It looks like there is some ordering issues:
This is a grep through /run/udev/links ; these are checked by udev-dev
# find . -name 'b250*'
./\x2fdisk\x2fby-uuid\x2f0a270acb-56b8-4498-8bad-b3bb149fe869/b250:1
./\x2fdisk\x2fby-uuid\x2f92b0868d-7e56-4956-8e55-2c90ebee4a72/b250:0
./\x2fbcache\x2fby-uuid\x2f92d882d8-38cd-4537-847b-6f9c40ba67b4/b250:1
./\x2fbcache\x2fby-uuid\x2f57e009b1-6bf4-42ea-abe0-334b10941a0b/b250:0
So both /dev/bcache/by-uuid and /dev/disk/by-uuid both point to the bcache
device (b250:0)
udevd shows this:
Nov 30 23:39:10.738290 ubuntu systemd-udevd[465]: LINK
'disk/by-uuid/0a270acb-56b8-4498-8bad-b3bb149fe869'
/lib/udev/rules.d/60-persistent-storage.rules:79
Nov 30 23:39:10.738304 ubuntu systemd-udevd[465]: update old name,
'/dev/bcache/by-uuid/92d882d8-38cd-4537-847b-6f9c40ba67b4' no longer
belonging to '/devices/virtual/block/bcache1'
Nov 30 23:39:10.738321 ubuntu systemd-udevd[465]: no reference left, remove
'/dev/bcache/by-uuid/92d882d8-38cd-4537-847b-6f9c40ba67b4'
Nov 30 23:39:10.738361 ubuntu systemd-udevd[465]: found 'b250:1' claiming
'/run/udev/links/\x2fdisk\x2fby-uuid\x2f0a270acb-56b8-4498-8bad-b3bb149fe869'
Nov 30 23:39:10.738370 ubuntu systemd-udevd[465]: creating link
'/dev/disk/by-uuid/0a270acb-56b8-4498-8bad-b3bb149fe869' to '/dev/bcache1'
Nov 30 23:39:10.738380 ubuntu systemd-udevd[465]: preserve already existing
symlink '/dev/disk/by-uuid/0a270acb-56b8-4498-8bad-b3bb149fe869' to
'../../bcache1'
Nov 30 23:39:10.743215 ubuntu systemd-udevd[487]: LINK
'disk/by-uuid/92b0868d-7e56-4956-8e55-2c90ebee4a72'
/lib/udev/rules.d/60-persistent-storage.rules:79
Nov 30 23:39:10.743228 ubuntu systemd-udevd[487]: update old name,
'/dev/bcache/by-uuid/57e009b1-6bf4-42ea-abe0-334b10941a0b' no longer
belonging to '/devices/virtual/block/bcache0'
Nov 30 23:39:10.743247 ubuntu systemd-udevd[487]: no reference left, remove
'/dev/bcache/by-uuid/57e009b1-6bf4-42ea-abe0-334b10941a0b'
Nov 30 23:39:10.743291 ubuntu systemd-udevd[487]: found 'b250:0' claiming
'/run/udev/links/\x2fdisk\x2fby-uuid\x2f92b0868d-7e56-4956-8e55-2c90ebee4a72'
Nov 30 23:39:10.743302 ubuntu systemd-udevd[487]: creating link
'/dev/disk/by-uuid/92b0868d-7e56-4956-8e55-2c90ebee4a72' to '/dev/bcache0'
Nov 30 23:39:10.743312 ubuntu systemd-udevd[487]: preserve already existing
symlink '/dev/disk/by-uuid/92b0868d-7e56-4956-8e55-2c90ebee4a72' to
'../../bcache0'
It would seem that the 'no longer belonging to ...bcache1' is the trigger
for the removal
however, 250:1 is indeed bcache1 device.
# ls -al /dev/bcache1
brw-rw---- 1 root disk 250, 1 Nov 30 23:39 /dev/bcache1
Looking at the systemd/udev/udev-event.c it appears that for entries in
the current udev database that don't have a new event associated with them
get the call to remove the old link
void udev_event_execute_rules()
...
if (major(udev_device_get_devnum(dev)) > 0) {
bool apply;
/* remove/update possible left-over symlinks from
old database entry */
if (event->dev_db != NULL)
udev_node_update_old_links(dev,
event->dev_db);
Will need to crawl through the db to see what the the event->dev_db entry
is and where that get's set.
On Thu, Nov 30, 2017 at 2:41 PM, Dmitrii Shcherbakov <
1729...@bugs.launchpad.net> wrote:
> Looks like masking systemd-udevd removes this behavior. Need to figure
> out where it actually clears everything out.
>
> ubuntu@maas-xenial4:~$ sudo systemctl mask systemd-udevd
> 11:32 PM Created symlink from /etc/systemd/system/systemd-udevd.service
> to /dev/null.
>
> # reboot
>
> ubuntu@maas-xenial4:~$ ls /dev/bcache/by-uuid/
> 2963855b-3d2b-4387-abd1-3ae788919de4 727212eb-0f0b-4d20-9191-f0577a38454e
> 835afacf-6213-48a9-864c-43733822668b aa04ab39-a42c-446f-aff5-addbd9c80e06
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1729145
>
> Title:
> /dev/bcache/by-uuid links not created after reboot
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/
> 1729145/+subscriptions
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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:
Triaged
Status in systemd package in Ubuntu:
New
Status in linux source package in Xenial:
Triaged
Status in systemd source package in Xenial:
New
Status in linux source package in Zesty:
Triaged
Status in systemd source package in Zesty:
New
Status in linux source package in Artful:
Triaged
Status in systemd source package in Artful:
New
Status in linux source package in Bionic:
Triaged
Status in systemd source package in Bionic:
New
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
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