5 files changed, 67 insertions, 9 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 3b5cd4ef54f1..5d6fac1fd39e 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1932,7 +1932,7 @@ slot_store(mdk_rdev_t *rdev, const char *buf, size_t len)
                 slot = -1;
         else if (e==buf || (*e && *e!= '\n'))
                 return -EINVAL;
-        if (rdev->mddev->pers) {
+        if (rdev->mddev->pers && slot == -1) {
                 /* Setting 'slot' on an active array requires also
                  * updating the 'rd%d' link, and communicating
                  * with the personality with ->hot_*_disk.
@@ -1940,8 +1940,6 @@ slot_store(mdk_rdev_t *rdev, const char *buf, size_t len)
                  * 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 */
@@ -1955,6 +1953,44 @@ slot_store(mdk_rdev_t *rdev, const char *buf, size_t len)
                 sysfs_remove_link(&rdev->mddev->kobj, nm);
                 set_bit(MD_RECOVERY_NEEDED, &rdev->mddev->recovery);
                 md_wakeup_thread(rdev->mddev->thread);
+        } else if (rdev->mddev->pers) {
+                mdk_rdev_t *rdev2;
+                struct list_head *tmp;
+                /* Activating a spare .. or possibly reactivating
+                 * if we every get bitmaps working here.
+                 */
+
+                if (rdev->raid_disk != -1)
+                        return -EBUSY;
+
+                if (rdev->mddev->pers->hot_add_disk == NULL)
+                        return -EINVAL;
+
+                rdev_for_each(rdev2, tmp, rdev->mddev)
+                        if (rdev2->raid_disk == slot)
+                                return -EEXIST;
+
+                rdev->raid_disk = slot;
+                if (test_bit(In_sync, &rdev->flags))
+                        rdev->saved_raid_disk = slot;
+                else
+                        rdev->saved_raid_disk = -1;
+                err = rdev->mddev->pers->
+                        hot_add_disk(rdev->mddev, rdev);
+                if (err != 1) {
+                        rdev->raid_disk = -1;
+                        if (err == 0)
+                                return -EEXIST;
+                        return err;
+                }
+                sprintf(nm, "rd%d", rdev->raid_disk);
+                if (sysfs_create_link(&rdev->mddev->kobj, &rdev->kobj, nm))
+                        printk(KERN_WARNING
+                               "md: cannot register "
+                               "%s for %s\n",
+                               nm, mdname(rdev->mddev));
+
+                /* don't wakeup anyone, leave that to userspace. */
         } else {
                 if (slot >= rdev->mddev->raid_disks)
                         return -ENOSPC;
diff --git a/drivers/md/multipath.c b/drivers/md/multipath.c
index e968116e0de9..4a1d714c048e 100644
--- a/drivers/md/multipath.c
+++ b/drivers/md/multipath.c
@@ -284,10 +284,15 @@ static int multipath_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
         int found = 0;
         int path;
         struct multipath_info *p;
+        int first = 0;
+        int last = mddev->raid_disks - 1;
+
+        if (rdev->raid_disk >= 0)
+                first = last = rdev->raid_disk;
 
         print_multipath_conf(conf);
 
-        for (path=0; path<mddev->raid_disks; path++) 
+        for (path = first; path <= last; path++)
                 if ((p=conf->multipaths+path)->rdev == NULL) {
                         q = rdev->bdev->bd_disk->queue;
                         blk_queue_stack_limits(mddev->queue, q);
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index c610b947218a..d32fc559ff05 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1103,8 +1103,13 @@ static int raid1_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
         int found = 0;
         int mirror = 0;
         mirror_info_t *p;
+        int first = 0;
+        int last = mddev->raid_disks - 1;
 
-        for (mirror=0; mirror < mddev->raid_disks; mirror++)
+        if (rdev->raid_disk >= 0)
+                first = last = rdev->raid_disk;
+
+        for (mirror = first; mirror <= last; mirror++)
                 if ( !(p=conf->mirrors+mirror)->rdev) {
 
                         blk_queue_stack_limits(mddev->queue,
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index a71277b640ab..50ad8d2ae0e8 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1116,6 +1116,8 @@ static int raid10_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
         int found = 0;
         int mirror;
         mirror_info_t *p;
+        int first = 0;
+        int last = mddev->raid_disks - 1;
 
         if (mddev->recovery_cp < MaxSector)
                 /* only hot-add to in-sync arrays, as recovery is
@@ -1125,12 +1127,16 @@ static int raid10_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
         if (!enough(conf))
                 return 0;
 
+        if (rdev->raid_disk)
+                first = last = rdev->raid_disk;
+
         if (rdev->saved_raid_disk >= 0 &&
+            rdev->saved_raid_disk >= first &&
             conf->mirrors[rdev->saved_raid_disk].rdev == NULL)
                 mirror = rdev->saved_raid_disk;
         else
-                mirror = 0;
-        for ( ; mirror < mddev->raid_disks; mirror++)
+                mirror = first;
+        for ( ; mirror <= last ; mirror++)
                 if ( !(p=conf->mirrors+mirror)->rdev) {
 
                         blk_queue_stack_limits(mddev->queue,
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;