Commit 26ac1073 authored Feb 18, 2015 by NeilBrown

md/raid5: Fix livelock when array is both resyncing and degraded.



Commit a7854487:
  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: a7854487
Cc: stable@vger.kernel.org (v3.7+)

parent f04ebb0b

drivers/md/raid5.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -3170,7 +3170,8 @@ static void handle_stripe_dirtying(struct r5conf *conf,
		* generate correct data from the parity.
		*/
		if (conf->max_degraded == 2 \|\|
		(recovery_cp < MaxSector && sh->sector >= recovery_cp)) {
		(recovery_cp < MaxSector && sh->sector >= recovery_cp &&
		s->failed == 0)) {
		/* Calculate the real rcw later - for now make it
		* look like rcw is cheaper
		*/

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