MD: fix invalid stored role for a disk

If we change the number of array's device after device is removed from array,
then add the device back to array, we can see that device is added as active
role instead of spare which we expected.

Please see the below link for details:
https://marc.info/?l=linux-raid&m=153736982015076&w=2

This is caused by that we prefer to use device's previous role which is
recorded by saved_raid_disk, but we should respect the new number of
conf->raid_disks since it could be changed after device is removed.

Reported-by: Gioh Kim <gi-oh.kim@profitbricks.com>
Tested-by: Gioh Kim <gi-oh.kim@profitbricks.com>
Acked-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 63ceabb4e020f656313fabff5e25e3ba593a8786..a25ebf81b266ae4d1f46104b276e44762fc406b8 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1774,6 +1774,10 @@ static int super_1_validate(struct mddev *mddev, struct md_rdev *rdev)
                        } else
                                set_bit(In_sync, &rdev->flags);
                        rdev->raid_disk = role;
+                       if (role >= mddev->raid_disks) {
+                               rdev->saved_raid_disk = -1;
+                               rdev->raid_disk = -1;
+                       }
                        break;
                }
                if (sb->devflags & WriteMostly1)