From: NeilBrown <neilb@suse.de>
Date: Tue, 15 May 2012 01:59:40 +0000 (+1000)
Subject: Grow: fix --layout=preserve to match man page.
X-Git-Tag: mdadm-3.2.5~8
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=385167f364122c9424aa3d56f00b8c0874ce78b8;p=thirdparty%2Fmdadm.git

Grow: fix --layout=preserve to match man page.

I think there was some confusion about what --layout=preserve
actually means, but in any case it wasn't doing what the man
page says it should.
So add some case analysis and make sure it does the right thing,
or complains if it cannot.

Reported-by: Patrik Horník <patrik@dsl.sk>
Signed-off-by: NeilBrown <neilb@suse.de>
---

diff --git a/Grow.c b/Grow.c
index 330e7195..9350a079 100644
--- a/Grow.c
+++ b/Grow.c
@@ -1885,9 +1885,37 @@ size_change_error:
 				*h = 0;
 				info.new_layout = map_name(r6layout, l);
 			}
+		} else {
+			fprintf(stderr, Name
+				": %s is only meaningful when reshaping"
+				" a RAID6 array.\n", layout_str);
+			rv = 1;
+			goto release;
 		}
 	} else if (strcmp(layout_str, "preserve") == 0) {
-		info.new_layout = UnSet;
+		/* This means that a non-standard RAID6 layout
+		 * is OK.
+		 * In particular:
+		 * - When reshape a RAID6 (e.g. adding a device)
+		 *   which is in a non-standard layout, it is OK
+		 *   to preserve that layout.
+		 * - When converting a RAID5 to RAID6, leave it in
+		 *   the XXX-6 layout, don't re-layout.
+		 */
+		if (info.array.level == 6 && info.new_level == UnSet)
+			info.new_layout = info.array.layout;
+		else if (info.array.level == 5 && info.new_level == 6) {
+			char l[40];
+			strcpy(l, map_num(r5layout, info.array.layout));
+			strcat(l, "-6");
+			info.new_layout = map_name(r6layout, l);
+		} else {
+			fprintf(stderr, Name
+				": %s in only meaningful when reshaping"
+				" to RAID6\n", layout_str);
+			rv = 1;
+			goto release;
+		}
 	} else {
 		int l = info.new_level;
 		if (l == UnSet)