revert-reshape: make sure reshape_position is acceptable.

We can only revert a reshape if the reshape_position aligns
properly for the old geometry.
If it doesn't we just fail for now.

Also fix a +/- error with updating raid_disks for super1.c

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

1 files changed, 9 insertions, 0 deletions

diff --git a/super0.c b/super0.c
index ff4c657c..b2019dfa 100644
--- a/super0.c
+++ b/super0.c
@@ -654,7 +654,16 @@ static int update_super0(struct supertype *st, struct mdinfo *info,
 			       devname);
 		else {
 			int tmp;
+			int parity = sb->level == 6 ? 2 : 1;
 			rv = 0;
+
+			if (sb->reshape_position % (
+				    sb->new_chunk/512 *
+				    (sb->raid_disks - sb->delta_disks - parity))) {
+				pr_err("Reshape position is not suitably aligned.\n");
+				pr_err("Try normal assembly as stop again\n");
+				return -2;
+			}
 			sb->raid_disks -= sb->delta_disks;
 			sb->delta_disks = -sb->delta_disks;