Following up my question; we should see both events in all kernels. The first event is when the /dev/bcache0 is joined with a cache device, and emitts the CACHED_UUID value in the uevent; the UUID is the *backing device bcache metadata UUID* it is not related to the content contained within the backing device; this CACHED_UUID is symlinked at /dev/bcache /by-uuid
Once /dev/bcache0 is created, blkid will scan the contents of /dev/bcache0 which contains an ext4 filesystem and the FS_UUID is symlinked at /dev/disk/by-uuid. CACHED_UUID != FS_UUID /dev/bcache/by-uuid != /dev/disk/by-uuid I speculate that udev has a bug where it's only looking at the basename of the symlink target and removing any other 'by-uuid' link against the device when it needs to account for the full path of the symlink since the bcache/by-uuid is different than the disk/by-uuid. -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. 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) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1861941/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
