Commit | Line | Data |
---|---|---|
1da177e4 LT |
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 | * | |
e1f8e874 | 9 | * 15May2002 Andrew Morton |
1da177e4 LT |
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> | |
630d9c47 | 16 | #include <linux/export.h> |
1da177e4 LT |
17 | #include <linux/mm.h> |
18 | #include <linux/kdev_t.h> | |
5a0e3ad6 | 19 | #include <linux/gfp.h> |
1da177e4 LT |
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> | |
c515e1fd | 30 | #include <linux/cleancache.h> |
1da177e4 LT |
31 | |
32 | /* | |
33 | * I/O completion handler for multipage BIOs. | |
34 | * | |
35 | * The mpage code never puts partial pages into a BIO (except for end-of-file). | |
36 | * If a page does not map to a contiguous run of blocks then it simply falls | |
37 | * back to block_read_full_page(). | |
38 | * | |
39 | * Why is this? If a page's completion depends on a number of different BIOs | |
40 | * which can complete in any order (or at the same time) then determining the | |
41 | * status of that page is hard. See end_buffer_async_read() for the details. | |
42 | * There is no point in duplicating all that complexity. | |
43 | */ | |
c32b0d4b | 44 | static void mpage_end_io(struct bio *bio, int err) |
1da177e4 | 45 | { |
2c30c71b KO |
46 | struct bio_vec *bv; |
47 | int i; | |
1da177e4 | 48 | |
2c30c71b KO |
49 | bio_for_each_segment_all(bv, bio, i) { |
50 | struct page *page = bv->bv_page; | |
57d99845 | 51 | page_endio(page, bio_data_dir(bio), err); |
2c30c71b KO |
52 | } |
53 | ||
1da177e4 | 54 | bio_put(bio); |
1da177e4 LT |
55 | } |
56 | ||
ced117c7 | 57 | static struct bio *mpage_bio_submit(int rw, struct bio *bio) |
1da177e4 | 58 | { |
c32b0d4b | 59 | bio->bi_end_io = mpage_end_io; |
1da177e4 LT |
60 | submit_bio(rw, bio); |
61 | return NULL; | |
62 | } | |
63 | ||
64 | static struct bio * | |
65 | mpage_alloc(struct block_device *bdev, | |
66 | sector_t first_sector, int nr_vecs, | |
dd0fc66f | 67 | gfp_t gfp_flags) |
1da177e4 LT |
68 | { |
69 | struct bio *bio; | |
70 | ||
71 | bio = bio_alloc(gfp_flags, nr_vecs); | |
72 | ||
73 | if (bio == NULL && (current->flags & PF_MEMALLOC)) { | |
74 | while (!bio && (nr_vecs /= 2)) | |
75 | bio = bio_alloc(gfp_flags, nr_vecs); | |
76 | } | |
77 | ||
78 | if (bio) { | |
79 | bio->bi_bdev = bdev; | |
4f024f37 | 80 | bio->bi_iter.bi_sector = first_sector; |
1da177e4 LT |
81 | } |
82 | return bio; | |
83 | } | |
84 | ||
85 | /* | |
86 | * support function for mpage_readpages. The fs supplied get_block might | |
87 | * return an up to date buffer. This is used to map that buffer into | |
88 | * the page, which allows readpage to avoid triggering a duplicate call | |
89 | * to get_block. | |
90 | * | |
91 | * The idea is to avoid adding buffers to pages that don't already have | |
92 | * them. So when the buffer is up to date and the page size == block size, | |
93 | * this marks the page up to date instead of adding new buffers. | |
94 | */ | |
95 | static void | |
96 | map_buffer_to_page(struct page *page, struct buffer_head *bh, int page_block) | |
97 | { | |
98 | struct inode *inode = page->mapping->host; | |
99 | struct buffer_head *page_bh, *head; | |
100 | int block = 0; | |
101 | ||
102 | if (!page_has_buffers(page)) { | |
103 | /* | |
104 | * don't make any buffers if there is only one buffer on | |
105 | * the page and the page just needs to be set up to date | |
106 | */ | |
107 | if (inode->i_blkbits == PAGE_CACHE_SHIFT && | |
108 | buffer_uptodate(bh)) { | |
109 | SetPageUptodate(page); | |
110 | return; | |
111 | } | |
112 | create_empty_buffers(page, 1 << inode->i_blkbits, 0); | |
113 | } | |
114 | head = page_buffers(page); | |
115 | page_bh = head; | |
116 | do { | |
117 | if (block == page_block) { | |
118 | page_bh->b_state = bh->b_state; | |
119 | page_bh->b_bdev = bh->b_bdev; | |
120 | page_bh->b_blocknr = bh->b_blocknr; | |
121 | break; | |
122 | } | |
123 | page_bh = page_bh->b_this_page; | |
124 | block++; | |
125 | } while (page_bh != head); | |
126 | } | |
127 | ||
fa30bd05 BP |
128 | /* |
129 | * This is the worker routine which does all the work of mapping the disk | |
130 | * blocks and constructs largest possible bios, submits them for IO if the | |
131 | * blocks are not contiguous on the disk. | |
132 | * | |
133 | * We pass a buffer_head back and forth and use its buffer_mapped() flag to | |
134 | * represent the validity of its disk mapping and to decide when to do the next | |
135 | * get_block() call. | |
136 | */ | |
1da177e4 LT |
137 | static struct bio * |
138 | do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages, | |
fa30bd05 BP |
139 | sector_t *last_block_in_bio, struct buffer_head *map_bh, |
140 | unsigned long *first_logical_block, get_block_t get_block) | |
1da177e4 LT |
141 | { |
142 | struct inode *inode = page->mapping->host; | |
143 | const unsigned blkbits = inode->i_blkbits; | |
144 | const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits; | |
145 | const unsigned blocksize = 1 << blkbits; | |
146 | sector_t block_in_file; | |
147 | sector_t last_block; | |
fa30bd05 | 148 | sector_t last_block_in_file; |
1da177e4 LT |
149 | sector_t blocks[MAX_BUF_PER_PAGE]; |
150 | unsigned page_block; | |
151 | unsigned first_hole = blocks_per_page; | |
152 | struct block_device *bdev = NULL; | |
1da177e4 LT |
153 | int length; |
154 | int fully_mapped = 1; | |
fa30bd05 BP |
155 | unsigned nblocks; |
156 | unsigned relative_block; | |
1da177e4 LT |
157 | |
158 | if (page_has_buffers(page)) | |
159 | goto confused; | |
160 | ||
54b21a79 | 161 | block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits); |
fa30bd05 BP |
162 | last_block = block_in_file + nr_pages * blocks_per_page; |
163 | last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits; | |
164 | if (last_block > last_block_in_file) | |
165 | last_block = last_block_in_file; | |
166 | page_block = 0; | |
167 | ||
168 | /* | |
169 | * Map blocks using the result from the previous get_blocks call first. | |
170 | */ | |
171 | nblocks = map_bh->b_size >> blkbits; | |
172 | if (buffer_mapped(map_bh) && block_in_file > *first_logical_block && | |
173 | block_in_file < (*first_logical_block + nblocks)) { | |
174 | unsigned map_offset = block_in_file - *first_logical_block; | |
175 | unsigned last = nblocks - map_offset; | |
176 | ||
177 | for (relative_block = 0; ; relative_block++) { | |
178 | if (relative_block == last) { | |
179 | clear_buffer_mapped(map_bh); | |
180 | break; | |
181 | } | |
182 | if (page_block == blocks_per_page) | |
183 | break; | |
184 | blocks[page_block] = map_bh->b_blocknr + map_offset + | |
185 | relative_block; | |
186 | page_block++; | |
187 | block_in_file++; | |
188 | } | |
189 | bdev = map_bh->b_bdev; | |
190 | } | |
191 | ||
192 | /* | |
193 | * Then do more get_blocks calls until we are done with this page. | |
194 | */ | |
195 | map_bh->b_page = page; | |
196 | while (page_block < blocks_per_page) { | |
197 | map_bh->b_state = 0; | |
198 | map_bh->b_size = 0; | |
1da177e4 | 199 | |
1da177e4 | 200 | if (block_in_file < last_block) { |
fa30bd05 BP |
201 | map_bh->b_size = (last_block-block_in_file) << blkbits; |
202 | if (get_block(inode, block_in_file, map_bh, 0)) | |
1da177e4 | 203 | goto confused; |
fa30bd05 | 204 | *first_logical_block = block_in_file; |
1da177e4 LT |
205 | } |
206 | ||
fa30bd05 | 207 | if (!buffer_mapped(map_bh)) { |
1da177e4 LT |
208 | fully_mapped = 0; |
209 | if (first_hole == blocks_per_page) | |
210 | first_hole = page_block; | |
fa30bd05 BP |
211 | page_block++; |
212 | block_in_file++; | |
1da177e4 LT |
213 | continue; |
214 | } | |
215 | ||
216 | /* some filesystems will copy data into the page during | |
217 | * the get_block call, in which case we don't want to | |
218 | * read it again. map_buffer_to_page copies the data | |
219 | * we just collected from get_block into the page's buffers | |
220 | * so readpage doesn't have to repeat the get_block call | |
221 | */ | |
fa30bd05 BP |
222 | if (buffer_uptodate(map_bh)) { |
223 | map_buffer_to_page(page, map_bh, page_block); | |
1da177e4 LT |
224 | goto confused; |
225 | } | |
226 | ||
227 | if (first_hole != blocks_per_page) | |
228 | goto confused; /* hole -> non-hole */ | |
229 | ||
230 | /* Contiguous blocks? */ | |
fa30bd05 | 231 | if (page_block && blocks[page_block-1] != map_bh->b_blocknr-1) |
1da177e4 | 232 | goto confused; |
fa30bd05 BP |
233 | nblocks = map_bh->b_size >> blkbits; |
234 | for (relative_block = 0; ; relative_block++) { | |
235 | if (relative_block == nblocks) { | |
236 | clear_buffer_mapped(map_bh); | |
237 | break; | |
238 | } else if (page_block == blocks_per_page) | |
239 | break; | |
240 | blocks[page_block] = map_bh->b_blocknr+relative_block; | |
241 | page_block++; | |
242 | block_in_file++; | |
243 | } | |
244 | bdev = map_bh->b_bdev; | |
1da177e4 LT |
245 | } |
246 | ||
247 | if (first_hole != blocks_per_page) { | |
eebd2aa3 | 248 | zero_user_segment(page, first_hole << blkbits, PAGE_CACHE_SIZE); |
1da177e4 LT |
249 | if (first_hole == 0) { |
250 | SetPageUptodate(page); | |
251 | unlock_page(page); | |
252 | goto out; | |
253 | } | |
254 | } else if (fully_mapped) { | |
255 | SetPageMappedToDisk(page); | |
256 | } | |
257 | ||
c515e1fd DM |
258 | if (fully_mapped && blocks_per_page == 1 && !PageUptodate(page) && |
259 | cleancache_get_page(page) == 0) { | |
260 | SetPageUptodate(page); | |
261 | goto confused; | |
262 | } | |
263 | ||
1da177e4 LT |
264 | /* |
265 | * This page will go to BIO. Do we need to send this BIO off first? | |
266 | */ | |
267 | if (bio && (*last_block_in_bio != blocks[0] - 1)) | |
268 | bio = mpage_bio_submit(READ, bio); | |
269 | ||
270 | alloc_new: | |
271 | if (bio == NULL) { | |
272 | bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9), | |
273 | min_t(int, nr_pages, bio_get_nr_vecs(bdev)), | |
274 | GFP_KERNEL); | |
275 | if (bio == NULL) | |
276 | goto confused; | |
277 | } | |
278 | ||
279 | length = first_hole << blkbits; | |
280 | if (bio_add_page(bio, page, length, 0) < length) { | |
281 | bio = mpage_bio_submit(READ, bio); | |
282 | goto alloc_new; | |
283 | } | |
284 | ||
38c8e618 MS |
285 | relative_block = block_in_file - *first_logical_block; |
286 | nblocks = map_bh->b_size >> blkbits; | |
287 | if ((buffer_boundary(map_bh) && relative_block == nblocks) || | |
288 | (first_hole != blocks_per_page)) | |
1da177e4 LT |
289 | bio = mpage_bio_submit(READ, bio); |
290 | else | |
291 | *last_block_in_bio = blocks[blocks_per_page - 1]; | |
292 | out: | |
293 | return bio; | |
294 | ||
295 | confused: | |
296 | if (bio) | |
297 | bio = mpage_bio_submit(READ, bio); | |
298 | if (!PageUptodate(page)) | |
299 | block_read_full_page(page, get_block); | |
300 | else | |
301 | unlock_page(page); | |
302 | goto out; | |
303 | } | |
304 | ||
67be2dd1 | 305 | /** |
78a4a50a | 306 | * mpage_readpages - populate an address space with some pages & start reads against them |
67be2dd1 MW |
307 | * @mapping: the address_space |
308 | * @pages: The address of a list_head which contains the target pages. These | |
309 | * pages have their ->index populated and are otherwise uninitialised. | |
67be2dd1 MW |
310 | * The page at @pages->prev has the lowest file offset, and reads should be |
311 | * issued in @pages->prev to @pages->next order. | |
67be2dd1 MW |
312 | * @nr_pages: The number of pages at *@pages |
313 | * @get_block: The filesystem's block mapper function. | |
314 | * | |
315 | * This function walks the pages and the blocks within each page, building and | |
316 | * emitting large BIOs. | |
317 | * | |
318 | * If anything unusual happens, such as: | |
319 | * | |
320 | * - encountering a page which has buffers | |
321 | * - encountering a page which has a non-hole after a hole | |
322 | * - encountering a page with non-contiguous blocks | |
323 | * | |
324 | * then this code just gives up and calls the buffer_head-based read function. | |
325 | * It does handle a page which has holes at the end - that is a common case: | |
326 | * the end-of-file on blocksize < PAGE_CACHE_SIZE setups. | |
327 | * | |
328 | * BH_Boundary explanation: | |
329 | * | |
330 | * There is a problem. The mpage read code assembles several pages, gets all | |
331 | * their disk mappings, and then submits them all. That's fine, but obtaining | |
332 | * the disk mappings may require I/O. Reads of indirect blocks, for example. | |
333 | * | |
334 | * So an mpage read of the first 16 blocks of an ext2 file will cause I/O to be | |
335 | * submitted in the following order: | |
336 | * 12 0 1 2 3 4 5 6 7 8 9 10 11 13 14 15 16 | |
78a4a50a | 337 | * |
67be2dd1 MW |
338 | * because the indirect block has to be read to get the mappings of blocks |
339 | * 13,14,15,16. Obviously, this impacts performance. | |
340 | * | |
341 | * So what we do it to allow the filesystem's get_block() function to set | |
342 | * BH_Boundary when it maps block 11. BH_Boundary says: mapping of the block | |
343 | * after this one will require I/O against a block which is probably close to | |
344 | * this one. So you should push what I/O you have currently accumulated. | |
345 | * | |
346 | * This all causes the disk requests to be issued in the correct order. | |
347 | */ | |
1da177e4 LT |
348 | int |
349 | mpage_readpages(struct address_space *mapping, struct list_head *pages, | |
350 | unsigned nr_pages, get_block_t get_block) | |
351 | { | |
352 | struct bio *bio = NULL; | |
353 | unsigned page_idx; | |
354 | sector_t last_block_in_bio = 0; | |
fa30bd05 BP |
355 | struct buffer_head map_bh; |
356 | unsigned long first_logical_block = 0; | |
1da177e4 | 357 | |
79ffab34 AK |
358 | map_bh.b_state = 0; |
359 | map_bh.b_size = 0; | |
1da177e4 LT |
360 | for (page_idx = 0; page_idx < nr_pages; page_idx++) { |
361 | struct page *page = list_entry(pages->prev, struct page, lru); | |
362 | ||
363 | prefetchw(&page->flags); | |
364 | list_del(&page->lru); | |
eb2be189 | 365 | if (!add_to_page_cache_lru(page, mapping, |
1da177e4 LT |
366 | page->index, GFP_KERNEL)) { |
367 | bio = do_mpage_readpage(bio, page, | |
368 | nr_pages - page_idx, | |
fa30bd05 BP |
369 | &last_block_in_bio, &map_bh, |
370 | &first_logical_block, | |
371 | get_block); | |
1da177e4 | 372 | } |
eb2be189 | 373 | page_cache_release(page); |
1da177e4 | 374 | } |
1da177e4 LT |
375 | BUG_ON(!list_empty(pages)); |
376 | if (bio) | |
377 | mpage_bio_submit(READ, bio); | |
378 | return 0; | |
379 | } | |
380 | EXPORT_SYMBOL(mpage_readpages); | |
381 | ||
382 | /* | |
383 | * This isn't called much at all | |
384 | */ | |
385 | int mpage_readpage(struct page *page, get_block_t get_block) | |
386 | { | |
387 | struct bio *bio = NULL; | |
388 | sector_t last_block_in_bio = 0; | |
fa30bd05 BP |
389 | struct buffer_head map_bh; |
390 | unsigned long first_logical_block = 0; | |
1da177e4 | 391 | |
79ffab34 AK |
392 | map_bh.b_state = 0; |
393 | map_bh.b_size = 0; | |
fa30bd05 BP |
394 | bio = do_mpage_readpage(bio, page, 1, &last_block_in_bio, |
395 | &map_bh, &first_logical_block, get_block); | |
1da177e4 LT |
396 | if (bio) |
397 | mpage_bio_submit(READ, bio); | |
398 | return 0; | |
399 | } | |
400 | EXPORT_SYMBOL(mpage_readpage); | |
401 | ||
402 | /* | |
403 | * Writing is not so simple. | |
404 | * | |
405 | * If the page has buffers then they will be used for obtaining the disk | |
406 | * mapping. We only support pages which are fully mapped-and-dirty, with a | |
407 | * special case for pages which are unmapped at the end: end-of-file. | |
408 | * | |
409 | * If the page has no buffers (preferred) then the page is mapped here. | |
410 | * | |
411 | * If all blocks are found to be contiguous then the page can go into the | |
412 | * BIO. Otherwise fall back to the mapping's writepage(). | |
413 | * | |
414 | * FIXME: This code wants an estimate of how many pages are still to be | |
415 | * written, so it can intelligently allocate a suitably-sized BIO. For now, | |
416 | * just allocate full-size (16-page) BIOs. | |
417 | */ | |
0ea97180 | 418 | |
ced117c7 DV |
419 | struct mpage_data { |
420 | struct bio *bio; | |
421 | sector_t last_block_in_bio; | |
422 | get_block_t *get_block; | |
423 | unsigned use_writepage; | |
424 | }; | |
425 | ||
90768eee MW |
426 | /* |
427 | * We have our BIO, so we can now mark the buffers clean. Make | |
428 | * sure to only clean buffers which we know we'll be writing. | |
429 | */ | |
430 | static void clean_buffers(struct page *page, unsigned first_unmapped) | |
431 | { | |
432 | unsigned buffer_counter = 0; | |
433 | struct buffer_head *bh, *head; | |
434 | if (!page_has_buffers(page)) | |
435 | return; | |
436 | head = page_buffers(page); | |
437 | bh = head; | |
438 | ||
439 | do { | |
440 | if (buffer_counter++ == first_unmapped) | |
441 | break; | |
442 | clear_buffer_dirty(bh); | |
443 | bh = bh->b_this_page; | |
444 | } while (bh != head); | |
445 | ||
446 | /* | |
447 | * we cannot drop the bh if the page is not uptodate or a concurrent | |
448 | * readpage would fail to serialize with the bh and it would read from | |
449 | * disk before we reach the platter. | |
450 | */ | |
451 | if (buffer_heads_over_limit && PageUptodate(page)) | |
452 | try_to_free_buffers(page); | |
453 | } | |
454 | ||
ced117c7 | 455 | static int __mpage_writepage(struct page *page, struct writeback_control *wbc, |
29a814d2 | 456 | void *data) |
1da177e4 | 457 | { |
0ea97180 MS |
458 | struct mpage_data *mpd = data; |
459 | struct bio *bio = mpd->bio; | |
1da177e4 LT |
460 | struct address_space *mapping = page->mapping; |
461 | struct inode *inode = page->mapping->host; | |
462 | const unsigned blkbits = inode->i_blkbits; | |
463 | unsigned long end_index; | |
464 | const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits; | |
465 | sector_t last_block; | |
466 | sector_t block_in_file; | |
467 | sector_t blocks[MAX_BUF_PER_PAGE]; | |
468 | unsigned page_block; | |
469 | unsigned first_unmapped = blocks_per_page; | |
470 | struct block_device *bdev = NULL; | |
471 | int boundary = 0; | |
472 | sector_t boundary_block = 0; | |
473 | struct block_device *boundary_bdev = NULL; | |
474 | int length; | |
475 | struct buffer_head map_bh; | |
476 | loff_t i_size = i_size_read(inode); | |
0ea97180 | 477 | int ret = 0; |
1da177e4 LT |
478 | |
479 | if (page_has_buffers(page)) { | |
480 | struct buffer_head *head = page_buffers(page); | |
481 | struct buffer_head *bh = head; | |
482 | ||
483 | /* If they're all mapped and dirty, do it */ | |
484 | page_block = 0; | |
485 | do { | |
486 | BUG_ON(buffer_locked(bh)); | |
487 | if (!buffer_mapped(bh)) { | |
488 | /* | |
489 | * unmapped dirty buffers are created by | |
490 | * __set_page_dirty_buffers -> mmapped data | |
491 | */ | |
492 | if (buffer_dirty(bh)) | |
493 | goto confused; | |
494 | if (first_unmapped == blocks_per_page) | |
495 | first_unmapped = page_block; | |
496 | continue; | |
497 | } | |
498 | ||
499 | if (first_unmapped != blocks_per_page) | |
500 | goto confused; /* hole -> non-hole */ | |
501 | ||
502 | if (!buffer_dirty(bh) || !buffer_uptodate(bh)) | |
503 | goto confused; | |
504 | if (page_block) { | |
505 | if (bh->b_blocknr != blocks[page_block-1] + 1) | |
506 | goto confused; | |
507 | } | |
508 | blocks[page_block++] = bh->b_blocknr; | |
509 | boundary = buffer_boundary(bh); | |
510 | if (boundary) { | |
511 | boundary_block = bh->b_blocknr; | |
512 | boundary_bdev = bh->b_bdev; | |
513 | } | |
514 | bdev = bh->b_bdev; | |
515 | } while ((bh = bh->b_this_page) != head); | |
516 | ||
517 | if (first_unmapped) | |
518 | goto page_is_mapped; | |
519 | ||
520 | /* | |
521 | * Page has buffers, but they are all unmapped. The page was | |
522 | * created by pagein or read over a hole which was handled by | |
523 | * block_read_full_page(). If this address_space is also | |
524 | * using mpage_readpages then this can rarely happen. | |
525 | */ | |
526 | goto confused; | |
527 | } | |
528 | ||
529 | /* | |
530 | * The page has no buffers: map it to disk | |
531 | */ | |
532 | BUG_ON(!PageUptodate(page)); | |
54b21a79 | 533 | block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits); |
1da177e4 LT |
534 | last_block = (i_size - 1) >> blkbits; |
535 | map_bh.b_page = page; | |
536 | for (page_block = 0; page_block < blocks_per_page; ) { | |
537 | ||
538 | map_bh.b_state = 0; | |
b0cf2321 | 539 | map_bh.b_size = 1 << blkbits; |
0ea97180 | 540 | if (mpd->get_block(inode, block_in_file, &map_bh, 1)) |
1da177e4 LT |
541 | goto confused; |
542 | if (buffer_new(&map_bh)) | |
543 | unmap_underlying_metadata(map_bh.b_bdev, | |
544 | map_bh.b_blocknr); | |
545 | if (buffer_boundary(&map_bh)) { | |
546 | boundary_block = map_bh.b_blocknr; | |
547 | boundary_bdev = map_bh.b_bdev; | |
548 | } | |
549 | if (page_block) { | |
550 | if (map_bh.b_blocknr != blocks[page_block-1] + 1) | |
551 | goto confused; | |
552 | } | |
553 | blocks[page_block++] = map_bh.b_blocknr; | |
554 | boundary = buffer_boundary(&map_bh); | |
555 | bdev = map_bh.b_bdev; | |
556 | if (block_in_file == last_block) | |
557 | break; | |
558 | block_in_file++; | |
559 | } | |
560 | BUG_ON(page_block == 0); | |
561 | ||
562 | first_unmapped = page_block; | |
563 | ||
564 | page_is_mapped: | |
565 | end_index = i_size >> PAGE_CACHE_SHIFT; | |
566 | if (page->index >= end_index) { | |
567 | /* | |
568 | * The page straddles i_size. It must be zeroed out on each | |
2a61aa40 | 569 | * and every writepage invocation because it may be mmapped. |
1da177e4 LT |
570 | * "A file is mapped in multiples of the page size. For a file |
571 | * that is not a multiple of the page size, the remaining memory | |
572 | * is zeroed when mapped, and writes to that region are not | |
573 | * written out to the file." | |
574 | */ | |
575 | unsigned offset = i_size & (PAGE_CACHE_SIZE - 1); | |
1da177e4 LT |
576 | |
577 | if (page->index > end_index || !offset) | |
578 | goto confused; | |
eebd2aa3 | 579 | zero_user_segment(page, offset, PAGE_CACHE_SIZE); |
1da177e4 LT |
580 | } |
581 | ||
582 | /* | |
583 | * This page will go to BIO. Do we need to send this BIO off first? | |
584 | */ | |
0ea97180 | 585 | if (bio && mpd->last_block_in_bio != blocks[0] - 1) |
1da177e4 LT |
586 | bio = mpage_bio_submit(WRITE, bio); |
587 | ||
588 | alloc_new: | |
589 | if (bio == NULL) { | |
590 | bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9), | |
591 | bio_get_nr_vecs(bdev), GFP_NOFS|__GFP_HIGH); | |
592 | if (bio == NULL) | |
593 | goto confused; | |
594 | } | |
595 | ||
596 | /* | |
597 | * Must try to add the page before marking the buffer clean or | |
598 | * the confused fail path above (OOM) will be very confused when | |
599 | * it finds all bh marked clean (i.e. it will not write anything) | |
600 | */ | |
601 | length = first_unmapped << blkbits; | |
602 | if (bio_add_page(bio, page, length, 0) < length) { | |
603 | bio = mpage_bio_submit(WRITE, bio); | |
604 | goto alloc_new; | |
605 | } | |
606 | ||
90768eee | 607 | clean_buffers(page, first_unmapped); |
1da177e4 LT |
608 | |
609 | BUG_ON(PageWriteback(page)); | |
610 | set_page_writeback(page); | |
611 | unlock_page(page); | |
612 | if (boundary || (first_unmapped != blocks_per_page)) { | |
613 | bio = mpage_bio_submit(WRITE, bio); | |
614 | if (boundary_block) { | |
615 | write_boundary_block(boundary_bdev, | |
616 | boundary_block, 1 << blkbits); | |
617 | } | |
618 | } else { | |
0ea97180 | 619 | mpd->last_block_in_bio = blocks[blocks_per_page - 1]; |
1da177e4 LT |
620 | } |
621 | goto out; | |
622 | ||
623 | confused: | |
624 | if (bio) | |
625 | bio = mpage_bio_submit(WRITE, bio); | |
626 | ||
0ea97180 MS |
627 | if (mpd->use_writepage) { |
628 | ret = mapping->a_ops->writepage(page, wbc); | |
1da177e4 | 629 | } else { |
0ea97180 | 630 | ret = -EAGAIN; |
1da177e4 LT |
631 | goto out; |
632 | } | |
633 | /* | |
634 | * The caller has a ref on the inode, so *mapping is stable | |
635 | */ | |
0ea97180 | 636 | mapping_set_error(mapping, ret); |
1da177e4 | 637 | out: |
0ea97180 MS |
638 | mpd->bio = bio; |
639 | return ret; | |
1da177e4 LT |
640 | } |
641 | ||
642 | /** | |
78a4a50a | 643 | * mpage_writepages - walk the list of dirty pages of the given address space & writepage() all of them |
1da177e4 LT |
644 | * @mapping: address space structure to write |
645 | * @wbc: subtract the number of written pages from *@wbc->nr_to_write | |
646 | * @get_block: the filesystem's block mapper function. | |
647 | * If this is NULL then use a_ops->writepage. Otherwise, go | |
648 | * direct-to-BIO. | |
649 | * | |
650 | * This is a library function, which implements the writepages() | |
651 | * address_space_operation. | |
652 | * | |
653 | * If a page is already under I/O, generic_writepages() skips it, even | |
654 | * if it's dirty. This is desirable behaviour for memory-cleaning writeback, | |
655 | * but it is INCORRECT for data-integrity system calls such as fsync(). fsync() | |
656 | * and msync() need to guarantee that all the data which was dirty at the time | |
657 | * the call was made get new I/O started against them. If wbc->sync_mode is | |
658 | * WB_SYNC_ALL then we were called for data integrity and we must wait for | |
659 | * existing IO to complete. | |
660 | */ | |
661 | int | |
662 | mpage_writepages(struct address_space *mapping, | |
663 | struct writeback_control *wbc, get_block_t get_block) | |
1da177e4 | 664 | { |
2ed1a6bc | 665 | struct blk_plug plug; |
0ea97180 MS |
666 | int ret; |
667 | ||
2ed1a6bc JA |
668 | blk_start_plug(&plug); |
669 | ||
0ea97180 MS |
670 | if (!get_block) |
671 | ret = generic_writepages(mapping, wbc); | |
672 | else { | |
673 | struct mpage_data mpd = { | |
674 | .bio = NULL, | |
675 | .last_block_in_bio = 0, | |
676 | .get_block = get_block, | |
677 | .use_writepage = 1, | |
678 | }; | |
679 | ||
680 | ret = write_cache_pages(mapping, wbc, __mpage_writepage, &mpd); | |
681 | if (mpd.bio) | |
682 | mpage_bio_submit(WRITE, mpd.bio); | |
1da177e4 | 683 | } |
2ed1a6bc | 684 | blk_finish_plug(&plug); |
1da177e4 LT |
685 | return ret; |
686 | } | |
687 | EXPORT_SYMBOL(mpage_writepages); | |
1da177e4 LT |
688 | |
689 | int mpage_writepage(struct page *page, get_block_t get_block, | |
690 | struct writeback_control *wbc) | |
691 | { | |
0ea97180 MS |
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); | |
1da177e4 LT |
701 | return ret; |
702 | } | |
703 | EXPORT_SYMBOL(mpage_writepage); |