From a40687ff73a5b14909d6aa522f7d778b158911c5 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Wed, 13 Aug 2014 09:48:45 +1000 Subject: md/raid5: avoid livelock caused by non-aligned writes. 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. Cc: stable@vger.kernel.org (v3.16) Fixed: 67f455486d2ea20b2d94d6adf5b9b783d079e321 Signed-off-by: NeilBrown --- drivers/md/raid5.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/md/raid5.c') diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index 6234b2e8458..6b2d615d109 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -2922,7 +2922,7 @@ static int fetch_block(struct stripe_head *sh, struct stripe_head_state *s, (!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 -- cgit v1.2.3-70-g09d2 From 9c4bdf697c39805078392d5ddbbba5ae5680e0dd Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Wed, 13 Aug 2014 09:57:07 +1000 Subject: md/raid6: avoid data corruption during recovery of double-degraded RAID6 During recovery of a double-degraded RAID6 it is possible for some blocks not to be recovered properly, leading to corruption. If a write happens to one block in a stripe that would be written to a missing device, and at the same time that stripe is recovering data to the other missing device, then that recovered data may not be written. This patch skips, in the double-degraded case, an optimisation that is only safe for single-degraded arrays. Bug was introduced in 2.6.32 and fix is suitable for any kernel since then. In an older kernel with separate handle_stripe5() and handle_stripe6() functions the patch must change handle_stripe6(). Cc: stable@vger.kernel.org (2.6.32+) Fixes: 6c0069c0ae9659e3a91b68eaed06a5c6c37f45c8 Cc: Yuri Tikhonov Cc: Dan Williams Reported-by: "Manibalan P" Tested-by: "Manibalan P" Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1090423 Signed-off-by: NeilBrown Acked-by: Dan Williams --- drivers/md/raid5.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers/md/raid5.c') diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index 6b2d615d109..183588b11fc 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -3817,6 +3817,8 @@ static void handle_stripe(struct stripe_head *sh) set_bit(R5_Wantwrite, &dev->flags); if (prexor) continue; + if (s.failed > 1) + continue; if (!test_bit(R5_Insync, &dev->flags) || ((i == sh->pd_idx || i == sh->qd_idx) && s.failed == 0)) -- cgit v1.2.3-70-g09d2