MD: raid5 do not set fullsync

Add check to determine if a device needs full resync or if partial resync will do

RAID 5 was assuming that if a device was not In_sync, it must undergo a full
resync.  We add a check to see if 'saved_raid_disk' is the same as 'raid_disk'.
If it is, we can safely skip the full resync and rely on the bitmap for
partial recovery instead.  This is the legitimate purpose of 'saved_raid_disk',
from md.h:
int saved_raid_disk;            /* role that device used to have in the
                                 * array and could again if we did a partial
                                 * resync from the bitmap
                                 */

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 346e69bfdab3f8b0b744f6b239c93ea0f3f099e2..f9d2fbc64977eb0eea74e4e10f1a9125b4bef6ea 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -4858,7 +4858,7 @@ static raid5_conf_t *setup_conf(mddev_t *mddev)
                        printk(KERN_INFO "md/raid:%s: device %s operational as raid"
                               " disk %d\n",
                               mdname(mddev), bdevname(rdev->bdev, b), raid_disk);
-               } else
+               } else if (rdev->saved_raid_disk != raid_disk)
                        /* Cannot rely on bitmap to complete recovery */
                        conf->fullsync = 1;
        }