Manage: check alignment when stopping an array undergoing reshape.

To be able to revert-reshape of raid4/5/6 which is changing
the number of devices, the reshape must has been stopped on a multiple
of the old and new stripe sizes.

The kernel only enforces the new stripe size multiple.

So we enforce the old-stripe-size multiple by careful use of
"sync_max" and monitoring "reshape_position".

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

1 files changed, 11 insertions, 0 deletions

diff --git a/lib.c b/lib.c
index fa6f2232..840c11f6 100644
--- a/lib.c
+++ b/lib.c
@@ -396,3 +396,14 @@ int use_udev(void)
 	}
 	return use;
 }
+
+unsigned long GCD(unsigned long a, unsigned long b)
+{
+	while (a != b) {
+		if (a < b)
+			b -= a;
+		if (b < a)
+			a -= b;
+	}
+	return a;
+}