2 * Resizable virtual memory filesystem for Linux.
4 * Copyright (C) 2000 Linus Torvalds.
6 * 2000-2001 Christoph Rohland
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
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>
19 * Copyright (c) 2004, 2008 Matt Mackall <mpm@selenic.com>
21 * This file is released under the GPL.
25 #include <linux/init.h>
26 #include <linux/vfs.h>
27 #include <linux/mount.h>
28 #include <linux/ramfs.h>
29 #include <linux/pagemap.h>
30 #include <linux/file.h>
32 #include <linux/export.h>
33 #include <linux/swap.h>
34 #include <linux/uio.h>
36 static struct vfsmount *shm_mnt;
40 * This virtual memory filesystem is heavily based on the ramfs. It
41 * extends ramfs by the ability to use swap and honor resource limits
42 * which makes it a completely usable filesystem.
45 #include <linux/xattr.h>
46 #include <linux/exportfs.h>
47 #include <linux/posix_acl.h>
48 #include <linux/posix_acl_xattr.h>
49 #include <linux/mman.h>
50 #include <linux/string.h>
51 #include <linux/slab.h>
52 #include <linux/backing-dev.h>
53 #include <linux/shmem_fs.h>
54 #include <linux/writeback.h>
55 #include <linux/blkdev.h>
56 #include <linux/pagevec.h>
57 #include <linux/percpu_counter.h>
58 #include <linux/falloc.h>
59 #include <linux/splice.h>
60 #include <linux/security.h>
61 #include <linux/swapops.h>
62 #include <linux/mempolicy.h>
63 #include <linux/namei.h>
64 #include <linux/ctype.h>
65 #include <linux/migrate.h>
66 #include <linux/highmem.h>
67 #include <linux/seq_file.h>
68 #include <linux/magic.h>
69 #include <linux/syscalls.h>
70 #include <linux/fcntl.h>
71 #include <uapi/linux/memfd.h>
73 #include <asm/uaccess.h>
74 #include <asm/pgtable.h>
76 #define BLOCKS_PER_PAGE (PAGE_CACHE_SIZE/512)
77 #define VM_ACCT(size) (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
79 /* Pretend that each entry is of this size in directory's i_size */
80 #define BOGO_DIRENT_SIZE 20
82 /* Symlink up to this size is kmalloc'ed instead of using a swappable page */
83 #define SHORT_SYMLINK_LEN 128
86 * shmem_fallocate communicates with shmem_fault or shmem_writepage via
87 * inode->i_private (with i_mutex making sure that it has only one user at
88 * a time): we would prefer not to enlarge the shmem inode just for that.
91 wait_queue_head_t *waitq; /* faults into hole wait for punch to end */
92 pgoff_t start; /* start of range currently being fallocated */
93 pgoff_t next; /* the next page offset to be fallocated */
94 pgoff_t nr_falloced; /* how many new pages have been fallocated */
95 pgoff_t nr_unswapped; /* how often writepage refused to swap out */
98 /* Flag allocation requirements to shmem_getpage */
100 SGP_READ, /* don't exceed i_size, don't allocate page */
101 SGP_CACHE, /* don't exceed i_size, may allocate page */
102 SGP_DIRTY, /* like SGP_CACHE, but set new page dirty */
103 SGP_WRITE, /* may exceed i_size, may allocate !Uptodate page */
104 SGP_FALLOC, /* like SGP_WRITE, but make existing page Uptodate */
108 static unsigned long shmem_default_max_blocks(void)
110 return totalram_pages / 2;
113 static unsigned long shmem_default_max_inodes(void)
115 return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
119 static bool shmem_should_replace_page(struct page *page, gfp_t gfp);
120 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
121 struct shmem_inode_info *info, pgoff_t index);
122 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
123 struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type);
125 static inline int shmem_getpage(struct inode *inode, pgoff_t index,
126 struct page **pagep, enum sgp_type sgp, int *fault_type)
128 return shmem_getpage_gfp(inode, index, pagep, sgp,
129 mapping_gfp_mask(inode->i_mapping), fault_type);
132 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
134 return sb->s_fs_info;
138 * shmem_file_setup pre-accounts the whole fixed size of a VM object,
139 * for shared memory and for shared anonymous (/dev/zero) mappings
140 * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
141 * consistent with the pre-accounting of private mappings ...
143 static inline int shmem_acct_size(unsigned long flags, loff_t size)
145 return (flags & VM_NORESERVE) ?
146 0 : security_vm_enough_memory_mm(current->mm, VM_ACCT(size));
149 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
151 if (!(flags & VM_NORESERVE))
152 vm_unacct_memory(VM_ACCT(size));
155 static inline int shmem_reacct_size(unsigned long flags,
156 loff_t oldsize, loff_t newsize)
158 if (!(flags & VM_NORESERVE)) {
159 if (VM_ACCT(newsize) > VM_ACCT(oldsize))
160 return security_vm_enough_memory_mm(current->mm,
161 VM_ACCT(newsize) - VM_ACCT(oldsize));
162 else if (VM_ACCT(newsize) < VM_ACCT(oldsize))
163 vm_unacct_memory(VM_ACCT(oldsize) - VM_ACCT(newsize));
169 * ... whereas tmpfs objects are accounted incrementally as
170 * pages are allocated, in order to allow huge sparse files.
171 * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
172 * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
174 static inline int shmem_acct_block(unsigned long flags)
176 return (flags & VM_NORESERVE) ?
177 security_vm_enough_memory_mm(current->mm, VM_ACCT(PAGE_CACHE_SIZE)) : 0;
180 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
182 if (flags & VM_NORESERVE)
183 vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
186 static const struct super_operations shmem_ops;
187 static const struct address_space_operations shmem_aops;
188 static const struct file_operations shmem_file_operations;
189 static const struct inode_operations shmem_inode_operations;
190 static const struct inode_operations shmem_dir_inode_operations;
191 static const struct inode_operations shmem_special_inode_operations;
192 static const struct vm_operations_struct shmem_vm_ops;
194 static LIST_HEAD(shmem_swaplist);
195 static DEFINE_MUTEX(shmem_swaplist_mutex);
197 static int shmem_reserve_inode(struct super_block *sb)
199 struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
200 if (sbinfo->max_inodes) {
201 spin_lock(&sbinfo->stat_lock);
202 if (!sbinfo->free_inodes) {
203 spin_unlock(&sbinfo->stat_lock);
206 sbinfo->free_inodes--;
207 spin_unlock(&sbinfo->stat_lock);
212 static void shmem_free_inode(struct super_block *sb)
214 struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
215 if (sbinfo->max_inodes) {
216 spin_lock(&sbinfo->stat_lock);
217 sbinfo->free_inodes++;
218 spin_unlock(&sbinfo->stat_lock);
223 * shmem_recalc_inode - recalculate the block usage of an inode
224 * @inode: inode to recalc
226 * We have to calculate the free blocks since the mm can drop
227 * undirtied hole pages behind our back.
229 * But normally info->alloced == inode->i_mapping->nrpages + info->swapped
230 * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
232 * It has to be called with the spinlock held.
234 static void shmem_recalc_inode(struct inode *inode)
236 struct shmem_inode_info *info = SHMEM_I(inode);
239 freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
241 struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
242 if (sbinfo->max_blocks)
243 percpu_counter_add(&sbinfo->used_blocks, -freed);
244 info->alloced -= freed;
245 inode->i_blocks -= freed * BLOCKS_PER_PAGE;
246 shmem_unacct_blocks(info->flags, freed);
251 * Replace item expected in radix tree by a new item, while holding tree lock.
253 static int shmem_radix_tree_replace(struct address_space *mapping,
254 pgoff_t index, void *expected, void *replacement)
259 VM_BUG_ON(!expected);
260 VM_BUG_ON(!replacement);
261 pslot = radix_tree_lookup_slot(&mapping->page_tree, index);
264 item = radix_tree_deref_slot_protected(pslot, &mapping->tree_lock);
265 if (item != expected)
267 radix_tree_replace_slot(pslot, replacement);
272 * Sometimes, before we decide whether to proceed or to fail, we must check
273 * that an entry was not already brought back from swap by a racing thread.
275 * Checking page is not enough: by the time a SwapCache page is locked, it
276 * might be reused, and again be SwapCache, using the same swap as before.
278 static bool shmem_confirm_swap(struct address_space *mapping,
279 pgoff_t index, swp_entry_t swap)
284 item = radix_tree_lookup(&mapping->page_tree, index);
286 return item == swp_to_radix_entry(swap);
290 * Like add_to_page_cache_locked, but error if expected item has gone.
292 static int shmem_add_to_page_cache(struct page *page,
293 struct address_space *mapping,
294 pgoff_t index, void *expected)
298 VM_BUG_ON_PAGE(!PageLocked(page), page);
299 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
301 page_cache_get(page);
302 page->mapping = mapping;
305 spin_lock_irq(&mapping->tree_lock);
307 error = radix_tree_insert(&mapping->page_tree, index, page);
309 error = shmem_radix_tree_replace(mapping, index, expected,
313 __inc_zone_page_state(page, NR_FILE_PAGES);
314 __inc_zone_page_state(page, NR_SHMEM);
315 spin_unlock_irq(&mapping->tree_lock);
317 page->mapping = NULL;
318 spin_unlock_irq(&mapping->tree_lock);
319 page_cache_release(page);
325 * Like delete_from_page_cache, but substitutes swap for page.
327 static void shmem_delete_from_page_cache(struct page *page, void *radswap)
329 struct address_space *mapping = page->mapping;
332 spin_lock_irq(&mapping->tree_lock);
333 error = shmem_radix_tree_replace(mapping, page->index, page, radswap);
334 page->mapping = NULL;
336 __dec_zone_page_state(page, NR_FILE_PAGES);
337 __dec_zone_page_state(page, NR_SHMEM);
338 spin_unlock_irq(&mapping->tree_lock);
339 page_cache_release(page);
344 * Remove swap entry from radix tree, free the swap and its page cache.
346 static int shmem_free_swap(struct address_space *mapping,
347 pgoff_t index, void *radswap)
351 spin_lock_irq(&mapping->tree_lock);
352 old = radix_tree_delete_item(&mapping->page_tree, index, radswap);
353 spin_unlock_irq(&mapping->tree_lock);
356 free_swap_and_cache(radix_to_swp_entry(radswap));
361 * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists.
363 void shmem_unlock_mapping(struct address_space *mapping)
366 pgoff_t indices[PAGEVEC_SIZE];
369 pagevec_init(&pvec, 0);
371 * Minor point, but we might as well stop if someone else SHM_LOCKs it.
373 while (!mapping_unevictable(mapping)) {
375 * Avoid pagevec_lookup(): find_get_pages() returns 0 as if it
376 * has finished, if it hits a row of PAGEVEC_SIZE swap entries.
378 pvec.nr = find_get_entries(mapping, index,
379 PAGEVEC_SIZE, pvec.pages, indices);
382 index = indices[pvec.nr - 1] + 1;
383 pagevec_remove_exceptionals(&pvec);
384 check_move_unevictable_pages(pvec.pages, pvec.nr);
385 pagevec_release(&pvec);
391 * Remove range of pages and swap entries from radix tree, and free them.
392 * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.
394 static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
397 struct address_space *mapping = inode->i_mapping;
398 struct shmem_inode_info *info = SHMEM_I(inode);
399 pgoff_t start = (lstart + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
400 pgoff_t end = (lend + 1) >> PAGE_CACHE_SHIFT;
401 unsigned int partial_start = lstart & (PAGE_CACHE_SIZE - 1);
402 unsigned int partial_end = (lend + 1) & (PAGE_CACHE_SIZE - 1);
404 pgoff_t indices[PAGEVEC_SIZE];
405 long nr_swaps_freed = 0;
410 end = -1; /* unsigned, so actually very big */
412 pagevec_init(&pvec, 0);
414 while (index < end) {
415 pvec.nr = find_get_entries(mapping, index,
416 min(end - index, (pgoff_t)PAGEVEC_SIZE),
417 pvec.pages, indices);
420 for (i = 0; i < pagevec_count(&pvec); i++) {
421 struct page *page = pvec.pages[i];
427 if (radix_tree_exceptional_entry(page)) {
430 nr_swaps_freed += !shmem_free_swap(mapping,
435 if (!trylock_page(page))
437 if (!unfalloc || !PageUptodate(page)) {
438 if (page->mapping == mapping) {
439 VM_BUG_ON_PAGE(PageWriteback(page), page);
440 truncate_inode_page(mapping, page);
445 pagevec_remove_exceptionals(&pvec);
446 pagevec_release(&pvec);
452 struct page *page = NULL;
453 shmem_getpage(inode, start - 1, &page, SGP_READ, NULL);
455 unsigned int top = PAGE_CACHE_SIZE;
460 zero_user_segment(page, partial_start, top);
461 set_page_dirty(page);
463 page_cache_release(page);
467 struct page *page = NULL;
468 shmem_getpage(inode, end, &page, SGP_READ, NULL);
470 zero_user_segment(page, 0, partial_end);
471 set_page_dirty(page);
473 page_cache_release(page);
480 while (index < end) {
483 pvec.nr = find_get_entries(mapping, index,
484 min(end - index, (pgoff_t)PAGEVEC_SIZE),
485 pvec.pages, indices);
487 /* If all gone or hole-punch or unfalloc, we're done */
488 if (index == start || end != -1)
490 /* But if truncating, restart to make sure all gone */
494 for (i = 0; i < pagevec_count(&pvec); i++) {
495 struct page *page = pvec.pages[i];
501 if (radix_tree_exceptional_entry(page)) {
504 if (shmem_free_swap(mapping, index, page)) {
505 /* Swap was replaced by page: retry */
514 if (!unfalloc || !PageUptodate(page)) {
515 if (page->mapping == mapping) {
516 VM_BUG_ON_PAGE(PageWriteback(page), page);
517 truncate_inode_page(mapping, page);
519 /* Page was replaced by swap: retry */
527 pagevec_remove_exceptionals(&pvec);
528 pagevec_release(&pvec);
532 spin_lock(&info->lock);
533 info->swapped -= nr_swaps_freed;
534 shmem_recalc_inode(inode);
535 spin_unlock(&info->lock);
538 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
540 shmem_undo_range(inode, lstart, lend, false);
541 inode->i_ctime = inode->i_mtime = CURRENT_TIME;
543 EXPORT_SYMBOL_GPL(shmem_truncate_range);
545 static int shmem_getattr(struct vfsmount *mnt, struct dentry *dentry,
548 struct inode *inode = dentry->d_inode;
549 struct shmem_inode_info *info = SHMEM_I(inode);
551 if (info->alloced - info->swapped != inode->i_mapping->nrpages) {
552 spin_lock(&info->lock);
553 shmem_recalc_inode(inode);
554 spin_unlock(&info->lock);
556 generic_fillattr(inode, stat);
560 static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
562 struct inode *inode = d_inode(dentry);
563 struct shmem_inode_info *info = SHMEM_I(inode);
566 error = inode_change_ok(inode, attr);
570 if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
571 loff_t oldsize = inode->i_size;
572 loff_t newsize = attr->ia_size;
574 /* protected by i_mutex */
575 if ((newsize < oldsize && (info->seals & F_SEAL_SHRINK)) ||
576 (newsize > oldsize && (info->seals & F_SEAL_GROW)))
579 if (newsize != oldsize) {
580 error = shmem_reacct_size(SHMEM_I(inode)->flags,
584 i_size_write(inode, newsize);
585 inode->i_ctime = inode->i_mtime = CURRENT_TIME;
587 if (newsize <= oldsize) {
588 loff_t holebegin = round_up(newsize, PAGE_SIZE);
589 if (oldsize > holebegin)
590 unmap_mapping_range(inode->i_mapping,
593 shmem_truncate_range(inode,
594 newsize, (loff_t)-1);
595 /* unmap again to remove racily COWed private pages */
596 if (oldsize > holebegin)
597 unmap_mapping_range(inode->i_mapping,
602 setattr_copy(inode, attr);
603 if (attr->ia_valid & ATTR_MODE)
604 error = posix_acl_chmod(inode, inode->i_mode);
608 static void shmem_evict_inode(struct inode *inode)
610 struct shmem_inode_info *info = SHMEM_I(inode);
612 if (inode->i_mapping->a_ops == &shmem_aops) {
613 shmem_unacct_size(info->flags, inode->i_size);
615 shmem_truncate_range(inode, 0, (loff_t)-1);
616 if (!list_empty(&info->swaplist)) {
617 mutex_lock(&shmem_swaplist_mutex);
618 list_del_init(&info->swaplist);
619 mutex_unlock(&shmem_swaplist_mutex);
622 kfree(info->symlink);
624 simple_xattrs_free(&info->xattrs);
625 WARN_ON(inode->i_blocks);
626 shmem_free_inode(inode->i_sb);
631 * If swap found in inode, free it and move page from swapcache to filecache.
633 static int shmem_unuse_inode(struct shmem_inode_info *info,
634 swp_entry_t swap, struct page **pagep)
636 struct address_space *mapping = info->vfs_inode.i_mapping;
642 radswap = swp_to_radix_entry(swap);
643 index = radix_tree_locate_item(&mapping->page_tree, radswap);
645 return -EAGAIN; /* tell shmem_unuse we found nothing */
648 * Move _head_ to start search for next from here.
649 * But be careful: shmem_evict_inode checks list_empty without taking
650 * mutex, and there's an instant in list_move_tail when info->swaplist
651 * would appear empty, if it were the only one on shmem_swaplist.
653 if (shmem_swaplist.next != &info->swaplist)
654 list_move_tail(&shmem_swaplist, &info->swaplist);
656 gfp = mapping_gfp_mask(mapping);
657 if (shmem_should_replace_page(*pagep, gfp)) {
658 mutex_unlock(&shmem_swaplist_mutex);
659 error = shmem_replace_page(pagep, gfp, info, index);
660 mutex_lock(&shmem_swaplist_mutex);
662 * We needed to drop mutex to make that restrictive page
663 * allocation, but the inode might have been freed while we
664 * dropped it: although a racing shmem_evict_inode() cannot
665 * complete without emptying the radix_tree, our page lock
666 * on this swapcache page is not enough to prevent that -
667 * free_swap_and_cache() of our swap entry will only
668 * trylock_page(), removing swap from radix_tree whatever.
670 * We must not proceed to shmem_add_to_page_cache() if the
671 * inode has been freed, but of course we cannot rely on
672 * inode or mapping or info to check that. However, we can
673 * safely check if our swap entry is still in use (and here
674 * it can't have got reused for another page): if it's still
675 * in use, then the inode cannot have been freed yet, and we
676 * can safely proceed (if it's no longer in use, that tells
677 * nothing about the inode, but we don't need to unuse swap).
679 if (!page_swapcount(*pagep))
684 * We rely on shmem_swaplist_mutex, not only to protect the swaplist,
685 * but also to hold up shmem_evict_inode(): so inode cannot be freed
686 * beneath us (pagelock doesn't help until the page is in pagecache).
689 error = shmem_add_to_page_cache(*pagep, mapping, index,
691 if (error != -ENOMEM) {
693 * Truncation and eviction use free_swap_and_cache(), which
694 * only does trylock page: if we raced, best clean up here.
696 delete_from_swap_cache(*pagep);
697 set_page_dirty(*pagep);
699 spin_lock(&info->lock);
701 spin_unlock(&info->lock);
709 * Search through swapped inodes to find and replace swap by page.
711 int shmem_unuse(swp_entry_t swap, struct page *page)
713 struct list_head *this, *next;
714 struct shmem_inode_info *info;
715 struct mem_cgroup *memcg;
719 * There's a faint possibility that swap page was replaced before
720 * caller locked it: caller will come back later with the right page.
722 if (unlikely(!PageSwapCache(page) || page_private(page) != swap.val))
726 * Charge page using GFP_KERNEL while we can wait, before taking
727 * the shmem_swaplist_mutex which might hold up shmem_writepage().
728 * Charged back to the user (not to caller) when swap account is used.
730 error = mem_cgroup_try_charge(page, current->mm, GFP_KERNEL, &memcg);
733 /* No radix_tree_preload: swap entry keeps a place for page in tree */
736 mutex_lock(&shmem_swaplist_mutex);
737 list_for_each_safe(this, next, &shmem_swaplist) {
738 info = list_entry(this, struct shmem_inode_info, swaplist);
740 error = shmem_unuse_inode(info, swap, &page);
742 list_del_init(&info->swaplist);
744 if (error != -EAGAIN)
746 /* found nothing in this: move on to search the next */
748 mutex_unlock(&shmem_swaplist_mutex);
751 if (error != -ENOMEM)
753 mem_cgroup_cancel_charge(page, memcg);
755 mem_cgroup_commit_charge(page, memcg, true);
758 page_cache_release(page);
763 * Move the page from the page cache to the swap cache.
765 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
767 struct shmem_inode_info *info;
768 struct address_space *mapping;
773 BUG_ON(!PageLocked(page));
774 mapping = page->mapping;
776 inode = mapping->host;
777 info = SHMEM_I(inode);
778 if (info->flags & VM_LOCKED)
780 if (!total_swap_pages)
784 * Our capabilities prevent regular writeback or sync from ever calling
785 * shmem_writepage; but a stacking filesystem might use ->writepage of
786 * its underlying filesystem, in which case tmpfs should write out to
787 * swap only in response to memory pressure, and not for the writeback
790 if (!wbc->for_reclaim) {
791 WARN_ON_ONCE(1); /* Still happens? Tell us about it! */
796 * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC
797 * value into swapfile.c, the only way we can correctly account for a
798 * fallocated page arriving here is now to initialize it and write it.
800 * That's okay for a page already fallocated earlier, but if we have
801 * not yet completed the fallocation, then (a) we want to keep track
802 * of this page in case we have to undo it, and (b) it may not be a
803 * good idea to continue anyway, once we're pushing into swap. So
804 * reactivate the page, and let shmem_fallocate() quit when too many.
806 if (!PageUptodate(page)) {
807 if (inode->i_private) {
808 struct shmem_falloc *shmem_falloc;
809 spin_lock(&inode->i_lock);
810 shmem_falloc = inode->i_private;
812 !shmem_falloc->waitq &&
813 index >= shmem_falloc->start &&
814 index < shmem_falloc->next)
815 shmem_falloc->nr_unswapped++;
818 spin_unlock(&inode->i_lock);
822 clear_highpage(page);
823 flush_dcache_page(page);
824 SetPageUptodate(page);
827 swap = get_swap_page();
832 * Add inode to shmem_unuse()'s list of swapped-out inodes,
833 * if it's not already there. Do it now before the page is
834 * moved to swap cache, when its pagelock no longer protects
835 * the inode from eviction. But don't unlock the mutex until
836 * we've incremented swapped, because shmem_unuse_inode() will
837 * prune a !swapped inode from the swaplist under this mutex.
839 mutex_lock(&shmem_swaplist_mutex);
840 if (list_empty(&info->swaplist))
841 list_add_tail(&info->swaplist, &shmem_swaplist);
843 if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
844 swap_shmem_alloc(swap);
845 shmem_delete_from_page_cache(page, swp_to_radix_entry(swap));
847 spin_lock(&info->lock);
849 shmem_recalc_inode(inode);
850 spin_unlock(&info->lock);
852 mutex_unlock(&shmem_swaplist_mutex);
853 BUG_ON(page_mapped(page));
854 swap_writepage(page, wbc);
858 mutex_unlock(&shmem_swaplist_mutex);
859 swapcache_free(swap);
861 set_page_dirty(page);
862 if (wbc->for_reclaim)
863 return AOP_WRITEPAGE_ACTIVATE; /* Return with page locked */
870 static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
874 if (!mpol || mpol->mode == MPOL_DEFAULT)
875 return; /* show nothing */
877 mpol_to_str(buffer, sizeof(buffer), mpol);
879 seq_printf(seq, ",mpol=%s", buffer);
882 static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
884 struct mempolicy *mpol = NULL;
886 spin_lock(&sbinfo->stat_lock); /* prevent replace/use races */
889 spin_unlock(&sbinfo->stat_lock);
893 #endif /* CONFIG_TMPFS */
895 static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
896 struct shmem_inode_info *info, pgoff_t index)
898 struct vm_area_struct pvma;
901 /* Create a pseudo vma that just contains the policy */
903 /* Bias interleave by inode number to distribute better across nodes */
904 pvma.vm_pgoff = index + info->vfs_inode.i_ino;
906 pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
908 page = swapin_readahead(swap, gfp, &pvma, 0);
910 /* Drop reference taken by mpol_shared_policy_lookup() */
911 mpol_cond_put(pvma.vm_policy);
916 static struct page *shmem_alloc_page(gfp_t gfp,
917 struct shmem_inode_info *info, pgoff_t index)
919 struct vm_area_struct pvma;
922 /* Create a pseudo vma that just contains the policy */
924 /* Bias interleave by inode number to distribute better across nodes */
925 pvma.vm_pgoff = index + info->vfs_inode.i_ino;
927 pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
929 page = alloc_page_vma(gfp, &pvma, 0);
931 /* Drop reference taken by mpol_shared_policy_lookup() */
932 mpol_cond_put(pvma.vm_policy);
936 #else /* !CONFIG_NUMA */
938 static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
941 #endif /* CONFIG_TMPFS */
943 static inline struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
944 struct shmem_inode_info *info, pgoff_t index)
946 return swapin_readahead(swap, gfp, NULL, 0);
949 static inline struct page *shmem_alloc_page(gfp_t gfp,
950 struct shmem_inode_info *info, pgoff_t index)
952 return alloc_page(gfp);
954 #endif /* CONFIG_NUMA */
956 #if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS)
957 static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
964 * When a page is moved from swapcache to shmem filecache (either by the
965 * usual swapin of shmem_getpage_gfp(), or by the less common swapoff of
966 * shmem_unuse_inode()), it may have been read in earlier from swap, in
967 * ignorance of the mapping it belongs to. If that mapping has special
968 * constraints (like the gma500 GEM driver, which requires RAM below 4GB),
969 * we may need to copy to a suitable page before moving to filecache.
971 * In a future release, this may well be extended to respect cpuset and
972 * NUMA mempolicy, and applied also to anonymous pages in do_swap_page();
973 * but for now it is a simple matter of zone.
975 static bool shmem_should_replace_page(struct page *page, gfp_t gfp)
977 return page_zonenum(page) > gfp_zone(gfp);
980 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
981 struct shmem_inode_info *info, pgoff_t index)
983 struct page *oldpage, *newpage;
984 struct address_space *swap_mapping;
989 swap_index = page_private(oldpage);
990 swap_mapping = page_mapping(oldpage);
993 * We have arrived here because our zones are constrained, so don't
994 * limit chance of success by further cpuset and node constraints.
996 gfp &= ~GFP_CONSTRAINT_MASK;
997 newpage = shmem_alloc_page(gfp, info, index);
1001 page_cache_get(newpage);
1002 copy_highpage(newpage, oldpage);
1003 flush_dcache_page(newpage);
1005 __set_page_locked(newpage);
1006 SetPageUptodate(newpage);
1007 SetPageSwapBacked(newpage);
1008 set_page_private(newpage, swap_index);
1009 SetPageSwapCache(newpage);
1012 * Our caller will very soon move newpage out of swapcache, but it's
1013 * a nice clean interface for us to replace oldpage by newpage there.
1015 spin_lock_irq(&swap_mapping->tree_lock);
1016 error = shmem_radix_tree_replace(swap_mapping, swap_index, oldpage,
1019 __inc_zone_page_state(newpage, NR_FILE_PAGES);
1020 __dec_zone_page_state(oldpage, NR_FILE_PAGES);
1022 spin_unlock_irq(&swap_mapping->tree_lock);
1024 if (unlikely(error)) {
1026 * Is this possible? I think not, now that our callers check
1027 * both PageSwapCache and page_private after getting page lock;
1028 * but be defensive. Reverse old to newpage for clear and free.
1032 mem_cgroup_replace_page(oldpage, newpage);
1033 lru_cache_add_anon(newpage);
1037 ClearPageSwapCache(oldpage);
1038 set_page_private(oldpage, 0);
1040 unlock_page(oldpage);
1041 page_cache_release(oldpage);
1042 page_cache_release(oldpage);
1047 * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
1049 * If we allocate a new one we do not mark it dirty. That's up to the
1050 * vm. If we swap it in we mark it dirty since we also free the swap
1051 * entry since a page cannot live in both the swap and page cache
1053 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
1054 struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type)
1056 struct address_space *mapping = inode->i_mapping;
1057 struct shmem_inode_info *info;
1058 struct shmem_sb_info *sbinfo;
1059 struct mem_cgroup *memcg;
1066 if (index > (MAX_LFS_FILESIZE >> PAGE_CACHE_SHIFT))
1070 page = find_lock_entry(mapping, index);
1071 if (radix_tree_exceptional_entry(page)) {
1072 swap = radix_to_swp_entry(page);
1076 if (sgp != SGP_WRITE && sgp != SGP_FALLOC &&
1077 ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
1082 if (page && sgp == SGP_WRITE)
1083 mark_page_accessed(page);
1085 /* fallocated page? */
1086 if (page && !PageUptodate(page)) {
1087 if (sgp != SGP_READ)
1090 page_cache_release(page);
1093 if (page || (sgp == SGP_READ && !swap.val)) {
1099 * Fast cache lookup did not find it:
1100 * bring it back from swap or allocate.
1102 info = SHMEM_I(inode);
1103 sbinfo = SHMEM_SB(inode->i_sb);
1106 /* Look it up and read it in.. */
1107 page = lookup_swap_cache(swap);
1109 /* here we actually do the io */
1111 *fault_type |= VM_FAULT_MAJOR;
1112 page = shmem_swapin(swap, gfp, info, index);
1119 /* We have to do this with page locked to prevent races */
1121 if (!PageSwapCache(page) || page_private(page) != swap.val ||
1122 !shmem_confirm_swap(mapping, index, swap)) {
1123 error = -EEXIST; /* try again */
1126 if (!PageUptodate(page)) {
1130 wait_on_page_writeback(page);
1132 if (shmem_should_replace_page(page, gfp)) {
1133 error = shmem_replace_page(&page, gfp, info, index);
1138 error = mem_cgroup_try_charge(page, current->mm, gfp, &memcg);
1140 error = shmem_add_to_page_cache(page, mapping, index,
1141 swp_to_radix_entry(swap));
1143 * We already confirmed swap under page lock, and make
1144 * no memory allocation here, so usually no possibility
1145 * of error; but free_swap_and_cache() only trylocks a
1146 * page, so it is just possible that the entry has been
1147 * truncated or holepunched since swap was confirmed.
1148 * shmem_undo_range() will have done some of the
1149 * unaccounting, now delete_from_swap_cache() will do
1151 * Reset swap.val? No, leave it so "failed" goes back to
1152 * "repeat": reading a hole and writing should succeed.
1155 mem_cgroup_cancel_charge(page, memcg);
1156 delete_from_swap_cache(page);
1162 mem_cgroup_commit_charge(page, memcg, true);
1164 spin_lock(&info->lock);
1166 shmem_recalc_inode(inode);
1167 spin_unlock(&info->lock);
1169 if (sgp == SGP_WRITE)
1170 mark_page_accessed(page);
1172 delete_from_swap_cache(page);
1173 set_page_dirty(page);
1177 if (shmem_acct_block(info->flags)) {
1181 if (sbinfo->max_blocks) {
1182 if (percpu_counter_compare(&sbinfo->used_blocks,
1183 sbinfo->max_blocks) >= 0) {
1187 percpu_counter_inc(&sbinfo->used_blocks);
1190 page = shmem_alloc_page(gfp, info, index);
1196 __SetPageSwapBacked(page);
1197 __set_page_locked(page);
1198 if (sgp == SGP_WRITE)
1199 __SetPageReferenced(page);
1201 error = mem_cgroup_try_charge(page, current->mm, gfp, &memcg);
1204 error = radix_tree_maybe_preload(gfp & GFP_RECLAIM_MASK);
1206 error = shmem_add_to_page_cache(page, mapping, index,
1208 radix_tree_preload_end();
1211 mem_cgroup_cancel_charge(page, memcg);
1214 mem_cgroup_commit_charge(page, memcg, false);
1215 lru_cache_add_anon(page);
1217 spin_lock(&info->lock);
1219 inode->i_blocks += BLOCKS_PER_PAGE;
1220 shmem_recalc_inode(inode);
1221 spin_unlock(&info->lock);
1225 * Let SGP_FALLOC use the SGP_WRITE optimization on a new page.
1227 if (sgp == SGP_FALLOC)
1231 * Let SGP_WRITE caller clear ends if write does not fill page;
1232 * but SGP_FALLOC on a page fallocated earlier must initialize
1233 * it now, lest undo on failure cancel our earlier guarantee.
1235 if (sgp != SGP_WRITE) {
1236 clear_highpage(page);
1237 flush_dcache_page(page);
1238 SetPageUptodate(page);
1240 if (sgp == SGP_DIRTY)
1241 set_page_dirty(page);
1244 /* Perhaps the file has been truncated since we checked */
1245 if (sgp != SGP_WRITE && sgp != SGP_FALLOC &&
1246 ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
1260 info = SHMEM_I(inode);
1261 ClearPageDirty(page);
1262 delete_from_page_cache(page);
1263 spin_lock(&info->lock);
1265 inode->i_blocks -= BLOCKS_PER_PAGE;
1266 spin_unlock(&info->lock);
1268 sbinfo = SHMEM_SB(inode->i_sb);
1269 if (sbinfo->max_blocks)
1270 percpu_counter_add(&sbinfo->used_blocks, -1);
1272 shmem_unacct_blocks(info->flags, 1);
1274 if (swap.val && error != -EINVAL &&
1275 !shmem_confirm_swap(mapping, index, swap))
1280 page_cache_release(page);
1282 if (error == -ENOSPC && !once++) {
1283 info = SHMEM_I(inode);
1284 spin_lock(&info->lock);
1285 shmem_recalc_inode(inode);
1286 spin_unlock(&info->lock);
1289 if (error == -EEXIST) /* from above or from radix_tree_insert */
1294 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1296 struct inode *inode = file_inode(vma->vm_file);
1298 int ret = VM_FAULT_LOCKED;
1301 * Trinity finds that probing a hole which tmpfs is punching can
1302 * prevent the hole-punch from ever completing: which in turn
1303 * locks writers out with its hold on i_mutex. So refrain from
1304 * faulting pages into the hole while it's being punched. Although
1305 * shmem_undo_range() does remove the additions, it may be unable to
1306 * keep up, as each new page needs its own unmap_mapping_range() call,
1307 * and the i_mmap tree grows ever slower to scan if new vmas are added.
1309 * It does not matter if we sometimes reach this check just before the
1310 * hole-punch begins, so that one fault then races with the punch:
1311 * we just need to make racing faults a rare case.
1313 * The implementation below would be much simpler if we just used a
1314 * standard mutex or completion: but we cannot take i_mutex in fault,
1315 * and bloating every shmem inode for this unlikely case would be sad.
1317 if (unlikely(inode->i_private)) {
1318 struct shmem_falloc *shmem_falloc;
1320 spin_lock(&inode->i_lock);
1321 shmem_falloc = inode->i_private;
1323 shmem_falloc->waitq &&
1324 vmf->pgoff >= shmem_falloc->start &&
1325 vmf->pgoff < shmem_falloc->next) {
1326 wait_queue_head_t *shmem_falloc_waitq;
1327 DEFINE_WAIT(shmem_fault_wait);
1329 ret = VM_FAULT_NOPAGE;
1330 if ((vmf->flags & FAULT_FLAG_ALLOW_RETRY) &&
1331 !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT)) {
1332 /* It's polite to up mmap_sem if we can */
1333 up_read(&vma->vm_mm->mmap_sem);
1334 ret = VM_FAULT_RETRY;
1337 shmem_falloc_waitq = shmem_falloc->waitq;
1338 prepare_to_wait(shmem_falloc_waitq, &shmem_fault_wait,
1339 TASK_UNINTERRUPTIBLE);
1340 spin_unlock(&inode->i_lock);
1344 * shmem_falloc_waitq points into the shmem_fallocate()
1345 * stack of the hole-punching task: shmem_falloc_waitq
1346 * is usually invalid by the time we reach here, but
1347 * finish_wait() does not dereference it in that case;
1348 * though i_lock needed lest racing with wake_up_all().
1350 spin_lock(&inode->i_lock);
1351 finish_wait(shmem_falloc_waitq, &shmem_fault_wait);
1352 spin_unlock(&inode->i_lock);
1355 spin_unlock(&inode->i_lock);
1358 error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
1360 return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1362 if (ret & VM_FAULT_MAJOR) {
1363 count_vm_event(PGMAJFAULT);
1364 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1370 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol)
1372 struct inode *inode = file_inode(vma->vm_file);
1373 return mpol_set_shared_policy(&SHMEM_I(inode)->policy, vma, mpol);
1376 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
1379 struct inode *inode = file_inode(vma->vm_file);
1382 index = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1383 return mpol_shared_policy_lookup(&SHMEM_I(inode)->policy, index);
1387 int shmem_lock(struct file *file, int lock, struct user_struct *user)
1389 struct inode *inode = file_inode(file);
1390 struct shmem_inode_info *info = SHMEM_I(inode);
1391 int retval = -ENOMEM;
1393 spin_lock(&info->lock);
1394 if (lock && !(info->flags & VM_LOCKED)) {
1395 if (!user_shm_lock(inode->i_size, user))
1397 info->flags |= VM_LOCKED;
1398 mapping_set_unevictable(file->f_mapping);
1400 if (!lock && (info->flags & VM_LOCKED) && user) {
1401 user_shm_unlock(inode->i_size, user);
1402 info->flags &= ~VM_LOCKED;
1403 mapping_clear_unevictable(file->f_mapping);
1408 spin_unlock(&info->lock);
1412 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1414 file_accessed(file);
1415 vma->vm_ops = &shmem_vm_ops;
1419 static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
1420 umode_t mode, dev_t dev, unsigned long flags)
1422 struct inode *inode;
1423 struct shmem_inode_info *info;
1424 struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1426 if (shmem_reserve_inode(sb))
1429 inode = new_inode(sb);
1431 inode->i_ino = get_next_ino();
1432 inode_init_owner(inode, dir, mode);
1433 inode->i_blocks = 0;
1434 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1435 inode->i_generation = get_seconds();
1436 info = SHMEM_I(inode);
1437 memset(info, 0, (char *)inode - (char *)info);
1438 spin_lock_init(&info->lock);
1439 info->seals = F_SEAL_SEAL;
1440 info->flags = flags & VM_NORESERVE;
1441 INIT_LIST_HEAD(&info->swaplist);
1442 simple_xattrs_init(&info->xattrs);
1443 cache_no_acl(inode);
1445 switch (mode & S_IFMT) {
1447 inode->i_op = &shmem_special_inode_operations;
1448 init_special_inode(inode, mode, dev);
1451 inode->i_mapping->a_ops = &shmem_aops;
1452 inode->i_op = &shmem_inode_operations;
1453 inode->i_fop = &shmem_file_operations;
1454 mpol_shared_policy_init(&info->policy,
1455 shmem_get_sbmpol(sbinfo));
1459 /* Some things misbehave if size == 0 on a directory */
1460 inode->i_size = 2 * BOGO_DIRENT_SIZE;
1461 inode->i_op = &shmem_dir_inode_operations;
1462 inode->i_fop = &simple_dir_operations;
1466 * Must not load anything in the rbtree,
1467 * mpol_free_shared_policy will not be called.
1469 mpol_shared_policy_init(&info->policy, NULL);
1473 shmem_free_inode(sb);
1477 bool shmem_mapping(struct address_space *mapping)
1482 return mapping->host->i_sb->s_op == &shmem_ops;
1486 static const struct inode_operations shmem_symlink_inode_operations;
1487 static const struct inode_operations shmem_short_symlink_operations;
1489 #ifdef CONFIG_TMPFS_XATTR
1490 static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
1492 #define shmem_initxattrs NULL
1496 shmem_write_begin(struct file *file, struct address_space *mapping,
1497 loff_t pos, unsigned len, unsigned flags,
1498 struct page **pagep, void **fsdata)
1500 struct inode *inode = mapping->host;
1501 struct shmem_inode_info *info = SHMEM_I(inode);
1502 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1504 /* i_mutex is held by caller */
1505 if (unlikely(info->seals)) {
1506 if (info->seals & F_SEAL_WRITE)
1508 if ((info->seals & F_SEAL_GROW) && pos + len > inode->i_size)
1512 return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
1516 shmem_write_end(struct file *file, struct address_space *mapping,
1517 loff_t pos, unsigned len, unsigned copied,
1518 struct page *page, void *fsdata)
1520 struct inode *inode = mapping->host;
1522 if (pos + copied > inode->i_size)
1523 i_size_write(inode, pos + copied);
1525 if (!PageUptodate(page)) {
1526 if (copied < PAGE_CACHE_SIZE) {
1527 unsigned from = pos & (PAGE_CACHE_SIZE - 1);
1528 zero_user_segments(page, 0, from,
1529 from + copied, PAGE_CACHE_SIZE);
1531 SetPageUptodate(page);
1533 set_page_dirty(page);
1535 page_cache_release(page);
1540 static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
1542 struct file *file = iocb->ki_filp;
1543 struct inode *inode = file_inode(file);
1544 struct address_space *mapping = inode->i_mapping;
1546 unsigned long offset;
1547 enum sgp_type sgp = SGP_READ;
1550 loff_t *ppos = &iocb->ki_pos;
1553 * Might this read be for a stacking filesystem? Then when reading
1554 * holes of a sparse file, we actually need to allocate those pages,
1555 * and even mark them dirty, so it cannot exceed the max_blocks limit.
1557 if (!iter_is_iovec(to))
1560 index = *ppos >> PAGE_CACHE_SHIFT;
1561 offset = *ppos & ~PAGE_CACHE_MASK;
1564 struct page *page = NULL;
1566 unsigned long nr, ret;
1567 loff_t i_size = i_size_read(inode);
1569 end_index = i_size >> PAGE_CACHE_SHIFT;
1570 if (index > end_index)
1572 if (index == end_index) {
1573 nr = i_size & ~PAGE_CACHE_MASK;
1578 error = shmem_getpage(inode, index, &page, sgp, NULL);
1580 if (error == -EINVAL)
1588 * We must evaluate after, since reads (unlike writes)
1589 * are called without i_mutex protection against truncate
1591 nr = PAGE_CACHE_SIZE;
1592 i_size = i_size_read(inode);
1593 end_index = i_size >> PAGE_CACHE_SHIFT;
1594 if (index == end_index) {
1595 nr = i_size & ~PAGE_CACHE_MASK;
1598 page_cache_release(page);
1606 * If users can be writing to this page using arbitrary
1607 * virtual addresses, take care about potential aliasing
1608 * before reading the page on the kernel side.
1610 if (mapping_writably_mapped(mapping))
1611 flush_dcache_page(page);
1613 * Mark the page accessed if we read the beginning.
1616 mark_page_accessed(page);
1618 page = ZERO_PAGE(0);
1619 page_cache_get(page);
1623 * Ok, we have the page, and it's up-to-date, so
1624 * now we can copy it to user space...
1626 ret = copy_page_to_iter(page, offset, nr, to);
1629 index += offset >> PAGE_CACHE_SHIFT;
1630 offset &= ~PAGE_CACHE_MASK;
1632 page_cache_release(page);
1633 if (!iov_iter_count(to))
1642 *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1643 file_accessed(file);
1644 return retval ? retval : error;
1647 static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
1648 struct pipe_inode_info *pipe, size_t len,
1651 struct address_space *mapping = in->f_mapping;
1652 struct inode *inode = mapping->host;
1653 unsigned int loff, nr_pages, req_pages;
1654 struct page *pages[PIPE_DEF_BUFFERS];
1655 struct partial_page partial[PIPE_DEF_BUFFERS];
1657 pgoff_t index, end_index;
1660 struct splice_pipe_desc spd = {
1663 .nr_pages_max = PIPE_DEF_BUFFERS,
1665 .ops = &page_cache_pipe_buf_ops,
1666 .spd_release = spd_release_page,
1669 isize = i_size_read(inode);
1670 if (unlikely(*ppos >= isize))
1673 left = isize - *ppos;
1674 if (unlikely(left < len))
1677 if (splice_grow_spd(pipe, &spd))
1680 index = *ppos >> PAGE_CACHE_SHIFT;
1681 loff = *ppos & ~PAGE_CACHE_MASK;
1682 req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1683 nr_pages = min(req_pages, spd.nr_pages_max);
1685 spd.nr_pages = find_get_pages_contig(mapping, index,
1686 nr_pages, spd.pages);
1687 index += spd.nr_pages;
1690 while (spd.nr_pages < nr_pages) {
1691 error = shmem_getpage(inode, index, &page, SGP_CACHE, NULL);
1695 spd.pages[spd.nr_pages++] = page;
1699 index = *ppos >> PAGE_CACHE_SHIFT;
1700 nr_pages = spd.nr_pages;
1703 for (page_nr = 0; page_nr < nr_pages; page_nr++) {
1704 unsigned int this_len;
1709 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
1710 page = spd.pages[page_nr];
1712 if (!PageUptodate(page) || page->mapping != mapping) {
1713 error = shmem_getpage(inode, index, &page,
1718 page_cache_release(spd.pages[page_nr]);
1719 spd.pages[page_nr] = page;
1722 isize = i_size_read(inode);
1723 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1724 if (unlikely(!isize || index > end_index))
1727 if (end_index == index) {
1730 plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1734 this_len = min(this_len, plen - loff);
1738 spd.partial[page_nr].offset = loff;
1739 spd.partial[page_nr].len = this_len;
1746 while (page_nr < nr_pages)
1747 page_cache_release(spd.pages[page_nr++]);
1750 error = splice_to_pipe(pipe, &spd);
1752 splice_shrink_spd(&spd);
1762 * llseek SEEK_DATA or SEEK_HOLE through the radix_tree.
1764 static pgoff_t shmem_seek_hole_data(struct address_space *mapping,
1765 pgoff_t index, pgoff_t end, int whence)
1768 struct pagevec pvec;
1769 pgoff_t indices[PAGEVEC_SIZE];
1773 pagevec_init(&pvec, 0);
1774 pvec.nr = 1; /* start small: we may be there already */
1776 pvec.nr = find_get_entries(mapping, index,
1777 pvec.nr, pvec.pages, indices);
1779 if (whence == SEEK_DATA)
1783 for (i = 0; i < pvec.nr; i++, index++) {
1784 if (index < indices[i]) {
1785 if (whence == SEEK_HOLE) {
1791 page = pvec.pages[i];
1792 if (page && !radix_tree_exceptional_entry(page)) {
1793 if (!PageUptodate(page))
1797 (page && whence == SEEK_DATA) ||
1798 (!page && whence == SEEK_HOLE)) {
1803 pagevec_remove_exceptionals(&pvec);
1804 pagevec_release(&pvec);
1805 pvec.nr = PAGEVEC_SIZE;
1811 static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence)
1813 struct address_space *mapping = file->f_mapping;
1814 struct inode *inode = mapping->host;
1818 if (whence != SEEK_DATA && whence != SEEK_HOLE)
1819 return generic_file_llseek_size(file, offset, whence,
1820 MAX_LFS_FILESIZE, i_size_read(inode));
1821 mutex_lock(&inode->i_mutex);
1822 /* We're holding i_mutex so we can access i_size directly */
1826 else if (offset >= inode->i_size)
1829 start = offset >> PAGE_CACHE_SHIFT;
1830 end = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1831 new_offset = shmem_seek_hole_data(mapping, start, end, whence);
1832 new_offset <<= PAGE_CACHE_SHIFT;
1833 if (new_offset > offset) {
1834 if (new_offset < inode->i_size)
1835 offset = new_offset;
1836 else if (whence == SEEK_DATA)
1839 offset = inode->i_size;
1844 offset = vfs_setpos(file, offset, MAX_LFS_FILESIZE);
1845 mutex_unlock(&inode->i_mutex);
1850 * We need a tag: a new tag would expand every radix_tree_node by 8 bytes,
1851 * so reuse a tag which we firmly believe is never set or cleared on shmem.
1853 #define SHMEM_TAG_PINNED PAGECACHE_TAG_TOWRITE
1854 #define LAST_SCAN 4 /* about 150ms max */
1856 static void shmem_tag_pins(struct address_space *mapping)
1858 struct radix_tree_iter iter;
1868 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1869 page = radix_tree_deref_slot(slot);
1870 if (!page || radix_tree_exception(page)) {
1871 if (radix_tree_deref_retry(page))
1873 } else if (page_count(page) - page_mapcount(page) > 1) {
1874 spin_lock_irq(&mapping->tree_lock);
1875 radix_tree_tag_set(&mapping->page_tree, iter.index,
1877 spin_unlock_irq(&mapping->tree_lock);
1880 if (need_resched()) {
1882 start = iter.index + 1;
1890 * Setting SEAL_WRITE requires us to verify there's no pending writer. However,
1891 * via get_user_pages(), drivers might have some pending I/O without any active
1892 * user-space mappings (eg., direct-IO, AIO). Therefore, we look at all pages
1893 * and see whether it has an elevated ref-count. If so, we tag them and wait for
1894 * them to be dropped.
1895 * The caller must guarantee that no new user will acquire writable references
1896 * to those pages to avoid races.
1898 static int shmem_wait_for_pins(struct address_space *mapping)
1900 struct radix_tree_iter iter;
1906 shmem_tag_pins(mapping);
1909 for (scan = 0; scan <= LAST_SCAN; scan++) {
1910 if (!radix_tree_tagged(&mapping->page_tree, SHMEM_TAG_PINNED))
1914 lru_add_drain_all();
1915 else if (schedule_timeout_killable((HZ << scan) / 200))
1921 radix_tree_for_each_tagged(slot, &mapping->page_tree, &iter,
1922 start, SHMEM_TAG_PINNED) {
1924 page = radix_tree_deref_slot(slot);
1925 if (radix_tree_exception(page)) {
1926 if (radix_tree_deref_retry(page))
1933 page_count(page) - page_mapcount(page) != 1) {
1934 if (scan < LAST_SCAN)
1935 goto continue_resched;
1938 * On the last scan, we clean up all those tags
1939 * we inserted; but make a note that we still
1940 * found pages pinned.
1945 spin_lock_irq(&mapping->tree_lock);
1946 radix_tree_tag_clear(&mapping->page_tree,
1947 iter.index, SHMEM_TAG_PINNED);
1948 spin_unlock_irq(&mapping->tree_lock);
1950 if (need_resched()) {
1952 start = iter.index + 1;
1962 #define F_ALL_SEALS (F_SEAL_SEAL | \
1967 int shmem_add_seals(struct file *file, unsigned int seals)
1969 struct inode *inode = file_inode(file);
1970 struct shmem_inode_info *info = SHMEM_I(inode);
1975 * Sealing allows multiple parties to share a shmem-file but restrict
1976 * access to a specific subset of file operations. Seals can only be
1977 * added, but never removed. This way, mutually untrusted parties can
1978 * share common memory regions with a well-defined policy. A malicious
1979 * peer can thus never perform unwanted operations on a shared object.
1981 * Seals are only supported on special shmem-files and always affect
1982 * the whole underlying inode. Once a seal is set, it may prevent some
1983 * kinds of access to the file. Currently, the following seals are
1985 * SEAL_SEAL: Prevent further seals from being set on this file
1986 * SEAL_SHRINK: Prevent the file from shrinking
1987 * SEAL_GROW: Prevent the file from growing
1988 * SEAL_WRITE: Prevent write access to the file
1990 * As we don't require any trust relationship between two parties, we
1991 * must prevent seals from being removed. Therefore, sealing a file
1992 * only adds a given set of seals to the file, it never touches
1993 * existing seals. Furthermore, the "setting seals"-operation can be
1994 * sealed itself, which basically prevents any further seal from being
1997 * Semantics of sealing are only defined on volatile files. Only
1998 * anonymous shmem files support sealing. More importantly, seals are
1999 * never written to disk. Therefore, there's no plan to support it on
2003 if (file->f_op != &shmem_file_operations)
2005 if (!(file->f_mode & FMODE_WRITE))
2007 if (seals & ~(unsigned int)F_ALL_SEALS)
2010 mutex_lock(&inode->i_mutex);
2012 if (info->seals & F_SEAL_SEAL) {
2017 if ((seals & F_SEAL_WRITE) && !(info->seals & F_SEAL_WRITE)) {
2018 error = mapping_deny_writable(file->f_mapping);
2022 error = shmem_wait_for_pins(file->f_mapping);
2024 mapping_allow_writable(file->f_mapping);
2029 info->seals |= seals;
2033 mutex_unlock(&inode->i_mutex);
2036 EXPORT_SYMBOL_GPL(shmem_add_seals);
2038 int shmem_get_seals(struct file *file)
2040 if (file->f_op != &shmem_file_operations)
2043 return SHMEM_I(file_inode(file))->seals;
2045 EXPORT_SYMBOL_GPL(shmem_get_seals);
2047 long shmem_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
2053 /* disallow upper 32bit */
2057 error = shmem_add_seals(file, arg);
2060 error = shmem_get_seals(file);
2070 static long shmem_fallocate(struct file *file, int mode, loff_t offset,
2073 struct inode *inode = file_inode(file);
2074 struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
2075 struct shmem_inode_info *info = SHMEM_I(inode);
2076 struct shmem_falloc shmem_falloc;
2077 pgoff_t start, index, end;
2080 if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
2083 mutex_lock(&inode->i_mutex);
2085 if (mode & FALLOC_FL_PUNCH_HOLE) {
2086 struct address_space *mapping = file->f_mapping;
2087 loff_t unmap_start = round_up(offset, PAGE_SIZE);
2088 loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1;
2089 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(shmem_falloc_waitq);
2091 /* protected by i_mutex */
2092 if (info->seals & F_SEAL_WRITE) {
2097 shmem_falloc.waitq = &shmem_falloc_waitq;
2098 shmem_falloc.start = unmap_start >> PAGE_SHIFT;
2099 shmem_falloc.next = (unmap_end + 1) >> PAGE_SHIFT;
2100 spin_lock(&inode->i_lock);
2101 inode->i_private = &shmem_falloc;
2102 spin_unlock(&inode->i_lock);
2104 if ((u64)unmap_end > (u64)unmap_start)
2105 unmap_mapping_range(mapping, unmap_start,
2106 1 + unmap_end - unmap_start, 0);
2107 shmem_truncate_range(inode, offset, offset + len - 1);
2108 /* No need to unmap again: hole-punching leaves COWed pages */
2110 spin_lock(&inode->i_lock);
2111 inode->i_private = NULL;
2112 wake_up_all(&shmem_falloc_waitq);
2113 spin_unlock(&inode->i_lock);
2118 /* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */
2119 error = inode_newsize_ok(inode, offset + len);
2123 if ((info->seals & F_SEAL_GROW) && offset + len > inode->i_size) {
2128 start = offset >> PAGE_CACHE_SHIFT;
2129 end = (offset + len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
2130 /* Try to avoid a swapstorm if len is impossible to satisfy */
2131 if (sbinfo->max_blocks && end - start > sbinfo->max_blocks) {
2136 shmem_falloc.waitq = NULL;
2137 shmem_falloc.start = start;
2138 shmem_falloc.next = start;
2139 shmem_falloc.nr_falloced = 0;
2140 shmem_falloc.nr_unswapped = 0;
2141 spin_lock(&inode->i_lock);
2142 inode->i_private = &shmem_falloc;
2143 spin_unlock(&inode->i_lock);
2145 for (index = start; index < end; index++) {
2149 * Good, the fallocate(2) manpage permits EINTR: we may have
2150 * been interrupted because we are using up too much memory.
2152 if (signal_pending(current))
2154 else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
2157 error = shmem_getpage(inode, index, &page, SGP_FALLOC,
2160 /* Remove the !PageUptodate pages we added */
2161 shmem_undo_range(inode,
2162 (loff_t)start << PAGE_CACHE_SHIFT,
2163 (loff_t)index << PAGE_CACHE_SHIFT, true);
2168 * Inform shmem_writepage() how far we have reached.
2169 * No need for lock or barrier: we have the page lock.
2171 shmem_falloc.next++;
2172 if (!PageUptodate(page))
2173 shmem_falloc.nr_falloced++;
2176 * If !PageUptodate, leave it that way so that freeable pages
2177 * can be recognized if we need to rollback on error later.
2178 * But set_page_dirty so that memory pressure will swap rather
2179 * than free the pages we are allocating (and SGP_CACHE pages
2180 * might still be clean: we now need to mark those dirty too).
2182 set_page_dirty(page);
2184 page_cache_release(page);
2188 if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
2189 i_size_write(inode, offset + len);
2190 inode->i_ctime = CURRENT_TIME;
2192 spin_lock(&inode->i_lock);
2193 inode->i_private = NULL;
2194 spin_unlock(&inode->i_lock);
2196 mutex_unlock(&inode->i_mutex);
2200 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
2202 struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
2204 buf->f_type = TMPFS_MAGIC;
2205 buf->f_bsize = PAGE_CACHE_SIZE;
2206 buf->f_namelen = NAME_MAX;
2207 if (sbinfo->max_blocks) {
2208 buf->f_blocks = sbinfo->max_blocks;
2210 buf->f_bfree = sbinfo->max_blocks -
2211 percpu_counter_sum(&sbinfo->used_blocks);
2213 if (sbinfo->max_inodes) {
2214 buf->f_files = sbinfo->max_inodes;
2215 buf->f_ffree = sbinfo->free_inodes;
2217 /* else leave those fields 0 like simple_statfs */
2222 * File creation. Allocate an inode, and we're done..
2225 shmem_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
2227 struct inode *inode;
2228 int error = -ENOSPC;
2230 inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
2232 error = simple_acl_create(dir, inode);
2235 error = security_inode_init_security(inode, dir,
2237 shmem_initxattrs, NULL);
2238 if (error && error != -EOPNOTSUPP)
2242 dir->i_size += BOGO_DIRENT_SIZE;
2243 dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2244 d_instantiate(dentry, inode);
2245 dget(dentry); /* Extra count - pin the dentry in core */
2254 shmem_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
2256 struct inode *inode;
2257 int error = -ENOSPC;
2259 inode = shmem_get_inode(dir->i_sb, dir, mode, 0, VM_NORESERVE);
2261 error = security_inode_init_security(inode, dir,
2263 shmem_initxattrs, NULL);
2264 if (error && error != -EOPNOTSUPP)
2266 error = simple_acl_create(dir, inode);
2269 d_tmpfile(dentry, inode);
2277 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
2281 if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
2287 static int shmem_create(struct inode *dir, struct dentry *dentry, umode_t mode,
2290 return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
2296 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
2298 struct inode *inode = d_inode(old_dentry);
2302 * No ordinary (disk based) filesystem counts links as inodes;
2303 * but each new link needs a new dentry, pinning lowmem, and
2304 * tmpfs dentries cannot be pruned until they are unlinked.
2306 ret = shmem_reserve_inode(inode->i_sb);
2310 dir->i_size += BOGO_DIRENT_SIZE;
2311 inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2313 ihold(inode); /* New dentry reference */
2314 dget(dentry); /* Extra pinning count for the created dentry */
2315 d_instantiate(dentry, inode);
2320 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
2322 struct inode *inode = d_inode(dentry);
2324 if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
2325 shmem_free_inode(inode->i_sb);
2327 dir->i_size -= BOGO_DIRENT_SIZE;
2328 inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2330 dput(dentry); /* Undo the count from "create" - this does all the work */
2334 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
2336 if (!simple_empty(dentry))
2339 drop_nlink(d_inode(dentry));
2341 return shmem_unlink(dir, dentry);
2344 static int shmem_exchange(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
2346 bool old_is_dir = d_is_dir(old_dentry);
2347 bool new_is_dir = d_is_dir(new_dentry);
2349 if (old_dir != new_dir && old_is_dir != new_is_dir) {
2351 drop_nlink(old_dir);
2354 drop_nlink(new_dir);
2358 old_dir->i_ctime = old_dir->i_mtime =
2359 new_dir->i_ctime = new_dir->i_mtime =
2360 d_inode(old_dentry)->i_ctime =
2361 d_inode(new_dentry)->i_ctime = CURRENT_TIME;
2366 static int shmem_whiteout(struct inode *old_dir, struct dentry *old_dentry)
2368 struct dentry *whiteout;
2371 whiteout = d_alloc(old_dentry->d_parent, &old_dentry->d_name);
2375 error = shmem_mknod(old_dir, whiteout,
2376 S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
2382 * Cheat and hash the whiteout while the old dentry is still in
2383 * place, instead of playing games with FS_RENAME_DOES_D_MOVE.
2385 * d_lookup() will consistently find one of them at this point,
2386 * not sure which one, but that isn't even important.
2393 * The VFS layer already does all the dentry stuff for rename,
2394 * we just have to decrement the usage count for the target if
2395 * it exists so that the VFS layer correctly free's it when it
2398 static int shmem_rename2(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry, unsigned int flags)
2400 struct inode *inode = d_inode(old_dentry);
2401 int they_are_dirs = S_ISDIR(inode->i_mode);
2403 if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
2406 if (flags & RENAME_EXCHANGE)
2407 return shmem_exchange(old_dir, old_dentry, new_dir, new_dentry);
2409 if (!simple_empty(new_dentry))
2412 if (flags & RENAME_WHITEOUT) {
2415 error = shmem_whiteout(old_dir, old_dentry);
2420 if (d_really_is_positive(new_dentry)) {
2421 (void) shmem_unlink(new_dir, new_dentry);
2422 if (they_are_dirs) {
2423 drop_nlink(d_inode(new_dentry));
2424 drop_nlink(old_dir);
2426 } else if (they_are_dirs) {
2427 drop_nlink(old_dir);
2431 old_dir->i_size -= BOGO_DIRENT_SIZE;
2432 new_dir->i_size += BOGO_DIRENT_SIZE;
2433 old_dir->i_ctime = old_dir->i_mtime =
2434 new_dir->i_ctime = new_dir->i_mtime =
2435 inode->i_ctime = CURRENT_TIME;
2439 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
2443 struct inode *inode;
2446 struct shmem_inode_info *info;
2448 len = strlen(symname) + 1;
2449 if (len > PAGE_CACHE_SIZE)
2450 return -ENAMETOOLONG;
2452 inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE);
2456 error = security_inode_init_security(inode, dir, &dentry->d_name,
2457 shmem_initxattrs, NULL);
2459 if (error != -EOPNOTSUPP) {
2466 info = SHMEM_I(inode);
2467 inode->i_size = len-1;
2468 if (len <= SHORT_SYMLINK_LEN) {
2469 info->symlink = kmemdup(symname, len, GFP_KERNEL);
2470 if (!info->symlink) {
2474 inode->i_op = &shmem_short_symlink_operations;
2475 inode->i_link = info->symlink;
2477 error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
2482 inode->i_mapping->a_ops = &shmem_aops;
2483 inode->i_op = &shmem_symlink_inode_operations;
2484 kaddr = kmap_atomic(page);
2485 memcpy(kaddr, symname, len);
2486 kunmap_atomic(kaddr);
2487 SetPageUptodate(page);
2488 set_page_dirty(page);
2490 page_cache_release(page);
2492 dir->i_size += BOGO_DIRENT_SIZE;
2493 dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2494 d_instantiate(dentry, inode);
2499 static const char *shmem_follow_link(struct dentry *dentry, void **cookie)
2501 struct page *page = NULL;
2502 int error = shmem_getpage(d_inode(dentry), 0, &page, SGP_READ, NULL);
2504 return ERR_PTR(error);
2510 static void shmem_put_link(struct inode *unused, void *cookie)
2512 struct page *page = cookie;
2514 mark_page_accessed(page);
2515 page_cache_release(page);
2518 #ifdef CONFIG_TMPFS_XATTR
2520 * Superblocks without xattr inode operations may get some security.* xattr
2521 * support from the LSM "for free". As soon as we have any other xattrs
2522 * like ACLs, we also need to implement the security.* handlers at
2523 * filesystem level, though.
2527 * Callback for security_inode_init_security() for acquiring xattrs.
2529 static int shmem_initxattrs(struct inode *inode,
2530 const struct xattr *xattr_array,
2533 struct shmem_inode_info *info = SHMEM_I(inode);
2534 const struct xattr *xattr;
2535 struct simple_xattr *new_xattr;
2538 for (xattr = xattr_array; xattr->name != NULL; xattr++) {
2539 new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len);
2543 len = strlen(xattr->name) + 1;
2544 new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
2546 if (!new_xattr->name) {
2551 memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
2552 XATTR_SECURITY_PREFIX_LEN);
2553 memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
2556 simple_xattr_list_add(&info->xattrs, new_xattr);
2562 static const struct xattr_handler *shmem_xattr_handlers[] = {
2563 #ifdef CONFIG_TMPFS_POSIX_ACL
2564 &posix_acl_access_xattr_handler,
2565 &posix_acl_default_xattr_handler,
2570 static int shmem_xattr_validate(const char *name)
2572 struct { const char *prefix; size_t len; } arr[] = {
2573 { XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN },
2574 { XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN }
2578 for (i = 0; i < ARRAY_SIZE(arr); i++) {
2579 size_t preflen = arr[i].len;
2580 if (strncmp(name, arr[i].prefix, preflen) == 0) {
2589 static ssize_t shmem_getxattr(struct dentry *dentry, const char *name,
2590 void *buffer, size_t size)
2592 struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
2596 * If this is a request for a synthetic attribute in the system.*
2597 * namespace use the generic infrastructure to resolve a handler
2598 * for it via sb->s_xattr.
2600 if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2601 return generic_getxattr(dentry, name, buffer, size);
2603 err = shmem_xattr_validate(name);
2607 return simple_xattr_get(&info->xattrs, name, buffer, size);
2610 static int shmem_setxattr(struct dentry *dentry, const char *name,
2611 const void *value, size_t size, int flags)
2613 struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
2617 * If this is a request for a synthetic attribute in the system.*
2618 * namespace use the generic infrastructure to resolve a handler
2619 * for it via sb->s_xattr.
2621 if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2622 return generic_setxattr(dentry, name, value, size, flags);
2624 err = shmem_xattr_validate(name);
2628 return simple_xattr_set(&info->xattrs, name, value, size, flags);
2631 static int shmem_removexattr(struct dentry *dentry, const char *name)
2633 struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
2637 * If this is a request for a synthetic attribute in the system.*
2638 * namespace use the generic infrastructure to resolve a handler
2639 * for it via sb->s_xattr.
2641 if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2642 return generic_removexattr(dentry, name);
2644 err = shmem_xattr_validate(name);
2648 return simple_xattr_remove(&info->xattrs, name);
2651 static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
2653 struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
2654 return simple_xattr_list(&info->xattrs, buffer, size);
2656 #endif /* CONFIG_TMPFS_XATTR */
2658 static const struct inode_operations shmem_short_symlink_operations = {
2659 .readlink = generic_readlink,
2660 .follow_link = simple_follow_link,
2661 #ifdef CONFIG_TMPFS_XATTR
2662 .setxattr = shmem_setxattr,
2663 .getxattr = shmem_getxattr,
2664 .listxattr = shmem_listxattr,
2665 .removexattr = shmem_removexattr,
2669 static const struct inode_operations shmem_symlink_inode_operations = {
2670 .readlink = generic_readlink,
2671 .follow_link = shmem_follow_link,
2672 .put_link = shmem_put_link,
2673 #ifdef CONFIG_TMPFS_XATTR
2674 .setxattr = shmem_setxattr,
2675 .getxattr = shmem_getxattr,
2676 .listxattr = shmem_listxattr,
2677 .removexattr = shmem_removexattr,
2681 static struct dentry *shmem_get_parent(struct dentry *child)
2683 return ERR_PTR(-ESTALE);
2686 static int shmem_match(struct inode *ino, void *vfh)
2690 inum = (inum << 32) | fh[1];
2691 return ino->i_ino == inum && fh[0] == ino->i_generation;
2694 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
2695 struct fid *fid, int fh_len, int fh_type)
2697 struct inode *inode;
2698 struct dentry *dentry = NULL;
2705 inum = (inum << 32) | fid->raw[1];
2707 inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
2708 shmem_match, fid->raw);
2710 dentry = d_find_alias(inode);
2717 static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len,
2718 struct inode *parent)
2722 return FILEID_INVALID;
2725 if (inode_unhashed(inode)) {
2726 /* Unfortunately insert_inode_hash is not idempotent,
2727 * so as we hash inodes here rather than at creation
2728 * time, we need a lock to ensure we only try
2731 static DEFINE_SPINLOCK(lock);
2733 if (inode_unhashed(inode))
2734 __insert_inode_hash(inode,
2735 inode->i_ino + inode->i_generation);
2739 fh[0] = inode->i_generation;
2740 fh[1] = inode->i_ino;
2741 fh[2] = ((__u64)inode->i_ino) >> 32;
2747 static const struct export_operations shmem_export_ops = {
2748 .get_parent = shmem_get_parent,
2749 .encode_fh = shmem_encode_fh,
2750 .fh_to_dentry = shmem_fh_to_dentry,
2753 static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
2756 char *this_char, *value, *rest;
2757 struct mempolicy *mpol = NULL;
2761 while (options != NULL) {
2762 this_char = options;
2765 * NUL-terminate this option: unfortunately,
2766 * mount options form a comma-separated list,
2767 * but mpol's nodelist may also contain commas.
2769 options = strchr(options, ',');
2770 if (options == NULL)
2773 if (!isdigit(*options)) {
2780 if ((value = strchr(this_char,'=')) != NULL) {
2784 "tmpfs: No value for mount option '%s'\n",
2789 if (!strcmp(this_char,"size")) {
2790 unsigned long long size;
2791 size = memparse(value,&rest);
2793 size <<= PAGE_SHIFT;
2794 size *= totalram_pages;
2800 sbinfo->max_blocks =
2801 DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
2802 } else if (!strcmp(this_char,"nr_blocks")) {
2803 sbinfo->max_blocks = memparse(value, &rest);
2806 } else if (!strcmp(this_char,"nr_inodes")) {
2807 sbinfo->max_inodes = memparse(value, &rest);
2810 } else if (!strcmp(this_char,"mode")) {
2813 sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
2816 } else if (!strcmp(this_char,"uid")) {
2819 uid = simple_strtoul(value, &rest, 0);
2822 sbinfo->uid = make_kuid(current_user_ns(), uid);
2823 if (!uid_valid(sbinfo->uid))
2825 } else if (!strcmp(this_char,"gid")) {
2828 gid = simple_strtoul(value, &rest, 0);
2831 sbinfo->gid = make_kgid(current_user_ns(), gid);
2832 if (!gid_valid(sbinfo->gid))
2834 } else if (!strcmp(this_char,"mpol")) {
2837 if (mpol_parse_str(value, &mpol))
2840 printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2845 sbinfo->mpol = mpol;
2849 printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2857 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2859 struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2860 struct shmem_sb_info config = *sbinfo;
2861 unsigned long inodes;
2862 int error = -EINVAL;
2865 if (shmem_parse_options(data, &config, true))
2868 spin_lock(&sbinfo->stat_lock);
2869 inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2870 if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0)
2872 if (config.max_inodes < inodes)
2875 * Those tests disallow limited->unlimited while any are in use;
2876 * but we must separately disallow unlimited->limited, because
2877 * in that case we have no record of how much is already in use.
2879 if (config.max_blocks && !sbinfo->max_blocks)
2881 if (config.max_inodes && !sbinfo->max_inodes)
2885 sbinfo->max_blocks = config.max_blocks;
2886 sbinfo->max_inodes = config.max_inodes;
2887 sbinfo->free_inodes = config.max_inodes - inodes;
2890 * Preserve previous mempolicy unless mpol remount option was specified.
2893 mpol_put(sbinfo->mpol);
2894 sbinfo->mpol = config.mpol; /* transfers initial ref */
2897 spin_unlock(&sbinfo->stat_lock);
2901 static int shmem_show_options(struct seq_file *seq, struct dentry *root)
2903 struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb);
2905 if (sbinfo->max_blocks != shmem_default_max_blocks())
2906 seq_printf(seq, ",size=%luk",
2907 sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
2908 if (sbinfo->max_inodes != shmem_default_max_inodes())
2909 seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
2910 if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
2911 seq_printf(seq, ",mode=%03ho", sbinfo->mode);
2912 if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
2913 seq_printf(seq, ",uid=%u",
2914 from_kuid_munged(&init_user_ns, sbinfo->uid));
2915 if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
2916 seq_printf(seq, ",gid=%u",
2917 from_kgid_munged(&init_user_ns, sbinfo->gid));
2918 shmem_show_mpol(seq, sbinfo->mpol);
2922 #define MFD_NAME_PREFIX "memfd:"
2923 #define MFD_NAME_PREFIX_LEN (sizeof(MFD_NAME_PREFIX) - 1)
2924 #define MFD_NAME_MAX_LEN (NAME_MAX - MFD_NAME_PREFIX_LEN)
2926 #define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING)
2928 SYSCALL_DEFINE2(memfd_create,
2929 const char __user *, uname,
2930 unsigned int, flags)
2932 struct shmem_inode_info *info;
2938 if (flags & ~(unsigned int)MFD_ALL_FLAGS)
2941 /* length includes terminating zero */
2942 len = strnlen_user(uname, MFD_NAME_MAX_LEN + 1);
2945 if (len > MFD_NAME_MAX_LEN + 1)
2948 name = kmalloc(len + MFD_NAME_PREFIX_LEN, GFP_TEMPORARY);
2952 strcpy(name, MFD_NAME_PREFIX);
2953 if (copy_from_user(&name[MFD_NAME_PREFIX_LEN], uname, len)) {
2958 /* terminating-zero may have changed after strnlen_user() returned */
2959 if (name[len + MFD_NAME_PREFIX_LEN - 1]) {
2964 fd = get_unused_fd_flags((flags & MFD_CLOEXEC) ? O_CLOEXEC : 0);
2970 file = shmem_file_setup(name, 0, VM_NORESERVE);
2972 error = PTR_ERR(file);
2975 info = SHMEM_I(file_inode(file));
2976 file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
2977 file->f_flags |= O_RDWR | O_LARGEFILE;
2978 if (flags & MFD_ALLOW_SEALING)
2979 info->seals &= ~F_SEAL_SEAL;
2981 fd_install(fd, file);
2992 #endif /* CONFIG_TMPFS */
2994 static void shmem_put_super(struct super_block *sb)
2996 struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2998 percpu_counter_destroy(&sbinfo->used_blocks);
2999 mpol_put(sbinfo->mpol);
3001 sb->s_fs_info = NULL;
3004 int shmem_fill_super(struct super_block *sb, void *data, int silent)
3006 struct inode *inode;
3007 struct shmem_sb_info *sbinfo;
3010 /* Round up to L1_CACHE_BYTES to resist false sharing */
3011 sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
3012 L1_CACHE_BYTES), GFP_KERNEL);
3016 sbinfo->mode = S_IRWXUGO | S_ISVTX;
3017 sbinfo->uid = current_fsuid();
3018 sbinfo->gid = current_fsgid();
3019 sb->s_fs_info = sbinfo;
3023 * Per default we only allow half of the physical ram per
3024 * tmpfs instance, limiting inodes to one per page of lowmem;
3025 * but the internal instance is left unlimited.
3027 if (!(sb->s_flags & MS_KERNMOUNT)) {
3028 sbinfo->max_blocks = shmem_default_max_blocks();
3029 sbinfo->max_inodes = shmem_default_max_inodes();
3030 if (shmem_parse_options(data, sbinfo, false)) {
3035 sb->s_flags |= MS_NOUSER;
3037 sb->s_export_op = &shmem_export_ops;
3038 sb->s_flags |= MS_NOSEC;
3040 sb->s_flags |= MS_NOUSER;
3043 spin_lock_init(&sbinfo->stat_lock);
3044 if (percpu_counter_init(&sbinfo->used_blocks, 0, GFP_KERNEL))
3046 sbinfo->free_inodes = sbinfo->max_inodes;
3048 sb->s_maxbytes = MAX_LFS_FILESIZE;
3049 sb->s_blocksize = PAGE_CACHE_SIZE;
3050 sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
3051 sb->s_magic = TMPFS_MAGIC;
3052 sb->s_op = &shmem_ops;
3053 sb->s_time_gran = 1;
3054 #ifdef CONFIG_TMPFS_XATTR
3055 sb->s_xattr = shmem_xattr_handlers;
3057 #ifdef CONFIG_TMPFS_POSIX_ACL
3058 sb->s_flags |= MS_POSIXACL;
3061 inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
3064 inode->i_uid = sbinfo->uid;
3065 inode->i_gid = sbinfo->gid;
3066 sb->s_root = d_make_root(inode);
3072 shmem_put_super(sb);
3076 static struct kmem_cache *shmem_inode_cachep;
3078 static struct inode *shmem_alloc_inode(struct super_block *sb)
3080 struct shmem_inode_info *info;
3081 info = kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
3084 return &info->vfs_inode;
3087 static void shmem_destroy_callback(struct rcu_head *head)
3089 struct inode *inode = container_of(head, struct inode, i_rcu);
3090 kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
3093 static void shmem_destroy_inode(struct inode *inode)
3095 if (S_ISREG(inode->i_mode))
3096 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
3097 call_rcu(&inode->i_rcu, shmem_destroy_callback);
3100 static void shmem_init_inode(void *foo)
3102 struct shmem_inode_info *info = foo;
3103 inode_init_once(&info->vfs_inode);
3106 static int shmem_init_inodecache(void)
3108 shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
3109 sizeof(struct shmem_inode_info),
3110 0, SLAB_PANIC, shmem_init_inode);
3114 static void shmem_destroy_inodecache(void)
3116 kmem_cache_destroy(shmem_inode_cachep);
3119 static const struct address_space_operations shmem_aops = {
3120 .writepage = shmem_writepage,
3121 .set_page_dirty = __set_page_dirty_no_writeback,
3123 .write_begin = shmem_write_begin,
3124 .write_end = shmem_write_end,
3126 #ifdef CONFIG_MIGRATION
3127 .migratepage = migrate_page,
3129 .error_remove_page = generic_error_remove_page,
3132 static const struct file_operations shmem_file_operations = {
3135 .llseek = shmem_file_llseek,
3136 .read_iter = shmem_file_read_iter,
3137 .write_iter = generic_file_write_iter,
3138 .fsync = noop_fsync,
3139 .splice_read = shmem_file_splice_read,
3140 .splice_write = iter_file_splice_write,
3141 .fallocate = shmem_fallocate,
3145 static const struct inode_operations shmem_inode_operations = {
3146 .getattr = shmem_getattr,
3147 .setattr = shmem_setattr,
3148 #ifdef CONFIG_TMPFS_XATTR
3149 .setxattr = shmem_setxattr,
3150 .getxattr = shmem_getxattr,
3151 .listxattr = shmem_listxattr,
3152 .removexattr = shmem_removexattr,
3153 .set_acl = simple_set_acl,
3157 static const struct inode_operations shmem_dir_inode_operations = {
3159 .create = shmem_create,
3160 .lookup = simple_lookup,
3162 .unlink = shmem_unlink,
3163 .symlink = shmem_symlink,
3164 .mkdir = shmem_mkdir,
3165 .rmdir = shmem_rmdir,
3166 .mknod = shmem_mknod,
3167 .rename2 = shmem_rename2,
3168 .tmpfile = shmem_tmpfile,
3170 #ifdef CONFIG_TMPFS_XATTR
3171 .setxattr = shmem_setxattr,
3172 .getxattr = shmem_getxattr,
3173 .listxattr = shmem_listxattr,
3174 .removexattr = shmem_removexattr,
3176 #ifdef CONFIG_TMPFS_POSIX_ACL
3177 .setattr = shmem_setattr,
3178 .set_acl = simple_set_acl,
3182 static const struct inode_operations shmem_special_inode_operations = {
3183 #ifdef CONFIG_TMPFS_XATTR
3184 .setxattr = shmem_setxattr,
3185 .getxattr = shmem_getxattr,
3186 .listxattr = shmem_listxattr,
3187 .removexattr = shmem_removexattr,
3189 #ifdef CONFIG_TMPFS_POSIX_ACL
3190 .setattr = shmem_setattr,
3191 .set_acl = simple_set_acl,
3195 static const struct super_operations shmem_ops = {
3196 .alloc_inode = shmem_alloc_inode,
3197 .destroy_inode = shmem_destroy_inode,
3199 .statfs = shmem_statfs,
3200 .remount_fs = shmem_remount_fs,
3201 .show_options = shmem_show_options,
3203 .evict_inode = shmem_evict_inode,
3204 .drop_inode = generic_delete_inode,
3205 .put_super = shmem_put_super,
3208 static const struct vm_operations_struct shmem_vm_ops = {
3209 .fault = shmem_fault,
3210 .map_pages = filemap_map_pages,
3212 .set_policy = shmem_set_policy,
3213 .get_policy = shmem_get_policy,
3217 static struct dentry *shmem_mount(struct file_system_type *fs_type,
3218 int flags, const char *dev_name, void *data)
3220 return mount_nodev(fs_type, flags, data, shmem_fill_super);
3223 static struct file_system_type shmem_fs_type = {
3224 .owner = THIS_MODULE,
3226 .mount = shmem_mount,
3227 .kill_sb = kill_litter_super,
3228 .fs_flags = FS_USERNS_MOUNT,
3231 int __init shmem_init(void)
3235 /* If rootfs called this, don't re-init */
3236 if (shmem_inode_cachep)
3239 error = shmem_init_inodecache();
3243 error = register_filesystem(&shmem_fs_type);
3245 printk(KERN_ERR "Could not register tmpfs\n");
3249 shm_mnt = kern_mount(&shmem_fs_type);
3250 if (IS_ERR(shm_mnt)) {
3251 error = PTR_ERR(shm_mnt);
3252 printk(KERN_ERR "Could not kern_mount tmpfs\n");
3258 unregister_filesystem(&shmem_fs_type);
3260 shmem_destroy_inodecache();
3262 shm_mnt = ERR_PTR(error);
3266 #else /* !CONFIG_SHMEM */
3269 * tiny-shmem: simple shmemfs and tmpfs using ramfs code
3271 * This is intended for small system where the benefits of the full
3272 * shmem code (swap-backed and resource-limited) are outweighed by
3273 * their complexity. On systems without swap this code should be
3274 * effectively equivalent, but much lighter weight.
3277 static struct file_system_type shmem_fs_type = {
3279 .mount = ramfs_mount,
3280 .kill_sb = kill_litter_super,
3281 .fs_flags = FS_USERNS_MOUNT,
3284 int __init shmem_init(void)
3286 BUG_ON(register_filesystem(&shmem_fs_type) != 0);
3288 shm_mnt = kern_mount(&shmem_fs_type);
3289 BUG_ON(IS_ERR(shm_mnt));
3294 int shmem_unuse(swp_entry_t swap, struct page *page)
3299 int shmem_lock(struct file *file, int lock, struct user_struct *user)
3304 void shmem_unlock_mapping(struct address_space *mapping)
3308 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
3310 truncate_inode_pages_range(inode->i_mapping, lstart, lend);
3312 EXPORT_SYMBOL_GPL(shmem_truncate_range);
3314 #define shmem_vm_ops generic_file_vm_ops
3315 #define shmem_file_operations ramfs_file_operations
3316 #define shmem_get_inode(sb, dir, mode, dev, flags) ramfs_get_inode(sb, dir, mode, dev)
3317 #define shmem_acct_size(flags, size) 0
3318 #define shmem_unacct_size(flags, size) do {} while (0)
3320 #endif /* CONFIG_SHMEM */
3324 static struct dentry_operations anon_ops = {
3325 .d_dname = simple_dname
3328 static struct file *__shmem_file_setup(const char *name, loff_t size,
3329 unsigned long flags, unsigned int i_flags)
3332 struct inode *inode;
3334 struct super_block *sb;
3337 if (IS_ERR(shm_mnt))
3338 return ERR_CAST(shm_mnt);
3340 if (size < 0 || size > MAX_LFS_FILESIZE)
3341 return ERR_PTR(-EINVAL);
3343 if (shmem_acct_size(flags, size))
3344 return ERR_PTR(-ENOMEM);
3346 res = ERR_PTR(-ENOMEM);
3348 this.len = strlen(name);
3349 this.hash = 0; /* will go */
3350 sb = shm_mnt->mnt_sb;
3351 path.mnt = mntget(shm_mnt);
3352 path.dentry = d_alloc_pseudo(sb, &this);
3355 d_set_d_op(path.dentry, &anon_ops);
3357 res = ERR_PTR(-ENOSPC);
3358 inode = shmem_get_inode(sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
3362 inode->i_flags |= i_flags;
3363 d_instantiate(path.dentry, inode);
3364 inode->i_size = size;
3365 clear_nlink(inode); /* It is unlinked */
3366 res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size));
3370 res = alloc_file(&path, FMODE_WRITE | FMODE_READ,
3371 &shmem_file_operations);
3378 shmem_unacct_size(flags, size);
3385 * shmem_kernel_file_setup - get an unlinked file living in tmpfs which must be
3386 * kernel internal. There will be NO LSM permission checks against the
3387 * underlying inode. So users of this interface must do LSM checks at a
3388 * higher layer. The users are the big_key and shm implementations. LSM
3389 * checks are provided at the key or shm level rather than the inode.
3390 * @name: name for dentry (to be seen in /proc/<pid>/maps
3391 * @size: size to be set for the file
3392 * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
3394 struct file *shmem_kernel_file_setup(const char *name, loff_t size, unsigned long flags)
3396 return __shmem_file_setup(name, size, flags, S_PRIVATE);
3400 * shmem_file_setup - get an unlinked file living in tmpfs
3401 * @name: name for dentry (to be seen in /proc/<pid>/maps
3402 * @size: size to be set for the file
3403 * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
3405 struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
3407 return __shmem_file_setup(name, size, flags, 0);
3409 EXPORT_SYMBOL_GPL(shmem_file_setup);
3412 * shmem_zero_setup - setup a shared anonymous mapping
3413 * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
3415 int shmem_zero_setup(struct vm_area_struct *vma)
3418 loff_t size = vma->vm_end - vma->vm_start;
3421 * Cloning a new file under mmap_sem leads to a lock ordering conflict
3422 * between XFS directory reading and selinux: since this file is only
3423 * accessible to the user through its mapping, use S_PRIVATE flag to
3424 * bypass file security, in the same way as shmem_kernel_file_setup().
3426 file = __shmem_file_setup("dev/zero", size, vma->vm_flags, S_PRIVATE);
3428 return PTR_ERR(file);
3432 vma->vm_file = file;
3433 vma->vm_ops = &shmem_vm_ops;
3438 * shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags.
3439 * @mapping: the page's address_space
3440 * @index: the page index
3441 * @gfp: the page allocator flags to use if allocating
3443 * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)",
3444 * with any new page allocations done using the specified allocation flags.
3445 * But read_cache_page_gfp() uses the ->readpage() method: which does not
3446 * suit tmpfs, since it may have pages in swapcache, and needs to find those
3447 * for itself; although drivers/gpu/drm i915 and ttm rely upon this support.
3449 * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in
3450 * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily.
3452 struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
3453 pgoff_t index, gfp_t gfp)
3456 struct inode *inode = mapping->host;
3460 BUG_ON(mapping->a_ops != &shmem_aops);
3461 error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE, gfp, NULL);
3463 page = ERR_PTR(error);
3469 * The tiny !SHMEM case uses ramfs without swap
3471 return read_cache_page_gfp(mapping, index, gfp);
3474 EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);