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Date: Mon, 15 Sep 2014 12:26:05 -0700 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, NeilBrown <neilb@...e.de> Subject: [PATCH 3.16 126/158] md/raid5: avoid livelock caused by non-aligned writes. 3.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: NeilBrown <neilb@...e.de> 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@...e.de> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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