auto-start mdmon on --create

FIXME uses sill hardcoded path.

Need --assemble too.

Create.c

@@ -71,6 +71,8 @@ int Create(struct supertype *st, char *mddev, int mdfd,
 	int rv;
 	int bitmap_fd;
 	int have_container = 0;
+	int container_fd;
+	int need_mdmon = 0;
 	unsigned long long bitmapsize;
 	struct mdinfo *sra;
 	struct mdinfo info;
@@ -545,6 +547,31 @@ int Create(struct supertype *st, char *mddev, int mdfd,
 			sprintf(ver, "external:/%s/%d",
 				devnum2devname(st->container_dev),
 				st->container_member);
+			/* When creating a member, we need to be careful
+			 * to negotiate with mdmon properly.
+			 * If it is already running, we cannot write to
+			 * the devices and must ask it to do that part.
+			 * If it isn't running, we write to the devices,
+			 * and then start it.
+			 * We hold an exclusive open on the container
+			 * device to make sure mdmon doesn't exit after
+			 * we checked that it is running.
+			 *
+			 * For now, fail if it is already running.
+			 */
+			container_fd = open_dev_excl(st->container_dev);
+			if (container_fd < 0) {
+				fprintf(stderr, Name ": Cannot get exclusive "
+					"open on container - weird.\n");
+				return 1;
+			}
+			if (mdmon_running(st->container_dev)) {
+				fprintf(stderr, Name ": mdmon already running "
+					"for %s - sorry\n",
+					devnum2devname(st->container_dev));
+				return 1;
+			}
+			need_mdmon = 1;
 		}
 		if ((vers % 100) < 2 ||
 		    sra == NULL ||
@@ -681,6 +708,7 @@ int Create(struct supertype *st, char *mddev, int mdfd,
 			case 0:
 				sysfs_set_str(sra, NULL, "array_state",
 					      "active");
+				need_mdmon = 0;
 				break;
 			default:
 				sysfs_set_str(sra, NULL, "array_state",
@@ -698,6 +726,31 @@ int Create(struct supertype *st, char *mddev, int mdfd,
 		}
 		if (verbose >= 0)
 			fprintf(stderr, Name ": array %s started.\n", mddev);
+		if (st->ss->external == 2) {
+			if (need_mdmon) {
+				int dn = st->container_dev;
+				int i;
+				switch(fork()) {
+				case 0:
+					/* FIXME yuk. CLOSE_EXEC?? */
+					for (i=3; i < 100; i++)
+						close(i);
+					execl("./mdmon", "mdmon",
+					      map_dev(dev2major(dn),
+						      dev2minor(dn),
+						      1), NULL);
+					exit(1);
+				case -1: fprintf(stderr, Name ": cannot fork. "
+						 "Array remains readonly\n");
+					return 1;
+				default: ; /* parent - good */
+				}
+			} else
+				signal_mdmon(st->container_dev);
+			/* FIXME wait for mdmon to set array to read-auto */
+			sleep(1);
+			close(container_fd);
+		}
 	} else {
 		fprintf(stderr, Name ": not starting array - not enough devices.\n");
 	}

mdadm.h

@@ -584,6 +584,7 @@ extern int check_raid(int fd, char *name);
 
 extern int get_mdp_major(void);
 extern int dev_open(char *dev, int flags);
+extern int open_dev_excl(int devnum);
 extern int is_standard(char *dev, int *nump);
 
 extern int parse_auto(char *str, char *msg, int config);
@@ -629,9 +630,27 @@ extern int open_mddev_devnum(char *devname, int devnum, char *name,
 			     char *chosen_name, int parts);
 extern int open_container(int fd);
 
+extern int mdmon_running(int devnum);
+extern int signal_mdmon(int devnum);
+
 extern char *devnum2devname(int num);
 extern int fd2devnum(int fd);
 
+static inline int dev2major(int d)
+{
+	if (d >= 0)
+		return MD_MAJOR;
+	else
+		return get_mdp_major();
+}
+
+static inline int dev2minor(int d)
+{
+	if (d >= 0)
+		return d;
+	return (-1-d) << MdpMinorShift;
+}
+
 #define	LEVEL_MULTIPATH		(-4)
 #define	LEVEL_LINEAR		(-1)
 #define	LEVEL_FAULTY		(-5)

util.c

@@ -32,6 +32,7 @@
 #include	<sys/utsname.h>
 #include	<ctype.h>
 #include	<dirent.h>
+#include	<signal.h>
 
 /*
  * following taken from linux/blkpg.h because they aren't
@@ -714,21 +715,6 @@ void put_md_name(char *name)
 		unlink(name);
 }
 
-static int dev2major(int d)
-{
-	if (d >= 0)
-		return MD_MAJOR;
-	else
-		return get_mdp_major();
-}
-
-static int dev2minor(int d)
-{
-	if (d >= 0)
-		return d;
-	return (-1-d) << MdpMinorShift;
-}
-
 int find_free_devnum(int use_partitions)
 {
 	int devnum;
@@ -781,6 +767,23 @@ int dev_open(char *dev, int flags)
 	return fd;
 }
 
+int open_dev_excl(int devnum)
+{
+	char buf[20];
+	int i;
+
+	sprintf(buf, "%d:%d", dev2major(devnum), dev2minor(devnum));
+	for (i=0 ; i<25 ; i++) {
+		int fd = dev_open(buf, O_RDWR|O_EXCL);
+		if (fd >= 0)
+			return fd;
+		if (errno != EBUSY)
+			return fd;
+		usleep(200000);
+	}
+	return -1;
+}
+
 struct superswitch *superlist[] = { &super0, &super1, &super_ddf, &super_imsm, NULL };
 
 #if !defined(MDASSEMBLE) || defined(MDASSEMBLE) && defined(MDASSEMBLE_AUTO)
@@ -1009,6 +1012,48 @@ int fd2devnum(int fd)
 	return -1;
 }
 
+int mdmon_running(int devnum)
+{
+	char path[100];
+	char pid[10];
+	int fd;
+	int n;
+	sprintf(path, "/var/run/mdadm/%s.pid", devnum2devname(devnum));
+	fd = open(path, O_RDONLY, 0);
+
+	if (fd < 0)
+		return 0;
+	n = read(fd, pid, 9);
+	close(fd);
+	if (n <= 0)
+		return 0;
+	if (kill(atoi(pid), 0) == 0)
+		return 1;
+	return 0;
+}
+
+int signal_mdmon(int devnum)
+{
+	char path[100];
+	char pid[10];
+	int fd;
+	int n;
+	sprintf(path, "/var/run/mdadm/%s.pid", devnum2devname(devnum));
+	fd = open(path, O_RDONLY, 0);
+
+	if (fd < 0)
+		return 0;
+	n = read(fd, pid, 9);
+	close(fd);
+	if (n <= 0)
+		return 0;
+	if (kill(atoi(pid), SIGUSR1) == 0)
+		return 1;
+	return 0;
+}
+
+
+
 #ifdef __TINYC__
 /* tinyc doesn't optimize this check in ioctl.h out ... */
 unsigned int __invalid_size_argument_for_IOC = 0;