md/raid6: Set R5_ReadError when there is read failure on parity disk

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>

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 3de4e13..59cafaf 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2558,7 +2558,9 @@ static void raid5_end_read_request(struct bio * bi)
                    && !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