[PATCH] libdisk: use major/minor when calling dmsetup

[Eric Sandeen]

In RH bugzilla,
[Bug 471102] Error message seen during mkfs.xfs on multipath device
(unfortunately marked private) reports problems when making xfs
fileystems on multipath devices:

# mkfs -t xfs -f /dev/mpath/oramp4
dm_task_set_name: Device /dev/dm-12 not found
Command failed
dm_task_set_name: Device /dev/dm-12 not found
Command failed
meta-data=/dev/mpath/oramp4      isize=256    agcount=4, agsize=2359680 blks
...

This is because dmsetup takes a "name" which is sometimes, but not
always (I think) the same as the device name.

dmsetup also can take major/minor as arguments, so this may be
simpler at this point.

Signed-off-by: Eric Sandeen <sandeen at sandeen.net>
---


Index: xfsprogs-3.0.3/libdisk/dm.c
===================================================================
--- xfsprogs-3.0.3.orig/libdisk/dm.c
+++ xfsprogs-3.0.3/libdisk/dm.c
@@ -36,10 +36,11 @@ dm_get_subvol_stripe(
 {
 	int		count, stripes = 0, stripesize = 0;
 	int		dmpipe[2];
-	char		*dpath, *largv[4], tmppath[PATH_MAX];
+	char		*largv[7];
 	FILE		*stream;
 	long long	offset, size;
 	static char	*command = "table";	/* dmsetup table /dev/xxx */
+	char		major_str[4], minor_str[4];
 
 	if (!mnt_is_dm_subvol(sb->st_rdev))
 		return 0;
@@ -57,16 +58,15 @@ dm_get_subvol_stripe(
 		return 0;
 	}
 
-	if (!(dpath = realpath(dfile, tmppath))) {
-		fprintf(stderr,
-	_("Warning - device mapper device, but cannot resolve path %s: %s\n"),
-			dfile, strerror(errno));
-		return 0;
-	}
+	snprintf(major_str, 4, "%d", major(sb->st_rdev));
+	snprintf(minor_str, 4, "%d", minor(sb->st_rdev));
 
 	largv[1] = command;
-	largv[2] = dpath;
-	largv[3] = NULL;
+	largv[2] = "-j";
+	largv[3] = major_str;
+	largv[4] = "-m";
+	largv[5] = minor_str;
+	largv[6] = NULL;
 
 	/* Open pipe */
 	if (pipe(dmpipe) < 0) {