1 files changed, 34 insertions, 9 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index e2782a04012d..00788c56276f 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1891,20 +1891,44 @@ static ssize_t
 slot_store(mdk_rdev_t *rdev, const char *buf, size_t len)
 {
         char *e;
+        int err;
+        char nm[20];
         int slot = simple_strtoul(buf, &e, 10);
         if (strncmp(buf, "none", 4)==0)
                 slot = -1;
         else if (e==buf || (*e && *e!= '\n'))
                 return -EINVAL;
-        if (rdev->mddev->pers)
-                /* Cannot set slot in active array (yet) */
-                return -EBUSY;
-        if (slot >= rdev->mddev->raid_disks)
-                return -ENOSPC;
-        rdev->raid_disk = slot;
-        /* assume it is working */
-        rdev->flags = 0;
-        set_bit(In_sync, &rdev->flags);
+        if (rdev->mddev->pers) {
+                /* Setting 'slot' on an active array requires also
+                 * updating the 'rd%d' link, and communicating
+                 * with the personality with ->hot_*_disk.
+                 * For now we only support removing
+                 * failed/spare devices.  This normally happens automatically,
+                 * but not when the metadata is externally managed.
+                 */
+                if (slot != -1)
+                        return -EBUSY;
+                if (rdev->raid_disk == -1)
+                        return -EEXIST;
+                /* personality does all needed checks */
+                if (rdev->mddev->pers->hot_add_disk == NULL)
+                        return -EINVAL;
+                err = rdev->mddev->pers->
+                        hot_remove_disk(rdev->mddev, rdev->raid_disk);
+                if (err)
+                        return err;
+                sprintf(nm, "rd%d", rdev->raid_disk);
+                sysfs_remove_link(&rdev->mddev->kobj, nm);
+                set_bit(MD_RECOVERY_NEEDED, &rdev->mddev->recovery);
+                md_wakeup_thread(rdev->mddev->thread);
+        } else {
+                if (slot >= rdev->mddev->raid_disks)
+                        return -ENOSPC;
+                rdev->raid_disk = slot;
+                /* assume it is working */
+                rdev->flags = 0;
+                set_bit(In_sync, &rdev->flags);
+        }
         return len;
 }
 
@@ -5549,6 +5573,7 @@ static int remove_and_add_spares(mddev_t *mddev)
 
         ITERATE_RDEV(mddev,rdev,rtmp)
                 if (rdev->raid_disk >= 0 &&
+                    !mddev->external &&
                     (test_bit(Faulty, &rdev->flags) ||
                      ! test_bit(In_sync, &rdev->flags)) &&
                     atomic_read(&rdev->nr_pending)==0) {