Blame view
mm/readahead.c
16.3 KB
1da177e4c
|
1 2 3 4 5 |
/* * mm/readahead.c - address_space-level file readahead. * * Copyright (C) 2002, Linus Torvalds * |
e1f8e8744
|
6 |
* 09Apr2002 Andrew Morton |
1da177e4c
|
7 8 9 10 |
* Initial version. */ #include <linux/kernel.h> |
11bd969fd
|
11 |
#include <linux/dax.h> |
5a0e3ad6a
|
12 |
#include <linux/gfp.h> |
b95f1b31b
|
13 |
#include <linux/export.h> |
1da177e4c
|
14 15 |
#include <linux/blkdev.h> #include <linux/backing-dev.h> |
8bde37f08
|
16 |
#include <linux/task_io_accounting_ops.h> |
1da177e4c
|
17 |
#include <linux/pagevec.h> |
f5ff8422b
|
18 |
#include <linux/pagemap.h> |
782182e53
|
19 20 |
#include <linux/syscalls.h> #include <linux/file.h> |
d72ee9111
|
21 |
#include <linux/mm_inline.h> |
1da177e4c
|
22 |
|
29f175d12
|
23 |
#include "internal.h" |
1da177e4c
|
24 25 26 27 28 29 30 |
/* * Initialise a struct file's readahead state. Assumes that the caller has * memset *ra to zero. */ void file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping) { |
de1414a65
|
31 |
ra->ra_pages = inode_to_bdi(mapping->host)->ra_pages; |
f4e6b498d
|
32 |
ra->prev_pos = -1; |
1da177e4c
|
33 |
} |
d41cc702c
|
34 |
EXPORT_SYMBOL_GPL(file_ra_state_init); |
1da177e4c
|
35 |
|
03fb3d2af
|
36 37 |
/* * see if a page needs releasing upon read_cache_pages() failure |
266cf658e
|
38 39 40 41 |
* - the caller of read_cache_pages() may have set PG_private or PG_fscache * before calling, such as the NFS fs marking pages that are cached locally * on disk, thus we need to give the fs a chance to clean up in the event of * an error |
03fb3d2af
|
42 43 44 45 |
*/ static void read_cache_pages_invalidate_page(struct address_space *mapping, struct page *page) { |
266cf658e
|
46 |
if (page_has_private(page)) { |
03fb3d2af
|
47 48 49 |
if (!trylock_page(page)) BUG(); page->mapping = mapping; |
09cbfeaf1
|
50 |
do_invalidatepage(page, 0, PAGE_SIZE); |
03fb3d2af
|
51 52 53 |
page->mapping = NULL; unlock_page(page); } |
09cbfeaf1
|
54 |
put_page(page); |
03fb3d2af
|
55 56 57 58 59 60 61 62 63 64 65 |
} /* * release a list of pages, invalidating them first if need be */ static void read_cache_pages_invalidate_pages(struct address_space *mapping, struct list_head *pages) { struct page *victim; while (!list_empty(pages)) { |
c8ad6302c
|
66 |
victim = lru_to_page(pages); |
03fb3d2af
|
67 68 69 70 |
list_del(&victim->lru); read_cache_pages_invalidate_page(mapping, victim); } } |
1da177e4c
|
71 |
/** |
bd40cddae
|
72 |
* read_cache_pages - populate an address space with some pages & start reads against them |
1da177e4c
|
73 74 75 76 77 78 79 80 81 82 83 84 |
* @mapping: the address_space * @pages: The address of a list_head which contains the target pages. These * pages have their ->index populated and are otherwise uninitialised. * @filler: callback routine for filling a single page. * @data: private data for the callback routine. * * Hides the details of the LRU cache etc from the filesystems. */ int read_cache_pages(struct address_space *mapping, struct list_head *pages, int (*filler)(void *, struct page *), void *data) { struct page *page; |
1da177e4c
|
85 |
int ret = 0; |
1da177e4c
|
86 |
while (!list_empty(pages)) { |
c8ad6302c
|
87 |
page = lru_to_page(pages); |
1da177e4c
|
88 |
list_del(&page->lru); |
063d99b4f
|
89 |
if (add_to_page_cache_lru(page, mapping, page->index, |
8a5c743e3
|
90 |
readahead_gfp_mask(mapping))) { |
03fb3d2af
|
91 |
read_cache_pages_invalidate_page(mapping, page); |
1da177e4c
|
92 93 |
continue; } |
09cbfeaf1
|
94 |
put_page(page); |
eb2be1893
|
95 |
|
1da177e4c
|
96 |
ret = filler(data, page); |
eb2be1893
|
97 |
if (unlikely(ret)) { |
03fb3d2af
|
98 |
read_cache_pages_invalidate_pages(mapping, pages); |
1da177e4c
|
99 100 |
break; } |
09cbfeaf1
|
101 |
task_io_account_read(PAGE_SIZE); |
1da177e4c
|
102 |
} |
1da177e4c
|
103 104 105 106 107 108 |
return ret; } EXPORT_SYMBOL(read_cache_pages); static int read_pages(struct address_space *mapping, struct file *filp, |
8a5c743e3
|
109 |
struct list_head *pages, unsigned int nr_pages, gfp_t gfp) |
1da177e4c
|
110 |
{ |
5b417b187
|
111 |
struct blk_plug plug; |
1da177e4c
|
112 |
unsigned page_idx; |
994fc28c7
|
113 |
int ret; |
1da177e4c
|
114 |
|
5b417b187
|
115 |
blk_start_plug(&plug); |
1da177e4c
|
116 117 |
if (mapping->a_ops->readpages) { ret = mapping->a_ops->readpages(filp, mapping, pages, nr_pages); |
029e332ea
|
118 119 |
/* Clean up the remaining pages */ put_pages_list(pages); |
1da177e4c
|
120 121 |
goto out; } |
1da177e4c
|
122 |
for (page_idx = 0; page_idx < nr_pages; page_idx++) { |
c8ad6302c
|
123 |
struct page *page = lru_to_page(pages); |
1da177e4c
|
124 |
list_del(&page->lru); |
8a5c743e3
|
125 |
if (!add_to_page_cache_lru(page, mapping, page->index, gfp)) |
9f1a3cfcf
|
126 |
mapping->a_ops->readpage(filp, page); |
09cbfeaf1
|
127 |
put_page(page); |
1da177e4c
|
128 |
} |
994fc28c7
|
129 |
ret = 0; |
5b417b187
|
130 |
|
1da177e4c
|
131 |
out: |
5b417b187
|
132 |
blk_finish_plug(&plug); |
1da177e4c
|
133 134 135 136 |
return ret; } /* |
d30a11004
|
137 |
* __do_page_cache_readahead() actually reads a chunk of disk. It allocates all |
1da177e4c
|
138 139 140 141 142 |
* the pages first, then submits them all for I/O. This avoids the very bad * behaviour which would occur if page allocations are causing VM writeback. * We really don't want to intermingle reads and writes like that. * * Returns the number of pages requested, or the maximum amount of I/O allowed. |
1da177e4c
|
143 |
*/ |
29f175d12
|
144 |
int __do_page_cache_readahead(struct address_space *mapping, struct file *filp, |
46fc3e7b4
|
145 146 |
pgoff_t offset, unsigned long nr_to_read, unsigned long lookahead_size) |
1da177e4c
|
147 148 149 150 151 152 153 154 |
{ struct inode *inode = mapping->host; struct page *page; unsigned long end_index; /* The last page we want to read */ LIST_HEAD(page_pool); int page_idx; int ret = 0; loff_t isize = i_size_read(inode); |
8a5c743e3
|
155 |
gfp_t gfp_mask = readahead_gfp_mask(mapping); |
1da177e4c
|
156 157 158 |
if (isize == 0) goto out; |
09cbfeaf1
|
159 |
end_index = ((isize - 1) >> PAGE_SHIFT); |
1da177e4c
|
160 161 162 163 |
/* * Preallocate as many pages as we will need. */ |
1da177e4c
|
164 |
for (page_idx = 0; page_idx < nr_to_read; page_idx++) { |
7361f4d8c
|
165 |
pgoff_t page_offset = offset + page_idx; |
c743d96b6
|
166 |
|
1da177e4c
|
167 168 |
if (page_offset > end_index) break; |
001281881
|
169 |
rcu_read_lock(); |
1da177e4c
|
170 |
page = radix_tree_lookup(&mapping->page_tree, page_offset); |
001281881
|
171 |
rcu_read_unlock(); |
0cd6144aa
|
172 |
if (page && !radix_tree_exceptional_entry(page)) |
1da177e4c
|
173 |
continue; |
8a5c743e3
|
174 |
page = __page_cache_alloc(gfp_mask); |
1da177e4c
|
175 176 177 178 |
if (!page) break; page->index = page_offset; list_add(&page->lru, &page_pool); |
46fc3e7b4
|
179 180 |
if (page_idx == nr_to_read - lookahead_size) SetPageReadahead(page); |
1da177e4c
|
181 182 |
ret++; } |
1da177e4c
|
183 184 185 186 187 188 189 |
/* * Now start the IO. We ignore I/O errors - if the page is not * uptodate then the caller will launch readpage again, and * will then handle the error. */ if (ret) |
8a5c743e3
|
190 |
read_pages(mapping, filp, &page_pool, ret, gfp_mask); |
1da177e4c
|
191 192 193 194 195 196 197 198 199 200 |
BUG_ON(!list_empty(&page_pool)); out: return ret; } /* * Chunk the readahead into 2 megabyte units, so that we don't pin too much * memory at once. */ int force_page_cache_readahead(struct address_space *mapping, struct file *filp, |
9491ae4aa
|
201 |
pgoff_t offset, unsigned long nr_to_read) |
1da177e4c
|
202 |
{ |
9491ae4aa
|
203 204 205 |
struct backing_dev_info *bdi = inode_to_bdi(mapping->host); struct file_ra_state *ra = &filp->f_ra; unsigned long max_pages; |
1da177e4c
|
206 207 |
if (unlikely(!mapping->a_ops->readpage && !mapping->a_ops->readpages)) return -EINVAL; |
9491ae4aa
|
208 209 210 211 212 213 |
/* * If the request exceeds the readahead window, allow the read to * be up to the optimal hardware IO size */ max_pages = max_t(unsigned long, bdi->io_pages, ra->ra_pages); nr_to_read = min(nr_to_read, max_pages); |
1da177e4c
|
214 215 |
while (nr_to_read) { int err; |
09cbfeaf1
|
216 |
unsigned long this_chunk = (2 * 1024 * 1024) / PAGE_SIZE; |
1da177e4c
|
217 218 219 220 |
if (this_chunk > nr_to_read) this_chunk = nr_to_read; err = __do_page_cache_readahead(mapping, filp, |
46fc3e7b4
|
221 |
offset, this_chunk, 0); |
58d5640eb
|
222 223 |
if (err < 0) return err; |
1da177e4c
|
224 225 226 |
offset += this_chunk; nr_to_read -= this_chunk; } |
58d5640eb
|
227 |
return 0; |
1da177e4c
|
228 |
} |
5ce1110b9
|
229 |
/* |
c743d96b6
|
230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 |
* Set the initial window size, round to next power of 2 and square * for small size, x 4 for medium, and x 2 for large * for 128k (32 page) max ra * 1-8 page = 32k initial, > 8 page = 128k initial */ static unsigned long get_init_ra_size(unsigned long size, unsigned long max) { unsigned long newsize = roundup_pow_of_two(size); if (newsize <= max / 32) newsize = newsize * 4; else if (newsize <= max / 4) newsize = newsize * 2; else newsize = max; return newsize; } /* |
122a21d11
|
250 251 252 |
* Get the previous window size, ramp it up, and * return it as the new window size. */ |
c743d96b6
|
253 |
static unsigned long get_next_ra_size(struct file_ra_state *ra, |
122a21d11
|
254 255 |
unsigned long max) { |
f9acc8c7b
|
256 |
unsigned long cur = ra->size; |
122a21d11
|
257 258 259 |
unsigned long newsize; if (cur < max / 16) |
c743d96b6
|
260 |
newsize = 4 * cur; |
122a21d11
|
261 |
else |
c743d96b6
|
262 |
newsize = 2 * cur; |
122a21d11
|
263 264 265 266 267 268 269 270 271 272 |
return min(newsize, max); } /* * On-demand readahead design. * * The fields in struct file_ra_state represent the most-recently-executed * readahead attempt: * |
f9acc8c7b
|
273 274 275 276 |
* |<----- async_size ---------| * |------------------- size -------------------->| * |==================#===========================| * ^start ^page marked with PG_readahead |
122a21d11
|
277 278 279 280 |
* * To overlap application thinking time and disk I/O time, we do * `readahead pipelining': Do not wait until the application consumed all * readahead pages and stalled on the missing page at readahead_index; |
f9acc8c7b
|
281 282 283 |
* Instead, submit an asynchronous readahead I/O as soon as there are * only async_size pages left in the readahead window. Normally async_size * will be equal to size, for maximum pipelining. |
122a21d11
|
284 285 286 |
* * In interleaved sequential reads, concurrent streams on the same fd can * be invalidating each other's readahead state. So we flag the new readahead |
f9acc8c7b
|
287 |
* page at (start+size-async_size) with PG_readahead, and use it as readahead |
122a21d11
|
288 289 290 |
* indicator. The flag won't be set on already cached pages, to avoid the * readahead-for-nothing fuss, saving pointless page cache lookups. * |
f4e6b498d
|
291 |
* prev_pos tracks the last visited byte in the _previous_ read request. |
122a21d11
|
292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 |
* It should be maintained by the caller, and will be used for detecting * small random reads. Note that the readahead algorithm checks loosely * for sequential patterns. Hence interleaved reads might be served as * sequential ones. * * There is a special-case: if the first page which the application tries to * read happens to be the first page of the file, it is assumed that a linear * read is about to happen and the window is immediately set to the initial size * based on I/O request size and the max_readahead. * * The code ramps up the readahead size aggressively at first, but slow down as * it approaches max_readhead. */ /* |
10be0b372
|
307 308 309 310 311 312 |
* Count contiguously cached pages from @offset-1 to @offset-@max, * this count is a conservative estimation of * - length of the sequential read sequence, or * - thrashing threshold in memory tight systems */ static pgoff_t count_history_pages(struct address_space *mapping, |
10be0b372
|
313 314 315 316 317 |
pgoff_t offset, unsigned long max) { pgoff_t head; rcu_read_lock(); |
e7b563bb2
|
318 |
head = page_cache_prev_hole(mapping, offset - 1, max); |
10be0b372
|
319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 |
rcu_read_unlock(); return offset - 1 - head; } /* * page cache context based read-ahead */ static int try_context_readahead(struct address_space *mapping, struct file_ra_state *ra, pgoff_t offset, unsigned long req_size, unsigned long max) { pgoff_t size; |
3e2faa085
|
334 |
size = count_history_pages(mapping, offset, max); |
10be0b372
|
335 336 |
/* |
2cad40180
|
337 |
* not enough history pages: |
10be0b372
|
338 339 |
* it could be a random read */ |
2cad40180
|
340 |
if (size <= req_size) |
10be0b372
|
341 342 343 344 345 346 347 348 349 350 |
return 0; /* * starts from beginning of file: * it is a strong indication of long-run stream (or whole-file-read) */ if (size >= offset) size *= 2; ra->start = offset; |
2cad40180
|
351 352 |
ra->size = min(size + req_size, max); ra->async_size = 1; |
10be0b372
|
353 354 355 356 357 |
return 1; } /* |
122a21d11
|
358 359 360 361 362 |
* A minimal readahead algorithm for trivial sequential/random reads. */ static unsigned long ondemand_readahead(struct address_space *mapping, struct file_ra_state *ra, struct file *filp, |
cf914a7d6
|
363 |
bool hit_readahead_marker, pgoff_t offset, |
122a21d11
|
364 365 |
unsigned long req_size) { |
9491ae4aa
|
366 367 |
struct backing_dev_info *bdi = inode_to_bdi(mapping->host); unsigned long max_pages = ra->ra_pages; |
cf12d0f9c
|
368 |
unsigned long add_pages; |
af248a0c6
|
369 |
pgoff_t prev_offset; |
045a2529a
|
370 371 |
/* |
9491ae4aa
|
372 373 374 375 376 377 378 |
* If the request exceeds the readahead window, allow the read to * be up to the optimal hardware IO size */ if (req_size > max_pages && bdi->io_pages > max_pages) max_pages = min(req_size, bdi->io_pages); /* |
045a2529a
|
379 380 381 382 |
* start of file */ if (!offset) goto initial_readahead; |
122a21d11
|
383 384 |
/* |
f9acc8c7b
|
385 |
* It's the expected callback offset, assume sequential access. |
122a21d11
|
386 387 |
* Ramp up sizes, and push forward the readahead window. */ |
045a2529a
|
388 389 |
if ((offset == (ra->start + ra->size - ra->async_size) || offset == (ra->start + ra->size))) { |
f9acc8c7b
|
390 |
ra->start += ra->size; |
9491ae4aa
|
391 |
ra->size = get_next_ra_size(ra, max_pages); |
f9acc8c7b
|
392 393 |
ra->async_size = ra->size; goto readit; |
122a21d11
|
394 |
} |
122a21d11
|
395 |
/* |
6b10c6c9f
|
396 397 398 399 400 401 402 |
* Hit a marked page without valid readahead state. * E.g. interleaved reads. * Query the pagecache for async_size, which normally equals to * readahead size. Ramp it up and use it as the new readahead size. */ if (hit_readahead_marker) { pgoff_t start; |
30002ed2e
|
403 |
rcu_read_lock(); |
9491ae4aa
|
404 |
start = page_cache_next_hole(mapping, offset + 1, max_pages); |
30002ed2e
|
405 |
rcu_read_unlock(); |
6b10c6c9f
|
406 |
|
9491ae4aa
|
407 |
if (!start || start - offset > max_pages) |
6b10c6c9f
|
408 409 410 411 |
return 0; ra->start = start; ra->size = start - offset; /* old async_size */ |
160334a0c
|
412 |
ra->size += req_size; |
9491ae4aa
|
413 |
ra->size = get_next_ra_size(ra, max_pages); |
6b10c6c9f
|
414 415 416 417 418 |
ra->async_size = ra->size; goto readit; } /* |
045a2529a
|
419 |
* oversize read |
122a21d11
|
420 |
*/ |
9491ae4aa
|
421 |
if (req_size > max_pages) |
045a2529a
|
422 423 424 425 |
goto initial_readahead; /* * sequential cache miss |
af248a0c6
|
426 427 |
* trivial case: (offset - prev_offset) == 1 * unaligned reads: (offset - prev_offset) == 0 |
045a2529a
|
428 |
*/ |
09cbfeaf1
|
429 |
prev_offset = (unsigned long long)ra->prev_pos >> PAGE_SHIFT; |
af248a0c6
|
430 |
if (offset - prev_offset <= 1UL) |
045a2529a
|
431 432 433 |
goto initial_readahead; /* |
10be0b372
|
434 435 436 |
* Query the page cache and look for the traces(cached history pages) * that a sequential stream would leave behind. */ |
9491ae4aa
|
437 |
if (try_context_readahead(mapping, ra, offset, req_size, max_pages)) |
10be0b372
|
438 439 440 |
goto readit; /* |
045a2529a
|
441 442 443 444 445 446 |
* standalone, small random read * Read as is, and do not pollute the readahead state. */ return __do_page_cache_readahead(mapping, filp, offset, req_size, 0); initial_readahead: |
f9acc8c7b
|
447 |
ra->start = offset; |
9491ae4aa
|
448 |
ra->size = get_init_ra_size(req_size, max_pages); |
f9acc8c7b
|
449 |
ra->async_size = ra->size > req_size ? ra->size - req_size : ra->size; |
122a21d11
|
450 |
|
f9acc8c7b
|
451 |
readit: |
51daa88eb
|
452 453 454 455 |
/* * Will this read hit the readahead marker made by itself? * If so, trigger the readahead marker hit now, and merge * the resulted next readahead window into the current one. |
cf12d0f9c
|
456 |
* Take care of maximum IO pages as above. |
51daa88eb
|
457 458 |
*/ if (offset == ra->start && ra->size == ra->async_size) { |
cf12d0f9c
|
459 460 461 462 463 464 465 466 |
add_pages = get_next_ra_size(ra, max_pages); if (ra->size + add_pages <= max_pages) { ra->async_size = add_pages; ra->size += add_pages; } else { ra->size = max_pages; ra->async_size = max_pages >> 1; } |
51daa88eb
|
467 |
} |
122a21d11
|
468 469 470 471 |
return ra_submit(ra, mapping, filp); } /** |
cf914a7d6
|
472 |
* page_cache_sync_readahead - generic file readahead |
122a21d11
|
473 474 475 |
* @mapping: address_space which holds the pagecache and I/O vectors * @ra: file_ra_state which holds the readahead state * @filp: passed on to ->readpage() and ->readpages() |
cf914a7d6
|
476 |
* @offset: start offset into @mapping, in pagecache page-sized units |
122a21d11
|
477 |
* @req_size: hint: total size of the read which the caller is performing in |
cf914a7d6
|
478 |
* pagecache pages |
122a21d11
|
479 |
* |
cf914a7d6
|
480 481 482 483 |
* page_cache_sync_readahead() should be called when a cache miss happened: * it will submit the read. The readahead logic may decide to piggyback more * pages onto the read request if access patterns suggest it will improve * performance. |
122a21d11
|
484 |
*/ |
cf914a7d6
|
485 486 487 |
void page_cache_sync_readahead(struct address_space *mapping, struct file_ra_state *ra, struct file *filp, pgoff_t offset, unsigned long req_size) |
122a21d11
|
488 489 490 |
{ /* no read-ahead */ if (!ra->ra_pages) |
cf914a7d6
|
491 |
return; |
0141450f6
|
492 |
/* be dumb */ |
70655c06b
|
493 |
if (filp && (filp->f_mode & FMODE_RANDOM)) { |
0141450f6
|
494 495 496 |
force_page_cache_readahead(mapping, filp, offset, req_size); return; } |
cf914a7d6
|
497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 |
/* do read-ahead */ ondemand_readahead(mapping, ra, filp, false, offset, req_size); } EXPORT_SYMBOL_GPL(page_cache_sync_readahead); /** * page_cache_async_readahead - file readahead for marked pages * @mapping: address_space which holds the pagecache and I/O vectors * @ra: file_ra_state which holds the readahead state * @filp: passed on to ->readpage() and ->readpages() * @page: the page at @offset which has the PG_readahead flag set * @offset: start offset into @mapping, in pagecache page-sized units * @req_size: hint: total size of the read which the caller is performing in * pagecache pages * |
bf8abe8b9
|
512 |
* page_cache_async_readahead() should be called when a page is used which |
f7850d932
|
513 |
* has the PG_readahead flag; this is a marker to suggest that the application |
cf914a7d6
|
514 |
* has used up enough of the readahead window that we should start pulling in |
f7850d932
|
515 516 |
* more pages. */ |
cf914a7d6
|
517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 |
void page_cache_async_readahead(struct address_space *mapping, struct file_ra_state *ra, struct file *filp, struct page *page, pgoff_t offset, unsigned long req_size) { /* no read-ahead */ if (!ra->ra_pages) return; /* * Same bit is used for PG_readahead and PG_reclaim. */ if (PageWriteback(page)) return; ClearPageReadahead(page); /* * Defer asynchronous read-ahead on IO congestion. */ |
703c27088
|
538 |
if (inode_read_congested(mapping->host)) |
cf914a7d6
|
539 |
return; |
122a21d11
|
540 541 |
/* do read-ahead */ |
cf914a7d6
|
542 |
ondemand_readahead(mapping, ra, filp, true, offset, req_size); |
122a21d11
|
543 |
} |
cf914a7d6
|
544 |
EXPORT_SYMBOL_GPL(page_cache_async_readahead); |
782182e53
|
545 546 547 548 549 |
static ssize_t do_readahead(struct address_space *mapping, struct file *filp, pgoff_t index, unsigned long nr) { |
63d0f0a3c
|
550 |
if (!mapping || !mapping->a_ops) |
782182e53
|
551 |
return -EINVAL; |
11bd969fd
|
552 553 554 555 556 557 558 |
/* * Readahead doesn't make sense for DAX inodes, but we don't want it * to report a failure either. Instead, we just return success and * don't do any work. */ if (dax_mapping(mapping)) return 0; |
58d5640eb
|
559 |
return force_page_cache_readahead(mapping, filp, index, nr); |
782182e53
|
560 |
} |
4a0fd5bf0
|
561 |
SYSCALL_DEFINE3(readahead, int, fd, loff_t, offset, size_t, count) |
782182e53
|
562 563 |
{ ssize_t ret; |
2903ff019
|
564 |
struct fd f; |
782182e53
|
565 566 |
ret = -EBADF; |
2903ff019
|
567 568 569 570 |
f = fdget(fd); if (f.file) { if (f.file->f_mode & FMODE_READ) { struct address_space *mapping = f.file->f_mapping; |
09cbfeaf1
|
571 572 |
pgoff_t start = offset >> PAGE_SHIFT; pgoff_t end = (offset + count - 1) >> PAGE_SHIFT; |
782182e53
|
573 |
unsigned long len = end - start + 1; |
2903ff019
|
574 |
ret = do_readahead(mapping, f.file, start, len); |
782182e53
|
575 |
} |
2903ff019
|
576 |
fdput(f); |
782182e53
|
577 578 579 |
} return ret; } |