1 files changed, 7 insertions, 2 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 3930b3e9aa04..5694eb8941b6 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -4169,8 +4169,13 @@ raid5_size(mddev_t *mddev, sector_t sectors, int raid_disks)
 
         if (!sectors)
                 sectors = mddev->dev_sectors;
-        if (!raid_disks)
-                raid_disks = conf->previous_raid_disks;
+        if (!raid_disks) {
+                /* size is defined by the smallest of previous and new size */
+                if (conf->raid_disks < conf->previous_raid_disks)
+                        raid_disks = conf->raid_disks;
+                else
+                        raid_disks = conf->previous_raid_disks;
+        }
 
         sectors &= ~((sector_t)mddev->chunk_size/512 - 1);
         return sectors * (raid_disks - conf->max_degraded);