This is the warning trigger line:
int bch_cached_dev_writeback_start(struct cached_dev *dc)
...
WARN_ON(test_and_set_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags));
...
This commit fixes this problem:
commit 1f0ffa67349c56ea54c03ccfd1e073c990e7411e
Author: Coly Li <[email protected]>
Date: Mon Jun 10 06:13:35 2019 +0800
bcache: only set BCACHE_DEV_WB_RUNNING when cached device
attached
It is included in linux 5.2, so for now only Ubuntu Eoan has the fix;
I could reproduce the problem with Ubuntu Disco (5.0-based) kernel.
The problem can Oops the kernel (worse error) if the cache is not
attached soon (reproduced below).
I'll provide a test kernel with the fix soon.
Steps to reproduce:
------------------
With attach (last line in script):
$ sudo ./setup-bcache-wb_percent-before-attach.sh
...
[ 36.130659] WARNING: CPU: 2 PID: 1288 at
drivers/md/bcache/writeback.c:837 bch_cached_dev_writeback_start+0x156/0x164
[bcache]
...
[ 36.155742] RIP: 0010:bch_cached_dev_writeback_start+0x156/0x164 [bcache]
...
[ 36.182455] Call Trace:
[ 36.183387] bch_cached_dev_attach+0x356/0x480 [bcache]
[ 36.185104] ? bch_keybuf_init+0x70/0x70 [bcache]
[ 36.186653] __cached_dev_store+0x59f/0x8b0 [bcache]
[ 36.188274] bch_cached_dev_store+0x39/0xc0 [bcache]
[ 36.189887] sysfs_kf_write+0x3b/0x40
[ 36.191142] kernfs_fop_write+0x12e/0x1b0
[ 36.192502] __vfs_write+0x1b/0x40
[ 36.193686] vfs_write+0xab/0x1b0
[ 36.194842] ksys_write+0x5c/0xd0
[ 36.196026] __x64_sys_write+0x1a/0x20
[ 36.197296] do_syscall_64+0x5a/0x110
[ 36.198532] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 36.200158] RIP: 0033:0x7f69a1d09154
...
[ 36.222967] ---[ end trace ec65e906cd03afa6 ]---
[ 36.225017] bcache: bch_cached_dev_attach() Caching loop0 as bcache0 on
set 57322d7a-1421-4dfc-a8cb-9c7b4e60c50a
Without attach (last line in script):
in a few seconds:
$ sudo ./setup-bcache-wb_percent-before-attach.sh
...
[ 30.623677] BUG: unable to handle kernel NULL pointer dereference at
0000000000000340
[ 30.627527] #PF error: [normal kernel read fault]
[ 30.629825] PGD 0 P4D 0
[ 30.631194] Oops: 0000 [#1] SMP PTI
...
[ 30.638818] Workqueue: events update_writeback_rate [bcache]
[ 30.640543] RIP: 0010:update_writeback_rate+0x36/0x330 [bcache]
...
[ 30.668496] Call Trace:
[ 30.670003] ? __schedule+0x2d8/0x840
[ 30.671998] process_one_work+0x20f/0x410
[ 30.674163] worker_thread+0x34/0x400
[ 30.676160] kthread+0x120/0x140
[ 30.678014] ? process_one_work+0x410/0x410
[ 30.680238] ? __kthread_parkme+0x70/0x70
[ 30.682411] ret_from_fork+0x35/0x40
...
[ 30.704646] ---[ end trace 1bbc1b34c704f1c5 ]---
[ 30.707086] RIP: 0010:update_writeback_rate+0x36/0x330 [bcache]
Test script:
$ cat setup-bcache-wb_percent-before-attach.sh
#!/bin/sh
#set -ex
dmesg -C
echo 9 > /proc/sys/kernel/printk
FILE_BACKING=/backing.img
FILE_CACHING=/caching.img
dd if=/dev/zero of=$FILE_BACKING bs=1G seek=1 count=0
dd if=/dev/zero of=$FILE_CACHING bs=1G seek=1 count=0
dd if=/dev/zero of=$FILE_BACKING bs=1M count=1 conv=notrunc
dd if=/dev/zero of=$FILE_CACHING bs=1M count=1 conv=notrunc
LOOP_BACKING=$(losetup -f --show $FILE_BACKING)
LOOP_CACHING=$(losetup -f --show $FILE_CACHING)
make-bcache -B $LOOP_BACKING
make-bcache -C $LOOP_CACHING
sleep 3
CSET_UUID=$(bcache-super-show $LOOP_CACHING | awk '/cset\.uuid/ { print
$2 }')
# Change writeback_percent before attaching
echo 11 > /sys/block/$(basename $LOOP_BACKING)/bcache/writeback_percent
sleep 1
# Comment this line to Oops in a few seconds
echo $CSET_UUID > /sys/block/$(basename $LOOP_BACKING)/bcache/attach
--
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/1837788
Title:
bcache kernel warning when attaching device
Status in linux package in Ubuntu:
Confirmed
Bug description:
See attached dmesg, each time this server is rebooted it emits a
concerning bcache warning.
ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: linux-image-4.15.0-54-generic 4.15.0-54.58
ProcVersionSignature: Ubuntu 4.15.0-54.58-generic 4.15.18
Uname: Linux 4.15.0-54-generic x86_64
AlsaVersion: Advanced Linux Sound Architecture Driver Version
k4.15.0-54-generic.
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay': 'aplay'
ApportVersion: 2.20.9-0ubuntu7.7
Architecture: amd64
ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord':
'arecord'
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/by-path',
'/dev/snd/hwC0D2', '/dev/snd/pcmC0D2c', '/dev/snd/pcmC0D3c',
'/dev/snd/pcmC0D3p', '/dev/snd/pcmC0D0c', '/dev/snd/pcmC0D0p',
'/dev/snd/controlC0', '/dev/snd/hwC1D0', '/dev/snd/pcmC1D3p',
'/dev/snd/controlC1', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
Card0.Amixer.info: Error: [Errno 2] No such file or directory: 'amixer':
'amixer'
Card0.Amixer.values: Error: [Errno 2] No such file or directory: 'amixer':
'amixer'
Card1.Amixer.info: Error: [Errno 2] No such file or directory: 'amixer':
'amixer'
Card1.Amixer.values: Error: [Errno 2] No such file or directory: 'amixer':
'amixer'
Date: Wed Jul 24 12:28:06 2019
InstallationDate: Installed on 2013-10-04 (2119 days ago)
InstallationMedia: Ubuntu-Server 13.10 "Saucy Salamander" - Beta amd64
(20130925.1)
MachineType: Supermicro X9DAi
ProcEnviron:
TERM=xterm-256color
PATH=(custom, no user)
XDG_RUNTIME_DIR=<set>
LANG=en_US.UTF-8
SHELL=/bin/bash
ProcFB: 0 EFI VGA
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.15.0-54-generic
root=UUID=8577302d-1f37-40a6-afcd-385beb26059f ro nomodeset elevator=deadline
nvme_core.default_ps_max_latency_us=0 nopti noibrs noibpb
RelatedPackageVersions:
linux-restricted-modules-4.15.0-54-generic N/A
linux-backports-modules-4.15.0-54-generic N/A
linux-firmware 1.173.9
RfKill: Error: [Errno 2] No such file or directory: 'rfkill': 'rfkill'
SourcePackage: linux
UpgradeStatus: Upgraded to bionic on 2018-06-09 (409 days ago)
dmi.bios.date: 05/09/2015
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 3.2
dmi.board.asset.tag: To be filled by O.E.M.
dmi.board.name: X9DAi
dmi.board.vendor: Supermicro
dmi.board.version: 0123456789
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: Supermicro
dmi.chassis.version: 0123456789
dmi.modalias:
dmi:bvnAmericanMegatrendsInc.:bvr3.2:bd05/09/2015:svnSupermicro:pnX9DAi:pvr0123456789:rvnSupermicro:rnX9DAi:rvr0123456789:cvnSupermicro:ct3:cvr0123456789:
dmi.product.family: To be filled by O.E.M.
dmi.product.name: X9DAi
dmi.product.version: 0123456789
dmi.sys.vendor: Supermicro
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