4.14-stable review patch. If anyone has any objections, please let me know.
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From: Liu Bo bo.li.liu@oracle.com
[ Upstream commit 762221f095e3932669093466aaf4b85ed9ad2ac1 ]
The raid6 corruption is that, suppose that all disks can be read without problems and if the content that was read out doesn't match its checksum, currently for raid6 btrfs at most retries twice,
- the 1st retry is to rebuild with all other stripes, it'll eventually be a raid5 xor rebuild, - if the 1st fails, the 2nd retry will deliberately fail parity p so that it will do raid6 style rebuild,
however, the chances are that another non-parity stripe content also has something corrupted, so that the above retries are not able to return correct content.
We've fixed normal reads to rebuild raid6 correctly with more retries in Patch "Btrfs: make raid6 rebuild retry more"[1], this is to fix scrub to do the exactly same rebuild process.
[1]: https://patchwork.kernel.org/patch/10091755/
Signed-off-by: Liu Bo bo.li.liu@oracle.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/raid56.c | 18 ++++++++++++++---- fs/btrfs/volumes.c | 9 ++++++++- 2 files changed, 22 insertions(+), 5 deletions(-)
--- a/fs/btrfs/raid56.c +++ b/fs/btrfs/raid56.c @@ -2159,11 +2159,21 @@ int raid56_parity_recover(struct btrfs_f }
/* - * reconstruct from the q stripe if they are - * asking for mirror 3 + * Loop retry: + * for 'mirror == 2', reconstruct from all other stripes. + * for 'mirror_num > 2', select a stripe to fail on every retry. */ - if (mirror_num == 3) - rbio->failb = rbio->real_stripes - 2; + if (mirror_num > 2) { + /* + * 'mirror == 3' is to fail the p stripe and + * reconstruct from the q stripe. 'mirror > 3' is to + * fail a data stripe and reconstruct from p+q stripe. + */ + rbio->failb = rbio->real_stripes - (mirror_num - 1); + ASSERT(rbio->failb > 0); + if (rbio->failb <= rbio->faila) + rbio->failb--; + }
ret = lock_stripe_add(rbio);
--- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -5101,7 +5101,14 @@ int btrfs_num_copies(struct btrfs_fs_inf else if (map->type & BTRFS_BLOCK_GROUP_RAID5) ret = 2; else if (map->type & BTRFS_BLOCK_GROUP_RAID6) - ret = 3; + /* + * There could be two corrupted data stripes, we need + * to loop retry in order to rebuild the correct data. + * + * Fail a stripe at a time on every retry except the + * stripe under reconstruction. + */ + ret = map->num_stripes; else ret = 1; free_extent_map(em);