Add --prefer option for --detail and --monitor

Both --detail and --monitor can report the names of member
devices on an array, and do so by searching /dev and finding
the shortest name that matches.

If
   --prefer=foo
is given, they will instead prefer a name that contain /foo/.
So
   mdadm --detail /dev/md0 --prefer=by-path

will list the component devices via their /dev/disk/by-path/xxx
names.

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

Detail.c

@@ -27,7 +27,7 @@
 #include	"md_u.h"
 #include	<dirent.h>
 
-int Detail(char *dev, int brief, int export, int test, char *homehost)
+int Detail(char *dev, int brief, int export, int test, char *homehost, char *prefer)
 {
 	/*
 	 * Print out details for an md array by using
@@ -105,7 +105,7 @@ int Detail(char *dev, int brief, int export, int test, char *homehost)
 		int dn = st->container_dev;
 
 		member = subarray;
-		container = map_dev(dev2major(dn), dev2minor(dn), 1);
+		container = map_dev_preferred(dev2major(dn), dev2minor(dn), 1, prefer);
 	}
 
 	/* try to load a superblock */
@@ -491,8 +491,9 @@ This is pretty boring
 				    vbuf[10+nlen] != '/')
 					continue;
 				dn = devname2devnum(de->d_name);
-				printf(" %s", map_dev(dev2major(dn),
-						      dev2minor(dn), 1));
+				printf(" %s", map_dev_preferred(
+					       dev2major(dn),
+					       dev2minor(dn), 1, prefer));
 			}
 			if (dir)
 				closedir(dir);
@@ -558,7 +559,7 @@ This is pretty boring
 		if (test && d < array.raid_disks
 		    && !(disk.state & (1<<MD_DISK_SYNC)))
 			rv |= 1;
-		if ((dv=map_dev(disk.major, disk.minor, 0))) {
+		if ((dv=map_dev_preferred(disk.major, disk.minor, 0, prefer))) {
 			if (brief) {
 				if (devices) {
 					devices = realloc(devices,

Monitor.c

@@ -69,7 +69,7 @@ static int check_one_sharer(int scan);
 static void alert(char *event, char *dev, char *disc, struct alert_info *info);
 static int check_array(struct state *st, struct mdstat_ent *mdstat,
 		       int test, struct alert_info *info,
-		       int increments);
+		       int increments, char *prefer);
 static int add_new_arrays(struct mdstat_ent *mdstat, struct state **statelist,
 			  int test, struct alert_info *info);
 static void try_spare_migration(struct state *statelist, struct alert_info *info);
@@ -79,7 +79,7 @@ int Monitor(struct mddev_dev *devlist,
 	    char *mailaddr, char *alert_cmd,
 	    int period, int daemonise, int scan, int oneshot,
 	    int dosyslog, int test, char *pidfile, int increments,
-	    int share)
+	    int share, char *prefer)
 {
 	/*
 	 * Every few seconds, scan every md device looking for changes
@@ -221,7 +221,8 @@ int Monitor(struct mddev_dev *devlist,
 		mdstat = mdstat_read(oneshot?0:1, 0);
 
 		for (st=statelist; st; st=st->next)
-			if (check_array(st, mdstat, test, &info, increments))
+			if (check_array(st, mdstat, test, &info,
+					increments, prefer))
 				anydegraded = 1;
 		
 		/* now check if there are any new devices found in mdstat */
@@ -445,7 +446,7 @@ static void alert(char *event, char *dev, char *disc, struct alert_info *info)
 
 static int check_array(struct state *st, struct mdstat_ent *mdstat,
 		       int test, struct alert_info *ainfo,
-		       int increments)
+		       int increments, char *prefer)
 {
 	/* Update the state 'st' to reflect any changes shown in mdstat,
 	 * or found by directly examining the array, and return
@@ -617,7 +618,9 @@ static int check_array(struct state *st, struct mdstat_ent *mdstat,
 			disc.major = disc.minor = 0;
 		} else if (info[i].major || info[i].minor) {
 			newstate = info[i].state;
-			dv = map_dev(info[i].major, info[i].minor, 1);
+			dv = map_dev_preferred(
+				info[i].major, info[i].minor, 1,
+				prefer);
 			disc.state = newstate;
 			disc.major = info[i].major;
 			disc.minor = info[i].minor;
@@ -629,8 +632,9 @@ static int check_array(struct state *st, struct mdstat_ent *mdstat,
 			disc.major = disc.minor = 0;
 		}
 		if (dv == NULL && st->devid[i])
-			dv = map_dev(major(st->devid[i]),
-				     minor(st->devid[i]), 1);
+			dv = map_dev_preferred(
+				major(st->devid[i]),
+				minor(st->devid[i]), 1, prefer);
 		change = newstate ^ st->devstate[i];
 		if (st->utime && change && !st->err) {
 			if (i < array.raid_disks &&

ReadMe.c

@@ -174,6 +174,7 @@ struct option long_options[] = {
     {"export",	  0, 0, 'Y'},
     {"sparc2.2",  0, 0, Sparc22},
     {"test",      0, 0, 't'},
+    {"prefer",    1, 0, Prefer},
 
     /* For Follow/monitor */
     {"mail",      1, 0, EMail},

lib.c

@@ -188,8 +188,11 @@ int nftw(const char *path, int (*han)(const char *name, const struct stat *stb,
  * If we find multiple names, choose the shortest.
  * If we find a name in /dev/md/, we prefer that.
  * This applies only to names for MD devices.
+ * If 'prefer' is set (normally to e.g. /by-path/)
+ * then we prefer a name which contains that string.
  */
-char *map_dev(int major, int minor, int create)
+char *map_dev_preferred(int major, int minor, int create,
+			char *prefer)
 {
 	struct devmap *p;
 	char *regular = NULL, *preferred=NULL;
@@ -219,7 +222,8 @@ char *map_dev(int major, int minor, int create)
 	for (p=devlist; p; p=p->next)
 		if (p->major == major &&
 		    p->minor == minor) {
-			if (strncmp(p->name, "/dev/md/",8) == 0) {
+			if (strncmp(p->name, "/dev/md/",8) == 0
+			    || (prefer && strstr(p->name, prefer))) {
 				if (preferred == NULL ||
 				    strlen(p->name) < strlen(preferred))
 					preferred = p->name;
@@ -243,6 +247,7 @@ char *map_dev(int major, int minor, int create)
 }
 
 
+
 /* conf_word gets one word from the conf file.
  * if "allow_key", then accept words at the start of a line,
  * otherwise stop when such a word is found.

mdadm.8.in

@@ -389,6 +389,28 @@ will be allowed to use 'local' names (i.e. not ending in '_' followed
 by a digit string).  See below under
 .BR "Auto Assembly" .
 
+.TP
+.B \-\-prefer=
+When
+.I mdadm
+needs to print the name for a device it normally finds the name in
+.B /dev
+which refers to the device and is shortest.  When a path component is
+given with
+.B \-\-prefer
+.I mdadm
+will prefer a longer name if it contains that component.  For example
+.B \-\-prefer=by-uuid
+will prefer a name in a subdirectory of
+.B /dev
+called
+.BR by-uuid .
+
+This functionality is currently only provided by
+.B \-\-detail
+and
+.BR \-\-monitor .
+
 .SH For create, build, or grow:
 
 .TP

mdadm.c

@@ -73,6 +73,7 @@ int main(int argc, char *argv[])
 	int test = 0;
 	int export = 0;
 	int assume_clean = 0;
+	char *prefer = NULL;
 	char *symlinks = NULL;
 	int grow_continue = 0;
 	/* autof indicates whether and how to create device node.
@@ -184,6 +185,13 @@ int main(int argc, char *argv[])
 			__offroot = 1;
 			continue;
 
+		case Prefer:
+			if (prefer)
+				free(prefer);
+			if (asprintf(&prefer, "/%s/", optarg) <= 0)
+				prefer = NULL;
+			continue;
+
 		case ':':
 		case '?':
 			fputs(Usage, stderr);
@@ -1498,7 +1506,7 @@ int main(int argc, char *argv[])
 						if (devmode == 'D')
 							rv |= Detail(name, v,
 								     export, test,
-								     homehost);
+								     homehost, prefer);
 						else
 							rv |= WaitClean(name, -1, v);
 						put_md_name(name);
@@ -1552,7 +1560,7 @@ int main(int argc, char *argv[])
 				case 'D':
 					rv |= Detail(dv->devname,
 						     brief?1+verbose:0,
-						     export, test, homehost);
+						     export, test, homehost, prefer);
 					continue;
 				case 'K': /* Zero superblock */
 					if (ss)
@@ -1626,7 +1634,8 @@ int main(int argc, char *argv[])
 		}
 		rv= Monitor(devlist, mailaddr, program,
 			    delay?delay:60, daemonise, scan, oneshot,
-			    dosyslog, test, pidfile, increments, spare_sharing);
+			    dosyslog, test, pidfile, increments,
+			    spare_sharing, prefer);
 		break;
 
 	case GROW:

mdadm.h

@@ -322,6 +322,7 @@ enum special_options {
 	FreezeReshape,
 	Continue,
 	OffRootOpt,
+	Prefer,
 };
 
 /* structures read from config file */
@@ -532,7 +533,12 @@ extern char *map_num(mapping_t *map, int num);
 extern int map_name(mapping_t *map, char *name);
 extern mapping_t r5layout[], r6layout[], pers[], modes[], faultylayout[];
 
-extern char *map_dev(int major, int minor, int create);
+extern char *map_dev_preferred(int major, int minor, int create,
+			       char *prefer);
+static inline char *map_dev(int major, int minor, int create)
+{
+	return map_dev_preferred(major, minor, create, NULL);
+}
 
 struct active_array;
 struct metadata_update;
@@ -1080,7 +1086,7 @@ extern int Create(struct supertype *st, char *mddev,
 		  int runstop, int verbose, int force, int assume_clean,
 		  char *bitmap_file, int bitmap_chunk, int write_behind, int delay, int autof);
 
-extern int Detail(char *dev, int brief, int export, int test, char *homehost);
+extern int Detail(char *dev, int brief, int export, int test, char *homehost, char *prefer);
 extern int Detail_Platform(struct superswitch *ss, int scan, int verbose);
 extern int Query(char *dev);
 extern int Examine(struct mddev_dev *devlist, int brief, int export, int scan,
@@ -1089,7 +1095,7 @@ extern int Monitor(struct mddev_dev *devlist,
 		   char *mailaddr, char *alert_cmd,
 		   int period, int daemonise, int scan, int oneshot,
 		   int dosyslog, int test, char *pidfile, int increments,
-		   int share);
+		   int share, char *prefer);
 
 extern int Kill(char *dev, struct supertype *st, int force, int quiet, int noexcl);
 extern int Kill_subarray(char *dev, char *subarray, int quiet);