[PATCH v2] Btrfs: enable repair during read for raid56 profile
From: Liu Bo <hidden>
Date: 2017-03-29 17:55:15
Subsystem:
btrfs file system, filesystems (vfs and infrastructure), the rest · Maintainers:
Chris Mason, David Sterba, Alexander Viro, Christian Brauner, Linus Torvalds
Now that scrub can fix data errors with the help of parity for raid56 profile, repair during read is able to as well. Although the mirror num in raid56 scenario has different meanings, i.e. 0 or 1: read data directly
1: do recover with parity,
it could be fit into how we repair bad block during read. The trick is to use BTRFS_MAP_READ instead of BTRFS_MAP_WRITE to get the device and position on it. Cc: David Sterba <redacted> Signed-off-by: Liu Bo <redacted> --- v2: Fix typo and add comments for why BTRFS_MAP_READ is used. fs/btrfs/extent_io.c | 40 +++++++++++++++++++++++++++------------- 1 file changed, 27 insertions(+), 13 deletions(-)
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index d39a11c..7241f94 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c@@ -2009,10 +2009,6 @@ int repair_io_failure(struct btrfs_inode *inode, u64 start, u64 length, ASSERT(!(fs_info->sb->s_flags & MS_RDONLY)); BUG_ON(!mirror_num); - /* we can't repair anything in raid56 yet */ - if (btrfs_is_parity_mirror(map_tree, logical, length, mirror_num)) - return 0; - bio = btrfs_io_bio_alloc(GFP_NOFS, 1); if (!bio) return -EIO;
@@ -2025,17 +2021,35 @@ int repair_io_failure(struct btrfs_inode *inode, u64 start, u64 length, * read repair operation. */ btrfs_bio_counter_inc_blocked(fs_info); - ret = btrfs_map_block(fs_info, BTRFS_MAP_WRITE, logical, - &map_length, &bbio, mirror_num); - if (ret) { - btrfs_bio_counter_dec(fs_info); - bio_put(bio); - return -EIO; + if (btrfs_is_parity_mirror(map_tree, logical, length, mirror_num)) { + /* + * Note that we don't use BTRFS_MAP_WRITE because it's supposed + * to update all raid stripes, but here we just want to correct + * bad stripe, thus BTRFS_MAP_READ is abused to only get the bad + * stripe's dev and sector. + */ + ret = btrfs_map_block(fs_info, BTRFS_MAP_READ, logical, + &map_length, &bbio, 0); + if (ret) { + btrfs_bio_counter_dec(fs_info); + bio_put(bio); + return -EIO; + } + ASSERT(bbio->mirror_num == 1); + } else { + ret = btrfs_map_block(fs_info, BTRFS_MAP_WRITE, logical, + &map_length, &bbio, mirror_num); + if (ret) { + btrfs_bio_counter_dec(fs_info); + bio_put(bio); + return -EIO; + } + BUG_ON(mirror_num != bbio->mirror_num); } - BUG_ON(mirror_num != bbio->mirror_num); - sector = bbio->stripes[mirror_num-1].physical >> 9; + + sector = bbio->stripes[bbio->mirror_num - 1].physical >> 9; bio->bi_iter.bi_sector = sector; - dev = bbio->stripes[mirror_num-1].dev; + dev = bbio->stripes[bbio->mirror_num - 1].dev; btrfs_put_bbio(bbio); if (!dev || !dev->bdev || !dev->writeable) { btrfs_bio_counter_dec(fs_info);
--
2.5.5