Assemble: allow a RAID4 to assemble easily when parity devices is missing.

If the parity device of a RAID4 is missing, then there is no immediate
risk to data.  So it doesn't matter if the array is dirty or not.

This can be important when reshaping a RAID0, and is a much better
solution that that in the resent-reverted.
   b720636a5849397dbc6dc1b0f0b671d17034a28b

Reported-by: "Jonathan Harker (Jesusaurus)" <jesusaurus@gentlydownthe.net>
Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 7 insertions, 0 deletions

diff --git a/util.c b/util.c
index 6f1e2b1..cc98d3b 100644
--- a/util.c
+++ b/util.c
@@ -368,6 +368,13 @@ int enough(int level, int raid_disks, int layout, int clean, char *avail)
 	case 1:
 		return avail_disks >= 1;
 	case 4:
+		if (avail_disks == raid_disks - 1 &&
+		    !avail[raid_disks - 1])
+			/* If just the parity device is missing, then we
+			 * have enough, even if not clean
+			 */
+			return 1;
+		/* FALL THROUGH */
 	case 5:
 		if (clean)
 			return avail_disks >= raid_disks-1;