Bug 1509036

Summary: dm table not updated after automatic lvm segment merge
Product: Red Hat Enterprise Linux 7 Reporter: John Pittman <jpittman>
Component: lvm2Assignee: Zdenek Kabelac <zkabelac>
lvm2 sub component: Changing Logical Volumes QA Contact: cluster-qe <cluster-qe>
Status: CLOSED CURRENTRELEASE Docs Contact:
Severity: medium    
Priority: medium CC: agk, alex.wang, cmarthal, heinzm, jbrassow, jmagrini, loberman, mcsontos, msnitzer, nweddle, orion, prajnoha, tcleveng, zkabelac
Version: 7.4   
Target Milestone: rc   
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2020-04-20 15:09:59 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 1784876    

Description John Pittman 2017-11-02 18:51:34 UTC 
Description of problem:

The device-mapper table is not being updated after an automatic segment merge made possible by a pvmove.  It seems the on-disk metadata is updated, but not in the kernel.

Version-Release number of selected component (if applicable):

device-mapper-1.02.140-8.el7.x86_64
lvm2-2.02.171-8.el7.x86_64
kernel-3.10.0-693.2.2.el7.x86_64

Steps to Reproduce:

- Create volume group and span one logical volume across two PVs so that it has 2 segments:

[root@localhost ~]# vgcreate seg_vg /dev/sdb /dev/sdc
  Physical volume "/dev/sdb" successfully created.
  Physical volume "/dev/sdc" successfully created.
  Volume group "seg_vg" successfully created
  
[root@localhost ~]# lvcreate -n lv1 -l 200 seg_vg /dev/sdb:0-99 /dev/sdc:0-99
  Logical volume "lv1" created.

- Verify that we indeed have two segments, both in lvm and device-mapper:

[root@localhost ~]# lvs -o +devices,seg_pe_ranges
  LV   VG     Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert Devices        PE Ranges         
  root rhel   -wi-ao----  <6.20g                                                     /dev/sda2(205) /dev/sda2:205-1790
  swap rhel   -wi-ao---- 820.00m                                                     /dev/sda2(0)   /dev/sda2:0-204   
  lv1  seg_vg -wi-ao---- 800.00m                                                     /dev/sdb(0)    /dev/sdb:0-99     <==== segment 1
  lv1  seg_vg -wi-ao---- 800.00m                                                     /dev/sdc(0)    /dev/sdc:0-99     <==== segment 2
  
[root@localhost ~]# dmsetup table seg_vg-lv1
0 819200 linear 8:16 2048          <=== segment 1
819200 819200 linear 8:32 2048     <=== segment 2

- Move the segment in sdc to a position directly after the sdb segment.  This will trigger the automatic merge of these segments:

[root@localhost ~]# pvmove /dev/sdc:0-99 /dev/sdb:100-199
  /dev/sdc: Moved: 2.00%
  /dev/sdc: Moved: 100.00%
  
- Verify lvm shows one segment and unknown (X) attributes:

[root@localhost ~]# lvs -o +devices,seg_pe_ranges
  WARNING: Cannot find matching striped segment for seg_vg/lv1.
  LV   VG     Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert Devices        PE Ranges         
  root rhel   -wi-ao----  <6.20g                                                     /dev/sda2(205) /dev/sda2:205-1790
  swap rhel   -wi-ao---- 820.00m                                                     /dev/sda2(0)   /dev/sda2:0-204   
  lv1  seg_vg -wi-XX--X- 800.00m                                                     /dev/sdb(0)    /dev/sdb:0-199      <==== 1 segment

- Verify device-mapper shows 2 segments:

[root@localhost ~]# dmsetup table seg_vg-lv1
0 819200 linear 8:16 2048                    <==== 1 segment
819200 819200 linear 8:16 821248             <==== 2 segments

- Remediate by refreshing the volume group:

[root@localhost ~]# vgchange --refresh seg_vg

- Verify lvm and device-mapper are consistent:

[root@localhost ~]# lvs -o +devices,seg_pe_ranges
  LV   VG     Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert Devices        PE Ranges         
  root rhel   -wi-ao----  <6.20g                                                     /dev/sda2(205) /dev/sda2:205-1790
  swap rhel   -wi-ao---- 820.00m                                                     /dev/sda2(0)   /dev/sda2:0-204   
  lv1  seg_vg -wi-ao---- 800.00m                                                     /dev/sdb(0)    /dev/sdb:0-199    
  
[root@localhost ~]# dmsetup table seg_vg-lv1
0 1638400 linear 8:16 2048

Actual results:

kernel state is not refreshed

Expected results:

kernel state should be consistent w/ lvm with no intervention after the merge
Comment 6 Zdenek Kabelac 2020-01-17 14:13:53 UTC 
This was already fixed in  2.02.177  (upstream commit c489dd2e1764216de07be80d36b1025fb4f6fc85)
Comment 9 Corey Marthaler 2020-04-15 17:00:22 UTC 
# This appears to work effortlessly in the current rhel7.9 rpms, no need for the vgchange --refresh. Adding ack, but feel free to just close WORKSFORME.

[root@mckinley-01 ~]# vgcreate seg_vg /dev/mapper/mpatha2 /dev/mapper/mpathb2
  Volume group "seg_vg" successfully created
[root@mckinley-01 ~]# lvcreate -n lv1 -l 200 seg_vg /dev/mapper/mpatha2:0-99 /dev/mapper/mpathb2:0-99
  Logical volume "lv1" created.

[root@mckinley-01 ~]# lvs -o +devices,seg_pe_ranges
  LV   VG               Attr       LSize    Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert Devices                PE Ranges               
  lv1  seg_vg           -wi-a-----  800.00m                                                     /dev/mapper/mpatha2(0) /dev/mapper/mpatha2:0-99
  lv1  seg_vg           -wi-a-----  800.00m                                                     /dev/mapper/mpathb2(0) /dev/mapper/mpathb2:0-99
[root@mckinley-01 ~]#  dmsetup table seg_vg-lv1
0 819200 linear 253:4 65543
819200 819200 linear 253:8 65543
[root@mckinley-01 ~]# pvmove /dev/mapper/mpathb2:0-99 /dev/mapper/mpatha2:100-199
  /dev/mapper/mpathb2: Moved: 0.00%
  /dev/mapper/mpathb2: Moved: 100.00%

# This appears to work effortlessly in the current rhel7.9 rpms, no need for the vgchange --refresh
[root@mckinley-01 ~]# lvs -o +devices,seg_pe_ranges
  LV   VG               Attr       LSize    Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert Devices                PE Ranges                
  lv1  seg_vg           -wi-a-----  800.00m                                                     /dev/mapper/mpatha2(0) /dev/mapper/mpatha2:0-199
[root@mckinley-01 ~]#  dmsetup table seg_vg-lv1
0 1638400 linear 253:4 65543

[root@mckinley-01 ~]# vgchange --refresh seg_vg
[root@mckinley-01 ~]# lvs -o +devices,seg_pe_ranges
  LV   VG               Attr       LSize    Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert Devices                PE Ranges                
  lv1  seg_vg           -wi-a-----  800.00m                                                     /dev/mapper/mpatha2(0) /dev/mapper/mpatha2:0-199