Line data Source code
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 :
17 : /*
18 : * Bits in mapping->flags. The lower __GFP_BITS_SHIFT bits are the page
19 : * allocation mode flags.
20 : */
21 : enum mapping_flags {
22 : AS_EIO = __GFP_BITS_SHIFT + 0, /* IO error on async write */
23 : AS_ENOSPC = __GFP_BITS_SHIFT + 1, /* ENOSPC on async write */
24 : AS_MM_ALL_LOCKS = __GFP_BITS_SHIFT + 2, /* under mm_take_all_locks() */
25 : AS_UNEVICTABLE = __GFP_BITS_SHIFT + 3, /* e.g., ramdisk, SHM_LOCK */
26 : };
27 :
28 : static inline void mapping_set_error(struct address_space *mapping, int error)
29 : {
30 : if (unlikely(error)) {
31 : if (error == -ENOSPC)
32 : set_bit(AS_ENOSPC, &mapping->flags);
33 : else
34 : set_bit(AS_EIO, &mapping->flags);
35 : }
36 : }
37 :
38 : static inline void mapping_set_unevictable(struct address_space *mapping)
39 : {
40 : set_bit(AS_UNEVICTABLE, &mapping->flags);
41 : }
42 :
43 : static inline void mapping_clear_unevictable(struct address_space *mapping)
44 : {
45 : clear_bit(AS_UNEVICTABLE, &mapping->flags);
46 : }
47 :
48 : static inline int mapping_unevictable(struct address_space *mapping)
49 : {
50 : if (likely(mapping))
51 : return test_bit(AS_UNEVICTABLE, &mapping->flags);
52 : return !!mapping;
53 : }
54 :
55 : static inline gfp_t mapping_gfp_mask(struct address_space * mapping)
56 : {
57 : return (__force gfp_t)mapping->flags & __GFP_BITS_MASK;
58 : }
59 :
60 : /*
61 : * This is non-atomic. Only to be used before the mapping is activated.
62 : * Probably needs a barrier...
63 : */
64 : static inline void mapping_set_gfp_mask(struct address_space *m, gfp_t mask)
65 : {
66 : m->flags = (m->flags & ~(__force unsigned long)__GFP_BITS_MASK) |
67 : (__force unsigned long)mask;
68 : }
69 :
70 : /*
71 : * The page cache can done in larger chunks than
72 : * one page, because it allows for more efficient
73 : * throughput (it can then be mapped into user
74 : * space in smaller chunks for same flexibility).
75 : *
76 : * Or rather, it _will_ be done in larger chunks.
77 : */
78 : #define PAGE_CACHE_SHIFT PAGE_SHIFT
79 : #define PAGE_CACHE_SIZE PAGE_SIZE
80 : #define PAGE_CACHE_MASK PAGE_MASK
81 : #define PAGE_CACHE_ALIGN(addr) (((addr)+PAGE_CACHE_SIZE-1)&PAGE_CACHE_MASK)
82 :
83 : #define page_cache_get(page) get_page(page)
84 : #define page_cache_release(page) put_page(page)
85 : void release_pages(struct page **pages, int nr, int cold);
86 :
87 : /*
88 : * speculatively take a reference to a page.
89 : * If the page is free (_count == 0), then _count is untouched, and 0
90 : * is returned. Otherwise, _count is incremented by 1 and 1 is returned.
91 : *
92 : * This function must be called inside the same rcu_read_lock() section as has
93 : * been used to lookup the page in the pagecache radix-tree (or page table):
94 : * this allows allocators to use a synchronize_rcu() to stabilize _count.
95 : *
96 : * Unless an RCU grace period has passed, the count of all pages coming out
97 : * of the allocator must be considered unstable. page_count may return higher
98 : * than expected, and put_page must be able to do the right thing when the
99 : * page has been finished with, no matter what it is subsequently allocated
100 : * for (because put_page is what is used here to drop an invalid speculative
101 : * reference).
102 : *
103 : * This is the interesting part of the lockless pagecache (and lockless
104 : * get_user_pages) locking protocol, where the lookup-side (eg. find_get_page)
105 : * has the following pattern:
106 : * 1. find page in radix tree
107 : * 2. conditionally increment refcount
108 : * 3. check the page is still in pagecache (if no, goto 1)
109 : *
110 : * Remove-side that cares about stability of _count (eg. reclaim) has the
111 : * following (with tree_lock held for write):
112 : * A. atomically check refcount is correct and set it to 0 (atomic_cmpxchg)
113 : * B. remove page from pagecache
114 : * C. free the page
115 : *
116 : * There are 2 critical interleavings that matter:
117 : * - 2 runs before A: in this case, A sees elevated refcount and bails out
118 : * - A runs before 2: in this case, 2 sees zero refcount and retries;
119 : * subsequently, B will complete and 1 will find no page, causing the
120 : * lookup to return NULL.
121 : *
122 : * It is possible that between 1 and 2, the page is removed then the exact same
123 : * page is inserted into the same position in pagecache. That's OK: the
124 : * old find_get_page using tree_lock could equally have run before or after
125 : * such a re-insertion, depending on order that locks are granted.
126 : *
127 : * Lookups racing against pagecache insertion isn't a big problem: either 1
128 : * will find the page or it will not. Likewise, the old find_get_page could run
129 : * either before the insertion or afterwards, depending on timing.
130 : */
131 : static inline int page_cache_get_speculative(struct page *page)
132 : {
133 : VM_BUG_ON(in_interrupt());
134 :
135 : #if !defined(CONFIG_SMP) && defined(CONFIG_TREE_RCU)
136 : # ifdef CONFIG_PREEMPT
137 : VM_BUG_ON(!in_atomic());
138 : # endif
139 : /*
140 : * Preempt must be disabled here - we rely on rcu_read_lock doing
141 : * this for us.
142 : *
143 : * Pagecache won't be truncated from interrupt context, so if we have
144 : * found a page in the radix tree here, we have pinned its refcount by
145 : * disabling preempt, and hence no need for the "speculative get" that
146 : * SMP requires.
147 : */
148 : VM_BUG_ON(page_count(page) == 0);
149 : atomic_inc(&page->_count);
150 :
151 : #else
152 : if (unlikely(!get_page_unless_zero(page))) {
153 : /*
154 : * Either the page has been freed, or will be freed.
155 : * In either case, retry here and the caller should
156 : * do the right thing (see comments above).
157 : */
158 : return 0;
159 : }
160 : #endif
161 : VM_BUG_ON(PageTail(page));
162 :
163 : return 1;
164 : }
165 :
166 : /*
167 : * Same as above, but add instead of inc (could just be merged)
168 : */
169 : static inline int page_cache_add_speculative(struct page *page, int count)
170 : {
171 : VM_BUG_ON(in_interrupt());
172 :
173 : #if !defined(CONFIG_SMP) && defined(CONFIG_TREE_RCU)
174 : # ifdef CONFIG_PREEMPT
175 : VM_BUG_ON(!in_atomic());
176 : # endif
177 : VM_BUG_ON(page_count(page) == 0);
178 : atomic_add(count, &page->_count);
179 :
180 : #else
181 : if (unlikely(!atomic_add_unless(&page->_count, count, 0)))
182 : return 0;
183 : #endif
184 : VM_BUG_ON(PageCompound(page) && page != compound_head(page));
185 :
186 : return 1;
187 : }
188 :
189 : static inline int page_freeze_refs(struct page *page, int count)
190 : {
191 : return likely(atomic_cmpxchg(&page->_count, count, 0) == count);
192 : }
193 :
194 : static inline void page_unfreeze_refs(struct page *page, int count)
195 : {
196 : VM_BUG_ON(page_count(page) != 0);
197 : VM_BUG_ON(count == 0);
198 :
199 : atomic_set(&page->_count, count);
200 : }
201 :
202 : #ifdef CONFIG_NUMA
203 : extern struct page *__page_cache_alloc(gfp_t gfp);
204 : #else
205 : static inline struct page *__page_cache_alloc(gfp_t gfp)
206 : {
207 : return alloc_pages(gfp, 0);
208 : }
209 : #endif
210 :
211 : static inline struct page *page_cache_alloc(struct address_space *x)
212 : {
213 : return __page_cache_alloc(mapping_gfp_mask(x));
214 : }
215 :
216 : static inline struct page *page_cache_alloc_cold(struct address_space *x)
217 : {
218 : return __page_cache_alloc(mapping_gfp_mask(x)|__GFP_COLD);
219 : }
220 :
221 : typedef int filler_t(void *, struct page *);
222 :
223 : extern struct page * find_get_page(struct address_space *mapping,
224 : pgoff_t index);
225 : extern struct page * find_lock_page(struct address_space *mapping,
226 : pgoff_t index);
227 : extern struct page * find_or_create_page(struct address_space *mapping,
228 : pgoff_t index, gfp_t gfp_mask);
229 : unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
230 : unsigned int nr_pages, struct page **pages);
231 : unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t start,
232 : unsigned int nr_pages, struct page **pages);
233 : unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
234 : int tag, unsigned int nr_pages, struct page **pages);
235 :
236 : struct page *grab_cache_page_write_begin(struct address_space *mapping,
237 : pgoff_t index, unsigned flags);
238 :
239 : /*
240 : * Returns locked page at given index in given cache, creating it if needed.
241 : */
242 : static inline struct page *grab_cache_page(struct address_space *mapping,
243 : pgoff_t index)
244 : {
245 : return find_or_create_page(mapping, index, mapping_gfp_mask(mapping));
246 : }
247 :
248 : extern struct page * grab_cache_page_nowait(struct address_space *mapping,
249 : pgoff_t index);
250 : extern struct page * read_cache_page_async(struct address_space *mapping,
251 : pgoff_t index, filler_t *filler,
252 : void *data);
253 : extern struct page * read_cache_page(struct address_space *mapping,
254 : pgoff_t index, filler_t *filler,
255 : void *data);
256 : extern struct page * read_cache_page_gfp(struct address_space *mapping,
257 : pgoff_t index, gfp_t gfp_mask);
258 : extern int read_cache_pages(struct address_space *mapping,
259 : struct list_head *pages, filler_t *filler, void *data);
260 :
261 : static inline struct page *read_mapping_page_async(
262 : struct address_space *mapping,
263 : pgoff_t index, void *data)
264 : {
265 : filler_t *filler = (filler_t *)mapping->a_ops->readpage;
266 : return read_cache_page_async(mapping, index, filler, data);
267 : }
268 :
269 : static inline struct page *read_mapping_page(struct address_space *mapping,
270 : pgoff_t index, void *data)
271 : {
272 : filler_t *filler = (filler_t *)mapping->a_ops->readpage;
273 : return read_cache_page(mapping, index, filler, data);
274 : }
275 :
276 : /*
277 : * Return byte-offset into filesystem object for page.
278 : */
279 : static inline loff_t page_offset(struct page *page)
280 : {
281 : return ((loff_t)page->index) << PAGE_CACHE_SHIFT;
282 : }
283 :
284 : static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
285 : unsigned long address)
286 : {
287 : pgoff_t pgoff = (address - vma->vm_start) >> PAGE_SHIFT;
288 : pgoff += vma->vm_pgoff;
289 : return pgoff >> (PAGE_CACHE_SHIFT - PAGE_SHIFT);
290 : }
291 :
292 : extern void __lock_page(struct page *page);
293 : extern int __lock_page_killable(struct page *page);
294 : extern void __lock_page_nosync(struct page *page);
295 : extern void unlock_page(struct page *page);
296 :
297 : static inline void __set_page_locked(struct page *page)
298 : {
299 : __set_bit(PG_locked, &page->flags);
300 : }
301 :
302 : static inline void __clear_page_locked(struct page *page)
303 : {
304 : __clear_bit(PG_locked, &page->flags);
305 : }
306 :
307 : static inline int trylock_page(struct page *page)
308 : {
309 : return (likely(!test_and_set_bit_lock(PG_locked, &page->flags)));
310 : }
311 :
312 : /*
313 : * lock_page may only be called if we have the page's inode pinned.
314 : */
315 : static inline void lock_page(struct page *page)
316 : {
317 : might_sleep();
318 : if (!trylock_page(page))
319 : __lock_page(page);
320 : }
321 :
322 : /*
323 : * lock_page_killable is like lock_page but can be interrupted by fatal
324 : * signals. It returns 0 if it locked the page and -EINTR if it was
325 : * killed while waiting.
326 : */
327 : static inline int lock_page_killable(struct page *page)
328 : {
329 : might_sleep();
330 : if (!trylock_page(page))
331 : return __lock_page_killable(page);
332 : return 0;
333 : }
334 :
335 : /*
336 : * lock_page_nosync should only be used if we can't pin the page's inode.
337 : * Doesn't play quite so well with block device plugging.
338 : */
339 : static inline void lock_page_nosync(struct page *page)
340 : {
341 : might_sleep();
342 : if (!trylock_page(page))
343 : __lock_page_nosync(page);
344 : }
345 :
346 : /*
347 : * This is exported only for wait_on_page_locked/wait_on_page_writeback.
348 : * Never use this directly!
349 : */
350 : extern void wait_on_page_bit(struct page *page, int bit_nr);
351 :
352 : /*
353 : * Wait for a page to be unlocked.
354 : *
355 : * This must be called with the caller "holding" the page,
356 : * ie with increased "page->count" so that the page won't
357 : * go away during the wait..
358 : */
359 : static inline void wait_on_page_locked(struct page *page)
360 : {
361 : if (PageLocked(page))
362 : wait_on_page_bit(page, PG_locked);
363 : }
364 :
365 : /*
366 : * Wait for a page to complete writeback
367 : */
368 : static inline void wait_on_page_writeback(struct page *page)
369 : {
370 : if (PageWriteback(page))
371 : wait_on_page_bit(page, PG_writeback);
372 : }
373 :
374 : extern void end_page_writeback(struct page *page);
375 :
376 : /*
377 : * Add an arbitrary waiter to a page's wait queue
378 : */
379 : extern void add_page_wait_queue(struct page *page, wait_queue_t *waiter);
380 :
381 : /*
382 : * Fault a userspace page into pagetables. Return non-zero on a fault.
383 : *
384 : * This assumes that two userspace pages are always sufficient. That's
385 : * not true if PAGE_CACHE_SIZE > PAGE_SIZE.
386 : */
387 : static inline int fault_in_pages_writeable(char __user *uaddr, int size)
388 : {
389 : int ret;
390 :
391 : if (unlikely(size == 0))
392 : return 0;
393 :
394 : /*
395 : * Writing zeroes into userspace here is OK, because we know that if
396 : * the zero gets there, we'll be overwriting it.
397 : */
398 : ret = __put_user(0, uaddr);
399 : if (ret == 0) {
400 : char __user *end = uaddr + size - 1;
401 :
402 : /*
403 : * If the page was already mapped, this will get a cache miss
404 : * for sure, so try to avoid doing it.
405 : */
406 : if (((unsigned long)uaddr & PAGE_MASK) !=
407 : ((unsigned long)end & PAGE_MASK))
408 : ret = __put_user(0, end);
409 : }
410 : return ret;
411 : }
412 :
413 : static inline int fault_in_pages_readable(const char __user *uaddr, int size)
414 : {
415 : volatile char c;
416 : int ret;
417 :
418 : if (unlikely(size == 0))
419 : return 0;
420 :
421 : ret = __get_user(c, uaddr);
422 : if (ret == 0) {
423 : const char __user *end = uaddr + size - 1;
424 :
425 : if (((unsigned long)uaddr & PAGE_MASK) !=
426 : ((unsigned long)end & PAGE_MASK))
427 : ret = __get_user(c, end);
428 : }
429 : return ret;
430 : }
431 :
432 : int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
433 : pgoff_t index, gfp_t gfp_mask);
434 : int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
435 : pgoff_t index, gfp_t gfp_mask);
436 : extern void remove_from_page_cache(struct page *page);
437 : extern void __remove_from_page_cache(struct page *page);
438 :
439 : /*
440 : * Like add_to_page_cache_locked, but used to add newly allocated pages:
441 : * the page is new, so we can just run __set_page_locked() against it.
442 : */
443 : static inline int add_to_page_cache(struct page *page,
444 : struct address_space *mapping, pgoff_t offset, gfp_t gfp_mask)
445 : {
446 : int error;
447 :
448 : __set_page_locked(page);
449 : error = add_to_page_cache_locked(page, mapping, offset, gfp_mask);
450 : if (unlikely(error))
451 : __clear_page_locked(page);
452 : return error;
453 : }
454 1 :
455 : #endif /* _LINUX_PAGEMAP_H */
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