Did this issue start happening after an update/upgrade? Was there a prior kernel version where you were not having this particular problem?
Would it be possible for you to test the latest upstream kernel? Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest v4.14 kernel[0]. If this bug is fixed in the mainline kernel, please add the following tag 'kernel-fixed-upstream'. If the mainline kernel does not fix this bug, please add the tag: 'kernel-bug-exists-upstream'. Once testing of the upstream kernel is complete, please mark this bug as "Confirmed". Thanks in advance. [0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.14-rc7 ** Tags added: kernel-da-key ** Changed in: linux (Ubuntu) Importance: Undecided => Medium ** Also affects: linux (Ubuntu Artful) Importance: Undecided Status: New ** Changed in: linux (Ubuntu Artful) Status: New => Confirmed ** Changed in: linux (Ubuntu Artful) Importance: Undecided => Medium -- 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/1729145 Title: /dev/bcache/by-uuid links not created after reboot Status in linux package in Ubuntu: Confirmed Status in linux source package in Artful: Confirmed Bug description: 1. $ lsb_release -rd Description: Ubuntu 17.10 Release: 17.10 2. $ apt-cache policy linux-image-`uname -r` linux-image-4.13.0-16-generic: Installed: 4.13.0-16.19 Candidate: 4.13.0-16.19 Version table: *** 4.13.0-16.19 500 500 http://nova.clouds.archive.ubuntu.com/ubuntu artful/main amd64 Packages 100 /var/lib/dpkg/status 3. After creating some bcache devices and rebooting /dev/bcache/by-uuid/<UUID> -> ../../bcacheN symlinks point to the current bcache device which is caching the dev.uuid found after creating a backing device. 4. /dev/bcache/by-uuid does not exist and there are not symlinks underneath It appears that since the initramfs loads the bcache module which probes and finds all of the cache devices and backing devices then once the rootfs is mounted and udev gets to run, the bcache kernel module does not emit the CACHED_UUID value into the environment if the underlying devices are already registered. In dmesg, one can see that prior to mounting the rootfs, we see bcache register events: [ 5.333973] bcache: register_bdev() registered backing device vdb2 [ 5.354138] bcache: register_bdev() registered backing device vdb4 [ 5.365665] bcache: register_bdev() registered backing device vdb3 [ 5.397720] bcache: bch_journal_replay() journal replay done, 0 keys in 1 entries, seq 1 [ 5.428683] bcache: register_cache() registered cache device vdb1 then rootfs ismounted and systemd starts systemd-udev [ 9.350889] systemd[1]: Listening on udev Kernel Socket. And then the coldplug replay of kernel events triggers /lib/udev/rules.d/69-bcache.rules which invokes /lib/udev/bcache-register which writes the device name (/dev/vdb1 or /dev/bcache0) into /sys/fs/bcache/register and results is the bcache kernel driver attempting to register the block device. However, there is already a bcache device associated already and registration fails [ 11.173141] bcache: register_bcache() error opening /dev/vdb2: device already registered [ 11.184617] bcache: register_bcache() error opening /dev/vdb3: device already registered [ 11.199130] bcache: register_bcache() error opening /dev/vdb1: device already registered [ 11.271694] bcache: register_bcache() error opening /dev/vdb4: device already registered The problem then is that only a kernel call to bch_cached_dev_run() which happens like this: bcache_register() register_bdev() bch_cached_dev_run() kobject_uevent_env(&disk_to_dev(d->disk)->kobj, KOBJ_CHANGE, env); where env includes: "DRIVER=bcache", kasprintf(GFP_KERNEL, "CACHED_UUID=%pU", dc->sb.uuid), NULL, NULL, }; Since that event is not emitted for any previously registered device, then the symlink will not be created. ProblemType: Bug DistroRelease: Ubuntu 17.10 Package: linux-image-4.13.0-16-generic 4.13.0-16.19 ProcVersionSignature: User Name 4.13.0-16.19-generic 4.13.4 Uname: Linux 4.13.0-16-generic x86_64 AlsaDevices: total 0 crw-rw---- 1 root audio 116, 1 Oct 31 22:09 seq crw-rw---- 1 root audio 116, 33 Oct 31 22:09 timer AplayDevices: Error: [Errno 2] No such file or directory: 'aplay': 'aplay' ApportVersion: 2.20.7-0ubuntu3.1 Architecture: amd64 ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord': 'arecord' AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1: CRDA: N/A Date: Wed Nov 1 01:39:01 2017 Ec2AMI: ami-0000030b Ec2AMIManifest: FIXME Ec2AvailabilityZone: nova Ec2InstanceType: m1.small Ec2Kernel: unavailable Ec2Ramdisk: unavailable IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig': 'iwconfig' Lsusb: Bus 001 Device 002: ID 0627:0001 Adomax Technology Co., Ltd Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub MachineType: OpenStack Foundation OpenStack Nova PciMultimedia: ProcEnviron: TERM=xterm PATH=(custom, no user) XDG_RUNTIME_DIR=<set> LANG=C.UTF-8 SHELL=/bin/bash ProcFB: ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.13.0-16-generic root=LABEL=cloudimg-rootfs ro console=tty1 console=ttyS0 RelatedPackageVersions: linux-restricted-modules-4.13.0-16-generic N/A linux-backports-modules-4.13.0-16-generic N/A linux-firmware N/A RfKill: Error: [Errno 2] No such file or directory: 'rfkill': 'rfkill' SourcePackage: linux UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 04/01/2014 dmi.bios.vendor: SeaBIOS dmi.bios.version: 1.10.1-1ubuntu1~cloud0 dmi.chassis.type: 1 dmi.chassis.vendor: QEMU dmi.chassis.version: pc-i440fx-zesty dmi.modalias: dmi:bvnSeaBIOS:bvr1.10.1-1ubuntu1~cloud0:bd04/01/2014:svnOpenStackFoundation:pnOpenStackNova:pvr15.0.7:cvnQEMU:ct1:cvrpc-i440fx-zesty: dmi.product.family: Virtual Machine dmi.product.name: OpenStack Nova dmi.product.version: 15.0.7 dmi.sys.vendor: OpenStack Foundation To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1729145/+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
