1 files changed, 7 insertions, 2 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 66cd47973398..96c690279fc6 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -5526,8 +5526,13 @@ static int raid5_start_reshape(mddev_t *mddev)
 
         /* Add some new drives, as many as will fit.
          * We know there are enough to make the newly sized array work.
+         * Don't add devices if we are reducing the number of
+         * devices in the array.  This is because it is not possible
+         * to correctly record the "partially reconstructed" state of
+         * such devices during the reshape and confusion could result.
          */
-        list_for_each_entry(rdev, &mddev->disks, same_set)
+        if (mddev->delta_disks >= 0)
+            list_for_each_entry(rdev, &mddev->disks, same_set)
                 if (rdev->raid_disk < 0 &&
                     !test_bit(Faulty, &rdev->flags)) {
                         if (raid5_add_disk(mddev, rdev) == 0) {
@@ -5549,7 +5554,7 @@ static int raid5_start_reshape(mddev_t *mddev)
                 }
 
         /* When a reshape changes the number of devices, ->degraded
-         * is measured against the large of the pre and post number of
+         * is measured against the larger of the pre and post number of
          * devices.*/
         if (mddev->delta_disks > 0) {
                 spin_lock_irqsave(&conf->device_lock, flags);