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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/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/mm_inline.h>
28#include <linux/writeback.h>
29#include <linux/backing-dev.h>
30#include <linux/pagevec.h>
31#include <linux/cleancache.h>
32#include "internal.h"
33
34#define CREATE_TRACE_POINTS
35#include <trace/events/android_fs.h>
36
37EXPORT_TRACEPOINT_SYMBOL(android_fs_datawrite_start);
38EXPORT_TRACEPOINT_SYMBOL(android_fs_datawrite_end);
39EXPORT_TRACEPOINT_SYMBOL(android_fs_dataread_start);
40EXPORT_TRACEPOINT_SYMBOL(android_fs_dataread_end);
41
42/*
43 * I/O completion handler for multipage BIOs.
44 *
45 * The mpage code never puts partial pages into a BIO (except for end-of-file).
46 * If a page does not map to a contiguous run of blocks then it simply falls
47 * back to block_read_full_page().
48 *
49 * Why is this? If a page's completion depends on a number of different BIOs
50 * which can complete in any order (or at the same time) then determining the
51 * status of that page is hard. See end_buffer_async_read() for the details.
52 * There is no point in duplicating all that complexity.
53 */
54static void mpage_end_io(struct bio *bio)
55{
56 struct bio_vec *bv;
57 int i;
58
59 if (trace_android_fs_dataread_end_enabled() &&
60 (bio_data_dir(bio) == READ)) {
61 struct page *first_page = bio->bi_io_vec[0].bv_page;
62
63 if (first_page != NULL)
64 trace_android_fs_dataread_end(first_page->mapping->host,
65 page_offset(first_page),
66 bio->bi_iter.bi_size);
67 }
68
69 bio_for_each_segment_all(bv, bio, i) {
70 struct page *page = bv->bv_page;
71 page_endio(page, op_is_write(bio_op(bio)), bio->bi_error);
72 }
73
74 bio_put(bio);
75}
76
77static struct bio *mpage_bio_submit(int op, int op_flags, struct bio *bio)
78{
79 if (trace_android_fs_dataread_start_enabled() && (op == REQ_OP_READ)) {
80 struct page *first_page = bio->bi_io_vec[0].bv_page;
81
82 if (first_page != NULL) {
83 #ifdef CONFIG_AMLOGIC_VMAP
84 trace_android_fs_dataread_wrap(
85 first_page->mapping->host,
86 page_offset(first_page),
87 bio->bi_iter.bi_size);
88 #else
89 char *path, pathbuf[MAX_TRACE_PATHBUF_LEN];
90
91 path = android_fstrace_get_pathname(pathbuf,
92 MAX_TRACE_PATHBUF_LEN,
93 first_page->mapping->host);
94 trace_android_fs_dataread_start(
95 first_page->mapping->host,
96 page_offset(first_page),
97 bio->bi_iter.bi_size,
98 current->pid,
99 path,
100 current->comm);
101 #endif
102 }
103 }
104 bio->bi_end_io = mpage_end_io;
105 bio_set_op_attrs(bio, op, op_flags);
106 guard_bio_eod(op, bio);
107 submit_bio(bio);
108 return NULL;
109}
110
111static struct bio *
112mpage_alloc(struct block_device *bdev,
113 sector_t first_sector, int nr_vecs,
114 gfp_t gfp_flags)
115{
116 struct bio *bio;
117
118 /* Restrict the given (page cache) mask for slab allocations */
119 gfp_flags &= GFP_KERNEL;
120 bio = bio_alloc(gfp_flags, nr_vecs);
121
122 if (bio == NULL && (current->flags & PF_MEMALLOC)) {
123 while (!bio && (nr_vecs /= 2))
124 bio = bio_alloc(gfp_flags, nr_vecs);
125 }
126
127 if (bio) {
128 bio->bi_bdev = bdev;
129 bio->bi_iter.bi_sector = first_sector;
130 }
131 return bio;
132}
133
134/*
135 * support function for mpage_readpages. The fs supplied get_block might
136 * return an up to date buffer. This is used to map that buffer into
137 * the page, which allows readpage to avoid triggering a duplicate call
138 * to get_block.
139 *
140 * The idea is to avoid adding buffers to pages that don't already have
141 * them. So when the buffer is up to date and the page size == block size,
142 * this marks the page up to date instead of adding new buffers.
143 */
144static void
145map_buffer_to_page(struct page *page, struct buffer_head *bh, int page_block)
146{
147 struct inode *inode = page->mapping->host;
148 struct buffer_head *page_bh, *head;
149 int block = 0;
150
151 if (!page_has_buffers(page)) {
152 /*
153 * don't make any buffers if there is only one buffer on
154 * the page and the page just needs to be set up to date
155 */
156 if (inode->i_blkbits == PAGE_SHIFT &&
157 buffer_uptodate(bh)) {
158 SetPageUptodate(page);
159 return;
160 }
161 create_empty_buffers(page, i_blocksize(inode), 0);
162 }
163 head = page_buffers(page);
164 page_bh = head;
165 do {
166 if (block == page_block) {
167 page_bh->b_state = bh->b_state;
168 page_bh->b_bdev = bh->b_bdev;
169 page_bh->b_blocknr = bh->b_blocknr;
170 break;
171 }
172 page_bh = page_bh->b_this_page;
173 block++;
174 } while (page_bh != head);
175}
176
177/*
178 * This is the worker routine which does all the work of mapping the disk
179 * blocks and constructs largest possible bios, submits them for IO if the
180 * blocks are not contiguous on the disk.
181 *
182 * We pass a buffer_head back and forth and use its buffer_mapped() flag to
183 * represent the validity of its disk mapping and to decide when to do the next
184 * get_block() call.
185 */
186static struct bio *
187do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
188 sector_t *last_block_in_bio, struct buffer_head *map_bh,
189 unsigned long *first_logical_block, get_block_t get_block,
190 gfp_t gfp)
191{
192 struct inode *inode = page->mapping->host;
193 const unsigned blkbits = inode->i_blkbits;
194 const unsigned blocks_per_page = PAGE_SIZE >> blkbits;
195 const unsigned blocksize = 1 << blkbits;
196 sector_t block_in_file;
197 sector_t last_block;
198 sector_t last_block_in_file;
199 sector_t blocks[MAX_BUF_PER_PAGE];
200 unsigned page_block;
201 unsigned first_hole = blocks_per_page;
202 struct block_device *bdev = NULL;
203 int length;
204 int fully_mapped = 1;
205 unsigned nblocks;
206 unsigned relative_block;
207
208 if (page_has_buffers(page))
209 goto confused;
210
211 block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
212 last_block = block_in_file + nr_pages * blocks_per_page;
213 last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits;
214 if (last_block > last_block_in_file)
215 last_block = last_block_in_file;
216 page_block = 0;
217
218 /*
219 * Map blocks using the result from the previous get_blocks call first.
220 */
221 nblocks = map_bh->b_size >> blkbits;
222 if (buffer_mapped(map_bh) && block_in_file > *first_logical_block &&
223 block_in_file < (*first_logical_block + nblocks)) {
224 unsigned map_offset = block_in_file - *first_logical_block;
225 unsigned last = nblocks - map_offset;
226
227 for (relative_block = 0; ; relative_block++) {
228 if (relative_block == last) {
229 clear_buffer_mapped(map_bh);
230 break;
231 }
232 if (page_block == blocks_per_page)
233 break;
234 blocks[page_block] = map_bh->b_blocknr + map_offset +
235 relative_block;
236 page_block++;
237 block_in_file++;
238 }
239 bdev = map_bh->b_bdev;
240 }
241
242 /*
243 * Then do more get_blocks calls until we are done with this page.
244 */
245 map_bh->b_page = page;
246 while (page_block < blocks_per_page) {
247 map_bh->b_state = 0;
248 map_bh->b_size = 0;
249
250 if (block_in_file < last_block) {
251 map_bh->b_size = (last_block-block_in_file) << blkbits;
252 if (get_block(inode, block_in_file, map_bh, 0))
253 goto confused;
254 *first_logical_block = block_in_file;
255 }
256
257 if (!buffer_mapped(map_bh)) {
258 fully_mapped = 0;
259 if (first_hole == blocks_per_page)
260 first_hole = page_block;
261 page_block++;
262 block_in_file++;
263 continue;
264 }
265
266 /* some filesystems will copy data into the page during
267 * the get_block call, in which case we don't want to
268 * read it again. map_buffer_to_page copies the data
269 * we just collected from get_block into the page's buffers
270 * so readpage doesn't have to repeat the get_block call
271 */
272 if (buffer_uptodate(map_bh)) {
273 map_buffer_to_page(page, map_bh, page_block);
274 goto confused;
275 }
276
277 if (first_hole != blocks_per_page)
278 goto confused; /* hole -> non-hole */
279
280 /* Contiguous blocks? */
281 if (page_block && blocks[page_block-1] != map_bh->b_blocknr-1)
282 goto confused;
283 nblocks = map_bh->b_size >> blkbits;
284 for (relative_block = 0; ; relative_block++) {
285 if (relative_block == nblocks) {
286 clear_buffer_mapped(map_bh);
287 break;
288 } else if (page_block == blocks_per_page)
289 break;
290 blocks[page_block] = map_bh->b_blocknr+relative_block;
291 page_block++;
292 block_in_file++;
293 }
294 bdev = map_bh->b_bdev;
295 }
296
297 if (first_hole != blocks_per_page) {
298 zero_user_segment(page, first_hole << blkbits, PAGE_SIZE);
299 if (first_hole == 0) {
300 SetPageUptodate(page);
301 unlock_page(page);
302 goto out;
303 }
304 } else if (fully_mapped) {
305 SetPageMappedToDisk(page);
306 }
307
308 if (fully_mapped && blocks_per_page == 1 && !PageUptodate(page) &&
309 cleancache_get_page(page) == 0) {
310 SetPageUptodate(page);
311 goto confused;
312 }
313
314 /*
315 * This page will go to BIO. Do we need to send this BIO off first?
316 */
317 if (bio && (*last_block_in_bio != blocks[0] - 1))
318 bio = mpage_bio_submit(REQ_OP_READ, 0, bio);
319
320alloc_new:
321 if (bio == NULL) {
322 if (first_hole == blocks_per_page) {
323 if (!bdev_read_page(bdev, blocks[0] << (blkbits - 9),
324 page))
325 goto out;
326 }
327 bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
328 min_t(int, nr_pages, BIO_MAX_PAGES), gfp);
329 if (bio == NULL)
330 goto confused;
331 }
332
333 length = first_hole << blkbits;
334 if (bio_add_page(bio, page, length, 0) < length) {
335 bio = mpage_bio_submit(REQ_OP_READ, 0, bio);
336 goto alloc_new;
337 }
338
339 relative_block = block_in_file - *first_logical_block;
340 nblocks = map_bh->b_size >> blkbits;
341 if ((buffer_boundary(map_bh) && relative_block == nblocks) ||
342 (first_hole != blocks_per_page))
343 bio = mpage_bio_submit(REQ_OP_READ, 0, bio);
344 else
345 *last_block_in_bio = blocks[blocks_per_page - 1];
346out:
347 return bio;
348
349confused:
350 if (bio)
351 bio = mpage_bio_submit(REQ_OP_READ, 0, bio);
352 if (!PageUptodate(page))
353 block_read_full_page(page, get_block);
354 else
355 unlock_page(page);
356 goto out;
357}
358
359/**
360 * mpage_readpages - populate an address space with some pages & start reads against them
361 * @mapping: the address_space
362 * @pages: The address of a list_head which contains the target pages. These
363 * pages have their ->index populated and are otherwise uninitialised.
364 * The page at @pages->prev has the lowest file offset, and reads should be
365 * issued in @pages->prev to @pages->next order.
366 * @nr_pages: The number of pages at *@pages
367 * @get_block: The filesystem's block mapper function.
368 *
369 * This function walks the pages and the blocks within each page, building and
370 * emitting large BIOs.
371 *
372 * If anything unusual happens, such as:
373 *
374 * - encountering a page which has buffers
375 * - encountering a page which has a non-hole after a hole
376 * - encountering a page with non-contiguous blocks
377 *
378 * then this code just gives up and calls the buffer_head-based read function.
379 * It does handle a page which has holes at the end - that is a common case:
380 * the end-of-file on blocksize < PAGE_SIZE setups.
381 *
382 * BH_Boundary explanation:
383 *
384 * There is a problem. The mpage read code assembles several pages, gets all
385 * their disk mappings, and then submits them all. That's fine, but obtaining
386 * the disk mappings may require I/O. Reads of indirect blocks, for example.
387 *
388 * So an mpage read of the first 16 blocks of an ext2 file will cause I/O to be
389 * submitted in the following order:
390 * 12 0 1 2 3 4 5 6 7 8 9 10 11 13 14 15 16
391 *
392 * because the indirect block has to be read to get the mappings of blocks
393 * 13,14,15,16. Obviously, this impacts performance.
394 *
395 * So what we do it to allow the filesystem's get_block() function to set
396 * BH_Boundary when it maps block 11. BH_Boundary says: mapping of the block
397 * after this one will require I/O against a block which is probably close to
398 * this one. So you should push what I/O you have currently accumulated.
399 *
400 * This all causes the disk requests to be issued in the correct order.
401 */
402int
403mpage_readpages(struct address_space *mapping, struct list_head *pages,
404 unsigned nr_pages, get_block_t get_block)
405{
406 struct bio *bio = NULL;
407 unsigned page_idx;
408 sector_t last_block_in_bio = 0;
409 struct buffer_head map_bh;
410 unsigned long first_logical_block = 0;
411 gfp_t gfp = readahead_gfp_mask(mapping);
412
413 map_bh.b_state = 0;
414 map_bh.b_size = 0;
415 for (page_idx = 0; page_idx < nr_pages; page_idx++) {
416 struct page *page = lru_to_page(pages);
417
418 prefetchw(&page->flags);
419 list_del(&page->lru);
420 if (!add_to_page_cache_lru(page, mapping,
421 page->index,
422 gfp)) {
423 bio = do_mpage_readpage(bio, page,
424 nr_pages - page_idx,
425 &last_block_in_bio, &map_bh,
426 &first_logical_block,
427 get_block, gfp);
428 }
429 put_page(page);
430 }
431 BUG_ON(!list_empty(pages));
432 if (bio)
433 mpage_bio_submit(REQ_OP_READ, 0, bio);
434 return 0;
435}
436EXPORT_SYMBOL(mpage_readpages);
437
438/*
439 * This isn't called much at all
440 */
441int mpage_readpage(struct page *page, get_block_t get_block)
442{
443 struct bio *bio = NULL;
444 sector_t last_block_in_bio = 0;
445 struct buffer_head map_bh;
446 unsigned long first_logical_block = 0;
447 gfp_t gfp = mapping_gfp_constraint(page->mapping, GFP_KERNEL);
448
449 map_bh.b_state = 0;
450 map_bh.b_size = 0;
451 bio = do_mpage_readpage(bio, page, 1, &last_block_in_bio,
452 &map_bh, &first_logical_block, get_block, gfp);
453 if (bio)
454 mpage_bio_submit(REQ_OP_READ, 0, bio);
455 return 0;
456}
457EXPORT_SYMBOL(mpage_readpage);
458
459/*
460 * Writing is not so simple.
461 *
462 * If the page has buffers then they will be used for obtaining the disk
463 * mapping. We only support pages which are fully mapped-and-dirty, with a
464 * special case for pages which are unmapped at the end: end-of-file.
465 *
466 * If the page has no buffers (preferred) then the page is mapped here.
467 *
468 * If all blocks are found to be contiguous then the page can go into the
469 * BIO. Otherwise fall back to the mapping's writepage().
470 *
471 * FIXME: This code wants an estimate of how many pages are still to be
472 * written, so it can intelligently allocate a suitably-sized BIO. For now,
473 * just allocate full-size (16-page) BIOs.
474 */
475
476struct mpage_data {
477 struct bio *bio;
478 sector_t last_block_in_bio;
479 get_block_t *get_block;
480 unsigned use_writepage;
481};
482
483/*
484 * We have our BIO, so we can now mark the buffers clean. Make
485 * sure to only clean buffers which we know we'll be writing.
486 */
487static void clean_buffers(struct page *page, unsigned first_unmapped)
488{
489 unsigned buffer_counter = 0;
490 struct buffer_head *bh, *head;
491 if (!page_has_buffers(page))
492 return;
493 head = page_buffers(page);
494 bh = head;
495
496 do {
497 if (buffer_counter++ == first_unmapped)
498 break;
499 clear_buffer_dirty(bh);
500 bh = bh->b_this_page;
501 } while (bh != head);
502
503 /*
504 * we cannot drop the bh if the page is not uptodate or a concurrent
505 * readpage would fail to serialize with the bh and it would read from
506 * disk before we reach the platter.
507 */
508 if (buffer_heads_over_limit && PageUptodate(page))
509 try_to_free_buffers(page);
510}
511
512/*
513 * For situations where we want to clean all buffers attached to a page.
514 * We don't need to calculate how many buffers are attached to the page,
515 * we just need to specify a number larger than the maximum number of buffers.
516 */
517void clean_page_buffers(struct page *page)
518{
519 clean_buffers(page, ~0U);
520}
521
522static int __mpage_writepage(struct page *page, struct writeback_control *wbc,
523 void *data)
524{
525 struct mpage_data *mpd = data;
526 struct bio *bio = mpd->bio;
527 struct address_space *mapping = page->mapping;
528 struct inode *inode = page->mapping->host;
529 const unsigned blkbits = inode->i_blkbits;
530 unsigned long end_index;
531 const unsigned blocks_per_page = PAGE_SIZE >> blkbits;
532 sector_t last_block;
533 sector_t block_in_file;
534 sector_t blocks[MAX_BUF_PER_PAGE];
535 unsigned page_block;
536 unsigned first_unmapped = blocks_per_page;
537 struct block_device *bdev = NULL;
538 int boundary = 0;
539 sector_t boundary_block = 0;
540 struct block_device *boundary_bdev = NULL;
541 int length;
542 struct buffer_head map_bh;
543 loff_t i_size = i_size_read(inode);
544 int ret = 0;
545 int op_flags = (wbc->sync_mode == WB_SYNC_ALL ? WRITE_SYNC : 0);
546
547 if (page_has_buffers(page)) {
548 struct buffer_head *head = page_buffers(page);
549 struct buffer_head *bh = head;
550
551 /* If they're all mapped and dirty, do it */
552 page_block = 0;
553 do {
554 BUG_ON(buffer_locked(bh));
555 if (!buffer_mapped(bh)) {
556 /*
557 * unmapped dirty buffers are created by
558 * __set_page_dirty_buffers -> mmapped data
559 */
560 if (buffer_dirty(bh))
561 goto confused;
562 if (first_unmapped == blocks_per_page)
563 first_unmapped = page_block;
564 continue;
565 }
566
567 if (first_unmapped != blocks_per_page)
568 goto confused; /* hole -> non-hole */
569
570 if (!buffer_dirty(bh) || !buffer_uptodate(bh))
571 goto confused;
572 if (page_block) {
573 if (bh->b_blocknr != blocks[page_block-1] + 1)
574 goto confused;
575 }
576 blocks[page_block++] = bh->b_blocknr;
577 boundary = buffer_boundary(bh);
578 if (boundary) {
579 boundary_block = bh->b_blocknr;
580 boundary_bdev = bh->b_bdev;
581 }
582 bdev = bh->b_bdev;
583 } while ((bh = bh->b_this_page) != head);
584
585 if (first_unmapped)
586 goto page_is_mapped;
587
588 /*
589 * Page has buffers, but they are all unmapped. The page was
590 * created by pagein or read over a hole which was handled by
591 * block_read_full_page(). If this address_space is also
592 * using mpage_readpages then this can rarely happen.
593 */
594 goto confused;
595 }
596
597 /*
598 * The page has no buffers: map it to disk
599 */
600 BUG_ON(!PageUptodate(page));
601 block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
602 last_block = (i_size - 1) >> blkbits;
603 map_bh.b_page = page;
604 for (page_block = 0; page_block < blocks_per_page; ) {
605
606 map_bh.b_state = 0;
607 map_bh.b_size = 1 << blkbits;
608 if (mpd->get_block(inode, block_in_file, &map_bh, 1))
609 goto confused;
610 if (buffer_new(&map_bh))
611 unmap_underlying_metadata(map_bh.b_bdev,
612 map_bh.b_blocknr);
613 if (buffer_boundary(&map_bh)) {
614 boundary_block = map_bh.b_blocknr;
615 boundary_bdev = map_bh.b_bdev;
616 }
617 if (page_block) {
618 if (map_bh.b_blocknr != blocks[page_block-1] + 1)
619 goto confused;
620 }
621 blocks[page_block++] = map_bh.b_blocknr;
622 boundary = buffer_boundary(&map_bh);
623 bdev = map_bh.b_bdev;
624 if (block_in_file == last_block)
625 break;
626 block_in_file++;
627 }
628 BUG_ON(page_block == 0);
629
630 first_unmapped = page_block;
631
632page_is_mapped:
633 end_index = i_size >> PAGE_SHIFT;
634 if (page->index >= end_index) {
635 /*
636 * The page straddles i_size. It must be zeroed out on each
637 * and every writepage invocation because it may be mmapped.
638 * "A file is mapped in multiples of the page size. For a file
639 * that is not a multiple of the page size, the remaining memory
640 * is zeroed when mapped, and writes to that region are not
641 * written out to the file."
642 */
643 unsigned offset = i_size & (PAGE_SIZE - 1);
644
645 if (page->index > end_index || !offset)
646 goto confused;
647 zero_user_segment(page, offset, PAGE_SIZE);
648 }
649
650 /*
651 * This page will go to BIO. Do we need to send this BIO off first?
652 */
653 if (bio && mpd->last_block_in_bio != blocks[0] - 1)
654 bio = mpage_bio_submit(REQ_OP_WRITE, op_flags, bio);
655
656alloc_new:
657 if (bio == NULL) {
658 if (first_unmapped == blocks_per_page) {
659 if (!bdev_write_page(bdev, blocks[0] << (blkbits - 9),
660 page, wbc))
661 goto out;
662 }
663 bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
664 BIO_MAX_PAGES, GFP_NOFS|__GFP_HIGH);
665 if (bio == NULL)
666 goto confused;
667
668 wbc_init_bio(wbc, bio);
669 }
670
671 /*
672 * Must try to add the page before marking the buffer clean or
673 * the confused fail path above (OOM) will be very confused when
674 * it finds all bh marked clean (i.e. it will not write anything)
675 */
676 wbc_account_io(wbc, page, PAGE_SIZE);
677 length = first_unmapped << blkbits;
678 if (bio_add_page(bio, page, length, 0) < length) {
679 bio = mpage_bio_submit(REQ_OP_WRITE, op_flags, bio);
680 goto alloc_new;
681 }
682
683 clean_buffers(page, first_unmapped);
684
685 BUG_ON(PageWriteback(page));
686 set_page_writeback(page);
687 unlock_page(page);
688 if (boundary || (first_unmapped != blocks_per_page)) {
689 bio = mpage_bio_submit(REQ_OP_WRITE, op_flags, bio);
690 if (boundary_block) {
691 write_boundary_block(boundary_bdev,
692 boundary_block, 1 << blkbits);
693 }
694 } else {
695 mpd->last_block_in_bio = blocks[blocks_per_page - 1];
696 }
697 goto out;
698
699confused:
700 if (bio)
701 bio = mpage_bio_submit(REQ_OP_WRITE, op_flags, bio);
702
703 if (mpd->use_writepage) {
704 ret = mapping->a_ops->writepage(page, wbc);
705 } else {
706 ret = -EAGAIN;
707 goto out;
708 }
709 /*
710 * The caller has a ref on the inode, so *mapping is stable
711 */
712 mapping_set_error(mapping, ret);
713out:
714 mpd->bio = bio;
715 return ret;
716}
717
718/**
719 * mpage_writepages - walk the list of dirty pages of the given address space & writepage() all of them
720 * @mapping: address space structure to write
721 * @wbc: subtract the number of written pages from *@wbc->nr_to_write
722 * @get_block: the filesystem's block mapper function.
723 * If this is NULL then use a_ops->writepage. Otherwise, go
724 * direct-to-BIO.
725 *
726 * This is a library function, which implements the writepages()
727 * address_space_operation.
728 *
729 * If a page is already under I/O, generic_writepages() skips it, even
730 * if it's dirty. This is desirable behaviour for memory-cleaning writeback,
731 * but it is INCORRECT for data-integrity system calls such as fsync(). fsync()
732 * and msync() need to guarantee that all the data which was dirty at the time
733 * the call was made get new I/O started against them. If wbc->sync_mode is
734 * WB_SYNC_ALL then we were called for data integrity and we must wait for
735 * existing IO to complete.
736 */
737int
738mpage_writepages(struct address_space *mapping,
739 struct writeback_control *wbc, get_block_t get_block)
740{
741 struct blk_plug plug;
742 int ret;
743
744 blk_start_plug(&plug);
745
746 if (!get_block)
747 ret = generic_writepages(mapping, wbc);
748 else {
749 struct mpage_data mpd = {
750 .bio = NULL,
751 .last_block_in_bio = 0,
752 .get_block = get_block,
753 .use_writepage = 1,
754 };
755
756 ret = write_cache_pages(mapping, wbc, __mpage_writepage, &mpd);
757 if (mpd.bio) {
758 int op_flags = (wbc->sync_mode == WB_SYNC_ALL ?
759 WRITE_SYNC : 0);
760 mpage_bio_submit(REQ_OP_WRITE, op_flags, mpd.bio);
761 }
762 }
763 blk_finish_plug(&plug);
764 return ret;
765}
766EXPORT_SYMBOL(mpage_writepages);
767
768int mpage_writepage(struct page *page, get_block_t get_block,
769 struct writeback_control *wbc)
770{
771 struct mpage_data mpd = {
772 .bio = NULL,
773 .last_block_in_bio = 0,
774 .get_block = get_block,
775 .use_writepage = 0,
776 };
777 int ret = __mpage_writepage(page, wbc, &mpd);
778 if (mpd.bio) {
779 int op_flags = (wbc->sync_mode == WB_SYNC_ALL ?
780 WRITE_SYNC : 0);
781 mpage_bio_submit(REQ_OP_WRITE, op_flags, mpd.bio);
782 }
783 return ret;
784}
785EXPORT_SYMBOL(mpage_writepage);
786
generated by cgit at 2024-05-18 11:15:42 (GMT)