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> |
ca47e8c7 | 22 | #include <linux/blk-cgroup.h> |
1da177e4 | 23 | |
29f175d1 FF |
24 | #include "internal.h" |
25 | ||
1da177e4 LT |
26 | /* |
27 | * Initialise a struct file's readahead state. Assumes that the caller has | |
28 | * memset *ra to zero. | |
29 | */ | |
30 | void | |
31 | file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping) | |
32 | { | |
de1414a6 | 33 | ra->ra_pages = inode_to_bdi(mapping->host)->ra_pages; |
f4e6b498 | 34 | ra->prev_pos = -1; |
1da177e4 | 35 | } |
d41cc702 | 36 | EXPORT_SYMBOL_GPL(file_ra_state_init); |
1da177e4 | 37 | |
03fb3d2a DH |
38 | /* |
39 | * see if a page needs releasing upon read_cache_pages() failure | |
266cf658 DH |
40 | * - the caller of read_cache_pages() may have set PG_private or PG_fscache |
41 | * before calling, such as the NFS fs marking pages that are cached locally | |
42 | * on disk, thus we need to give the fs a chance to clean up in the event of | |
43 | * an error | |
03fb3d2a DH |
44 | */ |
45 | static void read_cache_pages_invalidate_page(struct address_space *mapping, | |
46 | struct page *page) | |
47 | { | |
266cf658 | 48 | if (page_has_private(page)) { |
03fb3d2a DH |
49 | if (!trylock_page(page)) |
50 | BUG(); | |
51 | page->mapping = mapping; | |
09cbfeaf | 52 | do_invalidatepage(page, 0, PAGE_SIZE); |
03fb3d2a DH |
53 | page->mapping = NULL; |
54 | unlock_page(page); | |
55 | } | |
09cbfeaf | 56 | put_page(page); |
03fb3d2a DH |
57 | } |
58 | ||
59 | /* | |
60 | * release a list of pages, invalidating them first if need be | |
61 | */ | |
62 | static void read_cache_pages_invalidate_pages(struct address_space *mapping, | |
63 | struct list_head *pages) | |
64 | { | |
65 | struct page *victim; | |
66 | ||
67 | while (!list_empty(pages)) { | |
c8ad6302 | 68 | victim = lru_to_page(pages); |
03fb3d2a DH |
69 | list_del(&victim->lru); |
70 | read_cache_pages_invalidate_page(mapping, victim); | |
71 | } | |
72 | } | |
73 | ||
1da177e4 | 74 | /** |
bd40cdda | 75 | * read_cache_pages - populate an address space with some pages & start reads against them |
1da177e4 LT |
76 | * @mapping: the address_space |
77 | * @pages: The address of a list_head which contains the target pages. These | |
78 | * pages have their ->index populated and are otherwise uninitialised. | |
79 | * @filler: callback routine for filling a single page. | |
80 | * @data: private data for the callback routine. | |
81 | * | |
82 | * Hides the details of the LRU cache etc from the filesystems. | |
83 | */ | |
84 | int read_cache_pages(struct address_space *mapping, struct list_head *pages, | |
85 | int (*filler)(void *, struct page *), void *data) | |
86 | { | |
87 | struct page *page; | |
1da177e4 LT |
88 | int ret = 0; |
89 | ||
1da177e4 | 90 | while (!list_empty(pages)) { |
c8ad6302 | 91 | page = lru_to_page(pages); |
1da177e4 | 92 | list_del(&page->lru); |
063d99b4 | 93 | if (add_to_page_cache_lru(page, mapping, page->index, |
8a5c743e | 94 | readahead_gfp_mask(mapping))) { |
03fb3d2a | 95 | read_cache_pages_invalidate_page(mapping, page); |
1da177e4 LT |
96 | continue; |
97 | } | |
09cbfeaf | 98 | put_page(page); |
eb2be189 | 99 | |
1da177e4 | 100 | ret = filler(data, page); |
eb2be189 | 101 | if (unlikely(ret)) { |
03fb3d2a | 102 | read_cache_pages_invalidate_pages(mapping, pages); |
1da177e4 LT |
103 | break; |
104 | } | |
09cbfeaf | 105 | task_io_account_read(PAGE_SIZE); |
1da177e4 | 106 | } |
1da177e4 LT |
107 | return ret; |
108 | } | |
109 | ||
110 | EXPORT_SYMBOL(read_cache_pages); | |
111 | ||
112 | static int read_pages(struct address_space *mapping, struct file *filp, | |
8a5c743e | 113 | struct list_head *pages, unsigned int nr_pages, gfp_t gfp) |
1da177e4 | 114 | { |
5b417b18 | 115 | struct blk_plug plug; |
1da177e4 | 116 | unsigned page_idx; |
994fc28c | 117 | int ret; |
1da177e4 | 118 | |
5b417b18 JA |
119 | blk_start_plug(&plug); |
120 | ||
1da177e4 LT |
121 | if (mapping->a_ops->readpages) { |
122 | ret = mapping->a_ops->readpages(filp, mapping, pages, nr_pages); | |
029e332e OH |
123 | /* Clean up the remaining pages */ |
124 | put_pages_list(pages); | |
1da177e4 LT |
125 | goto out; |
126 | } | |
127 | ||
1da177e4 | 128 | for (page_idx = 0; page_idx < nr_pages; page_idx++) { |
c8ad6302 | 129 | struct page *page = lru_to_page(pages); |
1da177e4 | 130 | list_del(&page->lru); |
8a5c743e | 131 | if (!add_to_page_cache_lru(page, mapping, page->index, gfp)) |
9f1a3cfc | 132 | mapping->a_ops->readpage(filp, page); |
09cbfeaf | 133 | put_page(page); |
1da177e4 | 134 | } |
994fc28c | 135 | ret = 0; |
5b417b18 | 136 | |
1da177e4 | 137 | out: |
5b417b18 JA |
138 | blk_finish_plug(&plug); |
139 | ||
1da177e4 LT |
140 | return ret; |
141 | } | |
142 | ||
1da177e4 | 143 | /* |
b3751e6a CH |
144 | * __do_page_cache_readahead() actually reads a chunk of disk. It allocates |
145 | * the pages first, then submits them for I/O. This avoids the very bad | |
1da177e4 LT |
146 | * behaviour which would occur if page allocations are causing VM writeback. |
147 | * We really don't want to intermingle reads and writes like that. | |
148 | * | |
149 | * Returns the number of pages requested, or the maximum amount of I/O allowed. | |
1da177e4 | 150 | */ |
c534aa3f CH |
151 | unsigned int __do_page_cache_readahead(struct address_space *mapping, |
152 | struct file *filp, pgoff_t offset, unsigned long nr_to_read, | |
153 | unsigned long lookahead_size) | |
1da177e4 LT |
154 | { |
155 | struct inode *inode = mapping->host; | |
156 | struct page *page; | |
157 | unsigned long end_index; /* The last page we want to read */ | |
158 | LIST_HEAD(page_pool); | |
159 | int page_idx; | |
c534aa3f | 160 | unsigned int nr_pages = 0; |
1da177e4 | 161 | loff_t isize = i_size_read(inode); |
8a5c743e | 162 | gfp_t gfp_mask = readahead_gfp_mask(mapping); |
1da177e4 LT |
163 | |
164 | if (isize == 0) | |
165 | goto out; | |
166 | ||
09cbfeaf | 167 | end_index = ((isize - 1) >> PAGE_SHIFT); |
1da177e4 LT |
168 | |
169 | /* | |
170 | * Preallocate as many pages as we will need. | |
171 | */ | |
1da177e4 | 172 | for (page_idx = 0; page_idx < nr_to_read; page_idx++) { |
7361f4d8 | 173 | pgoff_t page_offset = offset + page_idx; |
c743d96b | 174 | |
1da177e4 LT |
175 | if (page_offset > end_index) |
176 | break; | |
177 | ||
00128188 | 178 | rcu_read_lock(); |
b93b0163 | 179 | page = radix_tree_lookup(&mapping->i_pages, page_offset); |
00128188 | 180 | rcu_read_unlock(); |
b3751e6a CH |
181 | if (page && !radix_tree_exceptional_entry(page)) { |
182 | /* | |
183 | * Page already present? Kick off the current batch of | |
184 | * contiguous pages before continuing with the next | |
185 | * batch. | |
186 | */ | |
187 | if (nr_pages) | |
188 | read_pages(mapping, filp, &page_pool, nr_pages, | |
189 | gfp_mask); | |
190 | nr_pages = 0; | |
1da177e4 | 191 | continue; |
b3751e6a | 192 | } |
1da177e4 | 193 | |
8a5c743e | 194 | page = __page_cache_alloc(gfp_mask); |
1da177e4 LT |
195 | if (!page) |
196 | break; | |
197 | page->index = page_offset; | |
198 | list_add(&page->lru, &page_pool); | |
46fc3e7b FW |
199 | if (page_idx == nr_to_read - lookahead_size) |
200 | SetPageReadahead(page); | |
836978b3 | 201 | nr_pages++; |
1da177e4 | 202 | } |
1da177e4 LT |
203 | |
204 | /* | |
205 | * Now start the IO. We ignore I/O errors - if the page is not | |
206 | * uptodate then the caller will launch readpage again, and | |
207 | * will then handle the error. | |
208 | */ | |
836978b3 CH |
209 | if (nr_pages) |
210 | read_pages(mapping, filp, &page_pool, nr_pages, gfp_mask); | |
1da177e4 LT |
211 | BUG_ON(!list_empty(&page_pool)); |
212 | out: | |
836978b3 | 213 | return nr_pages; |
1da177e4 LT |
214 | } |
215 | ||
216 | /* | |
217 | * Chunk the readahead into 2 megabyte units, so that we don't pin too much | |
218 | * memory at once. | |
219 | */ | |
220 | int force_page_cache_readahead(struct address_space *mapping, struct file *filp, | |
9491ae4a | 221 | pgoff_t offset, unsigned long nr_to_read) |
1da177e4 | 222 | { |
9491ae4a JA |
223 | struct backing_dev_info *bdi = inode_to_bdi(mapping->host); |
224 | struct file_ra_state *ra = &filp->f_ra; | |
225 | unsigned long max_pages; | |
226 | ||
1da177e4 LT |
227 | if (unlikely(!mapping->a_ops->readpage && !mapping->a_ops->readpages)) |
228 | return -EINVAL; | |
229 | ||
9491ae4a JA |
230 | /* |
231 | * If the request exceeds the readahead window, allow the read to | |
232 | * be up to the optimal hardware IO size | |
233 | */ | |
234 | max_pages = max_t(unsigned long, bdi->io_pages, ra->ra_pages); | |
235 | nr_to_read = min(nr_to_read, max_pages); | |
1da177e4 | 236 | while (nr_to_read) { |
09cbfeaf | 237 | unsigned long this_chunk = (2 * 1024 * 1024) / PAGE_SIZE; |
1da177e4 LT |
238 | |
239 | if (this_chunk > nr_to_read) | |
240 | this_chunk = nr_to_read; | |
c534aa3f | 241 | __do_page_cache_readahead(mapping, filp, offset, this_chunk, 0); |
58d5640e | 242 | |
1da177e4 LT |
243 | offset += this_chunk; |
244 | nr_to_read -= this_chunk; | |
245 | } | |
58d5640e | 246 | return 0; |
1da177e4 LT |
247 | } |
248 | ||
c743d96b FW |
249 | /* |
250 | * Set the initial window size, round to next power of 2 and square | |
251 | * for small size, x 4 for medium, and x 2 for large | |
252 | * for 128k (32 page) max ra | |
253 | * 1-8 page = 32k initial, > 8 page = 128k initial | |
254 | */ | |
255 | static unsigned long get_init_ra_size(unsigned long size, unsigned long max) | |
256 | { | |
257 | unsigned long newsize = roundup_pow_of_two(size); | |
258 | ||
259 | if (newsize <= max / 32) | |
260 | newsize = newsize * 4; | |
261 | else if (newsize <= max / 4) | |
262 | newsize = newsize * 2; | |
263 | else | |
264 | newsize = max; | |
265 | ||
266 | return newsize; | |
267 | } | |
268 | ||
122a21d1 FW |
269 | /* |
270 | * Get the previous window size, ramp it up, and | |
271 | * return it as the new window size. | |
272 | */ | |
c743d96b | 273 | static unsigned long get_next_ra_size(struct file_ra_state *ra, |
122a21d1 FW |
274 | unsigned long max) |
275 | { | |
f9acc8c7 | 276 | unsigned long cur = ra->size; |
122a21d1 FW |
277 | unsigned long newsize; |
278 | ||
279 | if (cur < max / 16) | |
c743d96b | 280 | newsize = 4 * cur; |
122a21d1 | 281 | else |
c743d96b | 282 | newsize = 2 * cur; |
122a21d1 FW |
283 | |
284 | return min(newsize, max); | |
285 | } | |
286 | ||
287 | /* | |
288 | * On-demand readahead design. | |
289 | * | |
290 | * The fields in struct file_ra_state represent the most-recently-executed | |
291 | * readahead attempt: | |
292 | * | |
f9acc8c7 FW |
293 | * |<----- async_size ---------| |
294 | * |------------------- size -------------------->| | |
295 | * |==================#===========================| | |
296 | * ^start ^page marked with PG_readahead | |
122a21d1 FW |
297 | * |
298 | * To overlap application thinking time and disk I/O time, we do | |
299 | * `readahead pipelining': Do not wait until the application consumed all | |
300 | * readahead pages and stalled on the missing page at readahead_index; | |
f9acc8c7 FW |
301 | * Instead, submit an asynchronous readahead I/O as soon as there are |
302 | * only async_size pages left in the readahead window. Normally async_size | |
303 | * will be equal to size, for maximum pipelining. | |
122a21d1 FW |
304 | * |
305 | * In interleaved sequential reads, concurrent streams on the same fd can | |
306 | * be invalidating each other's readahead state. So we flag the new readahead | |
f9acc8c7 | 307 | * page at (start+size-async_size) with PG_readahead, and use it as readahead |
122a21d1 FW |
308 | * indicator. The flag won't be set on already cached pages, to avoid the |
309 | * readahead-for-nothing fuss, saving pointless page cache lookups. | |
310 | * | |
f4e6b498 | 311 | * prev_pos tracks the last visited byte in the _previous_ read request. |
122a21d1 FW |
312 | * It should be maintained by the caller, and will be used for detecting |
313 | * small random reads. Note that the readahead algorithm checks loosely | |
314 | * for sequential patterns. Hence interleaved reads might be served as | |
315 | * sequential ones. | |
316 | * | |
317 | * There is a special-case: if the first page which the application tries to | |
318 | * read happens to be the first page of the file, it is assumed that a linear | |
319 | * read is about to happen and the window is immediately set to the initial size | |
320 | * based on I/O request size and the max_readahead. | |
321 | * | |
322 | * The code ramps up the readahead size aggressively at first, but slow down as | |
323 | * it approaches max_readhead. | |
324 | */ | |
325 | ||
10be0b37 WF |
326 | /* |
327 | * Count contiguously cached pages from @offset-1 to @offset-@max, | |
328 | * this count is a conservative estimation of | |
329 | * - length of the sequential read sequence, or | |
330 | * - thrashing threshold in memory tight systems | |
331 | */ | |
332 | static pgoff_t count_history_pages(struct address_space *mapping, | |
10be0b37 WF |
333 | pgoff_t offset, unsigned long max) |
334 | { | |
335 | pgoff_t head; | |
336 | ||
337 | rcu_read_lock(); | |
e7b563bb | 338 | head = page_cache_prev_hole(mapping, offset - 1, max); |
10be0b37 WF |
339 | rcu_read_unlock(); |
340 | ||
341 | return offset - 1 - head; | |
342 | } | |
343 | ||
344 | /* | |
345 | * page cache context based read-ahead | |
346 | */ | |
347 | static int try_context_readahead(struct address_space *mapping, | |
348 | struct file_ra_state *ra, | |
349 | pgoff_t offset, | |
350 | unsigned long req_size, | |
351 | unsigned long max) | |
352 | { | |
353 | pgoff_t size; | |
354 | ||
3e2faa08 | 355 | size = count_history_pages(mapping, offset, max); |
10be0b37 WF |
356 | |
357 | /* | |
2cad4018 | 358 | * not enough history pages: |
10be0b37 WF |
359 | * it could be a random read |
360 | */ | |
2cad4018 | 361 | if (size <= req_size) |
10be0b37 WF |
362 | return 0; |
363 | ||
364 | /* | |
365 | * starts from beginning of file: | |
366 | * it is a strong indication of long-run stream (or whole-file-read) | |
367 | */ | |
368 | if (size >= offset) | |
369 | size *= 2; | |
370 | ||
371 | ra->start = offset; | |
2cad4018 FW |
372 | ra->size = min(size + req_size, max); |
373 | ra->async_size = 1; | |
10be0b37 WF |
374 | |
375 | return 1; | |
376 | } | |
377 | ||
122a21d1 FW |
378 | /* |
379 | * A minimal readahead algorithm for trivial sequential/random reads. | |
380 | */ | |
381 | static unsigned long | |
382 | ondemand_readahead(struct address_space *mapping, | |
383 | struct file_ra_state *ra, struct file *filp, | |
cf914a7d | 384 | bool hit_readahead_marker, pgoff_t offset, |
122a21d1 FW |
385 | unsigned long req_size) |
386 | { | |
9491ae4a JA |
387 | struct backing_dev_info *bdi = inode_to_bdi(mapping->host); |
388 | unsigned long max_pages = ra->ra_pages; | |
dc30b96a | 389 | unsigned long add_pages; |
af248a0c | 390 | pgoff_t prev_offset; |
045a2529 | 391 | |
9491ae4a JA |
392 | /* |
393 | * If the request exceeds the readahead window, allow the read to | |
394 | * be up to the optimal hardware IO size | |
395 | */ | |
396 | if (req_size > max_pages && bdi->io_pages > max_pages) | |
397 | max_pages = min(req_size, bdi->io_pages); | |
398 | ||
045a2529 WF |
399 | /* |
400 | * start of file | |
401 | */ | |
402 | if (!offset) | |
403 | goto initial_readahead; | |
122a21d1 FW |
404 | |
405 | /* | |
f9acc8c7 | 406 | * It's the expected callback offset, assume sequential access. |
122a21d1 FW |
407 | * Ramp up sizes, and push forward the readahead window. |
408 | */ | |
045a2529 WF |
409 | if ((offset == (ra->start + ra->size - ra->async_size) || |
410 | offset == (ra->start + ra->size))) { | |
f9acc8c7 | 411 | ra->start += ra->size; |
9491ae4a | 412 | ra->size = get_next_ra_size(ra, max_pages); |
f9acc8c7 FW |
413 | ra->async_size = ra->size; |
414 | goto readit; | |
122a21d1 FW |
415 | } |
416 | ||
6b10c6c9 FW |
417 | /* |
418 | * Hit a marked page without valid readahead state. | |
419 | * E.g. interleaved reads. | |
420 | * Query the pagecache for async_size, which normally equals to | |
421 | * readahead size. Ramp it up and use it as the new readahead size. | |
422 | */ | |
423 | if (hit_readahead_marker) { | |
424 | pgoff_t start; | |
425 | ||
30002ed2 | 426 | rcu_read_lock(); |
9491ae4a | 427 | start = page_cache_next_hole(mapping, offset + 1, max_pages); |
30002ed2 | 428 | rcu_read_unlock(); |
6b10c6c9 | 429 | |
9491ae4a | 430 | if (!start || start - offset > max_pages) |
6b10c6c9 FW |
431 | return 0; |
432 | ||
433 | ra->start = start; | |
434 | ra->size = start - offset; /* old async_size */ | |
160334a0 | 435 | ra->size += req_size; |
9491ae4a | 436 | ra->size = get_next_ra_size(ra, max_pages); |
6b10c6c9 FW |
437 | ra->async_size = ra->size; |
438 | goto readit; | |
439 | } | |
440 | ||
122a21d1 | 441 | /* |
045a2529 | 442 | * oversize read |
122a21d1 | 443 | */ |
9491ae4a | 444 | if (req_size > max_pages) |
045a2529 WF |
445 | goto initial_readahead; |
446 | ||
447 | /* | |
448 | * sequential cache miss | |
af248a0c DR |
449 | * trivial case: (offset - prev_offset) == 1 |
450 | * unaligned reads: (offset - prev_offset) == 0 | |
045a2529 | 451 | */ |
09cbfeaf | 452 | prev_offset = (unsigned long long)ra->prev_pos >> PAGE_SHIFT; |
af248a0c | 453 | if (offset - prev_offset <= 1UL) |
045a2529 WF |
454 | goto initial_readahead; |
455 | ||
10be0b37 WF |
456 | /* |
457 | * Query the page cache and look for the traces(cached history pages) | |
458 | * that a sequential stream would leave behind. | |
459 | */ | |
9491ae4a | 460 | if (try_context_readahead(mapping, ra, offset, req_size, max_pages)) |
10be0b37 WF |
461 | goto readit; |
462 | ||
045a2529 WF |
463 | /* |
464 | * standalone, small random read | |
465 | * Read as is, and do not pollute the readahead state. | |
466 | */ | |
467 | return __do_page_cache_readahead(mapping, filp, offset, req_size, 0); | |
468 | ||
469 | initial_readahead: | |
f9acc8c7 | 470 | ra->start = offset; |
9491ae4a | 471 | ra->size = get_init_ra_size(req_size, max_pages); |
f9acc8c7 | 472 | ra->async_size = ra->size > req_size ? ra->size - req_size : ra->size; |
122a21d1 | 473 | |
f9acc8c7 | 474 | readit: |
51daa88e WF |
475 | /* |
476 | * Will this read hit the readahead marker made by itself? | |
477 | * If so, trigger the readahead marker hit now, and merge | |
478 | * the resulted next readahead window into the current one. | |
dc30b96a | 479 | * Take care of maximum IO pages as above. |
51daa88e WF |
480 | */ |
481 | if (offset == ra->start && ra->size == ra->async_size) { | |
dc30b96a MS |
482 | add_pages = get_next_ra_size(ra, max_pages); |
483 | if (ra->size + add_pages <= max_pages) { | |
484 | ra->async_size = add_pages; | |
485 | ra->size += add_pages; | |
486 | } else { | |
487 | ra->size = max_pages; | |
488 | ra->async_size = max_pages >> 1; | |
489 | } | |
51daa88e WF |
490 | } |
491 | ||
122a21d1 FW |
492 | return ra_submit(ra, mapping, filp); |
493 | } | |
494 | ||
495 | /** | |
cf914a7d | 496 | * page_cache_sync_readahead - generic file readahead |
122a21d1 FW |
497 | * @mapping: address_space which holds the pagecache and I/O vectors |
498 | * @ra: file_ra_state which holds the readahead state | |
499 | * @filp: passed on to ->readpage() and ->readpages() | |
cf914a7d | 500 | * @offset: start offset into @mapping, in pagecache page-sized units |
122a21d1 | 501 | * @req_size: hint: total size of the read which the caller is performing in |
cf914a7d | 502 | * pagecache pages |
122a21d1 | 503 | * |
cf914a7d RR |
504 | * page_cache_sync_readahead() should be called when a cache miss happened: |
505 | * it will submit the read. The readahead logic may decide to piggyback more | |
506 | * pages onto the read request if access patterns suggest it will improve | |
507 | * performance. | |
122a21d1 | 508 | */ |
cf914a7d RR |
509 | void page_cache_sync_readahead(struct address_space *mapping, |
510 | struct file_ra_state *ra, struct file *filp, | |
511 | pgoff_t offset, unsigned long req_size) | |
122a21d1 FW |
512 | { |
513 | /* no read-ahead */ | |
514 | if (!ra->ra_pages) | |
cf914a7d RR |
515 | return; |
516 | ||
ca47e8c7 JB |
517 | if (blk_cgroup_congested()) |
518 | return; | |
519 | ||
0141450f | 520 | /* be dumb */ |
70655c06 | 521 | if (filp && (filp->f_mode & FMODE_RANDOM)) { |
0141450f WF |
522 | force_page_cache_readahead(mapping, filp, offset, req_size); |
523 | return; | |
524 | } | |
525 | ||
cf914a7d RR |
526 | /* do read-ahead */ |
527 | ondemand_readahead(mapping, ra, filp, false, offset, req_size); | |
528 | } | |
529 | EXPORT_SYMBOL_GPL(page_cache_sync_readahead); | |
530 | ||
531 | /** | |
532 | * page_cache_async_readahead - file readahead for marked pages | |
533 | * @mapping: address_space which holds the pagecache and I/O vectors | |
534 | * @ra: file_ra_state which holds the readahead state | |
535 | * @filp: passed on to ->readpage() and ->readpages() | |
536 | * @page: the page at @offset which has the PG_readahead flag set | |
537 | * @offset: start offset into @mapping, in pagecache page-sized units | |
538 | * @req_size: hint: total size of the read which the caller is performing in | |
539 | * pagecache pages | |
540 | * | |
bf8abe8b | 541 | * page_cache_async_readahead() should be called when a page is used which |
f7850d93 | 542 | * has the PG_readahead flag; this is a marker to suggest that the application |
cf914a7d | 543 | * has used up enough of the readahead window that we should start pulling in |
f7850d93 RD |
544 | * more pages. |
545 | */ | |
cf914a7d RR |
546 | void |
547 | page_cache_async_readahead(struct address_space *mapping, | |
548 | struct file_ra_state *ra, struct file *filp, | |
549 | struct page *page, pgoff_t offset, | |
550 | unsigned long req_size) | |
551 | { | |
552 | /* no read-ahead */ | |
553 | if (!ra->ra_pages) | |
554 | return; | |
555 | ||
556 | /* | |
557 | * Same bit is used for PG_readahead and PG_reclaim. | |
558 | */ | |
559 | if (PageWriteback(page)) | |
560 | return; | |
561 | ||
562 | ClearPageReadahead(page); | |
563 | ||
564 | /* | |
565 | * Defer asynchronous read-ahead on IO congestion. | |
566 | */ | |
703c2708 | 567 | if (inode_read_congested(mapping->host)) |
cf914a7d | 568 | return; |
122a21d1 | 569 | |
ca47e8c7 JB |
570 | if (blk_cgroup_congested()) |
571 | return; | |
572 | ||
122a21d1 | 573 | /* do read-ahead */ |
cf914a7d | 574 | ondemand_readahead(mapping, ra, filp, true, offset, req_size); |
122a21d1 | 575 | } |
cf914a7d | 576 | EXPORT_SYMBOL_GPL(page_cache_async_readahead); |
782182e5 CW |
577 | |
578 | static ssize_t | |
579 | do_readahead(struct address_space *mapping, struct file *filp, | |
580 | pgoff_t index, unsigned long nr) | |
581 | { | |
63d0f0a3 | 582 | if (!mapping || !mapping->a_ops) |
782182e5 CW |
583 | return -EINVAL; |
584 | ||
11bd969f RZ |
585 | /* |
586 | * Readahead doesn't make sense for DAX inodes, but we don't want it | |
587 | * to report a failure either. Instead, we just return success and | |
588 | * don't do any work. | |
589 | */ | |
590 | if (dax_mapping(mapping)) | |
591 | return 0; | |
592 | ||
58d5640e | 593 | return force_page_cache_readahead(mapping, filp, index, nr); |
782182e5 CW |
594 | } |
595 | ||
c7b95d51 | 596 | ssize_t ksys_readahead(int fd, loff_t offset, size_t count) |
782182e5 CW |
597 | { |
598 | ssize_t ret; | |
2903ff01 | 599 | struct fd f; |
782182e5 CW |
600 | |
601 | ret = -EBADF; | |
2903ff01 AV |
602 | f = fdget(fd); |
603 | if (f.file) { | |
604 | if (f.file->f_mode & FMODE_READ) { | |
605 | struct address_space *mapping = f.file->f_mapping; | |
09cbfeaf KS |
606 | pgoff_t start = offset >> PAGE_SHIFT; |
607 | pgoff_t end = (offset + count - 1) >> PAGE_SHIFT; | |
782182e5 | 608 | unsigned long len = end - start + 1; |
2903ff01 | 609 | ret = do_readahead(mapping, f.file, start, len); |
782182e5 | 610 | } |
2903ff01 | 611 | fdput(f); |
782182e5 CW |
612 | } |
613 | return ret; | |
614 | } | |
c7b95d51 DB |
615 | |
616 | SYSCALL_DEFINE3(readahead, int, fd, loff_t, offset, size_t, count) | |
617 | { | |
618 | return ksys_readahead(fd, offset, count); | |
619 | } |