I think we need a udev plumbing expert, I've exhausted my udev
knowledge.
For older releases such as bionic we have one event:
UDEV [1304.304437] change /devices/virtual/block/bcache0 (block)
.ID_FS_TYPE_NEW=
ACTION=change
CACHED_LABEL=
CACHED_UUID=0192e0a7-9d8e-4771-9bb1-d730a2f66a9d
DEVLINKS=/dev/bcache/by-uuid/0192e0a7-9d8e-4771-9bb1-d730a2f66a9d
DEVNAME=/dev/bcache0
DEVPATH=/devices/virtual/block/bcache0
DEVTYPE=disk
DRIVER=bcache
ID_FS_TYPE=
MAJOR=251
MINOR=0
SEQNUM=4384
SUBSYSTEM=block
TAGS=:systemd:
USEC_INITIALIZED=1304237024
that creates the expected symlink.
---------
For focal, instead we get two events:
UDEV [2763.370729] change /devices/virtual/block/bcache0 (block)
ACTION=change
DEVPATH=/devices/virtual/block/bcache0
SUBSYSTEM=block
DRIVER=bcache
CACHED_UUID=1522715e-a390-40db-8d47-06fb728014e5
CACHED_LABEL=
DEVNAME=/dev/bcache0
DEVTYPE=disk
SEQNUM=5523
USEC_INITIALIZED=2763323504
.ID_FS_TYPE_NEW=
ID_FS_TYPE=
MAJOR=251
MINOR=0
DEVLINKS=/dev/bcache/by-uuid/1522715e-a390-40db-8d47-06fb728014e5
TAGS=:systemd:
KERNEL[2784.362374] change /devices/virtual/block/bcache0 (block)
ACTION=change
DEVPATH=/devices/virtual/block/bcache0
SUBSYSTEM=block
SYNTH_UUID=0
DEVNAME=/dev/bcache0
DEVTYPE=disk
SEQNUM=5524
MAJOR=251
MINOR=0
UDEV [2784.433618] change /devices/virtual/block/bcache0 (block)
ACTION=change
DEVPATH=/devices/virtual/block/bcache0
SUBSYSTEM=block
SYNTH_UUID=0
DEVNAME=/dev/bcache0
DEVTYPE=disk
SEQNUM=5524
USEC_INITIALIZED=2763323504
ID_FS_UUID=30b28bee-6a1e-423d-9d53-32c78ba5454a
ID_FS_UUID_ENC=30b28bee-6a1e-423d-9d53-32c78ba5454a
ID_FS_VERSION=1.0
ID_FS_TYPE=ext4
ID_FS_USAGE=filesystem
.ID_FS_TYPE_NEW=ext4
MAJOR=251
MINOR=0
DEVLINKS=/dev/disk/by-uuid/30b28bee-6a1e-423d-9d53-32c78ba5454a
TAGS=:systemd:
This performs:
pr 21 14:15:22 ubuntu-focal systemd-udevd[1870]: bcache0: Processing device
(SEQNUM=5523, ACTION=change)
Apr 21 14:15:22 ubuntu-focal systemd-udevd[1870]: bcache0: Removing watch
Apr 21 14:15:22 ubuntu-focal systemd-udevd[1870]: value '[dmi/id]sys_vendor' is
'QEMU'
Apr 21 14:15:22 ubuntu-focal systemd-udevd[1870]: value '[dmi/id]sys_vendor' is
'QEMU'
Apr 21 14:15:22 ubuntu-focal systemd-udevd[1870]: bcache0:
/usr/lib/udev/rules.d/60-persistent-storage.rules:109 Importing properties from
results of builtin command 'blkid'
Apr 21 14:15:22 ubuntu-focal systemd-udevd[1870]: bcache0: Probe /dev/bcache0
with raid and offset=0
Apr 21 14:15:22 ubuntu-focal systemd-udevd[1870]: bcache0:
/usr/lib/udev/rules.d/69-bcache.rules:16 Importing properties from results of
'probe-bcache -o udev /dev/bcache0'
Apr 21 14:15:22 ubuntu-focal systemd-udevd[1870]: bcache0: Starting
'probe-bcache -o udev /dev/bcache0'
Apr 21 14:15:22 ubuntu-focal systemd-udevd[1870]: Successfully forked off
'(spawn)' as PID 1912.
Apr 21 14:15:22 ubuntu-focal systemd-udevd[1870]: bcache0: Process
'probe-bcache -o udev /dev/bcache0' succeeded.
Apr 21 14:15:22 ubuntu-focal systemd-udevd[1870]: bcache0:
/usr/lib/udev/rules.d/69-bcache.rules:27 LINK
'bcache/by-uuid/1522715e-a390-40db-8d47-06fb728014e5'
Apr 21 14:15:22 ubuntu-focal systemd-udevd[1870]: bcache0: Handling device node
'/dev/bcache0', devnum=b251:0
Apr 21 14:15:22 ubuntu-focal systemd-udevd[1870]: bcache0: Preserve already
existing symlink '/dev/block/251:0' to '../bcache0'
Apr 21 14:15:22 ubuntu-focal systemd-udevd[1870]: bcache0: Creating symlink
'/dev/bcache/by-uuid/1522715e-a390-40db-8d47-06fb728014e5' to '../../bcache0'
Apr 21 14:15:22 ubuntu-focal systemd-udevd[1870]: bcache0: sd-device: Created
db file '/run/udev/data/b251:0' for '/devices/virtual/block/bcache0'
Apr 21 14:15:22 ubuntu-focal systemd-udevd[1870]: bcache0: Adding watch on
'/dev/bcache0'
Apr 21 14:15:22 ubuntu-focal systemd-udevd[1870]: bcache0: sd-device: Created
db file '/run/udev/data/b251:0' for '/devices/virtual/block/bcache0'
Apr 21 14:15:22 ubuntu-focal systemd-udevd[1870]: bcache0: Device (SEQNUM=5523,
ACTION=change) processed
Apr 21 14:15:22 ubuntu-focal systemd-udevd[1870]: bcache0: sd-device-monitor:
Passed 388 byte to netlink monitor
followed by the extra action:
Apr 21 14:15:43 ubuntu-focal systemd-udevd[1916]: bcache0: Processing device
(SEQNUM=5524, ACTION=change)
Apr 21 14:15:43 ubuntu-focal systemd-udevd[1916]: bcache0: Removing watch
Apr 21 14:15:43 ubuntu-focal systemd-udevd[1916]: value '[dmi/id]sys_vendor' is
'QEMU'
Apr 21 14:15:43 ubuntu-focal systemd-udevd[1916]: value '[dmi/id]sys_vendor' is
'QEMU'
Apr 21 14:15:43 ubuntu-focal systemd-udevd[1916]: bcache0:
/usr/lib/udev/rules.d/60-persistent-storage.rules:109 Importing properties from
results of builtin command 'blkid'
Apr 21 14:15:43 ubuntu-focal systemd-udevd[1916]: bcache0: Probe /dev/bcache0
with raid and offset=0
Apr 21 14:15:43 ubuntu-focal systemd-udevd[1916]: bcache0:
/usr/lib/udev/rules.d/60-persistent-storage.rules:112 LINK
'disk/by-uuid/30b28bee-6a1e-423d-9d53-32c78ba5454a'
Apr 21 14:15:43 ubuntu-focal systemd-udevd[1916]: bcache0: Updating old name,
'/dev/bcache/by-uuid/1522715e-a390-40db-8d47-06fb728014e5' no longer belonging
to '/devices/virtual/block/bcache0'
Apr 21 14:15:43 ubuntu-focal systemd-udevd[1916]: bcache0: No reference left,
removing '/dev/bcache/by-uuid/1522715e-a390-40db-8d47-06fb728014e5'
Apr 21 14:15:43 ubuntu-focal systemd-udevd[1916]: bcache0: Handling device node
'/dev/bcache0', devnum=b251:0
Apr 21 14:15:43 ubuntu-focal systemd-udevd[1916]: bcache0: Preserve already
existing symlink '/dev/block/251:0' to '../bcache0'
Apr 21 14:15:43 ubuntu-focal systemd-udevd[1916]: bcache0: Creating symlink
'/dev/disk/by-uuid/30b28bee-6a1e-423d-9d53-32c78ba5454a' to '../../bcache0'
Apr 21 14:15:43 ubuntu-focal systemd-udevd[1916]: bcache0: sd-device: Created
db file '/run/udev/data/b251:0' for '/devices/virtual/block/bcache0'
Apr 21 14:15:43 ubuntu-focal systemd-udevd[1916]: bcache0: Adding watch on
'/dev/bcache0'
Apr 21 14:15:43 ubuntu-focal systemd-udevd[1916]: bcache0: sd-device: Created
db file '/run/udev/data/b251:0' for '/devices/virtual/block/bcache0'
Apr 21 14:15:43 ubuntu-focal systemd-udevd[1916]: bcache0: Device (SEQNUM=5524,
ACTION=change) processed
Apr 21 14:15:43 ubuntu-focal systemd-udevd[1916]: bcache0: sd-device-monitor:
Passed 471 byte to netlink monitor
So it appears the symlink is being added to /dev/bcache/by-
uuid/1522715e-a390-40db-8d47-06fb728014e5 and then the next udev action
removes this symlink and adds dev/disk/by-uuid/30b28bee-6a1e-423d-
9d53-32c78ba5454a instead.
** Also affects: udev (Ubuntu)
Importance: Undecided
Status: New
** Changed in: udev (Ubuntu)
Assignee: (unassigned) => Dimitri John Ledkov (xnox)
** Changed in: udev (Ubuntu)
Importance: Undecided => High
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https://bugs.launchpad.net/bugs/1861941
Title:
bcache by-uuid links disappear after mounting bcache0
Status in linux package in Ubuntu:
Incomplete
Status in linux-signed-5.4 package in Ubuntu:
New
Status in udev package in Ubuntu:
New
Bug description:
1.
root@ubuntu:~# lsb_release -rd
Description: Ubuntu Focal Fossa (development branch)
Release: 20.04
2.
root@ubuntu:~# lsb_release -rd
Description: Ubuntu Focal Fossa (development branch)
Release: 20.04
root@ubuntu:~# apt-cache policy linux-image-virtual
linux-image-virtual:
Installed: 5.4.0.12.15
Candidate: 5.4.0.12.15
Version table:
*** 5.4.0.12.15 500
500 http://archive.ubuntu.com/ubuntu focal/main amd64 Packages
100 /var/lib/dpkg/status
root@ubuntu:~# apt-cache policy linux-image-5.4.0-12-generic
linux-image-5.4.0-12-generic:
Installed: 5.4.0-12.15
Candidate: 5.4.0-12.15
Version table:
*** 5.4.0-12.15 500
500 http://archive.ubuntu.com/ubuntu focal/main amd64 Packages
100 /var/lib/dpkg/status
3. mount /dev/bcache0 && ls -al /dev/bcache/by-uuid/
+ ls -al /dev/bcache/by-uuid/
total 0
drwxr-xr-x 2 root root 60 Feb 4 23:31 .
drwxr-xr-x 3 root root 60 Feb 4 23:31 ..
lrwxrwxrwx 1 root root 13 Feb 4 23:31 abdfd1f6-44ce-4266-91db-24667b9ae51a
-> ../../bcache0
4.
root@ubuntu:~# ls -al /dev/bcache/by-uuid
ls: cannot access '/dev/bcache/by-uuid': No such file or directory
ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: linux-image-5.4.0-12-generic 5.4.0-12.15
ProcVersionSignature: Ubuntu 5.4.0-12.15-generic 5.4.8
Uname: Linux 5.4.0-12-generic x86_64
ApportVersion: 2.20.11-0ubuntu16
Architecture: amd64
Date: Tue Feb 4 23:31:52 2020
ProcEnviron:
TERM=xterm-256color
PATH=(custom, no user)
LANG=C.UTF-8
SHELL=/bin/bash
SourcePackage: linux-signed-5.4
UpgradeStatus: No upgrade log present (probably fresh install)
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