Allow default metadata to be specified in mdadm.conf

CREATE metadata=1
in mdadm.conf will cause version-1 superblocks to be the default.

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

Create.c

@@ -214,6 +214,11 @@ int Create(struct supertype *st, char *mddev, int mdfd,
 			ldsize = dsize;
 			ldsize <<= 9;
 		}
+		if (st == NULL) {
+			struct createinfo *ci = conf_get_create_info(NULL);
+			if (ci)
+				st = ci->supertype;
+		}
 		if (st == NULL) {
 			/* Need to choose a default metadata, which is different
 			 * depending on the sizes of devices

config.c

@@ -354,6 +354,16 @@ static void createline(char *line)
 				fprintf(stderr, Name ": unrecognised CREATE mode %s\n",
 					w+5);
 			}
+		} else if (strncasecmp(w, "metadata=", 9) == 0) {
+			/* style of metadata to use by default */
+			int i;
+			for (i=0; superlist[i] && !createinfo.supertype; i++)
+				createinfo.supertype =
+					superlist[i]->match_metadata_desc(w+9);
+			if (!createinfo.supertype)
+				fprintf(stderr, Name ": metadata format %s unknown, ignoring\n",
+					w+9);
+
 		} else {
 			fprintf(stderr, Name ": unrecognised word on CREATE line: %s\n",
 				w);

mdadm.conf.5

@@ -126,6 +126,17 @@ this is mainly for compatibility with the output of
 
 .BR "mdadm --examine --scan" .
 
+.TP
+.B spares=
+The value is a number of spare devices to expect the array to have.
+.I mdadm --monitor
+will report an array if it is found to have fewer than this number of
+spares when
+.B --monitor
+starts or when
+.B --oneshot
+is used.
+
 .TP
 .B spare-group=
 The value is a textual name for a group of arrays.  All arrays with
@@ -165,6 +176,13 @@ driver as the bitmap file.  This has the same function as the
 .B --bitmap-file
 option to
 .BR --assemble .
+
+.TP
+.B metadata=
+Specify the metadata format that the array has.  This is mainly
+recognised for comparability with the output of
+.IR "mdadm -Es" .
+
 .RE
 
 .TP
@@ -217,7 +235,7 @@ line and it should be give only one program.
 .B CREATE
 The
 .B create
-line gives default values to be used when creating device entries for
+line gives default values to be used when creating arrays and device entries for
 arrays.
 These include:
 
@@ -244,6 +262,11 @@ flag to mdadm.  Give
 - possibly followed by a number of partitions - to indicate how
 missing device entries should be created.
 
+.TP
+.B metadata=
+The name of the metadata format to use if none is explicitly given.
+This can be useful to impose a system-wide default of version-1 superblocks.
+
 .RE
 
 

mdadm.h

@@ -116,6 +116,7 @@ struct createinfo {
 	int	gid;
 	int	autof;
 	int	mode;
+	struct supertype *supertype;
 };
 
 #define Name "mdadm"