On Tue, 2020-12-08 at 12:04 +0100, Christoph Hellwig wrote:

can you send me details of your device mapper setup, e.g. which targets
are used, are they used on top of whole device or partitions.  Do you
use partitions on top of the dm devices?  Are any other stacking devices
involved?

It is a standard RHEL8 installation using "autopart", so I don't think it uses
any particular targets. It is just a plain LVM backed by ahci (sda2 and sdb1.
Some other affected systems use smartpqi/NVM). The kernel has only dm-mirror
enabled but I don't think it uses it anyway.

# grep -i _DM_ .config | grep -v ^#
CONFIG_BLK_DEV_DM_BUILTIN=y
CONFIG_DM_MIRROR=m
CONFIG_DM_UEVENT=y

# lvdisplay
  --- Logical volume ---
  LV Path                /dev/rhel_ibm-p9wr-10/home
  LV Name                home
  VG Name                rhel_ibm-p9wr-10
  LV UUID                ETS2PI-yedc-7AJ6-NUP2-uAYD-6api-bp9nqv
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                <3.57 TiB
  Current LE             934662
  Segments               2
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           254:2
   
  --- Logical volume ---
  LV Path                /dev/rhel_ibm-p9wr-10/root
  LV Name                root
  VG Name                rhel_ibm-p9wr-10
  LV UUID                ozakb8-2DWE-YBI9-4nnc-gwk8-mMuf-s3EPsB
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                70.00 GiB
  Current LE             17920
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           254:0

# pvdisplay 
  --- Physical volume ---
  PV Name               /dev/sda2
  VG Name               rhel_ibm-p9wr-10
  PV Size               <1.82 TiB / not usable 4.00 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              476675
  Free PE               0
  Allocated PE          476675
  PV UUID               0Tv2Az-vx7S-HLPd-66Ff-tH6H-dte1-tjSZ7i
   
  --- Physical volume ---
  PV Name               /dev/sdb1
  VG Name               rhel_ibm-p9wr-10
  PV Size               <1.82 TiB / not usable 4.00 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              476931
  Free PE               0
  Allocated PE          476931
  PV UUID               4LfZJN-NxbJ-39OC-VBKP-jv5P-hciK-BOdiML

# lsblk 
NAME                        MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda                           8:0    1  1.8T  0 disk 
├─sda1                        8:1    1    1G  0 part /boot
└─sda2                        8:2    1  1.8T  0 part 
  ├─rhel_ibm--p9wr--10-root 254:0    0   70G  0 lvm  /
  └─rhel_ibm--p9wr--10-home 254:2    0  3.6T  0 lvm  /home
sdb                           8:16   1  1.8T  0 disk 
└─sdb1                        8:17   1  1.8T  0 part 
  └─rhel_ibm--p9wr--10-home 254:2    0  3.6T  0 lvm  /home