1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_PAGEMAP_H
3 #define _LINUX_PAGEMAP_H
6 * Copyright 1995 Linus Torvalds
10 #include <linux/list.h>
11 #include <linux/highmem.h>
12 #include <linux/compiler.h>
13 #include <linux/uaccess.h>
14 #include <linux/gfp.h>
15 #include <linux/bitops.h>
16 #include <linux/hardirq.h> /* for in_interrupt() */
17 #include <linux/hugetlb_inline.h>
22 * Bits in mapping->flags.
25 AS_EIO = 0, /* IO error on async write */
26 AS_ENOSPC = 1, /* ENOSPC on async write */
27 AS_MM_ALL_LOCKS = 2, /* under mm_take_all_locks() */
28 AS_UNEVICTABLE = 3, /* e.g., ramdisk, SHM_LOCK */
29 AS_EXITING = 4, /* final truncate in progress */
30 /* writeback related tags are not used */
31 AS_NO_WRITEBACK_TAGS = 5,
35 * mapping_set_error - record a writeback error in the address_space
36 * @mapping: the mapping in which an error should be set
37 * @error: the error to set in the mapping
39 * When writeback fails in some way, we must record that error so that
40 * userspace can be informed when fsync and the like are called. We endeavor
41 * to report errors on any file that was open at the time of the error. Some
42 * internal callers also need to know when writeback errors have occurred.
44 * When a writeback error occurs, most filesystems will want to call
45 * mapping_set_error to record the error in the mapping so that it can be
46 * reported when the application calls fsync(2).
48 static inline void mapping_set_error(struct address_space *mapping, int error)
53 /* Record in wb_err for checkers using errseq_t based tracking */
54 __filemap_set_wb_err(mapping, error);
56 /* Record it in superblock */
58 errseq_set(&mapping->host->i_sb->s_wb_err, error);
60 /* Record it in flags for now, for legacy callers */
62 set_bit(AS_ENOSPC, &mapping->flags);
64 set_bit(AS_EIO, &mapping->flags);
67 static inline void mapping_set_unevictable(struct address_space *mapping)
69 set_bit(AS_UNEVICTABLE, &mapping->flags);
72 static inline void mapping_clear_unevictable(struct address_space *mapping)
74 clear_bit(AS_UNEVICTABLE, &mapping->flags);
77 static inline bool mapping_unevictable(struct address_space *mapping)
79 return mapping && test_bit(AS_UNEVICTABLE, &mapping->flags);
82 static inline void mapping_set_exiting(struct address_space *mapping)
84 set_bit(AS_EXITING, &mapping->flags);
87 static inline int mapping_exiting(struct address_space *mapping)
89 return test_bit(AS_EXITING, &mapping->flags);
92 static inline void mapping_set_no_writeback_tags(struct address_space *mapping)
94 set_bit(AS_NO_WRITEBACK_TAGS, &mapping->flags);
97 static inline int mapping_use_writeback_tags(struct address_space *mapping)
99 return !test_bit(AS_NO_WRITEBACK_TAGS, &mapping->flags);
102 static inline gfp_t mapping_gfp_mask(struct address_space * mapping)
104 return mapping->gfp_mask;
107 /* Restricts the given gfp_mask to what the mapping allows. */
108 static inline gfp_t mapping_gfp_constraint(struct address_space *mapping,
111 return mapping_gfp_mask(mapping) & gfp_mask;
115 * This is non-atomic. Only to be used before the mapping is activated.
116 * Probably needs a barrier...
118 static inline void mapping_set_gfp_mask(struct address_space *m, gfp_t mask)
123 void release_pages(struct page **pages, int nr);
126 * speculatively take a reference to a page.
127 * If the page is free (_refcount == 0), then _refcount is untouched, and 0
128 * is returned. Otherwise, _refcount is incremented by 1 and 1 is returned.
130 * This function must be called inside the same rcu_read_lock() section as has
131 * been used to lookup the page in the pagecache radix-tree (or page table):
132 * this allows allocators to use a synchronize_rcu() to stabilize _refcount.
134 * Unless an RCU grace period has passed, the count of all pages coming out
135 * of the allocator must be considered unstable. page_count may return higher
136 * than expected, and put_page must be able to do the right thing when the
137 * page has been finished with, no matter what it is subsequently allocated
138 * for (because put_page is what is used here to drop an invalid speculative
141 * This is the interesting part of the lockless pagecache (and lockless
142 * get_user_pages) locking protocol, where the lookup-side (eg. find_get_page)
143 * has the following pattern:
144 * 1. find page in radix tree
145 * 2. conditionally increment refcount
146 * 3. check the page is still in pagecache (if no, goto 1)
148 * Remove-side that cares about stability of _refcount (eg. reclaim) has the
149 * following (with the i_pages lock held):
150 * A. atomically check refcount is correct and set it to 0 (atomic_cmpxchg)
151 * B. remove page from pagecache
154 * There are 2 critical interleavings that matter:
155 * - 2 runs before A: in this case, A sees elevated refcount and bails out
156 * - A runs before 2: in this case, 2 sees zero refcount and retries;
157 * subsequently, B will complete and 1 will find no page, causing the
158 * lookup to return NULL.
160 * It is possible that between 1 and 2, the page is removed then the exact same
161 * page is inserted into the same position in pagecache. That's OK: the
162 * old find_get_page using a lock could equally have run before or after
163 * such a re-insertion, depending on order that locks are granted.
165 * Lookups racing against pagecache insertion isn't a big problem: either 1
166 * will find the page or it will not. Likewise, the old find_get_page could run
167 * either before the insertion or afterwards, depending on timing.
169 static inline int __page_cache_add_speculative(struct page *page, int count)
171 #ifdef CONFIG_TINY_RCU
172 # ifdef CONFIG_PREEMPT_COUNT
173 VM_BUG_ON(!in_atomic() && !irqs_disabled());
176 * Preempt must be disabled here - we rely on rcu_read_lock doing
179 * Pagecache won't be truncated from interrupt context, so if we have
180 * found a page in the radix tree here, we have pinned its refcount by
181 * disabling preempt, and hence no need for the "speculative get" that
184 VM_BUG_ON_PAGE(page_count(page) == 0, page);
185 page_ref_add(page, count);
188 if (unlikely(!page_ref_add_unless(page, count, 0))) {
190 * Either the page has been freed, or will be freed.
191 * In either case, retry here and the caller should
192 * do the right thing (see comments above).
197 VM_BUG_ON_PAGE(PageTail(page), page);
202 static inline int page_cache_get_speculative(struct page *page)
204 return __page_cache_add_speculative(page, 1);
207 static inline int page_cache_add_speculative(struct page *page, int count)
209 return __page_cache_add_speculative(page, count);
213 * attach_page_private - Attach private data to a page.
214 * @page: Page to attach data to.
215 * @data: Data to attach to page.
217 * Attaching private data to a page increments the page's reference count.
218 * The data must be detached before the page will be freed.
220 static inline void attach_page_private(struct page *page, void *data)
223 set_page_private(page, (unsigned long)data);
224 SetPagePrivate(page);
228 * detach_page_private - Detach private data from a page.
229 * @page: Page to detach data from.
231 * Removes the data that was previously attached to the page and decrements
232 * the refcount on the page.
234 * Return: Data that was attached to the page.
236 static inline void *detach_page_private(struct page *page)
238 void *data = (void *)page_private(page);
240 if (!PagePrivate(page))
242 ClearPagePrivate(page);
243 set_page_private(page, 0);
250 extern struct page *__page_cache_alloc(gfp_t gfp);
252 static inline struct page *__page_cache_alloc(gfp_t gfp)
254 return alloc_pages(gfp, 0);
258 static inline struct page *page_cache_alloc(struct address_space *x)
260 return __page_cache_alloc(mapping_gfp_mask(x));
263 static inline gfp_t readahead_gfp_mask(struct address_space *x)
265 return mapping_gfp_mask(x) | __GFP_NORETRY | __GFP_NOWARN;
268 typedef int filler_t(void *, struct page *);
270 pgoff_t page_cache_next_miss(struct address_space *mapping,
271 pgoff_t index, unsigned long max_scan);
272 pgoff_t page_cache_prev_miss(struct address_space *mapping,
273 pgoff_t index, unsigned long max_scan);
275 #define FGP_ACCESSED 0x00000001
276 #define FGP_LOCK 0x00000002
277 #define FGP_CREAT 0x00000004
278 #define FGP_WRITE 0x00000008
279 #define FGP_NOFS 0x00000010
280 #define FGP_NOWAIT 0x00000020
281 #define FGP_FOR_MMAP 0x00000040
283 struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
284 int fgp_flags, gfp_t cache_gfp_mask);
287 * find_get_page - find and get a page reference
288 * @mapping: the address_space to search
289 * @offset: the page index
291 * Looks up the page cache slot at @mapping & @offset. If there is a
292 * page cache page, it is returned with an increased refcount.
294 * Otherwise, %NULL is returned.
296 static inline struct page *find_get_page(struct address_space *mapping,
299 return pagecache_get_page(mapping, offset, 0, 0);
302 static inline struct page *find_get_page_flags(struct address_space *mapping,
303 pgoff_t offset, int fgp_flags)
305 return pagecache_get_page(mapping, offset, fgp_flags, 0);
309 * find_lock_page - locate, pin and lock a pagecache page
310 * @mapping: the address_space to search
311 * @offset: the page index
313 * Looks up the page cache slot at @mapping & @offset. If there is a
314 * page cache page, it is returned locked and with an increased
317 * Otherwise, %NULL is returned.
319 * find_lock_page() may sleep.
321 static inline struct page *find_lock_page(struct address_space *mapping,
324 return pagecache_get_page(mapping, offset, FGP_LOCK, 0);
328 * find_or_create_page - locate or add a pagecache page
329 * @mapping: the page's address_space
330 * @index: the page's index into the mapping
331 * @gfp_mask: page allocation mode
333 * Looks up the page cache slot at @mapping & @offset. If there is a
334 * page cache page, it is returned locked and with an increased
337 * If the page is not present, a new page is allocated using @gfp_mask
338 * and added to the page cache and the VM's LRU list. The page is
339 * returned locked and with an increased refcount.
341 * On memory exhaustion, %NULL is returned.
343 * find_or_create_page() may sleep, even if @gfp_flags specifies an
346 static inline struct page *find_or_create_page(struct address_space *mapping,
347 pgoff_t index, gfp_t gfp_mask)
349 return pagecache_get_page(mapping, index,
350 FGP_LOCK|FGP_ACCESSED|FGP_CREAT,
355 * grab_cache_page_nowait - returns locked page at given index in given cache
356 * @mapping: target address_space
357 * @index: the page index
359 * Same as grab_cache_page(), but do not wait if the page is unavailable.
360 * This is intended for speculative data generators, where the data can
361 * be regenerated if the page couldn't be grabbed. This routine should
362 * be safe to call while holding the lock for another page.
364 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
365 * and deadlock against the caller's locked page.
367 static inline struct page *grab_cache_page_nowait(struct address_space *mapping,
370 return pagecache_get_page(mapping, index,
371 FGP_LOCK|FGP_CREAT|FGP_NOFS|FGP_NOWAIT,
372 mapping_gfp_mask(mapping));
376 * Given the page we found in the page cache, return the page corresponding
377 * to this index in the file
379 static inline struct page *find_subpage(struct page *head, pgoff_t index)
381 /* HugeTLBfs wants the head page regardless */
385 return head + (index & (thp_nr_pages(head) - 1));
388 struct page *find_get_entry(struct address_space *mapping, pgoff_t offset);
389 struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset);
390 unsigned find_get_entries(struct address_space *mapping, pgoff_t start,
391 unsigned int nr_entries, struct page **entries,
393 unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start,
394 pgoff_t end, unsigned int nr_pages,
395 struct page **pages);
396 static inline unsigned find_get_pages(struct address_space *mapping,
397 pgoff_t *start, unsigned int nr_pages,
400 return find_get_pages_range(mapping, start, (pgoff_t)-1, nr_pages,
403 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t start,
404 unsigned int nr_pages, struct page **pages);
405 unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index,
406 pgoff_t end, xa_mark_t tag, unsigned int nr_pages,
407 struct page **pages);
408 static inline unsigned find_get_pages_tag(struct address_space *mapping,
409 pgoff_t *index, xa_mark_t tag, unsigned int nr_pages,
412 return find_get_pages_range_tag(mapping, index, (pgoff_t)-1, tag,
416 struct page *grab_cache_page_write_begin(struct address_space *mapping,
417 pgoff_t index, unsigned flags);
420 * Returns locked page at given index in given cache, creating it if needed.
422 static inline struct page *grab_cache_page(struct address_space *mapping,
425 return find_or_create_page(mapping, index, mapping_gfp_mask(mapping));
428 extern struct page * read_cache_page(struct address_space *mapping,
429 pgoff_t index, filler_t *filler, void *data);
430 extern struct page * read_cache_page_gfp(struct address_space *mapping,
431 pgoff_t index, gfp_t gfp_mask);
432 extern int read_cache_pages(struct address_space *mapping,
433 struct list_head *pages, filler_t *filler, void *data);
435 static inline struct page *read_mapping_page(struct address_space *mapping,
436 pgoff_t index, void *data)
438 return read_cache_page(mapping, index, NULL, data);
442 * Get index of the page with in radix-tree
443 * (TODO: remove once hugetlb pages will have ->index in PAGE_SIZE)
445 static inline pgoff_t page_to_index(struct page *page)
449 if (likely(!PageTransTail(page)))
453 * We don't initialize ->index for tail pages: calculate based on
456 pgoff = compound_head(page)->index;
457 pgoff += page - compound_head(page);
462 * Get the offset in PAGE_SIZE.
463 * (TODO: hugepage should have ->index in PAGE_SIZE)
465 static inline pgoff_t page_to_pgoff(struct page *page)
467 if (unlikely(PageHeadHuge(page)))
468 return page->index << compound_order(page);
470 return page_to_index(page);
474 * Return byte-offset into filesystem object for page.
476 static inline loff_t page_offset(struct page *page)
478 return ((loff_t)page->index) << PAGE_SHIFT;
481 static inline loff_t page_file_offset(struct page *page)
483 return ((loff_t)page_index(page)) << PAGE_SHIFT;
486 extern pgoff_t linear_hugepage_index(struct vm_area_struct *vma,
487 unsigned long address);
489 static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
490 unsigned long address)
493 if (unlikely(is_vm_hugetlb_page(vma)))
494 return linear_hugepage_index(vma, address);
495 pgoff = (address - vma->vm_start) >> PAGE_SHIFT;
496 pgoff += vma->vm_pgoff;
500 /* This has the same layout as wait_bit_key - see fs/cachefiles/rdwr.c */
501 struct wait_page_key {
507 struct wait_page_queue {
510 wait_queue_entry_t wait;
513 static inline bool wake_page_match(struct wait_page_queue *wait_page,
514 struct wait_page_key *key)
516 if (wait_page->page != key->page)
520 if (wait_page->bit_nr != key->bit_nr)
526 extern void __lock_page(struct page *page);
527 extern int __lock_page_killable(struct page *page);
528 extern int __lock_page_async(struct page *page, struct wait_page_queue *wait);
529 extern int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
531 extern void unlock_page(struct page *page);
534 * Return true if the page was successfully locked
536 static inline int trylock_page(struct page *page)
538 page = compound_head(page);
539 return (likely(!test_and_set_bit_lock(PG_locked, &page->flags)));
543 * lock_page may only be called if we have the page's inode pinned.
545 static inline void lock_page(struct page *page)
548 if (!trylock_page(page))
553 * lock_page_killable is like lock_page but can be interrupted by fatal
554 * signals. It returns 0 if it locked the page and -EINTR if it was
555 * killed while waiting.
557 static inline int lock_page_killable(struct page *page)
560 if (!trylock_page(page))
561 return __lock_page_killable(page);
566 * lock_page_async - Lock the page, unless this would block. If the page
567 * is already locked, then queue a callback when the page becomes unlocked.
568 * This callback can then retry the operation.
570 * Returns 0 if the page is locked successfully, or -EIOCBQUEUED if the page
571 * was already locked and the callback defined in 'wait' was queued.
573 static inline int lock_page_async(struct page *page,
574 struct wait_page_queue *wait)
576 if (!trylock_page(page))
577 return __lock_page_async(page, wait);
582 * lock_page_or_retry - Lock the page, unless this would block and the
583 * caller indicated that it can handle a retry.
585 * Return value and mmap_lock implications depend on flags; see
586 * __lock_page_or_retry().
588 static inline int lock_page_or_retry(struct page *page, struct mm_struct *mm,
592 return trylock_page(page) || __lock_page_or_retry(page, mm, flags);
596 * This is exported only for wait_on_page_locked/wait_on_page_writeback, etc.,
597 * and should not be used directly.
599 extern void wait_on_page_bit(struct page *page, int bit_nr);
600 extern int wait_on_page_bit_killable(struct page *page, int bit_nr);
603 * Wait for a page to be unlocked.
605 * This must be called with the caller "holding" the page,
606 * ie with increased "page->count" so that the page won't
607 * go away during the wait..
609 static inline void wait_on_page_locked(struct page *page)
611 if (PageLocked(page))
612 wait_on_page_bit(compound_head(page), PG_locked);
615 static inline int wait_on_page_locked_killable(struct page *page)
617 if (!PageLocked(page))
619 return wait_on_page_bit_killable(compound_head(page), PG_locked);
622 extern void put_and_wait_on_page_locked(struct page *page);
624 void wait_on_page_writeback(struct page *page);
625 extern void end_page_writeback(struct page *page);
626 void wait_for_stable_page(struct page *page);
628 void page_endio(struct page *page, bool is_write, int err);
631 * Add an arbitrary waiter to a page's wait queue
633 extern void add_page_wait_queue(struct page *page, wait_queue_entry_t *waiter);
636 * Fault everything in given userspace address range in.
638 static inline int fault_in_pages_writeable(char __user *uaddr, int size)
640 char __user *end = uaddr + size - 1;
642 if (unlikely(size == 0))
645 if (unlikely(uaddr > end))
648 * Writing zeroes into userspace here is OK, because we know that if
649 * the zero gets there, we'll be overwriting it.
652 if (unlikely(__put_user(0, uaddr) != 0))
655 } while (uaddr <= end);
657 /* Check whether the range spilled into the next page. */
658 if (((unsigned long)uaddr & PAGE_MASK) ==
659 ((unsigned long)end & PAGE_MASK))
660 return __put_user(0, end);
665 static inline int fault_in_pages_readable(const char __user *uaddr, int size)
668 const char __user *end = uaddr + size - 1;
670 if (unlikely(size == 0))
673 if (unlikely(uaddr > end))
677 if (unlikely(__get_user(c, uaddr) != 0))
680 } while (uaddr <= end);
682 /* Check whether the range spilled into the next page. */
683 if (((unsigned long)uaddr & PAGE_MASK) ==
684 ((unsigned long)end & PAGE_MASK)) {
685 return __get_user(c, end);
692 int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
693 pgoff_t index, gfp_t gfp_mask);
694 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
695 pgoff_t index, gfp_t gfp_mask);
696 extern void delete_from_page_cache(struct page *page);
697 extern void __delete_from_page_cache(struct page *page, void *shadow);
698 int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask);
699 void delete_from_page_cache_batch(struct address_space *mapping,
700 struct pagevec *pvec);
702 #define VM_READAHEAD_PAGES (SZ_128K / PAGE_SIZE)
704 void page_cache_sync_readahead(struct address_space *, struct file_ra_state *,
705 struct file *, pgoff_t index, unsigned long req_count);
706 void page_cache_async_readahead(struct address_space *, struct file_ra_state *,
707 struct file *, struct page *, pgoff_t index,
708 unsigned long req_count);
709 void page_cache_readahead_unbounded(struct address_space *, struct file *,
710 pgoff_t index, unsigned long nr_to_read,
711 unsigned long lookahead_count);
714 * Like add_to_page_cache_locked, but used to add newly allocated pages:
715 * the page is new, so we can just run __SetPageLocked() against it.
717 static inline int add_to_page_cache(struct page *page,
718 struct address_space *mapping, pgoff_t offset, gfp_t gfp_mask)
722 __SetPageLocked(page);
723 error = add_to_page_cache_locked(page, mapping, offset, gfp_mask);
725 __ClearPageLocked(page);
730 * struct readahead_control - Describes a readahead request.
732 * A readahead request is for consecutive pages. Filesystems which
733 * implement the ->readahead method should call readahead_page() or
734 * readahead_page_batch() in a loop and attempt to start I/O against
735 * each page in the request.
737 * Most of the fields in this struct are private and should be accessed
738 * by the functions below.
740 * @file: The file, used primarily by network filesystems for authentication.
741 * May be NULL if invoked internally by the filesystem.
742 * @mapping: Readahead this filesystem object.
744 struct readahead_control {
746 struct address_space *mapping;
747 /* private: use the readahead_* accessors instead */
749 unsigned int _nr_pages;
750 unsigned int _batch_count;
754 * readahead_page - Get the next page to read.
755 * @rac: The current readahead request.
757 * Context: The page is locked and has an elevated refcount. The caller
758 * should decreases the refcount once the page has been submitted for I/O
759 * and unlock the page once all I/O to that page has completed.
760 * Return: A pointer to the next page, or %NULL if we are done.
762 static inline struct page *readahead_page(struct readahead_control *rac)
766 BUG_ON(rac->_batch_count > rac->_nr_pages);
767 rac->_nr_pages -= rac->_batch_count;
768 rac->_index += rac->_batch_count;
770 if (!rac->_nr_pages) {
771 rac->_batch_count = 0;
775 page = xa_load(&rac->mapping->i_pages, rac->_index);
776 VM_BUG_ON_PAGE(!PageLocked(page), page);
777 rac->_batch_count = thp_nr_pages(page);
782 static inline unsigned int __readahead_batch(struct readahead_control *rac,
783 struct page **array, unsigned int array_sz)
786 XA_STATE(xas, &rac->mapping->i_pages, 0);
789 BUG_ON(rac->_batch_count > rac->_nr_pages);
790 rac->_nr_pages -= rac->_batch_count;
791 rac->_index += rac->_batch_count;
792 rac->_batch_count = 0;
794 xas_set(&xas, rac->_index);
796 xas_for_each(&xas, page, rac->_index + rac->_nr_pages - 1) {
797 VM_BUG_ON_PAGE(!PageLocked(page), page);
798 VM_BUG_ON_PAGE(PageTail(page), page);
800 rac->_batch_count += thp_nr_pages(page);
803 * The page cache isn't using multi-index entries yet,
804 * so the xas cursor needs to be manually moved to the
805 * next index. This can be removed once the page cache
809 xas_set(&xas, rac->_index + rac->_batch_count);
820 * readahead_page_batch - Get a batch of pages to read.
821 * @rac: The current readahead request.
822 * @array: An array of pointers to struct page.
824 * Context: The pages are locked and have an elevated refcount. The caller
825 * should decreases the refcount once the page has been submitted for I/O
826 * and unlock the page once all I/O to that page has completed.
827 * Return: The number of pages placed in the array. 0 indicates the request
830 #define readahead_page_batch(rac, array) \
831 __readahead_batch(rac, array, ARRAY_SIZE(array))
834 * readahead_pos - The byte offset into the file of this readahead request.
835 * @rac: The readahead request.
837 static inline loff_t readahead_pos(struct readahead_control *rac)
839 return (loff_t)rac->_index * PAGE_SIZE;
843 * readahead_length - The number of bytes in this readahead request.
844 * @rac: The readahead request.
846 static inline loff_t readahead_length(struct readahead_control *rac)
848 return (loff_t)rac->_nr_pages * PAGE_SIZE;
852 * readahead_index - The index of the first page in this readahead request.
853 * @rac: The readahead request.
855 static inline pgoff_t readahead_index(struct readahead_control *rac)
861 * readahead_count - The number of pages in this readahead request.
862 * @rac: The readahead request.
864 static inline unsigned int readahead_count(struct readahead_control *rac)
866 return rac->_nr_pages;
869 static inline unsigned long dir_pages(struct inode *inode)
871 return (unsigned long)(inode->i_size + PAGE_SIZE - 1) >>
876 * page_mkwrite_check_truncate - check if page was truncated
877 * @page: the page to check
878 * @inode: the inode to check the page against
880 * Returns the number of bytes in the page up to EOF,
881 * or -EFAULT if the page was truncated.
883 static inline int page_mkwrite_check_truncate(struct page *page,
886 loff_t size = i_size_read(inode);
887 pgoff_t index = size >> PAGE_SHIFT;
888 int offset = offset_in_page(size);
890 if (page->mapping != inode->i_mapping)
893 /* page is wholly inside EOF */
894 if (page->index < index)
896 /* page is wholly past EOF */
897 if (page->index > index || !offset)
899 /* page is partially inside EOF */
903 #endif /* _LINUX_PAGEMAP_H */