Loading...
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * fs/mpage.c
4 *
5 * Copyright (C) 2002, Linus Torvalds.
6 *
7 * Contains functions related to preparing and submitting BIOs which contain
8 * multiple pagecache pages.
9 *
10 * 15May2002 Andrew Morton
11 * Initial version
12 * 27Jun2002 axboe@suse.de
13 * use bio_add_page() to build bio's just the right size
14 */
15
16#include <linux/kernel.h>
17#include <linux/export.h>
18#include <linux/mm.h>
19#include <linux/kdev_t.h>
20#include <linux/gfp.h>
21#include <linux/bio.h>
22#include <linux/fs.h>
23#include <linux/buffer_head.h>
24#include <linux/blkdev.h>
25#include <linux/highmem.h>
26#include <linux/prefetch.h>
27#include <linux/mpage.h>
28#include <linux/mm_inline.h>
29#include <linux/writeback.h>
30#include <linux/backing-dev.h>
31#include <linux/pagevec.h>
32#include <linux/cleancache.h>
33#include "internal.h"
34
35/*
36 * I/O completion handler for multipage BIOs.
37 *
38 * The mpage code never puts partial pages into a BIO (except for end-of-file).
39 * If a page does not map to a contiguous run of blocks then it simply falls
40 * back to block_read_full_page().
41 *
42 * Why is this? If a page's completion depends on a number of different BIOs
43 * which can complete in any order (or at the same time) then determining the
44 * status of that page is hard. See end_buffer_async_read() for the details.
45 * There is no point in duplicating all that complexity.
46 */
47static void mpage_end_io(struct bio *bio)
48{
49 struct bio_vec *bv;
50 int i;
51
52 bio_for_each_segment_all(bv, bio, i) {
53 struct page *page = bv->bv_page;
54 page_endio(page, op_is_write(bio_op(bio)),
55 blk_status_to_errno(bio->bi_status));
56 }
57
58 bio_put(bio);
59}
60
61static struct bio *mpage_bio_submit(int op, int op_flags, struct bio *bio)
62{
63 bio->bi_end_io = mpage_end_io;
64 bio_set_op_attrs(bio, op, op_flags);
65 guard_bio_eod(op, bio);
66 submit_bio(bio);
67 return NULL;
68}
69
70static struct bio *
71mpage_alloc(struct block_device *bdev,
72 sector_t first_sector, int nr_vecs,
73 gfp_t gfp_flags)
74{
75 struct bio *bio;
76
77 /* Restrict the given (page cache) mask for slab allocations */
78 gfp_flags &= GFP_KERNEL;
79 bio = bio_alloc(gfp_flags, nr_vecs);
80
81 if (bio == NULL && (current->flags & PF_MEMALLOC)) {
82 while (!bio && (nr_vecs /= 2))
83 bio = bio_alloc(gfp_flags, nr_vecs);
84 }
85
86 if (bio) {
87 bio_set_dev(bio, bdev);
88 bio->bi_iter.bi_sector = first_sector;
89 }
90 return bio;
91}
92
93/*
94 * support function for mpage_readpages. The fs supplied get_block might
95 * return an up to date buffer. This is used to map that buffer into
96 * the page, which allows readpage to avoid triggering a duplicate call
97 * to get_block.
98 *
99 * The idea is to avoid adding buffers to pages that don't already have
100 * them. So when the buffer is up to date and the page size == block size,
101 * this marks the page up to date instead of adding new buffers.
102 */
103static void
104map_buffer_to_page(struct page *page, struct buffer_head *bh, int page_block)
105{
106 struct inode *inode = page->mapping->host;
107 struct buffer_head *page_bh, *head;
108 int block = 0;
109
110 if (!page_has_buffers(page)) {
111 /*
112 * don't make any buffers if there is only one buffer on
113 * the page and the page just needs to be set up to date
114 */
115 if (inode->i_blkbits == PAGE_SHIFT &&
116 buffer_uptodate(bh)) {
117 SetPageUptodate(page);
118 return;
119 }
120 create_empty_buffers(page, i_blocksize(inode), 0);
121 }
122 head = page_buffers(page);
123 page_bh = head;
124 do {
125 if (block == page_block) {
126 page_bh->b_state = bh->b_state;
127 page_bh->b_bdev = bh->b_bdev;
128 page_bh->b_blocknr = bh->b_blocknr;
129 break;
130 }
131 page_bh = page_bh->b_this_page;
132 block++;
133 } while (page_bh != head);
134}
135
136/*
137 * This is the worker routine which does all the work of mapping the disk
138 * blocks and constructs largest possible bios, submits them for IO if the
139 * blocks are not contiguous on the disk.
140 *
141 * We pass a buffer_head back and forth and use its buffer_mapped() flag to
142 * represent the validity of its disk mapping and to decide when to do the next
143 * get_block() call.
144 */
145static struct bio *
146do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
147 sector_t *last_block_in_bio, struct buffer_head *map_bh,
148 unsigned long *first_logical_block, get_block_t get_block,
149 gfp_t gfp)
150{
151 struct inode *inode = page->mapping->host;
152 const unsigned blkbits = inode->i_blkbits;
153 const unsigned blocks_per_page = PAGE_SIZE >> blkbits;
154 const unsigned blocksize = 1 << blkbits;
155 sector_t block_in_file;
156 sector_t last_block;
157 sector_t last_block_in_file;
158 sector_t blocks[MAX_BUF_PER_PAGE];
159 unsigned page_block;
160 unsigned first_hole = blocks_per_page;
161 struct block_device *bdev = NULL;
162 int length;
163 int fully_mapped = 1;
164 unsigned nblocks;
165 unsigned relative_block;
166
167 if (page_has_buffers(page))
168 goto confused;
169
170 block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
171 last_block = block_in_file + nr_pages * blocks_per_page;
172 last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits;
173 if (last_block > last_block_in_file)
174 last_block = last_block_in_file;
175 page_block = 0;
176
177 /*
178 * Map blocks using the result from the previous get_blocks call first.
179 */
180 nblocks = map_bh->b_size >> blkbits;
181 if (buffer_mapped(map_bh) && block_in_file > *first_logical_block &&
182 block_in_file < (*first_logical_block + nblocks)) {
183 unsigned map_offset = block_in_file - *first_logical_block;
184 unsigned last = nblocks - map_offset;
185
186 for (relative_block = 0; ; relative_block++) {
187 if (relative_block == last) {
188 clear_buffer_mapped(map_bh);
189 break;
190 }
191 if (page_block == blocks_per_page)
192 break;
193 blocks[page_block] = map_bh->b_blocknr + map_offset +
194 relative_block;
195 page_block++;
196 block_in_file++;
197 }
198 bdev = map_bh->b_bdev;
199 }
200
201 /*
202 * Then do more get_blocks calls until we are done with this page.
203 */
204 map_bh->b_page = page;
205 while (page_block < blocks_per_page) {
206 map_bh->b_state = 0;
207 map_bh->b_size = 0;
208
209 if (block_in_file < last_block) {
210 map_bh->b_size = (last_block-block_in_file) << blkbits;
211 if (get_block(inode, block_in_file, map_bh, 0))
212 goto confused;
213 *first_logical_block = block_in_file;
214 }
215
216 if (!buffer_mapped(map_bh)) {
217 fully_mapped = 0;
218 if (first_hole == blocks_per_page)
219 first_hole = page_block;
220 page_block++;
221 block_in_file++;
222 continue;
223 }
224
225 /* some filesystems will copy data into the page during
226 * the get_block call, in which case we don't want to
227 * read it again. map_buffer_to_page copies the data
228 * we just collected from get_block into the page's buffers
229 * so readpage doesn't have to repeat the get_block call
230 */
231 if (buffer_uptodate(map_bh)) {
232 map_buffer_to_page(page, map_bh, page_block);
233 goto confused;
234 }
235
236 if (first_hole != blocks_per_page)
237 goto confused; /* hole -> non-hole */
238
239 /* Contiguous blocks? */
240 if (page_block && blocks[page_block-1] != map_bh->b_blocknr-1)
241 goto confused;
242 nblocks = map_bh->b_size >> blkbits;
243 for (relative_block = 0; ; relative_block++) {
244 if (relative_block == nblocks) {
245 clear_buffer_mapped(map_bh);
246 break;
247 } else if (page_block == blocks_per_page)
248 break;
249 blocks[page_block] = map_bh->b_blocknr+relative_block;
250 page_block++;
251 block_in_file++;
252 }
253 bdev = map_bh->b_bdev;
254 }
255
256 if (first_hole != blocks_per_page) {
257 zero_user_segment(page, first_hole << blkbits, PAGE_SIZE);
258 if (first_hole == 0) {
259 SetPageUptodate(page);
260 unlock_page(page);
261 goto out;
262 }
263 } else if (fully_mapped) {
264 SetPageMappedToDisk(page);
265 }
266
267 if (fully_mapped && blocks_per_page == 1 && !PageUptodate(page) &&
268 cleancache_get_page(page) == 0) {
269 SetPageUptodate(page);
270 goto confused;
271 }
272
273 /*
274 * This page will go to BIO. Do we need to send this BIO off first?
275 */
276 if (bio && (*last_block_in_bio != blocks[0] - 1))
277 bio = mpage_bio_submit(REQ_OP_READ, 0, bio);
278
279alloc_new:
280 if (bio == NULL) {
281 if (first_hole == blocks_per_page) {
282 if (!bdev_read_page(bdev, blocks[0] << (blkbits - 9),
283 page))
284 goto out;
285 }
286 bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
287 min_t(int, nr_pages, BIO_MAX_PAGES), gfp);
288 if (bio == NULL)
289 goto confused;
290 }
291
292 length = first_hole << blkbits;
293 if (bio_add_page(bio, page, length, 0) < length) {
294 bio = mpage_bio_submit(REQ_OP_READ, 0, bio);
295 goto alloc_new;
296 }
297
298 relative_block = block_in_file - *first_logical_block;
299 nblocks = map_bh->b_size >> blkbits;
300 if ((buffer_boundary(map_bh) && relative_block == nblocks) ||
301 (first_hole != blocks_per_page))
302 bio = mpage_bio_submit(REQ_OP_READ, 0, bio);
303 else
304 *last_block_in_bio = blocks[blocks_per_page - 1];
305out:
306 return bio;
307
308confused:
309 if (bio)
310 bio = mpage_bio_submit(REQ_OP_READ, 0, bio);
311 if (!PageUptodate(page))
312 block_read_full_page(page, get_block);
313 else
314 unlock_page(page);
315 goto out;
316}
317
318/**
319 * mpage_readpages - populate an address space with some pages & start reads against them
320 * @mapping: the address_space
321 * @pages: The address of a list_head which contains the target pages. These
322 * pages have their ->index populated and are otherwise uninitialised.
323 * The page at @pages->prev has the lowest file offset, and reads should be
324 * issued in @pages->prev to @pages->next order.
325 * @nr_pages: The number of pages at *@pages
326 * @get_block: The filesystem's block mapper function.
327 *
328 * This function walks the pages and the blocks within each page, building and
329 * emitting large BIOs.
330 *
331 * If anything unusual happens, such as:
332 *
333 * - encountering a page which has buffers
334 * - encountering a page which has a non-hole after a hole
335 * - encountering a page with non-contiguous blocks
336 *
337 * then this code just gives up and calls the buffer_head-based read function.
338 * It does handle a page which has holes at the end - that is a common case:
339 * the end-of-file on blocksize < PAGE_SIZE setups.
340 *
341 * BH_Boundary explanation:
342 *
343 * There is a problem. The mpage read code assembles several pages, gets all
344 * their disk mappings, and then submits them all. That's fine, but obtaining
345 * the disk mappings may require I/O. Reads of indirect blocks, for example.
346 *
347 * So an mpage read of the first 16 blocks of an ext2 file will cause I/O to be
348 * submitted in the following order:
349 *
350 * 12 0 1 2 3 4 5 6 7 8 9 10 11 13 14 15 16
351 *
352 * because the indirect block has to be read to get the mappings of blocks
353 * 13,14,15,16. Obviously, this impacts performance.
354 *
355 * So what we do it to allow the filesystem's get_block() function to set
356 * BH_Boundary when it maps block 11. BH_Boundary says: mapping of the block
357 * after this one will require I/O against a block which is probably close to
358 * this one. So you should push what I/O you have currently accumulated.
359 *
360 * This all causes the disk requests to be issued in the correct order.
361 */
362int
363mpage_readpages(struct address_space *mapping, struct list_head *pages,
364 unsigned nr_pages, get_block_t get_block)
365{
366 struct bio *bio = NULL;
367 unsigned page_idx;
368 sector_t last_block_in_bio = 0;
369 struct buffer_head map_bh;
370 unsigned long first_logical_block = 0;
371 gfp_t gfp = readahead_gfp_mask(mapping);
372
373 map_bh.b_state = 0;
374 map_bh.b_size = 0;
375 for (page_idx = 0; page_idx < nr_pages; page_idx++) {
376 struct page *page = lru_to_page(pages);
377
378 prefetchw(&page->flags);
379 list_del(&page->lru);
380 if (!add_to_page_cache_lru(page, mapping,
381 page->index,
382 gfp)) {
383 bio = do_mpage_readpage(bio, page,
384 nr_pages - page_idx,
385 &last_block_in_bio, &map_bh,
386 &first_logical_block,
387 get_block, gfp);
388 }
389 put_page(page);
390 }
391 BUG_ON(!list_empty(pages));
392 if (bio)
393 mpage_bio_submit(REQ_OP_READ, 0, bio);
394 return 0;
395}
396EXPORT_SYMBOL(mpage_readpages);
397
398/*
399 * This isn't called much at all
400 */
401int mpage_readpage(struct page *page, get_block_t get_block)
402{
403 struct bio *bio = NULL;
404 sector_t last_block_in_bio = 0;
405 struct buffer_head map_bh;
406 unsigned long first_logical_block = 0;
407 gfp_t gfp = mapping_gfp_constraint(page->mapping, GFP_KERNEL);
408
409 map_bh.b_state = 0;
410 map_bh.b_size = 0;
411 bio = do_mpage_readpage(bio, page, 1, &last_block_in_bio,
412 &map_bh, &first_logical_block, get_block, gfp);
413 if (bio)
414 mpage_bio_submit(REQ_OP_READ, 0, bio);
415 return 0;
416}
417EXPORT_SYMBOL(mpage_readpage);
418
419/*
420 * Writing is not so simple.
421 *
422 * If the page has buffers then they will be used for obtaining the disk
423 * mapping. We only support pages which are fully mapped-and-dirty, with a
424 * special case for pages which are unmapped at the end: end-of-file.
425 *
426 * If the page has no buffers (preferred) then the page is mapped here.
427 *
428 * If all blocks are found to be contiguous then the page can go into the
429 * BIO. Otherwise fall back to the mapping's writepage().
430 *
431 * FIXME: This code wants an estimate of how many pages are still to be
432 * written, so it can intelligently allocate a suitably-sized BIO. For now,
433 * just allocate full-size (16-page) BIOs.
434 */
435
436struct mpage_data {
437 struct bio *bio;
438 sector_t last_block_in_bio;
439 get_block_t *get_block;
440 unsigned use_writepage;
441};
442
443/*
444 * We have our BIO, so we can now mark the buffers clean. Make
445 * sure to only clean buffers which we know we'll be writing.
446 */
447static void clean_buffers(struct page *page, unsigned first_unmapped)
448{
449 unsigned buffer_counter = 0;
450 struct buffer_head *bh, *head;
451 if (!page_has_buffers(page))
452 return;
453 head = page_buffers(page);
454 bh = head;
455
456 do {
457 if (buffer_counter++ == first_unmapped)
458 break;
459 clear_buffer_dirty(bh);
460 bh = bh->b_this_page;
461 } while (bh != head);
462
463 /*
464 * we cannot drop the bh if the page is not uptodate or a concurrent
465 * readpage would fail to serialize with the bh and it would read from
466 * disk before we reach the platter.
467 */
468 if (buffer_heads_over_limit && PageUptodate(page))
469 try_to_free_buffers(page);
470}
471
472/*
473 * For situations where we want to clean all buffers attached to a page.
474 * We don't need to calculate how many buffers are attached to the page,
475 * we just need to specify a number larger than the maximum number of buffers.
476 */
477void clean_page_buffers(struct page *page)
478{
479 clean_buffers(page, ~0U);
480}
481
482static int __mpage_writepage(struct page *page, struct writeback_control *wbc,
483 void *data)
484{
485 struct mpage_data *mpd = data;
486 struct bio *bio = mpd->bio;
487 struct address_space *mapping = page->mapping;
488 struct inode *inode = page->mapping->host;
489 const unsigned blkbits = inode->i_blkbits;
490 unsigned long end_index;
491 const unsigned blocks_per_page = PAGE_SIZE >> blkbits;
492 sector_t last_block;
493 sector_t block_in_file;
494 sector_t blocks[MAX_BUF_PER_PAGE];
495 unsigned page_block;
496 unsigned first_unmapped = blocks_per_page;
497 struct block_device *bdev = NULL;
498 int boundary = 0;
499 sector_t boundary_block = 0;
500 struct block_device *boundary_bdev = NULL;
501 int length;
502 struct buffer_head map_bh;
503 loff_t i_size = i_size_read(inode);
504 int ret = 0;
505 int op_flags = wbc_to_write_flags(wbc);
506
507 if (page_has_buffers(page)) {
508 struct buffer_head *head = page_buffers(page);
509 struct buffer_head *bh = head;
510
511 /* If they're all mapped and dirty, do it */
512 page_block = 0;
513 do {
514 BUG_ON(buffer_locked(bh));
515 if (!buffer_mapped(bh)) {
516 /*
517 * unmapped dirty buffers are created by
518 * __set_page_dirty_buffers -> mmapped data
519 */
520 if (buffer_dirty(bh))
521 goto confused;
522 if (first_unmapped == blocks_per_page)
523 first_unmapped = page_block;
524 continue;
525 }
526
527 if (first_unmapped != blocks_per_page)
528 goto confused; /* hole -> non-hole */
529
530 if (!buffer_dirty(bh) || !buffer_uptodate(bh))
531 goto confused;
532 if (page_block) {
533 if (bh->b_blocknr != blocks[page_block-1] + 1)
534 goto confused;
535 }
536 blocks[page_block++] = bh->b_blocknr;
537 boundary = buffer_boundary(bh);
538 if (boundary) {
539 boundary_block = bh->b_blocknr;
540 boundary_bdev = bh->b_bdev;
541 }
542 bdev = bh->b_bdev;
543 } while ((bh = bh->b_this_page) != head);
544
545 if (first_unmapped)
546 goto page_is_mapped;
547
548 /*
549 * Page has buffers, but they are all unmapped. The page was
550 * created by pagein or read over a hole which was handled by
551 * block_read_full_page(). If this address_space is also
552 * using mpage_readpages then this can rarely happen.
553 */
554 goto confused;
555 }
556
557 /*
558 * The page has no buffers: map it to disk
559 */
560 BUG_ON(!PageUptodate(page));
561 block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
562 last_block = (i_size - 1) >> blkbits;
563 map_bh.b_page = page;
564 for (page_block = 0; page_block < blocks_per_page; ) {
565
566 map_bh.b_state = 0;
567 map_bh.b_size = 1 << blkbits;
568 if (mpd->get_block(inode, block_in_file, &map_bh, 1))
569 goto confused;
570 if (buffer_new(&map_bh))
571 clean_bdev_bh_alias(&map_bh);
572 if (buffer_boundary(&map_bh)) {
573 boundary_block = map_bh.b_blocknr;
574 boundary_bdev = map_bh.b_bdev;
575 }
576 if (page_block) {
577 if (map_bh.b_blocknr != blocks[page_block-1] + 1)
578 goto confused;
579 }
580 blocks[page_block++] = map_bh.b_blocknr;
581 boundary = buffer_boundary(&map_bh);
582 bdev = map_bh.b_bdev;
583 if (block_in_file == last_block)
584 break;
585 block_in_file++;
586 }
587 BUG_ON(page_block == 0);
588
589 first_unmapped = page_block;
590
591page_is_mapped:
592 end_index = i_size >> PAGE_SHIFT;
593 if (page->index >= end_index) {
594 /*
595 * The page straddles i_size. It must be zeroed out on each
596 * and every writepage invocation because it may be mmapped.
597 * "A file is mapped in multiples of the page size. For a file
598 * that is not a multiple of the page size, the remaining memory
599 * is zeroed when mapped, and writes to that region are not
600 * written out to the file."
601 */
602 unsigned offset = i_size & (PAGE_SIZE - 1);
603
604 if (page->index > end_index || !offset)
605 goto confused;
606 zero_user_segment(page, offset, PAGE_SIZE);
607 }
608
609 /*
610 * This page will go to BIO. Do we need to send this BIO off first?
611 */
612 if (bio && mpd->last_block_in_bio != blocks[0] - 1)
613 bio = mpage_bio_submit(REQ_OP_WRITE, op_flags, bio);
614
615alloc_new:
616 if (bio == NULL) {
617 if (first_unmapped == blocks_per_page) {
618 if (!bdev_write_page(bdev, blocks[0] << (blkbits - 9),
619 page, wbc))
620 goto out;
621 }
622 bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
623 BIO_MAX_PAGES, GFP_NOFS|__GFP_HIGH);
624 if (bio == NULL)
625 goto confused;
626
627 wbc_init_bio(wbc, bio);
628 bio->bi_write_hint = inode->i_write_hint;
629 }
630
631 /*
632 * Must try to add the page before marking the buffer clean or
633 * the confused fail path above (OOM) will be very confused when
634 * it finds all bh marked clean (i.e. it will not write anything)
635 */
636 wbc_account_io(wbc, page, PAGE_SIZE);
637 length = first_unmapped << blkbits;
638 if (bio_add_page(bio, page, length, 0) < length) {
639 bio = mpage_bio_submit(REQ_OP_WRITE, op_flags, bio);
640 goto alloc_new;
641 }
642
643 clean_buffers(page, first_unmapped);
644
645 BUG_ON(PageWriteback(page));
646 set_page_writeback(page);
647 unlock_page(page);
648 if (boundary || (first_unmapped != blocks_per_page)) {
649 bio = mpage_bio_submit(REQ_OP_WRITE, op_flags, bio);
650 if (boundary_block) {
651 write_boundary_block(boundary_bdev,
652 boundary_block, 1 << blkbits);
653 }
654 } else {
655 mpd->last_block_in_bio = blocks[blocks_per_page - 1];
656 }
657 goto out;
658
659confused:
660 if (bio)
661 bio = mpage_bio_submit(REQ_OP_WRITE, op_flags, bio);
662
663 if (mpd->use_writepage) {
664 ret = mapping->a_ops->writepage(page, wbc);
665 } else {
666 ret = -EAGAIN;
667 goto out;
668 }
669 /*
670 * The caller has a ref on the inode, so *mapping is stable
671 */
672 mapping_set_error(mapping, ret);
673out:
674 mpd->bio = bio;
675 return ret;
676}
677
678/**
679 * mpage_writepages - walk the list of dirty pages of the given address space & writepage() all of them
680 * @mapping: address space structure to write
681 * @wbc: subtract the number of written pages from *@wbc->nr_to_write
682 * @get_block: the filesystem's block mapper function.
683 * If this is NULL then use a_ops->writepage. Otherwise, go
684 * direct-to-BIO.
685 *
686 * This is a library function, which implements the writepages()
687 * address_space_operation.
688 *
689 * If a page is already under I/O, generic_writepages() skips it, even
690 * if it's dirty. This is desirable behaviour for memory-cleaning writeback,
691 * but it is INCORRECT for data-integrity system calls such as fsync(). fsync()
692 * and msync() need to guarantee that all the data which was dirty at the time
693 * the call was made get new I/O started against them. If wbc->sync_mode is
694 * WB_SYNC_ALL then we were called for data integrity and we must wait for
695 * existing IO to complete.
696 */
697int
698mpage_writepages(struct address_space *mapping,
699 struct writeback_control *wbc, get_block_t get_block)
700{
701 struct blk_plug plug;
702 int ret;
703
704 blk_start_plug(&plug);
705
706 if (!get_block)
707 ret = generic_writepages(mapping, wbc);
708 else {
709 struct mpage_data mpd = {
710 .bio = NULL,
711 .last_block_in_bio = 0,
712 .get_block = get_block,
713 .use_writepage = 1,
714 };
715
716 ret = write_cache_pages(mapping, wbc, __mpage_writepage, &mpd);
717 if (mpd.bio) {
718 int op_flags = (wbc->sync_mode == WB_SYNC_ALL ?
719 REQ_SYNC : 0);
720 mpage_bio_submit(REQ_OP_WRITE, op_flags, mpd.bio);
721 }
722 }
723 blk_finish_plug(&plug);
724 return ret;
725}
726EXPORT_SYMBOL(mpage_writepages);
727
728int mpage_writepage(struct page *page, get_block_t get_block,
729 struct writeback_control *wbc)
730{
731 struct mpage_data mpd = {
732 .bio = NULL,
733 .last_block_in_bio = 0,
734 .get_block = get_block,
735 .use_writepage = 0,
736 };
737 int ret = __mpage_writepage(page, wbc, &mpd);
738 if (mpd.bio) {
739 int op_flags = (wbc->sync_mode == WB_SYNC_ALL ?
740 REQ_SYNC : 0);
741 mpage_bio_submit(REQ_OP_WRITE, op_flags, mpd.bio);
742 }
743 return ret;
744}
745EXPORT_SYMBOL(mpage_writepage);
1/*
2 * fs/mpage.c
3 *
4 * Copyright (C) 2002, Linus Torvalds.
5 *
6 * Contains functions related to preparing and submitting BIOs which contain
7 * multiple pagecache pages.
8 *
9 * 15May2002 Andrew Morton
10 * Initial version
11 * 27Jun2002 axboe@suse.de
12 * use bio_add_page() to build bio's just the right size
13 */
14
15#include <linux/kernel.h>
16#include <linux/export.h>
17#include <linux/mm.h>
18#include <linux/kdev_t.h>
19#include <linux/gfp.h>
20#include <linux/bio.h>
21#include <linux/fs.h>
22#include <linux/buffer_head.h>
23#include <linux/blkdev.h>
24#include <linux/highmem.h>
25#include <linux/prefetch.h>
26#include <linux/mpage.h>
27#include <linux/mm_inline.h>
28#include <linux/writeback.h>
29#include <linux/backing-dev.h>
30#include <linux/pagevec.h>
31#include <linux/cleancache.h>
32#include "internal.h"
33
34/*
35 * I/O completion handler for multipage BIOs.
36 *
37 * The mpage code never puts partial pages into a BIO (except for end-of-file).
38 * If a page does not map to a contiguous run of blocks then it simply falls
39 * back to block_read_full_page().
40 *
41 * Why is this? If a page's completion depends on a number of different BIOs
42 * which can complete in any order (or at the same time) then determining the
43 * status of that page is hard. See end_buffer_async_read() for the details.
44 * There is no point in duplicating all that complexity.
45 */
46static void mpage_end_io(struct bio *bio)
47{
48 struct bio_vec *bv;
49 int i;
50
51 bio_for_each_segment_all(bv, bio, i) {
52 struct page *page = bv->bv_page;
53 page_endio(page, bio_data_dir(bio), bio->bi_error);
54 }
55
56 bio_put(bio);
57}
58
59static struct bio *mpage_bio_submit(int rw, struct bio *bio)
60{
61 bio->bi_end_io = mpage_end_io;
62 guard_bio_eod(rw, bio);
63 submit_bio(rw, bio);
64 return NULL;
65}
66
67static struct bio *
68mpage_alloc(struct block_device *bdev,
69 sector_t first_sector, int nr_vecs,
70 gfp_t gfp_flags)
71{
72 struct bio *bio;
73
74 bio = bio_alloc(gfp_flags, nr_vecs);
75
76 if (bio == NULL && (current->flags & PF_MEMALLOC)) {
77 while (!bio && (nr_vecs /= 2))
78 bio = bio_alloc(gfp_flags, nr_vecs);
79 }
80
81 if (bio) {
82 bio->bi_bdev = bdev;
83 bio->bi_iter.bi_sector = first_sector;
84 }
85 return bio;
86}
87
88/*
89 * support function for mpage_readpages. The fs supplied get_block might
90 * return an up to date buffer. This is used to map that buffer into
91 * the page, which allows readpage to avoid triggering a duplicate call
92 * to get_block.
93 *
94 * The idea is to avoid adding buffers to pages that don't already have
95 * them. So when the buffer is up to date and the page size == block size,
96 * this marks the page up to date instead of adding new buffers.
97 */
98static void
99map_buffer_to_page(struct page *page, struct buffer_head *bh, int page_block)
100{
101 struct inode *inode = page->mapping->host;
102 struct buffer_head *page_bh, *head;
103 int block = 0;
104
105 if (!page_has_buffers(page)) {
106 /*
107 * don't make any buffers if there is only one buffer on
108 * the page and the page just needs to be set up to date
109 */
110 if (inode->i_blkbits == PAGE_SHIFT &&
111 buffer_uptodate(bh)) {
112 SetPageUptodate(page);
113 return;
114 }
115 create_empty_buffers(page, 1 << inode->i_blkbits, 0);
116 }
117 head = page_buffers(page);
118 page_bh = head;
119 do {
120 if (block == page_block) {
121 page_bh->b_state = bh->b_state;
122 page_bh->b_bdev = bh->b_bdev;
123 page_bh->b_blocknr = bh->b_blocknr;
124 break;
125 }
126 page_bh = page_bh->b_this_page;
127 block++;
128 } while (page_bh != head);
129}
130
131/*
132 * This is the worker routine which does all the work of mapping the disk
133 * blocks and constructs largest possible bios, submits them for IO if the
134 * blocks are not contiguous on the disk.
135 *
136 * We pass a buffer_head back and forth and use its buffer_mapped() flag to
137 * represent the validity of its disk mapping and to decide when to do the next
138 * get_block() call.
139 */
140static struct bio *
141do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
142 sector_t *last_block_in_bio, struct buffer_head *map_bh,
143 unsigned long *first_logical_block, get_block_t get_block,
144 gfp_t gfp)
145{
146 struct inode *inode = page->mapping->host;
147 const unsigned blkbits = inode->i_blkbits;
148 const unsigned blocks_per_page = PAGE_SIZE >> blkbits;
149 const unsigned blocksize = 1 << blkbits;
150 sector_t block_in_file;
151 sector_t last_block;
152 sector_t last_block_in_file;
153 sector_t blocks[MAX_BUF_PER_PAGE];
154 unsigned page_block;
155 unsigned first_hole = blocks_per_page;
156 struct block_device *bdev = NULL;
157 int length;
158 int fully_mapped = 1;
159 unsigned nblocks;
160 unsigned relative_block;
161
162 if (page_has_buffers(page))
163 goto confused;
164
165 block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
166 last_block = block_in_file + nr_pages * blocks_per_page;
167 last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits;
168 if (last_block > last_block_in_file)
169 last_block = last_block_in_file;
170 page_block = 0;
171
172 /*
173 * Map blocks using the result from the previous get_blocks call first.
174 */
175 nblocks = map_bh->b_size >> blkbits;
176 if (buffer_mapped(map_bh) && block_in_file > *first_logical_block &&
177 block_in_file < (*first_logical_block + nblocks)) {
178 unsigned map_offset = block_in_file - *first_logical_block;
179 unsigned last = nblocks - map_offset;
180
181 for (relative_block = 0; ; relative_block++) {
182 if (relative_block == last) {
183 clear_buffer_mapped(map_bh);
184 break;
185 }
186 if (page_block == blocks_per_page)
187 break;
188 blocks[page_block] = map_bh->b_blocknr + map_offset +
189 relative_block;
190 page_block++;
191 block_in_file++;
192 }
193 bdev = map_bh->b_bdev;
194 }
195
196 /*
197 * Then do more get_blocks calls until we are done with this page.
198 */
199 map_bh->b_page = page;
200 while (page_block < blocks_per_page) {
201 map_bh->b_state = 0;
202 map_bh->b_size = 0;
203
204 if (block_in_file < last_block) {
205 map_bh->b_size = (last_block-block_in_file) << blkbits;
206 if (get_block(inode, block_in_file, map_bh, 0))
207 goto confused;
208 *first_logical_block = block_in_file;
209 }
210
211 if (!buffer_mapped(map_bh)) {
212 fully_mapped = 0;
213 if (first_hole == blocks_per_page)
214 first_hole = page_block;
215 page_block++;
216 block_in_file++;
217 continue;
218 }
219
220 /* some filesystems will copy data into the page during
221 * the get_block call, in which case we don't want to
222 * read it again. map_buffer_to_page copies the data
223 * we just collected from get_block into the page's buffers
224 * so readpage doesn't have to repeat the get_block call
225 */
226 if (buffer_uptodate(map_bh)) {
227 map_buffer_to_page(page, map_bh, page_block);
228 goto confused;
229 }
230
231 if (first_hole != blocks_per_page)
232 goto confused; /* hole -> non-hole */
233
234 /* Contiguous blocks? */
235 if (page_block && blocks[page_block-1] != map_bh->b_blocknr-1)
236 goto confused;
237 nblocks = map_bh->b_size >> blkbits;
238 for (relative_block = 0; ; relative_block++) {
239 if (relative_block == nblocks) {
240 clear_buffer_mapped(map_bh);
241 break;
242 } else if (page_block == blocks_per_page)
243 break;
244 blocks[page_block] = map_bh->b_blocknr+relative_block;
245 page_block++;
246 block_in_file++;
247 }
248 bdev = map_bh->b_bdev;
249 }
250
251 if (first_hole != blocks_per_page) {
252 zero_user_segment(page, first_hole << blkbits, PAGE_SIZE);
253 if (first_hole == 0) {
254 SetPageUptodate(page);
255 unlock_page(page);
256 goto out;
257 }
258 } else if (fully_mapped) {
259 SetPageMappedToDisk(page);
260 }
261
262 if (fully_mapped && blocks_per_page == 1 && !PageUptodate(page) &&
263 cleancache_get_page(page) == 0) {
264 SetPageUptodate(page);
265 goto confused;
266 }
267
268 /*
269 * This page will go to BIO. Do we need to send this BIO off first?
270 */
271 if (bio && (*last_block_in_bio != blocks[0] - 1))
272 bio = mpage_bio_submit(READ, bio);
273
274alloc_new:
275 if (bio == NULL) {
276 if (first_hole == blocks_per_page) {
277 if (!bdev_read_page(bdev, blocks[0] << (blkbits - 9),
278 page))
279 goto out;
280 }
281 bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
282 min_t(int, nr_pages, BIO_MAX_PAGES), gfp);
283 if (bio == NULL)
284 goto confused;
285 }
286
287 length = first_hole << blkbits;
288 if (bio_add_page(bio, page, length, 0) < length) {
289 bio = mpage_bio_submit(READ, bio);
290 goto alloc_new;
291 }
292
293 relative_block = block_in_file - *first_logical_block;
294 nblocks = map_bh->b_size >> blkbits;
295 if ((buffer_boundary(map_bh) && relative_block == nblocks) ||
296 (first_hole != blocks_per_page))
297 bio = mpage_bio_submit(READ, bio);
298 else
299 *last_block_in_bio = blocks[blocks_per_page - 1];
300out:
301 return bio;
302
303confused:
304 if (bio)
305 bio = mpage_bio_submit(READ, bio);
306 if (!PageUptodate(page))
307 block_read_full_page(page, get_block);
308 else
309 unlock_page(page);
310 goto out;
311}
312
313/**
314 * mpage_readpages - populate an address space with some pages & start reads against them
315 * @mapping: the address_space
316 * @pages: The address of a list_head which contains the target pages. These
317 * pages have their ->index populated and are otherwise uninitialised.
318 * The page at @pages->prev has the lowest file offset, and reads should be
319 * issued in @pages->prev to @pages->next order.
320 * @nr_pages: The number of pages at *@pages
321 * @get_block: The filesystem's block mapper function.
322 *
323 * This function walks the pages and the blocks within each page, building and
324 * emitting large BIOs.
325 *
326 * If anything unusual happens, such as:
327 *
328 * - encountering a page which has buffers
329 * - encountering a page which has a non-hole after a hole
330 * - encountering a page with non-contiguous blocks
331 *
332 * then this code just gives up and calls the buffer_head-based read function.
333 * It does handle a page which has holes at the end - that is a common case:
334 * the end-of-file on blocksize < PAGE_SIZE setups.
335 *
336 * BH_Boundary explanation:
337 *
338 * There is a problem. The mpage read code assembles several pages, gets all
339 * their disk mappings, and then submits them all. That's fine, but obtaining
340 * the disk mappings may require I/O. Reads of indirect blocks, for example.
341 *
342 * So an mpage read of the first 16 blocks of an ext2 file will cause I/O to be
343 * submitted in the following order:
344 * 12 0 1 2 3 4 5 6 7 8 9 10 11 13 14 15 16
345 *
346 * because the indirect block has to be read to get the mappings of blocks
347 * 13,14,15,16. Obviously, this impacts performance.
348 *
349 * So what we do it to allow the filesystem's get_block() function to set
350 * BH_Boundary when it maps block 11. BH_Boundary says: mapping of the block
351 * after this one will require I/O against a block which is probably close to
352 * this one. So you should push what I/O you have currently accumulated.
353 *
354 * This all causes the disk requests to be issued in the correct order.
355 */
356int
357mpage_readpages(struct address_space *mapping, struct list_head *pages,
358 unsigned nr_pages, get_block_t get_block)
359{
360 struct bio *bio = NULL;
361 unsigned page_idx;
362 sector_t last_block_in_bio = 0;
363 struct buffer_head map_bh;
364 unsigned long first_logical_block = 0;
365 gfp_t gfp = mapping_gfp_constraint(mapping, GFP_KERNEL);
366
367 map_bh.b_state = 0;
368 map_bh.b_size = 0;
369 for (page_idx = 0; page_idx < nr_pages; page_idx++) {
370 struct page *page = lru_to_page(pages);
371
372 prefetchw(&page->flags);
373 list_del(&page->lru);
374 if (!add_to_page_cache_lru(page, mapping,
375 page->index,
376 gfp)) {
377 bio = do_mpage_readpage(bio, page,
378 nr_pages - page_idx,
379 &last_block_in_bio, &map_bh,
380 &first_logical_block,
381 get_block, gfp);
382 }
383 put_page(page);
384 }
385 BUG_ON(!list_empty(pages));
386 if (bio)
387 mpage_bio_submit(READ, bio);
388 return 0;
389}
390EXPORT_SYMBOL(mpage_readpages);
391
392/*
393 * This isn't called much at all
394 */
395int mpage_readpage(struct page *page, get_block_t get_block)
396{
397 struct bio *bio = NULL;
398 sector_t last_block_in_bio = 0;
399 struct buffer_head map_bh;
400 unsigned long first_logical_block = 0;
401 gfp_t gfp = mapping_gfp_constraint(page->mapping, GFP_KERNEL);
402
403 map_bh.b_state = 0;
404 map_bh.b_size = 0;
405 bio = do_mpage_readpage(bio, page, 1, &last_block_in_bio,
406 &map_bh, &first_logical_block, get_block, gfp);
407 if (bio)
408 mpage_bio_submit(READ, bio);
409 return 0;
410}
411EXPORT_SYMBOL(mpage_readpage);
412
413/*
414 * Writing is not so simple.
415 *
416 * If the page has buffers then they will be used for obtaining the disk
417 * mapping. We only support pages which are fully mapped-and-dirty, with a
418 * special case for pages which are unmapped at the end: end-of-file.
419 *
420 * If the page has no buffers (preferred) then the page is mapped here.
421 *
422 * If all blocks are found to be contiguous then the page can go into the
423 * BIO. Otherwise fall back to the mapping's writepage().
424 *
425 * FIXME: This code wants an estimate of how many pages are still to be
426 * written, so it can intelligently allocate a suitably-sized BIO. For now,
427 * just allocate full-size (16-page) BIOs.
428 */
429
430struct mpage_data {
431 struct bio *bio;
432 sector_t last_block_in_bio;
433 get_block_t *get_block;
434 unsigned use_writepage;
435};
436
437/*
438 * We have our BIO, so we can now mark the buffers clean. Make
439 * sure to only clean buffers which we know we'll be writing.
440 */
441static void clean_buffers(struct page *page, unsigned first_unmapped)
442{
443 unsigned buffer_counter = 0;
444 struct buffer_head *bh, *head;
445 if (!page_has_buffers(page))
446 return;
447 head = page_buffers(page);
448 bh = head;
449
450 do {
451 if (buffer_counter++ == first_unmapped)
452 break;
453 clear_buffer_dirty(bh);
454 bh = bh->b_this_page;
455 } while (bh != head);
456
457 /*
458 * we cannot drop the bh if the page is not uptodate or a concurrent
459 * readpage would fail to serialize with the bh and it would read from
460 * disk before we reach the platter.
461 */
462 if (buffer_heads_over_limit && PageUptodate(page))
463 try_to_free_buffers(page);
464}
465
466static int __mpage_writepage(struct page *page, struct writeback_control *wbc,
467 void *data)
468{
469 struct mpage_data *mpd = data;
470 struct bio *bio = mpd->bio;
471 struct address_space *mapping = page->mapping;
472 struct inode *inode = page->mapping->host;
473 const unsigned blkbits = inode->i_blkbits;
474 unsigned long end_index;
475 const unsigned blocks_per_page = PAGE_SIZE >> blkbits;
476 sector_t last_block;
477 sector_t block_in_file;
478 sector_t blocks[MAX_BUF_PER_PAGE];
479 unsigned page_block;
480 unsigned first_unmapped = blocks_per_page;
481 struct block_device *bdev = NULL;
482 int boundary = 0;
483 sector_t boundary_block = 0;
484 struct block_device *boundary_bdev = NULL;
485 int length;
486 struct buffer_head map_bh;
487 loff_t i_size = i_size_read(inode);
488 int ret = 0;
489 int wr = (wbc->sync_mode == WB_SYNC_ALL ? WRITE_SYNC : WRITE);
490
491 if (page_has_buffers(page)) {
492 struct buffer_head *head = page_buffers(page);
493 struct buffer_head *bh = head;
494
495 /* If they're all mapped and dirty, do it */
496 page_block = 0;
497 do {
498 BUG_ON(buffer_locked(bh));
499 if (!buffer_mapped(bh)) {
500 /*
501 * unmapped dirty buffers are created by
502 * __set_page_dirty_buffers -> mmapped data
503 */
504 if (buffer_dirty(bh))
505 goto confused;
506 if (first_unmapped == blocks_per_page)
507 first_unmapped = page_block;
508 continue;
509 }
510
511 if (first_unmapped != blocks_per_page)
512 goto confused; /* hole -> non-hole */
513
514 if (!buffer_dirty(bh) || !buffer_uptodate(bh))
515 goto confused;
516 if (page_block) {
517 if (bh->b_blocknr != blocks[page_block-1] + 1)
518 goto confused;
519 }
520 blocks[page_block++] = bh->b_blocknr;
521 boundary = buffer_boundary(bh);
522 if (boundary) {
523 boundary_block = bh->b_blocknr;
524 boundary_bdev = bh->b_bdev;
525 }
526 bdev = bh->b_bdev;
527 } while ((bh = bh->b_this_page) != head);
528
529 if (first_unmapped)
530 goto page_is_mapped;
531
532 /*
533 * Page has buffers, but they are all unmapped. The page was
534 * created by pagein or read over a hole which was handled by
535 * block_read_full_page(). If this address_space is also
536 * using mpage_readpages then this can rarely happen.
537 */
538 goto confused;
539 }
540
541 /*
542 * The page has no buffers: map it to disk
543 */
544 BUG_ON(!PageUptodate(page));
545 block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
546 last_block = (i_size - 1) >> blkbits;
547 map_bh.b_page = page;
548 for (page_block = 0; page_block < blocks_per_page; ) {
549
550 map_bh.b_state = 0;
551 map_bh.b_size = 1 << blkbits;
552 if (mpd->get_block(inode, block_in_file, &map_bh, 1))
553 goto confused;
554 if (buffer_new(&map_bh))
555 unmap_underlying_metadata(map_bh.b_bdev,
556 map_bh.b_blocknr);
557 if (buffer_boundary(&map_bh)) {
558 boundary_block = map_bh.b_blocknr;
559 boundary_bdev = map_bh.b_bdev;
560 }
561 if (page_block) {
562 if (map_bh.b_blocknr != blocks[page_block-1] + 1)
563 goto confused;
564 }
565 blocks[page_block++] = map_bh.b_blocknr;
566 boundary = buffer_boundary(&map_bh);
567 bdev = map_bh.b_bdev;
568 if (block_in_file == last_block)
569 break;
570 block_in_file++;
571 }
572 BUG_ON(page_block == 0);
573
574 first_unmapped = page_block;
575
576page_is_mapped:
577 end_index = i_size >> PAGE_SHIFT;
578 if (page->index >= end_index) {
579 /*
580 * The page straddles i_size. It must be zeroed out on each
581 * and every writepage invocation because it may be mmapped.
582 * "A file is mapped in multiples of the page size. For a file
583 * that is not a multiple of the page size, the remaining memory
584 * is zeroed when mapped, and writes to that region are not
585 * written out to the file."
586 */
587 unsigned offset = i_size & (PAGE_SIZE - 1);
588
589 if (page->index > end_index || !offset)
590 goto confused;
591 zero_user_segment(page, offset, PAGE_SIZE);
592 }
593
594 /*
595 * This page will go to BIO. Do we need to send this BIO off first?
596 */
597 if (bio && mpd->last_block_in_bio != blocks[0] - 1)
598 bio = mpage_bio_submit(wr, bio);
599
600alloc_new:
601 if (bio == NULL) {
602 if (first_unmapped == blocks_per_page) {
603 if (!bdev_write_page(bdev, blocks[0] << (blkbits - 9),
604 page, wbc)) {
605 clean_buffers(page, first_unmapped);
606 goto out;
607 }
608 }
609 bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
610 BIO_MAX_PAGES, GFP_NOFS|__GFP_HIGH);
611 if (bio == NULL)
612 goto confused;
613
614 wbc_init_bio(wbc, bio);
615 }
616
617 /*
618 * Must try to add the page before marking the buffer clean or
619 * the confused fail path above (OOM) will be very confused when
620 * it finds all bh marked clean (i.e. it will not write anything)
621 */
622 wbc_account_io(wbc, page, PAGE_SIZE);
623 length = first_unmapped << blkbits;
624 if (bio_add_page(bio, page, length, 0) < length) {
625 bio = mpage_bio_submit(wr, bio);
626 goto alloc_new;
627 }
628
629 clean_buffers(page, first_unmapped);
630
631 BUG_ON(PageWriteback(page));
632 set_page_writeback(page);
633 unlock_page(page);
634 if (boundary || (first_unmapped != blocks_per_page)) {
635 bio = mpage_bio_submit(wr, bio);
636 if (boundary_block) {
637 write_boundary_block(boundary_bdev,
638 boundary_block, 1 << blkbits);
639 }
640 } else {
641 mpd->last_block_in_bio = blocks[blocks_per_page - 1];
642 }
643 goto out;
644
645confused:
646 if (bio)
647 bio = mpage_bio_submit(wr, bio);
648
649 if (mpd->use_writepage) {
650 ret = mapping->a_ops->writepage(page, wbc);
651 } else {
652 ret = -EAGAIN;
653 goto out;
654 }
655 /*
656 * The caller has a ref on the inode, so *mapping is stable
657 */
658 mapping_set_error(mapping, ret);
659out:
660 mpd->bio = bio;
661 return ret;
662}
663
664/**
665 * mpage_writepages - walk the list of dirty pages of the given address space & writepage() all of them
666 * @mapping: address space structure to write
667 * @wbc: subtract the number of written pages from *@wbc->nr_to_write
668 * @get_block: the filesystem's block mapper function.
669 * If this is NULL then use a_ops->writepage. Otherwise, go
670 * direct-to-BIO.
671 *
672 * This is a library function, which implements the writepages()
673 * address_space_operation.
674 *
675 * If a page is already under I/O, generic_writepages() skips it, even
676 * if it's dirty. This is desirable behaviour for memory-cleaning writeback,
677 * but it is INCORRECT for data-integrity system calls such as fsync(). fsync()
678 * and msync() need to guarantee that all the data which was dirty at the time
679 * the call was made get new I/O started against them. If wbc->sync_mode is
680 * WB_SYNC_ALL then we were called for data integrity and we must wait for
681 * existing IO to complete.
682 */
683int
684mpage_writepages(struct address_space *mapping,
685 struct writeback_control *wbc, get_block_t get_block)
686{
687 struct blk_plug plug;
688 int ret;
689
690 blk_start_plug(&plug);
691
692 if (!get_block)
693 ret = generic_writepages(mapping, wbc);
694 else {
695 struct mpage_data mpd = {
696 .bio = NULL,
697 .last_block_in_bio = 0,
698 .get_block = get_block,
699 .use_writepage = 1,
700 };
701
702 ret = write_cache_pages(mapping, wbc, __mpage_writepage, &mpd);
703 if (mpd.bio) {
704 int wr = (wbc->sync_mode == WB_SYNC_ALL ?
705 WRITE_SYNC : WRITE);
706 mpage_bio_submit(wr, mpd.bio);
707 }
708 }
709 blk_finish_plug(&plug);
710 return ret;
711}
712EXPORT_SYMBOL(mpage_writepages);
713
714int mpage_writepage(struct page *page, get_block_t get_block,
715 struct writeback_control *wbc)
716{
717 struct mpage_data mpd = {
718 .bio = NULL,
719 .last_block_in_bio = 0,
720 .get_block = get_block,
721 .use_writepage = 0,
722 };
723 int ret = __mpage_writepage(page, wbc, &mpd);
724 if (mpd.bio) {
725 int wr = (wbc->sync_mode == WB_SYNC_ALL ?
726 WRITE_SYNC : WRITE);
727 mpage_bio_submit(wr, mpd.bio);
728 }
729 return ret;
730}
731EXPORT_SYMBOL(mpage_writepage);