Support updating of uuid during --assemble.

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

Assemble.c

@@ -219,7 +219,7 @@ int Assemble(struct supertype *st, char *mddev, int mdfd,
 		}
 		if (dfd >= 0) close(dfd);
 
-		if (ident->uuid_set &&
+		if (ident->uuid_set && (!update && strcmp(update, "uuid")!= 0) &&
 		    (!super || same_uuid(info.uuid, ident->uuid, tst->ss->swapuuid)==0)) {
 			if ((inargv && verbose >= 0) || verbose > 0)
 				fprintf(stderr, Name ": %s has wrong uuid.\n",
@@ -281,7 +281,21 @@ int Assemble(struct supertype *st, char *mddev, int mdfd,
 			struct stat stb2;
 			fstat(mdfd, &stb2);
 			info.array.md_minor = minor(stb2.st_rdev);
-			
+
+			if (strcmp(update, "uuid")==0 &&
+			    !ident->uuid_set) {
+				int rfd;
+				if ((rfd = open("/dev/urandom", O_RDONLY)) < 0 ||
+				    read(rfd, ident->uuid, 16) != 16) {
+					*(__u32*)(ident->uuid) = random();
+					*(__u32*)(ident->uuid+1) = random();
+					*(__u32*)(ident->uuid+2) = random();
+					*(__u32*)(ident->uuid+3) = random();
+				}
+				if (rfd >= 0) close(rfd);
+				ident->uuid_set = 1;
+			}
+			memcpy(info.uuid, ident->uuid, 16);
 			st->ss->update_super(&info, super, update, devname, verbose);
 			
 			dfd = dev_open(devname, O_RDWR|O_EXCL);

ChangeLog

@@ -18,6 +18,7 @@ Changes Prior to this release
 	mdadm was insisting the event numbers were identical, but this
 	isn't needed, and is a problem if the crash was while the metadata
 	was being updated.
+    -   Support --update==uuid
 
 Changes Prior to 2.1 release
     -   Fix assembling of raid10 array when devices are missing.

mdadm.8

@@ -610,6 +610,7 @@ Update the superblock on each device while assembling the array.  The
 argument given to this flag can be one of
 .BR sparc2.2 ,
 .BR summaries ,
+.BR uuid ,
 .BR resync ,
 .BR byteorder ,
 or
@@ -617,7 +618,7 @@ or
 
 The
 .B sparc2.2
-option will  adjust the superblock of an array what was created on a Sparc
+option will adjust the superblock of an array what was created on a Sparc
 machine running a patched 2.2 Linux kernel.  This kernel got the
 alignment of part of the superblock wrong.  You can use the
 .B "--examine --sparc2.2"
@@ -633,6 +634,14 @@ field on each superblock to match the minor number of the array being
 assembled.  This is not needed on 2.6 and later kernels as they make
 this adjustment automatically.
 
+The
+.B uuid
+option will change the uuid of the array.  If a UUID is given with the
+"--uuid" option that UUID will be used as a new UUID and with
+.B NOT
+be used to help identify the devices in the array.
+If no "--uuid" is given, a random uuid is chosen.
+
 The
 .B resync
 option will cause the array to be marked

mdadm.c

@@ -593,6 +593,8 @@ int main(int argc, char *argv[])
 				continue;
 			if (strcmp(update, "resync")==0)
 				continue;
+			if (strcmp(update, "uuid")==0)
+				continue;
 			if (strcmp(update, "byteorder")==0) {
 				if (ss) {
 					fprintf(stderr, Name ": must not set metadata type with --update=byteorder.\n");
@@ -607,7 +609,7 @@ int main(int argc, char *argv[])
 
 				continue;
 			}
-			fprintf(stderr, Name ": '--update %s' invalid.  Only 'sparc2.2', 'super-minor', 'resync' or 'summaries' supported\n",update);
+			fprintf(stderr, Name ": '--update %s' invalid.  Only 'sparc2.2', 'super-minor', 'uuid', 'resync' or 'summaries' supported\n",update);
 			exit(2);
 
 		case O(ASSEMBLE,'c'): /* config file */

super0.c

@@ -359,6 +359,12 @@ static int update_super0(struct mdinfo *info, void *sbv, char *update, char *dev
 		sb->state &= ~(1<<MD_SB_CLEAN);
 		sb->recovery_cp = 0;
 	}
+	if (strcmp(update, "uuid") == 0) {
+		sb->set_uuid0 = info->uuid[0];
+		sb->set_uuid1 = info->uuid[1];
+		sb->set_uuid2 = info->uuid[2];
+		sb->set_uuid3 = info->uuid[3];
+	}
 
 	sb->sb_csum = calc_sb0_csum(sb);
 	return rv;

super1.c

@@ -381,6 +381,8 @@ static int update_super1(struct mdinfo *info, void *sbv, char *update, char *dev
 		/* make sure resync happens */
 		sb->resync_offset = ~0ULL;
 	}
+	if (strcmp(update, "uuid") == 0)
+		memcmp(sb->set_uuid, info->uuid, 16);
 
 	sb->sb_csum = calc_sb_1_csum(sb);
 	return rv;