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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, int 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 extern struct page * find_get_page(struct address_space *mapping,
247                                 pgoff_t index);
248 extern struct page * find_lock_page(struct address_space *mapping,
249                                 pgoff_t index);
250 extern struct page * find_or_create_page(struct address_space *mapping,
251                                 pgoff_t index, gfp_t gfp_mask);
252 unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
253                         unsigned int nr_pages, struct page **pages);
254 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t start,
255                                unsigned int nr_pages, struct page **pages);
256 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
257                         int tag, unsigned int nr_pages, struct page **pages);
258 
259 struct page *grab_cache_page_write_begin(struct address_space *mapping,
260                         pgoff_t index, unsigned flags);
261 
262 /*
263  * Returns locked page at given index in given cache, creating it if needed.
264  */
265 static inline struct page *grab_cache_page(struct address_space *mapping,
266                                                                 pgoff_t index)
267 {
268         return find_or_create_page(mapping, index, mapping_gfp_mask(mapping));
269 }
270 
271 extern struct page * grab_cache_page_nowait(struct address_space *mapping,
272                                 pgoff_t index);
273 extern struct page * read_cache_page_async(struct address_space *mapping,
274                                 pgoff_t index, filler_t *filler, void *data);
275 extern struct page * read_cache_page(struct address_space *mapping,
276                                 pgoff_t index, filler_t *filler, void *data);
277 extern struct page * read_cache_page_gfp(struct address_space *mapping,
278                                 pgoff_t index, gfp_t gfp_mask);
279 extern int read_cache_pages(struct address_space *mapping,
280                 struct list_head *pages, filler_t *filler, void *data);
281 
282 static inline struct page *read_mapping_page_async(
283                                 struct address_space *mapping,
284                                 pgoff_t index, void *data)
285 {
286         filler_t *filler = (filler_t *)mapping->a_ops->readpage;
287         return read_cache_page_async(mapping, index, filler, data);
288 }
289 
290 static inline struct page *read_mapping_page(struct address_space *mapping,
291                                 pgoff_t index, void *data)
292 {
293         filler_t *filler = (filler_t *)mapping->a_ops->readpage;
294         return read_cache_page(mapping, index, filler, data);
295 }
296 
297 /*
298  * Return byte-offset into filesystem object for page.
299  */
300 static inline loff_t page_offset(struct page *page)
301 {
302         return ((loff_t)page->index) << PAGE_CACHE_SHIFT;
303 }
304 
305 static inline loff_t page_file_offset(struct page *page)
306 {
307         return ((loff_t)page_file_index(page)) << PAGE_CACHE_SHIFT;
308 }
309 
310 extern pgoff_t linear_hugepage_index(struct vm_area_struct *vma,
311                                      unsigned long address);
312 
313 static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
314                                         unsigned long address)
315 {
316         pgoff_t pgoff;
317         if (unlikely(is_vm_hugetlb_page(vma)))
318                 return linear_hugepage_index(vma, address);
319         pgoff = (address - vma->vm_start) >> PAGE_SHIFT;
320         pgoff += vma->vm_pgoff;
321         return pgoff >> (PAGE_CACHE_SHIFT - PAGE_SHIFT);
322 }
323 
324 extern void __lock_page(struct page *page);
325 extern int __lock_page_killable(struct page *page);
326 extern int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
327                                 unsigned int flags);
328 extern void unlock_page(struct page *page);
329 
330 static inline void __set_page_locked(struct page *page)
331 {
332         __set_bit(PG_locked, &page->flags);
333 }
334 
335 static inline void __clear_page_locked(struct page *page)
336 {
337         __clear_bit(PG_locked, &page->flags);
338 }
339 
340 static inline int trylock_page(struct page *page)
341 {
342         return (likely(!test_and_set_bit_lock(PG_locked, &page->flags)));
343 }
344 
345 /*
346  * lock_page may only be called if we have the page's inode pinned.
347  */
348 static inline void lock_page(struct page *page)
349 {
350         might_sleep();
351         if (!trylock_page(page))
352                 __lock_page(page);
353 }
354 
355 /*
356  * lock_page_killable is like lock_page but can be interrupted by fatal
357  * signals.  It returns 0 if it locked the page and -EINTR if it was
358  * killed while waiting.
359  */
360 static inline int lock_page_killable(struct page *page)
361 {
362         might_sleep();
363         if (!trylock_page(page))
364                 return __lock_page_killable(page);
365         return 0;
366 }
367 
368 /*
369  * lock_page_or_retry - Lock the page, unless this would block and the
370  * caller indicated that it can handle a retry.
371  */
372 static inline int lock_page_or_retry(struct page *page, struct mm_struct *mm,
373                                      unsigned int flags)
374 {
375         might_sleep();
376         return trylock_page(page) || __lock_page_or_retry(page, mm, flags);
377 }
378 
379 /*
380  * This is exported only for wait_on_page_locked/wait_on_page_writeback.
381  * Never use this directly!
382  */
383 extern void wait_on_page_bit(struct page *page, int bit_nr);
384 
385 extern int wait_on_page_bit_killable(struct page *page, int bit_nr);
386 
387 static inline int wait_on_page_locked_killable(struct page *page)
388 {
389         if (PageLocked(page))
390                 return wait_on_page_bit_killable(page, PG_locked);
391         return 0;
392 }
393 
394 /* 
395  * Wait for a page to be unlocked.
396  *
397  * This must be called with the caller "holding" the page,
398  * ie with increased "page->count" so that the page won't
399  * go away during the wait..
400  */
401 static inline void wait_on_page_locked(struct page *page)
402 {
403         if (PageLocked(page))
404                 wait_on_page_bit(page, PG_locked);
405 }
406 
407 /* 
408  * Wait for a page to complete writeback
409  */
410 static inline void wait_on_page_writeback(struct page *page)
411 {
412         if (PageWriteback(page))
413                 wait_on_page_bit(page, PG_writeback);
414 }
415 
416 extern void end_page_writeback(struct page *page);
417 void wait_for_stable_page(struct page *page);
418 
419 /*
420  * Add an arbitrary waiter to a page's wait queue
421  */
422 extern void add_page_wait_queue(struct page *page, wait_queue_t *waiter);
423 
424 /*
425  * Fault a userspace page into pagetables.  Return non-zero on a fault.
426  *
427  * This assumes that two userspace pages are always sufficient.  That's
428  * not true if PAGE_CACHE_SIZE > PAGE_SIZE.
429  */
430 static inline int fault_in_pages_writeable(char __user *uaddr, int size)
431 {
432         int ret;
433 
434         if (unlikely(size == 0))
435                 return 0;
436 
437         /*
438          * Writing zeroes into userspace here is OK, because we know that if
439          * the zero gets there, we'll be overwriting it.
440          */
441         ret = __put_user(0, uaddr);
442         if (ret == 0) {
443                 char __user *end = uaddr + size - 1;
444 
445                 /*
446                  * If the page was already mapped, this will get a cache miss
447                  * for sure, so try to avoid doing it.
448                  */
449                 if (((unsigned long)uaddr & PAGE_MASK) !=
450                                 ((unsigned long)end & PAGE_MASK))
451                         ret = __put_user(0, end);
452         }
453         return ret;
454 }
455 
456 static inline int fault_in_pages_readable(const char __user *uaddr, int size)
457 {
458         volatile char c;
459         int ret;
460 
461         if (unlikely(size == 0))
462                 return 0;
463 
464         ret = __get_user(c, uaddr);
465         if (ret == 0) {
466                 const char __user *end = uaddr + size - 1;
467 
468                 if (((unsigned long)uaddr & PAGE_MASK) !=
469                                 ((unsigned long)end & PAGE_MASK)) {
470                         ret = __get_user(c, end);
471                         (void)c;
472                 }
473         }
474         return ret;
475 }
476 
477 /*
478  * Multipage variants of the above prefault helpers, useful if more than
479  * PAGE_SIZE of data needs to be prefaulted. These are separate from the above
480  * functions (which only handle up to PAGE_SIZE) to avoid clobbering the
481  * filemap.c hotpaths.
482  */
483 static inline int fault_in_multipages_writeable(char __user *uaddr, int size)
484 {
485         int ret = 0;
486         char __user *end = uaddr + size - 1;
487 
488         if (unlikely(size == 0))
489                 return ret;
490 
491         /*
492          * Writing zeroes into userspace here is OK, because we know that if
493          * the zero gets there, we'll be overwriting it.
494          */
495         while (uaddr <= end) {
496                 ret = __put_user(0, uaddr);
497                 if (ret != 0)
498                         return ret;
499                 uaddr += PAGE_SIZE;
500         }
501 
502         /* Check whether the range spilled into the next page. */
503         if (((unsigned long)uaddr & PAGE_MASK) ==
504                         ((unsigned long)end & PAGE_MASK))
505                 ret = __put_user(0, end);
506 
507         return ret;
508 }
509 
510 static inline int fault_in_multipages_readable(const char __user *uaddr,
511                                                int size)
512 {
513         volatile char c;
514         int ret = 0;
515         const char __user *end = uaddr + size - 1;
516 
517         if (unlikely(size == 0))
518                 return ret;
519 
520         while (uaddr <= end) {
521                 ret = __get_user(c, uaddr);
522                 if (ret != 0)
523                         return ret;
524                 uaddr += PAGE_SIZE;
525         }
526 
527         /* Check whether the range spilled into the next page. */
528         if (((unsigned long)uaddr & PAGE_MASK) ==
529                         ((unsigned long)end & PAGE_MASK)) {
530                 ret = __get_user(c, end);
531                 (void)c;
532         }
533 
534         return ret;
535 }
536 
537 int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
538                                 pgoff_t index, gfp_t gfp_mask);
539 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
540                                 pgoff_t index, gfp_t gfp_mask);
541 extern void delete_from_page_cache(struct page *page);
542 extern void __delete_from_page_cache(struct page *page);
543 int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask);
544 
545 /*
546  * Like add_to_page_cache_locked, but used to add newly allocated pages:
547  * the page is new, so we can just run __set_page_locked() against it.
548  */
549 static inline int add_to_page_cache(struct page *page,
550                 struct address_space *mapping, pgoff_t offset, gfp_t gfp_mask)
551 {
552         int error;
553 
554         __set_page_locked(page);
555         error = add_to_page_cache_locked(page, mapping, offset, gfp_mask);
556         if (unlikely(error))
557                 __clear_page_locked(page);
558         return error;
559 }
560 
561 #endif /* _LINUX_PAGEMAP_H */
562 

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