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, 39 insertions, 3 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;