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1 | /* |
2 | * fs/mpage.c |
3 | * |
4 | * Copyright (C) 2002, Linus Torvalds. |
5 | * |
6 | * Contains functions related to preparing and submitting BIOs which contain |
7 | * multiple pagecache pages. |
8 | * |
9 | * 15May2002 Andrew Morton |
10 | * Initial version |
11 | * 27Jun2002 axboe@suse.de |
12 | * use bio_add_page() to build bio's just the right size |
13 | */ |
14 | |
15 | #include <linux/kernel.h> |
16 | #include <linux/module.h> |
17 | #include <linux/mm.h> |
18 | #include <linux/kdev_t.h> |
19 | #include <linux/gfp.h> |
20 | #include <linux/bio.h> |
21 | #include <linux/fs.h> |
22 | #include <linux/buffer_head.h> |
23 | #include <linux/blkdev.h> |
24 | #include <linux/highmem.h> |
25 | #include <linux/prefetch.h> |
26 | #include <linux/mpage.h> |
27 | #include <linux/writeback.h> |
28 | #include <linux/backing-dev.h> |
29 | #include <linux/pagevec.h> |
30 | |
31 | /* |
32 | * I/O completion handler for multipage BIOs. |
33 | * |
34 | * The mpage code never puts partial pages into a BIO (except for end-of-file). |
35 | * If a page does not map to a contiguous run of blocks then it simply falls |
36 | * back to block_read_full_page(). |
37 | * |
38 | * Why is this? If a page's completion depends on a number of different BIOs |
39 | * which can complete in any order (or at the same time) then determining the |
40 | * status of that page is hard. See end_buffer_async_read() for the details. |
41 | * There is no point in duplicating all that complexity. |
42 | */ |
43 | static void mpage_end_io(struct bio *bio, int err) |
44 | { |
45 | const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); |
46 | struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1; |
47 | |
48 | do { |
49 | struct page *page = bvec->bv_page; |
50 | |
51 | if (--bvec >= bio->bi_io_vec) |
52 | prefetchw(&bvec->bv_page->flags); |
53 | if (bio_data_dir(bio) == READ) { |
54 | if (uptodate) { |
55 | SetPageUptodate(page); |
56 | } else { |
57 | ClearPageUptodate(page); |
58 | SetPageError(page); |
59 | } |
60 | unlock_page(page); |
61 | } else { /* bio_data_dir(bio) == WRITE */ |
62 | if (!uptodate) { |
63 | SetPageError(page); |
64 | if (page->mapping) |
65 | set_bit(AS_EIO, &page->mapping->flags); |
66 | } |
67 | end_page_writeback(page); |
68 | } |
69 | } while (bvec >= bio->bi_io_vec); |
70 | bio_put(bio); |
71 | } |
72 | |
73 | static struct bio *mpage_bio_submit(int rw, struct bio *bio) |
74 | { |
75 | bio->bi_end_io = mpage_end_io; |
76 | submit_bio(rw, bio); |
77 | return NULL; |
78 | } |
79 | |
80 | static struct bio * |
81 | mpage_alloc(struct block_device *bdev, |
82 | sector_t first_sector, int nr_vecs, |
83 | gfp_t gfp_flags) |
84 | { |
85 | struct bio *bio; |
86 | |
87 | bio = bio_alloc(gfp_flags, nr_vecs); |
88 | |
89 | if (bio == NULL && (current->flags & PF_MEMALLOC)) { |
90 | while (!bio && (nr_vecs /= 2)) |
91 | bio = bio_alloc(gfp_flags, nr_vecs); |
92 | } |
93 | |
94 | if (bio) { |
95 | bio->bi_bdev = bdev; |
96 | bio->bi_sector = first_sector; |
97 | } |
98 | return bio; |
99 | } |
100 | |
101 | /* |
102 | * support function for mpage_readpages. The fs supplied get_block might |
103 | * return an up to date buffer. This is used to map that buffer into |
104 | * the page, which allows readpage to avoid triggering a duplicate call |
105 | * to get_block. |
106 | * |
107 | * The idea is to avoid adding buffers to pages that don't already have |
108 | * them. So when the buffer is up to date and the page size == block size, |
109 | * this marks the page up to date instead of adding new buffers. |
110 | */ |
111 | static void |
112 | map_buffer_to_page(struct page *page, struct buffer_head *bh, int page_block) |
113 | { |
114 | struct inode *inode = page->mapping->host; |
115 | struct buffer_head *page_bh, *head; |
116 | int block = 0; |
117 | |
118 | if (!page_has_buffers(page)) { |
119 | /* |
120 | * don't make any buffers if there is only one buffer on |
121 | * the page and the page just needs to be set up to date |
122 | */ |
123 | if (inode->i_blkbits == PAGE_CACHE_SHIFT && |
124 | buffer_uptodate(bh)) { |
125 | SetPageUptodate(page); |
126 | return; |
127 | } |
128 | create_empty_buffers(page, 1 << inode->i_blkbits, 0); |
129 | } |
130 | head = page_buffers(page); |
131 | page_bh = head; |
132 | do { |
133 | if (block == page_block) { |
134 | page_bh->b_state = bh->b_state; |
135 | page_bh->b_bdev = bh->b_bdev; |
136 | page_bh->b_blocknr = bh->b_blocknr; |
137 | break; |
138 | } |
139 | page_bh = page_bh->b_this_page; |
140 | block++; |
141 | } while (page_bh != head); |
142 | } |
143 | |
144 | /* |
145 | * This is the worker routine which does all the work of mapping the disk |
146 | * blocks and constructs largest possible bios, submits them for IO if the |
147 | * blocks are not contiguous on the disk. |
148 | * |
149 | * We pass a buffer_head back and forth and use its buffer_mapped() flag to |
150 | * represent the validity of its disk mapping and to decide when to do the next |
151 | * get_block() call. |
152 | */ |
153 | static struct bio * |
154 | do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages, |
155 | sector_t *last_block_in_bio, struct buffer_head *map_bh, |
156 | unsigned long *first_logical_block, get_block_t get_block) |
157 | { |
158 | struct inode *inode = page->mapping->host; |
159 | const unsigned blkbits = inode->i_blkbits; |
160 | const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits; |
161 | const unsigned blocksize = 1 << blkbits; |
162 | sector_t block_in_file; |
163 | sector_t last_block; |
164 | sector_t last_block_in_file; |
165 | sector_t blocks[MAX_BUF_PER_PAGE]; |
166 | unsigned page_block; |
167 | unsigned first_hole = blocks_per_page; |
168 | struct block_device *bdev = NULL; |
169 | int length; |
170 | int fully_mapped = 1; |
171 | unsigned nblocks; |
172 | unsigned relative_block; |
173 | |
174 | if (page_has_buffers(page)) |
175 | goto confused; |
176 | |
177 | block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits); |
178 | last_block = block_in_file + nr_pages * blocks_per_page; |
179 | last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits; |
180 | if (last_block > last_block_in_file) |
181 | last_block = last_block_in_file; |
182 | page_block = 0; |
183 | |
184 | /* |
185 | * Map blocks using the result from the previous get_blocks call first. |
186 | */ |
187 | nblocks = map_bh->b_size >> blkbits; |
188 | if (buffer_mapped(map_bh) && block_in_file > *first_logical_block && |
189 | block_in_file < (*first_logical_block + nblocks)) { |
190 | unsigned map_offset = block_in_file - *first_logical_block; |
191 | unsigned last = nblocks - map_offset; |
192 | |
193 | for (relative_block = 0; ; relative_block++) { |
194 | if (relative_block == last) { |
195 | clear_buffer_mapped(map_bh); |
196 | break; |
197 | } |
198 | if (page_block == blocks_per_page) |
199 | break; |
200 | blocks[page_block] = map_bh->b_blocknr + map_offset + |
201 | relative_block; |
202 | page_block++; |
203 | block_in_file++; |
204 | } |
205 | bdev = map_bh->b_bdev; |
206 | } |
207 | |
208 | /* |
209 | * Then do more get_blocks calls until we are done with this page. |
210 | */ |
211 | map_bh->b_page = page; |
212 | while (page_block < blocks_per_page) { |
213 | map_bh->b_state = 0; |
214 | map_bh->b_size = 0; |
215 | |
216 | if (block_in_file < last_block) { |
217 | map_bh->b_size = (last_block-block_in_file) << blkbits; |
218 | if (get_block(inode, block_in_file, map_bh, 0)) |
219 | goto confused; |
220 | *first_logical_block = block_in_file; |
221 | } |
222 | |
223 | if (!buffer_mapped(map_bh)) { |
224 | fully_mapped = 0; |
225 | if (first_hole == blocks_per_page) |
226 | first_hole = page_block; |
227 | page_block++; |
228 | block_in_file++; |
229 | continue; |
230 | } |
231 | |
232 | /* some filesystems will copy data into the page during |
233 | * the get_block call, in which case we don't want to |
234 | * read it again. map_buffer_to_page copies the data |
235 | * we just collected from get_block into the page's buffers |
236 | * so readpage doesn't have to repeat the get_block call |
237 | */ |
238 | if (buffer_uptodate(map_bh)) { |
239 | map_buffer_to_page(page, map_bh, page_block); |
240 | goto confused; |
241 | } |
242 | |
243 | if (first_hole != blocks_per_page) |
244 | goto confused; /* hole -> non-hole */ |
245 | |
246 | /* Contiguous blocks? */ |
247 | if (page_block && blocks[page_block-1] != map_bh->b_blocknr-1) |
248 | goto confused; |
249 | nblocks = map_bh->b_size >> blkbits; |
250 | for (relative_block = 0; ; relative_block++) { |
251 | if (relative_block == nblocks) { |
252 | clear_buffer_mapped(map_bh); |
253 | break; |
254 | } else if (page_block == blocks_per_page) |
255 | break; |
256 | blocks[page_block] = map_bh->b_blocknr+relative_block; |
257 | page_block++; |
258 | block_in_file++; |
259 | } |
260 | bdev = map_bh->b_bdev; |
261 | } |
262 | |
263 | if (first_hole != blocks_per_page) { |
264 | zero_user_segment(page, first_hole << blkbits, PAGE_CACHE_SIZE); |
265 | if (first_hole == 0) { |
266 | SetPageUptodate(page); |
267 | unlock_page(page); |
268 | goto out; |
269 | } |
270 | } else if (fully_mapped) { |
271 | SetPageMappedToDisk(page); |
272 | } |
273 | |
274 | /* |
275 | * This page will go to BIO. Do we need to send this BIO off first? |
276 | */ |
277 | if (bio && (*last_block_in_bio != blocks[0] - 1)) |
278 | bio = mpage_bio_submit(READ, bio); |
279 | |
280 | alloc_new: |
281 | if (bio == NULL) { |
282 | bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9), |
283 | min_t(int, nr_pages, bio_get_nr_vecs(bdev)), |
284 | GFP_KERNEL); |
285 | if (bio == NULL) |
286 | goto confused; |
287 | } |
288 | |
289 | length = first_hole << blkbits; |
290 | if (bio_add_page(bio, page, length, 0) < length) { |
291 | bio = mpage_bio_submit(READ, bio); |
292 | goto alloc_new; |
293 | } |
294 | |
295 | relative_block = block_in_file - *first_logical_block; |
296 | nblocks = map_bh->b_size >> blkbits; |
297 | if ((buffer_boundary(map_bh) && relative_block == nblocks) || |
298 | (first_hole != blocks_per_page)) |
299 | bio = mpage_bio_submit(READ, bio); |
300 | else |
301 | *last_block_in_bio = blocks[blocks_per_page - 1]; |
302 | out: |
303 | return bio; |
304 | |
305 | confused: |
306 | if (bio) |
307 | bio = mpage_bio_submit(READ, bio); |
308 | if (!PageUptodate(page)) |
309 | block_read_full_page(page, get_block); |
310 | else |
311 | unlock_page(page); |
312 | goto out; |
313 | } |
314 | |
315 | /** |
316 | * mpage_readpages - populate an address space with some pages & start reads against them |
317 | * @mapping: the address_space |
318 | * @pages: The address of a list_head which contains the target pages. These |
319 | * pages have their ->index populated and are otherwise uninitialised. |
320 | * The page at @pages->prev has the lowest file offset, and reads should be |
321 | * issued in @pages->prev to @pages->next order. |
322 | * @nr_pages: The number of pages at *@pages |
323 | * @get_block: The filesystem's block mapper function. |
324 | * |
325 | * This function walks the pages and the blocks within each page, building and |
326 | * emitting large BIOs. |
327 | * |
328 | * If anything unusual happens, such as: |
329 | * |
330 | * - encountering a page which has buffers |
331 | * - encountering a page which has a non-hole after a hole |
332 | * - encountering a page with non-contiguous blocks |
333 | * |
334 | * then this code just gives up and calls the buffer_head-based read function. |
335 | * It does handle a page which has holes at the end - that is a common case: |
336 | * the end-of-file on blocksize < PAGE_CACHE_SIZE setups. |
337 | * |
338 | * BH_Boundary explanation: |
339 | * |
340 | * There is a problem. The mpage read code assembles several pages, gets all |
341 | * their disk mappings, and then submits them all. That's fine, but obtaining |
342 | * the disk mappings may require I/O. Reads of indirect blocks, for example. |
343 | * |
344 | * So an mpage read of the first 16 blocks of an ext2 file will cause I/O to be |
345 | * submitted in the following order: |
346 | * 12 0 1 2 3 4 5 6 7 8 9 10 11 13 14 15 16 |
347 | * |
348 | * because the indirect block has to be read to get the mappings of blocks |
349 | * 13,14,15,16. Obviously, this impacts performance. |
350 | * |
351 | * So what we do it to allow the filesystem's get_block() function to set |
352 | * BH_Boundary when it maps block 11. BH_Boundary says: mapping of the block |
353 | * after this one will require I/O against a block which is probably close to |
354 | * this one. So you should push what I/O you have currently accumulated. |
355 | * |
356 | * This all causes the disk requests to be issued in the correct order. |
357 | */ |
358 | int |
359 | mpage_readpages(struct address_space *mapping, struct list_head *pages, |
360 | unsigned nr_pages, get_block_t get_block) |
361 | { |
362 | struct bio *bio = NULL; |
363 | unsigned page_idx; |
364 | sector_t last_block_in_bio = 0; |
365 | struct buffer_head map_bh; |
366 | unsigned long first_logical_block = 0; |
367 | |
368 | map_bh.b_state = 0; |
369 | map_bh.b_size = 0; |
370 | for (page_idx = 0; page_idx < nr_pages; page_idx++) { |
371 | struct page *page = list_entry(pages->prev, struct page, lru); |
372 | |
373 | prefetchw(&page->flags); |
374 | list_del(&page->lru); |
375 | if (!add_to_page_cache_lru(page, mapping, |
376 | page->index, GFP_KERNEL)) { |
377 | bio = do_mpage_readpage(bio, page, |
378 | nr_pages - page_idx, |
379 | &last_block_in_bio, &map_bh, |
380 | &first_logical_block, |
381 | get_block); |
382 | } |
383 | page_cache_release(page); |
384 | } |
385 | BUG_ON(!list_empty(pages)); |
386 | if (bio) |
387 | mpage_bio_submit(READ, bio); |
388 | return 0; |
389 | } |
390 | EXPORT_SYMBOL(mpage_readpages); |
391 | |
392 | /* |
393 | * This isn't called much at all |
394 | */ |
395 | int mpage_readpage(struct page *page, get_block_t get_block) |
396 | { |
397 | struct bio *bio = NULL; |
398 | sector_t last_block_in_bio = 0; |
399 | struct buffer_head map_bh; |
400 | unsigned long first_logical_block = 0; |
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); |
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 | static int __mpage_writepage(struct page *page, struct writeback_control *wbc, |
437 | void *data) |
438 | { |
439 | struct mpage_data *mpd = data; |
440 | struct bio *bio = mpd->bio; |
441 | struct address_space *mapping = page->mapping; |
442 | struct inode *inode = page->mapping->host; |
443 | const unsigned blkbits = inode->i_blkbits; |
444 | unsigned long end_index; |
445 | const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits; |
446 | sector_t last_block; |
447 | sector_t block_in_file; |
448 | sector_t blocks[MAX_BUF_PER_PAGE]; |
449 | unsigned page_block; |
450 | unsigned first_unmapped = blocks_per_page; |
451 | struct block_device *bdev = NULL; |
452 | int boundary = 0; |
453 | sector_t boundary_block = 0; |
454 | struct block_device *boundary_bdev = NULL; |
455 | int length; |
456 | struct buffer_head map_bh; |
457 | loff_t i_size = i_size_read(inode); |
458 | int ret = 0; |
459 | |
460 | if (page_has_buffers(page)) { |
461 | struct buffer_head *head = page_buffers(page); |
462 | struct buffer_head *bh = head; |
463 | |
464 | /* If they're all mapped and dirty, do it */ |
465 | page_block = 0; |
466 | do { |
467 | BUG_ON(buffer_locked(bh)); |
468 | if (!buffer_mapped(bh)) { |
469 | /* |
470 | * unmapped dirty buffers are created by |
471 | * __set_page_dirty_buffers -> mmapped data |
472 | */ |
473 | if (buffer_dirty(bh)) |
474 | goto confused; |
475 | if (first_unmapped == blocks_per_page) |
476 | first_unmapped = page_block; |
477 | continue; |
478 | } |
479 | |
480 | if (first_unmapped != blocks_per_page) |
481 | goto confused; /* hole -> non-hole */ |
482 | |
483 | if (!buffer_dirty(bh) || !buffer_uptodate(bh)) |
484 | goto confused; |
485 | if (page_block) { |
486 | if (bh->b_blocknr != blocks[page_block-1] + 1) |
487 | goto confused; |
488 | } |
489 | blocks[page_block++] = bh->b_blocknr; |
490 | boundary = buffer_boundary(bh); |
491 | if (boundary) { |
492 | boundary_block = bh->b_blocknr; |
493 | boundary_bdev = bh->b_bdev; |
494 | } |
495 | bdev = bh->b_bdev; |
496 | } while ((bh = bh->b_this_page) != head); |
497 | |
498 | if (first_unmapped) |
499 | goto page_is_mapped; |
500 | |
501 | /* |
502 | * Page has buffers, but they are all unmapped. The page was |
503 | * created by pagein or read over a hole which was handled by |
504 | * block_read_full_page(). If this address_space is also |
505 | * using mpage_readpages then this can rarely happen. |
506 | */ |
507 | goto confused; |
508 | } |
509 | |
510 | /* |
511 | * The page has no buffers: map it to disk |
512 | */ |
513 | BUG_ON(!PageUptodate(page)); |
514 | block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits); |
515 | last_block = (i_size - 1) >> blkbits; |
516 | map_bh.b_page = page; |
517 | for (page_block = 0; page_block < blocks_per_page; ) { |
518 | |
519 | map_bh.b_state = 0; |
520 | map_bh.b_size = 1 << blkbits; |
521 | if (mpd->get_block(inode, block_in_file, &map_bh, 1)) |
522 | goto confused; |
523 | if (buffer_new(&map_bh)) |
524 | unmap_underlying_metadata(map_bh.b_bdev, |
525 | map_bh.b_blocknr); |
526 | if (buffer_boundary(&map_bh)) { |
527 | boundary_block = map_bh.b_blocknr; |
528 | boundary_bdev = map_bh.b_bdev; |
529 | } |
530 | if (page_block) { |
531 | if (map_bh.b_blocknr != blocks[page_block-1] + 1) |
532 | goto confused; |
533 | } |
534 | blocks[page_block++] = map_bh.b_blocknr; |
535 | boundary = buffer_boundary(&map_bh); |
536 | bdev = map_bh.b_bdev; |
537 | if (block_in_file == last_block) |
538 | break; |
539 | block_in_file++; |
540 | } |
541 | BUG_ON(page_block == 0); |
542 | |
543 | first_unmapped = page_block; |
544 | |
545 | page_is_mapped: |
546 | end_index = i_size >> PAGE_CACHE_SHIFT; |
547 | if (page->index >= end_index) { |
548 | /* |
549 | * The page straddles i_size. It must be zeroed out on each |
550 | * and every writepage invocation because it may be mmapped. |
551 | * "A file is mapped in multiples of the page size. For a file |
552 | * that is not a multiple of the page size, the remaining memory |
553 | * is zeroed when mapped, and writes to that region are not |
554 | * written out to the file." |
555 | */ |
556 | unsigned offset = i_size & (PAGE_CACHE_SIZE - 1); |
557 | |
558 | if (page->index > end_index || !offset) |
559 | goto confused; |
560 | zero_user_segment(page, offset, PAGE_CACHE_SIZE); |
561 | } |
562 | |
563 | /* |
564 | * This page will go to BIO. Do we need to send this BIO off first? |
565 | */ |
566 | if (bio && mpd->last_block_in_bio != blocks[0] - 1) |
567 | bio = mpage_bio_submit(WRITE, bio); |
568 | |
569 | alloc_new: |
570 | if (bio == NULL) { |
571 | bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9), |
572 | bio_get_nr_vecs(bdev), GFP_NOFS|__GFP_HIGH); |
573 | if (bio == NULL) |
574 | goto confused; |
575 | } |
576 | |
577 | /* |
578 | * Must try to add the page before marking the buffer clean or |
579 | * the confused fail path above (OOM) will be very confused when |
580 | * it finds all bh marked clean (i.e. it will not write anything) |
581 | */ |
582 | length = first_unmapped << blkbits; |
583 | if (bio_add_page(bio, page, length, 0) < length) { |
584 | bio = mpage_bio_submit(WRITE, bio); |
585 | goto alloc_new; |
586 | } |
587 | |
588 | /* |
589 | * OK, we have our BIO, so we can now mark the buffers clean. Make |
590 | * sure to only clean buffers which we know we'll be writing. |
591 | */ |
592 | if (page_has_buffers(page)) { |
593 | struct buffer_head *head = page_buffers(page); |
594 | struct buffer_head *bh = head; |
595 | unsigned buffer_counter = 0; |
596 | |
597 | do { |
598 | if (buffer_counter++ == first_unmapped) |
599 | break; |
600 | clear_buffer_dirty(bh); |
601 | bh = bh->b_this_page; |
602 | } while (bh != head); |
603 | |
604 | /* |
605 | * we cannot drop the bh if the page is not uptodate |
606 | * or a concurrent readpage would fail to serialize with the bh |
607 | * and it would read from disk before we reach the platter. |
608 | */ |
609 | if (buffer_heads_over_limit && PageUptodate(page)) |
610 | try_to_free_buffers(page); |
611 | } |
612 | |
613 | BUG_ON(PageWriteback(page)); |
614 | set_page_writeback(page); |
615 | unlock_page(page); |
616 | if (boundary || (first_unmapped != blocks_per_page)) { |
617 | bio = mpage_bio_submit(WRITE, bio); |
618 | if (boundary_block) { |
619 | write_boundary_block(boundary_bdev, |
620 | boundary_block, 1 << blkbits); |
621 | } |
622 | } else { |
623 | mpd->last_block_in_bio = blocks[blocks_per_page - 1]; |
624 | } |
625 | goto out; |
626 | |
627 | confused: |
628 | if (bio) |
629 | bio = mpage_bio_submit(WRITE, bio); |
630 | |
631 | if (mpd->use_writepage) { |
632 | ret = mapping->a_ops->writepage(page, wbc); |
633 | } else { |
634 | ret = -EAGAIN; |
635 | goto out; |
636 | } |
637 | /* |
638 | * The caller has a ref on the inode, so *mapping is stable |
639 | */ |
640 | mapping_set_error(mapping, ret); |
641 | out: |
642 | mpd->bio = bio; |
643 | return ret; |
644 | } |
645 | |
646 | /** |
647 | * mpage_writepages - walk the list of dirty pages of the given address space & writepage() all of them |
648 | * @mapping: address space structure to write |
649 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write |
650 | * @get_block: the filesystem's block mapper function. |
651 | * If this is NULL then use a_ops->writepage. Otherwise, go |
652 | * direct-to-BIO. |
653 | * |
654 | * This is a library function, which implements the writepages() |
655 | * address_space_operation. |
656 | * |
657 | * If a page is already under I/O, generic_writepages() skips it, even |
658 | * if it's dirty. This is desirable behaviour for memory-cleaning writeback, |
659 | * but it is INCORRECT for data-integrity system calls such as fsync(). fsync() |
660 | * and msync() need to guarantee that all the data which was dirty at the time |
661 | * the call was made get new I/O started against them. If wbc->sync_mode is |
662 | * WB_SYNC_ALL then we were called for data integrity and we must wait for |
663 | * existing IO to complete. |
664 | */ |
665 | int |
666 | mpage_writepages(struct address_space *mapping, |
667 | struct writeback_control *wbc, get_block_t get_block) |
668 | { |
669 | int ret; |
670 | |
671 | if (!get_block) |
672 | ret = generic_writepages(mapping, wbc); |
673 | else { |
674 | struct mpage_data mpd = { |
675 | .bio = NULL, |
676 | .last_block_in_bio = 0, |
677 | .get_block = get_block, |
678 | .use_writepage = 1, |
679 | }; |
680 | |
681 | ret = write_cache_pages(mapping, wbc, __mpage_writepage, &mpd); |
682 | if (mpd.bio) |
683 | mpage_bio_submit(WRITE, mpd.bio); |
684 | } |
685 | return ret; |
686 | } |
687 | EXPORT_SYMBOL(mpage_writepages); |
688 | |
689 | int mpage_writepage(struct page *page, get_block_t get_block, |
690 | struct writeback_control *wbc) |
691 | { |
692 | struct mpage_data mpd = { |
693 | .bio = NULL, |
694 | .last_block_in_bio = 0, |
695 | .get_block = get_block, |
696 | .use_writepage = 0, |
697 | }; |
698 | int ret = __mpage_writepage(page, wbc, &mpd); |
699 | if (mpd.bio) |
700 | mpage_bio_submit(WRITE, mpd.bio); |
701 | return ret; |
702 | } |
703 | EXPORT_SYMBOL(mpage_writepage); |
704 |
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