The patch below does not apply to the 3.10-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 108cef3aa41669610e1836fe638812dd067d72de Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@xxxxxxx>
Date: Wed, 3 Dec 2014 16:07:58 +1100
Subject: [PATCH] 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@xxxxxxxxxxxxxxx (v3.7+)
Fixes: a7854487cd7128a30a7f4f5259de9f67d5efb95f
Reported-by: Henry Cai <henryplusplus@xxxxxxxxx>
Signed-off-by: NeilBrown <neilb@xxxxxxx>
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
--
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