Also, I am having trouble reproducing the problem. Any chance that you can help
make a testcase?

I made a 5G disk, made a PV, VG and LV, and then made a btrfs filesystem. But
I could never get the udev trigger to actually occur to rename the device
links.

Any ideas?

$ uname -rv
5.15.0-127-generic #137-Ubuntu SMP Fri Nov 8 15:21:01 UTC 2024
$ lsblk
NAME    MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
vda     252:0    0   10G  0 disk 
├─vda1  252:1    0  9.9G  0 part /
├─vda14 252:14   0    4M  0 part 
└─vda15 252:15   0  106M  0 part /boot/efi
vdb     252:16   0  372K  0 disk 
vdc     252:32   0    5G  0 disk 
$ sudo pvcreate /dev/vdc
  Physical volume "/dev/vdc" successfully created.
$ sudo vgcreate vdc /dev/vdc
  /dev/vdc: already exists in filesystem
  Run `vgcreate --help' for more information.
$ sudo vgcreate VG0 /dev/vdc
  Volume group "VG0" successfully created
$ sudo lvcreate -L5G^Cn data0 vg0
$ sudo lvcreate -n LV0 -l 100%FREE VG0
  Logical volume "LV0" created.
$ sudo mkfs.btrfs /dev/VG0/LV0 
btrfs-progs v5.16.2
See http://btrfs.wiki.kernel.org for more information.

Performing full device TRIM /dev/VG0/LV0 (5.00GiB) ...
NOTE: several default settings have changed in version 5.15, please make sure
      this does not affect your deployments:
      - DUP for metadata (-m dup)
      - enabled no-holes (-O no-holes)
      - enabled free-space-tree (-R free-space-tree)

Label:              (null)
UUID:               ff124bfe-c58d-4112-8b37-6466e1ddedc9
Node size:          16384
Sector size:        4096
Filesystem size:    5.00GiB
Block group profiles:
  Data:             single            8.00MiB
  Metadata:         DUP             256.00MiB
  System:           DUP               8.00MiB
SSD detected:       no
Zoned device:       no
Incompat features:  extref, skinny-metadata, no-holes
Runtime features:   free-space-tree
Checksum:           crc32c
Number of devices:  1
Devices:
   ID        SIZE  PATH
    1     5.00GiB  /dev/VG0/LV0

$ sudo mount /dev/VG0/LV0 /m^C
$ sudo mkdir /mnt/a
$ sudo mkdir /mnt/b
$ sudo mkdir /mnt/c
$ sudo mount /dev/VG0/LV0 /mnt/a
$ sudo mount /dev/VG0/LV0 /mnt/b
$ sudo mount /dev/VG0/LV0 /mnt/c
$ lsblk
NAME      MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
loop0       7:0    0 63.7M  1 loop /snap/core20/2434
loop1       7:1    0 89.4M  1 loop /snap/lxd/31333
loop2       7:2    0 44.3M  1 loop /snap/snapd/23258
vda       252:0    0   10G  0 disk 
├─vda1    252:1    0  9.9G  0 part /
├─vda14   252:14   0    4M  0 part 
└─vda15   252:15   0  106M  0 part /boot/efi
vdb       252:16   0  372K  0 disk 
vdc       252:32   0    5G  0 disk 
└─VG0-LV0 253:0    0    5G  0 lvm  /mnt/c
                                   /mnt/b
                                   /mnt/a
$ grep /mnt /proc/mounts
/dev/mapper/VG0-LV0 /mnt/a btrfs rw,relatime,space_cache=v2,subvolid=5,subvol=/ 
0 0
/dev/mapper/VG0-LV0 /mnt/b btrfs rw,relatime,space_cache=v2,subvolid=5,subvol=/ 
0 0
/dev/mapper/VG0-LV0 /mnt/c btrfs rw,relatime,space_cache=v2,subvolid=5,subvol=/ 
0 0

$ sudo apt install linux-image-5.15.0-136-generic linux-
modules-5.15.0-136-generic linux-modules-extra-5.15.0-136-generic linux-
headers-5.15.0-136-generic

$ uname -rv
5.15.0-136-generic #147-Ubuntu SMP Sat Mar 15 15:53:30 UTC 2025
$ ls /mnt
a  b  c
$ sudo mount /dev/VG0/LV0 /mnt/a
$ sudo mount /dev/VG0/LV0 /mnt/b
$ sudo mount /dev/VG0/LV0 /mnt/c
$ lsblk
NAME      MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
loop0       7:0    0 63.7M  1 loop /snap/core20/2434
loop1       7:1    0 89.4M  1 loop /snap/lxd/31333
loop2       7:2    0 44.3M  1 loop /snap/snapd/23258
vda       252:0    0   10G  0 disk 
├─vda1    252:1    0  9.9G  0 part /
├─vda14   252:14   0    4M  0 part 
└─vda15   252:15   0  106M  0 part /boot/efi
vdb       252:16   0  372K  0 disk 
vdc       252:32   0    5G  0 disk 
└─VG0-LV0 253:0    0    5G  0 lvm  /mnt/c
                                   /mnt/b
                                   /mnt/a
$ grep /mnt /proc/mounts
/dev/mapper/VG0-LV0 /mnt/a btrfs rw,relatime,space_cache=v2,subvolid=5,subvol=/ 
0 0
/dev/mapper/VG0-LV0 /mnt/b btrfs rw,relatime,space_cache=v2,subvolid=5,subvol=/ 
0 0
/dev/mapper/VG0-LV0 /mnt/c btrfs rw,relatime,space_cache=v2,subvolid=5,subvol=/ 
0 0
$ sudo touch /dev/mapper/VG0-LV0
$ grep /mnt /proc/mounts
/dev/mapper/VG0-LV0 /mnt/a btrfs rw,relatime,space_cache=v2,subvolid=5,subvol=/ 
0 0
/dev/mapper/VG0-LV0 /mnt/b btrfs rw,relatime,space_cache=v2,subvolid=5,subvol=/ 
0 0
/dev/mapper/VG0-LV0 /mnt/c btrfs rw,relatime,space_cache=v2,subvolid=5,subvol=/ 
0 0
$ sudo umount /mnt/a
$ sudo umount /mnt/b
$ sudo umount /mnt/c
$ sudo mount /dev/dm-0 /mnt/a
$ sudo mount /dev/dm-0 /mnt/b
$ sudo mount /dev/dm-0 /mnt/c
$ lsblk
NAME      MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
loop0       7:0    0 63.7M  1 loop /snap/core20/2434
loop1       7:1    0 89.4M  1 loop /snap/lxd/31333
loop2       7:2    0 44.3M  1 loop /snap/snapd/23258
vda       252:0    0   10G  0 disk 
├─vda1    252:1    0  9.9G  0 part /
├─vda14   252:14   0    4M  0 part 
└─vda15   252:15   0  106M  0 part /boot/efi
vdb       252:16   0  372K  0 disk 
vdc       252:32   0    5G  0 disk 
└─VG0-LV0 253:0    0    5G  0 lvm  /mnt/c
                                   /mnt/b
                                   /mnt/a
$ grep /mnt /proc/mounts
/dev/mapper/VG0-LV0 /mnt/a btrfs rw,relatime,space_cache=v2,subvolid=5,subvol=/ 
0 0
/dev/mapper/VG0-LV0 /mnt/b btrfs rw,relatime,space_cache=v2,subvolid=5,subvol=/ 
0 0
/dev/mapper/VG0-LV0 /mnt/c btrfs rw,relatime,space_cache=v2,subvolid=5,subvol=/ 
0 0
$ sudo udevadm control --reload-rules
$ sudo udevadm trigger
$ grep /mnt /proc/mounts
/dev/mapper/VG0-LV0 /mnt/a btrfs rw,relatime,space_cache=v2,subvolid=5,subvol=/ 
0 0
/dev/mapper/VG0-LV0 /mnt/b btrfs rw,relatime,space_cache=v2,subvolid=5,subvol=/ 
0 0
/dev/mapper/VG0-LV0 /mnt/c btrfs rw,relatime,space_cache=v2,subvolid=5,subvol=/ 
0 0
$ sudo -s
root@test-disk:/home/ubuntu# echo change > /sys/block/dm-0/uevent 
root@test-disk:/home/ubuntu# 
exit
$ grep /mnt /proc/mounts
/dev/mapper/VG0-LV0 /mnt/a btrfs rw,relatime,space_cache=v2,subvolid=5,subvol=/ 
0 0
/dev/mapper/VG0-LV0 /mnt/b btrfs rw,relatime,space_cache=v2,subvolid=5,subvol=/ 
0 0
/dev/mapper/VG0-LV0 /mnt/c btrfs rw,relatime,space_cache=v2,subvolid=5,subvol=/ 
0 0

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https://bugs.launchpad.net/bugs/2107516

Title:
  Ubuntu 22.04 kernel 5.15.0.136 changes /proc/mounts for btfs volumes

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