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TOMOYO Linux Cross Reference
Linux/include/linux/pagemap.h

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

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