md: Fix handling of raid5 array which is being reshaped to fewer devices.

When a raid5 (or raid6) array is being reshaped to have fewer devices,
conf->raid_disks is the latter and hence smaller number of devices.
However sometimes we want to use a number which is the total number of
currently required devices - the larger of the 'old' and 'new' sizes.
Before we implemented reducing the number of devices, this was always
'new' i.e. ->raid_disks.
Now we need max(raid_disks, previous_raid_disks) in those places.

This particularly affects assembling an array that was shutdown while
in the middle of a reshape to fewer devices.

md.c needs a similar fix when interpreting the md metadata.

Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 26ba42a79129..10eb1fce975e 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -2631,7 +2631,7 @@ static void analyze_sbs(mddev_t * mddev)
 			rdev->desc_nr = i++;
 			rdev->raid_disk = rdev->desc_nr;
 			set_bit(In_sync, &rdev->flags);
-		} else if (rdev->raid_disk >= mddev->raid_disks) {
+		} else if (rdev->raid_disk >= (mddev->raid_disks - min(0, mddev->delta_disks))) {
 			rdev->raid_disk = -1;
 			clear_bit(In_sync, &rdev->flags);
 		}