Bug#827412: multipath-tools: /dev/mapper device files not removed when partition is removed

Andrew Patterson andrew.patterson at hpe.com
Wed Jun 15 21:31:32 UTC 2016


Package: multipath-tools
Version: 0.6.1

Multipath-tools creates device files in /dev/mapper for both the block
device and its partitions. The partition device file use the format
/dev/mapper/<mpath-device>-partX, where X is the partition number.

Example:

Configuration details:

Testing on an amd64 system running sid with
multipath-tools/kpartx_0.6.1-3 from experimental. We have 8 FC LUNs
with 4 paths each. The kernel version is 4.6.0-1-amd64.

With the following /etc/multipath.conf file:

defaults {
	user_friendly_names "yes"
}

blacklist {
	device {
		vendor "HP"
		product "LOGICAL VOLUME"
}

Here are the devices used (the boot device is blacklisted):

# lsscsi
[0:0:0:0]    storage HP       P244br           2.52  -        
[0:1:0:0]    disk    HP       LOGICAL VOLUME   2.52  /dev/sda 
[1:0:0:0]    disk    3PARdata VV               3212  /dev/sdj 
[1:0:0:1]    disk    3PARdata VV               3212  /dev/sdl 
[1:0:0:2]    disk    3PARdata VV               3212  /dev/sdn 
[1:0:0:3]    disk    3PARdata VV               3212  /dev/sdq 
[1:0:0:4]    disk    3PARdata VV               3212  /dev/sdr 
[1:0:0:5]    disk    3PARdata VV               3212  /dev/sdt 
[1:0:0:6]    disk    3PARdata VV               3212  /dev/sdv 
[1:0:0:7]    disk    3PARdata VV               3212  /dev/sdx 
[1:0:0:254]  enclosu 3PARdata SES              3212  -        
[1:0:1:0]    disk    3PARdata VV               3212  /dev/sdz 
[1:0:1:1]    disk    3PARdata VV               3212  /dev/sdaa
[1:0:1:2]    disk    3PARdata VV               3212  /dev/sdab
[1:0:1:3]    disk    3PARdata VV               3212  /dev/sdac
[1:0:1:4]    disk    3PARdata VV               3212  /dev/sdad
[1:0:1:5]    disk    3PARdata VV               3212  /dev/sdae
[1:0:1:6]    disk    3PARdata VV               3212  /dev/sdaf
[1:0:1:7]    disk    3PARdata VV               3212  /dev/sdag
[1:0:1:254]  enclosu 3PARdata SES              3212  -        
[2:0:0:0]    disk    3PARdata VV               3212  /dev/sdb 
[2:0:0:1]    disk    3PARdata VV               3212  /dev/sdc 
[2:0:0:2]    disk    3PARdata VV               3212  /dev/sdd 
[2:0:0:3]    disk    3PARdata VV               3212  /dev/sde 
[2:0:0:4]    disk    3PARdata VV               3212  /dev/sdf 
[2:0:0:5]    disk    3PARdata VV               3212  /dev/sdg 
[2:0:0:6]    disk    3PARdata VV               3212  /dev/sdh 
[2:0:0:7]    disk    3PARdata VV               3212  /dev/sdi 
[2:0:0:254]  enclosu 3PARdata SES              3212  -        
[2:0:1:0]    disk    3PARdata VV               3212  /dev/sdk 
[2:0:1:1]    disk    3PARdata VV               3212  /dev/sdm 
[2:0:1:2]    disk    3PARdata VV               3212  /dev/sdo 
[2:0:1:3]    disk    3PARdata VV               3212  /dev/sdp 
[2:0:1:4]    disk    3PARdata VV               3212  /dev/sds 
[2:0:1:5]    disk    3PARdata VV               3212  /dev/sdu 
[2:0:1:6]    disk    3PARdata VV               3212  /dev/sdw 
[2:0:1:7]    disk    3PARdata VV               3212  /dev/sdy 
[2:0:1:254]  enclosu 3PARdata SES              3212  - 

And the following multipath -l output:

# multipath -l
mpathe (360002ac00000000000001908000028be) dm-4 3PARdata,VV
size=1.0G features='0' hwhandler='0' wp=rw
`-+- policy='service-time 0' prio=0 status=active
  |- 1:0:0:4 sdr  65:16  active undef running
  |- 1:0:1:4 sdad 65:208 active undef running
  |- 2:0:0:4 sdf  8:80   active undef running
  `- 2:0:1:4 sds  65:32  active undef running
mpathd (360002ac00000000000001907000028be) dm-3 3PARdata,VV
size=1.0G features='0' hwhandler='0' wp=rw
`-+- policy='service-time 0' prio=0 status=active
  |- 1:0:0:3 sdq  65:0   active undef running
  |- 1:0:1:3 sdac 65:192 active undef running
  |- 2:0:0:3 sde  8:64   active undef running
  `- 2:0:1:3 sdp  8:240  active undef running
mpathc (360002ac00000000000001906000028be) dm-2 3PARdata,VV
size=1.0G features='0' hwhandler='0' wp=rw
`-+- policy='service-time 0' prio=0 status=active
  |- 1:0:0:2 sdn  8:208  active undef running
  |- 1:0:1:2 sdab 65:176 active undef running
  |- 2:0:0:2 sdd  8:48   active undef running
  `- 2:0:1:2 sdo  8:224  active undef running
mpathb (360002ac00000000000001905000028be) dm-1 3PARdata,VV
size=1.0G features='0' hwhandler='0' wp=rw
`-+- policy='service-time 0' prio=0 status=active
  |- 1:0:0:1 sdl  8:176  active undef running
  |- 1:0:1:1 sdaa 65:160 active undef running
  |- 2:0:0:1 sdc  8:32   active undef running
  `- 2:0:1:1 sdm  8:192  active undef running
mpatha (360002ac00000000000001904000028be) dm-0 3PARdata,VV
size=1.0G features='0' hwhandler='0' wp=rw
`-+- policy='service-time 0' prio=0 status=active
  |- 1:0:0:0 sdj  8:144  active undef running
  |- 1:0:1:0 sdz  65:144 active undef running
  |- 2:0:0:0 sdb  8:16   active undef running
  `- 2:0:1:0 sdk  8:160  active undef running
mpathh (360002ac0000000000000190b000028be) dm-7 3PARdata,VV
size=1.0G features='0' hwhandler='0' wp=rw
`-+- policy='service-time 0' prio=0 status=active
  |- 1:0:0:7 sdx  65:112 active undef running
  |- 1:0:1:7 sdag 66:0   active undef running
  |- 2:0:0:7 sdi  8:128  active undef running
  `- 2:0:1:7 sdy  65:128 active undef running
mpathg (360002ac0000000000000190a000028be) dm-6 3PARdata,VV
size=1.0G features='0' hwhandler='0' wp=rw
`-+- policy='service-time 0' prio=0 status=active
  |- 1:0:0:6 sdv  65:80  active undef running
  |- 1:0:1:6 sdaf 65:240 active undef running
  |- 2:0:0:6 sdh  8:112  active undef running
  `- 2:0:1:6 sdw  65:96  active undef running
mpathf (360002ac00000000000001909000028be) dm-5 3PARdata,VV
size=1.0G features='0' hwhandler='0' wp=rw
`-+- policy='service-time 0' prio=0 status=active
  |- 1:0:0:5 sdt  65:48  active undef running
  |- 1:0:1:5 sdae 65:224 active undef running
  |- 2:0:0:5 sdg  8:96   active undef running
  `- 2:0:1:5 sdu  65:64  active undef running

With the following device files in /dev/mapper:

# ls -l /dev/mapper
total 0
crw------- 1 root root 10, 236 Jun 14 13:28 control
lrwxrwxrwx 1 root root       7 Jun 14 13:53 mpatha -> ../dm-0
lrwxrwxrwx 1 root root       7 Jun 14 13:53 mpathb -> ../dm-1
lrwxrwxrwx 1 root root       7 Jun 14 13:53 mpathc -> ../dm-2
lrwxrwxrwx 1 root root       7 Jun 14 13:53 mpathd -> ../dm-3
lrwxrwxrwx 1 root root       7 Jun 14 13:53 mpathe -> ../dm-4
lrwxrwxrwx 1 root root       7 Jun 14 13:53 mpathf -> ../dm-5
lrwxrwxrwx 1 root root       7 Jun 14 13:53 mpathg -> ../dm-6
lrwxrwxrwx 1 root root       7 Jun 14 13:53 mpathh -> ../dm-7

We now create and remove a partition using fdisk.

# fdisk /dev/mapper/mpatha

Welcome to fdisk (util-linux 2.28).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): n
Partition number (1-128, default 1): 
First sector (34-2097118, default 32768): 
Last sector, +sectors or +size{K,M,G,T,P} (32768-2097118, default 2097118): 

Created a new partition 1 of type 'Linux filesystem' and of size 1008 MiB.

Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Re-reading the partition table failed.: Invalid argument

The kernel still uses the old table. The new table will be used at the next reboot or after you run partprobe(8) or kpartx(8).

Resulting in:

# ls -l /dev/mapper/mpatha*
lrwxrwxrwx 1 root root 7 Jun 15 14:58 /dev/mapper/mpatha -> ../dm-0
lrwxrwxrwx 1 root root 7 Jun 15 14:58 /dev/mapper/mpatha-part1 -> ../dm-8
# ls -l /dev/disk/by-id/scsi-mpatha*
lrwxrwxrwx 1 root root 10 Jun 15 15:02 /dev/disk/by-id/scsi-mpatha -> ../../dm-0
lrwxrwxrwx 1 root root 10 Jun 15 15:02 /dev/disk/by-id/scsi-mpatha-part1 -> ../../dm-2

Now when I remove this partition:

# fdisk /dev/mapper/mpatha

Welcome to fdisk (util-linux 2.28).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): d
Selected partition 1
Partition 1 has been deleted.

Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Re-reading the partition table failed.: Invalid argument

The kernel still uses the old table. The new table will be used at the next reboot or after you run partprobe(8) or kpartx(8).

The /dev/mapper partition device file is still present:

# ls -l /dev/mapper/mpatha*
lrwxrwxrwx 1 root root 7 Jun 15 15:05 /dev/mapper/mpatha -> ../dm-0
lrwxrwxrwx 1 root root 7 Jun 15 15:02 /dev/mapper/mpatha-part1 -> ../dm-2
# ls -l /dev/disk/by-id/scsi-mpatha
lrwxrwxrwx 1 root root 10 Jun 15 15:13 /dev/disk/by-id/scsi-mpatha -> ../../dm-2

Note that the /dev/disk/by-path file is gone while the /dev/mapper
device file remains.

Here is the output from udevadm monitor while removing the partition:

KERNEL[155.958774] change   /devices/virtual/block/dm-2 (block)
UDEV  [155.986198] change   /devices/virtual/block/dm-2 (block)

and /proc/partitions indicates that the partition is gone:

# cat /proc/partitions  | grep -- dm-
 254        0    1048576 dm-0
 254        1    1048576 dm-1
 254        2    1048576 dm-2
 254        3    1048576 dm-3
 254        4    1048576 dm-4
 254        5    1048576 dm-5
 254        6    1048576 dm-6
 254        7    1048576 dm-7
 254        8    1032175 dm-8

This seems to work correctly when using parted, e.g.,

# ls -l /dev/mapper/mpathb*
lrwxrwxrwx 1 root root 7 Jun 15 15:19 /dev/mapper/mpathb -> ../dm-3
lrwxrwxrwx 1 root root 7 Jun 15 15:19 /dev/mapper/mpathb1 -> ../dm-9
# ls -l /dev/disk/by-id/scsi-mpathb*
lrwxrwxrwx 1 root root 10 Jun 15 15:19 /dev/disk/by-id/scsi-mpathb -> ../../dm-3
lrwxrwxrwx 1 root root 10 Jun 15 15:19 /dev/disk/by-id/scsi-mpathb1 -> ../../dm-9

# parted /dev/mapper/mpathb
GNU Parted 3.2
Using /dev/mapper/mpathb
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) rm 1
(parted) quit                                                             
Information: You may need to update /etc/fstab.

# ls -l /dev/mapper/mpathb*                            
lrwxrwxrwx 1 root root 7 Jun 15 15:22 /dev/mapper/mpathb -> ../dm-3
# ls -l /dev/disk/by-id/scsi-mpathb*
lrwxrwxrwx 1 root root 10 Jun 15 15:22 /dev/disk/by-id/scsi-mpathb -> ../../dm-3

Here is the output for udevadm monitor when deleting the parted partition:

KERNEL[735.524037] change   /devices/virtual/block/dm-9 (block)
KERNEL[735.524470] change   /devices/virtual/block/dm-3 (block)
UDEV  [735.540771] change   /devices/virtual/block/dm-9 (block)
KERNEL[735.543465] add      /devices/virtual/bdi/254:10 (bdi)
KERNEL[735.543534] add      /devices/virtual/block/dm-10 (block)
UDEV  [735.543727] add      /devices/virtual/bdi/254:10 (bdi)
KERNEL[735.543795] remove   /devices/virtual/block/dm-10 (block)
UDEV  [735.548136] add      /devices/virtual/block/dm-10 (block)
UDEV  [735.548265] remove   /devices/virtual/block/dm-10 (block)
KERNEL[735.556226] remove   /devices/virtual/bdi/254:10 (bdi)
UDEV  [735.556447] remove   /devices/virtual/bdi/254:10 (bdi)
UDEV  [735.573117] change   /devices/virtual/block/dm-3 (block)
KERNEL[739.475199] change   /devices/virtual/block/dm-9 (block)
UDEV  [739.517662] change   /devices/virtual/block/dm-9 (block)
KERNEL[739.518452] remove   /devices/virtual/block/dm-9 (block)
KERNEL[739.518643] remove   /devices/virtual/block/dm-9 (block)
UDEV  [739.521683] remove   /devices/virtual/block/dm-9 (block)
UDEV  [739.521786] remove   /devices/virtual/block/dm-9 (block)
KERNEL[739.532256] remove   /devices/virtual/bdi/254:9 (bdi)
UDEV  [739.532847] remove   /devices/virtual/bdi/254:9 (bdi)
KERNEL[744.961662] change   /devices/virtual/block/dm-3 (block)
UDEV  [744.981294] change   /devices/virtual/block/dm-3 (block)

Note, we are now getting events for the partition as well as the parent
block device.

Note that when using parted, we get a different partition device file
-- /dev/mapper/mpathb1 than that created with fdisk. This difference
is discussed in bug
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=827308/

I have seen this same issue in earlier versions of multipath-tools.

-- 
Andrew Patterson
Hewlett-Packard Enterprise



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