This is a note to let you know that I've just added the patch titled
md/raid5: avoid livelock caused by non-aligned writes.
to the 3.16-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
md-raid5-avoid-livelock-caused-by-non-aligned-writes.patch
and it can be found in the queue-3.16 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From a40687ff73a5b14909d6aa522f7d778b158911c5 Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@xxxxxxx>
Date: Wed, 13 Aug 2014 09:48:45 +1000
Subject: md/raid5: avoid livelock caused by non-aligned writes.
From: NeilBrown <neilb@xxxxxxx>
commit a40687ff73a5b14909d6aa522f7d778b158911c5 upstream.
If a stripe in a raid6 array received a write to each data block while
the array is degraded, and if any of these writes to a missing device
are not page-aligned, then a live-lock happens.
In this case the P and Q blocks need to be read so that the part of
the missing block which is *not* being updated by the write can be
constructed. Due to a logic error, these blocks are not loaded, so
the update cannot proceed and the stripe is 'handled' repeatedly in an
infinite loop.
This bug is unlikely as most writes are page aligned. However as it
can lead to a livelock it is suitable for -stable. It was introduced
in 3.16.
Fixed: 67f455486d2ea20b2d94d6adf5b9b783d079e321
Signed-off-by: NeilBrown <neilb@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/md/raid5.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2922,7 +2922,7 @@ static int fetch_block(struct stripe_hea
(!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 < sh->raid_conf->raid_disks - 2 &&
+ s->to_write - s->non_overwrite < sh->raid_conf->raid_disks - 2 &&
(!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
Patches currently in stable-queue which might be from neilb@xxxxxxx are
queue-3.16/md-raid10-fix-memory-leak-when-reshaping-a-raid10.patch
queue-3.16/md-raid6-avoid-data-corruption-during-recovery-of-double-degraded-raid6.patch
queue-3.16/md-raid1-raid10-always-abort-recover-on-write-error.patch
queue-3.16/md-raid10-fix-memory-leak-when-raid10-reshape-completes.patch
queue-3.16/md-raid5-avoid-livelock-caused-by-non-aligned-writes.patch
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