Merge branch 'for-2.6.39/core' of git://git.kernel.dk/linux-2.6-block
[linux-2.6.git] / fs / mpage.c
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/module.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
31 /*
32  * I/O completion handler for multipage BIOs.
33  *
34  * The mpage code never puts partial pages into a BIO (except for end-of-file).
35  * If a page does not map to a contiguous run of blocks then it simply falls
36  * back to block_read_full_page().
37  *
38  * Why is this?  If a page's completion depends on a number of different BIOs
39  * which can complete in any order (or at the same time) then determining the
40  * status of that page is hard.  See end_buffer_async_read() for the details.
41  * There is no point in duplicating all that complexity.
42  */
43 static void mpage_end_io(struct bio *bio, int err)
44 {
45         const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
46         struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
47
48         do {
49                 struct page *page = bvec->bv_page;
50
51                 if (--bvec >= bio->bi_io_vec)
52                         prefetchw(&bvec->bv_page->flags);
53                 if (bio_data_dir(bio) == READ) {
54                         if (uptodate) {
55                                 SetPageUptodate(page);
56                         } else {
57                                 ClearPageUptodate(page);
58                                 SetPageError(page);
59                         }
60                         unlock_page(page);
61                 } else { /* bio_data_dir(bio) == WRITE */
62                         if (!uptodate) {
63                                 SetPageError(page);
64                                 if (page->mapping)
65                                         set_bit(AS_EIO, &page->mapping->flags);
66                         }
67                         end_page_writeback(page);
68                 }
69         } while (bvec >= bio->bi_io_vec);
70         bio_put(bio);
71 }
72
73 static 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
80 static struct bio *
81 mpage_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_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  */
111 static void 
112 map_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  */
153 static struct bio *
154 do_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         /*
275          * This page will go to BIO.  Do we need to send this BIO off first?
276          */
277         if (bio && (*last_block_in_bio != blocks[0] - 1))
278                 bio = mpage_bio_submit(READ, bio);
279
280 alloc_new:
281         if (bio == NULL) {
282                 bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
283                                 min_t(int, nr_pages, bio_get_nr_vecs(bdev)),
284                                 GFP_KERNEL);
285                 if (bio == NULL)
286                         goto confused;
287         }
288
289         length = first_hole << blkbits;
290         if (bio_add_page(bio, page, length, 0) < length) {
291                 bio = mpage_bio_submit(READ, bio);
292                 goto alloc_new;
293         }
294
295         relative_block = block_in_file - *first_logical_block;
296         nblocks = map_bh->b_size >> blkbits;
297         if ((buffer_boundary(map_bh) && relative_block == nblocks) ||
298             (first_hole != blocks_per_page))
299                 bio = mpage_bio_submit(READ, bio);
300         else
301                 *last_block_in_bio = blocks[blocks_per_page - 1];
302 out:
303         return bio;
304
305 confused:
306         if (bio)
307                 bio = mpage_bio_submit(READ, bio);
308         if (!PageUptodate(page))
309                 block_read_full_page(page, get_block);
310         else
311                 unlock_page(page);
312         goto out;
313 }
314
315 /**
316  * mpage_readpages - populate an address space with some pages & start reads against them
317  * @mapping: the address_space
318  * @pages: The address of a list_head which contains the target pages.  These
319  *   pages have their ->index populated and are otherwise uninitialised.
320  *   The page at @pages->prev has the lowest file offset, and reads should be
321  *   issued in @pages->prev to @pages->next order.
322  * @nr_pages: The number of pages at *@pages
323  * @get_block: The filesystem's block mapper function.
324  *
325  * This function walks the pages and the blocks within each page, building and
326  * emitting large BIOs.
327  *
328  * If anything unusual happens, such as:
329  *
330  * - encountering a page which has buffers
331  * - encountering a page which has a non-hole after a hole
332  * - encountering a page with non-contiguous blocks
333  *
334  * then this code just gives up and calls the buffer_head-based read function.
335  * It does handle a page which has holes at the end - that is a common case:
336  * the end-of-file on blocksize < PAGE_CACHE_SIZE setups.
337  *
338  * BH_Boundary explanation:
339  *
340  * There is a problem.  The mpage read code assembles several pages, gets all
341  * their disk mappings, and then submits them all.  That's fine, but obtaining
342  * the disk mappings may require I/O.  Reads of indirect blocks, for example.
343  *
344  * So an mpage read of the first 16 blocks of an ext2 file will cause I/O to be
345  * submitted in the following order:
346  *      12 0 1 2 3 4 5 6 7 8 9 10 11 13 14 15 16
347  *
348  * because the indirect block has to be read to get the mappings of blocks
349  * 13,14,15,16.  Obviously, this impacts performance.
350  *
351  * So what we do it to allow the filesystem's get_block() function to set
352  * BH_Boundary when it maps block 11.  BH_Boundary says: mapping of the block
353  * after this one will require I/O against a block which is probably close to
354  * this one.  So you should push what I/O you have currently accumulated.
355  *
356  * This all causes the disk requests to be issued in the correct order.
357  */
358 int
359 mpage_readpages(struct address_space *mapping, struct list_head *pages,
360                                 unsigned nr_pages, get_block_t get_block)
361 {
362         struct bio *bio = NULL;
363         unsigned page_idx;
364         sector_t last_block_in_bio = 0;
365         struct buffer_head map_bh;
366         unsigned long first_logical_block = 0;
367         struct blk_plug plug;
368
369         blk_start_plug(&plug);
370
371         map_bh.b_state = 0;
372         map_bh.b_size = 0;
373         for (page_idx = 0; page_idx < nr_pages; page_idx++) {
374                 struct page *page = list_entry(pages->prev, struct page, lru);
375
376                 prefetchw(&page->flags);
377                 list_del(&page->lru);
378                 if (!add_to_page_cache_lru(page, mapping,
379                                         page->index, GFP_KERNEL)) {
380                         bio = do_mpage_readpage(bio, page,
381                                         nr_pages - page_idx,
382                                         &last_block_in_bio, &map_bh,
383                                         &first_logical_block,
384                                         get_block);
385                 }
386                 page_cache_release(page);
387         }
388         BUG_ON(!list_empty(pages));
389         if (bio)
390                 mpage_bio_submit(READ, bio);
391         blk_finish_plug(&plug);
392         return 0;
393 }
394 EXPORT_SYMBOL(mpage_readpages);
395
396 /*
397  * This isn't called much at all
398  */
399 int mpage_readpage(struct page *page, get_block_t get_block)
400 {
401         struct bio *bio = NULL;
402         sector_t last_block_in_bio = 0;
403         struct buffer_head map_bh;
404         unsigned long first_logical_block = 0;
405
406         map_bh.b_state = 0;
407         map_bh.b_size = 0;
408         bio = do_mpage_readpage(bio, page, 1, &last_block_in_bio,
409                         &map_bh, &first_logical_block, get_block);
410         if (bio)
411                 mpage_bio_submit(READ, bio);
412         return 0;
413 }
414 EXPORT_SYMBOL(mpage_readpage);
415
416 /*
417  * Writing is not so simple.
418  *
419  * If the page has buffers then they will be used for obtaining the disk
420  * mapping.  We only support pages which are fully mapped-and-dirty, with a
421  * special case for pages which are unmapped at the end: end-of-file.
422  *
423  * If the page has no buffers (preferred) then the page is mapped here.
424  *
425  * If all blocks are found to be contiguous then the page can go into the
426  * BIO.  Otherwise fall back to the mapping's writepage().
427  * 
428  * FIXME: This code wants an estimate of how many pages are still to be
429  * written, so it can intelligently allocate a suitably-sized BIO.  For now,
430  * just allocate full-size (16-page) BIOs.
431  */
432
433 struct mpage_data {
434         struct bio *bio;
435         sector_t last_block_in_bio;
436         get_block_t *get_block;
437         unsigned use_writepage;
438 };
439
440 static int __mpage_writepage(struct page *page, struct writeback_control *wbc,
441                       void *data)
442 {
443         struct mpage_data *mpd = data;
444         struct bio *bio = mpd->bio;
445         struct address_space *mapping = page->mapping;
446         struct inode *inode = page->mapping->host;
447         const unsigned blkbits = inode->i_blkbits;
448         unsigned long end_index;
449         const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits;
450         sector_t last_block;
451         sector_t block_in_file;
452         sector_t blocks[MAX_BUF_PER_PAGE];
453         unsigned page_block;
454         unsigned first_unmapped = blocks_per_page;
455         struct block_device *bdev = NULL;
456         int boundary = 0;
457         sector_t boundary_block = 0;
458         struct block_device *boundary_bdev = NULL;
459         int length;
460         struct buffer_head map_bh;
461         loff_t i_size = i_size_read(inode);
462         int ret = 0;
463
464         if (page_has_buffers(page)) {
465                 struct buffer_head *head = page_buffers(page);
466                 struct buffer_head *bh = head;
467
468                 /* If they're all mapped and dirty, do it */
469                 page_block = 0;
470                 do {
471                         BUG_ON(buffer_locked(bh));
472                         if (!buffer_mapped(bh)) {
473                                 /*
474                                  * unmapped dirty buffers are created by
475                                  * __set_page_dirty_buffers -> mmapped data
476                                  */
477                                 if (buffer_dirty(bh))
478                                         goto confused;
479                                 if (first_unmapped == blocks_per_page)
480                                         first_unmapped = page_block;
481                                 continue;
482                         }
483
484                         if (first_unmapped != blocks_per_page)
485                                 goto confused;  /* hole -> non-hole */
486
487                         if (!buffer_dirty(bh) || !buffer_uptodate(bh))
488                                 goto confused;
489                         if (page_block) {
490                                 if (bh->b_blocknr != blocks[page_block-1] + 1)
491                                         goto confused;
492                         }
493                         blocks[page_block++] = bh->b_blocknr;
494                         boundary = buffer_boundary(bh);
495                         if (boundary) {
496                                 boundary_block = bh->b_blocknr;
497                                 boundary_bdev = bh->b_bdev;
498                         }
499                         bdev = bh->b_bdev;
500                 } while ((bh = bh->b_this_page) != head);
501
502                 if (first_unmapped)
503                         goto page_is_mapped;
504
505                 /*
506                  * Page has buffers, but they are all unmapped. The page was
507                  * created by pagein or read over a hole which was handled by
508                  * block_read_full_page().  If this address_space is also
509                  * using mpage_readpages then this can rarely happen.
510                  */
511                 goto confused;
512         }
513
514         /*
515          * The page has no buffers: map it to disk
516          */
517         BUG_ON(!PageUptodate(page));
518         block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
519         last_block = (i_size - 1) >> blkbits;
520         map_bh.b_page = page;
521         for (page_block = 0; page_block < blocks_per_page; ) {
522
523                 map_bh.b_state = 0;
524                 map_bh.b_size = 1 << blkbits;
525                 if (mpd->get_block(inode, block_in_file, &map_bh, 1))
526                         goto confused;
527                 if (buffer_new(&map_bh))
528                         unmap_underlying_metadata(map_bh.b_bdev,
529                                                 map_bh.b_blocknr);
530                 if (buffer_boundary(&map_bh)) {
531                         boundary_block = map_bh.b_blocknr;
532                         boundary_bdev = map_bh.b_bdev;
533                 }
534                 if (page_block) {
535                         if (map_bh.b_blocknr != blocks[page_block-1] + 1)
536                                 goto confused;
537                 }
538                 blocks[page_block++] = map_bh.b_blocknr;
539                 boundary = buffer_boundary(&map_bh);
540                 bdev = map_bh.b_bdev;
541                 if (block_in_file == last_block)
542                         break;
543                 block_in_file++;
544         }
545         BUG_ON(page_block == 0);
546
547         first_unmapped = page_block;
548
549 page_is_mapped:
550         end_index = i_size >> PAGE_CACHE_SHIFT;
551         if (page->index >= end_index) {
552                 /*
553                  * The page straddles i_size.  It must be zeroed out on each
554                  * and every writepage invocation because it may be mmapped.
555                  * "A file is mapped in multiples of the page size.  For a file
556                  * that is not a multiple of the page size, the remaining memory
557                  * is zeroed when mapped, and writes to that region are not
558                  * written out to the file."
559                  */
560                 unsigned offset = i_size & (PAGE_CACHE_SIZE - 1);
561
562                 if (page->index > end_index || !offset)
563                         goto confused;
564                 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
565         }
566
567         /*
568          * This page will go to BIO.  Do we need to send this BIO off first?
569          */
570         if (bio && mpd->last_block_in_bio != blocks[0] - 1)
571                 bio = mpage_bio_submit(WRITE, bio);
572
573 alloc_new:
574         if (bio == NULL) {
575                 bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
576                                 bio_get_nr_vecs(bdev), GFP_NOFS|__GFP_HIGH);
577                 if (bio == NULL)
578                         goto confused;
579         }
580
581         /*
582          * Must try to add the page before marking the buffer clean or
583          * the confused fail path above (OOM) will be very confused when
584          * it finds all bh marked clean (i.e. it will not write anything)
585          */
586         length = first_unmapped << blkbits;
587         if (bio_add_page(bio, page, length, 0) < length) {
588                 bio = mpage_bio_submit(WRITE, bio);
589                 goto alloc_new;
590         }
591
592         /*
593          * OK, we have our BIO, so we can now mark the buffers clean.  Make
594          * sure to only clean buffers which we know we'll be writing.
595          */
596         if (page_has_buffers(page)) {
597                 struct buffer_head *head = page_buffers(page);
598                 struct buffer_head *bh = head;
599                 unsigned buffer_counter = 0;
600
601                 do {
602                         if (buffer_counter++ == first_unmapped)
603                                 break;
604                         clear_buffer_dirty(bh);
605                         bh = bh->b_this_page;
606                 } while (bh != head);
607
608                 /*
609                  * we cannot drop the bh if the page is not uptodate
610                  * or a concurrent readpage would fail to serialize with the bh
611                  * and it would read from disk before we reach the platter.
612                  */
613                 if (buffer_heads_over_limit && PageUptodate(page))
614                         try_to_free_buffers(page);
615         }
616
617         BUG_ON(PageWriteback(page));
618         set_page_writeback(page);
619         unlock_page(page);
620         if (boundary || (first_unmapped != blocks_per_page)) {
621                 bio = mpage_bio_submit(WRITE, bio);
622                 if (boundary_block) {
623                         write_boundary_block(boundary_bdev,
624                                         boundary_block, 1 << blkbits);
625                 }
626         } else {
627                 mpd->last_block_in_bio = blocks[blocks_per_page - 1];
628         }
629         goto out;
630
631 confused:
632         if (bio)
633                 bio = mpage_bio_submit(WRITE, bio);
634
635         if (mpd->use_writepage) {
636                 ret = mapping->a_ops->writepage(page, wbc);
637         } else {
638                 ret = -EAGAIN;
639                 goto out;
640         }
641         /*
642          * The caller has a ref on the inode, so *mapping is stable
643          */
644         mapping_set_error(mapping, ret);
645 out:
646         mpd->bio = bio;
647         return ret;
648 }
649
650 /**
651  * mpage_writepages - walk the list of dirty pages of the given address space & writepage() all of them
652  * @mapping: address space structure to write
653  * @wbc: subtract the number of written pages from *@wbc->nr_to_write
654  * @get_block: the filesystem's block mapper function.
655  *             If this is NULL then use a_ops->writepage.  Otherwise, go
656  *             direct-to-BIO.
657  *
658  * This is a library function, which implements the writepages()
659  * address_space_operation.
660  *
661  * If a page is already under I/O, generic_writepages() skips it, even
662  * if it's dirty.  This is desirable behaviour for memory-cleaning writeback,
663  * but it is INCORRECT for data-integrity system calls such as fsync().  fsync()
664  * and msync() need to guarantee that all the data which was dirty at the time
665  * the call was made get new I/O started against them.  If wbc->sync_mode is
666  * WB_SYNC_ALL then we were called for data integrity and we must wait for
667  * existing IO to complete.
668  */
669 int
670 mpage_writepages(struct address_space *mapping,
671                 struct writeback_control *wbc, get_block_t get_block)
672 {
673         struct blk_plug plug;
674         int ret;
675
676         blk_start_plug(&plug);
677
678         if (!get_block)
679                 ret = generic_writepages(mapping, wbc);
680         else {
681                 struct mpage_data mpd = {
682                         .bio = NULL,
683                         .last_block_in_bio = 0,
684                         .get_block = get_block,
685                         .use_writepage = 1,
686                 };
687
688                 ret = write_cache_pages(mapping, wbc, __mpage_writepage, &mpd);
689                 if (mpd.bio)
690                         mpage_bio_submit(WRITE, mpd.bio);
691         }
692         blk_finish_plug(&plug);
693         return ret;
694 }
695 EXPORT_SYMBOL(mpage_writepages);
696
697 int mpage_writepage(struct page *page, get_block_t get_block,
698         struct writeback_control *wbc)
699 {
700         struct mpage_data mpd = {
701                 .bio = NULL,
702                 .last_block_in_bio = 0,
703                 .get_block = get_block,
704                 .use_writepage = 0,
705         };
706         int ret = __mpage_writepage(page, wbc, &mpd);
707         if (mpd.bio)
708                 mpage_bio_submit(WRITE, mpd.bio);
709         return ret;
710 }
711 EXPORT_SYMBOL(mpage_writepage);