do_mpage_readpage(): remove useless clear_buffer_mapped() call
[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/bio.h>
20 #include <linux/fs.h>
21 #include <linux/buffer_head.h>
22 #include <linux/blkdev.h>
23 #include <linux/highmem.h>
24 #include <linux/prefetch.h>
25 #include <linux/mpage.h>
26 #include <linux/writeback.h>
27 #include <linux/backing-dev.h>
28 #include <linux/pagevec.h>
29
30 /*
31  * I/O completion handler for multipage BIOs.
32  *
33  * The mpage code never puts partial pages into a BIO (except for end-of-file).
34  * If a page does not map to a contiguous run of blocks then it simply falls
35  * back to block_read_full_page().
36  *
37  * Why is this?  If a page's completion depends on a number of different BIOs
38  * which can complete in any order (or at the same time) then determining the
39  * status of that page is hard.  See end_buffer_async_read() for the details.
40  * There is no point in duplicating all that complexity.
41  */
42 static void mpage_end_io_read(struct bio *bio, int err)
43 {
44         const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
45         struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
46
47         do {
48                 struct page *page = bvec->bv_page;
49
50                 if (--bvec >= bio->bi_io_vec)
51                         prefetchw(&bvec->bv_page->flags);
52
53                 if (uptodate) {
54                         SetPageUptodate(page);
55                 } else {
56                         ClearPageUptodate(page);
57                         SetPageError(page);
58                 }
59                 unlock_page(page);
60         } while (bvec >= bio->bi_io_vec);
61         bio_put(bio);
62 }
63
64 static void mpage_end_io_write(struct bio *bio, int err)
65 {
66         const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
67         struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
68
69         do {
70                 struct page *page = bvec->bv_page;
71
72                 if (--bvec >= bio->bi_io_vec)
73                         prefetchw(&bvec->bv_page->flags);
74
75                 if (!uptodate){
76                         SetPageError(page);
77                         if (page->mapping)
78                                 set_bit(AS_EIO, &page->mapping->flags);
79                 }
80                 end_page_writeback(page);
81         } while (bvec >= bio->bi_io_vec);
82         bio_put(bio);
83 }
84
85 struct bio *mpage_bio_submit(int rw, struct bio *bio)
86 {
87         bio->bi_end_io = mpage_end_io_read;
88         if (rw == WRITE)
89                 bio->bi_end_io = mpage_end_io_write;
90         submit_bio(rw, bio);
91         return NULL;
92 }
93 EXPORT_SYMBOL(mpage_bio_submit);
94
95 static struct bio *
96 mpage_alloc(struct block_device *bdev,
97                 sector_t first_sector, int nr_vecs,
98                 gfp_t gfp_flags)
99 {
100         struct bio *bio;
101
102         bio = bio_alloc(gfp_flags, nr_vecs);
103
104         if (bio == NULL && (current->flags & PF_MEMALLOC)) {
105                 while (!bio && (nr_vecs /= 2))
106                         bio = bio_alloc(gfp_flags, nr_vecs);
107         }
108
109         if (bio) {
110                 bio->bi_bdev = bdev;
111                 bio->bi_sector = first_sector;
112         }
113         return bio;
114 }
115
116 /*
117  * support function for mpage_readpages.  The fs supplied get_block might
118  * return an up to date buffer.  This is used to map that buffer into
119  * the page, which allows readpage to avoid triggering a duplicate call
120  * to get_block.
121  *
122  * The idea is to avoid adding buffers to pages that don't already have
123  * them.  So when the buffer is up to date and the page size == block size,
124  * this marks the page up to date instead of adding new buffers.
125  */
126 static void 
127 map_buffer_to_page(struct page *page, struct buffer_head *bh, int page_block) 
128 {
129         struct inode *inode = page->mapping->host;
130         struct buffer_head *page_bh, *head;
131         int block = 0;
132
133         if (!page_has_buffers(page)) {
134                 /*
135                  * don't make any buffers if there is only one buffer on
136                  * the page and the page just needs to be set up to date
137                  */
138                 if (inode->i_blkbits == PAGE_CACHE_SHIFT && 
139                     buffer_uptodate(bh)) {
140                         SetPageUptodate(page);    
141                         return;
142                 }
143                 create_empty_buffers(page, 1 << inode->i_blkbits, 0);
144         }
145         head = page_buffers(page);
146         page_bh = head;
147         do {
148                 if (block == page_block) {
149                         page_bh->b_state = bh->b_state;
150                         page_bh->b_bdev = bh->b_bdev;
151                         page_bh->b_blocknr = bh->b_blocknr;
152                         break;
153                 }
154                 page_bh = page_bh->b_this_page;
155                 block++;
156         } while (page_bh != head);
157 }
158
159 /*
160  * This is the worker routine which does all the work of mapping the disk
161  * blocks and constructs largest possible bios, submits them for IO if the
162  * blocks are not contiguous on the disk.
163  *
164  * We pass a buffer_head back and forth and use its buffer_mapped() flag to
165  * represent the validity of its disk mapping and to decide when to do the next
166  * get_block() call.
167  */
168 static struct bio *
169 do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
170                 sector_t *last_block_in_bio, struct buffer_head *map_bh,
171                 unsigned long *first_logical_block, get_block_t get_block)
172 {
173         struct inode *inode = page->mapping->host;
174         const unsigned blkbits = inode->i_blkbits;
175         const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits;
176         const unsigned blocksize = 1 << blkbits;
177         sector_t block_in_file;
178         sector_t last_block;
179         sector_t last_block_in_file;
180         sector_t blocks[MAX_BUF_PER_PAGE];
181         unsigned page_block;
182         unsigned first_hole = blocks_per_page;
183         struct block_device *bdev = NULL;
184         int length;
185         int fully_mapped = 1;
186         unsigned nblocks;
187         unsigned relative_block;
188
189         if (page_has_buffers(page))
190                 goto confused;
191
192         block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
193         last_block = block_in_file + nr_pages * blocks_per_page;
194         last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits;
195         if (last_block > last_block_in_file)
196                 last_block = last_block_in_file;
197         page_block = 0;
198
199         /*
200          * Map blocks using the result from the previous get_blocks call first.
201          */
202         nblocks = map_bh->b_size >> blkbits;
203         if (buffer_mapped(map_bh) && block_in_file > *first_logical_block &&
204                         block_in_file < (*first_logical_block + nblocks)) {
205                 unsigned map_offset = block_in_file - *first_logical_block;
206                 unsigned last = nblocks - map_offset;
207
208                 for (relative_block = 0; ; relative_block++) {
209                         if (relative_block == last) {
210                                 clear_buffer_mapped(map_bh);
211                                 break;
212                         }
213                         if (page_block == blocks_per_page)
214                                 break;
215                         blocks[page_block] = map_bh->b_blocknr + map_offset +
216                                                 relative_block;
217                         page_block++;
218                         block_in_file++;
219                 }
220                 bdev = map_bh->b_bdev;
221         }
222
223         /*
224          * Then do more get_blocks calls until we are done with this page.
225          */
226         map_bh->b_page = page;
227         while (page_block < blocks_per_page) {
228                 map_bh->b_state = 0;
229                 map_bh->b_size = 0;
230
231                 if (block_in_file < last_block) {
232                         map_bh->b_size = (last_block-block_in_file) << blkbits;
233                         if (get_block(inode, block_in_file, map_bh, 0))
234                                 goto confused;
235                         *first_logical_block = block_in_file;
236                 }
237
238                 if (!buffer_mapped(map_bh)) {
239                         fully_mapped = 0;
240                         if (first_hole == blocks_per_page)
241                                 first_hole = page_block;
242                         page_block++;
243                         block_in_file++;
244                         continue;
245                 }
246
247                 /* some filesystems will copy data into the page during
248                  * the get_block call, in which case we don't want to
249                  * read it again.  map_buffer_to_page copies the data
250                  * we just collected from get_block into the page's buffers
251                  * so readpage doesn't have to repeat the get_block call
252                  */
253                 if (buffer_uptodate(map_bh)) {
254                         map_buffer_to_page(page, map_bh, page_block);
255                         goto confused;
256                 }
257         
258                 if (first_hole != blocks_per_page)
259                         goto confused;          /* hole -> non-hole */
260
261                 /* Contiguous blocks? */
262                 if (page_block && blocks[page_block-1] != map_bh->b_blocknr-1)
263                         goto confused;
264                 nblocks = map_bh->b_size >> blkbits;
265                 for (relative_block = 0; ; relative_block++) {
266                         if (relative_block == nblocks) {
267                                 clear_buffer_mapped(map_bh);
268                                 break;
269                         } else if (page_block == blocks_per_page)
270                                 break;
271                         blocks[page_block] = map_bh->b_blocknr+relative_block;
272                         page_block++;
273                         block_in_file++;
274                 }
275                 bdev = map_bh->b_bdev;
276         }
277
278         if (first_hole != blocks_per_page) {
279                 zero_user_segment(page, first_hole << blkbits, PAGE_CACHE_SIZE);
280                 if (first_hole == 0) {
281                         SetPageUptodate(page);
282                         unlock_page(page);
283                         goto out;
284                 }
285         } else if (fully_mapped) {
286                 SetPageMappedToDisk(page);
287         }
288
289         /*
290          * This page will go to BIO.  Do we need to send this BIO off first?
291          */
292         if (bio && (*last_block_in_bio != blocks[0] - 1))
293                 bio = mpage_bio_submit(READ, bio);
294
295 alloc_new:
296         if (bio == NULL) {
297                 bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
298                                 min_t(int, nr_pages, bio_get_nr_vecs(bdev)),
299                                 GFP_KERNEL);
300                 if (bio == NULL)
301                         goto confused;
302         }
303
304         length = first_hole << blkbits;
305         if (bio_add_page(bio, page, length, 0) < length) {
306                 bio = mpage_bio_submit(READ, bio);
307                 goto alloc_new;
308         }
309
310         relative_block = block_in_file - *first_logical_block;
311         nblocks = map_bh->b_size >> blkbits;
312         if ((buffer_boundary(map_bh) && relative_block == nblocks) ||
313             (first_hole != blocks_per_page))
314                 bio = mpage_bio_submit(READ, bio);
315         else
316                 *last_block_in_bio = blocks[blocks_per_page - 1];
317 out:
318         return bio;
319
320 confused:
321         if (bio)
322                 bio = mpage_bio_submit(READ, bio);
323         if (!PageUptodate(page))
324                 block_read_full_page(page, get_block);
325         else
326                 unlock_page(page);
327         goto out;
328 }
329
330 /**
331  * mpage_readpages - populate an address space with some pages & start reads against them
332  * @mapping: the address_space
333  * @pages: The address of a list_head which contains the target pages.  These
334  *   pages have their ->index populated and are otherwise uninitialised.
335  *   The page at @pages->prev has the lowest file offset, and reads should be
336  *   issued in @pages->prev to @pages->next order.
337  * @nr_pages: The number of pages at *@pages
338  * @get_block: The filesystem's block mapper function.
339  *
340  * This function walks the pages and the blocks within each page, building and
341  * emitting large BIOs.
342  *
343  * If anything unusual happens, such as:
344  *
345  * - encountering a page which has buffers
346  * - encountering a page which has a non-hole after a hole
347  * - encountering a page with non-contiguous blocks
348  *
349  * then this code just gives up and calls the buffer_head-based read function.
350  * It does handle a page which has holes at the end - that is a common case:
351  * the end-of-file on blocksize < PAGE_CACHE_SIZE setups.
352  *
353  * BH_Boundary explanation:
354  *
355  * There is a problem.  The mpage read code assembles several pages, gets all
356  * their disk mappings, and then submits them all.  That's fine, but obtaining
357  * the disk mappings may require I/O.  Reads of indirect blocks, for example.
358  *
359  * So an mpage read of the first 16 blocks of an ext2 file will cause I/O to be
360  * submitted in the following order:
361  *      12 0 1 2 3 4 5 6 7 8 9 10 11 13 14 15 16
362  *
363  * because the indirect block has to be read to get the mappings of blocks
364  * 13,14,15,16.  Obviously, this impacts performance.
365  *
366  * So what we do it to allow the filesystem's get_block() function to set
367  * BH_Boundary when it maps block 11.  BH_Boundary says: mapping of the block
368  * after this one will require I/O against a block which is probably close to
369  * this one.  So you should push what I/O you have currently accumulated.
370  *
371  * This all causes the disk requests to be issued in the correct order.
372  */
373 int
374 mpage_readpages(struct address_space *mapping, struct list_head *pages,
375                                 unsigned nr_pages, get_block_t get_block)
376 {
377         struct bio *bio = NULL;
378         unsigned page_idx;
379         sector_t last_block_in_bio = 0;
380         struct buffer_head map_bh;
381         unsigned long first_logical_block = 0;
382
383         clear_buffer_mapped(&map_bh);
384         for (page_idx = 0; page_idx < nr_pages; page_idx++) {
385                 struct page *page = list_entry(pages->prev, struct page, lru);
386
387                 prefetchw(&page->flags);
388                 list_del(&page->lru);
389                 if (!add_to_page_cache_lru(page, mapping,
390                                         page->index, GFP_KERNEL)) {
391                         bio = do_mpage_readpage(bio, page,
392                                         nr_pages - page_idx,
393                                         &last_block_in_bio, &map_bh,
394                                         &first_logical_block,
395                                         get_block);
396                 }
397                 page_cache_release(page);
398         }
399         BUG_ON(!list_empty(pages));
400         if (bio)
401                 mpage_bio_submit(READ, bio);
402         return 0;
403 }
404 EXPORT_SYMBOL(mpage_readpages);
405
406 /*
407  * This isn't called much at all
408  */
409 int mpage_readpage(struct page *page, get_block_t get_block)
410 {
411         struct bio *bio = NULL;
412         sector_t last_block_in_bio = 0;
413         struct buffer_head map_bh;
414         unsigned long first_logical_block = 0;
415
416         clear_buffer_mapped(&map_bh);
417         bio = do_mpage_readpage(bio, page, 1, &last_block_in_bio,
418                         &map_bh, &first_logical_block, get_block);
419         if (bio)
420                 mpage_bio_submit(READ, bio);
421         return 0;
422 }
423 EXPORT_SYMBOL(mpage_readpage);
424
425 /*
426  * Writing is not so simple.
427  *
428  * If the page has buffers then they will be used for obtaining the disk
429  * mapping.  We only support pages which are fully mapped-and-dirty, with a
430  * special case for pages which are unmapped at the end: end-of-file.
431  *
432  * If the page has no buffers (preferred) then the page is mapped here.
433  *
434  * If all blocks are found to be contiguous then the page can go into the
435  * BIO.  Otherwise fall back to the mapping's writepage().
436  * 
437  * FIXME: This code wants an estimate of how many pages are still to be
438  * written, so it can intelligently allocate a suitably-sized BIO.  For now,
439  * just allocate full-size (16-page) BIOs.
440  */
441
442 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
551 page_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 invokation 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
575 alloc_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
633 confused:
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);
647 out:
648         mpd->bio = bio;
649         return ret;
650 }
651 EXPORT_SYMBOL(__mpage_writepage);
652
653 /**
654  * mpage_writepages - walk the list of dirty pages of the given address space & writepage() all of them
655  * @mapping: address space structure to write
656  * @wbc: subtract the number of written pages from *@wbc->nr_to_write
657  * @get_block: the filesystem's block mapper function.
658  *             If this is NULL then use a_ops->writepage.  Otherwise, go
659  *             direct-to-BIO.
660  *
661  * This is a library function, which implements the writepages()
662  * address_space_operation.
663  *
664  * If a page is already under I/O, generic_writepages() skips it, even
665  * if it's dirty.  This is desirable behaviour for memory-cleaning writeback,
666  * but it is INCORRECT for data-integrity system calls such as fsync().  fsync()
667  * and msync() need to guarantee that all the data which was dirty at the time
668  * the call was made get new I/O started against them.  If wbc->sync_mode is
669  * WB_SYNC_ALL then we were called for data integrity and we must wait for
670  * existing IO to complete.
671  */
672 int
673 mpage_writepages(struct address_space *mapping,
674                 struct writeback_control *wbc, get_block_t get_block)
675 {
676         int ret;
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         return ret;
693 }
694 EXPORT_SYMBOL(mpage_writepages);
695
696 int mpage_writepage(struct page *page, get_block_t get_block,
697         struct writeback_control *wbc)
698 {
699         struct mpage_data mpd = {
700                 .bio = NULL,
701                 .last_block_in_bio = 0,
702                 .get_block = get_block,
703                 .use_writepage = 0,
704         };
705         int ret = __mpage_writepage(page, wbc, &mpd);
706         if (mpd.bio)
707                 mpage_bio_submit(WRITE, mpd.bio);
708         return ret;
709 }
710 EXPORT_SYMBOL(mpage_writepage);