1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * mm/readahead.c - address_space-level file readahead.
4 *
5 * Copyright (C) 2002, Linus Torvalds
6 *
7 * 09Apr2002 Andrew Morton
8 * Initial version.
9 */
10
11 #include <linux/kernel.h>
12 #include <linux/dax.h>
13 #include <linux/gfp.h>
14 #include <linux/export.h>
15 #include <linux/blkdev.h>
16 #include <linux/backing-dev.h>
17 #include <linux/task_io_accounting_ops.h>
18 #include <linux/pagevec.h>
19 #include <linux/pagemap.h>
20 #include <linux/syscalls.h>
21 #include <linux/file.h>
22 #include <linux/mm_inline.h>
23 #include <linux/blk-cgroup.h>
24 #include <linux/fadvise.h>
25 #include <linux/sched/mm.h>
26
27 #include "internal.h"
28
29 /*
30 * Initialise a struct file's readahead state. Assumes that the caller has
31 * memset *ra to zero.
32 */
33 void
file_ra_state_init(struct file_ra_state * ra,struct address_space * mapping)34 file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping)
35 {
36 ra->ra_pages = inode_to_bdi(mapping->host)->ra_pages;
37 ra->prev_pos = -1;
38 }
39 EXPORT_SYMBOL_GPL(file_ra_state_init);
40
41 /*
42 * see if a page needs releasing upon read_cache_pages() failure
43 * - the caller of read_cache_pages() may have set PG_private or PG_fscache
44 * before calling, such as the NFS fs marking pages that are cached locally
45 * on disk, thus we need to give the fs a chance to clean up in the event of
46 * an error
47 */
read_cache_pages_invalidate_page(struct address_space * mapping,struct page * page)48 static void read_cache_pages_invalidate_page(struct address_space *mapping,
49 struct page *page)
50 {
51 if (page_has_private(page)) {
52 if (!trylock_page(page))
53 BUG();
54 page->mapping = mapping;
55 do_invalidatepage(page, 0, PAGE_SIZE);
56 page->mapping = NULL;
57 unlock_page(page);
58 }
59 put_page(page);
60 }
61
62 /*
63 * release a list of pages, invalidating them first if need be
64 */
read_cache_pages_invalidate_pages(struct address_space * mapping,struct list_head * pages)65 static void read_cache_pages_invalidate_pages(struct address_space *mapping,
66 struct list_head *pages)
67 {
68 struct page *victim;
69
70 while (!list_empty(pages)) {
71 victim = lru_to_page(pages);
72 list_del(&victim->lru);
73 read_cache_pages_invalidate_page(mapping, victim);
74 }
75 }
76
77 /**
78 * read_cache_pages - populate an address space with some pages & start reads against them
79 * @mapping: the address_space
80 * @pages: The address of a list_head which contains the target pages. These
81 * pages have their ->index populated and are otherwise uninitialised.
82 * @filler: callback routine for filling a single page.
83 * @data: private data for the callback routine.
84 *
85 * Hides the details of the LRU cache etc from the filesystems.
86 *
87 * Returns: %0 on success, error return by @filler otherwise
88 */
read_cache_pages(struct address_space * mapping,struct list_head * pages,int (* filler)(void *,struct page *),void * data)89 int read_cache_pages(struct address_space *mapping, struct list_head *pages,
90 int (*filler)(void *, struct page *), void *data)
91 {
92 struct page *page;
93 int ret = 0;
94
95 while (!list_empty(pages)) {
96 page = lru_to_page(pages);
97 list_del(&page->lru);
98 if (add_to_page_cache_lru(page, mapping, page->index,
99 readahead_gfp_mask(mapping))) {
100 read_cache_pages_invalidate_page(mapping, page);
101 continue;
102 }
103 put_page(page);
104
105 ret = filler(data, page);
106 if (unlikely(ret)) {
107 read_cache_pages_invalidate_pages(mapping, pages);
108 break;
109 }
110 task_io_account_read(PAGE_SIZE);
111 }
112 return ret;
113 }
114
115 EXPORT_SYMBOL(read_cache_pages);
116
read_pages(struct readahead_control * rac,struct list_head * pages,bool skip_page)117 static void read_pages(struct readahead_control *rac, struct list_head *pages,
118 bool skip_page)
119 {
120 const struct address_space_operations *aops = rac->mapping->a_ops;
121 struct page *page;
122 struct blk_plug plug;
123
124 if (!readahead_count(rac))
125 goto out;
126
127 blk_start_plug(&plug);
128
129 if (aops->readahead) {
130 aops->readahead(rac);
131 /* Clean up the remaining pages */
132 while ((page = readahead_page(rac))) {
133 unlock_page(page);
134 put_page(page);
135 }
136 } else if (aops->readpages) {
137 aops->readpages(rac->file, rac->mapping, pages,
138 readahead_count(rac));
139 /* Clean up the remaining pages */
140 put_pages_list(pages);
141 rac->_index += rac->_nr_pages;
142 rac->_nr_pages = 0;
143 } else {
144 while ((page = readahead_page(rac))) {
145 aops->readpage(rac->file, page);
146 put_page(page);
147 }
148 }
149
150 blk_finish_plug(&plug);
151
152 BUG_ON(!list_empty(pages));
153 BUG_ON(readahead_count(rac));
154
155 out:
156 if (skip_page)
157 rac->_index++;
158 }
159
160 /**
161 * page_cache_ra_unbounded - Start unchecked readahead.
162 * @ractl: Readahead control.
163 * @nr_to_read: The number of pages to read.
164 * @lookahead_size: Where to start the next readahead.
165 *
166 * This function is for filesystems to call when they want to start
167 * readahead beyond a file's stated i_size. This is almost certainly
168 * not the function you want to call. Use page_cache_async_readahead()
169 * or page_cache_sync_readahead() instead.
170 *
171 * Context: File is referenced by caller. Mutexes may be held by caller.
172 * May sleep, but will not reenter filesystem to reclaim memory.
173 */
page_cache_ra_unbounded(struct readahead_control * ractl,unsigned long nr_to_read,unsigned long lookahead_size)174 void page_cache_ra_unbounded(struct readahead_control *ractl,
175 unsigned long nr_to_read, unsigned long lookahead_size)
176 {
177 struct address_space *mapping = ractl->mapping;
178 unsigned long index = readahead_index(ractl);
179 LIST_HEAD(page_pool);
180 gfp_t gfp_mask = readahead_gfp_mask(mapping);
181 unsigned long i;
182
183 /*
184 * Partway through the readahead operation, we will have added
185 * locked pages to the page cache, but will not yet have submitted
186 * them for I/O. Adding another page may need to allocate memory,
187 * which can trigger memory reclaim. Telling the VM we're in
188 * the middle of a filesystem operation will cause it to not
189 * touch file-backed pages, preventing a deadlock. Most (all?)
190 * filesystems already specify __GFP_NOFS in their mapping's
191 * gfp_mask, but let's be explicit here.
192 */
193 unsigned int nofs = memalloc_nofs_save();
194
195 filemap_invalidate_lock_shared(mapping);
196 /*
197 * Preallocate as many pages as we will need.
198 */
199 for (i = 0; i < nr_to_read; i++) {
200 struct page *page = xa_load(&mapping->i_pages, index + i);
201
202 if (page && !xa_is_value(page)) {
203 /*
204 * Page already present? Kick off the current batch
205 * of contiguous pages before continuing with the
206 * next batch. This page may be the one we would
207 * have intended to mark as Readahead, but we don't
208 * have a stable reference to this page, and it's
209 * not worth getting one just for that.
210 */
211 read_pages(ractl, &page_pool, true);
212 i = ractl->_index + ractl->_nr_pages - index - 1;
213 continue;
214 }
215
216 page = __page_cache_alloc(gfp_mask);
217 if (!page)
218 break;
219 if (mapping->a_ops->readpages) {
220 page->index = index + i;
221 list_add(&page->lru, &page_pool);
222 } else if (add_to_page_cache_lru(page, mapping, index + i,
223 gfp_mask) < 0) {
224 put_page(page);
225 read_pages(ractl, &page_pool, true);
226 i = ractl->_index + ractl->_nr_pages - index - 1;
227 continue;
228 }
229 if (i == nr_to_read - lookahead_size)
230 SetPageReadahead(page);
231 ractl->_nr_pages++;
232 }
233
234 /*
235 * Now start the IO. We ignore I/O errors - if the page is not
236 * uptodate then the caller will launch readpage again, and
237 * will then handle the error.
238 */
239 read_pages(ractl, &page_pool, false);
240 filemap_invalidate_unlock_shared(mapping);
241 memalloc_nofs_restore(nofs);
242 }
243 EXPORT_SYMBOL_GPL(page_cache_ra_unbounded);
244
245 /*
246 * do_page_cache_ra() actually reads a chunk of disk. It allocates
247 * the pages first, then submits them for I/O. This avoids the very bad
248 * behaviour which would occur if page allocations are causing VM writeback.
249 * We really don't want to intermingle reads and writes like that.
250 */
do_page_cache_ra(struct readahead_control * ractl,unsigned long nr_to_read,unsigned long lookahead_size)251 void do_page_cache_ra(struct readahead_control *ractl,
252 unsigned long nr_to_read, unsigned long lookahead_size)
253 {
254 struct inode *inode = ractl->mapping->host;
255 unsigned long index = readahead_index(ractl);
256 loff_t isize = i_size_read(inode);
257 pgoff_t end_index; /* The last page we want to read */
258
259 if (isize == 0)
260 return;
261
262 end_index = (isize - 1) >> PAGE_SHIFT;
263 if (index > end_index)
264 return;
265 /* Don't read past the page containing the last byte of the file */
266 if (nr_to_read > end_index - index)
267 nr_to_read = end_index - index + 1;
268
269 page_cache_ra_unbounded(ractl, nr_to_read, lookahead_size);
270 }
271
272 /*
273 * Chunk the readahead into 2 megabyte units, so that we don't pin too much
274 * memory at once.
275 */
force_page_cache_ra(struct readahead_control * ractl,unsigned long nr_to_read)276 void force_page_cache_ra(struct readahead_control *ractl,
277 unsigned long nr_to_read)
278 {
279 struct address_space *mapping = ractl->mapping;
280 struct file_ra_state *ra = ractl->ra;
281 struct backing_dev_info *bdi = inode_to_bdi(mapping->host);
282 unsigned long max_pages, index;
283
284 if (unlikely(!mapping->a_ops->readpage && !mapping->a_ops->readpages &&
285 !mapping->a_ops->readahead))
286 return;
287
288 /*
289 * If the request exceeds the readahead window, allow the read to
290 * be up to the optimal hardware IO size
291 */
292 index = readahead_index(ractl);
293 max_pages = max_t(unsigned long, bdi->io_pages, ra->ra_pages);
294 nr_to_read = min_t(unsigned long, nr_to_read, max_pages);
295 while (nr_to_read) {
296 unsigned long this_chunk = (2 * 1024 * 1024) / PAGE_SIZE;
297
298 if (this_chunk > nr_to_read)
299 this_chunk = nr_to_read;
300 ractl->_index = index;
301 do_page_cache_ra(ractl, this_chunk, 0);
302
303 index += this_chunk;
304 nr_to_read -= this_chunk;
305 }
306 }
307
308 /*
309 * Set the initial window size, round to next power of 2 and square
310 * for small size, x 4 for medium, and x 2 for large
311 * for 128k (32 page) max ra
312 * 1-8 page = 32k initial, > 8 page = 128k initial
313 */
get_init_ra_size(unsigned long size,unsigned long max)314 static unsigned long get_init_ra_size(unsigned long size, unsigned long max)
315 {
316 unsigned long newsize = roundup_pow_of_two(size);
317
318 if (newsize <= max / 32)
319 newsize = newsize * 4;
320 else if (newsize <= max / 4)
321 newsize = newsize * 2;
322 else
323 newsize = max;
324
325 return newsize;
326 }
327
328 /*
329 * Get the previous window size, ramp it up, and
330 * return it as the new window size.
331 */
get_next_ra_size(struct file_ra_state * ra,unsigned long max)332 static unsigned long get_next_ra_size(struct file_ra_state *ra,
333 unsigned long max)
334 {
335 unsigned long cur = ra->size;
336
337 if (cur < max / 16)
338 return 4 * cur;
339 if (cur <= max / 2)
340 return 2 * cur;
341 return max;
342 }
343
344 /*
345 * On-demand readahead design.
346 *
347 * The fields in struct file_ra_state represent the most-recently-executed
348 * readahead attempt:
349 *
350 * |<----- async_size ---------|
351 * |------------------- size -------------------->|
352 * |==================#===========================|
353 * ^start ^page marked with PG_readahead
354 *
355 * To overlap application thinking time and disk I/O time, we do
356 * `readahead pipelining': Do not wait until the application consumed all
357 * readahead pages and stalled on the missing page at readahead_index;
358 * Instead, submit an asynchronous readahead I/O as soon as there are
359 * only async_size pages left in the readahead window. Normally async_size
360 * will be equal to size, for maximum pipelining.
361 *
362 * In interleaved sequential reads, concurrent streams on the same fd can
363 * be invalidating each other's readahead state. So we flag the new readahead
364 * page at (start+size-async_size) with PG_readahead, and use it as readahead
365 * indicator. The flag won't be set on already cached pages, to avoid the
366 * readahead-for-nothing fuss, saving pointless page cache lookups.
367 *
368 * prev_pos tracks the last visited byte in the _previous_ read request.
369 * It should be maintained by the caller, and will be used for detecting
370 * small random reads. Note that the readahead algorithm checks loosely
371 * for sequential patterns. Hence interleaved reads might be served as
372 * sequential ones.
373 *
374 * There is a special-case: if the first page which the application tries to
375 * read happens to be the first page of the file, it is assumed that a linear
376 * read is about to happen and the window is immediately set to the initial size
377 * based on I/O request size and the max_readahead.
378 *
379 * The code ramps up the readahead size aggressively at first, but slow down as
380 * it approaches max_readhead.
381 */
382
383 /*
384 * Count contiguously cached pages from @index-1 to @index-@max,
385 * this count is a conservative estimation of
386 * - length of the sequential read sequence, or
387 * - thrashing threshold in memory tight systems
388 */
count_history_pages(struct address_space * mapping,pgoff_t index,unsigned long max)389 static pgoff_t count_history_pages(struct address_space *mapping,
390 pgoff_t index, unsigned long max)
391 {
392 pgoff_t head;
393
394 rcu_read_lock();
395 head = page_cache_prev_miss(mapping, index - 1, max);
396 rcu_read_unlock();
397
398 return index - 1 - head;
399 }
400
401 /*
402 * page cache context based read-ahead
403 */
try_context_readahead(struct address_space * mapping,struct file_ra_state * ra,pgoff_t index,unsigned long req_size,unsigned long max)404 static int try_context_readahead(struct address_space *mapping,
405 struct file_ra_state *ra,
406 pgoff_t index,
407 unsigned long req_size,
408 unsigned long max)
409 {
410 pgoff_t size;
411
412 size = count_history_pages(mapping, index, max);
413
414 /*
415 * not enough history pages:
416 * it could be a random read
417 */
418 if (size <= req_size)
419 return 0;
420
421 /*
422 * starts from beginning of file:
423 * it is a strong indication of long-run stream (or whole-file-read)
424 */
425 if (size >= index)
426 size *= 2;
427
428 ra->start = index;
429 ra->size = min(size + req_size, max);
430 ra->async_size = 1;
431
432 return 1;
433 }
434
435 /*
436 * A minimal readahead algorithm for trivial sequential/random reads.
437 */
ondemand_readahead(struct readahead_control * ractl,bool hit_readahead_marker,unsigned long req_size)438 static void ondemand_readahead(struct readahead_control *ractl,
439 bool hit_readahead_marker, unsigned long req_size)
440 {
441 struct backing_dev_info *bdi = inode_to_bdi(ractl->mapping->host);
442 struct file_ra_state *ra = ractl->ra;
443 unsigned long max_pages = ra->ra_pages;
444 unsigned long add_pages;
445 unsigned long index = readahead_index(ractl);
446 pgoff_t prev_index;
447
448 /*
449 * If the request exceeds the readahead window, allow the read to
450 * be up to the optimal hardware IO size
451 */
452 if (req_size > max_pages && bdi->io_pages > max_pages)
453 max_pages = min(req_size, bdi->io_pages);
454
455 /*
456 * start of file
457 */
458 if (!index)
459 goto initial_readahead;
460
461 /*
462 * It's the expected callback index, assume sequential access.
463 * Ramp up sizes, and push forward the readahead window.
464 */
465 if ((index == (ra->start + ra->size - ra->async_size) ||
466 index == (ra->start + ra->size))) {
467 ra->start += ra->size;
468 ra->size = get_next_ra_size(ra, max_pages);
469 ra->async_size = ra->size;
470 goto readit;
471 }
472
473 /*
474 * Hit a marked page without valid readahead state.
475 * E.g. interleaved reads.
476 * Query the pagecache for async_size, which normally equals to
477 * readahead size. Ramp it up and use it as the new readahead size.
478 */
479 if (hit_readahead_marker) {
480 pgoff_t start;
481
482 rcu_read_lock();
483 start = page_cache_next_miss(ractl->mapping, index + 1,
484 max_pages);
485 rcu_read_unlock();
486
487 if (!start || start - index > max_pages)
488 return;
489
490 ra->start = start;
491 ra->size = start - index; /* old async_size */
492 ra->size += req_size;
493 ra->size = get_next_ra_size(ra, max_pages);
494 ra->async_size = ra->size;
495 goto readit;
496 }
497
498 /*
499 * oversize read
500 */
501 if (req_size > max_pages)
502 goto initial_readahead;
503
504 /*
505 * sequential cache miss
506 * trivial case: (index - prev_index) == 1
507 * unaligned reads: (index - prev_index) == 0
508 */
509 prev_index = (unsigned long long)ra->prev_pos >> PAGE_SHIFT;
510 if (index - prev_index <= 1UL)
511 goto initial_readahead;
512
513 /*
514 * Query the page cache and look for the traces(cached history pages)
515 * that a sequential stream would leave behind.
516 */
517 if (try_context_readahead(ractl->mapping, ra, index, req_size,
518 max_pages))
519 goto readit;
520
521 /*
522 * standalone, small random read
523 * Read as is, and do not pollute the readahead state.
524 */
525 do_page_cache_ra(ractl, req_size, 0);
526 return;
527
528 initial_readahead:
529 ra->start = index;
530 ra->size = get_init_ra_size(req_size, max_pages);
531 ra->async_size = ra->size > req_size ? ra->size - req_size : ra->size;
532
533 readit:
534 /*
535 * Will this read hit the readahead marker made by itself?
536 * If so, trigger the readahead marker hit now, and merge
537 * the resulted next readahead window into the current one.
538 * Take care of maximum IO pages as above.
539 */
540 if (index == ra->start && ra->size == ra->async_size) {
541 add_pages = get_next_ra_size(ra, max_pages);
542 if (ra->size + add_pages <= max_pages) {
543 ra->async_size = add_pages;
544 ra->size += add_pages;
545 } else {
546 ra->size = max_pages;
547 ra->async_size = max_pages >> 1;
548 }
549 }
550
551 ractl->_index = ra->start;
552 do_page_cache_ra(ractl, ra->size, ra->async_size);
553 }
554
page_cache_sync_ra(struct readahead_control * ractl,unsigned long req_count)555 void page_cache_sync_ra(struct readahead_control *ractl,
556 unsigned long req_count)
557 {
558 bool do_forced_ra = ractl->file && (ractl->file->f_mode & FMODE_RANDOM);
559
560 /*
561 * Even if read-ahead is disabled, issue this request as read-ahead
562 * as we'll need it to satisfy the requested range. The forced
563 * read-ahead will do the right thing and limit the read to just the
564 * requested range, which we'll set to 1 page for this case.
565 */
566 if (!ractl->ra->ra_pages || blk_cgroup_congested()) {
567 if (!ractl->file)
568 return;
569 req_count = 1;
570 do_forced_ra = true;
571 }
572
573 /* be dumb */
574 if (do_forced_ra) {
575 force_page_cache_ra(ractl, req_count);
576 return;
577 }
578
579 /* do read-ahead */
580 ondemand_readahead(ractl, false, req_count);
581 }
582 EXPORT_SYMBOL_GPL(page_cache_sync_ra);
583
page_cache_async_ra(struct readahead_control * ractl,struct page * page,unsigned long req_count)584 void page_cache_async_ra(struct readahead_control *ractl,
585 struct page *page, unsigned long req_count)
586 {
587 /* no read-ahead */
588 if (!ractl->ra->ra_pages)
589 return;
590
591 /*
592 * Same bit is used for PG_readahead and PG_reclaim.
593 */
594 if (PageWriteback(page))
595 return;
596
597 ClearPageReadahead(page);
598
599 /*
600 * Defer asynchronous read-ahead on IO congestion.
601 */
602 if (inode_read_congested(ractl->mapping->host))
603 return;
604
605 if (blk_cgroup_congested())
606 return;
607
608 /* do read-ahead */
609 ondemand_readahead(ractl, true, req_count);
610 }
611 EXPORT_SYMBOL_GPL(page_cache_async_ra);
612
ksys_readahead(int fd,loff_t offset,size_t count)613 ssize_t ksys_readahead(int fd, loff_t offset, size_t count)
614 {
615 ssize_t ret;
616 struct fd f;
617
618 ret = -EBADF;
619 f = fdget(fd);
620 if (!f.file || !(f.file->f_mode & FMODE_READ))
621 goto out;
622
623 /*
624 * The readahead() syscall is intended to run only on files
625 * that can execute readahead. If readahead is not possible
626 * on this file, then we must return -EINVAL.
627 */
628 ret = -EINVAL;
629 if (!f.file->f_mapping || !f.file->f_mapping->a_ops ||
630 !S_ISREG(file_inode(f.file)->i_mode))
631 goto out;
632
633 ret = vfs_fadvise(f.file, offset, count, POSIX_FADV_WILLNEED);
634 out:
635 fdput(f);
636 return ret;
637 }
638
SYSCALL_DEFINE3(readahead,int,fd,loff_t,offset,size_t,count)639 SYSCALL_DEFINE3(readahead, int, fd, loff_t, offset, size_t, count)
640 {
641 return ksys_readahead(fd, offset, count);
642 }
643
644 /**
645 * readahead_expand - Expand a readahead request
646 * @ractl: The request to be expanded
647 * @new_start: The revised start
648 * @new_len: The revised size of the request
649 *
650 * Attempt to expand a readahead request outwards from the current size to the
651 * specified size by inserting locked pages before and after the current window
652 * to increase the size to the new window. This may involve the insertion of
653 * THPs, in which case the window may get expanded even beyond what was
654 * requested.
655 *
656 * The algorithm will stop if it encounters a conflicting page already in the
657 * pagecache and leave a smaller expansion than requested.
658 *
659 * The caller must check for this by examining the revised @ractl object for a
660 * different expansion than was requested.
661 */
readahead_expand(struct readahead_control * ractl,loff_t new_start,size_t new_len)662 void readahead_expand(struct readahead_control *ractl,
663 loff_t new_start, size_t new_len)
664 {
665 struct address_space *mapping = ractl->mapping;
666 struct file_ra_state *ra = ractl->ra;
667 pgoff_t new_index, new_nr_pages;
668 gfp_t gfp_mask = readahead_gfp_mask(mapping);
669
670 new_index = new_start / PAGE_SIZE;
671
672 /* Expand the leading edge downwards */
673 while (ractl->_index > new_index) {
674 unsigned long index = ractl->_index - 1;
675 struct page *page = xa_load(&mapping->i_pages, index);
676
677 if (page && !xa_is_value(page))
678 return; /* Page apparently present */
679
680 page = __page_cache_alloc(gfp_mask);
681 if (!page)
682 return;
683 if (add_to_page_cache_lru(page, mapping, index, gfp_mask) < 0) {
684 put_page(page);
685 return;
686 }
687
688 ractl->_nr_pages++;
689 ractl->_index = page->index;
690 }
691
692 new_len += new_start - readahead_pos(ractl);
693 new_nr_pages = DIV_ROUND_UP(new_len, PAGE_SIZE);
694
695 /* Expand the trailing edge upwards */
696 while (ractl->_nr_pages < new_nr_pages) {
697 unsigned long index = ractl->_index + ractl->_nr_pages;
698 struct page *page = xa_load(&mapping->i_pages, index);
699
700 if (page && !xa_is_value(page))
701 return; /* Page apparently present */
702
703 page = __page_cache_alloc(gfp_mask);
704 if (!page)
705 return;
706 if (add_to_page_cache_lru(page, mapping, index, gfp_mask) < 0) {
707 put_page(page);
708 return;
709 }
710 ractl->_nr_pages++;
711 if (ra) {
712 ra->size++;
713 ra->async_size++;
714 }
715 }
716 }
717 EXPORT_SYMBOL(readahead_expand);
718
