Branch data Line data Source code
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 : :
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 : : */
44 : 0 : static void mpage_end_io(struct bio *bio, int err)
45 : : {
46 : : struct bio_vec *bv;
47 : : int i;
48 : :
49 [ + + ]: 271067 : bio_for_each_segment_all(bv, bio, i) {
50 : 231769 : struct page *page = bv->bv_page;
51 : :
52 [ + + ]: 231769 : if (bio_data_dir(bio) == READ) {
53 [ + - ]: 231755 : if (!err) {
54 : : SetPageUptodate(page);
55 : : } else {
56 : : ClearPageUptodate(page);
57 : : SetPageError(page);
58 : : }
59 : 231755 : unlock_page(page);
60 : : } else { /* bio_data_dir(bio) == WRITE */
61 [ - + ]: 14 : if (err) {
62 : : SetPageError(page);
63 [ # # ]: 0 : if (page->mapping)
64 : 0 : set_bit(AS_EIO, &page->mapping->flags);
65 : : }
66 : 14 : end_page_writeback(page);
67 : : }
68 : : }
69 : :
70 : 39298 : bio_put(bio);
71 : 39298 : }
72 : :
73 : : static struct bio *mpage_bio_submit(int rw, struct bio *bio)
74 : : {
75 : 39298 : bio->bi_end_io = mpage_end_io;
76 : 269934 : submit_bio(rw, bio);
77 : : return NULL;
78 : : }
79 : :
80 : : static struct bio *
81 : 0 : 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 [ - + ][ # # ]: 39298 : if (bio == NULL && (current->flags & PF_MEMALLOC)) {
90 [ - - ][ # # ]: 39298 : while (!bio && (nr_vecs /= 2))
91 : : bio = bio_alloc(gfp_flags, nr_vecs);
92 : : }
93 : :
94 [ + - ]: 39298 : if (bio) {
95 : 39298 : bio->bi_bdev = bdev;
96 : 39298 : bio->bi_iter.bi_sector = first_sector;
97 : : }
98 : 39298 : 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 : 0 : map_buffer_to_page(struct page *page, struct buffer_head *bh, int page_block)
113 : : {
114 : 0 : struct inode *inode = page->mapping->host;
115 : : struct buffer_head *page_bh, *head;
116 : : int block = 0;
117 : :
118 [ # # ]: 0 : 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 [ # # ][ # # ]: 0 : if (inode->i_blkbits == PAGE_CACHE_SHIFT &&
124 : : buffer_uptodate(bh)) {
125 : : SetPageUptodate(page);
126 : 0 : return;
127 : : }
128 : 0 : create_empty_buffers(page, 1 << inode->i_blkbits, 0);
129 : : }
130 [ # # ]: 0 : head = page_buffers(page);
131 : : page_bh = head;
132 : : do {
133 [ # # ]: 0 : if (block == page_block) {
134 : 0 : page_bh->b_state = bh->b_state;
135 : 0 : page_bh->b_bdev = bh->b_bdev;
136 : 0 : page_bh->b_blocknr = bh->b_blocknr;
137 : 0 : break;
138 : : }
139 : 0 : page_bh = page_bh->b_this_page;
140 : 0 : block++;
141 [ # # ]: 0 : } 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 : 0 : 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 : 422255 : struct inode *inode = page->mapping->host;
159 : 422255 : const unsigned blkbits = inode->i_blkbits;
160 : 422255 : const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits;
161 : 422255 : 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 [ + + ]: 422255 : if (page_has_buffers(page))
175 : : goto confused;
176 : :
177 : 421233 : block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
178 : 421233 : last_block = block_in_file + nr_pages * blocks_per_page;
179 : 421049 : last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits;
180 [ + + ]: 843304 : 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 : 421049 : nblocks = map_bh->b_size >> blkbits;
188 [ + + ][ + - ]: 421049 : if (buffer_mapped(map_bh) && block_in_file > *first_logical_block &&
[ + + ]
189 : 195752 : block_in_file < (*first_logical_block + nblocks)) {
190 : 195726 : unsigned map_offset = block_in_file - *first_logical_block;
191 : 195726 : unsigned last = nblocks - map_offset;
192 : :
193 : 195726 : for (relative_block = 0; ; relative_block++) {
194 [ + + ]: 391452 : if (relative_block == last) {
195 : : clear_buffer_mapped(map_bh);
196 : : break;
197 : : }
198 [ + + ]: 370664 : if (page_block == blocks_per_page)
199 : : break;
200 : 195726 : blocks[page_block] = map_bh->b_blocknr + map_offset +
201 : : relative_block;
202 : 195726 : page_block++;
203 : 195726 : block_in_file++;
204 : 195726 : }
205 : 195726 : bdev = map_bh->b_bdev;
206 : : }
207 : :
208 : : /*
209 : : * Then do more get_blocks calls until we are done with this page.
210 : : */
211 : 421049 : map_bh->b_page = page;
212 [ + + ]: 646664 : while (page_block < blocks_per_page) {
213 : 225359 : map_bh->b_state = 0;
214 : 225359 : map_bh->b_size = 0;
215 : :
216 [ + + ]: 225359 : if (block_in_file < last_block) {
217 : 213828 : map_bh->b_size = (last_block-block_in_file) << blkbits;
218 [ + ]: 213828 : if (get_block(inode, block_in_file, map_bh, 0))
219 : : goto confused;
220 : 214084 : *first_logical_block = block_in_file;
221 : : }
222 : :
223 [ + + ]: 225615 : if (!buffer_mapped(map_bh)) {
224 : : fully_mapped = 0;
225 [ + + ]: 189586 : if (first_hole == blocks_per_page)
226 : : first_hole = page_block;
227 : 189586 : page_block++;
228 : 189586 : block_in_file++;
229 : 189586 : 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 [ - + ]: 36029 : if (buffer_uptodate(map_bh)) {
239 : 0 : map_buffer_to_page(page, map_bh, page_block);
240 : 0 : goto confused;
241 : : }
242 : :
243 [ + - ]: 36029 : if (first_hole != blocks_per_page)
244 : : goto confused; /* hole -> non-hole */
245 : :
246 : : /* Contiguous blocks? */
247 [ - + ][ # # ]: 36029 : if (page_block && blocks[page_block-1] != map_bh->b_blocknr-1)
248 : : goto confused;
249 : 36029 : nblocks = map_bh->b_size >> blkbits;
250 : 36029 : for (relative_block = 0; ; relative_block++) {
251 [ + + ]: 72058 : if (relative_block == nblocks) {
252 : : clear_buffer_mapped(map_bh);
253 : : break;
254 [ + + ]: 56843 : } else if (page_block == blocks_per_page)
255 : : break;
256 : 36029 : blocks[page_block] = map_bh->b_blocknr+relative_block;
257 : 36029 : page_block++;
258 : 36029 : block_in_file++;
259 : 36029 : }
260 : 225615 : bdev = map_bh->b_bdev;
261 : : }
262 : :
263 [ + + ]: 421305 : if (first_hole != blocks_per_page) {
264 : 189563 : zero_user_segment(page, first_hole << blkbits, PAGE_CACHE_SIZE);
265 [ + + ]: 189617 : if (first_hole == 0) {
266 : : SetPageUptodate(page);
267 : 189588 : unlock_page(page);
268 : 189471 : goto out;
269 : : }
270 [ + + ]: 231742 : } else if (fully_mapped) {
271 : : SetPageMappedToDisk(page);
272 : : }
273 : :
274 [ + + ]: 231755 : if (fully_mapped && blocks_per_page == 1 && !PageUptodate(page) &&
275 : : cleancache_get_page(page) == 0) {
276 : : SetPageUptodate(page);
277 : : goto confused;
278 : : }
279 : :
280 : : /*
281 : : * This page will go to BIO. Do we need to send this BIO off first?
282 : : */
283 [ + + ][ + + ]: 231755 : if (bio && (*last_block_in_bio != blocks[0] - 1))
284 : : bio = mpage_bio_submit(READ, bio);
285 : :
286 : : alloc_new:
287 [ + + ]: 234991 : if (bio == NULL) {
288 : 39284 : bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
289 : 39284 : min_t(int, nr_pages, bio_get_nr_vecs(bdev)),
290 : : GFP_KERNEL);
291 [ + + ]: 39284 : if (bio == NULL)
292 : : goto confused;
293 : : }
294 : :
295 : 234899 : length = first_hole << blkbits;
296 [ + + ]: 234899 : if (bio_add_page(bio, page, length, 0) < length) {
297 : : bio = mpage_bio_submit(READ, bio);
298 : 3236 : goto alloc_new;
299 : : }
300 : :
301 : 231755 : relative_block = block_in_file - *first_logical_block;
302 : 231755 : nblocks = map_bh->b_size >> blkbits;
303 [ - + ][ # # ]: 231755 : if ((buffer_boundary(map_bh) && relative_block == nblocks) ||
[ + + ]
304 : : (first_hole != blocks_per_page))
305 : 13 : bio = mpage_bio_submit(READ, bio);
306 : : else
307 : 231742 : *last_block_in_bio = blocks[blocks_per_page - 1];
308 : : out:
309 : 422303 : return bio;
310 : :
311 : : confused:
312 [ - + ]: 1077 : if (bio)
313 : : bio = mpage_bio_submit(READ, bio);
314 [ + - ]: 1077 : if (!PageUptodate(page))
315 : 1077 : block_read_full_page(page, get_block);
316 : : else
317 : 0 : unlock_page(page);
318 : : goto out;
319 : : }
320 : :
321 : : /**
322 : : * mpage_readpages - populate an address space with some pages & start reads against them
323 : : * @mapping: the address_space
324 : : * @pages: The address of a list_head which contains the target pages. These
325 : : * pages have their ->index populated and are otherwise uninitialised.
326 : : * The page at @pages->prev has the lowest file offset, and reads should be
327 : : * issued in @pages->prev to @pages->next order.
328 : : * @nr_pages: The number of pages at *@pages
329 : : * @get_block: The filesystem's block mapper function.
330 : : *
331 : : * This function walks the pages and the blocks within each page, building and
332 : : * emitting large BIOs.
333 : : *
334 : : * If anything unusual happens, such as:
335 : : *
336 : : * - encountering a page which has buffers
337 : : * - encountering a page which has a non-hole after a hole
338 : : * - encountering a page with non-contiguous blocks
339 : : *
340 : : * then this code just gives up and calls the buffer_head-based read function.
341 : : * It does handle a page which has holes at the end - that is a common case:
342 : : * the end-of-file on blocksize < PAGE_CACHE_SIZE setups.
343 : : *
344 : : * BH_Boundary explanation:
345 : : *
346 : : * There is a problem. The mpage read code assembles several pages, gets all
347 : : * their disk mappings, and then submits them all. That's fine, but obtaining
348 : : * the disk mappings may require I/O. Reads of indirect blocks, for example.
349 : : *
350 : : * So an mpage read of the first 16 blocks of an ext2 file will cause I/O to be
351 : : * submitted in the following order:
352 : : * 12 0 1 2 3 4 5 6 7 8 9 10 11 13 14 15 16
353 : : *
354 : : * because the indirect block has to be read to get the mappings of blocks
355 : : * 13,14,15,16. Obviously, this impacts performance.
356 : : *
357 : : * So what we do it to allow the filesystem's get_block() function to set
358 : : * BH_Boundary when it maps block 11. BH_Boundary says: mapping of the block
359 : : * after this one will require I/O against a block which is probably close to
360 : : * this one. So you should push what I/O you have currently accumulated.
361 : : *
362 : : * This all causes the disk requests to be issued in the correct order.
363 : : */
364 : : int
365 : 0 : mpage_readpages(struct address_space *mapping, struct list_head *pages,
366 : : unsigned nr_pages, get_block_t get_block)
367 : : {
368 : : struct bio *bio = NULL;
369 : : unsigned page_idx;
370 : 118633 : sector_t last_block_in_bio = 0;
371 : : struct buffer_head map_bh;
372 : 118633 : unsigned long first_logical_block = 0;
373 : :
374 : 118633 : map_bh.b_state = 0;
375 : 118633 : map_bh.b_size = 0;
376 [ + + ]: 528303 : for (page_idx = 0; page_idx < nr_pages; page_idx++) {
377 : 409595 : struct page *page = list_entry(pages->prev, struct page, lru);
378 : :
379 : 409595 : prefetchw(&page->flags);
380 : : list_del(&page->lru);
381 [ + ]: 409661 : if (!add_to_page_cache_lru(page, mapping,
382 : : page->index, GFP_KERNEL)) {
383 : 409545 : bio = do_mpage_readpage(bio, page,
384 : : nr_pages - page_idx,
385 : : &last_block_in_bio, &map_bh,
386 : : &first_logical_block,
387 : : get_block);
388 : : }
389 : 409544 : page_cache_release(page);
390 : : }
391 [ - + ]: 118708 : BUG_ON(!list_empty(pages));
392 [ + + ]: 118708 : if (bio)
393 : : mpage_bio_submit(READ, bio);
394 : 118708 : return 0;
395 : : }
396 : : EXPORT_SYMBOL(mpage_readpages);
397 : :
398 : : /*
399 : : * This isn't called much at all
400 : : */
401 : 0 : int mpage_readpage(struct page *page, get_block_t get_block)
402 : : {
403 : : struct bio *bio = NULL;
404 : 12754 : sector_t last_block_in_bio = 0;
405 : : struct buffer_head map_bh;
406 : 12754 : unsigned long first_logical_block = 0;
407 : :
408 : 12754 : map_bh.b_state = 0;
409 : 12754 : map_bh.b_size = 0;
410 : 12754 : bio = do_mpage_readpage(bio, page, 1, &last_block_in_bio,
411 : : &map_bh, &first_logical_block, get_block);
412 [ + + ]: 12755 : if (bio)
413 : : mpage_bio_submit(READ, bio);
414 : 1 : return 0;
415 : : }
416 : : EXPORT_SYMBOL(mpage_readpage);
417 : :
418 : : /*
419 : : * Writing is not so simple.
420 : : *
421 : : * If the page has buffers then they will be used for obtaining the disk
422 : : * mapping. We only support pages which are fully mapped-and-dirty, with a
423 : : * special case for pages which are unmapped at the end: end-of-file.
424 : : *
425 : : * If the page has no buffers (preferred) then the page is mapped here.
426 : : *
427 : : * If all blocks are found to be contiguous then the page can go into the
428 : : * BIO. Otherwise fall back to the mapping's writepage().
429 : : *
430 : : * FIXME: This code wants an estimate of how many pages are still to be
431 : : * written, so it can intelligently allocate a suitably-sized BIO. For now,
432 : : * just allocate full-size (16-page) BIOs.
433 : : */
434 : :
435 : : struct mpage_data {
436 : : struct bio *bio;
437 : : sector_t last_block_in_bio;
438 : : get_block_t *get_block;
439 : : unsigned use_writepage;
440 : : };
441 : :
442 : 0 : static int __mpage_writepage(struct page *page, struct writeback_control *wbc,
443 : : void *data)
444 : : {
445 : : struct mpage_data *mpd = data;
446 : 14 : struct bio *bio = mpd->bio;
447 : 14 : struct address_space *mapping = page->mapping;
448 : 14 : struct inode *inode = page->mapping->host;
449 : 14 : const unsigned blkbits = inode->i_blkbits;
450 : : unsigned long end_index;
451 : 14 : const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits;
452 : : sector_t last_block;
453 : : sector_t block_in_file;
454 : : sector_t blocks[MAX_BUF_PER_PAGE];
455 : : unsigned page_block;
456 : : unsigned first_unmapped = blocks_per_page;
457 : : struct block_device *bdev = NULL;
458 : : int boundary = 0;
459 : : sector_t boundary_block = 0;
460 : : struct block_device *boundary_bdev = NULL;
461 : : int length;
462 : : struct buffer_head map_bh;
463 : : loff_t i_size = i_size_read(inode);
464 : : int ret = 0;
465 : :
466 [ + - ]: 14 : if (page_has_buffers(page)) {
467 [ - + ]: 14 : struct buffer_head *head = page_buffers(page);
468 : : struct buffer_head *bh = head;
469 : :
470 : : /* If they're all mapped and dirty, do it */
471 : : page_block = 0;
472 : : do {
473 [ - + ]: 56 : BUG_ON(buffer_locked(bh));
474 [ + + ]: 56 : if (!buffer_mapped(bh)) {
475 : : /*
476 : : * unmapped dirty buffers are created by
477 : : * __set_page_dirty_buffers -> mmapped data
478 : : */
479 [ + - ]: 42 : if (buffer_dirty(bh))
480 : : goto confused;
481 [ + + ]: 42 : if (first_unmapped == blocks_per_page)
482 : : first_unmapped = page_block;
483 : 42 : continue;
484 : : }
485 : :
486 [ + - ]: 14 : if (first_unmapped != blocks_per_page)
487 : : goto confused; /* hole -> non-hole */
488 : :
489 [ + - ][ + - ]: 14 : if (!buffer_dirty(bh) || !buffer_uptodate(bh))
490 : : goto confused;
491 [ - + ]: 14 : if (page_block) {
492 [ # # ]: 0 : if (bh->b_blocknr != blocks[page_block-1] + 1)
493 : : goto confused;
494 : : }
495 : 14 : blocks[page_block++] = bh->b_blocknr;
496 : : boundary = buffer_boundary(bh);
497 [ - + ]: 14 : if (boundary) {
498 : : boundary_block = bh->b_blocknr;
499 : 0 : boundary_bdev = bh->b_bdev;
500 : : }
501 : 14 : bdev = bh->b_bdev;
502 [ + + ]: 56 : } while ((bh = bh->b_this_page) != head);
503 : :
504 [ + - ]: 14 : if (first_unmapped)
505 : : goto page_is_mapped;
506 : :
507 : : /*
508 : : * Page has buffers, but they are all unmapped. The page was
509 : : * created by pagein or read over a hole which was handled by
510 : : * block_read_full_page(). If this address_space is also
511 : : * using mpage_readpages then this can rarely happen.
512 : : */
513 : : goto confused;
514 : : }
515 : :
516 : : /*
517 : : * The page has no buffers: map it to disk
518 : : */
519 [ # # ]: 0 : BUG_ON(!PageUptodate(page));
520 : 0 : block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
521 : 0 : last_block = (i_size - 1) >> blkbits;
522 : 0 : map_bh.b_page = page;
523 [ # # ]: 0 : for (page_block = 0; page_block < blocks_per_page; ) {
524 : :
525 : 0 : map_bh.b_state = 0;
526 : 0 : map_bh.b_size = 1 << blkbits;
527 [ # # ]: 0 : if (mpd->get_block(inode, block_in_file, &map_bh, 1))
528 : : goto confused;
529 [ # # ]: 0 : if (buffer_new(&map_bh))
530 : 0 : unmap_underlying_metadata(map_bh.b_bdev,
531 : : map_bh.b_blocknr);
532 [ # # ]: 14 : if (buffer_boundary(&map_bh)) {
533 : 0 : boundary_block = map_bh.b_blocknr;
534 : 0 : boundary_bdev = map_bh.b_bdev;
535 : : }
536 [ # # ]: 0 : if (page_block) {
537 [ # # ]: 0 : if (map_bh.b_blocknr != blocks[page_block-1] + 1)
538 : : goto confused;
539 : : }
540 : 0 : blocks[page_block++] = map_bh.b_blocknr;
541 : : boundary = buffer_boundary(&map_bh);
542 : 0 : bdev = map_bh.b_bdev;
543 [ # # ]: 0 : if (block_in_file == last_block)
544 : : break;
545 : 0 : block_in_file++;
546 : : }
547 [ # # ]: 0 : BUG_ON(page_block == 0);
548 : :
549 : : first_unmapped = page_block;
550 : :
551 : : page_is_mapped:
552 : 14 : end_index = i_size >> PAGE_CACHE_SHIFT;
553 [ + - ]: 14 : if (page->index >= end_index) {
554 : : /*
555 : : * The page straddles i_size. It must be zeroed out on each
556 : : * and every writepage invocation because it may be mmapped.
557 : : * "A file is mapped in multiples of the page size. For a file
558 : : * that is not a multiple of the page size, the remaining memory
559 : : * is zeroed when mapped, and writes to that region are not
560 : : * written out to the file."
561 : : */
562 : 14 : unsigned offset = i_size & (PAGE_CACHE_SIZE - 1);
563 : :
564 [ + - ][ + - ]: 14 : if (page->index > end_index || !offset)
565 : : goto confused;
566 : : zero_user_segment(page, offset, PAGE_CACHE_SIZE);
567 : : }
568 : :
569 : : /*
570 : : * This page will go to BIO. Do we need to send this BIO off first?
571 : : */
572 [ - + ][ # # ]: 14 : if (bio && mpd->last_block_in_bio != blocks[0] - 1)
573 : : bio = mpage_bio_submit(WRITE, bio);
574 : :
575 : : alloc_new:
576 [ + - ]: 14 : if (bio == NULL) {
577 : 14 : bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
578 : : bio_get_nr_vecs(bdev), GFP_NOFS|__GFP_HIGH);
579 [ + - ]: 14 : if (bio == NULL)
580 : : goto confused;
581 : : }
582 : :
583 : : /*
584 : : * Must try to add the page before marking the buffer clean or
585 : : * the confused fail path above (OOM) will be very confused when
586 : : * it finds all bh marked clean (i.e. it will not write anything)
587 : : */
588 : 14 : length = first_unmapped << blkbits;
589 [ - + ]: 14 : if (bio_add_page(bio, page, length, 0) < length) {
590 : : bio = mpage_bio_submit(WRITE, bio);
591 : 0 : goto alloc_new;
592 : : }
593 : :
594 : : /*
595 : : * OK, we have our BIO, so we can now mark the buffers clean. Make
596 : : * sure to only clean buffers which we know we'll be writing.
597 : : */
598 [ + - ]: 14 : if (page_has_buffers(page)) {
599 [ - + ]: 14 : struct buffer_head *head = page_buffers(page);
600 : : struct buffer_head *bh = head;
601 : : unsigned buffer_counter = 0;
602 : :
603 : : do {
604 [ + + ]: 28 : if (buffer_counter++ == first_unmapped)
605 : : break;
606 : : clear_buffer_dirty(bh);
607 : 14 : bh = bh->b_this_page;
608 [ + - ]: 14 : } while (bh != head);
609 : :
610 : : /*
611 : : * we cannot drop the bh if the page is not uptodate
612 : : * or a concurrent readpage would fail to serialize with the bh
613 : : * and it would read from disk before we reach the platter.
614 : : */
615 [ - + ][ # # ]: 14 : if (buffer_heads_over_limit && PageUptodate(page))
616 : 0 : try_to_free_buffers(page);
617 : : }
618 : :
619 [ - + ]: 14 : BUG_ON(PageWriteback(page));
620 : : set_page_writeback(page);
621 : 14 : unlock_page(page);
622 [ + - ]: 14 : if (boundary || (first_unmapped != blocks_per_page)) {
623 : : bio = mpage_bio_submit(WRITE, bio);
624 [ - + ]: 14 : if (boundary_block) {
625 : 0 : write_boundary_block(boundary_bdev,
626 : 0 : boundary_block, 1 << blkbits);
627 : : }
628 : : } else {
629 : 0 : mpd->last_block_in_bio = blocks[blocks_per_page - 1];
630 : : }
631 : : goto out;
632 : :
633 : : confused:
634 [ # # ]: 0 : if (bio)
635 : : bio = mpage_bio_submit(WRITE, bio);
636 : :
637 [ # # ]: 0 : if (mpd->use_writepage) {
638 : 0 : ret = mapping->a_ops->writepage(page, wbc);
639 : : } else {
640 : : ret = -EAGAIN;
641 : : goto out;
642 : : }
643 : : /*
644 : : * The caller has a ref on the inode, so *mapping is stable
645 : : */
646 : : mapping_set_error(mapping, ret);
647 : : out:
648 : 14 : mpd->bio = bio;
649 : 14 : return ret;
650 : : }
651 : :
652 : : /**
653 : : * mpage_writepages - walk the list of dirty pages of the given address space & writepage() all of them
654 : : * @mapping: address space structure to write
655 : : * @wbc: subtract the number of written pages from *@wbc->nr_to_write
656 : : * @get_block: the filesystem's block mapper function.
657 : : * If this is NULL then use a_ops->writepage. Otherwise, go
658 : : * direct-to-BIO.
659 : : *
660 : : * This is a library function, which implements the writepages()
661 : : * address_space_operation.
662 : : *
663 : : * If a page is already under I/O, generic_writepages() skips it, even
664 : : * if it's dirty. This is desirable behaviour for memory-cleaning writeback,
665 : : * but it is INCORRECT for data-integrity system calls such as fsync(). fsync()
666 : : * and msync() need to guarantee that all the data which was dirty at the time
667 : : * the call was made get new I/O started against them. If wbc->sync_mode is
668 : : * WB_SYNC_ALL then we were called for data integrity and we must wait for
669 : : * existing IO to complete.
670 : : */
671 : : int
672 : 0 : mpage_writepages(struct address_space *mapping,
673 : : struct writeback_control *wbc, get_block_t get_block)
674 : : {
675 : : struct blk_plug plug;
676 : : int ret;
677 : :
678 : 21 : blk_start_plug(&plug);
679 : :
680 [ - + ]: 21 : if (!get_block)
681 : 0 : ret = generic_writepages(mapping, wbc);
682 : : else {
683 : 21 : struct mpage_data mpd = {
684 : : .bio = NULL,
685 : : .last_block_in_bio = 0,
686 : : .get_block = get_block,
687 : : .use_writepage = 1,
688 : : };
689 : :
690 : 21 : ret = write_cache_pages(mapping, wbc, __mpage_writepage, &mpd);
691 [ - + ]: 21 : if (mpd.bio)
692 : : mpage_bio_submit(WRITE, mpd.bio);
693 : : }
694 : 21 : blk_finish_plug(&plug);
695 : 21 : return ret;
696 : : }
697 : : EXPORT_SYMBOL(mpage_writepages);
698 : :
699 : 0 : int mpage_writepage(struct page *page, get_block_t get_block,
700 : : struct writeback_control *wbc)
701 : : {
702 : 0 : struct mpage_data mpd = {
703 : : .bio = NULL,
704 : : .last_block_in_bio = 0,
705 : : .get_block = get_block,
706 : : .use_writepage = 0,
707 : : };
708 : 0 : int ret = __mpage_writepage(page, wbc, &mpd);
709 [ # # ]: 0 : if (mpd.bio)
710 : : mpage_bio_submit(WRITE, mpd.bio);
711 : 0 : return ret;
712 : : }
713 : : EXPORT_SYMBOL(mpage_writepage);
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