From: NeilBrown Date: Wed, 3 Dec 2014 05:07:58 +0000 (+1100) Subject: md/raid5: fetch_block must fetch all the blocks handle_stripe_dirtying wants. X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=108cef3aa41669610e1836fe638812dd067d72de;p=deliverable%2Flinux.git md/raid5: fetch_block must fetch all the blocks handle_stripe_dirtying wants. It is critical that fetch_block() and handle_stripe_dirtying() are consistent in their analysis of what needs to be loaded. Otherwise raid5 can wait forever for a block that won't be loaded. Currently when writing to a RAID5 that is resyncing, to a location beyond the resync offset, handle_stripe_dirtying chooses a reconstruct-write cycle, but fetch_block() assumes a read-modify-write, and a lockup can happen. So treat that case just like RAID6, just as we do in handle_stripe_dirtying. RAID6 always does reconstruct-write. This bug was introduced when the behaviour of handle_stripe_dirtying was changed in 3.7, so the patch is suitable for any kernel since, though it will need careful merging for some versions. Cc: stable@vger.kernel.org (v3.7+) Fixes: a7854487cd7128a30a7f4f5259de9f67d5efb95f Reported-by: Henry Cai Signed-off-by: NeilBrown --- diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index 9c66e5997fc8..c1b0d52bfcb0 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -2917,8 +2917,11 @@ static int fetch_block(struct stripe_head *sh, struct stripe_head_state *s, (sh->raid_conf->level <= 5 && s->failed && fdev[0]->towrite && (!test_bit(R5_Insync, &dev->flags) || test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) && !test_bit(R5_OVERWRITE, &fdev[0]->flags)) || - (sh->raid_conf->level == 6 && s->failed && s->to_write && - s->to_write - s->non_overwrite < sh->raid_conf->raid_disks - 2 && + ((sh->raid_conf->level == 6 || + sh->sector >= sh->raid_conf->mddev->recovery_cp) + && s->failed && s->to_write && + (s->to_write - s->non_overwrite < + sh->raid_conf->raid_disks - sh->raid_conf->max_degraded) && (!test_bit(R5_Insync, &dev->flags) || test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))))) { /* we would like to get this block, possibly by computing it, * otherwise read it if the backing disk is insync