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