When assembly arrays using incomplete detail, prefer arrays built for this host.

i.e. if assembling with --name or --super-minor, then if we find two
different arrays with the same apparent identity, and one was built
for 'this' host, then prefer that one instead of giving up in disgust.

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

Assemble.c

@@ -277,9 +277,11 @@ int Assemble(struct supertype *st, char *mddev, int mdfd,
 			continue;
 		}
 
-		/* If we are this far, then we are commited to this device.
+		/* If we are this far, then we are nearly commited to this device.
 		 * If the super_block doesn't exist, or doesn't match others,
-		 * then we cannot continue
+		 * then we probably cannot continue
+		 * However if one of the arrays is for the homehost, and
+		 * the other isn't that can disambiguate.
 		 */
 
 		if (!super) {
@@ -289,9 +291,37 @@ int Assemble(struct supertype *st, char *mddev, int mdfd,
 			return 1;
 		}
 
-
-		st = tst; /* commit to this format, if haven't already */
-		if (st->ss->compare_super(&first_super, super)) {
+		if (st == NULL)
+			st = tst;
+		if (st->ss != tst->ss ||
+		    st->minor_version != tst->minor_version ||
+		    st->ss->compare_super(&first_super, super) != 0) {
+			/* Some mismatch. If exactly one array matches this host,
+			 * we can resolve on that one
+			 */
+			if (homehost) {
+				int first = st->ss->match_home(first_super, homehost);
+				int last = tst->ss->match_home(super, homehost);
+				if (first+last == 1) {
+					/* We can do something */
+					if (first) {/* just ignore this one */
+						if ((inargv && verbose >= 0) || verbose > 0)
+							fprintf(stderr, Name ": %s misses out due to wrong homehost\n",
+								devname);
+						continue;
+					} else { /* reject all those sofar */
+						mddev_dev_t td;
+						if ((inargv && verbose >= 0) || verbose > 0)
+							fprintf(stderr, Name ": %s overrides previous devices due to good homehost\n",
+								devname);
+						for (td=devlist; td != tmpdev; td=td->next)
+							if (td->used == 1)
+								td->used = 0;
+						tmpdev->used = 1;
+						continue;
+					}
+				}
+			}
 			fprintf(stderr, Name ": superblock on %s doesn't match others - assembly aborted\n",
 				devname);
 			free(super);

mdadm.h

@@ -279,6 +279,7 @@ extern struct superswitch {
 	void (*brief_detail_super)(void *sbv);
 	void (*uuid_from_super)(int uuid[4], void *sbv);
 	void (*getinfo_super)(struct mdinfo *info, void *sbv);
+	int (*match_home)(void *sbv, char *homehost);
 	int (*update_super)(struct mdinfo *info, void *sbv, char *update,
 			    char *devname, int verbose,
 			    int uuid_set, char *homehost);

super0.c

@@ -269,6 +269,17 @@ static void brief_detail_super0(void *sbv)
 		printf("%08x", sb->set_uuid0);
 }
 #endif
+
+static int match_home0(void *sbv, char *homehost)
+{
+	mdp_super_t *sb = sbv;
+	unsigned char *hash = SHA1((unsigned char *)homehost,
+				   strlen(homehost),
+				   NULL);
+
+	return (memcmp(&sb->set_uuid2, hash, 8)==0);
+}
+
 static void uuid_from_super0(int uuid[4], void * sbv)
 {
 	mdp_super_t *super = sbv;
@@ -942,6 +953,7 @@ struct superswitch super0 = {
 	.detail_super = detail_super0,
 	.brief_detail_super = brief_detail_super0,
 #endif
+	.match_home = match_home0,
 	.uuid_from_super = uuid_from_super0,
 	.getinfo_super = getinfo_super0,
 	.update_super = update_super0,

super1.c

@@ -357,6 +357,16 @@ static void brief_detail_super1(void *sbv)
 
 #endif
 
+static int match_home1(void *sbv, char *homehost)
+{
+	struct mdp_superblock_1 *sb = sbv;
+	int l = homehost ? strlen(homehost) : 0;
+
+	return (l > 0 && l < 32 &&
+		sb->set_name[l] == ':' &&
+		strncmp(sb->set_name, homehost, l) == 0);
+}
+
 static void uuid_from_super1(int uuid[4], void * sbv)
 {
 	struct mdp_superblock_1 *super = sbv;
@@ -1191,6 +1201,7 @@ struct superswitch super1 = {
 	.detail_super = detail_super1,
 	.brief_detail_super = brief_detail_super1,
 #endif
+	.match_home = match_home1,
 	.uuid_from_super = uuid_from_super1,
 	.getinfo_super = getinfo_super1,
 	.update_super = update_super1,