Comment 0 for bug 1486370

== Comment: #0 - Ping Tian Han <email address hidden> - 2015-07-21 23:38:48 ==
---Problem Description---
Some mpath devices in /dev/mapper are symbol links to /dev/dm-<n>, but there are exceptions:

% ls -l /dev/mapper
total 0
crw------- 1 root root 10, 236 Jul 21 20:46 control
lrwxrwxrwx 1 root root 7 Jul 21 20:46 mpath0 -> ../dm-0
brw------- 1 root root 252, 4 Jul 21 20:46 mpath0-part1
brw------- 1 root root 252, 6 Jul 21 20:46 mpath0-part2
brw------- 1 root root 252, 7 Jul 21 20:46 mpath0-part3
lrwxrwxrwx 1 root root 7 Jul 21 20:46 mpath1 -> ../dm-1
brw-rw---- 1 root disk 252, 2 Jul 21 20:46 mpath2
lrwxrwxrwx 1 root root 7 Jul 21 20:46 mpath3 -> ../dm-3
lrwxrwxrwx 1 root root 7 Jul 21 20:46 mpath4 -> ../dm-5

mpath2 isn't a symbol link.

% sudo dmestup info mpath2
sudo: dmestup: command not found
% sudo dmsetup info mpath2
Name: mpath2
State: ACTIVE
Read Ahead: 256
Tables present: LIVE
Open count: 0
Event number: 4
Major, minor: 252, 2
Number of targets: 1
UUID: mpath-36005076304ffc69f0000000000000469

% sudo dmsetup info /dev/dm-2
Name: mpath2
State: ACTIVE
Read Ahead: 256
Tables present: LIVE
Open count: 0
Event number: 4
Major, minor: 252, 2
Number of targets: 1
UUID: mpath-36005076304ffc69f0000000000000469

Contact Information = Ping Tian <email address hidden>, Chanh H <email address hidden>

---uname output---
Linux onyxlp2 3.19.0-22-generic #22~14.04.1-Ubuntu SMP Wed Jun 17 10:03:39 UTC 2015 ppc64le ppc64le ppc64le GNU/Linux

Machine Type = na

---Steps to Reproduce---
 1. install ubuntu on onyxlp2, which has mpath device
2. ls /dev/mapper, see some mpath device file isn't symbol link

Userspace tool common name: na

The userspace tool has the following bit modes: 64-bit

Userspace rpm: na

Userspace tool obtained from project website: na

== Comment: #6 - Mauricio Faria De Oliveira <email address hidden> - 2015-08-18 12:33:17 ==
This shouldn't be a problem at all.
Either symlinks to the dm devices or block devices which refer to them directly (via major:minor number) will work.

It isn't ideal, though.

== Comment: #7 - Mauricio Faria De Oliveira <email address hidden> - 2015-08-18 12:35:34 ==
BTW, that expectation is per the SRU policy.

And the problem cause is likely a race involving udev rules (multipath & kpartx), and possibly multipathd.