1 #ifndef _LINUX_PAGEMAP_H
2 #define _LINUX_PAGEMAP_H
5 * Copyright 1995 Linus Torvalds
9 #include <linux/list.h>
10 #include <linux/highmem.h>
11 #include <linux/compiler.h>
12 #include <asm/uaccess.h>
13 #include <linux/gfp.h>
14 #include <linux/bitops.h>
15 #include <linux/hardirq.h> /* for in_interrupt() */
16 #include <linux/hugetlb_inline.h>
19 * Bits in mapping->flags. The lower __GFP_BITS_SHIFT bits are the page
20 * allocation mode flags.
23 AS_EIO = __GFP_BITS_SHIFT + 0, /* IO error on async write */
24 AS_ENOSPC = __GFP_BITS_SHIFT + 1, /* ENOSPC on async write */
25 AS_MM_ALL_LOCKS = __GFP_BITS_SHIFT + 2, /* under mm_take_all_locks() */
26 AS_UNEVICTABLE = __GFP_BITS_SHIFT + 3, /* e.g., ramdisk, SHM_LOCK */
27 AS_EXITING = __GFP_BITS_SHIFT + 4, /* final truncate in progress */
30 static inline void mapping_set_error(struct address_space *mapping, int error)
32 if (unlikely(error)) {
34 set_bit(AS_ENOSPC, &mapping->flags);
36 set_bit(AS_EIO, &mapping->flags);
40 static inline void mapping_set_unevictable(struct address_space *mapping)
42 set_bit(AS_UNEVICTABLE, &mapping->flags);
45 static inline void mapping_clear_unevictable(struct address_space *mapping)
47 clear_bit(AS_UNEVICTABLE, &mapping->flags);
50 static inline int mapping_unevictable(struct address_space *mapping)
53 return test_bit(AS_UNEVICTABLE, &mapping->flags);
57 static inline void mapping_set_exiting(struct address_space *mapping)
59 set_bit(AS_EXITING, &mapping->flags);
62 static inline int mapping_exiting(struct address_space *mapping)
64 return test_bit(AS_EXITING, &mapping->flags);
67 static inline gfp_t mapping_gfp_mask(struct address_space * mapping)
69 return (__force gfp_t)mapping->flags & __GFP_BITS_MASK;
72 /* Restricts the given gfp_mask to what the mapping allows. */
73 static inline gfp_t mapping_gfp_constraint(struct address_space *mapping,
76 return mapping_gfp_mask(mapping) & gfp_mask;
80 * This is non-atomic. Only to be used before the mapping is activated.
81 * Probably needs a barrier...
83 static inline void mapping_set_gfp_mask(struct address_space *m, gfp_t mask)
85 m->flags = (m->flags & ~(__force unsigned long)__GFP_BITS_MASK) |
86 (__force unsigned long)mask;
90 * The page cache can be done in larger chunks than
91 * one page, because it allows for more efficient
92 * throughput (it can then be mapped into user
93 * space in smaller chunks for same flexibility).
95 * Or rather, it _will_ be done in larger chunks.
97 #define PAGE_CACHE_SHIFT PAGE_SHIFT
98 #define PAGE_CACHE_SIZE PAGE_SIZE
99 #define PAGE_CACHE_MASK PAGE_MASK
100 #define PAGE_CACHE_ALIGN(addr) (((addr)+PAGE_CACHE_SIZE-1)&PAGE_CACHE_MASK)
102 #define page_cache_get(page) get_page(page)
103 #define page_cache_release(page) put_page(page)
104 void release_pages(struct page **pages, int nr, bool cold);
107 * speculatively take a reference to a page.
108 * If the page is free (_count == 0), then _count is untouched, and 0
109 * is returned. Otherwise, _count is incremented by 1 and 1 is returned.
111 * This function must be called inside the same rcu_read_lock() section as has
112 * been used to lookup the page in the pagecache radix-tree (or page table):
113 * this allows allocators to use a synchronize_rcu() to stabilize _count.
115 * Unless an RCU grace period has passed, the count of all pages coming out
116 * of the allocator must be considered unstable. page_count may return higher
117 * than expected, and put_page must be able to do the right thing when the
118 * page has been finished with, no matter what it is subsequently allocated
119 * for (because put_page is what is used here to drop an invalid speculative
122 * This is the interesting part of the lockless pagecache (and lockless
123 * get_user_pages) locking protocol, where the lookup-side (eg. find_get_page)
124 * has the following pattern:
125 * 1. find page in radix tree
126 * 2. conditionally increment refcount
127 * 3. check the page is still in pagecache (if no, goto 1)
129 * Remove-side that cares about stability of _count (eg. reclaim) has the
130 * following (with tree_lock held for write):
131 * A. atomically check refcount is correct and set it to 0 (atomic_cmpxchg)
132 * B. remove page from pagecache
135 * There are 2 critical interleavings that matter:
136 * - 2 runs before A: in this case, A sees elevated refcount and bails out
137 * - A runs before 2: in this case, 2 sees zero refcount and retries;
138 * subsequently, B will complete and 1 will find no page, causing the
139 * lookup to return NULL.
141 * It is possible that between 1 and 2, the page is removed then the exact same
142 * page is inserted into the same position in pagecache. That's OK: the
143 * old find_get_page using tree_lock could equally have run before or after
144 * such a re-insertion, depending on order that locks are granted.
146 * Lookups racing against pagecache insertion isn't a big problem: either 1
147 * will find the page or it will not. Likewise, the old find_get_page could run
148 * either before the insertion or afterwards, depending on timing.
150 static inline int page_cache_get_speculative(struct page *page)
152 VM_BUG_ON(in_interrupt());
154 #ifdef CONFIG_TINY_RCU
155 # ifdef CONFIG_PREEMPT_COUNT
156 VM_BUG_ON(!in_atomic());
159 * Preempt must be disabled here - we rely on rcu_read_lock doing
162 * Pagecache won't be truncated from interrupt context, so if we have
163 * found a page in the radix tree here, we have pinned its refcount by
164 * disabling preempt, and hence no need for the "speculative get" that
167 VM_BUG_ON_PAGE(page_count(page) == 0, page);
171 if (unlikely(!get_page_unless_zero(page))) {
173 * Either the page has been freed, or will be freed.
174 * In either case, retry here and the caller should
175 * do the right thing (see comments above).
180 VM_BUG_ON_PAGE(PageTail(page), page);
186 * Same as above, but add instead of inc (could just be merged)
188 static inline int page_cache_add_speculative(struct page *page, int count)
190 VM_BUG_ON(in_interrupt());
192 #if !defined(CONFIG_SMP) && defined(CONFIG_TREE_RCU)
193 # ifdef CONFIG_PREEMPT_COUNT
194 VM_BUG_ON(!in_atomic());
196 VM_BUG_ON_PAGE(page_count(page) == 0, page);
197 page_ref_add(page, count);
200 if (unlikely(!page_ref_add_unless(page, count, 0)))
203 VM_BUG_ON_PAGE(PageCompound(page) && page != compound_head(page), page);
209 extern struct page *__page_cache_alloc(gfp_t gfp);
211 static inline struct page *__page_cache_alloc(gfp_t gfp)
213 return alloc_pages(gfp, 0);
217 static inline struct page *page_cache_alloc(struct address_space *x)
219 return __page_cache_alloc(mapping_gfp_mask(x));
222 static inline struct page *page_cache_alloc_cold(struct address_space *x)
224 return __page_cache_alloc(mapping_gfp_mask(x)|__GFP_COLD);
227 static inline struct page *page_cache_alloc_readahead(struct address_space *x)
229 return __page_cache_alloc(mapping_gfp_mask(x) |
230 __GFP_COLD | __GFP_NORETRY | __GFP_NOWARN);
233 typedef int filler_t(void *, struct page *);
235 pgoff_t page_cache_next_hole(struct address_space *mapping,
236 pgoff_t index, unsigned long max_scan);
237 pgoff_t page_cache_prev_hole(struct address_space *mapping,
238 pgoff_t index, unsigned long max_scan);
240 #define FGP_ACCESSED 0x00000001
241 #define FGP_LOCK 0x00000002
242 #define FGP_CREAT 0x00000004
243 #define FGP_WRITE 0x00000008
244 #define FGP_NOFS 0x00000010
245 #define FGP_NOWAIT 0x00000020
247 struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
248 int fgp_flags, gfp_t cache_gfp_mask);
251 * find_get_page - find and get a page reference
252 * @mapping: the address_space to search
253 * @offset: the page index
255 * Looks up the page cache slot at @mapping & @offset. If there is a
256 * page cache page, it is returned with an increased refcount.
258 * Otherwise, %NULL is returned.
260 static inline struct page *find_get_page(struct address_space *mapping,
263 return pagecache_get_page(mapping, offset, 0, 0);
266 static inline struct page *find_get_page_flags(struct address_space *mapping,
267 pgoff_t offset, int fgp_flags)
269 return pagecache_get_page(mapping, offset, fgp_flags, 0);
273 * find_lock_page - locate, pin and lock a pagecache page
274 * pagecache_get_page - find and get a page reference
275 * @mapping: the address_space to search
276 * @offset: the page index
278 * Looks up the page cache slot at @mapping & @offset. If there is a
279 * page cache page, it is returned locked and with an increased
282 * Otherwise, %NULL is returned.
284 * find_lock_page() may sleep.
286 static inline struct page *find_lock_page(struct address_space *mapping,
289 return pagecache_get_page(mapping, offset, FGP_LOCK, 0);
293 * find_or_create_page - locate or add a pagecache page
294 * @mapping: the page's address_space
295 * @index: the page's index into the mapping
296 * @gfp_mask: page allocation mode
298 * Looks up the page cache slot at @mapping & @offset. If there is a
299 * page cache page, it is returned locked and with an increased
302 * If the page is not present, a new page is allocated using @gfp_mask
303 * and added to the page cache and the VM's LRU list. The page is
304 * returned locked and with an increased refcount.
306 * On memory exhaustion, %NULL is returned.
308 * find_or_create_page() may sleep, even if @gfp_flags specifies an
311 static inline struct page *find_or_create_page(struct address_space *mapping,
312 pgoff_t offset, gfp_t gfp_mask)
314 return pagecache_get_page(mapping, offset,
315 FGP_LOCK|FGP_ACCESSED|FGP_CREAT,
320 * grab_cache_page_nowait - returns locked page at given index in given cache
321 * @mapping: target address_space
322 * @index: the page index
324 * Same as grab_cache_page(), but do not wait if the page is unavailable.
325 * This is intended for speculative data generators, where the data can
326 * be regenerated if the page couldn't be grabbed. This routine should
327 * be safe to call while holding the lock for another page.
329 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
330 * and deadlock against the caller's locked page.
332 static inline struct page *grab_cache_page_nowait(struct address_space *mapping,
335 return pagecache_get_page(mapping, index,
336 FGP_LOCK|FGP_CREAT|FGP_NOFS|FGP_NOWAIT,
337 mapping_gfp_mask(mapping));
340 struct page *find_get_entry(struct address_space *mapping, pgoff_t offset);
341 struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset);
342 unsigned find_get_entries(struct address_space *mapping, pgoff_t start,
343 unsigned int nr_entries, struct page **entries,
345 unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
346 unsigned int nr_pages, struct page **pages);
347 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t start,
348 unsigned int nr_pages, struct page **pages);
349 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
350 int tag, unsigned int nr_pages, struct page **pages);
351 unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start,
352 int tag, unsigned int nr_entries,
353 struct page **entries, pgoff_t *indices);
355 struct page *grab_cache_page_write_begin(struct address_space *mapping,
356 pgoff_t index, unsigned flags);
359 * Returns locked page at given index in given cache, creating it if needed.
361 static inline struct page *grab_cache_page(struct address_space *mapping,
364 return find_or_create_page(mapping, index, mapping_gfp_mask(mapping));
367 extern struct page * read_cache_page(struct address_space *mapping,
368 pgoff_t index, filler_t *filler, void *data);
369 extern struct page * read_cache_page_gfp(struct address_space *mapping,
370 pgoff_t index, gfp_t gfp_mask);
371 extern int read_cache_pages(struct address_space *mapping,
372 struct list_head *pages, filler_t *filler, void *data);
374 static inline struct page *read_mapping_page(struct address_space *mapping,
375 pgoff_t index, void *data)
377 filler_t *filler = (filler_t *)mapping->a_ops->readpage;
378 return read_cache_page(mapping, index, filler, data);
382 * Get the offset in PAGE_SIZE.
383 * (TODO: hugepage should have ->index in PAGE_SIZE)
385 static inline pgoff_t page_to_pgoff(struct page *page)
389 if (unlikely(PageHeadHuge(page)))
390 return page->index << compound_order(page);
392 if (likely(!PageTransTail(page)))
393 return page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
396 * We don't initialize ->index for tail pages: calculate based on
399 pgoff = compound_head(page)->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
400 pgoff += page - compound_head(page);
405 * Return byte-offset into filesystem object for page.
407 static inline loff_t page_offset(struct page *page)
409 return ((loff_t)page->index) << PAGE_CACHE_SHIFT;
412 static inline loff_t page_file_offset(struct page *page)
414 return ((loff_t)page_file_index(page)) << PAGE_CACHE_SHIFT;
417 extern pgoff_t linear_hugepage_index(struct vm_area_struct *vma,
418 unsigned long address);
420 static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
421 unsigned long address)
424 if (unlikely(is_vm_hugetlb_page(vma)))
425 return linear_hugepage_index(vma, address);
426 pgoff = (address - vma->vm_start) >> PAGE_SHIFT;
427 pgoff += vma->vm_pgoff;
428 return pgoff >> (PAGE_CACHE_SHIFT - PAGE_SHIFT);
431 extern void __lock_page(struct page *page);
432 extern int __lock_page_killable(struct page *page);
433 extern int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
435 extern void unlock_page(struct page *page);
437 static inline int trylock_page(struct page *page)
439 page = compound_head(page);
440 return (likely(!test_and_set_bit_lock(PG_locked, &page->flags)));
444 * lock_page may only be called if we have the page's inode pinned.
446 static inline void lock_page(struct page *page)
449 if (!trylock_page(page))
454 * lock_page_killable is like lock_page but can be interrupted by fatal
455 * signals. It returns 0 if it locked the page and -EINTR if it was
456 * killed while waiting.
458 static inline int lock_page_killable(struct page *page)
461 if (!trylock_page(page))
462 return __lock_page_killable(page);
467 * lock_page_or_retry - Lock the page, unless this would block and the
468 * caller indicated that it can handle a retry.
470 * Return value and mmap_sem implications depend on flags; see
471 * __lock_page_or_retry().
473 static inline int lock_page_or_retry(struct page *page, struct mm_struct *mm,
477 return trylock_page(page) || __lock_page_or_retry(page, mm, flags);
481 * This is exported only for wait_on_page_locked/wait_on_page_writeback,
482 * and for filesystems which need to wait on PG_private.
484 extern void wait_on_page_bit(struct page *page, int bit_nr);
486 extern int wait_on_page_bit_killable(struct page *page, int bit_nr);
487 extern int wait_on_page_bit_killable_timeout(struct page *page,
488 int bit_nr, unsigned long timeout);
490 static inline int wait_on_page_locked_killable(struct page *page)
492 if (!PageLocked(page))
494 return wait_on_page_bit_killable(compound_head(page), PG_locked);
497 extern wait_queue_head_t *page_waitqueue(struct page *page);
498 static inline void wake_up_page(struct page *page, int bit)
500 __wake_up_bit(page_waitqueue(page), &page->flags, bit);
504 * Wait for a page to be unlocked.
506 * This must be called with the caller "holding" the page,
507 * ie with increased "page->count" so that the page won't
508 * go away during the wait..
510 static inline void wait_on_page_locked(struct page *page)
512 if (PageLocked(page))
513 wait_on_page_bit(compound_head(page), PG_locked);
517 * Wait for a page to complete writeback
519 static inline void wait_on_page_writeback(struct page *page)
521 if (PageWriteback(page))
522 wait_on_page_bit(page, PG_writeback);
525 extern void end_page_writeback(struct page *page);
526 void wait_for_stable_page(struct page *page);
528 void page_endio(struct page *page, int rw, int err);
531 * Add an arbitrary waiter to a page's wait queue
533 extern void add_page_wait_queue(struct page *page, wait_queue_t *waiter);
536 * Fault a userspace page into pagetables. Return non-zero on a fault.
538 * This assumes that two userspace pages are always sufficient. That's
539 * not true if PAGE_CACHE_SIZE > PAGE_SIZE.
541 static inline int fault_in_pages_writeable(char __user *uaddr, int size)
545 if (unlikely(size == 0))
549 * Writing zeroes into userspace here is OK, because we know that if
550 * the zero gets there, we'll be overwriting it.
552 ret = __put_user(0, uaddr);
554 char __user *end = uaddr + size - 1;
557 * If the page was already mapped, this will get a cache miss
558 * for sure, so try to avoid doing it.
560 if (((unsigned long)uaddr & PAGE_MASK) !=
561 ((unsigned long)end & PAGE_MASK))
562 ret = __put_user(0, end);
567 static inline int fault_in_pages_readable(const char __user *uaddr, int size)
572 if (unlikely(size == 0))
575 ret = __get_user(c, uaddr);
577 const char __user *end = uaddr + size - 1;
579 if (((unsigned long)uaddr & PAGE_MASK) !=
580 ((unsigned long)end & PAGE_MASK)) {
581 ret = __get_user(c, end);
589 * Multipage variants of the above prefault helpers, useful if more than
590 * PAGE_SIZE of data needs to be prefaulted. These are separate from the above
591 * functions (which only handle up to PAGE_SIZE) to avoid clobbering the
592 * filemap.c hotpaths.
594 static inline int fault_in_multipages_writeable(char __user *uaddr, int size)
597 char __user *end = uaddr + size - 1;
599 if (unlikely(size == 0))
603 * Writing zeroes into userspace here is OK, because we know that if
604 * the zero gets there, we'll be overwriting it.
606 while (uaddr <= end) {
607 ret = __put_user(0, uaddr);
613 /* Check whether the range spilled into the next page. */
614 if (((unsigned long)uaddr & PAGE_MASK) ==
615 ((unsigned long)end & PAGE_MASK))
616 ret = __put_user(0, end);
621 static inline int fault_in_multipages_readable(const char __user *uaddr,
626 const char __user *end = uaddr + size - 1;
628 if (unlikely(size == 0))
631 while (uaddr <= end) {
632 ret = __get_user(c, uaddr);
638 /* Check whether the range spilled into the next page. */
639 if (((unsigned long)uaddr & PAGE_MASK) ==
640 ((unsigned long)end & PAGE_MASK)) {
641 ret = __get_user(c, end);
648 int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
649 pgoff_t index, gfp_t gfp_mask);
650 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
651 pgoff_t index, gfp_t gfp_mask);
652 extern void delete_from_page_cache(struct page *page);
653 extern void __delete_from_page_cache(struct page *page, void *shadow);
654 int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask);
657 * Like add_to_page_cache_locked, but used to add newly allocated pages:
658 * the page is new, so we can just run __SetPageLocked() against it.
660 static inline int add_to_page_cache(struct page *page,
661 struct address_space *mapping, pgoff_t offset, gfp_t gfp_mask)
665 __SetPageLocked(page);
666 error = add_to_page_cache_locked(page, mapping, offset, gfp_mask);
668 __ClearPageLocked(page);
672 static inline unsigned long dir_pages(struct inode *inode)
674 return (unsigned long)(inode->i_size + PAGE_CACHE_SIZE - 1) >>
678 #endif /* _LINUX_PAGEMAP_H */