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1 #ifndef _LINUX_PAGEMAP_H
2 #define _LINUX_PAGEMAP_H
3
4 /*
5 * Copyright 1995 Linus Torvalds
6 */
7 #include <linux/mm.h>
8 #include <linux/fs.h>
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>
17
18 /*
19 * Bits in mapping->flags. The lower __GFP_BITS_SHIFT bits are the page
20 * allocation mode flags.
21 */
22 enum mapping_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 */
28 };
29
30 static inline void mapping_set_error(struct address_space *mapping, int error)
31 {
32 if (unlikely(error)) {
33 if (error == -ENOSPC)
34 set_bit(AS_ENOSPC, &mapping->flags);
35 else
36 set_bit(AS_EIO, &mapping->flags);
37 }
38 }
39
40 static inline void mapping_set_unevictable(struct address_space *mapping)
41 {
42 set_bit(AS_UNEVICTABLE, &mapping->flags);
43 }
44
45 static inline void mapping_clear_unevictable(struct address_space *mapping)
46 {
47 clear_bit(AS_UNEVICTABLE, &mapping->flags);
48 }
49
50 static inline int mapping_unevictable(struct address_space *mapping)
51 {
52 if (mapping)
53 return test_bit(AS_UNEVICTABLE, &mapping->flags);
54 return !!mapping;
55 }
56
57 static inline void mapping_set_exiting(struct address_space *mapping)
58 {
59 set_bit(AS_EXITING, &mapping->flags);
60 }
61
62 static inline int mapping_exiting(struct address_space *mapping)
63 {
64 return test_bit(AS_EXITING, &mapping->flags);
65 }
66
67 static inline gfp_t mapping_gfp_mask(struct address_space * mapping)
68 {
69 return (__force gfp_t)mapping->flags & __GFP_BITS_MASK;
70 }
71
72 /*
73 * This is non-atomic. Only to be used before the mapping is activated.
74 * Probably needs a barrier...
75 */
76 static inline void mapping_set_gfp_mask(struct address_space *m, gfp_t mask)
77 {
78 m->flags = (m->flags & ~(__force unsigned long)__GFP_BITS_MASK) |
79 (__force unsigned long)mask;
80 }
81
82 /*
83 * The page cache can be done in larger chunks than
84 * one page, because it allows for more efficient
85 * throughput (it can then be mapped into user
86 * space in smaller chunks for same flexibility).
87 *
88 * Or rather, it _will_ be done in larger chunks.
89 */
90 #define PAGE_CACHE_SHIFT PAGE_SHIFT
91 #define PAGE_CACHE_SIZE PAGE_SIZE
92 #define PAGE_CACHE_MASK PAGE_MASK
93 #define PAGE_CACHE_ALIGN(addr) (((addr)+PAGE_CACHE_SIZE-1)&PAGE_CACHE_MASK)
94
95 #define page_cache_get(page) get_page(page)
96 #define page_cache_release(page) put_page(page)
97 void release_pages(struct page **pages, int nr, bool cold);
98
99 /*
100 * speculatively take a reference to a page.
101 * If the page is free (_count == 0), then _count is untouched, and 0
102 * is returned. Otherwise, _count is incremented by 1 and 1 is returned.
103 *
104 * This function must be called inside the same rcu_read_lock() section as has
105 * been used to lookup the page in the pagecache radix-tree (or page table):
106 * this allows allocators to use a synchronize_rcu() to stabilize _count.
107 *
108 * Unless an RCU grace period has passed, the count of all pages coming out
109 * of the allocator must be considered unstable. page_count may return higher
110 * than expected, and put_page must be able to do the right thing when the
111 * page has been finished with, no matter what it is subsequently allocated
112 * for (because put_page is what is used here to drop an invalid speculative
113 * reference).
114 *
115 * This is the interesting part of the lockless pagecache (and lockless
116 * get_user_pages) locking protocol, where the lookup-side (eg. find_get_page)
117 * has the following pattern:
118 * 1. find page in radix tree
119 * 2. conditionally increment refcount
120 * 3. check the page is still in pagecache (if no, goto 1)
121 *
122 * Remove-side that cares about stability of _count (eg. reclaim) has the
123 * following (with tree_lock held for write):
124 * A. atomically check refcount is correct and set it to 0 (atomic_cmpxchg)
125 * B. remove page from pagecache
126 * C. free the page
127 *
128 * There are 2 critical interleavings that matter:
129 * - 2 runs before A: in this case, A sees elevated refcount and bails out
130 * - A runs before 2: in this case, 2 sees zero refcount and retries;
131 * subsequently, B will complete and 1 will find no page, causing the
132 * lookup to return NULL.
133 *
134 * It is possible that between 1 and 2, the page is removed then the exact same
135 * page is inserted into the same position in pagecache. That's OK: the
136 * old find_get_page using tree_lock could equally have run before or after
137 * such a re-insertion, depending on order that locks are granted.
138 *
139 * Lookups racing against pagecache insertion isn't a big problem: either 1
140 * will find the page or it will not. Likewise, the old find_get_page could run
141 * either before the insertion or afterwards, depending on timing.
142 */
143 static inline int page_cache_get_speculative(struct page *page)
144 {
145 VM_BUG_ON(in_interrupt());
146
147 #ifdef CONFIG_TINY_RCU
148 # ifdef CONFIG_PREEMPT_COUNT
149 VM_BUG_ON(!in_atomic());
150 # endif
151 /*
152 * Preempt must be disabled here - we rely on rcu_read_lock doing
153 * this for us.
154 *
155 * Pagecache won't be truncated from interrupt context, so if we have
156 * found a page in the radix tree here, we have pinned its refcount by
157 * disabling preempt, and hence no need for the "speculative get" that
158 * SMP requires.
159 */
160 VM_BUG_ON_PAGE(page_count(page) == 0, page);
161 atomic_inc(&page->_count);
162
163 #else
164 if (unlikely(!get_page_unless_zero(page))) {
165 /*
166 * Either the page has been freed, or will be freed.
167 * In either case, retry here and the caller should
168 * do the right thing (see comments above).
169 */
170 return 0;
171 }
172 #endif
173 VM_BUG_ON_PAGE(PageTail(page), page);
174
175 return 1;
176 }
177
178 /*
179 * Same as above, but add instead of inc (could just be merged)
180 */
181 static inline int page_cache_add_speculative(struct page *page, int count)
182 {
183 VM_BUG_ON(in_interrupt());
184
185 #if !defined(CONFIG_SMP) && defined(CONFIG_TREE_RCU)
186 # ifdef CONFIG_PREEMPT_COUNT
187 VM_BUG_ON(!in_atomic());
188 # endif
189 VM_BUG_ON_PAGE(page_count(page) == 0, page);
190 atomic_add(count, &page->_count);
191
192 #else
193 if (unlikely(!atomic_add_unless(&page->_count, count, 0)))
194 return 0;
195 #endif
196 VM_BUG_ON_PAGE(PageCompound(page) && page != compound_head(page), page);
197
198 return 1;
199 }
200
201 static inline int page_freeze_refs(struct page *page, int count)
202 {
203 return likely(atomic_cmpxchg(&page->_count, count, 0) == count);
204 }
205
206 static inline void page_unfreeze_refs(struct page *page, int count)
207 {
208 VM_BUG_ON_PAGE(page_count(page) != 0, page);
209 VM_BUG_ON(count == 0);
210
211 atomic_set(&page->_count, count);
212 }
213
214 #ifdef CONFIG_NUMA
215 extern struct page *__page_cache_alloc(gfp_t gfp);
216 #else
217 static inline struct page *__page_cache_alloc(gfp_t gfp)
218 {
219 return alloc_pages(gfp, 0);
220 }
221 #endif
222
223 static inline struct page *page_cache_alloc(struct address_space *x)
224 {
225 return __page_cache_alloc(mapping_gfp_mask(x));
226 }
227
228 static inline struct page *page_cache_alloc_cold(struct address_space *x)
229 {
230 return __page_cache_alloc(mapping_gfp_mask(x)|__GFP_COLD);
231 }
232
233 static inline struct page *page_cache_alloc_readahead(struct address_space *x)
234 {
235 return __page_cache_alloc(mapping_gfp_mask(x) |
236 __GFP_COLD | __GFP_NORETRY | __GFP_NOWARN);
237 }
238
239 typedef int filler_t(void *, struct page *);
240
241 pgoff_t page_cache_next_hole(struct address_space *mapping,
242 pgoff_t index, unsigned long max_scan);
243 pgoff_t page_cache_prev_hole(struct address_space *mapping,
244 pgoff_t index, unsigned long max_scan);
245
246 #define FGP_ACCESSED 0x00000001
247 #define FGP_LOCK 0x00000002
248 #define FGP_CREAT 0x00000004
249 #define FGP_WRITE 0x00000008
250 #define FGP_NOFS 0x00000010
251 #define FGP_NOWAIT 0x00000020
252
253 struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
254 int fgp_flags, gfp_t cache_gfp_mask);
255
256 /**
257 * find_get_page - find and get a page reference
258 * @mapping: the address_space to search
259 * @offset: the page index
260 *
261 * Looks up the page cache slot at @mapping & @offset. If there is a
262 * page cache page, it is returned with an increased refcount.
263 *
264 * Otherwise, %NULL is returned.
265 */
266 static inline struct page *find_get_page(struct address_space *mapping,
267 pgoff_t offset)
268 {
269 return pagecache_get_page(mapping, offset, 0, 0);
270 }
271
272 static inline struct page *find_get_page_flags(struct address_space *mapping,
273 pgoff_t offset, int fgp_flags)
274 {
275 return pagecache_get_page(mapping, offset, fgp_flags, 0);
276 }
277
278 /**
279 * find_lock_page - locate, pin and lock a pagecache page
280 * pagecache_get_page - find and get a page reference
281 * @mapping: the address_space to search
282 * @offset: the page index
283 *
284 * Looks up the page cache slot at @mapping & @offset. If there is a
285 * page cache page, it is returned locked and with an increased
286 * refcount.
287 *
288 * Otherwise, %NULL is returned.
289 *
290 * find_lock_page() may sleep.
291 */
292 static inline struct page *find_lock_page(struct address_space *mapping,
293 pgoff_t offset)
294 {
295 return pagecache_get_page(mapping, offset, FGP_LOCK, 0);
296 }
297
298 /**
299 * find_or_create_page - locate or add a pagecache page
300 * @mapping: the page's address_space
301 * @index: the page's index into the mapping
302 * @gfp_mask: page allocation mode
303 *
304 * Looks up the page cache slot at @mapping & @offset. If there is a
305 * page cache page, it is returned locked and with an increased
306 * refcount.
307 *
308 * If the page is not present, a new page is allocated using @gfp_mask
309 * and added to the page cache and the VM's LRU list. The page is
310 * returned locked and with an increased refcount.
311 *
312 * On memory exhaustion, %NULL is returned.
313 *
314 * find_or_create_page() may sleep, even if @gfp_flags specifies an
315 * atomic allocation!
316 */
317 static inline struct page *find_or_create_page(struct address_space *mapping,
318 pgoff_t offset, gfp_t gfp_mask)
319 {
320 return pagecache_get_page(mapping, offset,
321 FGP_LOCK|FGP_ACCESSED|FGP_CREAT,
322 gfp_mask);
323 }
324
325 /**
326 * grab_cache_page_nowait - returns locked page at given index in given cache
327 * @mapping: target address_space
328 * @index: the page index
329 *
330 * Same as grab_cache_page(), but do not wait if the page is unavailable.
331 * This is intended for speculative data generators, where the data can
332 * be regenerated if the page couldn't be grabbed. This routine should
333 * be safe to call while holding the lock for another page.
334 *
335 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
336 * and deadlock against the caller's locked page.
337 */
338 static inline struct page *grab_cache_page_nowait(struct address_space *mapping,
339 pgoff_t index)
340 {
341 return pagecache_get_page(mapping, index,
342 FGP_LOCK|FGP_CREAT|FGP_NOFS|FGP_NOWAIT,
343 mapping_gfp_mask(mapping));
344 }
345
346 struct page *find_get_entry(struct address_space *mapping, pgoff_t offset);
347 struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset);
348 unsigned find_get_entries(struct address_space *mapping, pgoff_t start,
349 unsigned int nr_entries, struct page **entries,
350 pgoff_t *indices);
351 unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
352 unsigned int nr_pages, struct page **pages);
353 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t start,
354 unsigned int nr_pages, struct page **pages);
355 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
356 int tag, unsigned int nr_pages, struct page **pages);
357
358 struct page *grab_cache_page_write_begin(struct address_space *mapping,
359 pgoff_t index, unsigned flags);
360
361 /*
362 * Returns locked page at given index in given cache, creating it if needed.
363 */
364 static inline struct page *grab_cache_page(struct address_space *mapping,
365 pgoff_t index)
366 {
367 return find_or_create_page(mapping, index, mapping_gfp_mask(mapping));
368 }
369
370 extern struct page * read_cache_page(struct address_space *mapping,
371 pgoff_t index, filler_t *filler, void *data);
372 extern struct page * read_cache_page_gfp(struct address_space *mapping,
373 pgoff_t index, gfp_t gfp_mask);
374 extern int read_cache_pages(struct address_space *mapping,
375 struct list_head *pages, filler_t *filler, void *data);
376
377 static inline struct page *read_mapping_page(struct address_space *mapping,
378 pgoff_t index, void *data)
379 {
380 filler_t *filler = (filler_t *)mapping->a_ops->readpage;
381 return read_cache_page(mapping, index, filler, data);
382 }
383
384 /*
385 * Get the offset in PAGE_SIZE.
386 * (TODO: hugepage should have ->index in PAGE_SIZE)
387 */
388 static inline pgoff_t page_to_pgoff(struct page *page)
389 {
390 if (unlikely(PageHeadHuge(page)))
391 return page->index << compound_order(page);
392 else
393 return page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
394 }
395
396 /*
397 * Return byte-offset into filesystem object for page.
398 */
399 static inline loff_t page_offset(struct page *page)
400 {
401 return ((loff_t)page->index) << PAGE_CACHE_SHIFT;
402 }
403
404 static inline loff_t page_file_offset(struct page *page)
405 {
406 return ((loff_t)page_file_index(page)) << PAGE_CACHE_SHIFT;
407 }
408
409 extern pgoff_t linear_hugepage_index(struct vm_area_struct *vma,
410 unsigned long address);
411
412 static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
413 unsigned long address)
414 {
415 pgoff_t pgoff;
416 if (unlikely(is_vm_hugetlb_page(vma)))
417 return linear_hugepage_index(vma, address);
418 pgoff = (address - vma->vm_start) >> PAGE_SHIFT;
419 pgoff += vma->vm_pgoff;
420 return pgoff >> (PAGE_CACHE_SHIFT - PAGE_SHIFT);
421 }
422
423 extern void __lock_page(struct page *page);
424 extern int __lock_page_killable(struct page *page);
425 extern int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
426 unsigned int flags);
427 extern void unlock_page(struct page *page);
428
429 static inline void __set_page_locked(struct page *page)
430 {
431 __set_bit(PG_locked, &page->flags);
432 }
433
434 static inline void __clear_page_locked(struct page *page)
435 {
436 __clear_bit(PG_locked, &page->flags);
437 }
438
439 static inline int trylock_page(struct page *page)
440 {
441 return (likely(!test_and_set_bit_lock(PG_locked, &page->flags)));
442 }
443
444 /*
445 * lock_page may only be called if we have the page's inode pinned.
446 */
447 static inline void lock_page(struct page *page)
448 {
449 might_sleep();
450 if (!trylock_page(page))
451 __lock_page(page);
452 }
453
454 /*
455 * lock_page_killable is like lock_page but can be interrupted by fatal
456 * signals. It returns 0 if it locked the page and -EINTR if it was
457 * killed while waiting.
458 */
459 static inline int lock_page_killable(struct page *page)
460 {
461 might_sleep();
462 if (!trylock_page(page))
463 return __lock_page_killable(page);
464 return 0;
465 }
466
467 /*
468 * lock_page_or_retry - Lock the page, unless this would block and the
469 * caller indicated that it can handle a retry.
470 *
471 * Return value and mmap_sem implications depend on flags; see
472 * __lock_page_or_retry().
473 */
474 static inline int lock_page_or_retry(struct page *page, struct mm_struct *mm,
475 unsigned int flags)
476 {
477 might_sleep();
478 return trylock_page(page) || __lock_page_or_retry(page, mm, flags);
479 }
480
481 /*
482 * This is exported only for wait_on_page_locked/wait_on_page_writeback,
483 * and for filesystems which need to wait on PG_private.
484 */
485 extern void wait_on_page_bit(struct page *page, int bit_nr);
486
487 extern int wait_on_page_bit_killable(struct page *page, int bit_nr);
488 extern int wait_on_page_bit_killable_timeout(struct page *page,
489 int bit_nr, unsigned long timeout);
490
491 static inline int wait_on_page_locked_killable(struct page *page)
492 {
493 if (PageLocked(page))
494 return wait_on_page_bit_killable(page, PG_locked);
495 return 0;
496 }
497
498 extern wait_queue_head_t *page_waitqueue(struct page *page);
499 static inline void wake_up_page(struct page *page, int bit)
500 {
501 __wake_up_bit(page_waitqueue(page), &page->flags, bit);
502 }
503
504 /*
505 * Wait for a page to be unlocked.
506 *
507 * This must be called with the caller "holding" the page,
508 * ie with increased "page->count" so that the page won't
509 * go away during the wait..
510 */
511 static inline void wait_on_page_locked(struct page *page)
512 {
513 if (PageLocked(page))
514 wait_on_page_bit(page, PG_locked);
515 }
516
517 /*
518 * Wait for a page to complete writeback
519 */
520 static inline void wait_on_page_writeback(struct page *page)
521 {
522 if (PageWriteback(page))
523 wait_on_page_bit(page, PG_writeback);
524 }
525
526 extern void end_page_writeback(struct page *page);
527 void wait_for_stable_page(struct page *page);
528
529 void page_endio(struct page *page, int rw, int err);
530
531 /*
532 * Add an arbitrary waiter to a page's wait queue
533 */
534 extern void add_page_wait_queue(struct page *page, wait_queue_t *waiter);
535
536 /*
537 * Fault a userspace page into pagetables. Return non-zero on a fault.
538 *
539 * This assumes that two userspace pages are always sufficient. That's
540 * not true if PAGE_CACHE_SIZE > PAGE_SIZE.
541 */
542 static inline int fault_in_pages_writeable(char __user *uaddr, int size)
543 {
544 int ret;
545
546 if (unlikely(size == 0))
547 return 0;
548
549 /*
550 * Writing zeroes into userspace here is OK, because we know that if
551 * the zero gets there, we'll be overwriting it.
552 */
553 ret = __put_user(0, uaddr);
554 if (ret == 0) {
555 char __user *end = uaddr + size - 1;
556
557 /*
558 * If the page was already mapped, this will get a cache miss
559 * for sure, so try to avoid doing it.
560 */
561 if (((unsigned long)uaddr & PAGE_MASK) !=
562 ((unsigned long)end & PAGE_MASK))
563 ret = __put_user(0, end);
564 }
565 return ret;
566 }
567
568 static inline int fault_in_pages_readable(const char __user *uaddr, int size)
569 {
570 volatile char c;
571 int ret;
572
573 if (unlikely(size == 0))
574 return 0;
575
576 ret = __get_user(c, uaddr);
577 if (ret == 0) {
578 const char __user *end = uaddr + size - 1;
579
580 if (((unsigned long)uaddr & PAGE_MASK) !=
581 ((unsigned long)end & PAGE_MASK)) {
582 ret = __get_user(c, end);
583 (void)c;
584 }
585 }
586 return ret;
587 }
588
589 /*
590 * Multipage variants of the above prefault helpers, useful if more than
591 * PAGE_SIZE of data needs to be prefaulted. These are separate from the above
592 * functions (which only handle up to PAGE_SIZE) to avoid clobbering the
593 * filemap.c hotpaths.
594 */
595 static inline int fault_in_multipages_writeable(char __user *uaddr, int size)
596 {
597 int ret = 0;
598 char __user *end = uaddr + size - 1;
599
600 if (unlikely(size == 0))
601 return ret;
602
603 /*
604 * Writing zeroes into userspace here is OK, because we know that if
605 * the zero gets there, we'll be overwriting it.
606 */
607 while (uaddr <= end) {
608 ret = __put_user(0, uaddr);
609 if (ret != 0)
610 return ret;
611 uaddr += PAGE_SIZE;
612 }
613
614 /* Check whether the range spilled into the next page. */
615 if (((unsigned long)uaddr & PAGE_MASK) ==
616 ((unsigned long)end & PAGE_MASK))
617 ret = __put_user(0, end);
618
619 return ret;
620 }
621
622 static inline int fault_in_multipages_readable(const char __user *uaddr,
623 int size)
624 {
625 volatile char c;
626 int ret = 0;
627 const char __user *end = uaddr + size - 1;
628
629 if (unlikely(size == 0))
630 return ret;
631
632 while (uaddr <= end) {
633 ret = __get_user(c, uaddr);
634 if (ret != 0)
635 return ret;
636 uaddr += PAGE_SIZE;
637 }
638
639 /* Check whether the range spilled into the next page. */
640 if (((unsigned long)uaddr & PAGE_MASK) ==
641 ((unsigned long)end & PAGE_MASK)) {
642 ret = __get_user(c, end);
643 (void)c;
644 }
645
646 return ret;
647 }
648
649 int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
650 pgoff_t index, gfp_t gfp_mask);
651 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
652 pgoff_t index, gfp_t gfp_mask);
653 extern void delete_from_page_cache(struct page *page);
654 extern void __delete_from_page_cache(struct page *page, void *shadow);
655 int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask);
656
657 /*
658 * Like add_to_page_cache_locked, but used to add newly allocated pages:
659 * the page is new, so we can just run __set_page_locked() against it.
660 */
661 static inline int add_to_page_cache(struct page *page,
662 struct address_space *mapping, pgoff_t offset, gfp_t gfp_mask)
663 {
664 int error;
665
666 __set_page_locked(page);
667 error = add_to_page_cache_locked(page, mapping, offset, gfp_mask);
668 if (unlikely(error))
669 __clear_page_locked(page);
670 return error;
671 }
672
673 #endif /* _LINUX_PAGEMAP_H */