From 3329f828be213a7dce07c228d7bc494a277a56fa Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Wed, 13 Aug 2014 09:57:07 +1000 Subject: [PATCH] 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 (backported from commit 9c4bdf697c39805078392d5ddbbba5ae5680e0dd) BugLink: http://bugs.launchpad.net/bugs/1364091 Signed-off-by: Seth Forshee --- drivers/md/raid5.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index 883215d..ed5ea2c 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -3091,6 +3091,8 @@ static void handle_stripe5(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 && s.failed == 0)) set_bit(STRIPE_INSYNC, &sh->state); @@ -3378,6 +3380,8 @@ static void handle_stripe6(struct stripe_head *sh) pr_debug("Writing block %d\n", i); BUG_ON(!test_bit(R5_UPTODATE, &dev->flags)); set_bit(R5_Wantwrite, &dev->flags); + if (s.failed > 1) + continue; if (!test_bit(R5_Insync, &dev->flags) || ((i == sh->pd_idx || i == qd_idx) && s.failed == 0)) -- 1.9.1