From: Nigel Croxon <ncro...@redhat.com>

commit b2176a1dfb518d870ee073445d27055fea64dfb8 upstream.

The problem is that any 'uptodate' vs 'disks' check is not precise
in this path. Put a "WARN_ON(!test_bit(R5_UPTODATE, &dev->flags)" on the
device that might try to kick off writes and then skip the action.
Better to prevent the raid driver from taking unexpected action *and* keep
the system alive vs killing the machine with BUG_ON.

Note: fixed warning reported by kbuild test robot <l...@intel.com>

Signed-off-by: Dan Williams <dan.j.willi...@intel.com>
Signed-off-by: Nigel Croxon <ncro...@redhat.com>
Signed-off-by: Song Liu <songliubrav...@fb.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/md/raid5.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3861,7 +3861,7 @@ static void handle_parity_checks6(struct
                /* now write out any block on a failed drive,
                 * or P or Q if they were recomputed
                 */
-               BUG_ON(s->uptodate < disks - 1); /* We don't need Q to recover 
*/
+               dev = NULL;
                if (s->failed == 2) {
                        dev = &sh->dev[s->failed_num[1]];
                        s->locked++;
@@ -3886,6 +3886,14 @@ static void handle_parity_checks6(struct
                        set_bit(R5_LOCKED, &dev->flags);
                        set_bit(R5_Wantwrite, &dev->flags);
                }
+               if (WARN_ONCE(dev && !test_bit(R5_UPTODATE, &dev->flags),
+                             "%s: disk%td not up to date\n",
+                             mdname(conf->mddev),
+                             dev - (struct r5dev *) &sh->dev)) {
+                       clear_bit(R5_LOCKED, &dev->flags);
+                       clear_bit(R5_Wantwrite, &dev->flags);
+                       s->locked--;
+               }
                clear_bit(STRIPE_DEGRADED, &sh->state);
 
                set_bit(STRIPE_INSYNC, &sh->state);


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