md/raid5: Fix livelock when array is both resyncing and degraded.
authorNeilBrown <neilb@suse.de>
Wed, 18 Feb 2015 00:35:14 +0000 (11:35 +1100)
committerNeilBrown <neilb@suse.de>
Wed, 18 Feb 2015 00:35:14 +0000 (11:35 +1100)
commit26ac107378c4742978216be1005b7291b799c7b2
tree1ec992f01a3873c7c033c6b41633cbdeb5dec0dc
parentf04ebb0be74283b32f539c7f6b84d5cfcaa0ead3
md/raid5: Fix livelock when array is both resyncing and degraded.

Commit a7854487cd7128a30a7f4f5259de9f67d5efb95f:
  md: When RAID5 is dirty, force reconstruct-write instead of read-modify-write.

Causes an RCW cycle to be forced even when the array is degraded.
A degraded array cannot support RCW as that requires reading all data
blocks, and one may be missing.

Forcing an RCW when it is not possible causes a live-lock and the code
spins, repeatedly deciding to do something that cannot succeed.

So change the condition to only force RCW on non-degraded arrays.

Reported-by: Manibalan P <pmanibalan@amiindia.co.in>
Bisected-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Tested-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Fixes: a7854487cd7128a30a7f4f5259de9f67d5efb95f
Cc: stable@vger.kernel.org (v3.7+)
drivers/md/raid5.c