Support adding a spare to a live md array with external metadata.

i.e. extend the 'md/dev-XXX/slot' attribute so that you can
tell a device to fill an vacant slot in an and md array.

Signed-off-by: Neil Brown <neilb@suse.de>

1 files changed, 8 insertions, 2 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 214b44122822..002f33b1ae00 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -4607,21 +4607,27 @@ static int raid5_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
         int found = 0;
         int disk;
         struct disk_info *p;
+        int first = 0;
+        int last = conf->raid_disks - 1;
 
         if (mddev->degraded > conf->max_degraded)
                 /* no point adding a device */
                 return 0;
 
+        if (rdev->raid_disk >= 0)
+                first = last = rdev->raid_disk;
+
         /*
          * find the disk ... but prefer rdev->saved_raid_disk
          * if possible.
          */
         if (rdev->saved_raid_disk >= 0 &&
+            rdev->saved_raid_disk >= first &&
             conf->disks[rdev->saved_raid_disk].rdev == NULL)
                 disk = rdev->saved_raid_disk;
         else
-                disk = 0;
-        for ( ; disk < conf->raid_disks; disk++)
+                disk = first;
+        for ( ; disk <= last ; disk++)
                 if ((p=conf->disks + disk)->rdev == NULL) {
                         clear_bit(In_sync, &rdev->flags);
                         rdev->raid_disk = disk;