Adjust major number testing to allow for extended minor number in 2.6.28

From 2.6.28, normal md device will be able to have partitions.  These
partitions will have a different major number.  Sometimes mdadm tests
the major number and so can get confused.
Change these tests to test against get_mdp_major().  mdp does not use
extended minor number and so this test will always be accurate.

Also use /sys/dev links to map major/minor to devnum in sysfs.

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

1 files changed, 26 insertions, 3 deletions

diff --git a/sysfs.c b/sysfs.c
index 0255f882..6350242b 100644
--- a/sysfs.c
+++ b/sysfs.c
@@ -83,11 +83,34 @@ struct mdinfo *sysfs_read(int fd, int devnum, unsigned long options)
  		if (fstat(fd, &stb)) return NULL;
 		if (ioctl(fd, RAID_VERSION, &vers) != 0)
 			return NULL;
-		if (major(stb.st_rdev)==9)
+		if (major(stb.st_rdev) == MD_MAJOR)
 			sprintf(sra->sys_name, "md%d", (int)minor(stb.st_rdev));
-		else
+		else if (major(stb.st_rdev) == get_mdp_major())
 			sprintf(sra->sys_name, "md_d%d",
 				(int)minor(stb.st_rdev)>>MdpMinorShift);
+		else {
+			/* must be an extended-minor partition. Look at the
+			 * /sys/dev/block/%d:%d link which must look like
+			 * ../../block/mdXXX/mdXXXpYY
+			 */
+			char path[30];
+			char link[200];
+			char *cp;
+			int n;
+			sprintf(path, "/sys/dev/block/%d:%d", major(stb.st_rdev),
+				minor(stb.st_rdev));
+			n = readlink(path, link, sizeof(link)-1);
+			if (n <= 0)
+				return NULL;
+			link[n] = 0;
+			cp = strrchr(link, '/');
+			if (cp) *cp = 0;
+			cp = strchr(link, '/');
+			if (cp && strncmp(cp, "/md", 3) == 0)
+				strcpy(sra->sys_name, cp+1);
+			else
+				return NULL;
+		}
 	} else {
 		if (devnum >= 0)
 			sprintf(sra->sys_name, "md%d", devnum);
@@ -244,7 +267,7 @@ unsigned long long get_component_size(int fd)
 	char fname[50];
 	int n;
 	if (fstat(fd, &stb)) return 0;
-	if (major(stb.st_rdev) == 9)
+	if (major(stb.st_rdev) != get_mdp_major())
 		sprintf(fname, "/sys/block/md%d/md/component_size",
 			(int)minor(stb.st_rdev));
 	else