Add --auto-detect for in-kernel autodetect.

This is equivalent to raidautorun that some distros provide.

ChangeLog

@@ -7,6 +7,7 @@ Changes Prior to this release
     -   --help now goes to stdout so you can direct it to a pager.
     -   Various manpage updates.
     -   Make "--grow --add" for linear arrays really work.
+    -   --auto-detect to trigger in-kernel autodetect.
 
 Changes Prior to 2.6.1 release
     -   --monitor was producing some meaningless warnings due to a bug.

Manage.c

@@ -507,4 +507,17 @@ int Manage_subdevs(char *devname, int fd,
 	return 0;
 	
 }
+
+int autodetect(void)
+{
+	/* Open any md device, and issue the RAID_AUTORUN ioctl */
+	int rv = 1;
+	int fd = dev_open("9:0", O_RDONLY);
+	if (fd >= 0) {
+		if (ioctl(fd, RAID_AUTORUN, 0) == 0)
+			rv = 0;
+		close(fd);
+	}
+	return rv;
+}
 #endif

ReadMe.c

@@ -109,6 +109,7 @@ struct option long_options[] = {
     {"zero-superblock", 0, 0, 'K'}, /* deliberately no a short_option */
     {"query",	  0, 0, 'Q'},
     {"examine-bitmap", 0, 0, 'X'},
+    {"auto-detect", 0, 0, AutoDetect},
 
     /* synonyms */
     {"monitor",   0, 0, 'F'},
@@ -255,6 +256,7 @@ char OptionHelp[] =
 "  --incremental -I   : add a single device to an array as appropriate\n"
 "  --query       -Q   : Display general information about how a\n"
 "                       device relates to the md driver\n"
+"  --auto-detect      : Start arrays auto-detected by the kernel\n"
 ;
 /*
 "\n"
@@ -624,6 +626,7 @@ mapping_t modes[] = {
 	{ "monitor", MONITOR},
 	{ "grow", GROW},
 	{ "incremental", INCREMENTAL},
+	{ "auto-detect", AUTODETECT},
 };
 
 mapping_t faultylayout[] = {

mdadm.8

@@ -154,6 +154,10 @@ information gathering operations.
 '''This mode allows operations on independent devices such as examine MD
 '''superblocks, erasing old superblocks and stopping active arrays.
 
+.TP
+.B Auto-detect
+This mode does not act on a specific device or array, but rather it
+requests the Linux Kernel to activate any auto-detected arrays.
 .SH OPTIONS
 
 .SH Options for selecting a mode are:
@@ -181,9 +185,24 @@ mode.
 Change the size or shape of an active array.
 
 .TP
-.BE \-I ", " \-\-incremental
+.BR \-I ", " \-\-incremental
 Add a single device into an appropriate array, and possibly start the array.
 
+.TP
+.B \-\-auto-detect
+Request that the kernel starts any auto-detected arrays.  This can only
+work if
+.I md
+is compiled into the kernel \(em not if it is a module.
+Arrays can be auto-detected by the kernel if all the components are in
+primary MS-DOS partitions with partition type
+.BR FD .
+In-kernel autodetect is not recommended for new installations.  Using
+.I mdadm
+to detect and assemble arrays \(em possibly in an
+.I initrd
+\(em is substantially more flexible and should be preferred.
+
 .P
 If a device is given before any options, or if the first option is
 .BR \-\-add ,

mdadm.c

@@ -198,6 +198,8 @@ int main(int argc, char *argv[])
 		case 'F': newmode = MONITOR;break;
 		case 'G': newmode = GROW; shortopt = short_bitmap_auto_options; break;
 		case 'I': newmode = INCREMENTAL; break;
+		case AutoDetect:
+			newmode = AUTODETECT; break;
 
 		case '#':
 		case 'D':
@@ -277,6 +279,7 @@ int main(int argc, char *argv[])
 		case 'F':
 		case 'G':
 		case 'I':
+		case AutoDetect:
 			continue;
 		}
 		if (opt == 1) {
@@ -1344,6 +1347,10 @@ int main(int argc, char *argv[])
 		}
 		rv = Incremental(devlist->devname, verbose-quiet, runstop,
 				 ss, homehost, autof);
+		break;
+	case AUTODETECT:
+		autodetect();
+		break;
 	}
 	exit(rv);
 }

mdadm.h

@@ -151,6 +151,7 @@ enum mode {
 	MONITOR,
 	GROW,
 	INCREMENTAL,
+	AUTODETECT,
 };
 
 extern char short_options[];
@@ -175,6 +176,7 @@ enum special_options {
 	HomeHost,
 	AutoHomeHost,
 	Symlinks,
+	AutoDetect,
 };
 
 /* structures read from config file */
@@ -415,6 +417,7 @@ extern int Manage_resize(char *devname, int fd, long long size, int raid_disks);
 extern int Manage_reconfig(char *devname, int fd, int layout);
 extern int Manage_subdevs(char *devname, int fd,
 			  mddev_dev_t devlist, int verbose);
+extern int autodetect(void);
 extern int Grow_Add_device(char *devname, int fd, char *newdev);
 extern int Grow_addbitmap(char *devname, int fd, char *file, int chunk, int delay, int write_behind, int force);
 extern int Grow_reshape(char *devname, int fd, int quiet, char *backup_file,

test

@@ -21,6 +21,8 @@ fi
 
 # assume md0, md1, md2 exist in /dev
 md0=/dev/md0 md1=/dev/md1 md2=/dev/md2
+mdp0=/dev/md_d0
+mdp1=/dev/md_d1
 
 # We test mdadm on loop-back block devices.
 # dir for storing files should be settable by command line maybe

tests/07autodetect

@@ -0,0 +1,25 @@
+
+#
+# Test in-kernel autodetect.
+# Create a partitionable array on each of two devices,
+# put a partition on each, create an array, and see if we can
+# use autodetect to restart the array.
+
+mdadm -CR $mdp0 -l0 -f -n1 $dev0
+mdadm -CR $mdp1 -l0 -f -n1 $dev1
+sfdisk $mdp0 >&2 << END
+,,FD
+END
+sfdisk $mdp1 >&2 << END
+,,FD
+END
+mdadm -CR $md0 -l1 -n2 ${mdp0}p1 ${mdp1}p1
+check resync
+check raid1
+check wait
+mdadm -S $md0
+mdadm --auto-detect
+check raid1
+
+mdadm -Ss
+exit 0