2 * Resizable virtual memory filesystem for Linux.
4 * Copyright (C) 2000 Linus Torvalds.
6 * 2000-2001 Christoph Rohland
9 * Copyright (C) 2002-2005 Hugh Dickins.
10 * Copyright (C) 2002-2005 VERITAS Software Corporation.
11 * Copyright (C) 2004 Andi Kleen, SuSE Labs
13 * Extended attribute support for tmpfs:
14 * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
15 * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
18 * Copyright (c) 2004, 2008 Matt Mackall <mpm@selenic.com>
20 * This file is released under the GPL.
24 #include <linux/init.h>
25 #include <linux/vfs.h>
26 #include <linux/mount.h>
27 #include <linux/pagemap.h>
28 #include <linux/file.h>
30 #include <linux/module.h>
31 #include <linux/swap.h>
33 static struct vfsmount *shm_mnt;
37 * This virtual memory filesystem is heavily based on the ramfs. It
38 * extends ramfs by the ability to use swap and honor resource limits
39 * which makes it a completely usable filesystem.
42 #include <linux/xattr.h>
43 #include <linux/exportfs.h>
44 #include <linux/posix_acl.h>
45 #include <linux/generic_acl.h>
46 #include <linux/mman.h>
47 #include <linux/string.h>
48 #include <linux/slab.h>
49 #include <linux/backing-dev.h>
50 #include <linux/shmem_fs.h>
51 #include <linux/writeback.h>
52 #include <linux/blkdev.h>
53 #include <linux/security.h>
54 #include <linux/swapops.h>
55 #include <linux/mempolicy.h>
56 #include <linux/namei.h>
57 #include <linux/ctype.h>
58 #include <linux/migrate.h>
59 #include <linux/highmem.h>
60 #include <linux/seq_file.h>
61 #include <linux/magic.h>
63 #include <asm/uaccess.h>
64 #include <asm/div64.h>
65 #include <asm/pgtable.h>
68 * The maximum size of a shmem/tmpfs file is limited by the maximum size of
69 * its triple-indirect swap vector - see illustration at shmem_swp_entry().
71 * With 4kB page size, maximum file size is just over 2TB on a 32-bit kernel,
72 * but one eighth of that on a 64-bit kernel. With 8kB page size, maximum
73 * file size is just over 4TB on a 64-bit kernel, but 16TB on a 32-bit kernel,
74 * MAX_LFS_FILESIZE being then more restrictive than swap vector layout.
76 * We use / and * instead of shifts in the definitions below, so that the swap
77 * vector can be tested with small even values (e.g. 20) for ENTRIES_PER_PAGE.
79 #define ENTRIES_PER_PAGE (PAGE_CACHE_SIZE/sizeof(unsigned long))
80 #define ENTRIES_PER_PAGEPAGE ((unsigned long long)ENTRIES_PER_PAGE*ENTRIES_PER_PAGE)
82 #define SHMSWP_MAX_INDEX (SHMEM_NR_DIRECT + (ENTRIES_PER_PAGEPAGE/2) * (ENTRIES_PER_PAGE+1))
83 #define SHMSWP_MAX_BYTES (SHMSWP_MAX_INDEX << PAGE_CACHE_SHIFT)
85 #define SHMEM_MAX_BYTES min_t(unsigned long long, SHMSWP_MAX_BYTES, MAX_LFS_FILESIZE)
86 #define SHMEM_MAX_INDEX ((unsigned long)((SHMEM_MAX_BYTES+1) >> PAGE_CACHE_SHIFT))
88 #define BLOCKS_PER_PAGE (PAGE_CACHE_SIZE/512)
89 #define VM_ACCT(size) (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
91 /* info->flags needs VM_flags to handle pagein/truncate races efficiently */
92 #define SHMEM_PAGEIN VM_READ
93 #define SHMEM_TRUNCATE VM_WRITE
95 /* Definition to limit shmem_truncate's steps between cond_rescheds */
96 #define LATENCY_LIMIT 64
98 /* Pretend that each entry is of this size in directory's i_size */
99 #define BOGO_DIRENT_SIZE 20
101 /* Flag allocation requirements to shmem_getpage and shmem_swp_alloc */
103 SGP_READ, /* don't exceed i_size, don't allocate page */
104 SGP_CACHE, /* don't exceed i_size, may allocate page */
105 SGP_DIRTY, /* like SGP_CACHE, but set new page dirty */
106 SGP_WRITE, /* may exceed i_size, may allocate page */
110 static unsigned long shmem_default_max_blocks(void)
112 return totalram_pages / 2;
115 static unsigned long shmem_default_max_inodes(void)
117 return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
121 static int shmem_getpage(struct inode *inode, unsigned long idx,
122 struct page **pagep, enum sgp_type sgp, int *type);
124 static inline struct page *shmem_dir_alloc(gfp_t gfp_mask)
127 * The above definition of ENTRIES_PER_PAGE, and the use of
128 * BLOCKS_PER_PAGE on indirect pages, assume PAGE_CACHE_SIZE:
129 * might be reconsidered if it ever diverges from PAGE_SIZE.
131 * Mobility flags are masked out as swap vectors cannot move
133 return alloc_pages((gfp_mask & ~GFP_MOVABLE_MASK) | __GFP_ZERO,
134 PAGE_CACHE_SHIFT-PAGE_SHIFT);
137 static inline void shmem_dir_free(struct page *page)
139 __free_pages(page, PAGE_CACHE_SHIFT-PAGE_SHIFT);
142 static struct page **shmem_dir_map(struct page *page)
144 return (struct page **)kmap_atomic(page, KM_USER0);
147 static inline void shmem_dir_unmap(struct page **dir)
149 kunmap_atomic(dir, KM_USER0);
152 static swp_entry_t *shmem_swp_map(struct page *page)
154 return (swp_entry_t *)kmap_atomic(page, KM_USER1);
157 static inline void shmem_swp_balance_unmap(void)
160 * When passing a pointer to an i_direct entry, to code which
161 * also handles indirect entries and so will shmem_swp_unmap,
162 * we must arrange for the preempt count to remain in balance.
163 * What kmap_atomic of a lowmem page does depends on config
164 * and architecture, so pretend to kmap_atomic some lowmem page.
166 (void) kmap_atomic(ZERO_PAGE(0), KM_USER1);
169 static inline void shmem_swp_unmap(swp_entry_t *entry)
171 kunmap_atomic(entry, KM_USER1);
174 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
176 return sb->s_fs_info;
180 * shmem_file_setup pre-accounts the whole fixed size of a VM object,
181 * for shared memory and for shared anonymous (/dev/zero) mappings
182 * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
183 * consistent with the pre-accounting of private mappings ...
185 static inline int shmem_acct_size(unsigned long flags, loff_t size)
187 return (flags & VM_NORESERVE) ?
188 0 : security_vm_enough_memory_kern(VM_ACCT(size));
191 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
193 if (!(flags & VM_NORESERVE))
194 vm_unacct_memory(VM_ACCT(size));
198 * ... whereas tmpfs objects are accounted incrementally as
199 * pages are allocated, in order to allow huge sparse files.
200 * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
201 * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
203 static inline int shmem_acct_block(unsigned long flags)
205 return (flags & VM_NORESERVE) ?
206 security_vm_enough_memory_kern(VM_ACCT(PAGE_CACHE_SIZE)) : 0;
209 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
211 if (flags & VM_NORESERVE)
212 vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
215 static const struct super_operations shmem_ops;
216 static const struct address_space_operations shmem_aops;
217 static const struct file_operations shmem_file_operations;
218 static const struct inode_operations shmem_inode_operations;
219 static const struct inode_operations shmem_dir_inode_operations;
220 static const struct inode_operations shmem_special_inode_operations;
221 static const struct vm_operations_struct shmem_vm_ops;
223 static struct backing_dev_info shmem_backing_dev_info __read_mostly = {
224 .ra_pages = 0, /* No readahead */
225 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
226 .unplug_io_fn = default_unplug_io_fn,
229 static LIST_HEAD(shmem_swaplist);
230 static DEFINE_MUTEX(shmem_swaplist_mutex);
232 static void shmem_free_blocks(struct inode *inode, long pages)
234 struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
235 if (sbinfo->max_blocks) {
236 spin_lock(&sbinfo->stat_lock);
237 sbinfo->free_blocks += pages;
238 inode->i_blocks -= pages*BLOCKS_PER_PAGE;
239 spin_unlock(&sbinfo->stat_lock);
243 static int shmem_reserve_inode(struct super_block *sb)
245 struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
246 if (sbinfo->max_inodes) {
247 spin_lock(&sbinfo->stat_lock);
248 if (!sbinfo->free_inodes) {
249 spin_unlock(&sbinfo->stat_lock);
252 sbinfo->free_inodes--;
253 spin_unlock(&sbinfo->stat_lock);
258 static void shmem_free_inode(struct super_block *sb)
260 struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
261 if (sbinfo->max_inodes) {
262 spin_lock(&sbinfo->stat_lock);
263 sbinfo->free_inodes++;
264 spin_unlock(&sbinfo->stat_lock);
269 * shmem_recalc_inode - recalculate the size of an inode
270 * @inode: inode to recalc
272 * We have to calculate the free blocks since the mm can drop
273 * undirtied hole pages behind our back.
275 * But normally info->alloced == inode->i_mapping->nrpages + info->swapped
276 * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
278 * It has to be called with the spinlock held.
280 static void shmem_recalc_inode(struct inode *inode)
282 struct shmem_inode_info *info = SHMEM_I(inode);
285 freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
287 info->alloced -= freed;
288 shmem_unacct_blocks(info->flags, freed);
289 shmem_free_blocks(inode, freed);
294 * shmem_swp_entry - find the swap vector position in the info structure
295 * @info: info structure for the inode
296 * @index: index of the page to find
297 * @page: optional page to add to the structure. Has to be preset to
300 * If there is no space allocated yet it will return NULL when
301 * page is NULL, else it will use the page for the needed block,
302 * setting it to NULL on return to indicate that it has been used.
304 * The swap vector is organized the following way:
306 * There are SHMEM_NR_DIRECT entries directly stored in the
307 * shmem_inode_info structure. So small files do not need an addional
310 * For pages with index > SHMEM_NR_DIRECT there is the pointer
311 * i_indirect which points to a page which holds in the first half
312 * doubly indirect blocks, in the second half triple indirect blocks:
314 * For an artificial ENTRIES_PER_PAGE = 4 this would lead to the
315 * following layout (for SHMEM_NR_DIRECT == 16):
317 * i_indirect -> dir --> 16-19
330 static swp_entry_t *shmem_swp_entry(struct shmem_inode_info *info, unsigned long index, struct page **page)
332 unsigned long offset;
336 if (index < SHMEM_NR_DIRECT) {
337 shmem_swp_balance_unmap();
338 return info->i_direct+index;
340 if (!info->i_indirect) {
342 info->i_indirect = *page;
345 return NULL; /* need another page */
348 index -= SHMEM_NR_DIRECT;
349 offset = index % ENTRIES_PER_PAGE;
350 index /= ENTRIES_PER_PAGE;
351 dir = shmem_dir_map(info->i_indirect);
353 if (index >= ENTRIES_PER_PAGE/2) {
354 index -= ENTRIES_PER_PAGE/2;
355 dir += ENTRIES_PER_PAGE/2 + index/ENTRIES_PER_PAGE;
356 index %= ENTRIES_PER_PAGE;
363 shmem_dir_unmap(dir);
364 return NULL; /* need another page */
366 shmem_dir_unmap(dir);
367 dir = shmem_dir_map(subdir);
373 if (!page || !(subdir = *page)) {
374 shmem_dir_unmap(dir);
375 return NULL; /* need a page */
380 shmem_dir_unmap(dir);
381 return shmem_swp_map(subdir) + offset;
384 static void shmem_swp_set(struct shmem_inode_info *info, swp_entry_t *entry, unsigned long value)
386 long incdec = value? 1: -1;
389 info->swapped += incdec;
390 if ((unsigned long)(entry - info->i_direct) >= SHMEM_NR_DIRECT) {
391 struct page *page = kmap_atomic_to_page(entry);
392 set_page_private(page, page_private(page) + incdec);
397 * shmem_swp_alloc - get the position of the swap entry for the page.
398 * @info: info structure for the inode
399 * @index: index of the page to find
400 * @sgp: check and recheck i_size? skip allocation?
402 * If the entry does not exist, allocate it.
404 static swp_entry_t *shmem_swp_alloc(struct shmem_inode_info *info, unsigned long index, enum sgp_type sgp)
406 struct inode *inode = &info->vfs_inode;
407 struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
408 struct page *page = NULL;
411 if (sgp != SGP_WRITE &&
412 ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode))
413 return ERR_PTR(-EINVAL);
415 while (!(entry = shmem_swp_entry(info, index, &page))) {
417 return shmem_swp_map(ZERO_PAGE(0));
419 * Test free_blocks against 1 not 0, since we have 1 data
420 * page (and perhaps indirect index pages) yet to allocate:
421 * a waste to allocate index if we cannot allocate data.
423 if (sbinfo->max_blocks) {
424 spin_lock(&sbinfo->stat_lock);
425 if (sbinfo->free_blocks <= 1) {
426 spin_unlock(&sbinfo->stat_lock);
427 return ERR_PTR(-ENOSPC);
429 sbinfo->free_blocks--;
430 inode->i_blocks += BLOCKS_PER_PAGE;
431 spin_unlock(&sbinfo->stat_lock);
434 spin_unlock(&info->lock);
435 page = shmem_dir_alloc(mapping_gfp_mask(inode->i_mapping));
436 spin_lock(&info->lock);
439 shmem_free_blocks(inode, 1);
440 return ERR_PTR(-ENOMEM);
442 if (sgp != SGP_WRITE &&
443 ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
444 entry = ERR_PTR(-EINVAL);
447 if (info->next_index <= index)
448 info->next_index = index + 1;
451 /* another task gave its page, or truncated the file */
452 shmem_free_blocks(inode, 1);
453 shmem_dir_free(page);
455 if (info->next_index <= index && !IS_ERR(entry))
456 info->next_index = index + 1;
461 * shmem_free_swp - free some swap entries in a directory
462 * @dir: pointer to the directory
463 * @edir: pointer after last entry of the directory
464 * @punch_lock: pointer to spinlock when needed for the holepunch case
466 static int shmem_free_swp(swp_entry_t *dir, swp_entry_t *edir,
467 spinlock_t *punch_lock)
469 spinlock_t *punch_unlock = NULL;
473 for (ptr = dir; ptr < edir; ptr++) {
475 if (unlikely(punch_lock)) {
476 punch_unlock = punch_lock;
478 spin_lock(punch_unlock);
482 free_swap_and_cache(*ptr);
483 *ptr = (swp_entry_t){0};
488 spin_unlock(punch_unlock);
492 static int shmem_map_and_free_swp(struct page *subdir, int offset,
493 int limit, struct page ***dir, spinlock_t *punch_lock)
498 ptr = shmem_swp_map(subdir);
499 for (; offset < limit; offset += LATENCY_LIMIT) {
500 int size = limit - offset;
501 if (size > LATENCY_LIMIT)
502 size = LATENCY_LIMIT;
503 freed += shmem_free_swp(ptr+offset, ptr+offset+size,
505 if (need_resched()) {
506 shmem_swp_unmap(ptr);
508 shmem_dir_unmap(*dir);
512 ptr = shmem_swp_map(subdir);
515 shmem_swp_unmap(ptr);
519 static void shmem_free_pages(struct list_head *next)
525 page = container_of(next, struct page, lru);
527 shmem_dir_free(page);
529 if (freed >= LATENCY_LIMIT) {
536 static void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end)
538 struct shmem_inode_info *info = SHMEM_I(inode);
543 unsigned long diroff;
549 LIST_HEAD(pages_to_free);
550 long nr_pages_to_free = 0;
551 long nr_swaps_freed = 0;
555 spinlock_t *needs_lock;
556 spinlock_t *punch_lock;
557 unsigned long upper_limit;
559 inode->i_ctime = inode->i_mtime = CURRENT_TIME;
560 idx = (start + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
561 if (idx >= info->next_index)
564 spin_lock(&info->lock);
565 info->flags |= SHMEM_TRUNCATE;
566 if (likely(end == (loff_t) -1)) {
567 limit = info->next_index;
568 upper_limit = SHMEM_MAX_INDEX;
569 info->next_index = idx;
573 if (end + 1 >= inode->i_size) { /* we may free a little more */
574 limit = (inode->i_size + PAGE_CACHE_SIZE - 1) >>
576 upper_limit = SHMEM_MAX_INDEX;
578 limit = (end + 1) >> PAGE_CACHE_SHIFT;
581 needs_lock = &info->lock;
585 topdir = info->i_indirect;
586 if (topdir && idx <= SHMEM_NR_DIRECT && !punch_hole) {
587 info->i_indirect = NULL;
589 list_add(&topdir->lru, &pages_to_free);
591 spin_unlock(&info->lock);
593 if (info->swapped && idx < SHMEM_NR_DIRECT) {
594 ptr = info->i_direct;
596 if (size > SHMEM_NR_DIRECT)
597 size = SHMEM_NR_DIRECT;
598 nr_swaps_freed = shmem_free_swp(ptr+idx, ptr+size, needs_lock);
602 * If there are no indirect blocks or we are punching a hole
603 * below indirect blocks, nothing to be done.
605 if (!topdir || limit <= SHMEM_NR_DIRECT)
609 * The truncation case has already dropped info->lock, and we're safe
610 * because i_size and next_index have already been lowered, preventing
611 * access beyond. But in the punch_hole case, we still need to take
612 * the lock when updating the swap directory, because there might be
613 * racing accesses by shmem_getpage(SGP_CACHE), shmem_unuse_inode or
614 * shmem_writepage. However, whenever we find we can remove a whole
615 * directory page (not at the misaligned start or end of the range),
616 * we first NULLify its pointer in the level above, and then have no
617 * need to take the lock when updating its contents: needs_lock and
618 * punch_lock (either pointing to info->lock or NULL) manage this.
621 upper_limit -= SHMEM_NR_DIRECT;
622 limit -= SHMEM_NR_DIRECT;
623 idx = (idx > SHMEM_NR_DIRECT)? (idx - SHMEM_NR_DIRECT): 0;
624 offset = idx % ENTRIES_PER_PAGE;
627 dir = shmem_dir_map(topdir);
628 stage = ENTRIES_PER_PAGEPAGE/2;
629 if (idx < ENTRIES_PER_PAGEPAGE/2) {
631 diroff = idx/ENTRIES_PER_PAGE;
633 dir += ENTRIES_PER_PAGE/2;
634 dir += (idx - ENTRIES_PER_PAGEPAGE/2)/ENTRIES_PER_PAGEPAGE;
636 stage += ENTRIES_PER_PAGEPAGE;
639 diroff = ((idx - ENTRIES_PER_PAGEPAGE/2) %
640 ENTRIES_PER_PAGEPAGE) / ENTRIES_PER_PAGE;
641 if (!diroff && !offset && upper_limit >= stage) {
643 spin_lock(needs_lock);
645 spin_unlock(needs_lock);
650 list_add(&middir->lru, &pages_to_free);
652 shmem_dir_unmap(dir);
653 dir = shmem_dir_map(middir);
661 for (; idx < limit; idx += ENTRIES_PER_PAGE, diroff++) {
662 if (unlikely(idx == stage)) {
663 shmem_dir_unmap(dir);
664 dir = shmem_dir_map(topdir) +
665 ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
668 idx += ENTRIES_PER_PAGEPAGE;
672 stage = idx + ENTRIES_PER_PAGEPAGE;
675 needs_lock = &info->lock;
676 if (upper_limit >= stage) {
678 spin_lock(needs_lock);
680 spin_unlock(needs_lock);
685 list_add(&middir->lru, &pages_to_free);
687 shmem_dir_unmap(dir);
689 dir = shmem_dir_map(middir);
692 punch_lock = needs_lock;
693 subdir = dir[diroff];
694 if (subdir && !offset && upper_limit-idx >= ENTRIES_PER_PAGE) {
696 spin_lock(needs_lock);
698 spin_unlock(needs_lock);
703 list_add(&subdir->lru, &pages_to_free);
705 if (subdir && page_private(subdir) /* has swap entries */) {
707 if (size > ENTRIES_PER_PAGE)
708 size = ENTRIES_PER_PAGE;
709 freed = shmem_map_and_free_swp(subdir,
710 offset, size, &dir, punch_lock);
712 dir = shmem_dir_map(middir);
713 nr_swaps_freed += freed;
714 if (offset || punch_lock) {
715 spin_lock(&info->lock);
716 set_page_private(subdir,
717 page_private(subdir) - freed);
718 spin_unlock(&info->lock);
720 BUG_ON(page_private(subdir) != freed);
725 shmem_dir_unmap(dir);
727 if (inode->i_mapping->nrpages && (info->flags & SHMEM_PAGEIN)) {
729 * Call truncate_inode_pages again: racing shmem_unuse_inode
730 * may have swizzled a page in from swap since
731 * truncate_pagecache or generic_delete_inode did it, before we
732 * lowered next_index. Also, though shmem_getpage checks
733 * i_size before adding to cache, no recheck after: so fix the
734 * narrow window there too.
736 * Recalling truncate_inode_pages_range and unmap_mapping_range
737 * every time for punch_hole (which never got a chance to clear
738 * SHMEM_PAGEIN at the start of vmtruncate_range) is expensive,
739 * yet hardly ever necessary: try to optimize them out later.
741 truncate_inode_pages_range(inode->i_mapping, start, end);
743 unmap_mapping_range(inode->i_mapping, start,
747 spin_lock(&info->lock);
748 info->flags &= ~SHMEM_TRUNCATE;
749 info->swapped -= nr_swaps_freed;
750 if (nr_pages_to_free)
751 shmem_free_blocks(inode, nr_pages_to_free);
752 shmem_recalc_inode(inode);
753 spin_unlock(&info->lock);
756 * Empty swap vector directory pages to be freed?
758 if (!list_empty(&pages_to_free)) {
759 pages_to_free.prev->next = NULL;
760 shmem_free_pages(pages_to_free.next);
764 static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
766 struct inode *inode = dentry->d_inode;
767 loff_t newsize = attr->ia_size;
770 error = inode_change_ok(inode, attr);
774 if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)
775 && newsize != inode->i_size) {
776 struct page *page = NULL;
778 if (newsize < inode->i_size) {
780 * If truncating down to a partial page, then
781 * if that page is already allocated, hold it
782 * in memory until the truncation is over, so
783 * truncate_partial_page cannnot miss it were
784 * it assigned to swap.
786 if (newsize & (PAGE_CACHE_SIZE-1)) {
787 (void) shmem_getpage(inode,
788 newsize >> PAGE_CACHE_SHIFT,
789 &page, SGP_READ, NULL);
794 * Reset SHMEM_PAGEIN flag so that shmem_truncate can
795 * detect if any pages might have been added to cache
796 * after truncate_inode_pages. But we needn't bother
797 * if it's being fully truncated to zero-length: the
798 * nrpages check is efficient enough in that case.
801 struct shmem_inode_info *info = SHMEM_I(inode);
802 spin_lock(&info->lock);
803 info->flags &= ~SHMEM_PAGEIN;
804 spin_unlock(&info->lock);
808 /* XXX(truncate): truncate_setsize should be called last */
809 truncate_setsize(inode, newsize);
811 page_cache_release(page);
812 shmem_truncate_range(inode, newsize, (loff_t)-1);
815 setattr_copy(inode, attr);
816 #ifdef CONFIG_TMPFS_POSIX_ACL
817 if (attr->ia_valid & ATTR_MODE)
818 error = generic_acl_chmod(inode);
823 static void shmem_delete_inode(struct inode *inode)
825 struct shmem_inode_info *info = SHMEM_I(inode);
827 if (inode->i_mapping->a_ops == &shmem_aops) {
828 truncate_inode_pages(inode->i_mapping, 0);
829 shmem_unacct_size(info->flags, inode->i_size);
831 shmem_truncate_range(inode, 0, (loff_t)-1);
832 if (!list_empty(&info->swaplist)) {
833 mutex_lock(&shmem_swaplist_mutex);
834 list_del_init(&info->swaplist);
835 mutex_unlock(&shmem_swaplist_mutex);
838 BUG_ON(inode->i_blocks);
839 shmem_free_inode(inode->i_sb);
843 static inline int shmem_find_swp(swp_entry_t entry, swp_entry_t *dir, swp_entry_t *edir)
847 for (ptr = dir; ptr < edir; ptr++) {
848 if (ptr->val == entry.val)
854 static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t entry, struct page *page)
868 ptr = info->i_direct;
869 spin_lock(&info->lock);
870 if (!info->swapped) {
871 list_del_init(&info->swaplist);
874 limit = info->next_index;
876 if (size > SHMEM_NR_DIRECT)
877 size = SHMEM_NR_DIRECT;
878 offset = shmem_find_swp(entry, ptr, ptr+size);
881 if (!info->i_indirect)
884 dir = shmem_dir_map(info->i_indirect);
885 stage = SHMEM_NR_DIRECT + ENTRIES_PER_PAGEPAGE/2;
887 for (idx = SHMEM_NR_DIRECT; idx < limit; idx += ENTRIES_PER_PAGE, dir++) {
888 if (unlikely(idx == stage)) {
889 shmem_dir_unmap(dir-1);
890 if (cond_resched_lock(&info->lock)) {
891 /* check it has not been truncated */
892 if (limit > info->next_index) {
893 limit = info->next_index;
898 dir = shmem_dir_map(info->i_indirect) +
899 ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
902 idx += ENTRIES_PER_PAGEPAGE;
906 stage = idx + ENTRIES_PER_PAGEPAGE;
908 shmem_dir_unmap(dir);
909 dir = shmem_dir_map(subdir);
912 if (subdir && page_private(subdir)) {
913 ptr = shmem_swp_map(subdir);
915 if (size > ENTRIES_PER_PAGE)
916 size = ENTRIES_PER_PAGE;
917 offset = shmem_find_swp(entry, ptr, ptr+size);
918 shmem_swp_unmap(ptr);
920 shmem_dir_unmap(dir);
926 shmem_dir_unmap(dir-1);
928 spin_unlock(&info->lock);
932 inode = igrab(&info->vfs_inode);
933 spin_unlock(&info->lock);
936 * Move _head_ to start search for next from here.
937 * But be careful: shmem_delete_inode checks list_empty without taking
938 * mutex, and there's an instant in list_move_tail when info->swaplist
939 * would appear empty, if it were the only one on shmem_swaplist. We
940 * could avoid doing it if inode NULL; or use this minor optimization.
942 if (shmem_swaplist.next != &info->swaplist)
943 list_move_tail(&shmem_swaplist, &info->swaplist);
944 mutex_unlock(&shmem_swaplist_mutex);
950 * Charge page using GFP_KERNEL while we can wait.
951 * Charged back to the user(not to caller) when swap account is used.
952 * add_to_page_cache() will be called with GFP_NOWAIT.
954 error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL);
957 error = radix_tree_preload(GFP_KERNEL);
959 mem_cgroup_uncharge_cache_page(page);
964 spin_lock(&info->lock);
965 ptr = shmem_swp_entry(info, idx, NULL);
966 if (ptr && ptr->val == entry.val) {
967 error = add_to_page_cache_locked(page, inode->i_mapping,
969 /* does mem_cgroup_uncharge_cache_page on error */
970 } else /* we must compensate for our precharge above */
971 mem_cgroup_uncharge_cache_page(page);
973 if (error == -EEXIST) {
974 struct page *filepage = find_get_page(inode->i_mapping, idx);
978 * There might be a more uptodate page coming down
979 * from a stacked writepage: forget our swappage if so.
981 if (PageUptodate(filepage))
983 page_cache_release(filepage);
987 delete_from_swap_cache(page);
988 set_page_dirty(page);
989 info->flags |= SHMEM_PAGEIN;
990 shmem_swp_set(info, ptr, 0);
992 error = 1; /* not an error, but entry was found */
995 shmem_swp_unmap(ptr);
996 spin_unlock(&info->lock);
997 radix_tree_preload_end();
1000 page_cache_release(page);
1001 iput(inode); /* allows for NULL */
1006 * shmem_unuse() search for an eventually swapped out shmem page.
1008 int shmem_unuse(swp_entry_t entry, struct page *page)
1010 struct list_head *p, *next;
1011 struct shmem_inode_info *info;
1014 mutex_lock(&shmem_swaplist_mutex);
1015 list_for_each_safe(p, next, &shmem_swaplist) {
1016 info = list_entry(p, struct shmem_inode_info, swaplist);
1017 found = shmem_unuse_inode(info, entry, page);
1022 mutex_unlock(&shmem_swaplist_mutex);
1024 * Can some race bring us here? We've been holding page lock,
1025 * so I think not; but would rather try again later than BUG()
1028 page_cache_release(page);
1030 return (found < 0) ? found : 0;
1034 * Move the page from the page cache to the swap cache.
1036 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
1038 struct shmem_inode_info *info;
1039 swp_entry_t *entry, swap;
1040 struct address_space *mapping;
1041 unsigned long index;
1042 struct inode *inode;
1044 BUG_ON(!PageLocked(page));
1045 mapping = page->mapping;
1046 index = page->index;
1047 inode = mapping->host;
1048 info = SHMEM_I(inode);
1049 if (info->flags & VM_LOCKED)
1051 if (!total_swap_pages)
1055 * shmem_backing_dev_info's capabilities prevent regular writeback or
1056 * sync from ever calling shmem_writepage; but a stacking filesystem
1057 * may use the ->writepage of its underlying filesystem, in which case
1058 * tmpfs should write out to swap only in response to memory pressure,
1059 * and not for the writeback threads or sync. However, in those cases,
1060 * we do still want to check if there's a redundant swappage to be
1063 if (wbc->for_reclaim)
1064 swap = get_swap_page();
1068 spin_lock(&info->lock);
1069 if (index >= info->next_index) {
1070 BUG_ON(!(info->flags & SHMEM_TRUNCATE));
1073 entry = shmem_swp_entry(info, index, NULL);
1076 * The more uptodate page coming down from a stacked
1077 * writepage should replace our old swappage.
1079 free_swap_and_cache(*entry);
1080 shmem_swp_set(info, entry, 0);
1082 shmem_recalc_inode(inode);
1084 if (swap.val && add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
1085 remove_from_page_cache(page);
1086 shmem_swp_set(info, entry, swap.val);
1087 shmem_swp_unmap(entry);
1088 if (list_empty(&info->swaplist))
1089 inode = igrab(inode);
1092 spin_unlock(&info->lock);
1093 swap_shmem_alloc(swap);
1094 BUG_ON(page_mapped(page));
1095 page_cache_release(page); /* pagecache ref */
1096 swap_writepage(page, wbc);
1098 mutex_lock(&shmem_swaplist_mutex);
1099 /* move instead of add in case we're racing */
1100 list_move_tail(&info->swaplist, &shmem_swaplist);
1101 mutex_unlock(&shmem_swaplist_mutex);
1107 shmem_swp_unmap(entry);
1109 spin_unlock(&info->lock);
1111 * add_to_swap_cache() doesn't return -EEXIST, so we can safely
1112 * clear SWAP_HAS_CACHE flag.
1114 swapcache_free(swap, NULL);
1116 set_page_dirty(page);
1117 if (wbc->for_reclaim)
1118 return AOP_WRITEPAGE_ACTIVATE; /* Return with page locked */
1125 static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1129 if (!mpol || mpol->mode == MPOL_DEFAULT)
1130 return; /* show nothing */
1132 mpol_to_str(buffer, sizeof(buffer), mpol, 1);
1134 seq_printf(seq, ",mpol=%s", buffer);
1137 static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1139 struct mempolicy *mpol = NULL;
1141 spin_lock(&sbinfo->stat_lock); /* prevent replace/use races */
1142 mpol = sbinfo->mpol;
1144 spin_unlock(&sbinfo->stat_lock);
1148 #endif /* CONFIG_TMPFS */
1150 static struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
1151 struct shmem_inode_info *info, unsigned long idx)
1153 struct mempolicy mpol, *spol;
1154 struct vm_area_struct pvma;
1157 spol = mpol_cond_copy(&mpol,
1158 mpol_shared_policy_lookup(&info->policy, idx));
1160 /* Create a pseudo vma that just contains the policy */
1162 pvma.vm_pgoff = idx;
1164 pvma.vm_policy = spol;
1165 page = swapin_readahead(entry, gfp, &pvma, 0);
1169 static struct page *shmem_alloc_page(gfp_t gfp,
1170 struct shmem_inode_info *info, unsigned long idx)
1172 struct vm_area_struct pvma;
1174 /* Create a pseudo vma that just contains the policy */
1176 pvma.vm_pgoff = idx;
1178 pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
1181 * alloc_page_vma() will drop the shared policy reference
1183 return alloc_page_vma(gfp, &pvma, 0);
1185 #else /* !CONFIG_NUMA */
1187 static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *p)
1190 #endif /* CONFIG_TMPFS */
1192 static inline struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
1193 struct shmem_inode_info *info, unsigned long idx)
1195 return swapin_readahead(entry, gfp, NULL, 0);
1198 static inline struct page *shmem_alloc_page(gfp_t gfp,
1199 struct shmem_inode_info *info, unsigned long idx)
1201 return alloc_page(gfp);
1203 #endif /* CONFIG_NUMA */
1205 #if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS)
1206 static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1213 * shmem_getpage - either get the page from swap or allocate a new one
1215 * If we allocate a new one we do not mark it dirty. That's up to the
1216 * vm. If we swap it in we mark it dirty since we also free the swap
1217 * entry since a page cannot live in both the swap and page cache
1219 static int shmem_getpage(struct inode *inode, unsigned long idx,
1220 struct page **pagep, enum sgp_type sgp, int *type)
1222 struct address_space *mapping = inode->i_mapping;
1223 struct shmem_inode_info *info = SHMEM_I(inode);
1224 struct shmem_sb_info *sbinfo;
1225 struct page *filepage = *pagep;
1226 struct page *swappage;
1232 if (idx >= SHMEM_MAX_INDEX)
1239 * Normally, filepage is NULL on entry, and either found
1240 * uptodate immediately, or allocated and zeroed, or read
1241 * in under swappage, which is then assigned to filepage.
1242 * But shmem_readpage (required for splice) passes in a locked
1243 * filepage, which may be found not uptodate by other callers
1244 * too, and may need to be copied from the swappage read in.
1248 filepage = find_lock_page(mapping, idx);
1249 if (filepage && PageUptodate(filepage))
1252 gfp = mapping_gfp_mask(mapping);
1255 * Try to preload while we can wait, to not make a habit of
1256 * draining atomic reserves; but don't latch on to this cpu.
1258 error = radix_tree_preload(gfp & ~__GFP_HIGHMEM);
1261 radix_tree_preload_end();
1264 spin_lock(&info->lock);
1265 shmem_recalc_inode(inode);
1266 entry = shmem_swp_alloc(info, idx, sgp);
1267 if (IS_ERR(entry)) {
1268 spin_unlock(&info->lock);
1269 error = PTR_ERR(entry);
1275 /* Look it up and read it in.. */
1276 swappage = lookup_swap_cache(swap);
1278 shmem_swp_unmap(entry);
1279 /* here we actually do the io */
1280 if (type && !(*type & VM_FAULT_MAJOR)) {
1281 __count_vm_event(PGMAJFAULT);
1282 *type |= VM_FAULT_MAJOR;
1284 spin_unlock(&info->lock);
1285 swappage = shmem_swapin(swap, gfp, info, idx);
1287 spin_lock(&info->lock);
1288 entry = shmem_swp_alloc(info, idx, sgp);
1290 error = PTR_ERR(entry);
1292 if (entry->val == swap.val)
1294 shmem_swp_unmap(entry);
1296 spin_unlock(&info->lock);
1301 wait_on_page_locked(swappage);
1302 page_cache_release(swappage);
1306 /* We have to do this with page locked to prevent races */
1307 if (!trylock_page(swappage)) {
1308 shmem_swp_unmap(entry);
1309 spin_unlock(&info->lock);
1310 wait_on_page_locked(swappage);
1311 page_cache_release(swappage);
1314 if (PageWriteback(swappage)) {
1315 shmem_swp_unmap(entry);
1316 spin_unlock(&info->lock);
1317 wait_on_page_writeback(swappage);
1318 unlock_page(swappage);
1319 page_cache_release(swappage);
1322 if (!PageUptodate(swappage)) {
1323 shmem_swp_unmap(entry);
1324 spin_unlock(&info->lock);
1325 unlock_page(swappage);
1326 page_cache_release(swappage);
1332 shmem_swp_set(info, entry, 0);
1333 shmem_swp_unmap(entry);
1334 delete_from_swap_cache(swappage);
1335 spin_unlock(&info->lock);
1336 copy_highpage(filepage, swappage);
1337 unlock_page(swappage);
1338 page_cache_release(swappage);
1339 flush_dcache_page(filepage);
1340 SetPageUptodate(filepage);
1341 set_page_dirty(filepage);
1343 } else if (!(error = add_to_page_cache_locked(swappage, mapping,
1344 idx, GFP_NOWAIT))) {
1345 info->flags |= SHMEM_PAGEIN;
1346 shmem_swp_set(info, entry, 0);
1347 shmem_swp_unmap(entry);
1348 delete_from_swap_cache(swappage);
1349 spin_unlock(&info->lock);
1350 filepage = swappage;
1351 set_page_dirty(filepage);
1354 shmem_swp_unmap(entry);
1355 spin_unlock(&info->lock);
1356 if (error == -ENOMEM) {
1358 * reclaim from proper memory cgroup and
1359 * call memcg's OOM if needed.
1361 error = mem_cgroup_shmem_charge_fallback(
1366 unlock_page(swappage);
1367 page_cache_release(swappage);
1371 unlock_page(swappage);
1372 page_cache_release(swappage);
1375 } else if (sgp == SGP_READ && !filepage) {
1376 shmem_swp_unmap(entry);
1377 filepage = find_get_page(mapping, idx);
1379 (!PageUptodate(filepage) || !trylock_page(filepage))) {
1380 spin_unlock(&info->lock);
1381 wait_on_page_locked(filepage);
1382 page_cache_release(filepage);
1386 spin_unlock(&info->lock);
1388 shmem_swp_unmap(entry);
1389 sbinfo = SHMEM_SB(inode->i_sb);
1390 if (sbinfo->max_blocks) {
1391 spin_lock(&sbinfo->stat_lock);
1392 if (sbinfo->free_blocks == 0 ||
1393 shmem_acct_block(info->flags)) {
1394 spin_unlock(&sbinfo->stat_lock);
1395 spin_unlock(&info->lock);
1399 sbinfo->free_blocks--;
1400 inode->i_blocks += BLOCKS_PER_PAGE;
1401 spin_unlock(&sbinfo->stat_lock);
1402 } else if (shmem_acct_block(info->flags)) {
1403 spin_unlock(&info->lock);
1411 spin_unlock(&info->lock);
1412 filepage = shmem_alloc_page(gfp, info, idx);
1414 shmem_unacct_blocks(info->flags, 1);
1415 shmem_free_blocks(inode, 1);
1419 SetPageSwapBacked(filepage);
1421 /* Precharge page while we can wait, compensate after */
1422 error = mem_cgroup_cache_charge(filepage, current->mm,
1425 page_cache_release(filepage);
1426 shmem_unacct_blocks(info->flags, 1);
1427 shmem_free_blocks(inode, 1);
1432 spin_lock(&info->lock);
1433 entry = shmem_swp_alloc(info, idx, sgp);
1435 error = PTR_ERR(entry);
1438 shmem_swp_unmap(entry);
1440 ret = error || swap.val;
1442 mem_cgroup_uncharge_cache_page(filepage);
1444 ret = add_to_page_cache_lru(filepage, mapping,
1447 * At add_to_page_cache_lru() failure, uncharge will
1448 * be done automatically.
1451 spin_unlock(&info->lock);
1452 page_cache_release(filepage);
1453 shmem_unacct_blocks(info->flags, 1);
1454 shmem_free_blocks(inode, 1);
1460 info->flags |= SHMEM_PAGEIN;
1464 spin_unlock(&info->lock);
1465 clear_highpage(filepage);
1466 flush_dcache_page(filepage);
1467 SetPageUptodate(filepage);
1468 if (sgp == SGP_DIRTY)
1469 set_page_dirty(filepage);
1476 if (*pagep != filepage) {
1477 unlock_page(filepage);
1478 page_cache_release(filepage);
1483 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1485 struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1489 if (((loff_t)vmf->pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
1490 return VM_FAULT_SIGBUS;
1492 error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
1494 return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1496 return ret | VM_FAULT_LOCKED;
1500 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *new)
1502 struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1503 return mpol_set_shared_policy(&SHMEM_I(i)->policy, vma, new);
1506 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
1509 struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1512 idx = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1513 return mpol_shared_policy_lookup(&SHMEM_I(i)->policy, idx);
1517 int shmem_lock(struct file *file, int lock, struct user_struct *user)
1519 struct inode *inode = file->f_path.dentry->d_inode;
1520 struct shmem_inode_info *info = SHMEM_I(inode);
1521 int retval = -ENOMEM;
1523 spin_lock(&info->lock);
1524 if (lock && !(info->flags & VM_LOCKED)) {
1525 if (!user_shm_lock(inode->i_size, user))
1527 info->flags |= VM_LOCKED;
1528 mapping_set_unevictable(file->f_mapping);
1530 if (!lock && (info->flags & VM_LOCKED) && user) {
1531 user_shm_unlock(inode->i_size, user);
1532 info->flags &= ~VM_LOCKED;
1533 mapping_clear_unevictable(file->f_mapping);
1534 scan_mapping_unevictable_pages(file->f_mapping);
1539 spin_unlock(&info->lock);
1543 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1545 file_accessed(file);
1546 vma->vm_ops = &shmem_vm_ops;
1547 vma->vm_flags |= VM_CAN_NONLINEAR;
1551 static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
1552 int mode, dev_t dev, unsigned long flags)
1554 struct inode *inode;
1555 struct shmem_inode_info *info;
1556 struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1558 if (shmem_reserve_inode(sb))
1561 inode = new_inode(sb);
1563 inode_init_owner(inode, dir, mode);
1564 inode->i_blocks = 0;
1565 inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1566 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1567 inode->i_generation = get_seconds();
1568 info = SHMEM_I(inode);
1569 memset(info, 0, (char *)inode - (char *)info);
1570 spin_lock_init(&info->lock);
1571 info->flags = flags & VM_NORESERVE;
1572 INIT_LIST_HEAD(&info->swaplist);
1573 cache_no_acl(inode);
1575 switch (mode & S_IFMT) {
1577 inode->i_op = &shmem_special_inode_operations;
1578 init_special_inode(inode, mode, dev);
1581 inode->i_mapping->a_ops = &shmem_aops;
1582 inode->i_op = &shmem_inode_operations;
1583 inode->i_fop = &shmem_file_operations;
1584 mpol_shared_policy_init(&info->policy,
1585 shmem_get_sbmpol(sbinfo));
1589 /* Some things misbehave if size == 0 on a directory */
1590 inode->i_size = 2 * BOGO_DIRENT_SIZE;
1591 inode->i_op = &shmem_dir_inode_operations;
1592 inode->i_fop = &simple_dir_operations;
1596 * Must not load anything in the rbtree,
1597 * mpol_free_shared_policy will not be called.
1599 mpol_shared_policy_init(&info->policy, NULL);
1603 shmem_free_inode(sb);
1608 static const struct inode_operations shmem_symlink_inode_operations;
1609 static const struct inode_operations shmem_symlink_inline_operations;
1612 * Normally tmpfs avoids the use of shmem_readpage and shmem_write_begin;
1613 * but providing them allows a tmpfs file to be used for splice, sendfile, and
1614 * below the loop driver, in the generic fashion that many filesystems support.
1616 static int shmem_readpage(struct file *file, struct page *page)
1618 struct inode *inode = page->mapping->host;
1619 int error = shmem_getpage(inode, page->index, &page, SGP_CACHE, NULL);
1625 shmem_write_begin(struct file *file, struct address_space *mapping,
1626 loff_t pos, unsigned len, unsigned flags,
1627 struct page **pagep, void **fsdata)
1629 struct inode *inode = mapping->host;
1630 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1632 return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
1636 shmem_write_end(struct file *file, struct address_space *mapping,
1637 loff_t pos, unsigned len, unsigned copied,
1638 struct page *page, void *fsdata)
1640 struct inode *inode = mapping->host;
1642 if (pos + copied > inode->i_size)
1643 i_size_write(inode, pos + copied);
1645 set_page_dirty(page);
1647 page_cache_release(page);
1652 static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1654 struct inode *inode = filp->f_path.dentry->d_inode;
1655 struct address_space *mapping = inode->i_mapping;
1656 unsigned long index, offset;
1657 enum sgp_type sgp = SGP_READ;
1660 * Might this read be for a stacking filesystem? Then when reading
1661 * holes of a sparse file, we actually need to allocate those pages,
1662 * and even mark them dirty, so it cannot exceed the max_blocks limit.
1664 if (segment_eq(get_fs(), KERNEL_DS))
1667 index = *ppos >> PAGE_CACHE_SHIFT;
1668 offset = *ppos & ~PAGE_CACHE_MASK;
1671 struct page *page = NULL;
1672 unsigned long end_index, nr, ret;
1673 loff_t i_size = i_size_read(inode);
1675 end_index = i_size >> PAGE_CACHE_SHIFT;
1676 if (index > end_index)
1678 if (index == end_index) {
1679 nr = i_size & ~PAGE_CACHE_MASK;
1684 desc->error = shmem_getpage(inode, index, &page, sgp, NULL);
1686 if (desc->error == -EINVAL)
1694 * We must evaluate after, since reads (unlike writes)
1695 * are called without i_mutex protection against truncate
1697 nr = PAGE_CACHE_SIZE;
1698 i_size = i_size_read(inode);
1699 end_index = i_size >> PAGE_CACHE_SHIFT;
1700 if (index == end_index) {
1701 nr = i_size & ~PAGE_CACHE_MASK;
1704 page_cache_release(page);
1712 * If users can be writing to this page using arbitrary
1713 * virtual addresses, take care about potential aliasing
1714 * before reading the page on the kernel side.
1716 if (mapping_writably_mapped(mapping))
1717 flush_dcache_page(page);
1719 * Mark the page accessed if we read the beginning.
1722 mark_page_accessed(page);
1724 page = ZERO_PAGE(0);
1725 page_cache_get(page);
1729 * Ok, we have the page, and it's up-to-date, so
1730 * now we can copy it to user space...
1732 * The actor routine returns how many bytes were actually used..
1733 * NOTE! This may not be the same as how much of a user buffer
1734 * we filled up (we may be padding etc), so we can only update
1735 * "pos" here (the actor routine has to update the user buffer
1736 * pointers and the remaining count).
1738 ret = actor(desc, page, offset, nr);
1740 index += offset >> PAGE_CACHE_SHIFT;
1741 offset &= ~PAGE_CACHE_MASK;
1743 page_cache_release(page);
1744 if (ret != nr || !desc->count)
1750 *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1751 file_accessed(filp);
1754 static ssize_t shmem_file_aio_read(struct kiocb *iocb,
1755 const struct iovec *iov, unsigned long nr_segs, loff_t pos)
1757 struct file *filp = iocb->ki_filp;
1761 loff_t *ppos = &iocb->ki_pos;
1763 retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1767 for (seg = 0; seg < nr_segs; seg++) {
1768 read_descriptor_t desc;
1771 desc.arg.buf = iov[seg].iov_base;
1772 desc.count = iov[seg].iov_len;
1773 if (desc.count == 0)
1776 do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1777 retval += desc.written;
1779 retval = retval ?: desc.error;
1788 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1790 struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1792 buf->f_type = TMPFS_MAGIC;
1793 buf->f_bsize = PAGE_CACHE_SIZE;
1794 buf->f_namelen = NAME_MAX;
1795 spin_lock(&sbinfo->stat_lock);
1796 if (sbinfo->max_blocks) {
1797 buf->f_blocks = sbinfo->max_blocks;
1798 buf->f_bavail = buf->f_bfree = sbinfo->free_blocks;
1800 if (sbinfo->max_inodes) {
1801 buf->f_files = sbinfo->max_inodes;
1802 buf->f_ffree = sbinfo->free_inodes;
1804 /* else leave those fields 0 like simple_statfs */
1805 spin_unlock(&sbinfo->stat_lock);
1810 * File creation. Allocate an inode, and we're done..
1813 shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
1815 struct inode *inode;
1816 int error = -ENOSPC;
1818 inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
1820 error = security_inode_init_security(inode, dir, NULL, NULL,
1823 if (error != -EOPNOTSUPP) {
1828 #ifdef CONFIG_TMPFS_POSIX_ACL
1829 error = generic_acl_init(inode, dir);
1837 dir->i_size += BOGO_DIRENT_SIZE;
1838 dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1839 d_instantiate(dentry, inode);
1840 dget(dentry); /* Extra count - pin the dentry in core */
1845 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, int mode)
1849 if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1855 static int shmem_create(struct inode *dir, struct dentry *dentry, int mode,
1856 struct nameidata *nd)
1858 return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1864 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1866 struct inode *inode = old_dentry->d_inode;
1870 * No ordinary (disk based) filesystem counts links as inodes;
1871 * but each new link needs a new dentry, pinning lowmem, and
1872 * tmpfs dentries cannot be pruned until they are unlinked.
1874 ret = shmem_reserve_inode(inode->i_sb);
1878 dir->i_size += BOGO_DIRENT_SIZE;
1879 inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1881 atomic_inc(&inode->i_count); /* New dentry reference */
1882 dget(dentry); /* Extra pinning count for the created dentry */
1883 d_instantiate(dentry, inode);
1888 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
1890 struct inode *inode = dentry->d_inode;
1892 if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
1893 shmem_free_inode(inode->i_sb);
1895 dir->i_size -= BOGO_DIRENT_SIZE;
1896 inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1898 dput(dentry); /* Undo the count from "create" - this does all the work */
1902 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
1904 if (!simple_empty(dentry))
1907 drop_nlink(dentry->d_inode);
1909 return shmem_unlink(dir, dentry);
1913 * The VFS layer already does all the dentry stuff for rename,
1914 * we just have to decrement the usage count for the target if
1915 * it exists so that the VFS layer correctly free's it when it
1918 static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
1920 struct inode *inode = old_dentry->d_inode;
1921 int they_are_dirs = S_ISDIR(inode->i_mode);
1923 if (!simple_empty(new_dentry))
1926 if (new_dentry->d_inode) {
1927 (void) shmem_unlink(new_dir, new_dentry);
1929 drop_nlink(old_dir);
1930 } else if (they_are_dirs) {
1931 drop_nlink(old_dir);
1935 old_dir->i_size -= BOGO_DIRENT_SIZE;
1936 new_dir->i_size += BOGO_DIRENT_SIZE;
1937 old_dir->i_ctime = old_dir->i_mtime =
1938 new_dir->i_ctime = new_dir->i_mtime =
1939 inode->i_ctime = CURRENT_TIME;
1943 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
1947 struct inode *inode;
1948 struct page *page = NULL;
1950 struct shmem_inode_info *info;
1952 len = strlen(symname) + 1;
1953 if (len > PAGE_CACHE_SIZE)
1954 return -ENAMETOOLONG;
1956 inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE);
1960 error = security_inode_init_security(inode, dir, NULL, NULL,
1963 if (error != -EOPNOTSUPP) {
1970 info = SHMEM_I(inode);
1971 inode->i_size = len-1;
1972 if (len <= (char *)inode - (char *)info) {
1974 memcpy(info, symname, len);
1975 inode->i_op = &shmem_symlink_inline_operations;
1977 error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
1982 inode->i_mapping->a_ops = &shmem_aops;
1983 inode->i_op = &shmem_symlink_inode_operations;
1984 kaddr = kmap_atomic(page, KM_USER0);
1985 memcpy(kaddr, symname, len);
1986 kunmap_atomic(kaddr, KM_USER0);
1987 set_page_dirty(page);
1989 page_cache_release(page);
1991 dir->i_size += BOGO_DIRENT_SIZE;
1992 dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1993 d_instantiate(dentry, inode);
1998 static void *shmem_follow_link_inline(struct dentry *dentry, struct nameidata *nd)
2000 nd_set_link(nd, (char *)SHMEM_I(dentry->d_inode));
2004 static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
2006 struct page *page = NULL;
2007 int res = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
2008 nd_set_link(nd, res ? ERR_PTR(res) : kmap(page));
2014 static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
2016 if (!IS_ERR(nd_get_link(nd))) {
2017 struct page *page = cookie;
2019 mark_page_accessed(page);
2020 page_cache_release(page);
2024 static const struct inode_operations shmem_symlink_inline_operations = {
2025 .readlink = generic_readlink,
2026 .follow_link = shmem_follow_link_inline,
2029 static const struct inode_operations shmem_symlink_inode_operations = {
2030 .readlink = generic_readlink,
2031 .follow_link = shmem_follow_link,
2032 .put_link = shmem_put_link,
2035 #ifdef CONFIG_TMPFS_POSIX_ACL
2037 * Superblocks without xattr inode operations will get security.* xattr
2038 * support from the VFS "for free". As soon as we have any other xattrs
2039 * like ACLs, we also need to implement the security.* handlers at
2040 * filesystem level, though.
2043 static size_t shmem_xattr_security_list(struct dentry *dentry, char *list,
2044 size_t list_len, const char *name,
2045 size_t name_len, int handler_flags)
2047 return security_inode_listsecurity(dentry->d_inode, list, list_len);
2050 static int shmem_xattr_security_get(struct dentry *dentry, const char *name,
2051 void *buffer, size_t size, int handler_flags)
2053 if (strcmp(name, "") == 0)
2055 return xattr_getsecurity(dentry->d_inode, name, buffer, size);
2058 static int shmem_xattr_security_set(struct dentry *dentry, const char *name,
2059 const void *value, size_t size, int flags, int handler_flags)
2061 if (strcmp(name, "") == 0)
2063 return security_inode_setsecurity(dentry->d_inode, name, value,
2067 static const struct xattr_handler shmem_xattr_security_handler = {
2068 .prefix = XATTR_SECURITY_PREFIX,
2069 .list = shmem_xattr_security_list,
2070 .get = shmem_xattr_security_get,
2071 .set = shmem_xattr_security_set,
2074 static const struct xattr_handler *shmem_xattr_handlers[] = {
2075 &generic_acl_access_handler,
2076 &generic_acl_default_handler,
2077 &shmem_xattr_security_handler,
2082 static struct dentry *shmem_get_parent(struct dentry *child)
2084 return ERR_PTR(-ESTALE);
2087 static int shmem_match(struct inode *ino, void *vfh)
2091 inum = (inum << 32) | fh[1];
2092 return ino->i_ino == inum && fh[0] == ino->i_generation;
2095 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
2096 struct fid *fid, int fh_len, int fh_type)
2098 struct inode *inode;
2099 struct dentry *dentry = NULL;
2100 u64 inum = fid->raw[2];
2101 inum = (inum << 32) | fid->raw[1];
2106 inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
2107 shmem_match, fid->raw);
2109 dentry = d_find_alias(inode);
2116 static int shmem_encode_fh(struct dentry *dentry, __u32 *fh, int *len,
2119 struct inode *inode = dentry->d_inode;
2124 if (hlist_unhashed(&inode->i_hash)) {
2125 /* Unfortunately insert_inode_hash is not idempotent,
2126 * so as we hash inodes here rather than at creation
2127 * time, we need a lock to ensure we only try
2130 static DEFINE_SPINLOCK(lock);
2132 if (hlist_unhashed(&inode->i_hash))
2133 __insert_inode_hash(inode,
2134 inode->i_ino + inode->i_generation);
2138 fh[0] = inode->i_generation;
2139 fh[1] = inode->i_ino;
2140 fh[2] = ((__u64)inode->i_ino) >> 32;
2146 static const struct export_operations shmem_export_ops = {
2147 .get_parent = shmem_get_parent,
2148 .encode_fh = shmem_encode_fh,
2149 .fh_to_dentry = shmem_fh_to_dentry,
2152 static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
2155 char *this_char, *value, *rest;
2157 while (options != NULL) {
2158 this_char = options;
2161 * NUL-terminate this option: unfortunately,
2162 * mount options form a comma-separated list,
2163 * but mpol's nodelist may also contain commas.
2165 options = strchr(options, ',');
2166 if (options == NULL)
2169 if (!isdigit(*options)) {
2176 if ((value = strchr(this_char,'=')) != NULL) {
2180 "tmpfs: No value for mount option '%s'\n",
2185 if (!strcmp(this_char,"size")) {
2186 unsigned long long size;
2187 size = memparse(value,&rest);
2189 size <<= PAGE_SHIFT;
2190 size *= totalram_pages;
2196 sbinfo->max_blocks =
2197 DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
2198 } else if (!strcmp(this_char,"nr_blocks")) {
2199 sbinfo->max_blocks = memparse(value, &rest);
2202 } else if (!strcmp(this_char,"nr_inodes")) {
2203 sbinfo->max_inodes = memparse(value, &rest);
2206 } else if (!strcmp(this_char,"mode")) {
2209 sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
2212 } else if (!strcmp(this_char,"uid")) {
2215 sbinfo->uid = simple_strtoul(value, &rest, 0);
2218 } else if (!strcmp(this_char,"gid")) {
2221 sbinfo->gid = simple_strtoul(value, &rest, 0);
2224 } else if (!strcmp(this_char,"mpol")) {
2225 if (mpol_parse_str(value, &sbinfo->mpol, 1))
2228 printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2236 printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2242 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2244 struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2245 struct shmem_sb_info config = *sbinfo;
2246 unsigned long blocks;
2247 unsigned long inodes;
2248 int error = -EINVAL;
2250 if (shmem_parse_options(data, &config, true))
2253 spin_lock(&sbinfo->stat_lock);
2254 blocks = sbinfo->max_blocks - sbinfo->free_blocks;
2255 inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2256 if (config.max_blocks < blocks)
2258 if (config.max_inodes < inodes)
2261 * Those tests also disallow limited->unlimited while any are in
2262 * use, so i_blocks will always be zero when max_blocks is zero;
2263 * but we must separately disallow unlimited->limited, because
2264 * in that case we have no record of how much is already in use.
2266 if (config.max_blocks && !sbinfo->max_blocks)
2268 if (config.max_inodes && !sbinfo->max_inodes)
2272 sbinfo->max_blocks = config.max_blocks;
2273 sbinfo->free_blocks = config.max_blocks - blocks;
2274 sbinfo->max_inodes = config.max_inodes;
2275 sbinfo->free_inodes = config.max_inodes - inodes;
2277 mpol_put(sbinfo->mpol);
2278 sbinfo->mpol = config.mpol; /* transfers initial ref */
2280 spin_unlock(&sbinfo->stat_lock);
2284 static int shmem_show_options(struct seq_file *seq, struct vfsmount *vfs)
2286 struct shmem_sb_info *sbinfo = SHMEM_SB(vfs->mnt_sb);
2288 if (sbinfo->max_blocks != shmem_default_max_blocks())
2289 seq_printf(seq, ",size=%luk",
2290 sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
2291 if (sbinfo->max_inodes != shmem_default_max_inodes())
2292 seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
2293 if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
2294 seq_printf(seq, ",mode=%03o", sbinfo->mode);
2295 if (sbinfo->uid != 0)
2296 seq_printf(seq, ",uid=%u", sbinfo->uid);
2297 if (sbinfo->gid != 0)
2298 seq_printf(seq, ",gid=%u", sbinfo->gid);
2299 shmem_show_mpol(seq, sbinfo->mpol);
2302 #endif /* CONFIG_TMPFS */
2304 static void shmem_put_super(struct super_block *sb)
2306 kfree(sb->s_fs_info);
2307 sb->s_fs_info = NULL;
2310 int shmem_fill_super(struct super_block *sb, void *data, int silent)
2312 struct inode *inode;
2313 struct dentry *root;
2314 struct shmem_sb_info *sbinfo;
2317 /* Round up to L1_CACHE_BYTES to resist false sharing */
2318 sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
2319 L1_CACHE_BYTES), GFP_KERNEL);
2323 sbinfo->mode = S_IRWXUGO | S_ISVTX;
2324 sbinfo->uid = current_fsuid();
2325 sbinfo->gid = current_fsgid();
2326 sb->s_fs_info = sbinfo;
2330 * Per default we only allow half of the physical ram per
2331 * tmpfs instance, limiting inodes to one per page of lowmem;
2332 * but the internal instance is left unlimited.
2334 if (!(sb->s_flags & MS_NOUSER)) {
2335 sbinfo->max_blocks = shmem_default_max_blocks();
2336 sbinfo->max_inodes = shmem_default_max_inodes();
2337 if (shmem_parse_options(data, sbinfo, false)) {
2342 sb->s_export_op = &shmem_export_ops;
2344 sb->s_flags |= MS_NOUSER;
2347 spin_lock_init(&sbinfo->stat_lock);
2348 sbinfo->free_blocks = sbinfo->max_blocks;
2349 sbinfo->free_inodes = sbinfo->max_inodes;
2351 sb->s_maxbytes = SHMEM_MAX_BYTES;
2352 sb->s_blocksize = PAGE_CACHE_SIZE;
2353 sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2354 sb->s_magic = TMPFS_MAGIC;
2355 sb->s_op = &shmem_ops;
2356 sb->s_time_gran = 1;
2357 #ifdef CONFIG_TMPFS_POSIX_ACL
2358 sb->s_xattr = shmem_xattr_handlers;
2359 sb->s_flags |= MS_POSIXACL;
2362 inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
2365 inode->i_uid = sbinfo->uid;
2366 inode->i_gid = sbinfo->gid;
2367 root = d_alloc_root(inode);
2376 shmem_put_super(sb);
2380 static struct kmem_cache *shmem_inode_cachep;
2382 static struct inode *shmem_alloc_inode(struct super_block *sb)
2384 struct shmem_inode_info *p;
2385 p = (struct shmem_inode_info *)kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2388 return &p->vfs_inode;
2391 static void shmem_destroy_inode(struct inode *inode)
2393 if ((inode->i_mode & S_IFMT) == S_IFREG) {
2394 /* only struct inode is valid if it's an inline symlink */
2395 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2397 kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2400 static void init_once(void *foo)
2402 struct shmem_inode_info *p = (struct shmem_inode_info *) foo;
2404 inode_init_once(&p->vfs_inode);
2407 static int init_inodecache(void)
2409 shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2410 sizeof(struct shmem_inode_info),
2411 0, SLAB_PANIC, init_once);
2415 static void destroy_inodecache(void)
2417 kmem_cache_destroy(shmem_inode_cachep);
2420 static const struct address_space_operations shmem_aops = {
2421 .writepage = shmem_writepage,
2422 .set_page_dirty = __set_page_dirty_no_writeback,
2424 .readpage = shmem_readpage,
2425 .write_begin = shmem_write_begin,
2426 .write_end = shmem_write_end,
2428 .migratepage = migrate_page,
2429 .error_remove_page = generic_error_remove_page,
2432 static const struct file_operations shmem_file_operations = {
2435 .llseek = generic_file_llseek,
2436 .read = do_sync_read,
2437 .write = do_sync_write,
2438 .aio_read = shmem_file_aio_read,
2439 .aio_write = generic_file_aio_write,
2440 .fsync = noop_fsync,
2441 .splice_read = generic_file_splice_read,
2442 .splice_write = generic_file_splice_write,
2446 static const struct inode_operations shmem_inode_operations = {
2447 .setattr = shmem_notify_change,
2448 .truncate_range = shmem_truncate_range,
2449 #ifdef CONFIG_TMPFS_POSIX_ACL
2450 .setxattr = generic_setxattr,
2451 .getxattr = generic_getxattr,
2452 .listxattr = generic_listxattr,
2453 .removexattr = generic_removexattr,
2454 .check_acl = generic_check_acl,
2459 static const struct inode_operations shmem_dir_inode_operations = {
2461 .create = shmem_create,
2462 .lookup = simple_lookup,
2464 .unlink = shmem_unlink,
2465 .symlink = shmem_symlink,
2466 .mkdir = shmem_mkdir,
2467 .rmdir = shmem_rmdir,
2468 .mknod = shmem_mknod,
2469 .rename = shmem_rename,
2471 #ifdef CONFIG_TMPFS_POSIX_ACL
2472 .setattr = shmem_notify_change,
2473 .setxattr = generic_setxattr,
2474 .getxattr = generic_getxattr,
2475 .listxattr = generic_listxattr,
2476 .removexattr = generic_removexattr,
2477 .check_acl = generic_check_acl,
2481 static const struct inode_operations shmem_special_inode_operations = {
2482 #ifdef CONFIG_TMPFS_POSIX_ACL
2483 .setattr = shmem_notify_change,
2484 .setxattr = generic_setxattr,
2485 .getxattr = generic_getxattr,
2486 .listxattr = generic_listxattr,
2487 .removexattr = generic_removexattr,
2488 .check_acl = generic_check_acl,
2492 static const struct super_operations shmem_ops = {
2493 .alloc_inode = shmem_alloc_inode,
2494 .destroy_inode = shmem_destroy_inode,
2496 .statfs = shmem_statfs,
2497 .remount_fs = shmem_remount_fs,
2498 .show_options = shmem_show_options,
2500 .delete_inode = shmem_delete_inode,
2501 .drop_inode = generic_delete_inode,
2502 .put_super = shmem_put_super,
2505 static const struct vm_operations_struct shmem_vm_ops = {
2506 .fault = shmem_fault,
2508 .set_policy = shmem_set_policy,
2509 .get_policy = shmem_get_policy,
2514 static int shmem_get_sb(struct file_system_type *fs_type,
2515 int flags, const char *dev_name, void *data, struct vfsmount *mnt)
2517 return get_sb_nodev(fs_type, flags, data, shmem_fill_super, mnt);
2520 static struct file_system_type tmpfs_fs_type = {
2521 .owner = THIS_MODULE,
2523 .get_sb = shmem_get_sb,
2524 .kill_sb = kill_litter_super,
2527 int __init init_tmpfs(void)
2531 error = bdi_init(&shmem_backing_dev_info);
2535 error = init_inodecache();
2539 error = register_filesystem(&tmpfs_fs_type);
2541 printk(KERN_ERR "Could not register tmpfs\n");
2545 shm_mnt = vfs_kern_mount(&tmpfs_fs_type, MS_NOUSER,
2546 tmpfs_fs_type.name, NULL);
2547 if (IS_ERR(shm_mnt)) {
2548 error = PTR_ERR(shm_mnt);
2549 printk(KERN_ERR "Could not kern_mount tmpfs\n");
2555 unregister_filesystem(&tmpfs_fs_type);
2557 destroy_inodecache();
2559 bdi_destroy(&shmem_backing_dev_info);
2561 shm_mnt = ERR_PTR(error);
2565 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2567 * mem_cgroup_get_shmem_target - find a page or entry assigned to the shmem file
2568 * @inode: the inode to be searched
2569 * @pgoff: the offset to be searched
2570 * @pagep: the pointer for the found page to be stored
2571 * @ent: the pointer for the found swap entry to be stored
2573 * If a page is found, refcount of it is incremented. Callers should handle
2576 void mem_cgroup_get_shmem_target(struct inode *inode, pgoff_t pgoff,
2577 struct page **pagep, swp_entry_t *ent)
2579 swp_entry_t entry = { .val = 0 }, *ptr;
2580 struct page *page = NULL;
2581 struct shmem_inode_info *info = SHMEM_I(inode);
2583 if ((pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
2586 spin_lock(&info->lock);
2587 ptr = shmem_swp_entry(info, pgoff, NULL);
2589 if (ptr && ptr->val) {
2590 entry.val = ptr->val;
2591 page = find_get_page(&swapper_space, entry.val);
2594 page = find_get_page(inode->i_mapping, pgoff);
2596 shmem_swp_unmap(ptr);
2597 spin_unlock(&info->lock);
2604 #else /* !CONFIG_SHMEM */
2607 * tiny-shmem: simple shmemfs and tmpfs using ramfs code
2609 * This is intended for small system where the benefits of the full
2610 * shmem code (swap-backed and resource-limited) are outweighed by
2611 * their complexity. On systems without swap this code should be
2612 * effectively equivalent, but much lighter weight.
2615 #include <linux/ramfs.h>
2617 static struct file_system_type tmpfs_fs_type = {
2619 .get_sb = ramfs_get_sb,
2620 .kill_sb = kill_litter_super,
2623 int __init init_tmpfs(void)
2625 BUG_ON(register_filesystem(&tmpfs_fs_type) != 0);
2627 shm_mnt = kern_mount(&tmpfs_fs_type);
2628 BUG_ON(IS_ERR(shm_mnt));
2633 int shmem_unuse(swp_entry_t entry, struct page *page)
2638 int shmem_lock(struct file *file, int lock, struct user_struct *user)
2643 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2645 * mem_cgroup_get_shmem_target - find a page or entry assigned to the shmem file
2646 * @inode: the inode to be searched
2647 * @pgoff: the offset to be searched
2648 * @pagep: the pointer for the found page to be stored
2649 * @ent: the pointer for the found swap entry to be stored
2651 * If a page is found, refcount of it is incremented. Callers should handle
2654 void mem_cgroup_get_shmem_target(struct inode *inode, pgoff_t pgoff,
2655 struct page **pagep, swp_entry_t *ent)
2657 struct page *page = NULL;
2659 if ((pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
2661 page = find_get_page(inode->i_mapping, pgoff);
2664 *ent = (swp_entry_t){ .val = 0 };
2668 #define shmem_vm_ops generic_file_vm_ops
2669 #define shmem_file_operations ramfs_file_operations
2670 #define shmem_get_inode(sb, dir, mode, dev, flags) ramfs_get_inode(sb, dir, mode, dev)
2671 #define shmem_acct_size(flags, size) 0
2672 #define shmem_unacct_size(flags, size) do {} while (0)
2673 #define SHMEM_MAX_BYTES MAX_LFS_FILESIZE
2675 #endif /* CONFIG_SHMEM */
2680 * shmem_file_setup - get an unlinked file living in tmpfs
2681 * @name: name for dentry (to be seen in /proc/<pid>/maps
2682 * @size: size to be set for the file
2683 * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
2685 struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
2689 struct inode *inode;
2691 struct dentry *root;
2694 if (IS_ERR(shm_mnt))
2695 return (void *)shm_mnt;
2697 if (size < 0 || size > SHMEM_MAX_BYTES)
2698 return ERR_PTR(-EINVAL);
2700 if (shmem_acct_size(flags, size))
2701 return ERR_PTR(-ENOMEM);
2705 this.len = strlen(name);
2706 this.hash = 0; /* will go */
2707 root = shm_mnt->mnt_root;
2708 path.dentry = d_alloc(root, &this);
2711 path.mnt = mntget(shm_mnt);
2714 inode = shmem_get_inode(root->d_sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
2718 d_instantiate(path.dentry, inode);
2719 inode->i_size = size;
2720 inode->i_nlink = 0; /* It is unlinked */
2722 error = ramfs_nommu_expand_for_mapping(inode, size);
2728 file = alloc_file(&path, FMODE_WRITE | FMODE_READ,
2729 &shmem_file_operations);
2738 shmem_unacct_size(flags, size);
2739 return ERR_PTR(error);
2741 EXPORT_SYMBOL_GPL(shmem_file_setup);
2744 * shmem_zero_setup - setup a shared anonymous mapping
2745 * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2747 int shmem_zero_setup(struct vm_area_struct *vma)
2750 loff_t size = vma->vm_end - vma->vm_start;
2752 file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2754 return PTR_ERR(file);
2758 vma->vm_file = file;
2759 vma->vm_ops = &shmem_vm_ops;