From: Peter Rajnoha <prajnoha@redhat.com>
Date: Thu, 20 Sep 2012 07:39:57 +0000 (+0200)
Subject: lib/sysfs: fix sysfs_devname_to_devno for dm partitions
X-Git-Tag: v2.23-rc1~685
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=857db7f53c03ca363de50682a4958ae9f1f77391;p=thirdparty%2Futil-linux.git

lib/sysfs: fix sysfs_devname_to_devno for dm partitions

Partitions mapped by device-mapper are not like real partitions where
there's a /sys/block/<parent>/<name>/dev sysfs path. We need to look
at /sys/block/<name>/dev like we do for any other non-partition devices.
The mapped partition is not found otherwise.

For example, this bug shows up in lsblk while specifying a device
on command line while that device is a dm mapping over a partition:
$lsblk
NAME             MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda                8:0    0  128M  0 disk
`-test (dm-0)    253:0    0  128M  0 dm
  `-test1 (dm-1) 253:1    0  127M  0 part

Before this patch:
$lsblk /dev/mapper/test1
lsblk: dm-1: unknown device name

With this patch:
$lsblk /dev/mapper/test1
NAME         MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
test1 (dm-1) 253:1    0  127M  0 part
---

diff --git a/lib/sysfs.c b/lib/sysfs.c
index d1eccb585c..1384acda61 100644
--- a/lib/sysfs.c
+++ b/lib/sysfs.c
@@ -58,7 +58,7 @@ dev_t sysfs_devname_to_devno(const char *name, const char *parent)
 			name += 5;	/* unaccesible, or not node in /dev */
 	}
 
-	if (!dev && parent) {
+	if (!dev && parent && strncmp("dm-", name, 3)) {
 		/*
 		 * Create path to /sys/block/<parent>/<name>/dev
 		 */