  */
416 void shmem_unlock_mapping(struct address_space *mapping)
417 {
418         struct pagevec pvec;
419         pgoff_t indices[PAGEVEC_SIZE];
420         pgoff_t index = 0;
421
422         pagevec_init(&pvec, 0);
423         /*
424          * Minor point, but we might as well stop if someone else SHM_LOCKs it.
425          */
426         while (!mapping_unevictable(mapping)) {
427                 /*
428                  * Avoid pagevec_lookup(): find_get_pages() returns 0 as if it
429                  * has finished, if it hits a row of PAGEVEC_SIZE swap entries.
430                  */
431                 pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
432                                         PAGEVEC_SIZE, pvec.pages, indices);
433                 if (!pvec.nr)
434                         break;
435                 index = indices[pvec.nr - 1] + 1;
436                 shmem_deswap_pagevec(&pvec);
437                 check_move_unevictable_pages(pvec.pages, pvec.nr);
438                 pagevec_release(&pvec);
439                 cond_resched();
440         }
441 }
442
443 /*
444  * Remove range of pages and swap entries from radix tree, and free them.
445  * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.
446  */
447 static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
448                                                                  bool unfalloc)
449 {
450         struct address_space *mapping = inode->i_mapping;
451         struct shmem_inode_info *info = SHMEM_I(inode);
452         pgoff_t start = (lstart + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
453         pgoff_t end = (lend + 1) >> PAGE_CACHE_SHIFT;
454         unsigned int partial_start = lstart & (PAGE_CACHE_SIZE - 1);
455         unsigned int partial_end = (lend + 1) & (PAGE_CACHE_SIZE - 1);
456         struct pagevec pvec;
457         pgoff_t indices[PAGEVEC_SIZE];
458         long nr_swaps_freed = 0;
459         pgoff_t index;
460         int i;
461
462         if (lend == -1)
463                 end = -1;       /* unsigned, so actually very big */
464
465         pagevec_init(&pvec, 0);
466         index = start;
467         while (index < end) {
468                 pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
469                                 min(end - index, (pgoff_t)PAGEVEC_SIZE),
470                                                         pvec.pages, indices);
471                 if (!pvec.nr)
472                         break;
473                 mem_cgroup_uncharge_start();
474                 for (i = 0; i < pagevec_count(&pvec); i++) {
475                         struct page *page = pvec.pages[i];
476
477                         index = indices[i];
478                         if (index >= end)
479                                 break;
480
481                         if (radix_tree_exceptional_entry(page)) {
482                                 if (unfalloc)
483                                         continue;
484                                 nr_swaps_freed += !shmem_free_swap(mapping,
485                                                                 index, page);
486                                 continue;
487                         }
488
489                         if (!trylock_page(page))
490                                 continue;
491                         if (!unfalloc || !PageUptodate(page)) {
492                                 if (page->mapping == mapping) {
493                                         VM_BUG_ON(PageWriteback(page));
494                                         truncate_inode_page(mapping, page);
495                                 }
496                         }
497                         unlock_page(page);
498                 }
499                 shmem_deswap_pagevec(&pvec);
500                 pagevec_release(&pvec);
501                 mem_cgroup_uncharge_end();
502                 cond_resched();
503                 index++;
504         }
505
506         if (partial_start) {
507                 struct page *page = NULL;
508                 shmem_getpage(inode, start - 1, &page, SGP_READ, NULL);
509                 if (page) {
510                         unsigned int top = PAGE_CACHE_SIZE;
511                         if (start > end) {
512                                 top = partial_end;
513                                 partial_end = 0;
514                         }
515                         zero_user_segment(page, partial_start, top);
516                         set_page_dirty(page);
517                         unlock_page(page);
518                         page_cache_release(page);
519                 }
520         }
521         if (partial_end) {
522                 struct page *page = NULL;
523                 shmem_getpage(inode, end, &page, SGP_READ, NULL);
524                 if (page) {
525                         zero_user_segment(page, 0, partial_end);
526                         set_page_dirty(page);
527                         unlock_page(page);
528                         page_cache_release(page);
529                 }
530         }
531         if (start >= end)
532                 return;
533
534         index = start;
535         for ( ; ; ) {
536                 cond_resched();
537                 pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
538                                 min(end - index, (pgoff_t)PAGEVEC_SIZE),
539                                                         pvec.pages, indices);
540                 if (!pvec.nr) {
541                         if (index == start || unfalloc)
542                                 break;
543                         index = start;
544                         continue;
545                 }
546                 if ((index == start || unfalloc) && indices[0] >= end) {
547                         shmem_deswap_pagevec(&pvec);
548                         pagevec_release(&pvec);
549                         break;
550                 }
551                 mem_cgroup_uncharge_start();
552                 for (i = 0; i < pagevec_count(&pvec); i++) {
553                         struct page *page = pvec.pages[i];
554
555                         index = indices[i];
556                         if (index >= end)
557                                 break;
558
559                         if (radix_tree_exceptional_entry(page)) {
560                                 if (unfalloc)
561                                         continue;
562                                 nr_swaps_freed += !shmem_free_swap(mapping,
563                                                                 index, page);
564                                 continue;
565                         }
566
567                         lock_page(page);
568                         if (!unfalloc || !PageUptodate(page)) {
569                                 if (page->mapping == mapping) {
570                                         VM_BUG_ON(PageWriteback(page));
571                                         truncate_inode_page(mapping, page);
572                                 }
573                         }
574                         unlock_page(page);
575                 }
576                 shmem_deswap_pagevec(&pvec);
577                 pagevec_release(&pvec);
578                 mem_cgroup_uncharge_end();
579                 index++;
580         }
581
582         spin_lock(&info->lock);
583         info->swapped -= nr_swaps_freed;
584         shmem_recalc_inode(inode);
585         spin_unlock(&info->lock);
586 }
587
588 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
589 {
590         shmem_undo_range(inode, lstart, lend, false);
591         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
592 }
593 EXPORT_SYMBOL_GPL(shmem_truncate_range);
594
595 static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
596 {
597         struct inode *inode = dentry->d_inode;
598         int error;
599
600         error = inode_change_ok(inode, attr);
601         if (error)
602                 return error;
603
604         if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
605                 loff_t oldsize = inode->i_size;
606                 loff_t newsize = attr->ia_size;
607
608                 if (newsize != oldsize) {
609                         i_size_write(inode, newsize);
610                         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
611                 }
612                 if (newsize < oldsize) {
613                         loff_t holebegin = round_up(newsize, PAGE_SIZE);
614                         unmap_mapping_range(inode->i_mapping, holebegin, 0, 1);
615                         shmem_truncate_range(inode, newsize, (loff_t)-1);
616                         /* unmap again to remove racily COWed private pages */
617                         unmap_mapping_range(inode->i_mapping, holebegin, 0, 1);
618                 }
619         }
620
621         setattr_copy(inode, attr);
622 #ifdef CONFIG_TMPFS_POSIX_ACL
623         if (attr->ia_valid & ATTR_MODE)
624                 error = generic_acl_chmod(inode);
625 #endif
626         return error;
627 }
628
629 static void shmem_evict_inode(struct inode *inode)
630 {
631         struct shmem_inode_info *info = SHMEM_I(inode);
632
633         if (inode->i_mapping->a_ops == &shmem_aops) {
634                 shmem_unacct_size(info->flags, inode->i_size);
635                 inode->i_size = 0;
636                 shmem_truncate_range(inode, 0, (loff_t)-1);
637                 if (!list_empty(&info->swaplist)) {
638                         mutex_lock(&shmem_swaplist_mutex);
639                         list_del_init(&info->swaplist);
640                         mutex_unlock(&shmem_swaplist_mutex);
641                 }
642         } else
643                 kfree(info->symlink);
644
645         simple_xattrs_free(&info->xattrs);
646         WARN_ON(inode->i_blocks);
647         shmem_free_inode(inode->i_sb);
648         clear_inode(inode);
649 }
650
651 /*
652  * If swap found in inode, free it and move page from swapcache to filecache.
653  */
654 static int shmem_unuse_inode(struct shmem_inode_info *info,
655                              swp_entry_t swap, struct page **pagep)
656 {
657         struct address_space *mapping = info->vfs_inode.i_mapping;
658         void *radswap;
659         pgoff_t index;
660         gfp_t gfp;
661         int error = 0;
662
663         radswap = swp_to_radix_entry(swap);
664         index = radix_tree_locate_item(&mapping->page_tree, radswap);
665         if (index == -1)
666                 return 0;
667
668         /*
669          * Move _head_ to start search for next from here.
670          * But be careful: shmem_evict_inode checks list_empty without taking
671          * mutex, and there's an instant in list_move_tail when info->swaplist
672          * would appear empty, if it were the only one on shmem_swaplist.
673          */
674         if (shmem_swaplist.next != &info->swaplist)
675                 list_move_tail(&shmem_swaplist, &info->swaplist);
676
677         gfp = mapping_gfp_mask(mapping);
678         if (shmem_should_replace_page(*pagep, gfp)) {
679                 mutex_unlock(&shmem_swaplist_mutex);
680                 error = shmem_replace_page(pagep, gfp, info, index);
681                 mutex_lock(&shmem_swaplist_mutex);
682                 /*
683                  * We needed to drop mutex to make that restrictive page
684                  * allocation, but the inode might have been freed while we
685                  * dropped it: although a racing shmem_evict_inode() cannot
686                  * complete without emptying the radix_tree, our page lock
687                  * on this swapcache page is not enough to prevent that -
688                  * free_swap_and_cache() of our swap entry will only
689                  * trylock_page(), removing swap from radix_tree whatever.
690                  *
691                  * We must not proceed to shmem_add_to_page_cache() if the
692                  * inode has been freed, but of course we cannot rely on
693                  * inode or mapping or info to check that.  However, we can
694                  * safely check if our swap entry is still in use (and here
695                  * it can't have got reused for another page): if it's still
696                  * in use, then the inode cannot have been freed yet, and we
697                  * can safely proceed (if it's no longer in use, that tells
698                  * nothing about the inode, but we don't need to unuse swap).
699                  */
700                 if (!page_swapcount(*pagep))
701                         error = -ENOENT;
702         }
703
704         /*
705          * We rely on shmem_swaplist_mutex, not only to protect the swaplist,
706          * but also to hold up shmem_evict_inode(): so inode cannot be freed
707          * beneath us (pagelock doesn't help until the page is in pagecache).
708          */
709         if (!error)
710                 error = shmem_add_to_page_cache(*pagep, mapping, index,
711                                                 GFP_NOWAIT, radswap);
712         if (error != -ENOMEM) {
713                 /*
714                  * Truncation and eviction use free_swap_and_cache(), which
715                  * only does trylock page: if we raced, best clean up here.
716                  */
717                 delete_from_swap_cache(*pagep);
718                 set_page_dirty(*pagep);
719                 if (!error) {
720                         spin_lock(&info->lock);
721                         info->swapped--;
722                         spin_unlock(&info->lock);
723                         swap_free(swap);
724                 }
725                 error = 1;      /* not an error, but entry was found */
726         }
727         return error;
728 }
729
730 /*
731  * Search through swapped inodes to find and replace swap by page.
732  */
733 int shmem_unuse(swp_entry_t swap, struct page *page)
734 {
735         struct list_head *this, *next;
736         struct shmem_inode_info *info;
737         int found = 0;
738         int error = 0;
739
740         /*
741          * There's a faint possibility that swap page was replaced before
742          * caller locked it: caller will come back later with the right page.
743          */
744         if (unlikely(!PageSwapCache(page) || page_private(page) != swap.val))
745                 goto out;
746
747         /*
748          * Charge page using GFP_KERNEL while we can wait, before taking
749          * the shmem_swaplist_mutex which might hold up shmem_writepage().
750          * Charged back to the user (not to caller) when swap account is used.
751          */
752         error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL);
753         if (error)
754                 goto out;
755         /* No radix_tree_preload: swap entry keeps a place for page in tree */
756
757         mutex_lock(&shmem_swaplist_mutex);
758         list_for_each_safe(this, next, &shmem_swaplist) {
759                 info = list_entry(this, struct shmem_inode_info, swaplist);
760                 if (info->swapped)
761                         found = shmem_unuse_inode(info, swap, &page);
762                 else
763                         list_del_init(&info->swaplist);
764                 cond_resched();
765                 if (found)
766                         break;
767         }
768         mutex_unlock(&shmem_swaplist_mutex);
769
770         if (found < 0)
771                 error = found;
772 out:
773         unlock_page(page);
774         page_cache_release(page);
775         return error;
776 }
777
778 /*
779  * Move the page from the page cache to the swap cache.
780  */
781 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
782 {
783         struct shmem_inode_info *info;
784         struct address_space *mapping;
785         struct inode *inode;
786         swp_entry_t swap;
787         pgoff_t index;
788
789         BUG_ON(!PageLocked(page));
790         mapping = page->mapping;
791         index = page->index;
792         inode = mapping->host;
793         info = SHMEM_I(inode);
794         if (info->flags & VM_LOCKED)
795                 goto redirty;
796         if (!total_swap_pages)
797                 goto redirty;
798
799         /*
800          * shmem_backing_dev_info's capabilities prevent regular writeback or
801          * sync from ever calling shmem_writepage; but a stacking filesystem
802          * might use ->writepage of its underlying filesystem, in which case
803          * tmpfs should write out to swap only in response to memory pressure,
804          * and not for the writeback threads or sync.
805          */
806         if (!wbc->for_reclaim) {
807                 WARN_ON_ONCE(1);        /* Still happens? Tell us about it! */
808                 goto redirty;
809         }
810
811         /*
812          * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC
813          * value into swapfile.c, the only way we can correctly account for a
814          * fallocated page arriving here is now to initialize it and write it.
815          *
816          * That's okay for a page already fallocated earlier, but if we have
817          * not yet completed the fallocation, then (a) we want to keep track
818          * of this page in case we have to undo it, and (b) it may not be a
819          * good idea to continue anyway, once we're pushing into swap.  So
820          * reactivate the page, and let shmem_fallocate() quit when too many.
821          */
822         if (!PageUptodate(page)) {
823                 if (inode->i_private) {
824                         struct shmem_falloc *shmem_falloc;
825                         spin_lock(&inode->i_lock);
826                         shmem_falloc = inode->i_private;
827                         if (shmem_falloc &&
828                             index >= shmem_falloc->start &&
829                             index < shmem_falloc->next)
830                                 shmem_falloc->nr_unswapped++;
831                         else
832                                 shmem_falloc = NULL;
833                         spin_unlock(&inode->i_lock);
834                         if (shmem_falloc)
835                                 goto redirty;
836                 }
837                 clear_highpage(page);
838                 flush_dcache_page(page);
839                 SetPageUptodate(page);
840         }
841
842         swap = get_swap_page();
843         if (!swap.val)
844                 goto redirty;
845
846         /*
847          * Add inode to shmem_unuse()'s list of swapped-out inodes,
848          * if it's not already there.  Do it now before the page is
849          * moved to swap cache, when its pagelock no longer protects
850          * the inode from eviction.  But don't unlock the mutex until
851          * we've incremented swapped, because shmem_unuse_inode() will
852          * prune a !swapped inode from the swaplist under this mutex.
853          */
854         mutex_lock(&shmem_swaplist_mutex);
855         if (list_empty(&info->swaplist))
856                 list_add_tail(&info->swaplist, &shmem_swaplist);
857
858         if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
859                 swap_shmem_alloc(swap);
860                 shmem_delete_from_page_cache(page, swp_to_radix_entry(swap));
861
862                 spin_lock(&info->lock);
863                 info->swapped++;
864                 shmem_recalc_inode(inode);
865                 spin_unlock(&info->lock);
866
867                 mutex_unlock(&shmem_swaplist_mutex);
868                 BUG_ON(page_mapped(page));
869                 swap_writepage(page, wbc);
870                 return 0;
871         }
872
873         mutex_unlock(&shmem_swaplist_mutex);
874         swapcache_free(swap, NULL);
875 redirty:
876         set_page_dirty(page);
877         if (wbc->for_reclaim)
878                 return AOP_WRITEPAGE_ACTIVATE;  /* Return with page locked */
879         unlock_page(page);
880         return 0;
881 }
882
883 #ifdef CONFIG_NUMA
884 #ifdef CONFIG_TMPFS
885 static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
886 {
887         char buffer[64];
888
889         if (!mpol || mpol->mode == MPOL_DEFAULT)
890                 return;         /* show nothing */
891
892         mpol_to_str(buffer, sizeof(buffer), mpol, 1);
893
894         seq_printf(seq, ",mpol=%s", buffer);
895 }
896
897 static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
898 {
899         struct mempolicy *mpol = NULL;
900         if (sbinfo->mpol) {
901                 spin_lock(&sbinfo->stat_lock);  /* prevent replace/use races */
902                 mpol = sbinfo->mpol;
903                 mpol_get(mpol);
904                 spin_unlock(&sbinfo->stat_lock);
905         }
906         return mpol;
907 }
908 #endif /* CONFIG_TMPFS */
909
910 static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
911                         struct shmem_inode_info *info, pgoff_t index)
912 {
913         struct vm_area_struct pvma;
914         struct page *page;
915
916         /* Create a pseudo vma that just contains the policy */
917         pvma.vm_start = 0;
918         /* Bias interleave by inode number to distribute better across nodes */
919         pvma.vm_pgoff = index + info->vfs_inode.i_ino;
920         pvma.vm_ops = NULL;
921         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
922
923         page = swapin_readahead(swap, gfp, &pvma, 0);
924
925         /* Drop reference taken by mpol_shared_policy_lookup() */
926         mpol_cond_put(pvma.vm_policy);
927
928         return page;
929 }
930
931 static struct page *shmem_alloc_page(gfp_t gfp,
932                         struct shmem_inode_info *info, pgoff_t index)
933 {
934         struct vm_area_struct pvma;
935         struct page *page;
936
937         /* Create a pseudo vma that just contains the policy */
938         pvma.vm_start = 0;
939         /* Bias interleave by inode number to distribute better across nodes */
940         pvma.vm_pgoff = index + info->vfs_inode.i_ino;
941         pvma.vm_ops = NULL;
942         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
943
944         page = alloc_page_vma(gfp, &pvma, 0);
945
946         /* Drop reference taken by mpol_shared_policy_lookup() */
947         mpol_cond_put(pvma.vm_policy);
948
949         return page;
950 }
951 #else /* !CONFIG_NUMA */
952 #ifdef CONFIG_TMPFS
953 static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
954 {
955 }
956 #endif /* CONFIG_TMPFS */
957
958 static inline struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
959                         struct shmem_inode_info *info, pgoff_t index)
960 {
961         return swapin_readahead(swap, gfp, NULL, 0);
962 }
963
964 static inline struct page *shmem_alloc_page(gfp_t gfp,
965                         struct shmem_inode_info *info, pgoff_t index)
966 {
967         return alloc_page(gfp);
968 }
969 #endif /* CONFIG_NUMA */
970
971 #if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS)
972 static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
973 {
974         return NULL;
975 }
976 #endif
977
978 /*
979  * When a page is moved from swapcache to shmem filecache (either by the
980  * usual swapin of shmem_getpage_gfp(), or by the less common swapoff of
981  * shmem_unuse_inode()), it may have been read in earlier from swap, in
982  * ignorance of the mapping it belongs to.  If that mapping has special
983  * constraints (like the gma500 GEM driver, which requires RAM below 4GB),
984  * we may need to copy to a suitable page before moving to filecache.
985  *
986  * In a future release, this may well be extended to respect cpuset and
987  * NUMA mempolicy, and applied also to anonymous pages in do_swap_page();
988  * but for now it is a simple matter of zone.
989  */
990 static bool shmem_should_replace_page(struct page *page, gfp_t gfp)
991 {
992         return page_zonenum(page) > gfp_zone(gfp);
993 }
994
995 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
996                                 struct shmem_inode_info *info, pgoff_t index)
997 {
998         struct page *oldpage, *newpage;
999         struct address_space *swap_mapping;
1000         pgoff_t swap_index;
1001         int error;
1002
1003         oldpage = *pagep;
1004         swap_index = page_private(oldpage);
1005         swap_mapping = page_mapping(oldpage);
1006
1007         /*
1008          * We have arrived here because our zones are constrained, so don't
1009          * limit chance of success by further cpuset and node constraints.
1010          */
1011         gfp &= ~GFP_CONSTRAINT_MASK;
1012         newpage = shmem_alloc_page(gfp, info, index);
1013         if (!newpage)
1014                 return -ENOMEM;
1015
1016         page_cache_get(newpage);
1017         copy_highpage(newpage, oldpage);
1018         flush_dcache_page(newpage);
1019
1020         __set_page_locked(newpage);
1021         SetPageUptodate(newpage);
1022         SetPageSwapBacked(newpage);
1023         set_page_private(newpage, swap_index);
1024         SetPageSwapCache(newpage);
1025
1026         /*
1027          * Our caller will very soon move newpage out of swapcache, but it's
1028          * a nice clean interface for us to replace oldpage by newpage there.
1029          */
1030         spin_lock_irq(&swap_mapping->tree_lock);
1031         error = shmem_radix_tree_replace(swap_mapping, swap_index, oldpage,
1032                                                                    newpage);
1033         if (!error) {
1034                 __inc_zone_page_state(newpage, NR_FILE_PAGES);
1035                 __dec_zone_page_state(oldpage, NR_FILE_PAGES);
1036         }
1037         spin_unlock_irq(&swap_mapping->tree_lock);
1038
1039         if (unlikely(error)) {
1040                 /*
1041                  * Is this possible?  I think not, now that our callers check
1042                  * both PageSwapCache and page_private after getting page lock;
1043                  * but be defensive.  Reverse old to newpage for clear and free.
1044                  */
1045                 oldpage = newpage;
1046         } else {
1047                 mem_cgroup_replace_page_cache(oldpage, newpage);
1048                 lru_cache_add_anon(newpage);
1049                 *pagep = newpage;
1050         }
1051
1052         ClearPageSwapCache(oldpage);
1053         set_page_private(oldpage, 0);
1054
1055         unlock_page(oldpage);
1056         page_cache_release(oldpage);
1057         page_cache_release(oldpage);
1058         return error;
1059 }
1060
1061 /*
1062  * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
1063  *
1064  * If we allocate a new one we do not mark it dirty. That's up to the
1065  * vm. If we swap it in we mark it dirty since we also free the swap
1066  * entry since a page cannot live in both the swap and page cache
1067  */
1068 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
1069         struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type)
1070 {
1071         struct address_space *mapping = inode->i_mapping;
1072         struct shmem_inode_info *info;
1073         struct shmem_sb_info *sbinfo;
1074         struct page *page;
1075         swp_entry_t swap;
1076         int error;
1077         int once = 0;
1078         int alloced = 0;
1079
1080         if (index > (MAX_LFS_FILESIZE >> PAGE_CACHE_SHIFT))
1081                 return -EFBIG;
1082 repeat:
1083         swap.val = 0;
1084         page = find_lock_page(mapping, index);
1085         if (radix_tree_exceptional_entry(page)) {
1086                 swap = radix_to_swp_entry(page);
1087                 page = NULL;
1088         }
1089
1090         if (sgp != SGP_WRITE && sgp != SGP_FALLOC &&
1091             ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
1092                 error = -EINVAL;
1093                 goto failed;
1094         }
1095
1096         /* fallocated page? */
1097         if (page && !PageUptodate(page)) {
1098                 if (sgp != SGP_READ)
1099                         goto clear;
1100                 unlock_page(page);
1101                 page_cache_release(page);
1102                 page = NULL;
1103         }
1104         if (page || (sgp == SGP_READ && !swap.val)) {
1105                 *pagep = page;
1106                 return 0;
1107         }
1108
1109         /*
1110          * Fast cache lookup did not find it:
1111          * bring it back from swap or allocate.
1112          */
1113         info = SHMEM_I(inode);
1114         sbinfo = SHMEM_SB(inode->i_sb);
1115
1116         if (swap.val) {
1117                 /* Look it up and read it in.. */
1118                 page = lookup_swap_cache(swap);
1119                 if (!page) {
1120                         /* here we actually do the io */
1121                         if (fault_type)
1122                                 *fault_type |= VM_FAULT_MAJOR;
1123                         page = shmem_swapin(swap, gfp, info, index);
1124                         if (!page) {
1125                                 error = -ENOMEM;
1126                                 goto failed;
1127                         }
1128                 }
1129
1130                 /* We have to do this with page locked to prevent races */
1131                 lock_page(page);
1132                 if (!PageSwapCache(page) || page_private(page) != swap.val ||
1133                     !shmem_confirm_swap(mapping, index, swap)) {
1134                         error = -EEXIST;        /* try again */
1135                         goto unlock;
1136                 }
1137                 if (!PageUptodate(page)) {
1138                         error = -EIO;
1139                         goto failed;
1140                 }
1141                 wait_on_page_writeback(page);
1142
1143                 if (shmem_should_replace_page(page, gfp)) {
1144                         error = shmem_replace_page(&page, gfp, info, index);
1145                         if (error)
1146                                 goto failed;
1147                 }
1148
1149                 error = mem_cgroup_cache_charge(page, current->mm,
1150                                                 gfp & GFP_RECLAIM_MASK);
1151                 if (!error) {
1152                         error = shmem_add_to_page_cache(page, mapping, index,
1153                                                 gfp, swp_to_radix_entry(swap));
1154                         /*
1155                          * We already confirmed swap under page lock, and make
1156                          * no memory allocation here, so usually no possibility
1157                          * of error; but free_swap_and_cache() only trylocks a
1158                          * page, so it is just possible that the entry has been
1159                          * truncated or holepunched since swap was confirmed.
1160                          * shmem_undo_range() will have done some of the
1161                          * unaccounting, now delete_from_swap_cache() will do
1162                          * the rest (including mem_cgroup_uncharge_swapcache).
1163                          * Reset swap.val? No, leave it so "failed" goes back to
1164                          * "repeat": reading a hole and writing should succeed.
1165                          */
1166                         if (error)
1167                                 delete_from_swap_cache(page);
1168                 }
1169                 if (error)
1170                         goto failed;
1171
1172                 spin_lock(&info->lock);
1173                 info->swapped--;
1174                 shmem_recalc_inode(inode);
1175                 spin_unlock(&info->lock);
1176
1177                 delete_from_swap_cache(page);
1178                 set_page_dirty(page);
1179                 swap_free(swap);
1180
1181         } else {
1182                 if (shmem_acct_block(info->flags)) {
1183                         error = -ENOSPC;
1184                         goto failed;
1185                 }
1186                 if (sbinfo->max_blocks) {
1187                         if (percpu_counter_compare(&sbinfo->used_blocks,
1188                                                 sbinfo->max_blocks) >= 0) {
1189                                 error = -ENOSPC;
1190                                 goto unacct;
1191                         }
1192                         percpu_counter_inc(&sbinfo->used_blocks);
1193                 }
1194
1195                 page = shmem_alloc_page(gfp, info, index);
1196                 if (!page) {
1197                         error = -ENOMEM;
1198                         goto decused;
1199                 }
1200
1201                 SetPageSwapBacked(page);
1202                 __set_page_locked(page);
1203                 error = mem_cgroup_cache_charge(page, current->mm,
1204                                                 gfp & GFP_RECLAIM_MASK);
1205                 if (error)
1206                         goto decused;
1207                 error = radix_tree_preload(gfp & GFP_RECLAIM_MASK);
1208                 if (!error) {
1209                         error = shmem_add_to_page_cache(page, mapping, index,
1210                                                         gfp, NULL);
1211                         radix_tree_preload_end();
1212                 }
1213                 if (error) {
1214                         mem_cgroup_uncharge_cache_page(page);
1215                         goto decused;
1216                 }
1217                 lru_cache_add_anon(page);
1218
1219                 spin_lock(&info->lock);
1220                 info->alloced++;
1221                 inode->i_blocks += BLOCKS_PER_PAGE;
1222                 shmem_recalc_inode(inode);
1223                 spin_unlock(&info->lock);
1224                 alloced = true;
1225
1226                 /*
1227                  * Let SGP_FALLOC use the SGP_WRITE optimization on a new page.
1228                  */
1229                 if (sgp == SGP_FALLOC)
1230                         sgp = SGP_WRITE;
1231 clear:
1232                 /*
1233                  * Let SGP_WRITE caller clear ends if write does not fill page;
1234                  * but SGP_FALLOC on a page fallocated earlier must initialize
1235                  * it now, lest undo on failure cancel our earlier guarantee.
1236                  */
1237                 if (sgp != SGP_WRITE) {
1238                         clear_highpage(page);
1239                         flush_dcache_page(page);
1240                         SetPageUptodate(page);
1241                 }
1242                 if (sgp == SGP_DIRTY)
1243                         set_page_dirty(page);
1244         }
1245
1246         /* Perhaps the file has been truncated since we checked */
1247         if (sgp != SGP_WRITE && sgp != SGP_FALLOC &&
1248             ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
1249                 error = -EINVAL;
1250                 if (alloced)
1251                         goto trunc;
1252                 else
1253                         goto failed;
1254         }
1255         *pagep = page;
1256         return 0;
1257
1258         /*
1259          * Error recovery.
1260          */
1261 trunc:
1262         info = SHMEM_I(inode);
1263         ClearPageDirty(page);
1264         delete_from_page_cache(page);
1265         spin_lock(&info->lock);
1266         info->alloced--;
1267         inode->i_blocks -= BLOCKS_PER_PAGE;
1268         spin_unlock(&info->lock);
1269 decused:
1270         sbinfo = SHMEM_SB(inode->i_sb);
1271         if (sbinfo->max_blocks)
1272                 percpu_counter_add(&sbinfo->used_blocks, -1);
1273 unacct:
1274         shmem_unacct_blocks(info->flags, 1);
1275 failed:
1276         if (swap.val && error != -EINVAL &&
1277             !shmem_confirm_swap(mapping, index, swap))
1278                 error = -EEXIST;
1279 unlock:
1280         if (page) {
1281                 unlock_page(page);
1282                 page_cache_release(page);
1283         }
1284         if (error == -ENOSPC && !once++) {
1285                 info = SHMEM_I(inode);
1286                 spin_lock(&info->lock);
1287                 shmem_recalc_inode(inode);
1288                 spin_unlock(&info->lock);
1289                 goto repeat;
1290         }
1291         if (error == -EEXIST)   /* from above or from radix_tree_insert */
1292                 goto repeat;
1293         return error;
1294 }
1295
1296 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1297 {
1298         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1299         int error;
1300         int ret = VM_FAULT_LOCKED;
1301
1302         error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
1303         if (error)
1304                 return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1305
1306         if (ret & VM_FAULT_MAJOR) {
1307                 count_vm_event(PGMAJFAULT);
1308                 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1309         }
1310         return ret;
1311 }
1312
1313 #ifdef CONFIG_NUMA
1314 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol)
1315 {
1316         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1317         return mpol_set_shared_policy(&SHMEM_I(inode)->policy, vma, mpol);
1318 }
1319
1320 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
1321                                           unsigned long addr)
1322 {
1323         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1324         pgoff_t index;
1325
1326         index = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1327         return mpol_shared_policy_lookup(&SHMEM_I(inode)->policy, index);
1328 }
1329 #endif
1330
1331 int shmem_lock(struct file *file, int lock, struct user_struct *user)
1332 {
1333         struct inode *inode = file->f_path.dentry->d_inode;
1334         struct shmem_inode_info *info = SHMEM_I(inode);
1335         int retval = -ENOMEM;
1336
1337         spin_lock(&info->lock);
1338         if (lock && !(info->flags & VM_LOCKED)) {
1339                 if (!user_shm_lock(inode->i_size, user))
1340                         goto out_nomem;
1341                 info->flags |= VM_LOCKED;
1342                 mapping_set_unevictable(file->f_mapping);
1343         }
1344         if (!lock && (info->flags & VM_LOCKED) && user) {
1345                 user_shm_unlock(inode->i_size, user);
1346                 info->flags &= ~VM_LOCKED;
1347                 mapping_clear_unevictable(file->f_mapping);
1348         }
1349         retval = 0;
1350
1351 out_nomem:
1352         spin_unlock(&info->lock);
1353         return retval;
1354 }
1355
1356 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1357 {
1358         file_accessed(file);
1359         vma->vm_ops = &shmem_vm_ops;
1360         return 0;
1361 }
1362
1363 static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
1364                                      umode_t mode, dev_t dev, unsigned long flags)
1365 {
1366         struct inode *inode;
1367         struct shmem_inode_info *info;
1368         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1369
1370         if (shmem_reserve_inode(sb))
1371                 return NULL;
1372
1373         inode = new_inode(sb);
1374         if (inode) {
1375                 inode->i_ino = get_next_ino();
1376                 inode_init_owner(inode, dir, mode);
1377                 inode->i_blocks = 0;
1378                 inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1379                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1380                 inode->i_generation = get_seconds();
1381                 info = SHMEM_I(inode);
1382                 memset(info, 0, (char *)inode - (char *)info);
1383                 spin_lock_init(&info->lock);
1384                 info->flags = flags & VM_NORESERVE;
1385                 INIT_LIST_HEAD(&info->swaplist);
1386                 simple_xattrs_init(&info->xattrs);
1387                 cache_no_acl(inode);
1388
1389                 switch (mode & S_IFMT) {
1390                 default:
1391                         inode->i_op = &shmem_special_inode_operations;
1392                         init_special_inode(inode, mode, dev);
1393                         break;
1394                 case S_IFREG:
1395                         inode->i_mapping->a_ops = &shmem_aops;
1396                         inode->i_op = &shmem_inode_operations;
1397                         inode->i_fop = &shmem_file_operations;
1398                         mpol_shared_policy_init(&info->policy,
1399                                                  shmem_get_sbmpol(sbinfo));
1400                         break;
1401                 case S_IFDIR:
1402                         inc_nlink(inode);
1403                         /* Some things misbehave if size == 0 on a directory */
1404                         inode->i_size = 2 * BOGO_DIRENT_SIZE;
1405                         inode->i_op = &shmem_dir_inode_operations;
1406                         inode->i_fop = &simple_dir_operations;
1407                         break;
1408                 case S_IFLNK:
1409                         /*
1410                          * Must not load anything in the rbtree,
1411                          * mpol_free_shared_policy will not be called.
1412                          */
1413                         mpol_shared_policy_init(&info->policy, NULL);
1414                         break;
1415                 }
1416         } else
1417                 shmem_free_inode(sb);
1418         return inode;
1419 }
1420
1421 #ifdef CONFIG_TMPFS
1422 static const struct inode_operations shmem_symlink_inode_operations;
1423 static const struct inode_operations shmem_short_symlink_operations;
1424
1425 #ifdef CONFIG_TMPFS_XATTR
1426 static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
1427 #else
1428 #define shmem_initxattrs NULL
1429 #endif
1430
1431 static int
1432 shmem_write_begin(struct file *file, struct address_space *mapping,
1433                         loff_t pos, unsigned len, unsigned flags,
1434                         struct page **pagep, void **fsdata)
1435 {
1436         struct inode *inode = mapping->host;
1437         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1438         return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
1439 }
1440
1441 static int
1442 shmem_write_end(struct file *file, struct address_space *mapping,
1443                         loff_t pos, unsigned len, unsigned copied,
1444                         struct page *page, void *fsdata)
1445 {
1446         struct inode *inode = mapping->host;
1447
1448         if (pos + copied > inode->i_size)
1449                 i_size_write(inode, pos + copied);
1450
1451         if (!PageUptodate(page)) {
1452                 if (copied < PAGE_CACHE_SIZE) {
1453                         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
1454                         zero_user_segments(page, 0, from,
1455                                         from + copied, PAGE_CACHE_SIZE);
1456                 }
1457                 SetPageUptodate(page);
1458         }
1459         set_page_dirty(page);
1460         unlock_page(page);
1461         page_cache_release(page);
1462
1463         return copied;
1464 }
1465
1466 static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1467 {
1468         struct inode *inode = filp->f_path.dentry->d_inode;
1469         struct address_space *mapping = inode->i_mapping;
1470         pgoff_t index;
1471         unsigned long offset;
1472         enum sgp_type sgp = SGP_READ;
1473
1474         /*
1475          * Might this read be for a stacking filesystem?  Then when reading
1476          * holes of a sparse file, we actually need to allocate those pages,
1477          * and even mark them dirty, so it cannot exceed the max_blocks limit.
1478          */
1479         if (segment_eq(get_fs(), KERNEL_DS))
1480                 sgp = SGP_DIRTY;
1481
1482         index = *ppos >> PAGE_CACHE_SHIFT;
1483         offset = *ppos & ~PAGE_CACHE_MASK;
1484
1485         for (;;) {
1486                 struct page *page = NULL;
1487                 pgoff_t end_index;
1488                 unsigned long nr, ret;
1489                 loff_t i_size = i_size_read(inode);
1490
1491                 end_index = i_size >> PAGE_CACHE_SHIFT;
1492                 if (index > end_index)
1493                         break;
1494                 if (index == end_index) {
1495                         nr = i_size & ~PAGE_CACHE_MASK;
1496                         if (nr <= offset)
1497                                 break;
1498                 }
1499
1500                 desc->error = shmem_getpage(inode, index, &page, sgp, NULL);
1501                 if (desc->error) {
1502                         if (desc->error == -EINVAL)
1503                                 desc->error = 0;
1504                         break;
1505                 }
1506                 if (page)
1507                         unlock_page(page);
1508
1509                 /*
1510                  * We must evaluate after, since reads (unlike writes)
1511                  * are called without i_mutex protection against truncate
1512                  */
1513                 nr = PAGE_CACHE_SIZE;
1514                 i_size = i_size_read(inode);
1515                 end_index = i_size >> PAGE_CACHE_SHIFT;
1516                 if (index == end_index) {
1517                         nr = i_size & ~PAGE_CACHE_MASK;
1518                         if (nr <= offset) {
1519                                 if (page)
1520                                         page_cache_release(page);
1521                                 break;
1522                         }
1523                 }
1524                 nr -= offset;
1525
1526                 if (page) {
1527                         /*
1528                          * If users can be writing to this page using arbitrary
1529                          * virtual addresses, take care about potential aliasing
1530                          * before reading the page on the kernel side.
1531                          */
1532                         if (mapping_writably_mapped(mapping))
1533                                 flush_dcache_page(page);
1534                         /*
1535                          * Mark the page accessed if we read the beginning.
1536                          */
1537                         if (!offset)
1538                                 mark_page_accessed(page);
1539                 } else {
1540                         page = ZERO_PAGE(0);
1541                         page_cache_get(page);
1542                 }
1543
1544                 /*
1545                  * Ok, we have the page, and it's up-to-date, so
1546                  * now we can copy it to user space...
1547                  *
1548                  * The actor routine returns how many bytes were actually used..
1549                  * NOTE! This may not be the same as how much of a user buffer
1550                  * we filled up (we may be padding etc), so we can only update
1551                  * "pos" here (the actor routine has to update the user buffer
1552                  * pointers and the remaining count).
1553                  */
1554                 ret = actor(desc, page, offset, nr);
1555                 offset += ret;
1556                 index += offset >> PAGE_CACHE_SHIFT;
1557                 offset &= ~PAGE_CACHE_MASK;
1558
1559                 page_cache_release(page);
1560                 if (ret != nr || !desc->count)
1561                         break;
1562
1563                 cond_resched();
1564         }
1565
1566         *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1567         file_accessed(filp);
1568 }
1569
1570 static ssize_t shmem_file_aio_read(struct kiocb *iocb,
1571                 const struct iovec *iov, unsigned long nr_segs, loff_t pos)
1572 {
1573         struct file *filp = iocb->ki_filp;
1574         ssize_t retval;
1575         unsigned long seg;
1576         size_t count;
1577         loff_t *ppos = &iocb->ki_pos;
1578
1579         retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1580         if (retval)
1581                 return retval;
1582
1583         for (seg = 0; seg < nr_segs; seg++) {
1584                 read_descriptor_t desc;
1585
1586                 desc.written = 0;
1587                 desc.arg.buf = iov[seg].iov_base;
1588                 desc.count = iov[seg].iov_len;
1589                 if (desc.count == 0)
1590                         continue;
1591                 desc.error = 0;
1592                 do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1593                 retval += desc.written;
1594                 if (desc.error) {
1595                         retval = retval ?: desc.error;
1596                         break;
1597                 }
1598                 if (desc.count > 0)
1599                         break;
1600         }
1601         return retval;
1602 }
1603
1604 static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
1605                                 struct pipe_inode_info *pipe, size_t len,
1606                                 unsigned int flags)
1607 {
1608         struct address_space *mapping = in->f_mapping;
1609         struct inode *inode = mapping->host;
1610         unsigned int loff, nr_pages, req_pages;
1611         struct page *pages[PIPE_DEF_BUFFERS];
1612         struct partial_page partial[PIPE_DEF_BUFFERS];
1613         struct page *page;
1614         pgoff_t index, end_index;
1615         loff_t isize, left;
1616         int error, page_nr;
1617         struct splice_pipe_desc spd = {
1618                 .pages = pages,
1619                 .partial = partial,
1620                 .nr_pages_max = PIPE_DEF_BUFFERS,
1621                 .flags = flags,
1622                 .ops = &page_cache_pipe_buf_ops,
1623                 .spd_release = spd_release_page,
1624         };
1625
1626         isize = i_size_read(inode);
1627         if (unlikely(*ppos >= isize))
1628                 return 0;
1629
1630         left = isize - *ppos;
1631         if (unlikely(left < len))
1632                 len = left;
1633
1634         if (splice_grow_spd(pipe, &spd))
1635                 return -ENOMEM;
1636
1637         index = *ppos >> PAGE_CACHE_SHIFT;
1638         loff = *ppos & ~PAGE_CACHE_MASK;
1639         req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1640         nr_pages = min(req_pages, pipe->buffers);
1641
1642         spd.nr_pages = find_get_pages_contig(mapping, index,
1643                                                 nr_pages, spd.pages);
1644         index += spd.nr_pages;
1645         error = 0;
1646
1647         while (spd.nr_pages < nr_pages) {
1648                 error = shmem_getpage(inode, index, &page, SGP_CACHE, NULL);
1649                 if (error)
1650                         break;
1651                 unlock_page(page);
1652                 spd.pages[spd.nr_pages++] = page;
1653                 index++;
1654         }
1655
1656         index = *ppos >> PAGE_CACHE_SHIFT;
1657         nr_pages = spd.nr_pages;
1658         spd.nr_pages = 0;
1659
1660         for (page_nr = 0; page_nr < nr_pages; page_nr++) {
1661                 unsigned int this_len;
1662
1663                 if (!len)
1664                         break;
1665
1666                 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
1667                 page = spd.pages[page_nr];
1668
1669                 if (!PageUptodate(page) || page->mapping != mapping) {
1670                         error = shmem_getpage(inode, index, &page,
1671                                                         SGP_CACHE, NULL);
1672                         if (error)
1673                                 break;
1674                         unlock_page(page);
1675                         page_cache_release(spd.pages[page_nr]);
1676                         spd.pages[page_nr] = page;
1677                 }
1678
1679                 isize = i_size_read(inode);
1680                 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1681                 if (unlikely(!isize || index > end_index))
1682                         break;
1683
1684                 if (end_index == index) {
1685                         unsigned int plen;
1686
1687                         plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1688                         if (plen <= loff)
1689                                 break;
1690
1691                         this_len = min(this_len, plen - loff);
1692                         len = this_len;
1693                 }
1694
1695                 spd.partial[page_nr].offset = loff;
1696                 spd.partial[page_nr].len = this_len;
1697                 len -= this_len;
1698                 loff = 0;
1699                 spd.nr_pages++;
1700                 index++;
1701         }
1702
1703         while (page_nr < nr_pages)
1704                 page_cache_release(spd.pages[page_nr++]);
1705
1706         if (spd.nr_pages)
1707                 error = splice_to_pipe(pipe, &spd);
1708
1709         splice_shrink_spd(&spd);
1710
1711         if (error > 0) {
1712                 *ppos += error;
1713                 file_accessed(in);
1714         }
1715         return error;
1716 }
1717
1718 static long shmem_fallocate(struct file *file, int mode, loff_t offset,
1719                                                          loff_t len)
1720 {
1721         struct inode *inode = file->f_path.dentry->d_inode;
1722         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1723         struct shmem_falloc shmem_falloc;
1724         pgoff_t start, index, end;
1725         int error;
1726
1727         mutex_lock(&inode->i_mutex);
1728
1729         if (mode & FALLOC_FL_PUNCH_HOLE) {
1730                 struct address_space *mapping = file->f_mapping;
1731                 loff_t unmap_start = round_up(offset, PAGE_SIZE);
1732                 loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1;
1733
1734                 if ((u64)unmap_end > (u64)unmap_start)
1735                         unmap_mapping_range(mapping, unmap_start,
1736                                             1 + unmap_end - unmap_start, 0);
1737                 shmem_truncate_range(inode, offset, offset + len - 1);
1738                 /* No need to unmap again: hole-punching leaves COWed pages */
1739                 error = 0;
1740                 goto out;
1741         }
1742
1743         /* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */
1744         error = inode_newsize_ok(inode, offset + len);
1745         if (error)
1746                 goto out;
1747
1748         start = offset >> PAGE_CACHE_SHIFT;
1749         end = (offset + len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1750         /* Try to avoid a swapstorm if len is impossible to satisfy */
1751         if (sbinfo->max_blocks && end - start > sbinfo->max_blocks) {
1752                 error = -ENOSPC;
1753                 goto out;
1754         }
1755
1756         shmem_falloc.start = start;
1757         shmem_falloc.next  = start;
1758         shmem_falloc.nr_falloced = 0;
1759         shmem_falloc.nr_unswapped = 0;
1760         spin_lock(&inode->i_lock);
1761         inode->i_private = &shmem_falloc;
1762         spin_unlock(&inode->i_lock);
1763
1764         for (index = start; index < end; index++) {
1765                 struct page *page;
1766
1767                 /*
1768                  * Good, the fallocate(2) manpage permits EINTR: we may have
1769                  * been interrupted because we are using up too much memory.
1770                  */
1771                 if (signal_pending(current))
1772                         error = -EINTR;
1773                 else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
1774                         error = -ENOMEM;
1775                 else
1776                         error = shmem_getpage(inode, index, &page, SGP_FALLOC,
1777                                                                         NULL);
1778                 if (error) {
1779                         /* Remove the !PageUptodate pages we added */
1780                         shmem_undo_range(inode,
1781                                 (loff_t)start << PAGE_CACHE_SHIFT,
1782                                 (loff_t)index << PAGE_CACHE_SHIFT, true);
1783                         goto undone;
1784                 }
1785
1786                 /*
1787                  * Inform shmem_writepage() how far we have reached.
1788                  * No need for lock or barrier: we have the page lock.
1789                  */
1790                 shmem_falloc.next++;
1791                 if (!PageUptodate(page))
1792                         shmem_falloc.nr_falloced++;
1793
1794                 /*
1795                  * If !PageUptodate, leave it that way so that freeable pages
1796                  * can be recognized if we need to rollback on error later.
1797                  * But set_page_dirty so that memory pressure will swap rather
1798                  * than free the pages we are allocating (and SGP_CACHE pages
1799                  * might still be clean: we now need to mark those dirty too).
1800                  */
1801                 set_page_dirty(page);
1802                 unlock_page(page);
1803                 page_cache_release(page);
1804                 cond_resched();
1805         }
1806
1807         if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
1808                 i_size_write(inode, offset + len);
1809         inode->i_ctime = CURRENT_TIME;
1810 undone:
1811         spin_lock(&inode->i_lock);
1812         inode->i_private = NULL;
1813         spin_unlock(&inode->i_lock);
1814 out:
1815         mutex_unlock(&inode->i_mutex);
1816         return error;
1817 }
1818
1819 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1820 {
1821         struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1822
1823         buf->f_type = TMPFS_MAGIC;
1824         buf->f_bsize = PAGE_CACHE_SIZE;
1825         buf->f_namelen = NAME_MAX;
1826         if (sbinfo->max_blocks) {
1827                 buf->f_blocks = sbinfo->max_blocks;
1828                 buf->f_bavail =
1829                 buf->f_bfree  = sbinfo->max_blocks -
1830                                 percpu_counter_sum(&sbinfo->used_blocks);
1831         }
1832         if (sbinfo->max_inodes) {
1833                 buf->f_files = sbinfo->max_inodes;
1834                 buf->f_ffree = sbinfo->free_inodes;
1835         }
1836         /* else leave those fields 0 like simple_statfs */
1837         return 0;
1838 }
1839
1840 /*
1841  * File creation. Allocate an inode, and we're done..
1842  */
1843 static int
1844 shmem_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
1845 {
1846         struct inode *inode;
1847         int error = -ENOSPC;
1848
1849         inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
1850         if (inode) {
1851                 error = security_inode_init_security(inode, dir,
1852                                                      &dentry->d_name,
1853                                                      shmem_initxattrs, NULL);
1854                 if (error) {
1855                         if (error != -EOPNOTSUPP) {
1856                                 iput(inode);
1857                                 return error;
1858                         }
1859                 }
1860 #ifdef CONFIG_TMPFS_POSIX_ACL
1861                 error = generic_acl_init(inode, dir);
1862                 if (error) {
1863                         iput(inode);
1864                         return error;
1865                 }
1866 #else
1867                 error = 0;
1868 #endif
1869                 dir->i_size += BOGO_DIRENT_SIZE;
1870                 dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1871                 d_instantiate(dentry, inode);
1872                 dget(dentry); /* Extra count - pin the dentry in core */
1873         }
1874         return error;
1875 }
1876
1877 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
1878 {
1879         int error;
1880
1881         if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1882                 return error;
1883         inc_nlink(dir);
1884         return 0;
1885 }
1886
1887 static int shmem_create(struct inode *dir, struct dentry *dentry, umode_t mode,
1888                 bool excl)
1889 {
1890         return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1891 }
1892
1893 /*
1894  * Link a file..
1895  */
1896 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1897 {
1898         struct inode *inode = old_dentry->d_inode;
1899         int ret;
1900
1901         /*
1902          * No ordinary (disk based) filesystem counts links as inodes;
1903          * but each new link needs a new dentry, pinning lowmem, and
1904          * tmpfs dentries cannot be pruned until they are unlinked.
1905          */
1906         ret = shmem_reserve_inode(inode->i_sb);
1907         if (ret)
1908                 goto out;
1909
1910         dir->i_size += BOGO_DIRENT_SIZE;
1911         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1912         inc_nlink(inode);
1913         ihold(inode);   /* New dentry reference */
1914         dget(dentry);           /* Extra pinning count for the created dentry */
1915         d_instantiate(dentry, inode);
1916 out:
1917         return ret;
1918 }
1919
1920 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
1921 {
1922         struct inode *inode = dentry->d_inode;
1923
1924         if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
1925                 shmem_free_inode(inode->i_sb);
1926
1927         dir->i_size -= BOGO_DIRENT_SIZE;
1928         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1929         drop_nlink(inode);
1930         dput(dentry);   /* Undo the count from "create" - this does all the work */
1931         return 0;
1932 }
1933
1934 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
1935 {
1936         if (!simple_empty(dentry))
1937                 return -ENOTEMPTY;
1938
1939         drop_nlink(dentry->d_inode);
1940         drop_nlink(dir);
1941         return shmem_unlink(dir, dentry);
1942 }
1943
1944 /*
1945  * The VFS layer already does all the dentry stuff for rename,
1946  * we just have to decrement the usage count for the target if
1947  * it exists so that the VFS layer correctly free's it when it
1948  * gets overwritten.
1949  */
1950 static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
1951 {
1952         struct inode *inode = old_dentry->d_inode;
1953         int they_are_dirs = S_ISDIR(inode->i_mode);
1954
1955         if (!simple_empty(new_dentry))
1956                 return -ENOTEMPTY;
1957
1958         if (new_dentry->d_inode) {
1959                 (void) shmem_unlink(new_dir, new_dentry);
1960                 if (they_are_dirs)
1961                         drop_nlink(old_dir);
1962         } else if (they_are_dirs) {
1963                 drop_nlink(old_dir);
1964                 inc_nlink(new_dir);
1965         }
1966
1967         old_dir->i_size -= BOGO_DIRENT_SIZE;
1968         new_dir->i_size += BOGO_DIRENT_SIZE;
1969         old_dir->i_ctime = old_dir->i_mtime =
1970         new_dir->i_ctime = new_dir->i_mtime =
1971         inode->i_ctime = CURRENT_TIME;
1972         return 0;
1973 }
1974
1975 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
1976 {
1977         int error;
1978         int len;
1979         struct inode *inode;
1980         struct page *page;
1981         char *kaddr;
1982         struct shmem_inode_info *info;
1983
1984         len = strlen(symname) + 1;
1985         if (len > PAGE_CACHE_SIZE)
1986                 return -ENAMETOOLONG;
1987
1988         inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE);
1989         if (!inode)
1990                 return -ENOSPC;
1991
1992         error = security_inode_init_security(inode, dir, &dentry->d_name,
1993                                              shmem_initxattrs, NULL);
1994         if (error) {
1995                 if (error != -EOPNOTSUPP) {
1996                         iput(inode);
1997                         return error;
1998                 }
1999                 error = 0;
2000         }
2001
2002         info = SHMEM_I(inode);
2003         inode->i_size = len-1;
2004         if (len <= SHORT_SYMLINK_LEN) {
2005                 info->symlink = kmemdup(symname, len, GFP_KERNEL);
2006                 if (!info->symlink) {
2007                         iput(inode);
2008                         return -ENOMEM;
2009                 }
2010                 inode->i_op = &shmem_short_symlink_operations;
2011         } else {
2012                 error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
2013                 if (error) {
2014                         iput(inode);
2015                         return error;
2016                 }
2017                 inode->i_mapping->a_ops = &shmem_aops;
2018                 inode->i_op = &shmem_symlink_inode_operations;
2019                 kaddr = kmap_atomic(page);
2020                 memcpy(kaddr, symname, len);
2021                 kunmap_atomic(kaddr);
2022                 SetPageUptodate(page);
2023                 set_page_dirty(page);
2024                 unlock_page(page);
2025                 page_cache_release(page);
2026         }
2027         dir->i_size += BOGO_DIRENT_SIZE;
2028         dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2029         d_instantiate(dentry, inode);
2030         dget(dentry);
2031         return 0;
2032 }
2033
2034 static void *shmem_follow_short_symlink(struct dentry *dentry, struct nameidata *nd)
2035 {
2036         nd_set_link(nd, SHMEM_I(dentry->d_inode)->symlink);
2037         return NULL;
2038 }
2039
2040 static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
2041 {
2042         struct page *page = NULL;
2043         int error = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
2044         nd_set_link(nd, error ? ERR_PTR(error) : kmap(page));
2045         if (page)
2046                 unlock_page(page);
2047         return page;
2048 }
2049
2050 static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
2051 {
2052         if (!IS_ERR(nd_get_link(nd))) {
2053                 struct page *page = cookie;
2054                 kunmap(page);
2055                 mark_page_accessed(page);
2056                 page_cache_release(page);
2057         }
2058 }
2059
2060 #ifdef CONFIG_TMPFS_XATTR
2061 /*
2062  * Superblocks without xattr inode operations may get some security.* xattr
2063  * support from the LSM "for free". As soon as we have any other xattrs
2064  * like ACLs, we also need to implement the security.* handlers at
2065  * filesystem level, though.
2066  */
2067
2068 /*
2069  * Callback for security_inode_init_security() for acquiring xattrs.
2070  */
2071 static int shmem_initxattrs(struct inode *inode,
2072                             const struct xattr *xattr_array,
2073                             void *fs_info)
2074 {
2075         struct shmem_inode_info *info = SHMEM_I(inode);
2076         const struct xattr *xattr;
2077         struct simple_xattr *new_xattr;
2078         size_t len;
2079
2080         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
2081                 new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len);
2082                 if (!new_xattr)
2083                         return -ENOMEM;
2084
2085                 len = strlen(xattr->name) + 1;
2086                 new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
2087                                           GFP_KERNEL);
2088                 if (!new_xattr->name) {
2089                         kfree(new_xattr);
2090                         return -ENOMEM;
2091                 }
2092
2093                 memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
2094                        XATTR_SECURITY_PREFIX_LEN);
2095                 memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
2096                        xattr->name, len);
2097
2098                 simple_xattr_list_add(&info->xattrs, new_xattr);
2099         }
2100
2101         return 0;
2102 }
2103
2104 static const struct xattr_handler *shmem_xattr_handlers[] = {
2105 #ifdef CONFIG_TMPFS_POSIX_ACL
2106         &generic_acl_access_handler,
2107         &generic_acl_default_handler,
2108 #endif
2109         NULL
2110 };
2111
2112 static int shmem_xattr_validate(const char *name)
2113 {
2114         struct { const char *prefix; size_t len; } arr[] = {
2115                 { XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN },
2116                 { XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN }
2117         };
2118         int i;
2119
2120         for (i = 0; i < ARRAY_SIZE(arr); i++) {
2121                 size_t preflen = arr[i].len;
2122                 if (strncmp(name, arr[i].prefix, preflen) == 0) {
2123                         if (!name[preflen])
2124                                 return -EINVAL;
2125                         return 0;
2126                 }
2127         }
2128         return -EOPNOTSUPP;
2129 }
2130
2131 static ssize_t shmem_getxattr(struct dentry *dentry, const char *name,
2132                               void *buffer, size_t size)
2133 {
2134         struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2135         int err;
2136
2137         /*
2138          * If this is a request for a synthetic attribute in the system.*
2139          * namespace use the generic infrastructure to resolve a handler
2140          * for it via sb->s_xattr.
2141          */
2142         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2143                 return generic_getxattr(dentry, name, buffer, size);
2144
2145         err = shmem_xattr_validate(name);
2146         if (err)
2147                 return err;
2148
2149         return simple_xattr_get(&info->xattrs, name, buffer, size);
2150 }
2151
2152 static int shmem_setxattr(struct dentry *dentry, const char *name,
2153                           const void *value, size_t size, int flags)
2154 {
2155         struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2156         int err;
2157
2158         /*
2159          * If this is a request for a synthetic attribute in the system.*
2160          * namespace use the generic infrastructure to resolve a handler
2161          * for it via sb->s_xattr.
2162          */
2163         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2164                 return generic_setxattr(dentry, name, value, size, flags);
2165
2166         err = shmem_xattr_validate(name);
2167         if (err)
2168                 return err;
2169
2170         return simple_xattr_set(&info->xattrs, name, value, size, flags);
2171 }
2172
2173 static int shmem_removexattr(struct dentry *dentry, const char *name)
2174 {
2175         struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2176         int err;
2177
2178         /*
2179          * If this is a request for a synthetic attribute in the system.*
2180          * namespace use the generic infrastructure to resolve a handler
2181          * for it via sb->s_xattr.
2182          */
2183         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2184                 return generic_removexattr(dentry, name);
2185
2186         err = shmem_xattr_validate(name);
2187         if (err)
2188                 return err;
2189
2190         return simple_xattr_remove(&info->xattrs, name);
2191 }
2192
2193 static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
2194 {
2195         struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2196         return simple_xattr_list(&info->xattrs, buffer, size);
2197 }
2198 #endif /* CONFIG_TMPFS_XATTR */
2199
2200 static const struct inode_operations shmem_short_symlink_operations = {
2201         .readlink       = generic_readlink,
2202         .follow_link    = shmem_follow_short_symlink,
2203 #ifdef CONFIG_TMPFS_XATTR
2204         .setxattr       = shmem_setxattr,
2205         .getxattr       = shmem_getxattr,
2206         .listxattr      = shmem_listxattr,
2207         .removexattr    = shmem_removexattr,
2208 #endif
2209 };
2210
2211 static const struct inode_operations shmem_symlink_inode_operations = {
2212         .readlink       = generic_readlink,
2213         .follow_link    = shmem_follow_link,
2214         .put_link       = shmem_put_link,
2215 #ifdef CONFIG_TMPFS_XATTR
2216         .setxattr       = shmem_setxattr,
2217         .getxattr       = shmem_getxattr,
2218         .listxattr      = shmem_listxattr,
2219         .removexattr    = shmem_removexattr,
2220 #endif
2221 };
2222
2223 static struct dentry *shmem_get_parent(struct dentry *child)
2224 {
2225         return ERR_PTR(-ESTALE);
2226 }
2227
2228 static int shmem_match(struct inode *ino, void *vfh)
2229 {
2230         __u32 *fh = vfh;
2231         __u64 inum = fh[2];
2232         inum = (inum << 32) | fh[1];
2233         return ino->i_ino == inum && fh[0] == ino->i_generation;
2234 }
2235
2236 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
2237                 struct fid *fid, int fh_len, int fh_type)
2238 {
2239         struct inode *inode;
2240         struct dentry *dentry = NULL;
2241         u64 inum;
2242
2243         if (fh_len < 3)
2244                 return NULL;
2245
2246         inum = fid->raw[2];
2247         inum = (inum << 32) | fid->raw[1];
2248
2249         inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
2250                         shmem_match, fid->raw);
2251         if (inode) {
2252                 dentry = d_find_alias(inode);
2253                 iput(inode);
2254         }
2255
2256         return dentry;
2257 }
2258
2259 static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len,
2260                                 struct inode *parent)
2261 {
2262         if (*len < 3) {
2263                 *len = 3;
2264                 return 255;
2265         }
2266
2267         if (inode_unhashed(inode)) {
2268                 /* Unfortunately insert_inode_hash is not idempotent,
2269                  * so as we hash inodes here rather than at creation
2270                  * time, we need a lock to ensure we only try
2271                  * to do it once
2272                  */
2273                 static DEFINE_SPINLOCK(lock);
2274                 spin_lock(&lock);
2275                 if (inode_unhashed(inode))
2276                         __insert_inode_hash(inode,
2277                                             inode->i_ino + inode->i_generation);
2278                 spin_unlock(&lock);
2279         }
2280
2281         fh[0] = inode->i_generation;
2282         fh[1] = inode->i_ino;
2283         fh[2] = ((__u64)inode->i_ino) >> 32;
2284
2285         *len = 3;
2286         return 1;
2287 }
2288
2289 static const struct export_operations shmem_export_ops = {
2290         .get_parent     = shmem_get_parent,
2291         .encode_fh      = shmem_encode_fh,
2292         .fh_to_dentry   = shmem_fh_to_dentry,
2293 };
2294
2295 static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
2296                                bool remount)
2297 {
2298         char *this_char, *value, *rest;
2299         uid_t uid;
2300         gid_t gid;
2301
2302         while (options != NULL) {
2303                 this_char = options;
2304                 for (;;) {
2305                         /*
2306                          * NUL-terminate this option: unfortunately,
2307                          * mount options form a comma-separated list,
2308                          * but mpol's nodelist may also contain commas.
2309                          */
2310                         options = strchr(options, ',');
2311                         if (options == NULL)
2312                                 break;
2313                         options++;
2314                         if (!isdigit(*options)) {
2315                                 options[-1] = '\0';
2316                                 break;
2317                         }
2318                 }
2319                 if (!*this_char)
2320                         continue;
2321                 if ((value = strchr(this_char,'=')) != NULL) {
2322                         *value++ = 0;
2323                 } else {
2324                         printk(KERN_ERR
2325                             "tmpfs: No value for mount option '%s'\n",
2326                             this_char);
2327                         return 1;
2328                 }
2329
2330                 if (!strcmp(this_char,"size")) {
2331                         unsigned long long size;
2332                         size = memparse(value,&rest);
2333                         if (*rest == '%') {
2334                                 size <<= PAGE_SHIFT;
2335                                 size *= totalram_pages;
2336                                 do_div(size, 100);
2337                                 rest++;
2338                         }
2339                         if (*rest)
2340                                 goto bad_val;
2341                         sbinfo->max_blocks =
2342                                 DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
2343                 } else if (!strcmp(this_char,"nr_blocks")) {
2344                         sbinfo->max_blocks = memparse(value, &rest);
2345                         if (*rest)
2346                                 goto bad_val;
2347                 } else if (!strcmp(this_char,"nr_inodes")) {
2348                         sbinfo->max_inodes = memparse(value, &rest);
2349                         if (*rest)
2350                                 goto bad_val;
2351                 } else if (!strcmp(this_char,"mode")) {
2352                         if (remount)
2353                                 continue;
2354                         sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
2355                         if (*rest)
2356                                 goto bad_val;
2357                 } else if (!strcmp(this_char,"uid")) {
2358                         if (remount)
2359                                 continue;
2360                         uid = simple_strtoul(value, &rest, 0);
2361                         if (*rest)
2362                                 goto bad_val;
2363                         sbinfo->uid = make_kuid(current_user_ns(), uid);
2364                         if (!uid_valid(sbinfo->uid))
2365                                 goto bad_val;
2366                 } else if (!strcmp(this_char,"gid")) {
2367                         if (remount)
2368                                 continue;
2369                         gid = simple_strtoul(value, &rest, 0);
2370                         if (*rest)
2371                                 goto bad_val;
2372                         sbinfo->gid = make_kgid(current_user_ns(), gid);
2373                         if (!gid_valid(sbinfo->gid))
2374                                 goto bad_val;
2375                 } else if (!strcmp(this_char,"mpol")) {
2376                         if (mpol_parse_str(value, &sbinfo->mpol, 1))
2377                                 goto bad_val;
2378                 } else {
2379                         printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2380                                this_char);
2381                         return 1;
2382                 }
2383         }
2384         return 0;
2385
2386 bad_val:
2387         printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2388                value, this_char);
2389         return 1;
2390
2391 }
2392
2393 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2394 {
2395         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2396         struct shmem_sb_info config = *sbinfo;
2397         unsigned long inodes;
2398         int error = -EINVAL;
2399
2400         if (shmem_parse_options(data, &config, true))
2401                 return error;
2402
2403         spin_lock(&sbinfo->stat_lock);
2404         inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2405         if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0)
2406                 goto out;
2407         if (config.max_inodes < inodes)
2408                 goto out;
2409         /*
2410          * Those tests disallow limited->unlimited while any are in use;
2411          * but we must separately disallow unlimited->limited, because
2412          * in that case we have no record of how much is already in use.
2413          */
2414         if (config.max_blocks && !sbinfo->max_blocks)
2415                 goto out;
2416         if (config.max_inodes && !sbinfo->max_inodes)
2417                 goto out;
2418
2419         error = 0;
2420         sbinfo->max_blocks  = config.max_blocks;
2421         sbinfo->max_inodes  = config.max_inodes;
2422         sbinfo->free_inodes = config.max_inodes - inodes;
2423
2424         mpol_put(sbinfo->mpol);
2425         sbinfo->mpol        = config.mpol;      /* transfers initial ref */
2426 out:
2427         spin_unlock(&sbinfo->stat_lock);
2428         return error;
2429 }
2430
2431 static int shmem_show_options(struct seq_file *seq, struct dentry *root)
2432 {
2433         struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb);
2434
2435         if (sbinfo->max_blocks != shmem_default_max_blocks())
2436                 seq_printf(seq, ",size=%luk",
2437                         sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
2438         if (sbinfo->max_inodes != shmem_default_max_inodes())
2439                 seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
2440         if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
2441                 seq_printf(seq, ",mode=%03ho", sbinfo->mode);
2442         if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
2443                 seq_printf(seq, ",uid=%u",
2444                                 from_kuid_munged(&init_user_ns, sbinfo->uid));
2445         if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
2446                 seq_printf(seq, ",gid=%u",
2447                                 from_kgid_munged(&init_user_ns, sbinfo->gid));
2448         shmem_show_mpol(seq, sbinfo->mpol);
2449         return 0;
2450 }
2451 #endif /* CONFIG_TMPFS */
2452
2453 static void shmem_put_super(struct super_block *sb)
2454 {
2455         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2456
2457         percpu_counter_destroy(&sbinfo->used_blocks);
2458         kfree(sbinfo);
2459         sb->s_fs_info = NULL;
2460 }
2461
2462 int shmem_fill_super(struct super_block *sb, void *data, int silent)
2463 {
2464         struct inode *inode;
2465         struct shmem_sb_info *sbinfo;
2466         int err = -ENOMEM;
2467
2468         /* Round up to L1_CACHE_BYTES to resist false sharing */
2469         sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
2470                                 L1_CACHE_BYTES), GFP_KERNEL);
2471         if (!sbinfo)
2472                 return -ENOMEM;
2473
2474         sbinfo->mode = S_IRWXUGO | S_ISVTX;
2475         sbinfo->uid = current_fsuid();
2476         sbinfo->gid = current_fsgid();
2477         sb->s_fs_info = sbinfo;
2478
2479 #ifdef CONFIG_TMPFS
2480         /*
2481          * Per default we only allow half of the physical ram per
2482          * tmpfs instance, limiting inodes to one per page of lowmem;
2483          * but the internal instance is left unlimited.
2484          */
2485         if (!(sb->s_flags & MS_NOUSER)) {
2486                 sbinfo->max_blocks = shmem_default_max_blocks();
2487                 sbinfo->max_inodes = shmem_default_max_inodes();
2488                 if (shmem_parse_options(data, sbinfo, false)) {
2489                         err = -EINVAL;
2490                         goto failed;
2491                 }
2492         }
2493         sb->s_export_op = &shmem_export_ops;
2494         sb->s_flags |= MS_NOSEC;
2495 #else
2496         sb->s_flags |= MS_NOUSER;
2497 #endif
2498
2499         spin_lock_init(&sbinfo->stat_lock);
2500         if (percpu_counter_init(&sbinfo->used_blocks, 0))
2501                 goto failed;
2502         sbinfo->free_inodes = sbinfo->max_inodes;
2503
2504         sb->s_maxbytes = MAX_LFS_FILESIZE;
2505         sb->s_blocksize = PAGE_CACHE_SIZE;
2506         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2507         sb->s_magic = TMPFS_MAGIC;
2508         sb->s_op = &shmem_ops;
2509         sb->s_time_gran = 1;
2510 #ifdef CONFIG_TMPFS_XATTR
2511         sb->s_xattr = shmem_xattr_handlers;
2512 #endif
2513 #ifdef CONFIG_TMPFS_POSIX_ACL
2514         sb->s_flags |= MS_POSIXACL;
2515 #endif
2516
2517         inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
2518         if (!inode)
2519                 goto failed;
2520         inode->i_uid = sbinfo->uid;
2521         inode->i_gid = sbinfo->gid;
2522         sb->s_root = d_make_root(inode);
2523         if (!sb->s_root)
2524                 goto failed;
2525         return 0;
2526
2527 failed:
2528         shmem_put_super(sb);
2529         return err;
2530 }
2531
2532 static struct kmem_cache *shmem_inode_cachep;
2533
2534 static struct inode *shmem_alloc_inode(struct super_block *sb)
2535 {
2536         struct shmem_inode_info *info;
2537         info = kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2538         if (!info)
2539                 return NULL;
2540         return &info->vfs_inode;
2541 }
2542
2543 static void shmem_destroy_callback(struct rcu_head *head)
2544 {
2545         struct inode *inode = container_of(head, struct inode, i_rcu);
2546         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2547 }
2548
2549 static void shmem_destroy_inode(struct inode *inode)
2550 {
2551         if (S_ISREG(inode->i_mode))
2552                 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2553         call_rcu(&inode->i_rcu, shmem_destroy_callback);
2554 }
2555
2556 static void shmem_init_inode(void *foo)
2557 {
2558         struct shmem_inode_info *info = foo;
2559         inode_init_once(&info->vfs_inode);
2560 }
2561
2562 static int shmem_init_inodecache(void)
2563 {
2564         shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2565                                 sizeof(struct shmem_inode_info),
2566                                 0, SLAB_PANIC, shmem_init_inode);
2567         return 0;
2568 }
2569
2570 static void shmem_destroy_inodecache(void)
2571 {
2572         kmem_cache_destroy(shmem_inode_cachep);
2573 }
2574
2575 static const struct address_space_operations shmem_aops = {
2576         .writepage      = shmem_writepage,
2577         .set_page_dirty = __set_page_dirty_no_writeback,
2578 #ifdef CONFIG_TMPFS
2579         .write_begin    = shmem_write_begin,
2580         .write_end      = shmem_write_end,
2581 #endif
2582         .migratepage    = migrate_page,
2583         .error_remove_page = generic_error_remove_page,
2584 };
2585
2586 static const struct file_operations shmem_file_operations = {
2587         .mmap           = shmem_mmap,
2588 #ifdef CONFIG_TMPFS
2589         .llseek         = generic_file_llseek,
2590         .read           = do_sync_read,
2591         .write          = do_sync_write,
2592         .aio_read       = shmem_file_aio_read,
2593         .aio_write      = generic_file_aio_write,
2594         .fsync          = noop_fsync,
2595         .splice_read    = shmem_file_splice_read,
2596         .splice_write   = generic_file_splice_write,
2597         .fallocate      = shmem_fallocate,
2598 #endif
2599 };
2600
2601 static const struct inode_operations shmem_inode_operations = {
2602         .setattr        = shmem_setattr,
2603 #ifdef CONFIG_TMPFS_XATTR
2604         .setxattr       = shmem_setxattr,
2605         .getxattr       = shmem_getxattr,
2606         .listxattr      = shmem_listxattr,
2607         .removexattr    = shmem_removexattr,
2608 #endif
2609 };
2610
2611 static const struct inode_operations shmem_dir_inode_operations = {
2612 #ifdef CONFIG_TMPFS
2613         .create         = shmem_create,
2614         .lookup         = simple_lookup,
2615         .link           = shmem_link,
2616         .unlink         = shmem_unlink,
2617         .symlink        = shmem_symlink,
2618         .mkdir          = shmem_mkdir,
2619         .rmdir          = shmem_rmdir,
2620         .mknod          = shmem_mknod,
2621         .rename         = shmem_rename,
2622 #endif
2623 #ifdef CONFIG_TMPFS_XATTR
2624         .setxattr       = shmem_setxattr,
2625         .getxattr       = shmem_getxattr,
2626         .listxattr      = shmem_listxattr,
2627         .removexattr    = shmem_removexattr,
2628 #endif
2629 #ifdef CONFIG_TMPFS_POSIX_ACL
2630         .setattr        = shmem_setattr,
2631 #endif
2632 };
2633
2634 static const struct inode_operations shmem_special_inode_operations = {
2635 #ifdef CONFIG_TMPFS_XATTR
2636         .setxattr       = shmem_setxattr,
2637         .getxattr       = shmem_getxattr,
2638         .listxattr      = shmem_listxattr,
2639         .removexattr    = shmem_removexattr,
2640 #endif
2641 #ifdef CONFIG_TMPFS_POSIX_ACL
2642         .setattr        = shmem_setattr,
2643 #endif
2644 };
2645
2646 static const struct super_operations shmem_ops = {
2647         .alloc_inode    = shmem_alloc_inode,
2648         .destroy_inode  = shmem_destroy_inode,
2649 #ifdef CONFIG_TMPFS
2650         .statfs         = shmem_statfs,
2651         .remount_fs     = shmem_remount_fs,
2652         .show_options   = shmem_show_options,
2653 #endif
2654         .evict_inode    = shmem_evict_inode,
2655         .drop_inode     = generic_delete_inode,
2656         .put_super      = shmem_put_super,
2657 };
2658
2659 static const struct vm_operations_struct shmem_vm_ops = {
2660         .fault          = shmem_fault,
2661 #ifdef CONFIG_NUMA
2662         .set_policy     = shmem_set_policy,
2663         .get_policy     = shmem_get_policy,
2664 #endif
2665         .remap_pages    = generic_file_remap_pages,
2666 };
2667
2668 static struct dentry *shmem_mount(struct file_system_type *fs_type,
2669         int flags, const char *dev_name, void *data)
2670 {
2671         return mount_nodev(fs_type, flags, data, shmem_fill_super);
2672 }
2673
2674 static struct file_system_type shmem_fs_type = {
2675         .owner          = THIS_MODULE,
2676         .name           = "tmpfs",
2677         .mount          = shmem_mount,
2678         .kill_sb        = kill_litter_super,
2679 };
2680
2681 int __init shmem_init(void)
2682 {
2683         int error;
2684
2685         error = bdi_init(&shmem_backing_dev_info);
2686         if (error)
2687                 goto out4;
2688
2689         error = shmem_init_inodecache();
2690         if (error)
2691                 goto out3;
2692
2693         error = register_filesystem(&shmem_fs_type);
2694         if (error) {
2695                 printk(KERN_ERR "Could not register tmpfs\n");
2696                 goto out2;
2697         }
2698
2699         shm_mnt = vfs_kern_mount(&shmem_fs_type, MS_NOUSER,
2700                                  shmem_fs_type.name, NULL);
2701         if (IS_ERR(shm_mnt)) {
2702                 error = PTR_ERR(shm_mnt);
2703                 printk(KERN_ERR "Could not kern_mount tmpfs\n");
2704                 goto out1;
2705         }
2706         return 0;
2707
2708 out1:
2709         unregister_filesystem(&shmem_fs_type);
2710 out2:
2711         shmem_destroy_inodecache();
2712 out3:
2713         bdi_destroy(&shmem_backing_dev_info);
2714 out4:
2715         shm_mnt = ERR_PTR(error);
2716         return error;
2717 }
2718
2719 #else /* !CONFIG_SHMEM */
2720
2721 /*
2722  * tiny-shmem: simple shmemfs and tmpfs using ramfs code
2723  *
2724  * This is intended for small system where the benefits of the full
2725  * shmem code (swap-backed and resource-limited) are outweighed by
2726  * their complexity. On systems without swap this code should be
2727  * effectively equivalent, but much lighter weight.
2728  */
2729
2730 #include <linux/ramfs.h>
2731
2732 static struct file_system_type shmem_fs_type = {
2733         .name           = "tmpfs",
2734         .mount          = ramfs_mount,
2735         .kill_sb        = kill_litter_super,
2736 };
2737
2738 int __init shmem_init(void)
2739 {
2740         BUG_ON(register_filesystem(&shmem_fs_type) != 0);
2741
2742         shm_mnt = kern_mount(&shmem_fs_type);
2743         BUG_ON(IS_ERR(shm_mnt));
2744
2745         return 0;
2746 }
2747
2748 int shmem_unuse(swp_entry_t swap, struct page *page)
2749 {
2750         return 0;
2751 }
2752
2753 int shmem_lock(struct file *file, int lock, struct user_struct *user)
2754 {
2755         return 0;
2756 }
2757
2758 void shmem_unlock_mapping(struct address_space *mapping)
2759 {
2760 }
2761
2762 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
2763 {
2764         truncate_inode_pages_range(inode->i_mapping, lstart, lend);
2765 }
2766 EXPORT_SYMBOL_GPL(shmem_truncate_range);
2767
2768 #define shmem_vm_ops                            generic_file_vm_ops
2769 #define shmem_file_operations                   ramfs_file_operations
2770 #define shmem_get_inode(sb, dir, mode, dev, flags)      ramfs_get_inode(sb, dir, mode, dev)
2771 #define shmem_acct_size(flags, size)            0
2772 #define shmem_unacct_size(flags, size)          do {} while (0)
2773
2774 #endif /* CONFIG_SHMEM */
2775
2776 /* common code */
2777
2778 /**
2779  * shmem_file_setup - get an unlinked file living in tmpfs
2780  * @name: name for dentry (to be seen in /proc/<pid>/maps
2781  * @size: size to be set for the file
2782  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
2783  */
2784 struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
2785 {
2786         int error;
2787         struct file *file;
2788         struct inode *inode;
2789         struct path path;
2790         struct dentry *root;
2791         struct qstr this;
2792
2793         if (IS_ERR(shm_mnt))
2794                 return (void *)shm_mnt;
2795
2796         if (size < 0 || size > MAX_LFS_FILESIZE)
2797                 return ERR_PTR(-EINVAL);
2798
2799         if (shmem_acct_size(flags, size))
2800                 return ERR_PTR(-ENOMEM);
2801
2802         error = -ENOMEM;
2803         this.name = name;
2804         this.len = strlen(name);
2805         this.hash = 0; /* will go */
2806         root = shm_mnt->mnt_root;
2807         path.dentry = d_alloc(root, &this);
2808         if (!path.dentry)
2809                 goto put_memory;
2810         path.mnt = mntget(shm_mnt);
2811
2812         error = -ENOSPC;
2813         inode = shmem_get_inode(root->d_sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
2814         if (!inode)
2815                 goto put_dentry;
2816
2817         d_instantiate(path.dentry, inode);
2818         inode->i_size = size;
2819         clear_nlink(inode);     /* It is unlinked */
2820 #ifndef CONFIG_MMU
2821         error = ramfs_nommu_expand_for_mapping(inode, size);
2822         if (error)
2823                 goto put_dentry;
2824 #endif
2825
2826         error = -ENFILE;
2827         file = alloc_file(&path, FMODE_WRITE | FMODE_READ,
2828                   &shmem_file_operations);
2829         if (!file)
2830                 goto put_dentry;
2831
2832         return file;
2833
2834 put_dentry:
2835         path_put(&path);
2836 put_memory:
2837         shmem_unacct_size(flags, size);
2838         return ERR_PTR(error);
2839 }
2840 EXPORT_SYMBOL_GPL(shmem_file_setup);
2841
2842 /**
2843  * shmem_zero_setup - setup a shared anonymous mapping
2844  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2845  */
2846 int shmem_zero_setup(struct vm_area_struct *vma)
2847 {
2848         struct file *file;
2849         loff_t size = vma->vm_end - vma->vm_start;
2850
2851         file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2852         if (IS_ERR(file))
2853                 return PTR_ERR(file);
2854
2855         if (vma->vm_file)
2856                 fput(vma->vm_file);
2857         vma->vm_file = file;
2858         vma->vm_ops = &shmem_vm_ops;
2859         return 0;
2860 }
2861
2862 /**
2863  * shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags.
2864  * @mapping:    the page's address_space
2865  * @index:      the page index
2866  * @gfp:        the page allocator flags to use if allocating
2867  *
2868  * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)",
2869  * with any new page allocations done using the specified allocation flags.
2870  * But read_cache_page_gfp() uses the ->readpage() method: which does not
2871  * suit tmpfs, since it may have pages in swapcache, and needs to find those
2872  * for itself; although drivers/gpu/drm i915 and ttm rely upon this support.
2873  *
2874  * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in
2875  * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily.
2876  */
2877 struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
2878                                          pgoff_t index, gfp_t gfp)
2879 {
2880 #ifdef CONFIG_SHMEM
2881         struct inode *inode = mapping->host;
2882         struct page *page;
2883         int error;
2884
2885         BUG_ON(mapping->a_ops != &shmem_aops);
2886         error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE, gfp, NULL);
2887         if (error)
2888                 page = ERR_PTR(error);
2889         else
2890                 unlock_page(page);
2891         return page;
2892 #else
2893         /*
2894          * The tiny !SHMEM case uses ramfs without swap
2895          */
2896         return read_cache_page_gfp(mapping, index, gfp);
2897 #endif
2898 }
2899 EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);