| Message ID | 20180113010702.25612-2-bo.li.liu@oracle.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Jan 12, 2018 at 06:07:02PM -0700, Liu Bo wrote: > Since raid6 recover tries all possible combinations of failed stripes, > > - when raid6 rebuild algorithm is used, i.e. raid6_datap_recov() and > raid6_2data_recov(), it may change the in-memory content of failed > stripes, if such a raid bio is cached, a later raid write rmw or recover > can steal @stripe_pages from it instead of reading from disks, such that > it carries the wrong content to do write rmw or recovery and ends up > with corruption or recovery failures. > > - when raid5 rebuild algorithm is used, i.e. xor, raid bio can be cached > because the only failed stripe which contains @rbio->bio_pages gets > modified, others remain the same so that their in-memory content is > consistent with their on-disk content. > > This adds a check to skip caching rbio if using raid6 recover. > > Signed-off-by: Liu Bo <bo.li.liu@oracle.com> Added to 4.16 queue, thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c index 56ae5bd..4d56f24 100644 --- a/fs/btrfs/raid56.c +++ b/fs/btrfs/raid56.c @@ -1975,7 +1975,22 @@ static void __raid_recover_end_io(struct btrfs_raid_bio *rbio) cleanup_io: if (rbio->operation == BTRFS_RBIO_READ_REBUILD) { - if (err == BLK_STS_OK) + /* + * - In case of two failures, where rbio->failb != -1: + * + * Do not cache this rbio since the above read reconstruction + * (raid6_datap_recov() or raid6_2data_recov()) may have + * changed some content of stripes which are not identical to + * on-disk content any more, otherwise, a later write/recover + * may steal stripe_pages from this rbio and end up with + * corruptions or rebuild failures. + * + * - In case of single failure, where rbio->failb == -1: + * + * Cache this rbio iff the above read reconstruction is + * excuted without problems. + */ + if (err == BLK_STS_OK && rbio->failb < 0) cache_rbio_pages(rbio); else clear_bit(RBIO_CACHE_READY_BIT, &rbio->flags);
Since raid6 recover tries all possible combinations of failed stripes, - when raid6 rebuild algorithm is used, i.e. raid6_datap_recov() and raid6_2data_recov(), it may change the in-memory content of failed stripes, if such a raid bio is cached, a later raid write rmw or recover can steal @stripe_pages from it instead of reading from disks, such that it carries the wrong content to do write rmw or recovery and ends up with corruption or recovery failures. - when raid5 rebuild algorithm is used, i.e. xor, raid bio can be cached because the only failed stripe which contains @rbio->bio_pages gets modified, others remain the same so that their in-memory content is consistent with their on-disk content. This adds a check to skip caching rbio if using raid6 recover. Signed-off-by: Liu Bo <bo.li.liu@oracle.com> --- fs/btrfs/raid56.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-)