9p: rework client code to use new protocol support functions
[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                         clear_buffer_mapped(map_bh);
245                         continue;
246                 }
247
248                 /* some filesystems will copy data into the page during
249                  * the get_block call, in which case we don't want to
250                  * read it again.  map_buffer_to_page copies the data
251                  * we just collected from get_block into the page's buffers
252                  * so readpage doesn't have to repeat the get_block call
253                  */
254                 if (buffer_uptodate(map_bh)) {
255                         map_buffer_to_page(page, map_bh, page_block);
256                         goto confused;
257                 }
258         
259                 if (first_hole != blocks_per_page)
260                         goto confused;          /* hole -> non-hole */
261
262                 /* Contiguous blocks? */
263                 if (page_block && blocks[page_block-1] != map_bh->b_blocknr-1)
264                         goto confused;
265                 nblocks = map_bh->b_size >> blkbits;
266                 for (relative_block = 0; ; relative_block++) {
267                         if (relative_block == nblocks) {
268                                 clear_buffer_mapped(map_bh);
269                                 break;
270                         } else if (page_block == blocks_per_page)
271                                 break;
272                         blocks[page_block] = map_bh->b_blocknr+relative_block;
273                         page_block++;
274                         block_in_file++;
275                 }
276                 bdev = map_bh->b_bdev;
277         }
278
279         if (first_hole != blocks_per_page) {
280                 zero_user_segment(page, first_hole << blkbits, PAGE_CACHE_SIZE);
281                 if (first_hole == 0) {
282                         SetPageUptodate(page);
283                         unlock_page(page);
284                         goto out;
285                 }
286         } else if (fully_mapped) {
287                 SetPageMappedToDisk(page);
288         }
289
290         /*
291          * This page will go to BIO.  Do we need to send this BIO off first?
292          */
293         if (bio && (*last_block_in_bio != blocks[0] - 1))
294                 bio = mpage_bio_submit(READ, bio);
295
296 alloc_new:
297         if (bio == NULL) {
298                 bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
299                                 min_t(int, nr_pages, bio_get_nr_vecs(bdev)),
300                                 GFP_KERNEL);
301                 if (bio == NULL)
302                         goto confused;
303         }
304
305         length = first_hole << blkbits;
306         if (bio_add_page(bio, page, length, 0) < length) {
307                 bio = mpage_bio_submit(READ, bio);
308                 goto alloc_new;
309         }
310
311         if (buffer_boundary(map_bh) || (first_hole != blocks_per_page))
312                 bio = mpage_bio_submit(READ, bio);
313         else
314                 *last_block_in_bio = blocks[blocks_per_page - 1];
315 out:
316         return bio;
317
318 confused:
319         if (bio)
320                 bio = mpage_bio_submit(READ, bio);
321         if (!PageUptodate(page))
322                 block_read_full_page(page, get_block);
323         else
324                 unlock_page(page);
325         goto out;
326 }
327
328 /**
329  * mpage_readpages - populate an address space with some pages & start reads against them
330  * @mapping: the address_space
331  * @pages: The address of a list_head which contains the target pages.  These
332  *   pages have their ->index populated and are otherwise uninitialised.
333  *   The page at @pages->prev has the lowest file offset, and reads should be
334  *   issued in @pages->prev to @pages->next order.
335  * @nr_pages: The number of pages at *@pages
336  * @get_block: The filesystem's block mapper function.
337  *
338  * This function walks the pages and the blocks within each page, building and
339  * emitting large BIOs.
340  *
341  * If anything unusual happens, such as:
342  *
343  * - encountering a page which has buffers
344  * - encountering a page which has a non-hole after a hole
345  * - encountering a page with non-contiguous blocks
346  *
347  * then this code just gives up and calls the buffer_head-based read function.
348  * It does handle a page which has holes at the end - that is a common case:
349  * the end-of-file on blocksize < PAGE_CACHE_SIZE setups.
350  *
351  * BH_Boundary explanation:
352  *
353  * There is a problem.  The mpage read code assembles several pages, gets all
354  * their disk mappings, and then submits them all.  That's fine, but obtaining
355  * the disk mappings may require I/O.  Reads of indirect blocks, for example.
356  *
357  * So an mpage read of the first 16 blocks of an ext2 file will cause I/O to be
358  * submitted in the following order:
359  *      12 0 1 2 3 4 5 6 7 8 9 10 11 13 14 15 16
360  *
361  * because the indirect block has to be read to get the mappings of blocks
362  * 13,14,15,16.  Obviously, this impacts performance.
363  *
364  * So what we do it to allow the filesystem's get_block() function to set
365  * BH_Boundary when it maps block 11.  BH_Boundary says: mapping of the block
366  * after this one will require I/O against a block which is probably close to
367  * this one.  So you should push what I/O you have currently accumulated.
368  *
369  * This all causes the disk requests to be issued in the correct order.
370  */
371 int
372 mpage_readpages(struct address_space *mapping, struct list_head *pages,
373                                 unsigned nr_pages, get_block_t get_block)
374 {
375         struct bio *bio = NULL;
376         unsigned page_idx;
377         sector_t last_block_in_bio = 0;
378         struct buffer_head map_bh;
379         unsigned long first_logical_block = 0;
380
381         clear_buffer_mapped(&map_bh);
382         for (page_idx = 0; page_idx < nr_pages; page_idx++) {
383                 struct page *page = list_entry(pages->prev, struct page, lru);
384
385                 prefetchw(&page->flags);
386                 list_del(&page->lru);
387                 if (!add_to_page_cache_lru(page, mapping,
388                                         page->index, GFP_KERNEL)) {
389                         bio = do_mpage_readpage(bio, page,
390                                         nr_pages - page_idx,
391                                         &last_block_in_bio, &map_bh,
392                                         &first_logical_block,
393                                         get_block);
394                 }
395                 page_cache_release(page);
396         }
397         BUG_ON(!list_empty(pages));
398         if (bio)
399                 mpage_bio_submit(READ, bio);
400         return 0;
401 }
402 EXPORT_SYMBOL(mpage_readpages);
403
404 /*
405  * This isn't called much at all
406  */
407 int mpage_readpage(struct page *page, get_block_t get_block)
408 {
409         struct bio *bio = NULL;
410         sector_t last_block_in_bio = 0;
411         struct buffer_head map_bh;
412         unsigned long first_logical_block = 0;
413
414         clear_buffer_mapped(&map_bh);
415         bio = do_mpage_readpage(bio, page, 1, &last_block_in_bio,
416                         &map_bh, &first_logical_block, get_block);
417         if (bio)
418                 mpage_bio_submit(READ, bio);
419         return 0;
420 }
421 EXPORT_SYMBOL(mpage_readpage);
422
423 /*
424  * Writing is not so simple.
425  *
426  * If the page has buffers then they will be used for obtaining the disk
427  * mapping.  We only support pages which are fully mapped-and-dirty, with a
428  * special case for pages which are unmapped at the end: end-of-file.
429  *
430  * If the page has no buffers (preferred) then the page is mapped here.
431  *
432  * If all blocks are found to be contiguous then the page can go into the
433  * BIO.  Otherwise fall back to the mapping's writepage().
434  * 
435  * FIXME: This code wants an estimate of how many pages are still to be
436  * written, so it can intelligently allocate a suitably-sized BIO.  For now,
437  * just allocate full-size (16-page) BIOs.
438  */
439
440 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 invokation 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 EXPORT_SYMBOL(__mpage_writepage);
650
651 /**
652  * mpage_writepages - walk the list of dirty pages of the given address space & writepage() all of them
653  * @mapping: address space structure to write
654  * @wbc: subtract the number of written pages from *@wbc->nr_to_write
655  * @get_block: the filesystem's block mapper function.
656  *             If this is NULL then use a_ops->writepage.  Otherwise, go
657  *             direct-to-BIO.
658  *
659  * This is a library function, which implements the writepages()
660  * address_space_operation.
661  *
662  * If a page is already under I/O, generic_writepages() skips it, even
663  * if it's dirty.  This is desirable behaviour for memory-cleaning writeback,
664  * but it is INCORRECT for data-integrity system calls such as fsync().  fsync()
665  * and msync() need to guarantee that all the data which was dirty at the time
666  * the call was made get new I/O started against them.  If wbc->sync_mode is
667  * WB_SYNC_ALL then we were called for data integrity and we must wait for
668  * existing IO to complete.
669  */
670 int
671 mpage_writepages(struct address_space *mapping,
672                 struct writeback_control *wbc, get_block_t get_block)
673 {
674         int ret;
675
676         if (!get_block)
677                 ret = generic_writepages(mapping, wbc);
678         else {
679                 struct mpage_data mpd = {
680                         .bio = NULL,
681                         .last_block_in_bio = 0,
682                         .get_block = get_block,
683                         .use_writepage = 1,
684                 };
685
686                 ret = write_cache_pages(mapping, wbc, __mpage_writepage, &mpd);
687                 if (mpd.bio)
688                         mpage_bio_submit(WRITE, mpd.bio);
689         }
690         return ret;
691 }
692 EXPORT_SYMBOL(mpage_writepages);
693
694 int mpage_writepage(struct page *page, get_block_t get_block,
695         struct writeback_control *wbc)
696 {
697         struct mpage_data mpd = {
698                 .bio = NULL,
699                 .last_block_in_bio = 0,
700                 .get_block = get_block,
701                 .use_writepage = 0,
702         };
703         int ret = __mpage_writepage(page, wbc, &mpd);
704         if (mpd.bio)
705                 mpage_bio_submit(WRITE, mpd.bio);
706         return ret;
707 }
708 EXPORT_SYMBOL(mpage_writepage);