diff options
Diffstat (limited to 'fs/btrfs/extent_io.c')
-rw-r--r-- | fs/btrfs/extent_io.c | 67 |
1 files changed, 60 insertions, 7 deletions
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 05937a8..9a837a8 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -2444,7 +2444,8 @@ static int submit_extent_page(int rw, struct extent_io_tree *tree, bio_end_io_t end_io_func, int mirror_num, unsigned long prev_bio_flags, - unsigned long bio_flags) + unsigned long bio_flags, + bool force_bio_submit) { int ret = 0; struct bio *bio; @@ -2463,6 +2464,7 @@ static int submit_extent_page(int rw, struct extent_io_tree *tree, sector; if (prev_bio_flags != bio_flags || !contig || + force_bio_submit || (tree->ops && tree->ops->merge_bio_hook && tree->ops->merge_bio_hook(page, offset, page_size, bio, bio_flags)) || @@ -2519,7 +2521,8 @@ static int __extent_read_full_page(struct extent_io_tree *tree, struct page *page, get_extent_t *get_extent, struct bio **bio, int mirror_num, - unsigned long *bio_flags) + unsigned long *bio_flags, + u64 *prev_em_start) { struct inode *inode = page->mapping->host; u64 start = (u64)page->index << PAGE_CACHE_SHIFT; @@ -2575,6 +2578,8 @@ static int __extent_read_full_page(struct extent_io_tree *tree, } } while (cur <= end) { + bool force_bio_submit = false; + if (cur >= last_byte) { char *userpage; struct extent_state *cached = NULL; @@ -2621,6 +2626,49 @@ static int __extent_read_full_page(struct extent_io_tree *tree, block_start = em->block_start; if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags)) block_start = EXTENT_MAP_HOLE; + + /* + * If we have a file range that points to a compressed extent + * and it's followed by a consecutive file range that points to + * to the same compressed extent (possibly with a different + * offset and/or length, so it either points to the whole extent + * or only part of it), we must make sure we do not submit a + * single bio to populate the pages for the 2 ranges because + * this makes the compressed extent read zero out the pages + * belonging to the 2nd range. Imagine the following scenario: + * + * File layout + * [0 - 8K] [8K - 24K] + * | | + * | | + * points to extent X, points to extent X, + * offset 4K, length of 8K offset 0, length 16K + * + * [extent X, compressed length = 4K uncompressed length = 16K] + * + * If the bio to read the compressed extent covers both ranges, + * it will decompress extent X into the pages belonging to the + * first range and then it will stop, zeroing out the remaining + * pages that belong to the other range that points to extent X. + * So here we make sure we submit 2 bios, one for the first + * range and another one for the third range. Both will target + * the same physical extent from disk, but we can't currently + * make the compressed bio endio callback populate the pages + * for both ranges because each compressed bio is tightly + * coupled with a single extent map, and each range can have + * an extent map with a different offset value relative to the + * uncompressed data of our extent and different lengths. This + * is a corner case so we prioritize correctness over + * non-optimal behavior (submitting 2 bios for the same extent). + */ + if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags) && + prev_em_start && *prev_em_start != (u64)-1 && + *prev_em_start != em->orig_start) + force_bio_submit = true; + + if (prev_em_start) + *prev_em_start = em->orig_start; + free_extent_map(em); em = NULL; @@ -2675,7 +2723,8 @@ static int __extent_read_full_page(struct extent_io_tree *tree, bdev, bio, pnr, end_bio_extent_readpage, mirror_num, *bio_flags, - this_bio_flag); + this_bio_flag, + force_bio_submit); nr++; *bio_flags = this_bio_flag; } @@ -2701,7 +2750,7 @@ int extent_read_full_page(struct extent_io_tree *tree, struct page *page, int ret; ret = __extent_read_full_page(tree, page, get_extent, &bio, mirror_num, - &bio_flags); + &bio_flags, NULL); if (bio) ret = submit_one_bio(READ, bio, mirror_num, bio_flags); return ret; @@ -2960,7 +3009,7 @@ static int __extent_writepage(struct page *page, struct writeback_control *wbc, sector, iosize, pg_offset, bdev, &epd->bio, max_nr, end_bio_extent_writepage, - 0, 0, 0); + 0, 0, 0, false); if (ret) SetPageError(page); } @@ -3219,6 +3268,7 @@ int extent_readpages(struct extent_io_tree *tree, struct bio *bio = NULL; unsigned page_idx; unsigned long bio_flags = 0; + u64 prev_em_start = (u64)-1; for (page_idx = 0; page_idx < nr_pages; page_idx++) { struct page *page = list_entry(pages->prev, struct page, lru); @@ -3228,7 +3278,8 @@ int extent_readpages(struct extent_io_tree *tree, if (!add_to_page_cache_lru(page, mapping, page->index, GFP_NOFS)) { __extent_read_full_page(tree, page, get_extent, - &bio, 0, &bio_flags); + &bio, 0, &bio_flags, + &prev_em_start); } page_cache_release(page); } @@ -3998,6 +4049,7 @@ int read_extent_buffer_pages(struct extent_io_tree *tree, unsigned long num_pages; struct bio *bio = NULL; unsigned long bio_flags = 0; + u64 prev_em_start = (u64)-1; if (test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags)) return 0; @@ -4053,7 +4105,8 @@ int read_extent_buffer_pages(struct extent_io_tree *tree, ClearPageError(page); err = __extent_read_full_page(tree, page, get_extent, &bio, - mirror_num, &bio_flags); + mirror_num, &bio_flags, + &prev_em_start); if (err) ret = err; } else { |