ia64/linux-2.6.18-xen.hg

view fs/mpage.c @ 524:7f8b544237bf

netfront: Allow netfront in domain 0.

This is useful if your physical network device is in a utility domain.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
author Keir Fraser <keir.fraser@citrix.com>
date Tue Apr 15 15:18:58 2008 +0100 (2008-04-15)
parents 831230e53067
children cad6f60f0506
line source
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 akpm@zip.com.au
10 * Initial version
11 * 27Jun2002 axboe@suse.de
12 * use bio_add_page() to build bio's just the right size
13 */
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>
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 int mpage_end_io_read(struct bio *bio, unsigned int bytes_done, 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;
47 if (bio->bi_size)
48 return 1;
50 do {
51 struct page *page = bvec->bv_page;
53 if (--bvec >= bio->bi_io_vec)
54 prefetchw(&bvec->bv_page->flags);
56 if (uptodate) {
57 SetPageUptodate(page);
58 } else {
59 ClearPageUptodate(page);
60 SetPageError(page);
61 }
62 unlock_page(page);
63 } while (bvec >= bio->bi_io_vec);
64 bio_put(bio);
65 return 0;
66 }
68 static int mpage_end_io_write(struct bio *bio, unsigned int bytes_done, int err)
69 {
70 const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
71 struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
73 if (bio->bi_size)
74 return 1;
76 do {
77 struct page *page = bvec->bv_page;
79 if (--bvec >= bio->bi_io_vec)
80 prefetchw(&bvec->bv_page->flags);
82 if (!uptodate){
83 SetPageError(page);
84 if (page->mapping)
85 set_bit(AS_EIO, &page->mapping->flags);
86 }
87 end_page_writeback(page);
88 } while (bvec >= bio->bi_io_vec);
89 bio_put(bio);
90 return 0;
91 }
93 static struct bio *mpage_bio_submit(int rw, struct bio *bio)
94 {
95 bio->bi_end_io = mpage_end_io_read;
96 if (rw == WRITE)
97 bio->bi_end_io = mpage_end_io_write;
98 submit_bio(rw, bio);
99 return NULL;
100 }
102 static struct bio *
103 mpage_alloc(struct block_device *bdev,
104 sector_t first_sector, int nr_vecs,
105 gfp_t gfp_flags)
106 {
107 struct bio *bio;
109 bio = bio_alloc(gfp_flags, nr_vecs);
111 if (bio == NULL && (current->flags & PF_MEMALLOC)) {
112 while (!bio && (nr_vecs /= 2))
113 bio = bio_alloc(gfp_flags, nr_vecs);
114 }
116 if (bio) {
117 bio->bi_bdev = bdev;
118 bio->bi_sector = first_sector;
119 }
120 return bio;
121 }
123 /*
124 * support function for mpage_readpages. The fs supplied get_block might
125 * return an up to date buffer. This is used to map that buffer into
126 * the page, which allows readpage to avoid triggering a duplicate call
127 * to get_block.
128 *
129 * The idea is to avoid adding buffers to pages that don't already have
130 * them. So when the buffer is up to date and the page size == block size,
131 * this marks the page up to date instead of adding new buffers.
132 */
133 static void
134 map_buffer_to_page(struct page *page, struct buffer_head *bh, int page_block)
135 {
136 struct inode *inode = page->mapping->host;
137 struct buffer_head *page_bh, *head;
138 int block = 0;
140 if (!page_has_buffers(page)) {
141 /*
142 * don't make any buffers if there is only one buffer on
143 * the page and the page just needs to be set up to date
144 */
145 if (inode->i_blkbits == PAGE_CACHE_SHIFT &&
146 buffer_uptodate(bh)) {
147 SetPageUptodate(page);
148 return;
149 }
150 create_empty_buffers(page, 1 << inode->i_blkbits, 0);
151 }
152 head = page_buffers(page);
153 page_bh = head;
154 do {
155 if (block == page_block) {
156 page_bh->b_state = bh->b_state;
157 page_bh->b_bdev = bh->b_bdev;
158 page_bh->b_blocknr = bh->b_blocknr;
159 break;
160 }
161 page_bh = page_bh->b_this_page;
162 block++;
163 } while (page_bh != head);
164 }
166 /*
167 * This is the worker routine which does all the work of mapping the disk
168 * blocks and constructs largest possible bios, submits them for IO if the
169 * blocks are not contiguous on the disk.
170 *
171 * We pass a buffer_head back and forth and use its buffer_mapped() flag to
172 * represent the validity of its disk mapping and to decide when to do the next
173 * get_block() call.
174 */
175 static struct bio *
176 do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
177 sector_t *last_block_in_bio, struct buffer_head *map_bh,
178 unsigned long *first_logical_block, get_block_t get_block)
179 {
180 struct inode *inode = page->mapping->host;
181 const unsigned blkbits = inode->i_blkbits;
182 const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits;
183 const unsigned blocksize = 1 << blkbits;
184 sector_t block_in_file;
185 sector_t last_block;
186 sector_t last_block_in_file;
187 sector_t blocks[MAX_BUF_PER_PAGE];
188 unsigned page_block;
189 unsigned first_hole = blocks_per_page;
190 struct block_device *bdev = NULL;
191 int length;
192 int fully_mapped = 1;
193 unsigned nblocks;
194 unsigned relative_block;
196 if (page_has_buffers(page))
197 goto confused;
199 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
200 last_block = block_in_file + nr_pages * blocks_per_page;
201 last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits;
202 if (last_block > last_block_in_file)
203 last_block = last_block_in_file;
204 page_block = 0;
206 /*
207 * Map blocks using the result from the previous get_blocks call first.
208 */
209 nblocks = map_bh->b_size >> blkbits;
210 if (buffer_mapped(map_bh) && block_in_file > *first_logical_block &&
211 block_in_file < (*first_logical_block + nblocks)) {
212 unsigned map_offset = block_in_file - *first_logical_block;
213 unsigned last = nblocks - map_offset;
215 for (relative_block = 0; ; relative_block++) {
216 if (relative_block == last) {
217 clear_buffer_mapped(map_bh);
218 break;
219 }
220 if (page_block == blocks_per_page)
221 break;
222 blocks[page_block] = map_bh->b_blocknr + map_offset +
223 relative_block;
224 page_block++;
225 block_in_file++;
226 }
227 bdev = map_bh->b_bdev;
228 }
230 /*
231 * Then do more get_blocks calls until we are done with this page.
232 */
233 map_bh->b_page = page;
234 while (page_block < blocks_per_page) {
235 map_bh->b_state = 0;
236 map_bh->b_size = 0;
238 if (block_in_file < last_block) {
239 map_bh->b_size = (last_block-block_in_file) << blkbits;
240 if (get_block(inode, block_in_file, map_bh, 0))
241 goto confused;
242 *first_logical_block = block_in_file;
243 }
245 if (!buffer_mapped(map_bh)) {
246 fully_mapped = 0;
247 if (first_hole == blocks_per_page)
248 first_hole = page_block;
249 page_block++;
250 block_in_file++;
251 clear_buffer_mapped(map_bh);
252 continue;
253 }
255 /* some filesystems will copy data into the page during
256 * the get_block call, in which case we don't want to
257 * read it again. map_buffer_to_page copies the data
258 * we just collected from get_block into the page's buffers
259 * so readpage doesn't have to repeat the get_block call
260 */
261 if (buffer_uptodate(map_bh)) {
262 map_buffer_to_page(page, map_bh, page_block);
263 goto confused;
264 }
266 if (first_hole != blocks_per_page)
267 goto confused; /* hole -> non-hole */
269 /* Contiguous blocks? */
270 if (page_block && blocks[page_block-1] != map_bh->b_blocknr-1)
271 goto confused;
272 nblocks = map_bh->b_size >> blkbits;
273 for (relative_block = 0; ; relative_block++) {
274 if (relative_block == nblocks) {
275 clear_buffer_mapped(map_bh);
276 break;
277 } else if (page_block == blocks_per_page)
278 break;
279 blocks[page_block] = map_bh->b_blocknr+relative_block;
280 page_block++;
281 block_in_file++;
282 }
283 bdev = map_bh->b_bdev;
284 }
286 if (first_hole != blocks_per_page) {
287 char *kaddr = kmap_atomic(page, KM_USER0);
288 memset(kaddr + (first_hole << blkbits), 0,
289 PAGE_CACHE_SIZE - (first_hole << blkbits));
290 flush_dcache_page(page);
291 kunmap_atomic(kaddr, KM_USER0);
292 if (first_hole == 0) {
293 SetPageUptodate(page);
294 unlock_page(page);
295 goto out;
296 }
297 } else if (fully_mapped) {
298 SetPageMappedToDisk(page);
299 }
301 /*
302 * This page will go to BIO. Do we need to send this BIO off first?
303 */
304 if (bio && (*last_block_in_bio != blocks[0] - 1))
305 bio = mpage_bio_submit(READ, bio);
307 alloc_new:
308 if (bio == NULL) {
309 bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
310 min_t(int, nr_pages, bio_get_nr_vecs(bdev)),
311 GFP_KERNEL);
312 if (bio == NULL)
313 goto confused;
314 }
316 length = first_hole << blkbits;
317 if (bio_add_page(bio, page, length, 0) < length) {
318 bio = mpage_bio_submit(READ, bio);
319 goto alloc_new;
320 }
322 if (buffer_boundary(map_bh) || (first_hole != blocks_per_page))
323 bio = mpage_bio_submit(READ, bio);
324 else
325 *last_block_in_bio = blocks[blocks_per_page - 1];
326 out:
327 return bio;
329 confused:
330 if (bio)
331 bio = mpage_bio_submit(READ, bio);
332 if (!PageUptodate(page))
333 block_read_full_page(page, get_block);
334 else
335 unlock_page(page);
336 goto out;
337 }
339 /**
340 * mpage_readpages - populate an address space with some pages, and
341 * start reads against them.
342 *
343 * @mapping: the address_space
344 * @pages: The address of a list_head which contains the target pages. These
345 * pages have their ->index populated and are otherwise uninitialised.
346 *
347 * The page at @pages->prev has the lowest file offset, and reads should be
348 * issued in @pages->prev to @pages->next order.
349 *
350 * @nr_pages: The number of pages at *@pages
351 * @get_block: The filesystem's block mapper function.
352 *
353 * This function walks the pages and the blocks within each page, building and
354 * emitting large BIOs.
355 *
356 * If anything unusual happens, such as:
357 *
358 * - encountering a page which has buffers
359 * - encountering a page which has a non-hole after a hole
360 * - encountering a page with non-contiguous blocks
361 *
362 * then this code just gives up and calls the buffer_head-based read function.
363 * It does handle a page which has holes at the end - that is a common case:
364 * the end-of-file on blocksize < PAGE_CACHE_SIZE setups.
365 *
366 * BH_Boundary explanation:
367 *
368 * There is a problem. The mpage read code assembles several pages, gets all
369 * their disk mappings, and then submits them all. That's fine, but obtaining
370 * the disk mappings may require I/O. Reads of indirect blocks, for example.
371 *
372 * So an mpage read of the first 16 blocks of an ext2 file will cause I/O to be
373 * submitted in the following order:
374 * 12 0 1 2 3 4 5 6 7 8 9 10 11 13 14 15 16
375 * because the indirect block has to be read to get the mappings of blocks
376 * 13,14,15,16. Obviously, this impacts performance.
377 *
378 * So what we do it to allow the filesystem's get_block() function to set
379 * BH_Boundary when it maps block 11. BH_Boundary says: mapping of the block
380 * after this one will require I/O against a block which is probably close to
381 * this one. So you should push what I/O you have currently accumulated.
382 *
383 * This all causes the disk requests to be issued in the correct order.
384 */
385 int
386 mpage_readpages(struct address_space *mapping, struct list_head *pages,
387 unsigned nr_pages, get_block_t get_block)
388 {
389 struct bio *bio = NULL;
390 unsigned page_idx;
391 sector_t last_block_in_bio = 0;
392 struct pagevec lru_pvec;
393 struct buffer_head map_bh;
394 unsigned long first_logical_block = 0;
396 clear_buffer_mapped(&map_bh);
397 pagevec_init(&lru_pvec, 0);
398 for (page_idx = 0; page_idx < nr_pages; page_idx++) {
399 struct page *page = list_entry(pages->prev, struct page, lru);
401 prefetchw(&page->flags);
402 list_del(&page->lru);
403 if (!add_to_page_cache(page, mapping,
404 page->index, GFP_KERNEL)) {
405 bio = do_mpage_readpage(bio, page,
406 nr_pages - page_idx,
407 &last_block_in_bio, &map_bh,
408 &first_logical_block,
409 get_block);
410 if (!pagevec_add(&lru_pvec, page))
411 __pagevec_lru_add(&lru_pvec);
412 } else {
413 page_cache_release(page);
414 }
415 }
416 pagevec_lru_add(&lru_pvec);
417 BUG_ON(!list_empty(pages));
418 if (bio)
419 mpage_bio_submit(READ, bio);
420 return 0;
421 }
422 EXPORT_SYMBOL(mpage_readpages);
424 /*
425 * This isn't called much at all
426 */
427 int mpage_readpage(struct page *page, get_block_t get_block)
428 {
429 struct bio *bio = NULL;
430 sector_t last_block_in_bio = 0;
431 struct buffer_head map_bh;
432 unsigned long first_logical_block = 0;
434 clear_buffer_mapped(&map_bh);
435 bio = do_mpage_readpage(bio, page, 1, &last_block_in_bio,
436 &map_bh, &first_logical_block, get_block);
437 if (bio)
438 mpage_bio_submit(READ, bio);
439 return 0;
440 }
441 EXPORT_SYMBOL(mpage_readpage);
443 /*
444 * Writing is not so simple.
445 *
446 * If the page has buffers then they will be used for obtaining the disk
447 * mapping. We only support pages which are fully mapped-and-dirty, with a
448 * special case for pages which are unmapped at the end: end-of-file.
449 *
450 * If the page has no buffers (preferred) then the page is mapped here.
451 *
452 * If all blocks are found to be contiguous then the page can go into the
453 * BIO. Otherwise fall back to the mapping's writepage().
454 *
455 * FIXME: This code wants an estimate of how many pages are still to be
456 * written, so it can intelligently allocate a suitably-sized BIO. For now,
457 * just allocate full-size (16-page) BIOs.
458 */
459 static struct bio *
460 __mpage_writepage(struct bio *bio, struct page *page, get_block_t get_block,
461 sector_t *last_block_in_bio, int *ret, struct writeback_control *wbc,
462 writepage_t writepage_fn)
463 {
464 struct address_space *mapping = page->mapping;
465 struct inode *inode = page->mapping->host;
466 const unsigned blkbits = inode->i_blkbits;
467 unsigned long end_index;
468 const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits;
469 sector_t last_block;
470 sector_t block_in_file;
471 sector_t blocks[MAX_BUF_PER_PAGE];
472 unsigned page_block;
473 unsigned first_unmapped = blocks_per_page;
474 struct block_device *bdev = NULL;
475 int boundary = 0;
476 sector_t boundary_block = 0;
477 struct block_device *boundary_bdev = NULL;
478 int length;
479 struct buffer_head map_bh;
480 loff_t i_size = i_size_read(inode);
482 if (page_has_buffers(page)) {
483 struct buffer_head *head = page_buffers(page);
484 struct buffer_head *bh = head;
486 /* If they're all mapped and dirty, do it */
487 page_block = 0;
488 do {
489 BUG_ON(buffer_locked(bh));
490 if (!buffer_mapped(bh)) {
491 /*
492 * unmapped dirty buffers are created by
493 * __set_page_dirty_buffers -> mmapped data
494 */
495 if (buffer_dirty(bh))
496 goto confused;
497 if (first_unmapped == blocks_per_page)
498 first_unmapped = page_block;
499 continue;
500 }
502 if (first_unmapped != blocks_per_page)
503 goto confused; /* hole -> non-hole */
505 if (!buffer_dirty(bh) || !buffer_uptodate(bh))
506 goto confused;
507 if (page_block) {
508 if (bh->b_blocknr != blocks[page_block-1] + 1)
509 goto confused;
510 }
511 blocks[page_block++] = bh->b_blocknr;
512 boundary = buffer_boundary(bh);
513 if (boundary) {
514 boundary_block = bh->b_blocknr;
515 boundary_bdev = bh->b_bdev;
516 }
517 bdev = bh->b_bdev;
518 } while ((bh = bh->b_this_page) != head);
520 if (first_unmapped)
521 goto page_is_mapped;
523 /*
524 * Page has buffers, but they are all unmapped. The page was
525 * created by pagein or read over a hole which was handled by
526 * block_read_full_page(). If this address_space is also
527 * using mpage_readpages then this can rarely happen.
528 */
529 goto confused;
530 }
532 /*
533 * The page has no buffers: map it to disk
534 */
535 BUG_ON(!PageUptodate(page));
536 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
537 last_block = (i_size - 1) >> blkbits;
538 map_bh.b_page = page;
539 for (page_block = 0; page_block < blocks_per_page; ) {
541 map_bh.b_state = 0;
542 map_bh.b_size = 1 << blkbits;
543 if (get_block(inode, block_in_file, &map_bh, 1))
544 goto confused;
545 if (buffer_new(&map_bh))
546 unmap_underlying_metadata(map_bh.b_bdev,
547 map_bh.b_blocknr);
548 if (buffer_boundary(&map_bh)) {
549 boundary_block = map_bh.b_blocknr;
550 boundary_bdev = map_bh.b_bdev;
551 }
552 if (page_block) {
553 if (map_bh.b_blocknr != blocks[page_block-1] + 1)
554 goto confused;
555 }
556 blocks[page_block++] = map_bh.b_blocknr;
557 boundary = buffer_boundary(&map_bh);
558 bdev = map_bh.b_bdev;
559 if (block_in_file == last_block)
560 break;
561 block_in_file++;
562 }
563 BUG_ON(page_block == 0);
565 first_unmapped = page_block;
567 page_is_mapped:
568 end_index = i_size >> PAGE_CACHE_SHIFT;
569 if (page->index >= end_index) {
570 /*
571 * The page straddles i_size. It must be zeroed out on each
572 * and every writepage invokation because it may be mmapped.
573 * "A file is mapped in multiples of the page size. For a file
574 * that is not a multiple of the page size, the remaining memory
575 * is zeroed when mapped, and writes to that region are not
576 * written out to the file."
577 */
578 unsigned offset = i_size & (PAGE_CACHE_SIZE - 1);
579 char *kaddr;
581 if (page->index > end_index || !offset)
582 goto confused;
583 kaddr = kmap_atomic(page, KM_USER0);
584 memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
585 flush_dcache_page(page);
586 kunmap_atomic(kaddr, KM_USER0);
587 }
589 /*
590 * This page will go to BIO. Do we need to send this BIO off first?
591 */
592 if (bio && *last_block_in_bio != blocks[0] - 1)
593 bio = mpage_bio_submit(WRITE, bio);
595 alloc_new:
596 if (bio == NULL) {
597 bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
598 bio_get_nr_vecs(bdev), GFP_NOFS|__GFP_HIGH);
599 if (bio == NULL)
600 goto confused;
601 }
603 /*
604 * Must try to add the page before marking the buffer clean or
605 * the confused fail path above (OOM) will be very confused when
606 * it finds all bh marked clean (i.e. it will not write anything)
607 */
608 length = first_unmapped << blkbits;
609 if (bio_add_page(bio, page, length, 0) < length) {
610 bio = mpage_bio_submit(WRITE, bio);
611 goto alloc_new;
612 }
614 /*
615 * OK, we have our BIO, so we can now mark the buffers clean. Make
616 * sure to only clean buffers which we know we'll be writing.
617 */
618 if (page_has_buffers(page)) {
619 struct buffer_head *head = page_buffers(page);
620 struct buffer_head *bh = head;
621 unsigned buffer_counter = 0;
623 do {
624 if (buffer_counter++ == first_unmapped)
625 break;
626 clear_buffer_dirty(bh);
627 bh = bh->b_this_page;
628 } while (bh != head);
630 /*
631 * we cannot drop the bh if the page is not uptodate
632 * or a concurrent readpage would fail to serialize with the bh
633 * and it would read from disk before we reach the platter.
634 */
635 if (buffer_heads_over_limit && PageUptodate(page))
636 try_to_free_buffers(page);
637 }
639 BUG_ON(PageWriteback(page));
640 set_page_writeback(page);
641 unlock_page(page);
642 if (boundary || (first_unmapped != blocks_per_page)) {
643 bio = mpage_bio_submit(WRITE, bio);
644 if (boundary_block) {
645 write_boundary_block(boundary_bdev,
646 boundary_block, 1 << blkbits);
647 }
648 } else {
649 *last_block_in_bio = blocks[blocks_per_page - 1];
650 }
651 goto out;
653 confused:
654 if (bio)
655 bio = mpage_bio_submit(WRITE, bio);
657 if (writepage_fn) {
658 *ret = (*writepage_fn)(page, wbc);
659 } else {
660 *ret = -EAGAIN;
661 goto out;
662 }
663 /*
664 * The caller has a ref on the inode, so *mapping is stable
665 */
666 if (*ret) {
667 if (*ret == -ENOSPC)
668 set_bit(AS_ENOSPC, &mapping->flags);
669 else
670 set_bit(AS_EIO, &mapping->flags);
671 }
672 out:
673 return bio;
674 }
676 /**
677 * mpage_writepages - walk the list of dirty pages of the given
678 * address space and writepage() all of them.
679 *
680 * @mapping: address space structure to write
681 * @wbc: subtract the number of written pages from *@wbc->nr_to_write
682 * @get_block: the filesystem's block mapper function.
683 * If this is NULL then use a_ops->writepage. Otherwise, go
684 * direct-to-BIO.
685 *
686 * This is a library function, which implements the writepages()
687 * address_space_operation.
688 *
689 * If a page is already under I/O, generic_writepages() skips it, even
690 * if it's dirty. This is desirable behaviour for memory-cleaning writeback,
691 * but it is INCORRECT for data-integrity system calls such as fsync(). fsync()
692 * and msync() need to guarantee that all the data which was dirty at the time
693 * the call was made get new I/O started against them. If wbc->sync_mode is
694 * WB_SYNC_ALL then we were called for data integrity and we must wait for
695 * existing IO to complete.
696 */
697 int
698 mpage_writepages(struct address_space *mapping,
699 struct writeback_control *wbc, get_block_t get_block)
700 {
701 struct backing_dev_info *bdi = mapping->backing_dev_info;
702 struct bio *bio = NULL;
703 sector_t last_block_in_bio = 0;
704 int ret = 0;
705 int done = 0;
706 int (*writepage)(struct page *page, struct writeback_control *wbc);
707 struct pagevec pvec;
708 int nr_pages;
709 pgoff_t index;
710 pgoff_t end; /* Inclusive */
711 int scanned = 0;
712 int range_whole = 0;
714 if (wbc->nonblocking && bdi_write_congested(bdi)) {
715 wbc->encountered_congestion = 1;
716 return 0;
717 }
719 writepage = NULL;
720 if (get_block == NULL)
721 writepage = mapping->a_ops->writepage;
723 pagevec_init(&pvec, 0);
724 if (wbc->range_cyclic) {
725 index = mapping->writeback_index; /* Start from prev offset */
726 end = -1;
727 } else {
728 index = wbc->range_start >> PAGE_CACHE_SHIFT;
729 end = wbc->range_end >> PAGE_CACHE_SHIFT;
730 if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
731 range_whole = 1;
732 scanned = 1;
733 }
734 retry:
735 while (!done && (index <= end) &&
736 (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
737 PAGECACHE_TAG_DIRTY,
738 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1))) {
739 unsigned i;
741 scanned = 1;
742 for (i = 0; i < nr_pages; i++) {
743 struct page *page = pvec.pages[i];
745 /*
746 * At this point we hold neither mapping->tree_lock nor
747 * lock on the page itself: the page may be truncated or
748 * invalidated (changing page->mapping to NULL), or even
749 * swizzled back from swapper_space to tmpfs file
750 * mapping
751 */
753 lock_page(page);
755 if (unlikely(page->mapping != mapping)) {
756 unlock_page(page);
757 continue;
758 }
760 if (!wbc->range_cyclic && page->index > end) {
761 done = 1;
762 unlock_page(page);
763 continue;
764 }
766 if (wbc->sync_mode != WB_SYNC_NONE)
767 wait_on_page_writeback(page);
769 if (PageWriteback(page) ||
770 !clear_page_dirty_for_io(page)) {
771 unlock_page(page);
772 continue;
773 }
775 if (writepage) {
776 ret = (*writepage)(page, wbc);
777 if (ret) {
778 if (ret == -ENOSPC)
779 set_bit(AS_ENOSPC,
780 &mapping->flags);
781 else
782 set_bit(AS_EIO,
783 &mapping->flags);
784 }
785 } else {
786 bio = __mpage_writepage(bio, page, get_block,
787 &last_block_in_bio, &ret, wbc,
788 page->mapping->a_ops->writepage);
789 }
790 if (unlikely(ret == AOP_WRITEPAGE_ACTIVATE))
791 unlock_page(page);
792 if (ret || (--(wbc->nr_to_write) <= 0))
793 done = 1;
794 if (wbc->nonblocking && bdi_write_congested(bdi)) {
795 wbc->encountered_congestion = 1;
796 done = 1;
797 }
798 }
799 pagevec_release(&pvec);
800 cond_resched();
801 }
802 if (!scanned && !done) {
803 /*
804 * We hit the last page and there is more work to be done: wrap
805 * back to the start of the file
806 */
807 scanned = 1;
808 index = 0;
809 goto retry;
810 }
811 if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
812 mapping->writeback_index = index;
813 if (bio)
814 mpage_bio_submit(WRITE, bio);
815 return ret;
816 }
817 EXPORT_SYMBOL(mpage_writepages);
819 int mpage_writepage(struct page *page, get_block_t get_block,
820 struct writeback_control *wbc)
821 {
822 int ret = 0;
823 struct bio *bio;
824 sector_t last_block_in_bio = 0;
826 bio = __mpage_writepage(NULL, page, get_block,
827 &last_block_in_bio, &ret, wbc, NULL);
828 if (bio)
829 mpage_bio_submit(WRITE, bio);
831 return ret;
832 }
833 EXPORT_SYMBOL(mpage_writepage);