debugfs: fix refcount imbalance in start_creating
[firefly-linux-kernel-4.4.55.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/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 #include "internal.h"
32
33 /*
34  * I/O completion handler for multipage BIOs.
35  *
36  * The mpage code never puts partial pages into a BIO (except for end-of-file).
37  * If a page does not map to a contiguous run of blocks then it simply falls
38  * back to block_read_full_page().
39  *
40  * Why is this?  If a page's completion depends on a number of different BIOs
41  * which can complete in any order (or at the same time) then determining the
42  * status of that page is hard.  See end_buffer_async_read() for the details.
43  * There is no point in duplicating all that complexity.
44  */
45 static void mpage_end_io(struct bio *bio)
46 {
47         struct bio_vec *bv;
48         int i;
49
50         bio_for_each_segment_all(bv, bio, i) {
51                 struct page *page = bv->bv_page;
52                 page_endio(page, bio_data_dir(bio), bio->bi_error);
53         }
54
55         bio_put(bio);
56 }
57
58 static struct bio *mpage_bio_submit(int rw, struct bio *bio)
59 {
60         bio->bi_end_io = mpage_end_io;
61         guard_bio_eod(rw, bio);
62         submit_bio(rw, bio);
63         return NULL;
64 }
65
66 static struct bio *
67 mpage_alloc(struct block_device *bdev,
68                 sector_t first_sector, int nr_vecs,
69                 gfp_t gfp_flags)
70 {
71         struct bio *bio;
72
73         bio = bio_alloc(gfp_flags, nr_vecs);
74
75         if (bio == NULL && (current->flags & PF_MEMALLOC)) {
76                 while (!bio && (nr_vecs /= 2))
77                         bio = bio_alloc(gfp_flags, nr_vecs);
78         }
79
80         if (bio) {
81                 bio->bi_bdev = bdev;
82                 bio->bi_iter.bi_sector = first_sector;
83         }
84         return bio;
85 }
86
87 /*
88  * support function for mpage_readpages.  The fs supplied get_block might
89  * return an up to date buffer.  This is used to map that buffer into
90  * the page, which allows readpage to avoid triggering a duplicate call
91  * to get_block.
92  *
93  * The idea is to avoid adding buffers to pages that don't already have
94  * them.  So when the buffer is up to date and the page size == block size,
95  * this marks the page up to date instead of adding new buffers.
96  */
97 static void 
98 map_buffer_to_page(struct page *page, struct buffer_head *bh, int page_block) 
99 {
100         struct inode *inode = page->mapping->host;
101         struct buffer_head *page_bh, *head;
102         int block = 0;
103
104         if (!page_has_buffers(page)) {
105                 /*
106                  * don't make any buffers if there is only one buffer on
107                  * the page and the page just needs to be set up to date
108                  */
109                 if (inode->i_blkbits == PAGE_CACHE_SHIFT && 
110                     buffer_uptodate(bh)) {
111                         SetPageUptodate(page);    
112                         return;
113                 }
114                 create_empty_buffers(page, 1 << inode->i_blkbits, 0);
115         }
116         head = page_buffers(page);
117         page_bh = head;
118         do {
119                 if (block == page_block) {
120                         page_bh->b_state = bh->b_state;
121                         page_bh->b_bdev = bh->b_bdev;
122                         page_bh->b_blocknr = bh->b_blocknr;
123                         break;
124                 }
125                 page_bh = page_bh->b_this_page;
126                 block++;
127         } while (page_bh != head);
128 }
129
130 /*
131  * This is the worker routine which does all the work of mapping the disk
132  * blocks and constructs largest possible bios, submits them for IO if the
133  * blocks are not contiguous on the disk.
134  *
135  * We pass a buffer_head back and forth and use its buffer_mapped() flag to
136  * represent the validity of its disk mapping and to decide when to do the next
137  * get_block() call.
138  */
139 static struct bio *
140 do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
141                 sector_t *last_block_in_bio, struct buffer_head *map_bh,
142                 unsigned long *first_logical_block, get_block_t get_block,
143                 gfp_t gfp)
144 {
145         struct inode *inode = page->mapping->host;
146         const unsigned blkbits = inode->i_blkbits;
147         const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits;
148         const unsigned blocksize = 1 << blkbits;
149         sector_t block_in_file;
150         sector_t last_block;
151         sector_t last_block_in_file;
152         sector_t blocks[MAX_BUF_PER_PAGE];
153         unsigned page_block;
154         unsigned first_hole = blocks_per_page;
155         struct block_device *bdev = NULL;
156         int length;
157         int fully_mapped = 1;
158         unsigned nblocks;
159         unsigned relative_block;
160
161         if (page_has_buffers(page))
162                 goto confused;
163
164         block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
165         last_block = block_in_file + nr_pages * blocks_per_page;
166         last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits;
167         if (last_block > last_block_in_file)
168                 last_block = last_block_in_file;
169         page_block = 0;
170
171         /*
172          * Map blocks using the result from the previous get_blocks call first.
173          */
174         nblocks = map_bh->b_size >> blkbits;
175         if (buffer_mapped(map_bh) && block_in_file > *first_logical_block &&
176                         block_in_file < (*first_logical_block + nblocks)) {
177                 unsigned map_offset = block_in_file - *first_logical_block;
178                 unsigned last = nblocks - map_offset;
179
180                 for (relative_block = 0; ; relative_block++) {
181                         if (relative_block == last) {
182                                 clear_buffer_mapped(map_bh);
183                                 break;
184                         }
185                         if (page_block == blocks_per_page)
186                                 break;
187                         blocks[page_block] = map_bh->b_blocknr + map_offset +
188                                                 relative_block;
189                         page_block++;
190                         block_in_file++;
191                 }
192                 bdev = map_bh->b_bdev;
193         }
194
195         /*
196          * Then do more get_blocks calls until we are done with this page.
197          */
198         map_bh->b_page = page;
199         while (page_block < blocks_per_page) {
200                 map_bh->b_state = 0;
201                 map_bh->b_size = 0;
202
203                 if (block_in_file < last_block) {
204                         map_bh->b_size = (last_block-block_in_file) << blkbits;
205                         if (get_block(inode, block_in_file, map_bh, 0))
206                                 goto confused;
207                         *first_logical_block = block_in_file;
208                 }
209
210                 if (!buffer_mapped(map_bh)) {
211                         fully_mapped = 0;
212                         if (first_hole == blocks_per_page)
213                                 first_hole = page_block;
214                         page_block++;
215                         block_in_file++;
216                         continue;
217                 }
218
219                 /* some filesystems will copy data into the page during
220                  * the get_block call, in which case we don't want to
221                  * read it again.  map_buffer_to_page copies the data
222                  * we just collected from get_block into the page's buffers
223                  * so readpage doesn't have to repeat the get_block call
224                  */
225                 if (buffer_uptodate(map_bh)) {
226                         map_buffer_to_page(page, map_bh, page_block);
227                         goto confused;
228                 }
229         
230                 if (first_hole != blocks_per_page)
231                         goto confused;          /* hole -> non-hole */
232
233                 /* Contiguous blocks? */
234                 if (page_block && blocks[page_block-1] != map_bh->b_blocknr-1)
235                         goto confused;
236                 nblocks = map_bh->b_size >> blkbits;
237                 for (relative_block = 0; ; relative_block++) {
238                         if (relative_block == nblocks) {
239                                 clear_buffer_mapped(map_bh);
240                                 break;
241                         } else if (page_block == blocks_per_page)
242                                 break;
243                         blocks[page_block] = map_bh->b_blocknr+relative_block;
244                         page_block++;
245                         block_in_file++;
246                 }
247                 bdev = map_bh->b_bdev;
248         }
249
250         if (first_hole != blocks_per_page) {
251                 zero_user_segment(page, first_hole << blkbits, PAGE_CACHE_SIZE);
252                 if (first_hole == 0) {
253                         SetPageUptodate(page);
254                         unlock_page(page);
255                         goto out;
256                 }
257         } else if (fully_mapped) {
258                 SetPageMappedToDisk(page);
259         }
260
261         if (fully_mapped && blocks_per_page == 1 && !PageUptodate(page) &&
262             cleancache_get_page(page) == 0) {
263                 SetPageUptodate(page);
264                 goto confused;
265         }
266
267         /*
268          * This page will go to BIO.  Do we need to send this BIO off first?
269          */
270         if (bio && (*last_block_in_bio != blocks[0] - 1))
271                 bio = mpage_bio_submit(READ, bio);
272
273 alloc_new:
274         if (bio == NULL) {
275                 if (first_hole == blocks_per_page) {
276                         if (!bdev_read_page(bdev, blocks[0] << (blkbits - 9),
277                                                                 page))
278                                 goto out;
279                 }
280                 bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
281                                 min_t(int, nr_pages, BIO_MAX_PAGES), gfp);
282                 if (bio == NULL)
283                         goto confused;
284         }
285
286         length = first_hole << blkbits;
287         if (bio_add_page(bio, page, length, 0) < length) {
288                 bio = mpage_bio_submit(READ, bio);
289                 goto alloc_new;
290         }
291
292         relative_block = block_in_file - *first_logical_block;
293         nblocks = map_bh->b_size >> blkbits;
294         if ((buffer_boundary(map_bh) && relative_block == nblocks) ||
295             (first_hole != blocks_per_page))
296                 bio = mpage_bio_submit(READ, bio);
297         else
298                 *last_block_in_bio = blocks[blocks_per_page - 1];
299 out:
300         return bio;
301
302 confused:
303         if (bio)
304                 bio = mpage_bio_submit(READ, bio);
305         if (!PageUptodate(page))
306                 block_read_full_page(page, get_block);
307         else
308                 unlock_page(page);
309         goto out;
310 }
311
312 /**
313  * mpage_readpages - populate an address space with some pages & start reads against them
314  * @mapping: the address_space
315  * @pages: The address of a list_head which contains the target pages.  These
316  *   pages have their ->index populated and are otherwise uninitialised.
317  *   The page at @pages->prev has the lowest file offset, and reads should be
318  *   issued in @pages->prev to @pages->next order.
319  * @nr_pages: The number of pages at *@pages
320  * @get_block: The filesystem's block mapper function.
321  *
322  * This function walks the pages and the blocks within each page, building and
323  * emitting large BIOs.
324  *
325  * If anything unusual happens, such as:
326  *
327  * - encountering a page which has buffers
328  * - encountering a page which has a non-hole after a hole
329  * - encountering a page with non-contiguous blocks
330  *
331  * then this code just gives up and calls the buffer_head-based read function.
332  * It does handle a page which has holes at the end - that is a common case:
333  * the end-of-file on blocksize < PAGE_CACHE_SIZE setups.
334  *
335  * BH_Boundary explanation:
336  *
337  * There is a problem.  The mpage read code assembles several pages, gets all
338  * their disk mappings, and then submits them all.  That's fine, but obtaining
339  * the disk mappings may require I/O.  Reads of indirect blocks, for example.
340  *
341  * So an mpage read of the first 16 blocks of an ext2 file will cause I/O to be
342  * submitted in the following order:
343  *      12 0 1 2 3 4 5 6 7 8 9 10 11 13 14 15 16
344  *
345  * because the indirect block has to be read to get the mappings of blocks
346  * 13,14,15,16.  Obviously, this impacts performance.
347  *
348  * So what we do it to allow the filesystem's get_block() function to set
349  * BH_Boundary when it maps block 11.  BH_Boundary says: mapping of the block
350  * after this one will require I/O against a block which is probably close to
351  * this one.  So you should push what I/O you have currently accumulated.
352  *
353  * This all causes the disk requests to be issued in the correct order.
354  */
355 int
356 mpage_readpages(struct address_space *mapping, struct list_head *pages,
357                                 unsigned nr_pages, get_block_t get_block)
358 {
359         struct bio *bio = NULL;
360         unsigned page_idx;
361         sector_t last_block_in_bio = 0;
362         struct buffer_head map_bh;
363         unsigned long first_logical_block = 0;
364         gfp_t gfp = mapping_gfp_constraint(mapping, GFP_KERNEL);
365
366         map_bh.b_state = 0;
367         map_bh.b_size = 0;
368         for (page_idx = 0; page_idx < nr_pages; page_idx++) {
369                 struct page *page = list_entry(pages->prev, struct page, lru);
370
371                 prefetchw(&page->flags);
372                 list_del(&page->lru);
373                 if (!add_to_page_cache_lru(page, mapping,
374                                         page->index,
375                                         gfp)) {
376                         bio = do_mpage_readpage(bio, page,
377                                         nr_pages - page_idx,
378                                         &last_block_in_bio, &map_bh,
379                                         &first_logical_block,
380                                         get_block, gfp);
381                 }
382                 page_cache_release(page);
383         }
384         BUG_ON(!list_empty(pages));
385         if (bio)
386                 mpage_bio_submit(READ, bio);
387         return 0;
388 }
389 EXPORT_SYMBOL(mpage_readpages);
390
391 /*
392  * This isn't called much at all
393  */
394 int mpage_readpage(struct page *page, get_block_t get_block)
395 {
396         struct bio *bio = NULL;
397         sector_t last_block_in_bio = 0;
398         struct buffer_head map_bh;
399         unsigned long first_logical_block = 0;
400         gfp_t gfp = mapping_gfp_constraint(page->mapping, GFP_KERNEL);
401
402         map_bh.b_state = 0;
403         map_bh.b_size = 0;
404         bio = do_mpage_readpage(bio, page, 1, &last_block_in_bio,
405                         &map_bh, &first_logical_block, get_block, gfp);
406         if (bio)
407                 mpage_bio_submit(READ, bio);
408         return 0;
409 }
410 EXPORT_SYMBOL(mpage_readpage);
411
412 /*
413  * Writing is not so simple.
414  *
415  * If the page has buffers then they will be used for obtaining the disk
416  * mapping.  We only support pages which are fully mapped-and-dirty, with a
417  * special case for pages which are unmapped at the end: end-of-file.
418  *
419  * If the page has no buffers (preferred) then the page is mapped here.
420  *
421  * If all blocks are found to be contiguous then the page can go into the
422  * BIO.  Otherwise fall back to the mapping's writepage().
423  * 
424  * FIXME: This code wants an estimate of how many pages are still to be
425  * written, so it can intelligently allocate a suitably-sized BIO.  For now,
426  * just allocate full-size (16-page) BIOs.
427  */
428
429 struct mpage_data {
430         struct bio *bio;
431         sector_t last_block_in_bio;
432         get_block_t *get_block;
433         unsigned use_writepage;
434 };
435
436 /*
437  * We have our BIO, so we can now mark the buffers clean.  Make
438  * sure to only clean buffers which we know we'll be writing.
439  */
440 static void clean_buffers(struct page *page, unsigned first_unmapped)
441 {
442         unsigned buffer_counter = 0;
443         struct buffer_head *bh, *head;
444         if (!page_has_buffers(page))
445                 return;
446         head = page_buffers(page);
447         bh = head;
448
449         do {
450                 if (buffer_counter++ == first_unmapped)
451                         break;
452                 clear_buffer_dirty(bh);
453                 bh = bh->b_this_page;
454         } while (bh != head);
455
456         /*
457          * we cannot drop the bh if the page is not uptodate or a concurrent
458          * readpage would fail to serialize with the bh and it would read from
459          * disk before we reach the platter.
460          */
461         if (buffer_heads_over_limit && PageUptodate(page))
462                 try_to_free_buffers(page);
463 }
464
465 static int __mpage_writepage(struct page *page, struct writeback_control *wbc,
466                       void *data)
467 {
468         struct mpage_data *mpd = data;
469         struct bio *bio = mpd->bio;
470         struct address_space *mapping = page->mapping;
471         struct inode *inode = page->mapping->host;
472         const unsigned blkbits = inode->i_blkbits;
473         unsigned long end_index;
474         const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits;
475         sector_t last_block;
476         sector_t block_in_file;
477         sector_t blocks[MAX_BUF_PER_PAGE];
478         unsigned page_block;
479         unsigned first_unmapped = blocks_per_page;
480         struct block_device *bdev = NULL;
481         int boundary = 0;
482         sector_t boundary_block = 0;
483         struct block_device *boundary_bdev = NULL;
484         int length;
485         struct buffer_head map_bh;
486         loff_t i_size = i_size_read(inode);
487         int ret = 0;
488         int wr = (wbc->sync_mode == WB_SYNC_ALL ?  WRITE_SYNC : WRITE);
489
490         if (page_has_buffers(page)) {
491                 struct buffer_head *head = page_buffers(page);
492                 struct buffer_head *bh = head;
493
494                 /* If they're all mapped and dirty, do it */
495                 page_block = 0;
496                 do {
497                         BUG_ON(buffer_locked(bh));
498                         if (!buffer_mapped(bh)) {
499                                 /*
500                                  * unmapped dirty buffers are created by
501                                  * __set_page_dirty_buffers -> mmapped data
502                                  */
503                                 if (buffer_dirty(bh))
504                                         goto confused;
505                                 if (first_unmapped == blocks_per_page)
506                                         first_unmapped = page_block;
507                                 continue;
508                         }
509
510                         if (first_unmapped != blocks_per_page)
511                                 goto confused;  /* hole -> non-hole */
512
513                         if (!buffer_dirty(bh) || !buffer_uptodate(bh))
514                                 goto confused;
515                         if (page_block) {
516                                 if (bh->b_blocknr != blocks[page_block-1] + 1)
517                                         goto confused;
518                         }
519                         blocks[page_block++] = bh->b_blocknr;
520                         boundary = buffer_boundary(bh);
521                         if (boundary) {
522                                 boundary_block = bh->b_blocknr;
523                                 boundary_bdev = bh->b_bdev;
524                         }
525                         bdev = bh->b_bdev;
526                 } while ((bh = bh->b_this_page) != head);
527
528                 if (first_unmapped)
529                         goto page_is_mapped;
530
531                 /*
532                  * Page has buffers, but they are all unmapped. The page was
533                  * created by pagein or read over a hole which was handled by
534                  * block_read_full_page().  If this address_space is also
535                  * using mpage_readpages then this can rarely happen.
536                  */
537                 goto confused;
538         }
539
540         /*
541          * The page has no buffers: map it to disk
542          */
543         BUG_ON(!PageUptodate(page));
544         block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
545         last_block = (i_size - 1) >> blkbits;
546         map_bh.b_page = page;
547         for (page_block = 0; page_block < blocks_per_page; ) {
548
549                 map_bh.b_state = 0;
550                 map_bh.b_size = 1 << blkbits;
551                 if (mpd->get_block(inode, block_in_file, &map_bh, 1))
552                         goto confused;
553                 if (buffer_new(&map_bh))
554                         unmap_underlying_metadata(map_bh.b_bdev,
555                                                 map_bh.b_blocknr);
556                 if (buffer_boundary(&map_bh)) {
557                         boundary_block = map_bh.b_blocknr;
558                         boundary_bdev = map_bh.b_bdev;
559                 }
560                 if (page_block) {
561                         if (map_bh.b_blocknr != blocks[page_block-1] + 1)
562                                 goto confused;
563                 }
564                 blocks[page_block++] = map_bh.b_blocknr;
565                 boundary = buffer_boundary(&map_bh);
566                 bdev = map_bh.b_bdev;
567                 if (block_in_file == last_block)
568                         break;
569                 block_in_file++;
570         }
571         BUG_ON(page_block == 0);
572
573         first_unmapped = page_block;
574
575 page_is_mapped:
576         end_index = i_size >> PAGE_CACHE_SHIFT;
577         if (page->index >= end_index) {
578                 /*
579                  * The page straddles i_size.  It must be zeroed out on each
580                  * and every writepage invocation because it may be mmapped.
581                  * "A file is mapped in multiples of the page size.  For a file
582                  * that is not a multiple of the page size, the remaining memory
583                  * is zeroed when mapped, and writes to that region are not
584                  * written out to the file."
585                  */
586                 unsigned offset = i_size & (PAGE_CACHE_SIZE - 1);
587
588                 if (page->index > end_index || !offset)
589                         goto confused;
590                 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
591         }
592
593         /*
594          * This page will go to BIO.  Do we need to send this BIO off first?
595          */
596         if (bio && mpd->last_block_in_bio != blocks[0] - 1)
597                 bio = mpage_bio_submit(wr, bio);
598
599 alloc_new:
600         if (bio == NULL) {
601                 if (first_unmapped == blocks_per_page) {
602                         if (!bdev_write_page(bdev, blocks[0] << (blkbits - 9),
603                                                                 page, wbc)) {
604                                 clean_buffers(page, first_unmapped);
605                                 goto out;
606                         }
607                 }
608                 bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
609                                 BIO_MAX_PAGES, GFP_NOFS|__GFP_HIGH);
610                 if (bio == NULL)
611                         goto confused;
612
613                 wbc_init_bio(wbc, bio);
614         }
615
616         /*
617          * Must try to add the page before marking the buffer clean or
618          * the confused fail path above (OOM) will be very confused when
619          * it finds all bh marked clean (i.e. it will not write anything)
620          */
621         wbc_account_io(wbc, page, PAGE_SIZE);
622         length = first_unmapped << blkbits;
623         if (bio_add_page(bio, page, length, 0) < length) {
624                 bio = mpage_bio_submit(wr, bio);
625                 goto alloc_new;
626         }
627
628         clean_buffers(page, first_unmapped);
629
630         BUG_ON(PageWriteback(page));
631         set_page_writeback(page);
632         unlock_page(page);
633         if (boundary || (first_unmapped != blocks_per_page)) {
634                 bio = mpage_bio_submit(wr, bio);
635                 if (boundary_block) {
636                         write_boundary_block(boundary_bdev,
637                                         boundary_block, 1 << blkbits);
638                 }
639         } else {
640                 mpd->last_block_in_bio = blocks[blocks_per_page - 1];
641         }
642         goto out;
643
644 confused:
645         if (bio)
646                 bio = mpage_bio_submit(wr, bio);
647
648         if (mpd->use_writepage) {
649                 ret = mapping->a_ops->writepage(page, wbc);
650         } else {
651                 ret = -EAGAIN;
652                 goto out;
653         }
654         /*
655          * The caller has a ref on the inode, so *mapping is stable
656          */
657         mapping_set_error(mapping, ret);
658 out:
659         mpd->bio = bio;
660         return ret;
661 }
662
663 /**
664  * mpage_writepages - walk the list of dirty pages of the given address space & writepage() all of them
665  * @mapping: address space structure to write
666  * @wbc: subtract the number of written pages from *@wbc->nr_to_write
667  * @get_block: the filesystem's block mapper function.
668  *             If this is NULL then use a_ops->writepage.  Otherwise, go
669  *             direct-to-BIO.
670  *
671  * This is a library function, which implements the writepages()
672  * address_space_operation.
673  *
674  * If a page is already under I/O, generic_writepages() skips it, even
675  * if it's dirty.  This is desirable behaviour for memory-cleaning writeback,
676  * but it is INCORRECT for data-integrity system calls such as fsync().  fsync()
677  * and msync() need to guarantee that all the data which was dirty at the time
678  * the call was made get new I/O started against them.  If wbc->sync_mode is
679  * WB_SYNC_ALL then we were called for data integrity and we must wait for
680  * existing IO to complete.
681  */
682 int
683 mpage_writepages(struct address_space *mapping,
684                 struct writeback_control *wbc, get_block_t get_block)
685 {
686         struct blk_plug plug;
687         int ret;
688
689         blk_start_plug(&plug);
690
691         if (!get_block)
692                 ret = generic_writepages(mapping, wbc);
693         else {
694                 struct mpage_data mpd = {
695                         .bio = NULL,
696                         .last_block_in_bio = 0,
697                         .get_block = get_block,
698                         .use_writepage = 1,
699                 };
700
701                 ret = write_cache_pages(mapping, wbc, __mpage_writepage, &mpd);
702                 if (mpd.bio) {
703                         int wr = (wbc->sync_mode == WB_SYNC_ALL ?
704                                   WRITE_SYNC : WRITE);
705                         mpage_bio_submit(wr, mpd.bio);
706                 }
707         }
708         blk_finish_plug(&plug);
709         return ret;
710 }
711 EXPORT_SYMBOL(mpage_writepages);
712
713 int mpage_writepage(struct page *page, get_block_t get_block,
714         struct writeback_control *wbc)
715 {
716         struct mpage_data mpd = {
717                 .bio = NULL,
718                 .last_block_in_bio = 0,
719                 .get_block = get_block,
720                 .use_writepage = 0,
721         };
722         int ret = __mpage_writepage(page, wbc, &mpd);
723         if (mpd.bio) {
724                 int wr = (wbc->sync_mode == WB_SYNC_ALL ?
725                           WRITE_SYNC : WRITE);
726                 mpage_bio_submit(wr, mpd.bio);
727         }
728         return ret;
729 }
730 EXPORT_SYMBOL(mpage_writepage);