[PATCH] md: cause md/raid1 to "repack" working devices when number of drives is changed

i.e.  missing or failed drives are moved to the end of the list.  The means
a 3 drive md array with the first drive missing can be shrunk to a two
drive array.  Currently that isn't possible.

Also, the "last_used" device number might be out-of-range after the number
of devices is reduced, so we set it to 0.

Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 19 insertions, 5 deletions

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 1db5de52d376..4947f599b652 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1349,17 +1349,26 @@ static int raid1_reshape(mddev_t *mddev, int raid_disks)
          * We allocate a new r1bio_pool if we can.
          * Then raise a device barrier and wait until all IO stops.
          * Then resize conf->mirrors and swap in the new r1bio pool.
+         *
+         * At the same time, we "pack" the devices so that all the missing
+         * devices have the higher raid_disk numbers.
          */
         mempool_t *newpool, *oldpool;
         struct pool_info *newpoolinfo;
         mirror_info_t *newmirrors;
         conf_t *conf = mddev_to_conf(mddev);
+        int cnt;
 
-        int d;
+        int d, d2;
 
-        for (d= raid_disks; d < conf->raid_disks; d++)
-                if (conf->mirrors[d].rdev)
+        if (raid_disks < conf->raid_disks) {
+                cnt=0;
+                for (d= 0; d < conf->raid_disks; d++)
+                        if (conf->mirrors[d].rdev)
+                                cnt++;
+                if (cnt > raid_disks)
                         return -EBUSY;
+        }
 
         newpoolinfo = kmalloc(sizeof(*newpoolinfo), GFP_KERNEL);
         if (!newpoolinfo)
@@ -1390,8 +1399,12 @@ static int raid1_reshape(mddev_t *mddev, int raid_disks)
         /* ok, everything is stopped */
         oldpool = conf->r1bio_pool;
         conf->r1bio_pool = newpool;
-        for (d=0; d < raid_disks && d < conf->raid_disks; d++)
-                newmirrors[d] = conf->mirrors[d];
+
+        for (d=d2=0; d < conf->raid_disks; d++)
+                if (conf->mirrors[d].rdev) {
+                        conf->mirrors[d].rdev->raid_disk = d2;
+                        newmirrors[d2++].rdev = conf->mirrors[d].rdev;
+                }
         kfree(conf->mirrors);
         conf->mirrors = newmirrors;
         kfree(conf->poolinfo);
@@ -1400,6 +1413,7 @@ static int raid1_reshape(mddev_t *mddev, int raid_disks)
         mddev->degraded += (raid_disks - conf->raid_disks);
         conf->raid_disks = mddev->raid_disks = raid_disks;
 
+        conf->last_used = 0; /* just make sure it is in-range */
         spin_lock_irq(&conf->resync_lock);
         conf->barrier--;
         spin_unlock_irq(&conf->resync_lock);