Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...
[platform/adaptation/renesas_rcar/renesas_kernel.git] / mm / shmem.c
1 /*
2  * Resizable virtual memory filesystem for Linux.
3  *
4  * Copyright (C) 2000 Linus Torvalds.
5  *               2000 Transmeta Corp.
6  *               2000-2001 Christoph Rohland
7  *               2000-2001 SAP AG
8  *               2002 Red Hat Inc.
9  * Copyright (C) 2002-2011 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 struct shmem_xattr {
81         struct list_head list;  /* anchored by shmem_inode_info->xattr_list */
82         char *name;             /* xattr name */
83         size_t size;
84         char value[0];
85 };
86
87 /*
88  * shmem_fallocate and shmem_writepage communicate via inode->i_private
89  * (with i_mutex making sure that it has only one user at a time):
90  * we would prefer not to enlarge the shmem inode just for that.
91  */
92 struct shmem_falloc {
93         pgoff_t start;          /* start of range currently being fallocated */
94         pgoff_t next;           /* the next page offset to be fallocated */
95         pgoff_t nr_falloced;    /* how many new pages have been fallocated */
96         pgoff_t nr_unswapped;   /* how often writepage refused to swap out */
97 };
98
99 /* Flag allocation requirements to shmem_getpage */
100 enum sgp_type {
101         SGP_READ,       /* don't exceed i_size, don't allocate page */
102         SGP_CACHE,      /* don't exceed i_size, may allocate page */
103         SGP_DIRTY,      /* like SGP_CACHE, but set new page dirty */
104         SGP_WRITE,      /* may exceed i_size, may allocate !Uptodate page */
105         SGP_FALLOC,     /* like SGP_WRITE, but make existing page Uptodate */
106 };
107
108 #ifdef CONFIG_TMPFS
109 static unsigned long shmem_default_max_blocks(void)
110 {
111         return totalram_pages / 2;
112 }
113
114 static unsigned long shmem_default_max_inodes(void)
115 {
116         return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
117 }
118 #endif
119
120 static bool shmem_should_replace_page(struct page *page, gfp_t gfp);
121 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
122                                 struct shmem_inode_info *info, pgoff_t index);
123 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
124         struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type);
125
126 static inline int shmem_getpage(struct inode *inode, pgoff_t index,
127         struct page **pagep, enum sgp_type sgp, int *fault_type)
128 {
129         return shmem_getpage_gfp(inode, index, pagep, sgp,
130                         mapping_gfp_mask(inode->i_mapping), fault_type);
131 }
132
133 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
134 {
135         return sb->s_fs_info;
136 }
137
138 /*
139  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
140  * for shared memory and for shared anonymous (/dev/zero) mappings
141  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
142  * consistent with the pre-accounting of private mappings ...
143  */
144 static inline int shmem_acct_size(unsigned long flags, loff_t size)
145 {
146         return (flags & VM_NORESERVE) ?
147                 0 : security_vm_enough_memory_mm(current->mm, VM_ACCT(size));
148 }
149
150 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
151 {
152         if (!(flags & VM_NORESERVE))
153                 vm_unacct_memory(VM_ACCT(size));
154 }
155
156 /*
157  * ... whereas tmpfs objects are accounted incrementally as
158  * pages are allocated, in order to allow huge sparse files.
159  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
160  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
161  */
162 static inline int shmem_acct_block(unsigned long flags)
163 {
164         return (flags & VM_NORESERVE) ?
165                 security_vm_enough_memory_mm(current->mm, VM_ACCT(PAGE_CACHE_SIZE)) : 0;
166 }
167
168 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
169 {
170         if (flags & VM_NORESERVE)
171                 vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
172 }
173
174 static const struct super_operations shmem_ops;
175 static const struct address_space_operations shmem_aops;
176 static const struct file_operations shmem_file_operations;
177 static const struct inode_operations shmem_inode_operations;
178 static const struct inode_operations shmem_dir_inode_operations;
179 static const struct inode_operations shmem_special_inode_operations;
180 static const struct vm_operations_struct shmem_vm_ops;
181
182 static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
183         .ra_pages       = 0,    /* No readahead */
184         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
185 };
186
187 static LIST_HEAD(shmem_swaplist);
188 static DEFINE_MUTEX(shmem_swaplist_mutex);
189
190 static int shmem_reserve_inode(struct super_block *sb)
191 {
192         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
193         if (sbinfo->max_inodes) {
194                 spin_lock(&sbinfo->stat_lock);
195                 if (!sbinfo->free_inodes) {
196                         spin_unlock(&sbinfo->stat_lock);
197                         return -ENOSPC;
198                 }
199                 sbinfo->free_inodes--;
200                 spin_unlock(&sbinfo->stat_lock);
201         }
202         return 0;
203 }
204
205 static void shmem_free_inode(struct super_block *sb)
206 {
207         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
208         if (sbinfo->max_inodes) {
209                 spin_lock(&sbinfo->stat_lock);
210                 sbinfo->free_inodes++;
211                 spin_unlock(&sbinfo->stat_lock);
212         }
213 }
214
215 /**
216  * shmem_recalc_inode - recalculate the block usage of an inode
217  * @inode: inode to recalc
218  *
219  * We have to calculate the free blocks since the mm can drop
220  * undirtied hole pages behind our back.
221  *
222  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
223  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
224  *
225  * It has to be called with the spinlock held.
226  */
227 static void shmem_recalc_inode(struct inode *inode)
228 {
229         struct shmem_inode_info *info = SHMEM_I(inode);
230         long freed;
231
232         freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
233         if (freed > 0) {
234                 struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
235                 if (sbinfo->max_blocks)
236                         percpu_counter_add(&sbinfo->used_blocks, -freed);
237                 info->alloced -= freed;
238                 inode->i_blocks -= freed * BLOCKS_PER_PAGE;
239                 shmem_unacct_blocks(info->flags, freed);
240         }
241 }
242
243 /*
244  * Replace item expected in radix tree by a new item, while holding tree lock.
245  */
246 static int shmem_radix_tree_replace(struct address_space *mapping,
247                         pgoff_t index, void *expected, void *replacement)
248 {
249         void **pslot;
250         void *item = NULL;
251
252         VM_BUG_ON(!expected);
253         pslot = radix_tree_lookup_slot(&mapping->page_tree, index);
254         if (pslot)
255                 item = radix_tree_deref_slot_protected(pslot,
256                                                         &mapping->tree_lock);
257         if (item != expected)
258                 return -ENOENT;
259         if (replacement)
260                 radix_tree_replace_slot(pslot, replacement);
261         else
262                 radix_tree_delete(&mapping->page_tree, index);
263         return 0;
264 }
265
266 /*
267  * Like add_to_page_cache_locked, but error if expected item has gone.
268  */
269 static int shmem_add_to_page_cache(struct page *page,
270                                    struct address_space *mapping,
271                                    pgoff_t index, gfp_t gfp, void *expected)
272 {
273         int error = 0;
274
275         VM_BUG_ON(!PageLocked(page));
276         VM_BUG_ON(!PageSwapBacked(page));
277
278         if (!expected)
279                 error = radix_tree_preload(gfp & GFP_RECLAIM_MASK);
280         if (!error) {
281                 page_cache_get(page);
282                 page->mapping = mapping;
283                 page->index = index;
284
285                 spin_lock_irq(&mapping->tree_lock);
286                 if (!expected)
287                         error = radix_tree_insert(&mapping->page_tree,
288                                                         index, page);
289                 else
290                         error = shmem_radix_tree_replace(mapping, index,
291                                                         expected, page);
292                 if (!error) {
293                         mapping->nrpages++;
294                         __inc_zone_page_state(page, NR_FILE_PAGES);
295                         __inc_zone_page_state(page, NR_SHMEM);
296                         spin_unlock_irq(&mapping->tree_lock);
297                 } else {
298                         page->mapping = NULL;
299                         spin_unlock_irq(&mapping->tree_lock);
300                         page_cache_release(page);
301                 }
302                 if (!expected)
303                         radix_tree_preload_end();
304         }
305         if (error)
306                 mem_cgroup_uncharge_cache_page(page);
307         return error;
308 }
309
310 /*
311  * Like delete_from_page_cache, but substitutes swap for page.
312  */
313 static void shmem_delete_from_page_cache(struct page *page, void *radswap)
314 {
315         struct address_space *mapping = page->mapping;
316         int error;
317
318         spin_lock_irq(&mapping->tree_lock);
319         error = shmem_radix_tree_replace(mapping, page->index, page, radswap);
320         page->mapping = NULL;
321         mapping->nrpages--;
322         __dec_zone_page_state(page, NR_FILE_PAGES);
323         __dec_zone_page_state(page, NR_SHMEM);
324         spin_unlock_irq(&mapping->tree_lock);
325         page_cache_release(page);
326         BUG_ON(error);
327 }
328
329 /*
330  * Like find_get_pages, but collecting swap entries as well as pages.
331  */
332 static unsigned shmem_find_get_pages_and_swap(struct address_space *mapping,
333                                         pgoff_t start, unsigned int nr_pages,
334                                         struct page **pages, pgoff_t *indices)
335 {
336         unsigned int i;
337         unsigned int ret;
338         unsigned int nr_found;
339
340         rcu_read_lock();
341 restart:
342         nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
343                                 (void ***)pages, indices, start, nr_pages);
344         ret = 0;
345         for (i = 0; i < nr_found; i++) {
346                 struct page *page;
347 repeat:
348                 page = radix_tree_deref_slot((void **)pages[i]);
349                 if (unlikely(!page))
350                         continue;
351                 if (radix_tree_exception(page)) {
352                         if (radix_tree_deref_retry(page))
353                                 goto restart;
354                         /*
355                          * Otherwise, we must be storing a swap entry
356                          * here as an exceptional entry: so return it
357                          * without attempting to raise page count.
358                          */
359                         goto export;
360                 }
361                 if (!page_cache_get_speculative(page))
362                         goto repeat;
363
364                 /* Has the page moved? */
365                 if (unlikely(page != *((void **)pages[i]))) {
366                         page_cache_release(page);
367                         goto repeat;
368                 }
369 export:
370                 indices[ret] = indices[i];
371                 pages[ret] = page;
372                 ret++;
373         }
374         if (unlikely(!ret && nr_found))
375                 goto restart;
376         rcu_read_unlock();
377         return ret;
378 }
379
380 /*
381  * Remove swap entry from radix tree, free the swap and its page cache.
382  */
383 static int shmem_free_swap(struct address_space *mapping,
384                            pgoff_t index, void *radswap)
385 {
386         int error;
387
388         spin_lock_irq(&mapping->tree_lock);
389         error = shmem_radix_tree_replace(mapping, index, radswap, NULL);
390         spin_unlock_irq(&mapping->tree_lock);
391         if (!error)
392                 free_swap_and_cache(radix_to_swp_entry(radswap));
393         return error;
394 }
395
396 /*
397  * Pagevec may contain swap entries, so shuffle up pages before releasing.
398  */
399 static void shmem_deswap_pagevec(struct pagevec *pvec)
400 {
401         int i, j;
402
403         for (i = 0, j = 0; i < pagevec_count(pvec); i++) {
404                 struct page *page = pvec->pages[i];
405                 if (!radix_tree_exceptional_entry(page))
406                         pvec->pages[j++] = page;
407         }
408         pvec->nr = j;
409 }
410
411 /*
412  * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists.
413  */
414 void shmem_unlock_mapping(struct address_space *mapping)
415 {
416         struct pagevec pvec;
417         pgoff_t indices[PAGEVEC_SIZE];
418         pgoff_t index = 0;
419
420         pagevec_init(&pvec, 0);
421         /*
422          * Minor point, but we might as well stop if someone else SHM_LOCKs it.
423          */
424         while (!mapping_unevictable(mapping)) {
425                 /*
426                  * Avoid pagevec_lookup(): find_get_pages() returns 0 as if it
427                  * has finished, if it hits a row of PAGEVEC_SIZE swap entries.
428                  */
429                 pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
430                                         PAGEVEC_SIZE, pvec.pages, indices);
431                 if (!pvec.nr)
432                         break;
433                 index = indices[pvec.nr - 1] + 1;
434                 shmem_deswap_pagevec(&pvec);
435                 check_move_unevictable_pages(pvec.pages, pvec.nr);
436                 pagevec_release(&pvec);
437                 cond_resched();
438         }
439 }
440
441 /*
442  * Remove range of pages and swap entries from radix tree, and free them.
443  * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.
444  */
445 static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
446                                                                  bool unfalloc)
447 {
448         struct address_space *mapping = inode->i_mapping;
449         struct shmem_inode_info *info = SHMEM_I(inode);
450         pgoff_t start = (lstart + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
451         pgoff_t end = (lend + 1) >> PAGE_CACHE_SHIFT;
452         unsigned int partial_start = lstart & (PAGE_CACHE_SIZE - 1);
453         unsigned int partial_end = (lend + 1) & (PAGE_CACHE_SIZE - 1);
454         struct pagevec pvec;
455         pgoff_t indices[PAGEVEC_SIZE];
456         long nr_swaps_freed = 0;
457         pgoff_t index;
458         int i;
459
460         if (lend == -1)
461                 end = -1;       /* unsigned, so actually very big */
462
463         pagevec_init(&pvec, 0);
464         index = start;
465         while (index < end) {
466                 pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
467                                 min(end - index, (pgoff_t)PAGEVEC_SIZE),
468                                                         pvec.pages, indices);
469                 if (!pvec.nr)
470                         break;
471                 mem_cgroup_uncharge_start();
472                 for (i = 0; i < pagevec_count(&pvec); i++) {
473                         struct page *page = pvec.pages[i];
474
475                         index = indices[i];
476                         if (index >= end)
477                                 break;
478
479                         if (radix_tree_exceptional_entry(page)) {
480                                 if (unfalloc)
481                                         continue;
482                                 nr_swaps_freed += !shmem_free_swap(mapping,
483                                                                 index, page);
484                                 continue;
485                         }
486
487                         if (!trylock_page(page))
488                                 continue;
489                         if (!unfalloc || !PageUptodate(page)) {
490                                 if (page->mapping == mapping) {
491                                         VM_BUG_ON(PageWriteback(page));
492                                         truncate_inode_page(mapping, page);
493                                 }
494                         }
495                         unlock_page(page);
496                 }
497                 shmem_deswap_pagevec(&pvec);
498                 pagevec_release(&pvec);
499                 mem_cgroup_uncharge_end();
500                 cond_resched();
501                 index++;
502         }
503
504         if (partial_start) {
505                 struct page *page = NULL;
506                 shmem_getpage(inode, start - 1, &page, SGP_READ, NULL);
507                 if (page) {
508                         unsigned int top = PAGE_CACHE_SIZE;
509                         if (start > end) {
510                                 top = partial_end;
511                                 partial_end = 0;
512                         }
513                         zero_user_segment(page, partial_start, top);
514                         set_page_dirty(page);
515                         unlock_page(page);
516                         page_cache_release(page);
517                 }
518         }
519         if (partial_end) {
520                 struct page *page = NULL;
521                 shmem_getpage(inode, end, &page, SGP_READ, NULL);
522                 if (page) {
523                         zero_user_segment(page, 0, partial_end);
524                         set_page_dirty(page);
525                         unlock_page(page);
526                         page_cache_release(page);
527                 }
528         }
529         if (start >= end)
530                 return;
531
532         index = start;
533         for ( ; ; ) {
534                 cond_resched();
535                 pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
536                                 min(end - index, (pgoff_t)PAGEVEC_SIZE),
537                                                         pvec.pages, indices);
538                 if (!pvec.nr) {
539                         if (index == start || unfalloc)
540                                 break;
541                         index = start;
542                         continue;
543                 }
544                 if ((index == start || unfalloc) && indices[0] >= end) {
545                         shmem_deswap_pagevec(&pvec);
546                         pagevec_release(&pvec);
547                         break;
548                 }
549                 mem_cgroup_uncharge_start();
550                 for (i = 0; i < pagevec_count(&pvec); i++) {
551                         struct page *page = pvec.pages[i];
552
553                         index = indices[i];
554                         if (index >= end)
555                                 break;
556
557                         if (radix_tree_exceptional_entry(page)) {
558                                 if (unfalloc)
559                                         continue;
560                                 nr_swaps_freed += !shmem_free_swap(mapping,
561                                                                 index, page);
562                                 continue;
563                         }
564
565                         lock_page(page);
566                         if (!unfalloc || !PageUptodate(page)) {
567                                 if (page->mapping == mapping) {
568                                         VM_BUG_ON(PageWriteback(page));
569                                         truncate_inode_page(mapping, page);
570                                 }
571                         }
572                         unlock_page(page);
573                 }
574                 shmem_deswap_pagevec(&pvec);
575                 pagevec_release(&pvec);
576                 mem_cgroup_uncharge_end();
577                 index++;
578         }
579
580         spin_lock(&info->lock);
581         info->swapped -= nr_swaps_freed;
582         shmem_recalc_inode(inode);
583         spin_unlock(&info->lock);
584 }
585
586 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
587 {
588         shmem_undo_range(inode, lstart, lend, false);
589         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
590 }
591 EXPORT_SYMBOL_GPL(shmem_truncate_range);
592
593 static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
594 {
595         struct inode *inode = dentry->d_inode;
596         int error;
597
598         error = inode_change_ok(inode, attr);
599         if (error)
600                 return error;
601
602         if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
603                 loff_t oldsize = inode->i_size;
604                 loff_t newsize = attr->ia_size;
605
606                 if (newsize != oldsize) {
607                         i_size_write(inode, newsize);
608                         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
609                 }
610                 if (newsize < oldsize) {
611                         loff_t holebegin = round_up(newsize, PAGE_SIZE);
612                         unmap_mapping_range(inode->i_mapping, holebegin, 0, 1);
613                         shmem_truncate_range(inode, newsize, (loff_t)-1);
614                         /* unmap again to remove racily COWed private pages */
615                         unmap_mapping_range(inode->i_mapping, holebegin, 0, 1);
616                 }
617         }
618
619         setattr_copy(inode, attr);
620 #ifdef CONFIG_TMPFS_POSIX_ACL
621         if (attr->ia_valid & ATTR_MODE)
622                 error = generic_acl_chmod(inode);
623 #endif
624         return error;
625 }
626
627 static void shmem_evict_inode(struct inode *inode)
628 {
629         struct shmem_inode_info *info = SHMEM_I(inode);
630         struct shmem_xattr *xattr, *nxattr;
631
632         if (inode->i_mapping->a_ops == &shmem_aops) {
633                 shmem_unacct_size(info->flags, inode->i_size);
634                 inode->i_size = 0;
635                 shmem_truncate_range(inode, 0, (loff_t)-1);
636                 if (!list_empty(&info->swaplist)) {
637                         mutex_lock(&shmem_swaplist_mutex);
638                         list_del_init(&info->swaplist);
639                         mutex_unlock(&shmem_swaplist_mutex);
640                 }
641         } else
642                 kfree(info->symlink);
643
644         list_for_each_entry_safe(xattr, nxattr, &info->xattr_list, list) {
645                 kfree(xattr->name);
646                 kfree(xattr);
647         }
648         BUG_ON(inode->i_blocks);
649         shmem_free_inode(inode->i_sb);
650         clear_inode(inode);
651 }
652
653 /*
654  * If swap found in inode, free it and move page from swapcache to filecache.
655  */
656 static int shmem_unuse_inode(struct shmem_inode_info *info,
657                              swp_entry_t swap, struct page **pagep)
658 {
659         struct address_space *mapping = info->vfs_inode.i_mapping;
660         void *radswap;
661         pgoff_t index;
662         gfp_t gfp;
663         int error = 0;
664
665         radswap = swp_to_radix_entry(swap);
666         index = radix_tree_locate_item(&mapping->page_tree, radswap);
667         if (index == -1)
668                 return 0;
669
670         /*
671          * Move _head_ to start search for next from here.
672          * But be careful: shmem_evict_inode checks list_empty without taking
673          * mutex, and there's an instant in list_move_tail when info->swaplist
674          * would appear empty, if it were the only one on shmem_swaplist.
675          */
676         if (shmem_swaplist.next != &info->swaplist)
677                 list_move_tail(&shmem_swaplist, &info->swaplist);
678
679         gfp = mapping_gfp_mask(mapping);
680         if (shmem_should_replace_page(*pagep, gfp)) {
681                 mutex_unlock(&shmem_swaplist_mutex);
682                 error = shmem_replace_page(pagep, gfp, info, index);
683                 mutex_lock(&shmem_swaplist_mutex);
684                 /*
685                  * We needed to drop mutex to make that restrictive page
686                  * allocation, but the inode might have been freed while we
687                  * dropped it: although a racing shmem_evict_inode() cannot
688                  * complete without emptying the radix_tree, our page lock
689                  * on this swapcache page is not enough to prevent that -
690                  * free_swap_and_cache() of our swap entry will only
691                  * trylock_page(), removing swap from radix_tree whatever.
692                  *
693                  * We must not proceed to shmem_add_to_page_cache() if the
694                  * inode has been freed, but of course we cannot rely on
695                  * inode or mapping or info to check that.  However, we can
696                  * safely check if our swap entry is still in use (and here
697                  * it can't have got reused for another page): if it's still
698                  * in use, then the inode cannot have been freed yet, and we
699                  * can safely proceed (if it's no longer in use, that tells
700                  * nothing about the inode, but we don't need to unuse swap).
701                  */
702                 if (!page_swapcount(*pagep))
703                         error = -ENOENT;
704         }
705
706         /*
707          * We rely on shmem_swaplist_mutex, not only to protect the swaplist,
708          * but also to hold up shmem_evict_inode(): so inode cannot be freed
709          * beneath us (pagelock doesn't help until the page is in pagecache).
710          */
711         if (!error)
712                 error = shmem_add_to_page_cache(*pagep, mapping, index,
713                                                 GFP_NOWAIT, radswap);
714         if (error != -ENOMEM) {
715                 /*
716                  * Truncation and eviction use free_swap_and_cache(), which
717                  * only does trylock page: if we raced, best clean up here.
718                  */
719                 delete_from_swap_cache(*pagep);
720                 set_page_dirty(*pagep);
721                 if (!error) {
722                         spin_lock(&info->lock);
723                         info->swapped--;
724                         spin_unlock(&info->lock);
725                         swap_free(swap);
726                 }
727                 error = 1;      /* not an error, but entry was found */
728         }
729         return error;
730 }
731
732 /*
733  * Search through swapped inodes to find and replace swap by page.
734  */
735 int shmem_unuse(swp_entry_t swap, struct page *page)
736 {
737         struct list_head *this, *next;
738         struct shmem_inode_info *info;
739         int found = 0;
740         int error = 0;
741
742         /*
743          * There's a faint possibility that swap page was replaced before
744          * caller locked it: caller will come back later with the right page.
745          */
746         if (unlikely(!PageSwapCache(page) || page_private(page) != swap.val))
747                 goto out;
748
749         /*
750          * Charge page using GFP_KERNEL while we can wait, before taking
751          * the shmem_swaplist_mutex which might hold up shmem_writepage().
752          * Charged back to the user (not to caller) when swap account is used.
753          */
754         error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL);
755         if (error)
756                 goto out;
757         /* No radix_tree_preload: swap entry keeps a place for page in tree */
758
759         mutex_lock(&shmem_swaplist_mutex);
760         list_for_each_safe(this, next, &shmem_swaplist) {
761                 info = list_entry(this, struct shmem_inode_info, swaplist);
762                 if (info->swapped)
763                         found = shmem_unuse_inode(info, swap, &page);
764                 else
765                         list_del_init(&info->swaplist);
766                 cond_resched();
767                 if (found)
768                         break;
769         }
770         mutex_unlock(&shmem_swaplist_mutex);
771
772         if (found < 0)
773                 error = found;
774 out:
775         unlock_page(page);
776         page_cache_release(page);
777         return error;
778 }
779
780 /*
781  * Move the page from the page cache to the swap cache.
782  */
783 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
784 {
785         struct shmem_inode_info *info;
786         struct address_space *mapping;
787         struct inode *inode;
788         swp_entry_t swap;
789         pgoff_t index;
790
791         BUG_ON(!PageLocked(page));
792         mapping = page->mapping;
793         index = page->index;
794         inode = mapping->host;
795         info = SHMEM_I(inode);
796         if (info->flags & VM_LOCKED)
797                 goto redirty;
798         if (!total_swap_pages)
799                 goto redirty;
800
801         /*
802          * shmem_backing_dev_info's capabilities prevent regular writeback or
803          * sync from ever calling shmem_writepage; but a stacking filesystem
804          * might use ->writepage of its underlying filesystem, in which case
805          * tmpfs should write out to swap only in response to memory pressure,
806          * and not for the writeback threads or sync.
807          */
808         if (!wbc->for_reclaim) {
809                 WARN_ON_ONCE(1);        /* Still happens? Tell us about it! */
810                 goto redirty;
811         }
812
813         /*
814          * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC
815          * value into swapfile.c, the only way we can correctly account for a
816          * fallocated page arriving here is now to initialize it and write it.
817          *
818          * That's okay for a page already fallocated earlier, but if we have
819          * not yet completed the fallocation, then (a) we want to keep track
820          * of this page in case we have to undo it, and (b) it may not be a
821          * good idea to continue anyway, once we're pushing into swap.  So
822          * reactivate the page, and let shmem_fallocate() quit when too many.
823          */
824         if (!PageUptodate(page)) {
825                 if (inode->i_private) {
826                         struct shmem_falloc *shmem_falloc;
827                         spin_lock(&inode->i_lock);
828                         shmem_falloc = inode->i_private;
829                         if (shmem_falloc &&
830                             index >= shmem_falloc->start &&
831                             index < shmem_falloc->next)
832                                 shmem_falloc->nr_unswapped++;
833                         else
834                                 shmem_falloc = NULL;
835                         spin_unlock(&inode->i_lock);
836                         if (shmem_falloc)
837                                 goto redirty;
838                 }
839                 clear_highpage(page);
840                 flush_dcache_page(page);
841                 SetPageUptodate(page);
842         }
843
844         swap = get_swap_page();
845         if (!swap.val)
846                 goto redirty;
847
848         /*
849          * Add inode to shmem_unuse()'s list of swapped-out inodes,
850          * if it's not already there.  Do it now before the page is
851          * moved to swap cache, when its pagelock no longer protects
852          * the inode from eviction.  But don't unlock the mutex until
853          * we've incremented swapped, because shmem_unuse_inode() will
854          * prune a !swapped inode from the swaplist under this mutex.
855          */
856         mutex_lock(&shmem_swaplist_mutex);
857         if (list_empty(&info->swaplist))
858                 list_add_tail(&info->swaplist, &shmem_swaplist);
859
860         if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
861                 swap_shmem_alloc(swap);
862                 shmem_delete_from_page_cache(page, swp_to_radix_entry(swap));
863
864                 spin_lock(&info->lock);
865                 info->swapped++;
866                 shmem_recalc_inode(inode);
867                 spin_unlock(&info->lock);
868
869                 mutex_unlock(&shmem_swaplist_mutex);
870                 BUG_ON(page_mapped(page));
871                 swap_writepage(page, wbc);
872                 return 0;
873         }
874
875         mutex_unlock(&shmem_swaplist_mutex);
876         swapcache_free(swap, NULL);
877 redirty:
878         set_page_dirty(page);
879         if (wbc->for_reclaim)
880                 return AOP_WRITEPAGE_ACTIVATE;  /* Return with page locked */
881         unlock_page(page);
882         return 0;
883 }
884
885 #ifdef CONFIG_NUMA
886 #ifdef CONFIG_TMPFS
887 static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
888 {
889         char buffer[64];
890
891         if (!mpol || mpol->mode == MPOL_DEFAULT)
892                 return;         /* show nothing */
893
894         mpol_to_str(buffer, sizeof(buffer), mpol, 1);
895
896         seq_printf(seq, ",mpol=%s", buffer);
897 }
898
899 static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
900 {
901         struct mempolicy *mpol = NULL;
902         if (sbinfo->mpol) {
903                 spin_lock(&sbinfo->stat_lock);  /* prevent replace/use races */
904                 mpol = sbinfo->mpol;
905                 mpol_get(mpol);
906                 spin_unlock(&sbinfo->stat_lock);
907         }
908         return mpol;
909 }
910 #endif /* CONFIG_TMPFS */
911
912 static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
913                         struct shmem_inode_info *info, pgoff_t index)
914 {
915         struct mempolicy mpol, *spol;
916         struct vm_area_struct pvma;
917
918         spol = mpol_cond_copy(&mpol,
919                         mpol_shared_policy_lookup(&info->policy, index));
920
921         /* Create a pseudo vma that just contains the policy */
922         pvma.vm_start = 0;
923         pvma.vm_pgoff = index;
924         pvma.vm_ops = NULL;
925         pvma.vm_policy = spol;
926         return swapin_readahead(swap, gfp, &pvma, 0);
927 }
928
929 static struct page *shmem_alloc_page(gfp_t gfp,
930                         struct shmem_inode_info *info, pgoff_t index)
931 {
932         struct vm_area_struct pvma;
933
934         /* Create a pseudo vma that just contains the policy */
935         pvma.vm_start = 0;
936         pvma.vm_pgoff = index;
937         pvma.vm_ops = NULL;
938         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
939
940         /*
941          * alloc_page_vma() will drop the shared policy reference
942          */
943         return alloc_page_vma(gfp, &pvma, 0);
944 }
945 #else /* !CONFIG_NUMA */
946 #ifdef CONFIG_TMPFS
947 static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
948 {
949 }
950 #endif /* CONFIG_TMPFS */
951
952 static inline struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
953                         struct shmem_inode_info *info, pgoff_t index)
954 {
955         return swapin_readahead(swap, gfp, NULL, 0);
956 }
957
958 static inline struct page *shmem_alloc_page(gfp_t gfp,
959                         struct shmem_inode_info *info, pgoff_t index)
960 {
961         return alloc_page(gfp);
962 }
963 #endif /* CONFIG_NUMA */
964
965 #if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS)
966 static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
967 {
968         return NULL;
969 }
970 #endif
971
972 /*
973  * When a page is moved from swapcache to shmem filecache (either by the
974  * usual swapin of shmem_getpage_gfp(), or by the less common swapoff of
975  * shmem_unuse_inode()), it may have been read in earlier from swap, in
976  * ignorance of the mapping it belongs to.  If that mapping has special
977  * constraints (like the gma500 GEM driver, which requires RAM below 4GB),
978  * we may need to copy to a suitable page before moving to filecache.
979  *
980  * In a future release, this may well be extended to respect cpuset and
981  * NUMA mempolicy, and applied also to anonymous pages in do_swap_page();
982  * but for now it is a simple matter of zone.
983  */
984 static bool shmem_should_replace_page(struct page *page, gfp_t gfp)
985 {
986         return page_zonenum(page) > gfp_zone(gfp);
987 }
988
989 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
990                                 struct shmem_inode_info *info, pgoff_t index)
991 {
992         struct page *oldpage, *newpage;
993         struct address_space *swap_mapping;
994         pgoff_t swap_index;
995         int error;
996
997         oldpage = *pagep;
998         swap_index = page_private(oldpage);
999         swap_mapping = page_mapping(oldpage);
1000
1001         /*
1002          * We have arrived here because our zones are constrained, so don't
1003          * limit chance of success by further cpuset and node constraints.
1004          */
1005         gfp &= ~GFP_CONSTRAINT_MASK;
1006         newpage = shmem_alloc_page(gfp, info, index);
1007         if (!newpage)
1008                 return -ENOMEM;
1009
1010         page_cache_get(newpage);
1011         copy_highpage(newpage, oldpage);
1012         flush_dcache_page(newpage);
1013
1014         __set_page_locked(newpage);
1015         SetPageUptodate(newpage);
1016         SetPageSwapBacked(newpage);
1017         set_page_private(newpage, swap_index);
1018         SetPageSwapCache(newpage);
1019
1020         /*
1021          * Our caller will very soon move newpage out of swapcache, but it's
1022          * a nice clean interface for us to replace oldpage by newpage there.
1023          */
1024         spin_lock_irq(&swap_mapping->tree_lock);
1025         error = shmem_radix_tree_replace(swap_mapping, swap_index, oldpage,
1026                                                                    newpage);
1027         if (!error) {
1028                 __inc_zone_page_state(newpage, NR_FILE_PAGES);
1029                 __dec_zone_page_state(oldpage, NR_FILE_PAGES);
1030         }
1031         spin_unlock_irq(&swap_mapping->tree_lock);
1032
1033         if (unlikely(error)) {
1034                 /*
1035                  * Is this possible?  I think not, now that our callers check
1036                  * both PageSwapCache and page_private after getting page lock;
1037                  * but be defensive.  Reverse old to newpage for clear and free.
1038                  */
1039                 oldpage = newpage;
1040         } else {
1041                 mem_cgroup_replace_page_cache(oldpage, newpage);
1042                 lru_cache_add_anon(newpage);
1043                 *pagep = newpage;
1044         }
1045
1046         ClearPageSwapCache(oldpage);
1047         set_page_private(oldpage, 0);
1048
1049         unlock_page(oldpage);
1050         page_cache_release(oldpage);
1051         page_cache_release(oldpage);
1052         return error;
1053 }
1054
1055 /*
1056  * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
1057  *
1058  * If we allocate a new one we do not mark it dirty. That's up to the
1059  * vm. If we swap it in we mark it dirty since we also free the swap
1060  * entry since a page cannot live in both the swap and page cache
1061  */
1062 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
1063         struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type)
1064 {
1065         struct address_space *mapping = inode->i_mapping;
1066         struct shmem_inode_info *info;
1067         struct shmem_sb_info *sbinfo;
1068         struct page *page;
1069         swp_entry_t swap;
1070         int error;
1071         int once = 0;
1072         int alloced = 0;
1073
1074         if (index > (MAX_LFS_FILESIZE >> PAGE_CACHE_SHIFT))
1075                 return -EFBIG;
1076 repeat:
1077         swap.val = 0;
1078         page = find_lock_page(mapping, index);
1079         if (radix_tree_exceptional_entry(page)) {
1080                 swap = radix_to_swp_entry(page);
1081                 page = NULL;
1082         }
1083
1084         if (sgp != SGP_WRITE && sgp != SGP_FALLOC &&
1085             ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
1086                 error = -EINVAL;
1087                 goto failed;
1088         }
1089
1090         /* fallocated page? */
1091         if (page && !PageUptodate(page)) {
1092                 if (sgp != SGP_READ)
1093                         goto clear;
1094                 unlock_page(page);
1095                 page_cache_release(page);
1096                 page = NULL;
1097         }
1098         if (page || (sgp == SGP_READ && !swap.val)) {
1099                 *pagep = page;
1100                 return 0;
1101         }
1102
1103         /*
1104          * Fast cache lookup did not find it:
1105          * bring it back from swap or allocate.
1106          */
1107         info = SHMEM_I(inode);
1108         sbinfo = SHMEM_SB(inode->i_sb);
1109
1110         if (swap.val) {
1111                 /* Look it up and read it in.. */
1112                 page = lookup_swap_cache(swap);
1113                 if (!page) {
1114                         /* here we actually do the io */
1115                         if (fault_type)
1116                                 *fault_type |= VM_FAULT_MAJOR;
1117                         page = shmem_swapin(swap, gfp, info, index);
1118                         if (!page) {
1119                                 error = -ENOMEM;
1120                                 goto failed;
1121                         }
1122                 }
1123
1124                 /* We have to do this with page locked to prevent races */
1125                 lock_page(page);
1126                 if (!PageSwapCache(page) || page_private(page) != swap.val ||
1127                     page->mapping) {
1128                         error = -EEXIST;        /* try again */
1129                         goto failed;
1130                 }
1131                 if (!PageUptodate(page)) {
1132                         error = -EIO;
1133                         goto failed;
1134                 }
1135                 wait_on_page_writeback(page);
1136
1137                 if (shmem_should_replace_page(page, gfp)) {
1138                         error = shmem_replace_page(&page, gfp, info, index);
1139                         if (error)
1140                                 goto failed;
1141                 }
1142
1143                 error = mem_cgroup_cache_charge(page, current->mm,
1144                                                 gfp & GFP_RECLAIM_MASK);
1145                 if (!error)
1146                         error = shmem_add_to_page_cache(page, mapping, index,
1147                                                 gfp, swp_to_radix_entry(swap));
1148                 if (error)
1149                         goto failed;
1150
1151                 spin_lock(&info->lock);
1152                 info->swapped--;
1153                 shmem_recalc_inode(inode);
1154                 spin_unlock(&info->lock);
1155
1156                 delete_from_swap_cache(page);
1157                 set_page_dirty(page);
1158                 swap_free(swap);
1159
1160         } else {
1161                 if (shmem_acct_block(info->flags)) {
1162                         error = -ENOSPC;
1163                         goto failed;
1164                 }
1165                 if (sbinfo->max_blocks) {
1166                         if (percpu_counter_compare(&sbinfo->used_blocks,
1167                                                 sbinfo->max_blocks) >= 0) {
1168                                 error = -ENOSPC;
1169                                 goto unacct;
1170                         }
1171                         percpu_counter_inc(&sbinfo->used_blocks);
1172                 }
1173
1174                 page = shmem_alloc_page(gfp, info, index);
1175                 if (!page) {
1176                         error = -ENOMEM;
1177                         goto decused;
1178                 }
1179
1180                 SetPageSwapBacked(page);
1181                 __set_page_locked(page);
1182                 error = mem_cgroup_cache_charge(page, current->mm,
1183                                                 gfp & GFP_RECLAIM_MASK);
1184                 if (!error)
1185                         error = shmem_add_to_page_cache(page, mapping, index,
1186                                                 gfp, NULL);
1187                 if (error)
1188                         goto decused;
1189                 lru_cache_add_anon(page);
1190
1191                 spin_lock(&info->lock);
1192                 info->alloced++;
1193                 inode->i_blocks += BLOCKS_PER_PAGE;
1194                 shmem_recalc_inode(inode);
1195                 spin_unlock(&info->lock);
1196                 alloced = true;
1197
1198                 /*
1199                  * Let SGP_FALLOC use the SGP_WRITE optimization on a new page.
1200                  */
1201                 if (sgp == SGP_FALLOC)
1202                         sgp = SGP_WRITE;
1203 clear:
1204                 /*
1205                  * Let SGP_WRITE caller clear ends if write does not fill page;
1206                  * but SGP_FALLOC on a page fallocated earlier must initialize
1207                  * it now, lest undo on failure cancel our earlier guarantee.
1208                  */
1209                 if (sgp != SGP_WRITE) {
1210                         clear_highpage(page);
1211                         flush_dcache_page(page);
1212                         SetPageUptodate(page);
1213                 }
1214                 if (sgp == SGP_DIRTY)
1215                         set_page_dirty(page);
1216         }
1217
1218         /* Perhaps the file has been truncated since we checked */
1219         if (sgp != SGP_WRITE && sgp != SGP_FALLOC &&
1220             ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
1221                 error = -EINVAL;
1222                 if (alloced)
1223                         goto trunc;
1224                 else
1225                         goto failed;
1226         }
1227         *pagep = page;
1228         return 0;
1229
1230         /*
1231          * Error recovery.
1232          */
1233 trunc:
1234         info = SHMEM_I(inode);
1235         ClearPageDirty(page);
1236         delete_from_page_cache(page);
1237         spin_lock(&info->lock);
1238         info->alloced--;
1239         inode->i_blocks -= BLOCKS_PER_PAGE;
1240         spin_unlock(&info->lock);
1241 decused:
1242         sbinfo = SHMEM_SB(inode->i_sb);
1243         if (sbinfo->max_blocks)
1244                 percpu_counter_add(&sbinfo->used_blocks, -1);
1245 unacct:
1246         shmem_unacct_blocks(info->flags, 1);
1247 failed:
1248         if (swap.val && error != -EINVAL) {
1249                 struct page *test = find_get_page(mapping, index);
1250                 if (test && !radix_tree_exceptional_entry(test))
1251                         page_cache_release(test);
1252                 /* Have another try if the entry has changed */
1253                 if (test != swp_to_radix_entry(swap))
1254                         error = -EEXIST;
1255         }
1256         if (page) {
1257                 unlock_page(page);
1258                 page_cache_release(page);
1259         }
1260         if (error == -ENOSPC && !once++) {
1261                 info = SHMEM_I(inode);
1262                 spin_lock(&info->lock);
1263                 shmem_recalc_inode(inode);
1264                 spin_unlock(&info->lock);
1265                 goto repeat;
1266         }
1267         if (error == -EEXIST)
1268                 goto repeat;
1269         return error;
1270 }
1271
1272 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1273 {
1274         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1275         int error;
1276         int ret = VM_FAULT_LOCKED;
1277
1278         error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
1279         if (error)
1280                 return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1281
1282         if (ret & VM_FAULT_MAJOR) {
1283                 count_vm_event(PGMAJFAULT);
1284                 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1285         }
1286         return ret;
1287 }
1288
1289 #ifdef CONFIG_NUMA
1290 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol)
1291 {
1292         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1293         return mpol_set_shared_policy(&SHMEM_I(inode)->policy, vma, mpol);
1294 }
1295
1296 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
1297                                           unsigned long addr)
1298 {
1299         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1300         pgoff_t index;
1301
1302         index = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1303         return mpol_shared_policy_lookup(&SHMEM_I(inode)->policy, index);
1304 }
1305 #endif
1306
1307 int shmem_lock(struct file *file, int lock, struct user_struct *user)
1308 {
1309         struct inode *inode = file->f_path.dentry->d_inode;
1310         struct shmem_inode_info *info = SHMEM_I(inode);
1311         int retval = -ENOMEM;
1312
1313         spin_lock(&info->lock);
1314         if (lock && !(info->flags & VM_LOCKED)) {
1315                 if (!user_shm_lock(inode->i_size, user))
1316                         goto out_nomem;
1317                 info->flags |= VM_LOCKED;
1318                 mapping_set_unevictable(file->f_mapping);
1319         }
1320         if (!lock && (info->flags & VM_LOCKED) && user) {
1321                 user_shm_unlock(inode->i_size, user);
1322                 info->flags &= ~VM_LOCKED;
1323                 mapping_clear_unevictable(file->f_mapping);
1324         }
1325         retval = 0;
1326
1327 out_nomem:
1328         spin_unlock(&info->lock);
1329         return retval;
1330 }
1331
1332 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1333 {
1334         file_accessed(file);
1335         vma->vm_ops = &shmem_vm_ops;
1336         vma->vm_flags |= VM_CAN_NONLINEAR;
1337         return 0;
1338 }
1339
1340 static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
1341                                      umode_t mode, dev_t dev, unsigned long flags)
1342 {
1343         struct inode *inode;
1344         struct shmem_inode_info *info;
1345         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1346
1347         if (shmem_reserve_inode(sb))
1348                 return NULL;
1349
1350         inode = new_inode(sb);
1351         if (inode) {
1352                 inode->i_ino = get_next_ino();
1353                 inode_init_owner(inode, dir, mode);
1354                 inode->i_blocks = 0;
1355                 inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1356                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1357                 inode->i_generation = get_seconds();
1358                 info = SHMEM_I(inode);
1359                 memset(info, 0, (char *)inode - (char *)info);
1360                 spin_lock_init(&info->lock);
1361                 info->flags = flags & VM_NORESERVE;
1362                 INIT_LIST_HEAD(&info->swaplist);
1363                 INIT_LIST_HEAD(&info->xattr_list);
1364                 cache_no_acl(inode);
1365
1366                 switch (mode & S_IFMT) {
1367                 default:
1368                         inode->i_op = &shmem_special_inode_operations;
1369                         init_special_inode(inode, mode, dev);
1370                         break;
1371                 case S_IFREG:
1372                         inode->i_mapping->a_ops = &shmem_aops;
1373                         inode->i_op = &shmem_inode_operations;
1374                         inode->i_fop = &shmem_file_operations;
1375                         mpol_shared_policy_init(&info->policy,
1376                                                  shmem_get_sbmpol(sbinfo));
1377                         break;
1378                 case S_IFDIR:
1379                         inc_nlink(inode);
1380                         /* Some things misbehave if size == 0 on a directory */
1381                         inode->i_size = 2 * BOGO_DIRENT_SIZE;
1382                         inode->i_op = &shmem_dir_inode_operations;
1383                         inode->i_fop = &simple_dir_operations;
1384                         break;
1385                 case S_IFLNK:
1386                         /*
1387                          * Must not load anything in the rbtree,
1388                          * mpol_free_shared_policy will not be called.
1389                          */
1390                         mpol_shared_policy_init(&info->policy, NULL);
1391                         break;
1392                 }
1393         } else
1394                 shmem_free_inode(sb);
1395         return inode;
1396 }
1397
1398 #ifdef CONFIG_TMPFS
1399 static const struct inode_operations shmem_symlink_inode_operations;
1400 static const struct inode_operations shmem_short_symlink_operations;
1401
1402 #ifdef CONFIG_TMPFS_XATTR
1403 static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
1404 #else
1405 #define shmem_initxattrs NULL
1406 #endif
1407
1408 static int
1409 shmem_write_begin(struct file *file, struct address_space *mapping,
1410                         loff_t pos, unsigned len, unsigned flags,
1411                         struct page **pagep, void **fsdata)
1412 {
1413         struct inode *inode = mapping->host;
1414         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1415         return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
1416 }
1417
1418 static int
1419 shmem_write_end(struct file *file, struct address_space *mapping,
1420                         loff_t pos, unsigned len, unsigned copied,
1421                         struct page *page, void *fsdata)
1422 {
1423         struct inode *inode = mapping->host;
1424
1425         if (pos + copied > inode->i_size)
1426                 i_size_write(inode, pos + copied);
1427
1428         if (!PageUptodate(page)) {
1429                 if (copied < PAGE_CACHE_SIZE) {
1430                         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
1431                         zero_user_segments(page, 0, from,
1432                                         from + copied, PAGE_CACHE_SIZE);
1433                 }
1434                 SetPageUptodate(page);
1435         }
1436         set_page_dirty(page);
1437         unlock_page(page);
1438         page_cache_release(page);
1439
1440         return copied;
1441 }
1442
1443 static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1444 {
1445         struct inode *inode = filp->f_path.dentry->d_inode;
1446         struct address_space *mapping = inode->i_mapping;
1447         pgoff_t index;
1448         unsigned long offset;
1449         enum sgp_type sgp = SGP_READ;
1450
1451         /*
1452          * Might this read be for a stacking filesystem?  Then when reading
1453          * holes of a sparse file, we actually need to allocate those pages,
1454          * and even mark them dirty, so it cannot exceed the max_blocks limit.
1455          */
1456         if (segment_eq(get_fs(), KERNEL_DS))
1457                 sgp = SGP_DIRTY;
1458
1459         index = *ppos >> PAGE_CACHE_SHIFT;
1460         offset = *ppos & ~PAGE_CACHE_MASK;
1461
1462         for (;;) {
1463                 struct page *page = NULL;
1464                 pgoff_t end_index;
1465                 unsigned long nr, ret;
1466                 loff_t i_size = i_size_read(inode);
1467
1468                 end_index = i_size >> PAGE_CACHE_SHIFT;
1469                 if (index > end_index)
1470                         break;
1471                 if (index == end_index) {
1472                         nr = i_size & ~PAGE_CACHE_MASK;
1473                         if (nr <= offset)
1474                                 break;
1475                 }
1476
1477                 desc->error = shmem_getpage(inode, index, &page, sgp, NULL);
1478                 if (desc->error) {
1479                         if (desc->error == -EINVAL)
1480                                 desc->error = 0;
1481                         break;
1482                 }
1483                 if (page)
1484                         unlock_page(page);
1485
1486                 /*
1487                  * We must evaluate after, since reads (unlike writes)
1488                  * are called without i_mutex protection against truncate
1489                  */
1490                 nr = PAGE_CACHE_SIZE;
1491                 i_size = i_size_read(inode);
1492                 end_index = i_size >> PAGE_CACHE_SHIFT;
1493                 if (index == end_index) {
1494                         nr = i_size & ~PAGE_CACHE_MASK;
1495                         if (nr <= offset) {
1496                                 if (page)
1497                                         page_cache_release(page);
1498                                 break;
1499                         }
1500                 }
1501                 nr -= offset;
1502
1503                 if (page) {
1504                         /*
1505                          * If users can be writing to this page using arbitrary
1506                          * virtual addresses, take care about potential aliasing
1507                          * before reading the page on the kernel side.
1508                          */
1509                         if (mapping_writably_mapped(mapping))
1510                                 flush_dcache_page(page);
1511                         /*
1512                          * Mark the page accessed if we read the beginning.
1513                          */
1514                         if (!offset)
1515                                 mark_page_accessed(page);
1516                 } else {
1517                         page = ZERO_PAGE(0);
1518                         page_cache_get(page);
1519                 }
1520
1521                 /*
1522                  * Ok, we have the page, and it's up-to-date, so
1523                  * now we can copy it to user space...
1524                  *
1525                  * The actor routine returns how many bytes were actually used..
1526                  * NOTE! This may not be the same as how much of a user buffer
1527                  * we filled up (we may be padding etc), so we can only update
1528                  * "pos" here (the actor routine has to update the user buffer
1529                  * pointers and the remaining count).
1530                  */
1531                 ret = actor(desc, page, offset, nr);
1532                 offset += ret;
1533                 index += offset >> PAGE_CACHE_SHIFT;
1534                 offset &= ~PAGE_CACHE_MASK;
1535
1536                 page_cache_release(page);
1537                 if (ret != nr || !desc->count)
1538                         break;
1539
1540                 cond_resched();
1541         }
1542
1543         *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1544         file_accessed(filp);
1545 }
1546
1547 static ssize_t shmem_file_aio_read(struct kiocb *iocb,
1548                 const struct iovec *iov, unsigned long nr_segs, loff_t pos)
1549 {
1550         struct file *filp = iocb->ki_filp;
1551         ssize_t retval;
1552         unsigned long seg;
1553         size_t count;
1554         loff_t *ppos = &iocb->ki_pos;
1555
1556         retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1557         if (retval)
1558                 return retval;
1559
1560         for (seg = 0; seg < nr_segs; seg++) {
1561                 read_descriptor_t desc;
1562
1563                 desc.written = 0;
1564                 desc.arg.buf = iov[seg].iov_base;
1565                 desc.count = iov[seg].iov_len;
1566                 if (desc.count == 0)
1567                         continue;
1568                 desc.error = 0;
1569                 do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1570                 retval += desc.written;
1571                 if (desc.error) {
1572                         retval = retval ?: desc.error;
1573                         break;
1574                 }
1575                 if (desc.count > 0)
1576                         break;
1577         }
1578         return retval;
1579 }
1580
1581 static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
1582                                 struct pipe_inode_info *pipe, size_t len,
1583                                 unsigned int flags)
1584 {
1585         struct address_space *mapping = in->f_mapping;
1586         struct inode *inode = mapping->host;
1587         unsigned int loff, nr_pages, req_pages;
1588         struct page *pages[PIPE_DEF_BUFFERS];
1589         struct partial_page partial[PIPE_DEF_BUFFERS];
1590         struct page *page;
1591         pgoff_t index, end_index;
1592         loff_t isize, left;
1593         int error, page_nr;
1594         struct splice_pipe_desc spd = {
1595                 .pages = pages,
1596                 .partial = partial,
1597                 .flags = flags,
1598                 .ops = &page_cache_pipe_buf_ops,
1599                 .spd_release = spd_release_page,
1600         };
1601
1602         isize = i_size_read(inode);
1603         if (unlikely(*ppos >= isize))
1604                 return 0;
1605
1606         left = isize - *ppos;
1607         if (unlikely(left < len))
1608                 len = left;
1609
1610         if (splice_grow_spd(pipe, &spd))
1611                 return -ENOMEM;
1612
1613         index = *ppos >> PAGE_CACHE_SHIFT;
1614         loff = *ppos & ~PAGE_CACHE_MASK;
1615         req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1616         nr_pages = min(req_pages, pipe->buffers);
1617
1618         spd.nr_pages = find_get_pages_contig(mapping, index,
1619                                                 nr_pages, spd.pages);
1620         index += spd.nr_pages;
1621         error = 0;
1622
1623         while (spd.nr_pages < nr_pages) {
1624                 error = shmem_getpage(inode, index, &page, SGP_CACHE, NULL);
1625                 if (error)
1626                         break;
1627                 unlock_page(page);
1628                 spd.pages[spd.nr_pages++] = page;
1629                 index++;
1630         }
1631
1632         index = *ppos >> PAGE_CACHE_SHIFT;
1633         nr_pages = spd.nr_pages;
1634         spd.nr_pages = 0;
1635
1636         for (page_nr = 0; page_nr < nr_pages; page_nr++) {
1637                 unsigned int this_len;
1638
1639                 if (!len)
1640                         break;
1641
1642                 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
1643                 page = spd.pages[page_nr];
1644
1645                 if (!PageUptodate(page) || page->mapping != mapping) {
1646                         error = shmem_getpage(inode, index, &page,
1647                                                         SGP_CACHE, NULL);
1648                         if (error)
1649                                 break;
1650                         unlock_page(page);
1651                         page_cache_release(spd.pages[page_nr]);
1652                         spd.pages[page_nr] = page;
1653                 }
1654
1655                 isize = i_size_read(inode);
1656                 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1657                 if (unlikely(!isize || index > end_index))
1658                         break;
1659
1660                 if (end_index == index) {
1661                         unsigned int plen;
1662
1663                         plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1664                         if (plen <= loff)
1665                                 break;
1666
1667                         this_len = min(this_len, plen - loff);
1668                         len = this_len;
1669                 }
1670
1671                 spd.partial[page_nr].offset = loff;
1672                 spd.partial[page_nr].len = this_len;
1673                 len -= this_len;
1674                 loff = 0;
1675                 spd.nr_pages++;
1676                 index++;
1677         }
1678
1679         while (page_nr < nr_pages)
1680                 page_cache_release(spd.pages[page_nr++]);
1681
1682         if (spd.nr_pages)
1683                 error = splice_to_pipe(pipe, &spd);
1684
1685         splice_shrink_spd(pipe, &spd);
1686
1687         if (error > 0) {
1688                 *ppos += error;
1689                 file_accessed(in);
1690         }
1691         return error;
1692 }
1693
1694 /*
1695  * llseek SEEK_DATA or SEEK_HOLE through the radix_tree.
1696  */
1697 static pgoff_t shmem_seek_hole_data(struct address_space *mapping,
1698                                     pgoff_t index, pgoff_t end, int origin)
1699 {
1700         struct page *page;
1701         struct pagevec pvec;
1702         pgoff_t indices[PAGEVEC_SIZE];
1703         bool done = false;
1704         int i;
1705
1706         pagevec_init(&pvec, 0);
1707         pvec.nr = 1;            /* start small: we may be there already */
1708         while (!done) {
1709                 pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
1710                                         pvec.nr, pvec.pages, indices);
1711                 if (!pvec.nr) {
1712                         if (origin == SEEK_DATA)
1713                                 index = end;
1714                         break;
1715                 }
1716                 for (i = 0; i < pvec.nr; i++, index++) {
1717                         if (index < indices[i]) {
1718                                 if (origin == SEEK_HOLE) {
1719                                         done = true;
1720                                         break;
1721                                 }
1722                                 index = indices[i];
1723                         }
1724                         page = pvec.pages[i];
1725                         if (page && !radix_tree_exceptional_entry(page)) {
1726                                 if (!PageUptodate(page))
1727                                         page = NULL;
1728                         }
1729                         if (index >= end ||
1730                             (page && origin == SEEK_DATA) ||
1731                             (!page && origin == SEEK_HOLE)) {
1732                                 done = true;
1733                                 break;
1734                         }
1735                 }
1736                 shmem_deswap_pagevec(&pvec);
1737                 pagevec_release(&pvec);
1738                 pvec.nr = PAGEVEC_SIZE;
1739                 cond_resched();
1740         }
1741         return index;
1742 }
1743
1744 static loff_t shmem_file_llseek(struct file *file, loff_t offset, int origin)
1745 {
1746         struct address_space *mapping;
1747         struct inode *inode;
1748         pgoff_t start, end;
1749         loff_t new_offset;
1750
1751         if (origin != SEEK_DATA && origin != SEEK_HOLE)
1752                 return generic_file_llseek_size(file, offset, origin,
1753                                                         MAX_LFS_FILESIZE);
1754         mapping = file->f_mapping;
1755         inode = mapping->host;
1756         mutex_lock(&inode->i_mutex);
1757         /* We're holding i_mutex so we can access i_size directly */
1758
1759         if (offset < 0)
1760                 offset = -EINVAL;
1761         else if (offset >= inode->i_size)
1762                 offset = -ENXIO;
1763         else {
1764                 start = offset >> PAGE_CACHE_SHIFT;
1765                 end = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1766                 new_offset = shmem_seek_hole_data(mapping, start, end, origin);
1767                 new_offset <<= PAGE_CACHE_SHIFT;
1768                 if (new_offset > offset) {
1769                         if (new_offset < inode->i_size)
1770                                 offset = new_offset;
1771                         else if (origin == SEEK_DATA)
1772                                 offset = -ENXIO;
1773                         else
1774                                 offset = inode->i_size;
1775                 }
1776         }
1777
1778         if (offset >= 0 && offset != file->f_pos) {
1779                 file->f_pos = offset;
1780                 file->f_version = 0;
1781         }
1782         mutex_unlock(&inode->i_mutex);
1783         return offset;
1784 }
1785
1786 static long shmem_fallocate(struct file *file, int mode, loff_t offset,
1787                                                          loff_t len)
1788 {
1789         struct inode *inode = file->f_path.dentry->d_inode;
1790         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1791         struct shmem_falloc shmem_falloc;
1792         pgoff_t start, index, end;
1793         int error;
1794
1795         mutex_lock(&inode->i_mutex);
1796
1797         if (mode & FALLOC_FL_PUNCH_HOLE) {
1798                 struct address_space *mapping = file->f_mapping;
1799                 loff_t unmap_start = round_up(offset, PAGE_SIZE);
1800                 loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1;
1801
1802                 if ((u64)unmap_end > (u64)unmap_start)
1803                         unmap_mapping_range(mapping, unmap_start,
1804                                             1 + unmap_end - unmap_start, 0);
1805                 shmem_truncate_range(inode, offset, offset + len - 1);
1806                 /* No need to unmap again: hole-punching leaves COWed pages */
1807                 error = 0;
1808                 goto out;
1809         }
1810
1811         /* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */
1812         error = inode_newsize_ok(inode, offset + len);
1813         if (error)
1814                 goto out;
1815
1816         start = offset >> PAGE_CACHE_SHIFT;
1817         end = (offset + len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1818         /* Try to avoid a swapstorm if len is impossible to satisfy */
1819         if (sbinfo->max_blocks && end - start > sbinfo->max_blocks) {
1820                 error = -ENOSPC;
1821                 goto out;
1822         }
1823
1824         shmem_falloc.start = start;
1825         shmem_falloc.next  = start;
1826         shmem_falloc.nr_falloced = 0;
1827         shmem_falloc.nr_unswapped = 0;
1828         spin_lock(&inode->i_lock);
1829         inode->i_private = &shmem_falloc;
1830         spin_unlock(&inode->i_lock);
1831
1832         for (index = start; index < end; index++) {
1833                 struct page *page;
1834
1835                 /*
1836                  * Good, the fallocate(2) manpage permits EINTR: we may have
1837                  * been interrupted because we are using up too much memory.
1838                  */
1839                 if (signal_pending(current))
1840                         error = -EINTR;
1841                 else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
1842                         error = -ENOMEM;
1843                 else
1844                         error = shmem_getpage(inode, index, &page, SGP_FALLOC,
1845                                                                         NULL);
1846                 if (error) {
1847                         /* Remove the !PageUptodate pages we added */
1848                         shmem_undo_range(inode,
1849                                 (loff_t)start << PAGE_CACHE_SHIFT,
1850                                 (loff_t)index << PAGE_CACHE_SHIFT, true);
1851                         goto undone;
1852                 }
1853
1854                 /*
1855                  * Inform shmem_writepage() how far we have reached.
1856                  * No need for lock or barrier: we have the page lock.
1857                  */
1858                 shmem_falloc.next++;
1859                 if (!PageUptodate(page))
1860                         shmem_falloc.nr_falloced++;
1861
1862                 /*
1863                  * If !PageUptodate, leave it that way so that freeable pages
1864                  * can be recognized if we need to rollback on error later.
1865                  * But set_page_dirty so that memory pressure will swap rather
1866                  * than free the pages we are allocating (and SGP_CACHE pages
1867                  * might still be clean: we now need to mark those dirty too).
1868                  */
1869                 set_page_dirty(page);
1870                 unlock_page(page);
1871                 page_cache_release(page);
1872                 cond_resched();
1873         }
1874
1875         if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
1876                 i_size_write(inode, offset + len);
1877         inode->i_ctime = CURRENT_TIME;
1878 undone:
1879         spin_lock(&inode->i_lock);
1880         inode->i_private = NULL;
1881         spin_unlock(&inode->i_lock);
1882 out:
1883         mutex_unlock(&inode->i_mutex);
1884         return error;
1885 }
1886
1887 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1888 {
1889         struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1890
1891         buf->f_type = TMPFS_MAGIC;
1892         buf->f_bsize = PAGE_CACHE_SIZE;
1893         buf->f_namelen = NAME_MAX;
1894         if (sbinfo->max_blocks) {
1895                 buf->f_blocks = sbinfo->max_blocks;
1896                 buf->f_bavail =
1897                 buf->f_bfree  = sbinfo->max_blocks -
1898                                 percpu_counter_sum(&sbinfo->used_blocks);
1899         }
1900         if (sbinfo->max_inodes) {
1901                 buf->f_files = sbinfo->max_inodes;
1902                 buf->f_ffree = sbinfo->free_inodes;
1903         }
1904         /* else leave those fields 0 like simple_statfs */
1905         return 0;
1906 }
1907
1908 /*
1909  * File creation. Allocate an inode, and we're done..
1910  */
1911 static int
1912 shmem_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
1913 {
1914         struct inode *inode;
1915         int error = -ENOSPC;
1916
1917         inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
1918         if (inode) {
1919                 error = security_inode_init_security(inode, dir,
1920                                                      &dentry->d_name,
1921                                                      shmem_initxattrs, NULL);
1922                 if (error) {
1923                         if (error != -EOPNOTSUPP) {
1924                                 iput(inode);
1925                                 return error;
1926                         }
1927                 }
1928 #ifdef CONFIG_TMPFS_POSIX_ACL
1929                 error = generic_acl_init(inode, dir);
1930                 if (error) {
1931                         iput(inode);
1932                         return error;
1933                 }
1934 #else
1935                 error = 0;
1936 #endif
1937                 dir->i_size += BOGO_DIRENT_SIZE;
1938                 dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1939                 d_instantiate(dentry, inode);
1940                 dget(dentry); /* Extra count - pin the dentry in core */
1941         }
1942         return error;
1943 }
1944
1945 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
1946 {
1947         int error;
1948
1949         if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1950                 return error;
1951         inc_nlink(dir);
1952         return 0;
1953 }
1954
1955 static int shmem_create(struct inode *dir, struct dentry *dentry, umode_t mode,
1956                 struct nameidata *nd)
1957 {
1958         return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1959 }
1960
1961 /*
1962  * Link a file..
1963  */
1964 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1965 {
1966         struct inode *inode = old_dentry->d_inode;
1967         int ret;
1968
1969         /*
1970          * No ordinary (disk based) filesystem counts links as inodes;
1971          * but each new link needs a new dentry, pinning lowmem, and
1972          * tmpfs dentries cannot be pruned until they are unlinked.
1973          */
1974         ret = shmem_reserve_inode(inode->i_sb);
1975         if (ret)
1976                 goto out;
1977
1978         dir->i_size += BOGO_DIRENT_SIZE;
1979         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1980         inc_nlink(inode);
1981         ihold(inode);   /* New dentry reference */
1982         dget(dentry);           /* Extra pinning count for the created dentry */
1983         d_instantiate(dentry, inode);
1984 out:
1985         return ret;
1986 }
1987
1988 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
1989 {
1990         struct inode *inode = dentry->d_inode;
1991
1992         if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
1993                 shmem_free_inode(inode->i_sb);
1994
1995         dir->i_size -= BOGO_DIRENT_SIZE;
1996         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1997         drop_nlink(inode);
1998         dput(dentry);   /* Undo the count from "create" - this does all the work */
1999         return 0;
2000 }
2001
2002 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
2003 {
2004         if (!simple_empty(dentry))
2005                 return -ENOTEMPTY;
2006
2007         drop_nlink(dentry->d_inode);
2008         drop_nlink(dir);
2009         return shmem_unlink(dir, dentry);
2010 }
2011
2012 /*
2013  * The VFS layer already does all the dentry stuff for rename,
2014  * we just have to decrement the usage count for the target if
2015  * it exists so that the VFS layer correctly free's it when it
2016  * gets overwritten.
2017  */
2018 static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
2019 {
2020         struct inode *inode = old_dentry->d_inode;
2021         int they_are_dirs = S_ISDIR(inode->i_mode);
2022
2023         if (!simple_empty(new_dentry))
2024                 return -ENOTEMPTY;
2025
2026         if (new_dentry->d_inode) {
2027                 (void) shmem_unlink(new_dir, new_dentry);
2028                 if (they_are_dirs)
2029                         drop_nlink(old_dir);
2030         } else if (they_are_dirs) {
2031                 drop_nlink(old_dir);
2032                 inc_nlink(new_dir);
2033         }
2034
2035         old_dir->i_size -= BOGO_DIRENT_SIZE;
2036         new_dir->i_size += BOGO_DIRENT_SIZE;
2037         old_dir->i_ctime = old_dir->i_mtime =
2038         new_dir->i_ctime = new_dir->i_mtime =
2039         inode->i_ctime = CURRENT_TIME;
2040         return 0;
2041 }
2042
2043 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
2044 {
2045         int error;
2046         int len;
2047         struct inode *inode;
2048         struct page *page;
2049         char *kaddr;
2050         struct shmem_inode_info *info;
2051
2052         len = strlen(symname) + 1;
2053         if (len > PAGE_CACHE_SIZE)
2054                 return -ENAMETOOLONG;
2055
2056         inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE);
2057         if (!inode)
2058                 return -ENOSPC;
2059
2060         error = security_inode_init_security(inode, dir, &dentry->d_name,
2061                                              shmem_initxattrs, NULL);
2062         if (error) {
2063                 if (error != -EOPNOTSUPP) {
2064                         iput(inode);
2065                         return error;
2066                 }
2067                 error = 0;
2068         }
2069
2070         info = SHMEM_I(inode);
2071         inode->i_size = len-1;
2072         if (len <= SHORT_SYMLINK_LEN) {
2073                 info->symlink = kmemdup(symname, len, GFP_KERNEL);
2074                 if (!info->symlink) {
2075                         iput(inode);
2076                         return -ENOMEM;
2077                 }
2078                 inode->i_op = &shmem_short_symlink_operations;
2079         } else {
2080                 error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
2081                 if (error) {
2082                         iput(inode);
2083                         return error;
2084                 }
2085                 inode->i_mapping->a_ops = &shmem_aops;
2086                 inode->i_op = &shmem_symlink_inode_operations;
2087                 kaddr = kmap_atomic(page);
2088                 memcpy(kaddr, symname, len);
2089                 kunmap_atomic(kaddr);
2090                 SetPageUptodate(page);
2091                 set_page_dirty(page);
2092                 unlock_page(page);
2093                 page_cache_release(page);
2094         }
2095         dir->i_size += BOGO_DIRENT_SIZE;
2096         dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2097         d_instantiate(dentry, inode);
2098         dget(dentry);
2099         return 0;
2100 }
2101
2102 static void *shmem_follow_short_symlink(struct dentry *dentry, struct nameidata *nd)
2103 {
2104         nd_set_link(nd, SHMEM_I(dentry->d_inode)->symlink);
2105         return NULL;
2106 }
2107
2108 static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
2109 {
2110         struct page *page = NULL;
2111         int error = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
2112         nd_set_link(nd, error ? ERR_PTR(error) : kmap(page));
2113         if (page)
2114                 unlock_page(page);
2115         return page;
2116 }
2117
2118 static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
2119 {
2120         if (!IS_ERR(nd_get_link(nd))) {
2121                 struct page *page = cookie;
2122                 kunmap(page);
2123                 mark_page_accessed(page);
2124                 page_cache_release(page);
2125         }
2126 }
2127
2128 #ifdef CONFIG_TMPFS_XATTR
2129 /*
2130  * Superblocks without xattr inode operations may get some security.* xattr
2131  * support from the LSM "for free". As soon as we have any other xattrs
2132  * like ACLs, we also need to implement the security.* handlers at
2133  * filesystem level, though.
2134  */
2135
2136 /*
2137  * Allocate new xattr and copy in the value; but leave the name to callers.
2138  */
2139 static struct shmem_xattr *shmem_xattr_alloc(const void *value, size_t size)
2140 {
2141         struct shmem_xattr *new_xattr;
2142         size_t len;
2143
2144         /* wrap around? */
2145         len = sizeof(*new_xattr) + size;
2146         if (len <= sizeof(*new_xattr))
2147                 return NULL;
2148
2149         new_xattr = kmalloc(len, GFP_KERNEL);
2150         if (!new_xattr)
2151                 return NULL;
2152
2153         new_xattr->size = size;
2154         memcpy(new_xattr->value, value, size);
2155         return new_xattr;
2156 }
2157
2158 /*
2159  * Callback for security_inode_init_security() for acquiring xattrs.
2160  */
2161 static int shmem_initxattrs(struct inode *inode,
2162                             const struct xattr *xattr_array,
2163                             void *fs_info)
2164 {
2165         struct shmem_inode_info *info = SHMEM_I(inode);
2166         const struct xattr *xattr;
2167         struct shmem_xattr *new_xattr;
2168         size_t len;
2169
2170         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
2171                 new_xattr = shmem_xattr_alloc(xattr->value, xattr->value_len);
2172                 if (!new_xattr)
2173                         return -ENOMEM;
2174
2175                 len = strlen(xattr->name) + 1;
2176                 new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
2177                                           GFP_KERNEL);
2178                 if (!new_xattr->name) {
2179                         kfree(new_xattr);
2180                         return -ENOMEM;
2181                 }
2182
2183                 memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
2184                        XATTR_SECURITY_PREFIX_LEN);
2185                 memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
2186                        xattr->name, len);
2187
2188                 spin_lock(&info->lock);
2189                 list_add(&new_xattr->list, &info->xattr_list);
2190                 spin_unlock(&info->lock);
2191         }
2192
2193         return 0;
2194 }
2195
2196 static int shmem_xattr_get(struct dentry *dentry, const char *name,
2197                            void *buffer, size_t size)
2198 {
2199         struct shmem_inode_info *info;
2200         struct shmem_xattr *xattr;
2201         int ret = -ENODATA;
2202
2203         info = SHMEM_I(dentry->d_inode);
2204
2205         spin_lock(&info->lock);
2206         list_for_each_entry(xattr, &info->xattr_list, list) {
2207                 if (strcmp(name, xattr->name))
2208                         continue;
2209
2210                 ret = xattr->size;
2211                 if (buffer) {
2212                         if (size < xattr->size)
2213                                 ret = -ERANGE;
2214                         else
2215                                 memcpy(buffer, xattr->value, xattr->size);
2216                 }
2217                 break;
2218         }
2219         spin_unlock(&info->lock);
2220         return ret;
2221 }
2222
2223 static int shmem_xattr_set(struct inode *inode, const char *name,
2224                            const void *value, size_t size, int flags)
2225 {
2226         struct shmem_inode_info *info = SHMEM_I(inode);
2227         struct shmem_xattr *xattr;
2228         struct shmem_xattr *new_xattr = NULL;
2229         int err = 0;
2230
2231         /* value == NULL means remove */
2232         if (value) {
2233                 new_xattr = shmem_xattr_alloc(value, size);
2234                 if (!new_xattr)
2235                         return -ENOMEM;
2236
2237                 new_xattr->name = kstrdup(name, GFP_KERNEL);
2238                 if (!new_xattr->name) {
2239                         kfree(new_xattr);
2240                         return -ENOMEM;
2241                 }
2242         }
2243
2244         spin_lock(&info->lock);
2245         list_for_each_entry(xattr, &info->xattr_list, list) {
2246                 if (!strcmp(name, xattr->name)) {
2247                         if (flags & XATTR_CREATE) {
2248                                 xattr = new_xattr;
2249                                 err = -EEXIST;
2250                         } else if (new_xattr) {
2251                                 list_replace(&xattr->list, &new_xattr->list);
2252                         } else {
2253                                 list_del(&xattr->list);
2254                         }
2255                         goto out;
2256                 }
2257         }
2258         if (flags & XATTR_REPLACE) {
2259                 xattr = new_xattr;
2260                 err = -ENODATA;
2261         } else {
2262                 list_add(&new_xattr->list, &info->xattr_list);
2263                 xattr = NULL;
2264         }
2265 out:
2266         spin_unlock(&info->lock);
2267         if (xattr)
2268                 kfree(xattr->name);
2269         kfree(xattr);
2270         return err;
2271 }
2272
2273 static const struct xattr_handler *shmem_xattr_handlers[] = {
2274 #ifdef CONFIG_TMPFS_POSIX_ACL
2275         &generic_acl_access_handler,
2276         &generic_acl_default_handler,
2277 #endif
2278         NULL
2279 };
2280
2281 static int shmem_xattr_validate(const char *name)
2282 {
2283         struct { const char *prefix; size_t len; } arr[] = {
2284                 { XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN },
2285                 { XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN }
2286         };
2287         int i;
2288
2289         for (i = 0; i < ARRAY_SIZE(arr); i++) {
2290                 size_t preflen = arr[i].len;
2291                 if (strncmp(name, arr[i].prefix, preflen) == 0) {
2292                         if (!name[preflen])
2293                                 return -EINVAL;
2294                         return 0;
2295                 }
2296         }
2297         return -EOPNOTSUPP;
2298 }
2299
2300 static ssize_t shmem_getxattr(struct dentry *dentry, const char *name,
2301                               void *buffer, size_t size)
2302 {
2303         int err;
2304
2305         /*
2306          * If this is a request for a synthetic attribute in the system.*
2307          * namespace use the generic infrastructure to resolve a handler
2308          * for it via sb->s_xattr.
2309          */
2310         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2311                 return generic_getxattr(dentry, name, buffer, size);
2312
2313         err = shmem_xattr_validate(name);
2314         if (err)
2315                 return err;
2316
2317         return shmem_xattr_get(dentry, name, buffer, size);
2318 }
2319
2320 static int shmem_setxattr(struct dentry *dentry, const char *name,
2321                           const void *value, size_t size, int flags)
2322 {
2323         int err;
2324
2325         /*
2326          * If this is a request for a synthetic attribute in the system.*
2327          * namespace use the generic infrastructure to resolve a handler
2328          * for it via sb->s_xattr.
2329          */
2330         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2331                 return generic_setxattr(dentry, name, value, size, flags);
2332
2333         err = shmem_xattr_validate(name);
2334         if (err)
2335                 return err;
2336
2337         if (size == 0)
2338                 value = "";  /* empty EA, do not remove */
2339
2340         return shmem_xattr_set(dentry->d_inode, name, value, size, flags);
2341
2342 }
2343
2344 static int shmem_removexattr(struct dentry *dentry, const char *name)
2345 {
2346         int err;
2347
2348         /*
2349          * If this is a request for a synthetic attribute in the system.*
2350          * namespace use the generic infrastructure to resolve a handler
2351          * for it via sb->s_xattr.
2352          */
2353         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2354                 return generic_removexattr(dentry, name);
2355
2356         err = shmem_xattr_validate(name);
2357         if (err)
2358                 return err;
2359
2360         return shmem_xattr_set(dentry->d_inode, name, NULL, 0, XATTR_REPLACE);
2361 }
2362
2363 static bool xattr_is_trusted(const char *name)
2364 {
2365         return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
2366 }
2367
2368 static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
2369 {
2370         bool trusted = capable(CAP_SYS_ADMIN);
2371         struct shmem_xattr *xattr;
2372         struct shmem_inode_info *info;
2373         size_t used = 0;
2374
2375         info = SHMEM_I(dentry->d_inode);
2376
2377         spin_lock(&info->lock);
2378         list_for_each_entry(xattr, &info->xattr_list, list) {
2379                 size_t len;
2380
2381                 /* skip "trusted." attributes for unprivileged callers */
2382                 if (!trusted && xattr_is_trusted(xattr->name))
2383                         continue;
2384
2385                 len = strlen(xattr->name) + 1;
2386                 used += len;
2387                 if (buffer) {
2388                         if (size < used) {
2389                                 used = -ERANGE;
2390                                 break;
2391                         }
2392                         memcpy(buffer, xattr->name, len);
2393                         buffer += len;
2394                 }
2395         }
2396         spin_unlock(&info->lock);
2397
2398         return used;
2399 }
2400 #endif /* CONFIG_TMPFS_XATTR */
2401
2402 static const struct inode_operations shmem_short_symlink_operations = {
2403         .readlink       = generic_readlink,
2404         .follow_link    = shmem_follow_short_symlink,
2405 #ifdef CONFIG_TMPFS_XATTR
2406         .setxattr       = shmem_setxattr,
2407         .getxattr       = shmem_getxattr,
2408         .listxattr      = shmem_listxattr,
2409         .removexattr    = shmem_removexattr,
2410 #endif
2411 };
2412
2413 static const struct inode_operations shmem_symlink_inode_operations = {
2414         .readlink       = generic_readlink,
2415         .follow_link    = shmem_follow_link,
2416         .put_link       = shmem_put_link,
2417 #ifdef CONFIG_TMPFS_XATTR
2418         .setxattr       = shmem_setxattr,
2419         .getxattr       = shmem_getxattr,
2420         .listxattr      = shmem_listxattr,
2421         .removexattr    = shmem_removexattr,
2422 #endif
2423 };
2424
2425 static struct dentry *shmem_get_parent(struct dentry *child)
2426 {
2427         return ERR_PTR(-ESTALE);
2428 }
2429
2430 static int shmem_match(struct inode *ino, void *vfh)
2431 {
2432         __u32 *fh = vfh;
2433         __u64 inum = fh[2];
2434         inum = (inum << 32) | fh[1];
2435         return ino->i_ino == inum && fh[0] == ino->i_generation;
2436 }
2437
2438 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
2439                 struct fid *fid, int fh_len, int fh_type)
2440 {
2441         struct inode *inode;
2442         struct dentry *dentry = NULL;
2443         u64 inum = fid->raw[2];
2444         inum = (inum << 32) | fid->raw[1];
2445
2446         if (fh_len < 3)
2447                 return NULL;
2448
2449         inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
2450                         shmem_match, fid->raw);
2451         if (inode) {
2452                 dentry = d_find_alias(inode);
2453                 iput(inode);
2454         }
2455
2456         return dentry;
2457 }
2458
2459 static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len,
2460                                 struct inode *parent)
2461 {
2462         if (*len < 3) {
2463                 *len = 3;
2464                 return 255;
2465         }
2466
2467         if (inode_unhashed(inode)) {
2468                 /* Unfortunately insert_inode_hash is not idempotent,
2469                  * so as we hash inodes here rather than at creation
2470                  * time, we need a lock to ensure we only try
2471                  * to do it once
2472                  */
2473                 static DEFINE_SPINLOCK(lock);
2474                 spin_lock(&lock);
2475                 if (inode_unhashed(inode))
2476                         __insert_inode_hash(inode,
2477                                             inode->i_ino + inode->i_generation);
2478                 spin_unlock(&lock);
2479         }
2480
2481         fh[0] = inode->i_generation;
2482         fh[1] = inode->i_ino;
2483         fh[2] = ((__u64)inode->i_ino) >> 32;
2484
2485         *len = 3;
2486         return 1;
2487 }
2488
2489 static const struct export_operations shmem_export_ops = {
2490         .get_parent     = shmem_get_parent,
2491         .encode_fh      = shmem_encode_fh,
2492         .fh_to_dentry   = shmem_fh_to_dentry,
2493 };
2494
2495 static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
2496                                bool remount)
2497 {
2498         char *this_char, *value, *rest;
2499         uid_t uid;
2500         gid_t gid;
2501
2502         while (options != NULL) {
2503                 this_char = options;
2504                 for (;;) {
2505                         /*
2506                          * NUL-terminate this option: unfortunately,
2507                          * mount options form a comma-separated list,
2508                          * but mpol's nodelist may also contain commas.
2509                          */
2510                         options = strchr(options, ',');
2511                         if (options == NULL)
2512                                 break;
2513                         options++;
2514                         if (!isdigit(*options)) {
2515                                 options[-1] = '\0';
2516                                 break;
2517                         }
2518                 }
2519                 if (!*this_char)
2520                         continue;
2521                 if ((value = strchr(this_char,'=')) != NULL) {
2522                         *value++ = 0;
2523                 } else {
2524                         printk(KERN_ERR
2525                             "tmpfs: No value for mount option '%s'\n",
2526                             this_char);
2527                         return 1;
2528                 }
2529
2530                 if (!strcmp(this_char,"size")) {
2531                         unsigned long long size;
2532                         size = memparse(value,&rest);
2533                         if (*rest == '%') {
2534                                 size <<= PAGE_SHIFT;
2535                                 size *= totalram_pages;
2536                                 do_div(size, 100);
2537                                 rest++;
2538                         }
2539                         if (*rest)
2540                                 goto bad_val;
2541                         sbinfo->max_blocks =
2542                                 DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
2543                 } else if (!strcmp(this_char,"nr_blocks")) {
2544                         sbinfo->max_blocks = memparse(value, &rest);
2545                         if (*rest)
2546                                 goto bad_val;
2547                 } else if (!strcmp(this_char,"nr_inodes")) {
2548                         sbinfo->max_inodes = memparse(value, &rest);
2549                         if (*rest)
2550                                 goto bad_val;
2551                 } else if (!strcmp(this_char,"mode")) {
2552                         if (remount)
2553                                 continue;
2554                         sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
2555                         if (*rest)
2556                                 goto bad_val;
2557                 } else if (!strcmp(this_char,"uid")) {
2558                         if (remount)
2559                                 continue;
2560                         uid = simple_strtoul(value, &rest, 0);
2561                         if (*rest)
2562                                 goto bad_val;
2563                         sbinfo->uid = make_kuid(current_user_ns(), uid);
2564                         if (!uid_valid(sbinfo->uid))
2565                                 goto bad_val;
2566                 } else if (!strcmp(this_char,"gid")) {
2567                         if (remount)
2568                                 continue;
2569                         gid = simple_strtoul(value, &rest, 0);
2570                         if (*rest)
2571                                 goto bad_val;
2572                         sbinfo->gid = make_kgid(current_user_ns(), gid);
2573                         if (!gid_valid(sbinfo->gid))
2574                                 goto bad_val;
2575                 } else if (!strcmp(this_char,"mpol")) {
2576                         if (mpol_parse_str(value, &sbinfo->mpol, 1))
2577                                 goto bad_val;
2578                 } else {
2579                         printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2580                                this_char);
2581                         return 1;
2582                 }
2583         }
2584         return 0;
2585
2586 bad_val:
2587         printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2588                value, this_char);
2589         return 1;
2590
2591 }
2592
2593 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2594 {
2595         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2596         struct shmem_sb_info config = *sbinfo;
2597         unsigned long inodes;
2598         int error = -EINVAL;
2599
2600         if (shmem_parse_options(data, &config, true))
2601                 return error;
2602
2603         spin_lock(&sbinfo->stat_lock);
2604         inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2605         if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0)
2606                 goto out;
2607         if (config.max_inodes < inodes)
2608                 goto out;
2609         /*
2610          * Those tests disallow limited->unlimited while any are in use;
2611          * but we must separately disallow unlimited->limited, because
2612          * in that case we have no record of how much is already in use.
2613          */
2614         if (config.max_blocks && !sbinfo->max_blocks)
2615                 goto out;
2616         if (config.max_inodes && !sbinfo->max_inodes)
2617                 goto out;
2618
2619         error = 0;
2620         sbinfo->max_blocks  = config.max_blocks;
2621         sbinfo->max_inodes  = config.max_inodes;
2622         sbinfo->free_inodes = config.max_inodes - inodes;
2623
2624         mpol_put(sbinfo->mpol);
2625         sbinfo->mpol        = config.mpol;      /* transfers initial ref */
2626 out:
2627         spin_unlock(&sbinfo->stat_lock);
2628         return error;
2629 }
2630
2631 static int shmem_show_options(struct seq_file *seq, struct dentry *root)
2632 {
2633         struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb);
2634
2635         if (sbinfo->max_blocks != shmem_default_max_blocks())
2636                 seq_printf(seq, ",size=%luk",
2637                         sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
2638         if (sbinfo->max_inodes != shmem_default_max_inodes())
2639                 seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
2640         if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
2641                 seq_printf(seq, ",mode=%03ho", sbinfo->mode);
2642         if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
2643                 seq_printf(seq, ",uid=%u",
2644                                 from_kuid_munged(&init_user_ns, sbinfo->uid));
2645         if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
2646                 seq_printf(seq, ",gid=%u",
2647                                 from_kgid_munged(&init_user_ns, sbinfo->gid));
2648         shmem_show_mpol(seq, sbinfo->mpol);
2649         return 0;
2650 }
2651 #endif /* CONFIG_TMPFS */
2652
2653 static void shmem_put_super(struct super_block *sb)
2654 {
2655         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2656
2657         percpu_counter_destroy(&sbinfo->used_blocks);
2658         kfree(sbinfo);
2659         sb->s_fs_info = NULL;
2660 }
2661
2662 int shmem_fill_super(struct super_block *sb, void *data, int silent)
2663 {
2664         struct inode *inode;
2665         struct shmem_sb_info *sbinfo;
2666         int err = -ENOMEM;
2667
2668         /* Round up to L1_CACHE_BYTES to resist false sharing */
2669         sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
2670                                 L1_CACHE_BYTES), GFP_KERNEL);
2671         if (!sbinfo)
2672                 return -ENOMEM;
2673
2674         sbinfo->mode = S_IRWXUGO | S_ISVTX;
2675         sbinfo->uid = current_fsuid();
2676         sbinfo->gid = current_fsgid();
2677         sb->s_fs_info = sbinfo;
2678
2679 #ifdef CONFIG_TMPFS
2680         /*
2681          * Per default we only allow half of the physical ram per
2682          * tmpfs instance, limiting inodes to one per page of lowmem;
2683          * but the internal instance is left unlimited.
2684          */
2685         if (!(sb->s_flags & MS_NOUSER)) {
2686                 sbinfo->max_blocks = shmem_default_max_blocks();
2687                 sbinfo->max_inodes = shmem_default_max_inodes();
2688                 if (shmem_parse_options(data, sbinfo, false)) {
2689                         err = -EINVAL;
2690                         goto failed;
2691                 }
2692         }
2693         sb->s_export_op = &shmem_export_ops;
2694         sb->s_flags |= MS_NOSEC;
2695 #else
2696         sb->s_flags |= MS_NOUSER;
2697 #endif
2698
2699         spin_lock_init(&sbinfo->stat_lock);
2700         if (percpu_counter_init(&sbinfo->used_blocks, 0))
2701                 goto failed;
2702         sbinfo->free_inodes = sbinfo->max_inodes;
2703
2704         sb->s_maxbytes = MAX_LFS_FILESIZE;
2705         sb->s_blocksize = PAGE_CACHE_SIZE;
2706         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2707         sb->s_magic = TMPFS_MAGIC;
2708         sb->s_op = &shmem_ops;
2709         sb->s_time_gran = 1;
2710 #ifdef CONFIG_TMPFS_XATTR
2711         sb->s_xattr = shmem_xattr_handlers;
2712 #endif
2713 #ifdef CONFIG_TMPFS_POSIX_ACL
2714         sb->s_flags |= MS_POSIXACL;
2715 #endif
2716
2717         inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
2718         if (!inode)
2719                 goto failed;
2720         inode->i_uid = sbinfo->uid;
2721         inode->i_gid = sbinfo->gid;
2722         sb->s_root = d_make_root(inode);
2723         if (!sb->s_root)
2724                 goto failed;
2725         return 0;
2726
2727 failed:
2728         shmem_put_super(sb);
2729         return err;
2730 }
2731
2732 static struct kmem_cache *shmem_inode_cachep;
2733
2734 static struct inode *shmem_alloc_inode(struct super_block *sb)
2735 {
2736         struct shmem_inode_info *info;
2737         info = kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2738         if (!info)
2739                 return NULL;
2740         return &info->vfs_inode;
2741 }
2742
2743 static void shmem_destroy_callback(struct rcu_head *head)
2744 {
2745         struct inode *inode = container_of(head, struct inode, i_rcu);
2746         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2747 }
2748
2749 static void shmem_destroy_inode(struct inode *inode)
2750 {
2751         if (S_ISREG(inode->i_mode))
2752                 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2753         call_rcu(&inode->i_rcu, shmem_destroy_callback);
2754 }
2755
2756 static void shmem_init_inode(void *foo)
2757 {
2758         struct shmem_inode_info *info = foo;
2759         inode_init_once(&info->vfs_inode);
2760 }
2761
2762 static int shmem_init_inodecache(void)
2763 {
2764         shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2765                                 sizeof(struct shmem_inode_info),
2766                                 0, SLAB_PANIC, shmem_init_inode);
2767         return 0;
2768 }
2769
2770 static void shmem_destroy_inodecache(void)
2771 {
2772         kmem_cache_destroy(shmem_inode_cachep);
2773 }
2774
2775 static const struct address_space_operations shmem_aops = {
2776         .writepage      = shmem_writepage,
2777         .set_page_dirty = __set_page_dirty_no_writeback,
2778 #ifdef CONFIG_TMPFS
2779         .write_begin    = shmem_write_begin,
2780         .write_end      = shmem_write_end,
2781 #endif
2782         .migratepage    = migrate_page,
2783         .error_remove_page = generic_error_remove_page,
2784 };
2785
2786 static const struct file_operations shmem_file_operations = {
2787         .mmap           = shmem_mmap,
2788 #ifdef CONFIG_TMPFS
2789         .llseek         = shmem_file_llseek,
2790         .read           = do_sync_read,
2791         .write          = do_sync_write,
2792         .aio_read       = shmem_file_aio_read,
2793         .aio_write      = generic_file_aio_write,
2794         .fsync          = noop_fsync,
2795         .splice_read    = shmem_file_splice_read,
2796         .splice_write   = generic_file_splice_write,
2797         .fallocate      = shmem_fallocate,
2798 #endif
2799 };
2800
2801 static const struct inode_operations shmem_inode_operations = {
2802         .setattr        = shmem_setattr,
2803 #ifdef CONFIG_TMPFS_XATTR
2804         .setxattr       = shmem_setxattr,
2805         .getxattr       = shmem_getxattr,
2806         .listxattr      = shmem_listxattr,
2807         .removexattr    = shmem_removexattr,
2808 #endif
2809 };
2810
2811 static const struct inode_operations shmem_dir_inode_operations = {
2812 #ifdef CONFIG_TMPFS
2813         .create         = shmem_create,
2814         .lookup         = simple_lookup,
2815         .link           = shmem_link,
2816         .unlink         = shmem_unlink,
2817         .symlink        = shmem_symlink,
2818         .mkdir          = shmem_mkdir,
2819         .rmdir          = shmem_rmdir,
2820         .mknod          = shmem_mknod,
2821         .rename         = shmem_rename,
2822 #endif
2823 #ifdef CONFIG_TMPFS_XATTR
2824         .setxattr       = shmem_setxattr,
2825         .getxattr       = shmem_getxattr,
2826         .listxattr      = shmem_listxattr,
2827         .removexattr    = shmem_removexattr,
2828 #endif
2829 #ifdef CONFIG_TMPFS_POSIX_ACL
2830         .setattr        = shmem_setattr,
2831 #endif
2832 };
2833
2834 static const struct inode_operations shmem_special_inode_operations = {
2835 #ifdef CONFIG_TMPFS_XATTR
2836         .setxattr       = shmem_setxattr,
2837         .getxattr       = shmem_getxattr,
2838         .listxattr      = shmem_listxattr,
2839         .removexattr    = shmem_removexattr,
2840 #endif
2841 #ifdef CONFIG_TMPFS_POSIX_ACL
2842         .setattr        = shmem_setattr,
2843 #endif
2844 };
2845
2846 static const struct super_operations shmem_ops = {
2847         .alloc_inode    = shmem_alloc_inode,
2848         .destroy_inode  = shmem_destroy_inode,
2849 #ifdef CONFIG_TMPFS
2850         .statfs         = shmem_statfs,
2851         .remount_fs     = shmem_remount_fs,
2852         .show_options   = shmem_show_options,
2853 #endif
2854         .evict_inode    = shmem_evict_inode,
2855         .drop_inode     = generic_delete_inode,
2856         .put_super      = shmem_put_super,
2857 };
2858
2859 static const struct vm_operations_struct shmem_vm_ops = {
2860         .fault          = shmem_fault,
2861 #ifdef CONFIG_NUMA
2862         .set_policy     = shmem_set_policy,
2863         .get_policy     = shmem_get_policy,
2864 #endif
2865 };
2866
2867 static struct dentry *shmem_mount(struct file_system_type *fs_type,
2868         int flags, const char *dev_name, void *data)
2869 {
2870         return mount_nodev(fs_type, flags, data, shmem_fill_super);
2871 }
2872
2873 static struct file_system_type shmem_fs_type = {
2874         .owner          = THIS_MODULE,
2875         .name           = "tmpfs",
2876         .mount          = shmem_mount,
2877         .kill_sb        = kill_litter_super,
2878 };
2879
2880 int __init shmem_init(void)
2881 {
2882         int error;
2883
2884         error = bdi_init(&shmem_backing_dev_info);
2885         if (error)
2886                 goto out4;
2887
2888         error = shmem_init_inodecache();
2889         if (error)
2890                 goto out3;
2891
2892         error = register_filesystem(&shmem_fs_type);
2893         if (error) {
2894                 printk(KERN_ERR "Could not register tmpfs\n");
2895                 goto out2;
2896         }
2897
2898         shm_mnt = vfs_kern_mount(&shmem_fs_type, MS_NOUSER,
2899                                  shmem_fs_type.name, NULL);
2900         if (IS_ERR(shm_mnt)) {
2901                 error = PTR_ERR(shm_mnt);
2902                 printk(KERN_ERR "Could not kern_mount tmpfs\n");
2903                 goto out1;
2904         }
2905         return 0;
2906
2907 out1:
2908         unregister_filesystem(&shmem_fs_type);
2909 out2:
2910         shmem_destroy_inodecache();
2911 out3:
2912         bdi_destroy(&shmem_backing_dev_info);
2913 out4:
2914         shm_mnt = ERR_PTR(error);
2915         return error;
2916 }
2917
2918 #else /* !CONFIG_SHMEM */
2919
2920 /*
2921  * tiny-shmem: simple shmemfs and tmpfs using ramfs code
2922  *
2923  * This is intended for small system where the benefits of the full
2924  * shmem code (swap-backed and resource-limited) are outweighed by
2925  * their complexity. On systems without swap this code should be
2926  * effectively equivalent, but much lighter weight.
2927  */
2928
2929 #include <linux/ramfs.h>
2930
2931 static struct file_system_type shmem_fs_type = {
2932         .name           = "tmpfs",
2933         .mount          = ramfs_mount,
2934         .kill_sb        = kill_litter_super,
2935 };
2936
2937 int __init shmem_init(void)
2938 {
2939         BUG_ON(register_filesystem(&shmem_fs_type) != 0);
2940
2941         shm_mnt = kern_mount(&shmem_fs_type);
2942         BUG_ON(IS_ERR(shm_mnt));
2943
2944         return 0;
2945 }
2946
2947 int shmem_unuse(swp_entry_t swap, struct page *page)
2948 {
2949         return 0;
2950 }
2951
2952 int shmem_lock(struct file *file, int lock, struct user_struct *user)
2953 {
2954         return 0;
2955 }
2956
2957 void shmem_unlock_mapping(struct address_space *mapping)
2958 {
2959 }
2960
2961 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
2962 {
2963         truncate_inode_pages_range(inode->i_mapping, lstart, lend);
2964 }
2965 EXPORT_SYMBOL_GPL(shmem_truncate_range);
2966
2967 #define shmem_vm_ops                            generic_file_vm_ops
2968 #define shmem_file_operations                   ramfs_file_operations
2969 #define shmem_get_inode(sb, dir, mode, dev, flags)      ramfs_get_inode(sb, dir, mode, dev)
2970 #define shmem_acct_size(flags, size)            0
2971 #define shmem_unacct_size(flags, size)          do {} while (0)
2972
2973 #endif /* CONFIG_SHMEM */
2974
2975 /* common code */
2976
2977 /**
2978  * shmem_file_setup - get an unlinked file living in tmpfs
2979  * @name: name for dentry (to be seen in /proc/<pid>/maps
2980  * @size: size to be set for the file
2981  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
2982  */
2983 struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
2984 {
2985         int error;
2986         struct file *file;
2987         struct inode *inode;
2988         struct path path;
2989         struct dentry *root;
2990         struct qstr this;
2991
2992         if (IS_ERR(shm_mnt))
2993                 return (void *)shm_mnt;
2994
2995         if (size < 0 || size > MAX_LFS_FILESIZE)
2996                 return ERR_PTR(-EINVAL);
2997
2998         if (shmem_acct_size(flags, size))
2999                 return ERR_PTR(-ENOMEM);
3000
3001         error = -ENOMEM;
3002         this.name = name;
3003         this.len = strlen(name);
3004         this.hash = 0; /* will go */
3005         root = shm_mnt->mnt_root;
3006         path.dentry = d_alloc(root, &this);
3007         if (!path.dentry)
3008                 goto put_memory;
3009         path.mnt = mntget(shm_mnt);
3010
3011         error = -ENOSPC;
3012         inode = shmem_get_inode(root->d_sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
3013         if (!inode)
3014                 goto put_dentry;
3015
3016         d_instantiate(path.dentry, inode);
3017         inode->i_size = size;
3018         clear_nlink(inode);     /* It is unlinked */
3019 #ifndef CONFIG_MMU
3020         error = ramfs_nommu_expand_for_mapping(inode, size);
3021         if (error)
3022                 goto put_dentry;
3023 #endif
3024
3025         error = -ENFILE;
3026         file = alloc_file(&path, FMODE_WRITE | FMODE_READ,
3027                   &shmem_file_operations);
3028         if (!file)
3029                 goto put_dentry;
3030
3031         return file;
3032
3033 put_dentry:
3034         path_put(&path);
3035 put_memory:
3036         shmem_unacct_size(flags, size);
3037         return ERR_PTR(error);
3038 }
3039 EXPORT_SYMBOL_GPL(shmem_file_setup);
3040
3041 /**
3042  * shmem_zero_setup - setup a shared anonymous mapping
3043  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
3044  */
3045 int shmem_zero_setup(struct vm_area_struct *vma)
3046 {
3047         struct file *file;
3048         loff_t size = vma->vm_end - vma->vm_start;
3049
3050         file = shmem_file_setup("dev/zero", size, vma->vm_flags);
3051         if (IS_ERR(file))
3052                 return PTR_ERR(file);
3053
3054         if (vma->vm_file)
3055                 fput(vma->vm_file);
3056         vma->vm_file = file;
3057         vma->vm_ops = &shmem_vm_ops;
3058         vma->vm_flags |= VM_CAN_NONLINEAR;
3059         return 0;
3060 }
3061
3062 /**
3063  * shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags.
3064  * @mapping:    the page's address_space
3065  * @index:      the page index
3066  * @gfp:        the page allocator flags to use if allocating
3067  *
3068  * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)",
3069  * with any new page allocations done using the specified allocation flags.
3070  * But read_cache_page_gfp() uses the ->readpage() method: which does not
3071  * suit tmpfs, since it may have pages in swapcache, and needs to find those
3072  * for itself; although drivers/gpu/drm i915 and ttm rely upon this support.
3073  *
3074  * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in
3075  * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily.
3076  */
3077 struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
3078                                          pgoff_t index, gfp_t gfp)
3079 {
3080 #ifdef CONFIG_SHMEM
3081         struct inode *inode = mapping->host;
3082         struct page *page;
3083         int error;
3084
3085         BUG_ON(mapping->a_ops != &shmem_aops);
3086         error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE, gfp, NULL);
3087         if (error)
3088                 page = ERR_PTR(error);
3089         else
3090                 unlock_page(page);
3091         return page;
3092 #else
3093         /*
3094          * The tiny !SHMEM case uses ramfs without swap
3095          */
3096         return read_cache_page_gfp(mapping, index, gfp);
3097 #endif
3098 }
3099 EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);