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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Xiao Ni <xni@redhat.com>,
        Song Liu <songliubraving@fb.com>
Subject: [PATCH 4.4 88/99] md/raid6: Set R5_ReadError when there is read failure on parity disk
Date:   Thu,  3 Oct 2019 17:53:51 +0200
Message-Id: <20191003154338.656585846@linuxfoundation.org>
In-Reply-To: <20191003154252.297991283@linuxfoundation.org>
References: <20191003154252.297991283@linuxfoundation.org>
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From: Xiao Ni <xni@redhat.com>

commit 143f6e733b73051cd22dcb80951c6c929da413ce upstream.

7471fb77ce4d ("md/raid6: Fix anomily when recovering a single device in
RAID6.") avoids rereading P when it can be computed from other members.
However, this misses the chance to re-write the right data to P. This
patch sets R5_ReadError if the re-read fails.

Also, when re-read is skipped, we also missed the chance to reset
rdev->read_errors to 0. It can fail the disk when there are many read
errors on P member disk (other disks don't have read error)

V2: upper layer read request don't read parity/Q data. So there is no
need to consider such situation.

This is Reported-by: kbuild test robot <lkp@intel.com>

Fixes: 7471fb77ce4d ("md/raid6: Fix anomily when recovering a single device in RAID6.")
Cc: <stable@vger.kernel.org> #4.4+
Signed-off-by: Xiao Ni <xni@redhat.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/md/raid5.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2394,7 +2394,9 @@ static void raid5_end_read_request(struc
 		    && !test_bit(R5_ReadNoMerge, &sh->dev[i].flags))
 			retry = 1;
 		if (retry)
-			if (test_bit(R5_ReadNoMerge, &sh->dev[i].flags)) {
+			if (sh->qd_idx >= 0 && sh->pd_idx == i)
+				set_bit(R5_ReadError, &sh->dev[i].flags);
+			else if (test_bit(R5_ReadNoMerge, &sh->dev[i].flags)) {
 				set_bit(R5_ReadError, &sh->dev[i].flags);
 				clear_bit(R5_ReadNoMerge, &sh->dev[i].flags);
 			} else