Commit | Line | Data |
---|---|---|
1da177e4 LT |
1 | /* |
2 | * mm/readahead.c - address_space-level file readahead. | |
3 | * | |
4 | * Copyright (C) 2002, Linus Torvalds | |
5 | * | |
e1f8e874 | 6 | * 09Apr2002 Andrew Morton |
1da177e4 LT |
7 | * Initial version. |
8 | */ | |
9 | ||
10 | #include <linux/kernel.h> | |
11bd969f | 11 | #include <linux/dax.h> |
5a0e3ad6 | 12 | #include <linux/gfp.h> |
b95f1b31 | 13 | #include <linux/export.h> |
1da177e4 LT |
14 | #include <linux/blkdev.h> |
15 | #include <linux/backing-dev.h> | |
8bde37f0 | 16 | #include <linux/task_io_accounting_ops.h> |
1da177e4 | 17 | #include <linux/pagevec.h> |
f5ff8422 | 18 | #include <linux/pagemap.h> |
782182e5 CW |
19 | #include <linux/syscalls.h> |
20 | #include <linux/file.h> | |
d72ee911 | 21 | #include <linux/mm_inline.h> |
1da177e4 | 22 | |
29f175d1 FF |
23 | #include "internal.h" |
24 | ||
1da177e4 LT |
25 | /* |
26 | * Initialise a struct file's readahead state. Assumes that the caller has | |
27 | * memset *ra to zero. | |
28 | */ | |
29 | void | |
30 | file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping) | |
31 | { | |
de1414a6 | 32 | ra->ra_pages = inode_to_bdi(mapping->host)->ra_pages; |
f4e6b498 | 33 | ra->prev_pos = -1; |
1da177e4 | 34 | } |
d41cc702 | 35 | EXPORT_SYMBOL_GPL(file_ra_state_init); |
1da177e4 | 36 | |
03fb3d2a DH |
37 | /* |
38 | * see if a page needs releasing upon read_cache_pages() failure | |
266cf658 DH |
39 | * - the caller of read_cache_pages() may have set PG_private or PG_fscache |
40 | * before calling, such as the NFS fs marking pages that are cached locally | |
41 | * on disk, thus we need to give the fs a chance to clean up in the event of | |
42 | * an error | |
03fb3d2a DH |
43 | */ |
44 | static void read_cache_pages_invalidate_page(struct address_space *mapping, | |
45 | struct page *page) | |
46 | { | |
266cf658 | 47 | if (page_has_private(page)) { |
03fb3d2a DH |
48 | if (!trylock_page(page)) |
49 | BUG(); | |
50 | page->mapping = mapping; | |
09cbfeaf | 51 | do_invalidatepage(page, 0, PAGE_SIZE); |
03fb3d2a DH |
52 | page->mapping = NULL; |
53 | unlock_page(page); | |
54 | } | |
09cbfeaf | 55 | put_page(page); |
03fb3d2a DH |
56 | } |
57 | ||
58 | /* | |
59 | * release a list of pages, invalidating them first if need be | |
60 | */ | |
61 | static void read_cache_pages_invalidate_pages(struct address_space *mapping, | |
62 | struct list_head *pages) | |
63 | { | |
64 | struct page *victim; | |
65 | ||
66 | while (!list_empty(pages)) { | |
c8ad6302 | 67 | victim = lru_to_page(pages); |
03fb3d2a DH |
68 | list_del(&victim->lru); |
69 | read_cache_pages_invalidate_page(mapping, victim); | |
70 | } | |
71 | } | |
72 | ||
1da177e4 | 73 | /** |
bd40cdda | 74 | * read_cache_pages - populate an address space with some pages & start reads against them |
1da177e4 LT |
75 | * @mapping: the address_space |
76 | * @pages: The address of a list_head which contains the target pages. These | |
77 | * pages have their ->index populated and are otherwise uninitialised. | |
78 | * @filler: callback routine for filling a single page. | |
79 | * @data: private data for the callback routine. | |
80 | * | |
81 | * Hides the details of the LRU cache etc from the filesystems. | |
82 | */ | |
83 | int read_cache_pages(struct address_space *mapping, struct list_head *pages, | |
c1e98bf2 | 84 | int (*filler)(struct file *, struct page *), void *data) |
1da177e4 LT |
85 | { |
86 | struct page *page; | |
1da177e4 LT |
87 | int ret = 0; |
88 | ||
1da177e4 | 89 | while (!list_empty(pages)) { |
c8ad6302 | 90 | page = lru_to_page(pages); |
1da177e4 | 91 | list_del(&page->lru); |
063d99b4 | 92 | if (add_to_page_cache_lru(page, mapping, page->index, |
8a5c743e | 93 | readahead_gfp_mask(mapping))) { |
03fb3d2a | 94 | read_cache_pages_invalidate_page(mapping, page); |
1da177e4 LT |
95 | continue; |
96 | } | |
09cbfeaf | 97 | put_page(page); |
eb2be189 | 98 | |
1da177e4 | 99 | ret = filler(data, page); |
eb2be189 | 100 | if (unlikely(ret)) { |
03fb3d2a | 101 | read_cache_pages_invalidate_pages(mapping, pages); |
1da177e4 LT |
102 | break; |
103 | } | |
09cbfeaf | 104 | task_io_account_read(PAGE_SIZE); |
1da177e4 | 105 | } |
1da177e4 LT |
106 | return ret; |
107 | } | |
108 | ||
109 | EXPORT_SYMBOL(read_cache_pages); | |
110 | ||
111 | static int read_pages(struct address_space *mapping, struct file *filp, | |
8a5c743e | 112 | struct list_head *pages, unsigned int nr_pages, gfp_t gfp) |
1da177e4 | 113 | { |
5b417b18 | 114 | struct blk_plug plug; |
1da177e4 | 115 | unsigned page_idx; |
994fc28c | 116 | int ret; |
1da177e4 | 117 | |
5b417b18 JA |
118 | blk_start_plug(&plug); |
119 | ||
1da177e4 LT |
120 | if (mapping->a_ops->readpages) { |
121 | ret = mapping->a_ops->readpages(filp, mapping, pages, nr_pages); | |
029e332e OH |
122 | /* Clean up the remaining pages */ |
123 | put_pages_list(pages); | |
1da177e4 LT |
124 | goto out; |
125 | } | |
126 | ||
1da177e4 | 127 | for (page_idx = 0; page_idx < nr_pages; page_idx++) { |
c8ad6302 | 128 | struct page *page = lru_to_page(pages); |
1da177e4 | 129 | list_del(&page->lru); |
8a5c743e | 130 | if (!add_to_page_cache_lru(page, mapping, page->index, gfp)) |
9f1a3cfc | 131 | mapping->a_ops->readpage(filp, page); |
09cbfeaf | 132 | put_page(page); |
1da177e4 | 133 | } |
994fc28c | 134 | ret = 0; |
5b417b18 | 135 | |
1da177e4 | 136 | out: |
5b417b18 JA |
137 | blk_finish_plug(&plug); |
138 | ||
1da177e4 LT |
139 | return ret; |
140 | } | |
141 | ||
1da177e4 | 142 | /* |
d30a1100 | 143 | * __do_page_cache_readahead() actually reads a chunk of disk. It allocates all |
1da177e4 LT |
144 | * the pages first, then submits them all for I/O. This avoids the very bad |
145 | * behaviour which would occur if page allocations are causing VM writeback. | |
146 | * We really don't want to intermingle reads and writes like that. | |
147 | * | |
148 | * Returns the number of pages requested, or the maximum amount of I/O allowed. | |
1da177e4 | 149 | */ |
29f175d1 | 150 | int __do_page_cache_readahead(struct address_space *mapping, struct file *filp, |
46fc3e7b FW |
151 | pgoff_t offset, unsigned long nr_to_read, |
152 | unsigned long lookahead_size) | |
1da177e4 LT |
153 | { |
154 | struct inode *inode = mapping->host; | |
155 | struct page *page; | |
156 | unsigned long end_index; /* The last page we want to read */ | |
157 | LIST_HEAD(page_pool); | |
158 | int page_idx; | |
159 | int ret = 0; | |
160 | loff_t isize = i_size_read(inode); | |
8a5c743e | 161 | gfp_t gfp_mask = readahead_gfp_mask(mapping); |
1da177e4 LT |
162 | |
163 | if (isize == 0) | |
164 | goto out; | |
165 | ||
09cbfeaf | 166 | end_index = ((isize - 1) >> PAGE_SHIFT); |
1da177e4 LT |
167 | |
168 | /* | |
169 | * Preallocate as many pages as we will need. | |
170 | */ | |
1da177e4 | 171 | for (page_idx = 0; page_idx < nr_to_read; page_idx++) { |
7361f4d8 | 172 | pgoff_t page_offset = offset + page_idx; |
c743d96b | 173 | |
1da177e4 LT |
174 | if (page_offset > end_index) |
175 | break; | |
176 | ||
00128188 | 177 | rcu_read_lock(); |
1da177e4 | 178 | page = radix_tree_lookup(&mapping->page_tree, page_offset); |
00128188 | 179 | rcu_read_unlock(); |
0cd6144a | 180 | if (page && !radix_tree_exceptional_entry(page)) |
1da177e4 LT |
181 | continue; |
182 | ||
8a5c743e | 183 | page = __page_cache_alloc(gfp_mask); |
1da177e4 LT |
184 | if (!page) |
185 | break; | |
186 | page->index = page_offset; | |
187 | list_add(&page->lru, &page_pool); | |
46fc3e7b FW |
188 | if (page_idx == nr_to_read - lookahead_size) |
189 | SetPageReadahead(page); | |
1da177e4 LT |
190 | ret++; |
191 | } | |
1da177e4 LT |
192 | |
193 | /* | |
194 | * Now start the IO. We ignore I/O errors - if the page is not | |
195 | * uptodate then the caller will launch readpage again, and | |
196 | * will then handle the error. | |
197 | */ | |
198 | if (ret) | |
8a5c743e | 199 | read_pages(mapping, filp, &page_pool, ret, gfp_mask); |
1da177e4 LT |
200 | BUG_ON(!list_empty(&page_pool)); |
201 | out: | |
202 | return ret; | |
203 | } | |
204 | ||
205 | /* | |
206 | * Chunk the readahead into 2 megabyte units, so that we don't pin too much | |
207 | * memory at once. | |
208 | */ | |
209 | int force_page_cache_readahead(struct address_space *mapping, struct file *filp, | |
9491ae4a | 210 | pgoff_t offset, unsigned long nr_to_read) |
1da177e4 | 211 | { |
9491ae4a JA |
212 | struct backing_dev_info *bdi = inode_to_bdi(mapping->host); |
213 | struct file_ra_state *ra = &filp->f_ra; | |
214 | unsigned long max_pages; | |
215 | ||
1da177e4 LT |
216 | if (unlikely(!mapping->a_ops->readpage && !mapping->a_ops->readpages)) |
217 | return -EINVAL; | |
218 | ||
9491ae4a JA |
219 | /* |
220 | * If the request exceeds the readahead window, allow the read to | |
221 | * be up to the optimal hardware IO size | |
222 | */ | |
223 | max_pages = max_t(unsigned long, bdi->io_pages, ra->ra_pages); | |
224 | nr_to_read = min(nr_to_read, max_pages); | |
1da177e4 LT |
225 | while (nr_to_read) { |
226 | int err; | |
227 | ||
09cbfeaf | 228 | unsigned long this_chunk = (2 * 1024 * 1024) / PAGE_SIZE; |
1da177e4 LT |
229 | |
230 | if (this_chunk > nr_to_read) | |
231 | this_chunk = nr_to_read; | |
232 | err = __do_page_cache_readahead(mapping, filp, | |
46fc3e7b | 233 | offset, this_chunk, 0); |
58d5640e MR |
234 | if (err < 0) |
235 | return err; | |
236 | ||
1da177e4 LT |
237 | offset += this_chunk; |
238 | nr_to_read -= this_chunk; | |
239 | } | |
58d5640e | 240 | return 0; |
1da177e4 LT |
241 | } |
242 | ||
c743d96b FW |
243 | /* |
244 | * Set the initial window size, round to next power of 2 and square | |
245 | * for small size, x 4 for medium, and x 2 for large | |
246 | * for 128k (32 page) max ra | |
247 | * 1-8 page = 32k initial, > 8 page = 128k initial | |
248 | */ | |
249 | static unsigned long get_init_ra_size(unsigned long size, unsigned long max) | |
250 | { | |
251 | unsigned long newsize = roundup_pow_of_two(size); | |
252 | ||
253 | if (newsize <= max / 32) | |
254 | newsize = newsize * 4; | |
255 | else if (newsize <= max / 4) | |
256 | newsize = newsize * 2; | |
257 | else | |
258 | newsize = max; | |
259 | ||
260 | return newsize; | |
261 | } | |
262 | ||
122a21d1 FW |
263 | /* |
264 | * Get the previous window size, ramp it up, and | |
265 | * return it as the new window size. | |
266 | */ | |
c743d96b | 267 | static unsigned long get_next_ra_size(struct file_ra_state *ra, |
122a21d1 FW |
268 | unsigned long max) |
269 | { | |
f9acc8c7 | 270 | unsigned long cur = ra->size; |
122a21d1 FW |
271 | unsigned long newsize; |
272 | ||
273 | if (cur < max / 16) | |
c743d96b | 274 | newsize = 4 * cur; |
122a21d1 | 275 | else |
c743d96b | 276 | newsize = 2 * cur; |
122a21d1 FW |
277 | |
278 | return min(newsize, max); | |
279 | } | |
280 | ||
281 | /* | |
282 | * On-demand readahead design. | |
283 | * | |
284 | * The fields in struct file_ra_state represent the most-recently-executed | |
285 | * readahead attempt: | |
286 | * | |
f9acc8c7 FW |
287 | * |<----- async_size ---------| |
288 | * |------------------- size -------------------->| | |
289 | * |==================#===========================| | |
290 | * ^start ^page marked with PG_readahead | |
122a21d1 FW |
291 | * |
292 | * To overlap application thinking time and disk I/O time, we do | |
293 | * `readahead pipelining': Do not wait until the application consumed all | |
294 | * readahead pages and stalled on the missing page at readahead_index; | |
f9acc8c7 FW |
295 | * Instead, submit an asynchronous readahead I/O as soon as there are |
296 | * only async_size pages left in the readahead window. Normally async_size | |
297 | * will be equal to size, for maximum pipelining. | |
122a21d1 FW |
298 | * |
299 | * In interleaved sequential reads, concurrent streams on the same fd can | |
300 | * be invalidating each other's readahead state. So we flag the new readahead | |
f9acc8c7 | 301 | * page at (start+size-async_size) with PG_readahead, and use it as readahead |
122a21d1 FW |
302 | * indicator. The flag won't be set on already cached pages, to avoid the |
303 | * readahead-for-nothing fuss, saving pointless page cache lookups. | |
304 | * | |
f4e6b498 | 305 | * prev_pos tracks the last visited byte in the _previous_ read request. |
122a21d1 FW |
306 | * It should be maintained by the caller, and will be used for detecting |
307 | * small random reads. Note that the readahead algorithm checks loosely | |
308 | * for sequential patterns. Hence interleaved reads might be served as | |
309 | * sequential ones. | |
310 | * | |
311 | * There is a special-case: if the first page which the application tries to | |
312 | * read happens to be the first page of the file, it is assumed that a linear | |
313 | * read is about to happen and the window is immediately set to the initial size | |
314 | * based on I/O request size and the max_readahead. | |
315 | * | |
316 | * The code ramps up the readahead size aggressively at first, but slow down as | |
317 | * it approaches max_readhead. | |
318 | */ | |
319 | ||
10be0b37 WF |
320 | /* |
321 | * Count contiguously cached pages from @offset-1 to @offset-@max, | |
322 | * this count is a conservative estimation of | |
323 | * - length of the sequential read sequence, or | |
324 | * - thrashing threshold in memory tight systems | |
325 | */ | |
326 | static pgoff_t count_history_pages(struct address_space *mapping, | |
10be0b37 WF |
327 | pgoff_t offset, unsigned long max) |
328 | { | |
329 | pgoff_t head; | |
330 | ||
331 | rcu_read_lock(); | |
e7b563bb | 332 | head = page_cache_prev_hole(mapping, offset - 1, max); |
10be0b37 WF |
333 | rcu_read_unlock(); |
334 | ||
335 | return offset - 1 - head; | |
336 | } | |
337 | ||
338 | /* | |
339 | * page cache context based read-ahead | |
340 | */ | |
341 | static int try_context_readahead(struct address_space *mapping, | |
342 | struct file_ra_state *ra, | |
343 | pgoff_t offset, | |
344 | unsigned long req_size, | |
345 | unsigned long max) | |
346 | { | |
347 | pgoff_t size; | |
348 | ||
3e2faa08 | 349 | size = count_history_pages(mapping, offset, max); |
10be0b37 WF |
350 | |
351 | /* | |
2cad4018 | 352 | * not enough history pages: |
10be0b37 WF |
353 | * it could be a random read |
354 | */ | |
2cad4018 | 355 | if (size <= req_size) |
10be0b37 WF |
356 | return 0; |
357 | ||
358 | /* | |
359 | * starts from beginning of file: | |
360 | * it is a strong indication of long-run stream (or whole-file-read) | |
361 | */ | |
362 | if (size >= offset) | |
363 | size *= 2; | |
364 | ||
365 | ra->start = offset; | |
2cad4018 FW |
366 | ra->size = min(size + req_size, max); |
367 | ra->async_size = 1; | |
10be0b37 WF |
368 | |
369 | return 1; | |
370 | } | |
371 | ||
122a21d1 FW |
372 | /* |
373 | * A minimal readahead algorithm for trivial sequential/random reads. | |
374 | */ | |
375 | static unsigned long | |
376 | ondemand_readahead(struct address_space *mapping, | |
377 | struct file_ra_state *ra, struct file *filp, | |
cf914a7d | 378 | bool hit_readahead_marker, pgoff_t offset, |
122a21d1 FW |
379 | unsigned long req_size) |
380 | { | |
9491ae4a JA |
381 | struct backing_dev_info *bdi = inode_to_bdi(mapping->host); |
382 | unsigned long max_pages = ra->ra_pages; | |
cf12d0f9 | 383 | unsigned long add_pages; |
af248a0c | 384 | pgoff_t prev_offset; |
045a2529 | 385 | |
9491ae4a JA |
386 | /* |
387 | * If the request exceeds the readahead window, allow the read to | |
388 | * be up to the optimal hardware IO size | |
389 | */ | |
390 | if (req_size > max_pages && bdi->io_pages > max_pages) | |
391 | max_pages = min(req_size, bdi->io_pages); | |
392 | ||
045a2529 WF |
393 | /* |
394 | * start of file | |
395 | */ | |
396 | if (!offset) | |
397 | goto initial_readahead; | |
122a21d1 FW |
398 | |
399 | /* | |
f9acc8c7 | 400 | * It's the expected callback offset, assume sequential access. |
122a21d1 FW |
401 | * Ramp up sizes, and push forward the readahead window. |
402 | */ | |
045a2529 WF |
403 | if ((offset == (ra->start + ra->size - ra->async_size) || |
404 | offset == (ra->start + ra->size))) { | |
f9acc8c7 | 405 | ra->start += ra->size; |
9491ae4a | 406 | ra->size = get_next_ra_size(ra, max_pages); |
f9acc8c7 FW |
407 | ra->async_size = ra->size; |
408 | goto readit; | |
122a21d1 FW |
409 | } |
410 | ||
6b10c6c9 FW |
411 | /* |
412 | * Hit a marked page without valid readahead state. | |
413 | * E.g. interleaved reads. | |
414 | * Query the pagecache for async_size, which normally equals to | |
415 | * readahead size. Ramp it up and use it as the new readahead size. | |
416 | */ | |
417 | if (hit_readahead_marker) { | |
418 | pgoff_t start; | |
419 | ||
30002ed2 | 420 | rcu_read_lock(); |
9491ae4a | 421 | start = page_cache_next_hole(mapping, offset + 1, max_pages); |
30002ed2 | 422 | rcu_read_unlock(); |
6b10c6c9 | 423 | |
9491ae4a | 424 | if (!start || start - offset > max_pages) |
6b10c6c9 FW |
425 | return 0; |
426 | ||
427 | ra->start = start; | |
428 | ra->size = start - offset; /* old async_size */ | |
160334a0 | 429 | ra->size += req_size; |
9491ae4a | 430 | ra->size = get_next_ra_size(ra, max_pages); |
6b10c6c9 FW |
431 | ra->async_size = ra->size; |
432 | goto readit; | |
433 | } | |
434 | ||
122a21d1 | 435 | /* |
045a2529 | 436 | * oversize read |
122a21d1 | 437 | */ |
9491ae4a | 438 | if (req_size > max_pages) |
045a2529 WF |
439 | goto initial_readahead; |
440 | ||
441 | /* | |
442 | * sequential cache miss | |
af248a0c DR |
443 | * trivial case: (offset - prev_offset) == 1 |
444 | * unaligned reads: (offset - prev_offset) == 0 | |
045a2529 | 445 | */ |
09cbfeaf | 446 | prev_offset = (unsigned long long)ra->prev_pos >> PAGE_SHIFT; |
af248a0c | 447 | if (offset - prev_offset <= 1UL) |
045a2529 WF |
448 | goto initial_readahead; |
449 | ||
10be0b37 WF |
450 | /* |
451 | * Query the page cache and look for the traces(cached history pages) | |
452 | * that a sequential stream would leave behind. | |
453 | */ | |
9491ae4a | 454 | if (try_context_readahead(mapping, ra, offset, req_size, max_pages)) |
10be0b37 WF |
455 | goto readit; |
456 | ||
045a2529 WF |
457 | /* |
458 | * standalone, small random read | |
459 | * Read as is, and do not pollute the readahead state. | |
460 | */ | |
461 | return __do_page_cache_readahead(mapping, filp, offset, req_size, 0); | |
462 | ||
463 | initial_readahead: | |
f9acc8c7 | 464 | ra->start = offset; |
9491ae4a | 465 | ra->size = get_init_ra_size(req_size, max_pages); |
f9acc8c7 | 466 | ra->async_size = ra->size > req_size ? ra->size - req_size : ra->size; |
122a21d1 | 467 | |
f9acc8c7 | 468 | readit: |
51daa88e WF |
469 | /* |
470 | * Will this read hit the readahead marker made by itself? | |
471 | * If so, trigger the readahead marker hit now, and merge | |
472 | * the resulted next readahead window into the current one. | |
cf12d0f9 | 473 | * Take care of maximum IO pages as above. |
51daa88e WF |
474 | */ |
475 | if (offset == ra->start && ra->size == ra->async_size) { | |
cf12d0f9 MS |
476 | add_pages = get_next_ra_size(ra, max_pages); |
477 | if (ra->size + add_pages <= max_pages) { | |
478 | ra->async_size = add_pages; | |
479 | ra->size += add_pages; | |
480 | } else { | |
481 | ra->size = max_pages; | |
482 | ra->async_size = max_pages >> 1; | |
483 | } | |
51daa88e WF |
484 | } |
485 | ||
122a21d1 FW |
486 | return ra_submit(ra, mapping, filp); |
487 | } | |
488 | ||
489 | /** | |
cf914a7d | 490 | * page_cache_sync_readahead - generic file readahead |
122a21d1 FW |
491 | * @mapping: address_space which holds the pagecache and I/O vectors |
492 | * @ra: file_ra_state which holds the readahead state | |
493 | * @filp: passed on to ->readpage() and ->readpages() | |
cf914a7d | 494 | * @offset: start offset into @mapping, in pagecache page-sized units |
122a21d1 | 495 | * @req_size: hint: total size of the read which the caller is performing in |
cf914a7d | 496 | * pagecache pages |
122a21d1 | 497 | * |
cf914a7d RR |
498 | * page_cache_sync_readahead() should be called when a cache miss happened: |
499 | * it will submit the read. The readahead logic may decide to piggyback more | |
500 | * pages onto the read request if access patterns suggest it will improve | |
501 | * performance. | |
122a21d1 | 502 | */ |
cf914a7d RR |
503 | void page_cache_sync_readahead(struct address_space *mapping, |
504 | struct file_ra_state *ra, struct file *filp, | |
505 | pgoff_t offset, unsigned long req_size) | |
122a21d1 FW |
506 | { |
507 | /* no read-ahead */ | |
508 | if (!ra->ra_pages) | |
cf914a7d RR |
509 | return; |
510 | ||
0141450f | 511 | /* be dumb */ |
70655c06 | 512 | if (filp && (filp->f_mode & FMODE_RANDOM)) { |
0141450f WF |
513 | force_page_cache_readahead(mapping, filp, offset, req_size); |
514 | return; | |
515 | } | |
516 | ||
cf914a7d RR |
517 | /* do read-ahead */ |
518 | ondemand_readahead(mapping, ra, filp, false, offset, req_size); | |
519 | } | |
520 | EXPORT_SYMBOL_GPL(page_cache_sync_readahead); | |
521 | ||
522 | /** | |
523 | * page_cache_async_readahead - file readahead for marked pages | |
524 | * @mapping: address_space which holds the pagecache and I/O vectors | |
525 | * @ra: file_ra_state which holds the readahead state | |
526 | * @filp: passed on to ->readpage() and ->readpages() | |
527 | * @page: the page at @offset which has the PG_readahead flag set | |
528 | * @offset: start offset into @mapping, in pagecache page-sized units | |
529 | * @req_size: hint: total size of the read which the caller is performing in | |
530 | * pagecache pages | |
531 | * | |
bf8abe8b | 532 | * page_cache_async_readahead() should be called when a page is used which |
f7850d93 | 533 | * has the PG_readahead flag; this is a marker to suggest that the application |
cf914a7d | 534 | * has used up enough of the readahead window that we should start pulling in |
f7850d93 RD |
535 | * more pages. |
536 | */ | |
cf914a7d RR |
537 | void |
538 | page_cache_async_readahead(struct address_space *mapping, | |
539 | struct file_ra_state *ra, struct file *filp, | |
540 | struct page *page, pgoff_t offset, | |
541 | unsigned long req_size) | |
542 | { | |
543 | /* no read-ahead */ | |
544 | if (!ra->ra_pages) | |
545 | return; | |
546 | ||
547 | /* | |
548 | * Same bit is used for PG_readahead and PG_reclaim. | |
549 | */ | |
550 | if (PageWriteback(page)) | |
551 | return; | |
552 | ||
553 | ClearPageReadahead(page); | |
554 | ||
555 | /* | |
556 | * Defer asynchronous read-ahead on IO congestion. | |
557 | */ | |
703c2708 | 558 | if (inode_read_congested(mapping->host)) |
cf914a7d | 559 | return; |
122a21d1 FW |
560 | |
561 | /* do read-ahead */ | |
cf914a7d | 562 | ondemand_readahead(mapping, ra, filp, true, offset, req_size); |
122a21d1 | 563 | } |
cf914a7d | 564 | EXPORT_SYMBOL_GPL(page_cache_async_readahead); |
782182e5 CW |
565 | |
566 | static ssize_t | |
567 | do_readahead(struct address_space *mapping, struct file *filp, | |
568 | pgoff_t index, unsigned long nr) | |
569 | { | |
63d0f0a3 | 570 | if (!mapping || !mapping->a_ops) |
782182e5 CW |
571 | return -EINVAL; |
572 | ||
11bd969f RZ |
573 | /* |
574 | * Readahead doesn't make sense for DAX inodes, but we don't want it | |
575 | * to report a failure either. Instead, we just return success and | |
576 | * don't do any work. | |
577 | */ | |
578 | if (dax_mapping(mapping)) | |
579 | return 0; | |
580 | ||
58d5640e | 581 | return force_page_cache_readahead(mapping, filp, index, nr); |
782182e5 CW |
582 | } |
583 | ||
4a0fd5bf | 584 | SYSCALL_DEFINE3(readahead, int, fd, loff_t, offset, size_t, count) |
782182e5 CW |
585 | { |
586 | ssize_t ret; | |
2903ff01 | 587 | struct fd f; |
782182e5 CW |
588 | |
589 | ret = -EBADF; | |
2903ff01 AV |
590 | f = fdget(fd); |
591 | if (f.file) { | |
592 | if (f.file->f_mode & FMODE_READ) { | |
593 | struct address_space *mapping = f.file->f_mapping; | |
09cbfeaf KS |
594 | pgoff_t start = offset >> PAGE_SHIFT; |
595 | pgoff_t end = (offset + count - 1) >> PAGE_SHIFT; | |
782182e5 | 596 | unsigned long len = end - start + 1; |
2903ff01 | 597 | ret = do_readahead(mapping, f.file, start, len); |
782182e5 | 598 | } |
2903ff01 | 599 | fdput(f); |
782182e5 CW |
600 | } |
601 | return ret; | |
602 | } |