Grow: do not allow size changes with other changes.

A change the reduces the size of an array always happens
before any other change.  So it can cause data to be lost.
By themselves these changes are reversible.  But once another
change has started, the data would be permanently lost.
So recommend data integrity be checked between a size change
and any other change.

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

1 files changed, 9 insertions, 0 deletions

diff --git a/mdadm.c b/mdadm.c
index 0c51d63..3dc8be9 100644
--- a/mdadm.c
+++ b/mdadm.c
@@ -1417,9 +1417,18 @@ int main(int argc, char *argv[])
 		if (array_size >= 0) {
 			/* alway impose array size first, independent of
 			 * anything else
+			 * Do not allow level or raid_disks changes at the
+			 * same time as that can be irreversibly destructive.
 			 */
 			struct mdinfo sra;
 			int err;
+			if (raiddisks || level != UnSet) {
+				fprintf(stderr, Name ": cannot change array size in same operation "
+					"as changing raiddisks or level.\n"
+					"    Change size first, then check that data is still intact.\n");
+				rv = 1;
+				break;
+			}
 			sysfs_init(&sra, mdfd, 0);
 			if (array_size == 0)
 				err = sysfs_set_str(&sra, NULL, "array_size", "default");