[Bug 1486370] Re: ISST-LTE: not all mpath device files are symbol link

[Mathieu Trudel-Lapierre]

Could you please verify that you're not seeing this issue on 16.04? It
looks like the patch found should solve this, but it's hard to verify
given that this is very dependent on the speed of the system on which
multipath-tools run, as well as how fast udev can run, scan devices,
etc.

** Description changed:

+ [Impact]
+ Minimal impact, this is limited to aesthetic issues; devices should if possible all be actual block device nodes rather than symlinks.
+ 
+ [Test case]
+ 1) ls -l /dev/mapper
+ 2) Reboot, try again.
+ 
+ [Regression potential]
+ Timing issues may cause delays in generating device nodes or symlinks due to the need for multipath-tools, device-mapper and udev to synchronize.
+ 
+ ---
+ 
  == Comment: #0 - Ping Tian Han <pthan at cn.ibm.com> - 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 
+ % 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 
+ % 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 Han/pthan at cn.ibm.com,   Chanh H
+ Nguyen/chnguyen at us.ibm.com
  
-  
- Contact Information = Ping Tian Han/pthan at cn.ibm.com, 	Chanh H Nguyen/chnguyen at us.ibm.com 
-  
  ---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 
-  
+ 
+ Machine Type = na
+ 
  ---Steps to Reproduce---
-  1. install ubuntu on onyxlp2, which has mpath device
+  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 tool common name: na
+ 
+ The userspace tool has the following bit modes: 64-bit
  
  Userspace rpm: na
  
- Userspace tool obtained from project website:  na 
-  
+ Userspace tool obtained from project website:  na
+ 
  == Comment: #6 - Mauricio Faria De Oliveira <mauricfo at br.ibm.com> - 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 <mauricfo at br.ibm.com> - 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.

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Title:
  ISST-LTE: not all mpath device files are symbol link

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