v4.13 shows the same search_free stack as 4.14, but doesn't appear to be fatal (it doesn't result in a hung process nor a block device that cannot be wiped.
I suspect we've got a new upstream issue since 4.20 didn't fix things. Re-running 4.20 to see if we had a stack trace, we don't NULL pointer oops, but there is a stuck worker queue: [ 242.887966] kworker/0:47 D 0 2165 2 0x80000000 [ 242.888014] Workqueue: events cache_set_flush [bcache] [ 242.888027] Call Trace: [ 242.888084] __schedule+0x2a2/0x880 [ 242.888097] ? __switch_to+0xfc/0x4f0 [ 242.888105] schedule+0x2c/0x80 [ 242.888113] schedule_timeout+0x246/0x350 [ 242.888122] wait_for_completion+0xb7/0x140 [ 242.888141] ? wake_up_q+0x80/0x80 [ 242.888151] kthread_stop+0x49/0x110 [ 242.888176] cache_set_flush+0xdb/0x190 [bcache] [ 242.888186] process_one_work+0x20f/0x410 [ 242.888194] worker_thread+0x34/0x400 [ 242.888202] kthread+0x120/0x140 [ 242.888209] ? process_one_work+0x410/0x410 [ 242.888216] ? kthread_park+0x90/0x90 [ 242.888236] ret_from_fork+0x35/0x40 [ 242.888435] INFO: task bcache_allocato:9015 blocked for more than 120 seconds. [ 242.893786] Not tainted 4.20.0-042000rc3-generic #201811182231 [ 242.896669] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 242.900428] bcache_allocato D 0 9015 2 0x80000000 [ 242.900434] Call Trace: [ 242.900448] __schedule+0x2a2/0x880 [ 242.900455] ? __schedule+0x2aa/0x880 [ 242.900462] schedule+0x2c/0x80 [ 242.900480] bch_bucket_alloc+0x19d/0x380 [bcache] [ 242.900503] ? wait_woken+0x80/0x80 [ 242.900519] bch_prio_write+0x190/0x340 [bcache] [ 242.900530] bch_allocator_thread+0x482/0xd10 [bcache] [ 242.900535] kthread+0x120/0x140 [ 242.900546] ? bch_invalidate_one_bucket+0x80/0x80 [bcache] [ 242.900549] ? kthread_park+0x90/0x90 [ 242.900554] ret_from_fork+0x35/0x40 -- 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/1784665 Title: mkfs.ext4 over /dev/bcache0 hangs Status in linux package in Ubuntu: In Progress Status in linux source package in Bionic: In Progress Status in linux source package in Cosmic: In Progress Bug description: $ cat /proc/version_signature Ubuntu 4.15.0-29.31-generic 4.15.18 $ lsb_release -rd Description: Ubuntu Cosmic Cuttlefish (development branch) Release: 18.10 $ apt-cache policy linux-image-`uname -r` linux-image-4.15.0-29-generic: Installed: 4.15.0-29.31 Candidate: 4.15.0-29.31 Version table: *** 4.15.0-29.31 500 500 http://archive.ubuntu.com/ubuntu cosmic/main amd64 Packages 100 /var/lib/dpkg/status 3) mkfs.ext4 /dev/bcache0 returns successful creating an ext4 filesystem on top of a bcache device 4) mkfs.ext4 doesn't return and kernel prints hung process info [ 58.018099] cloud-init[920]: Running command ['mkfs.ext4', '-F', '-L', 'root-fs', '-U', 'f01aec97-9457-11e8-b8d6-525400123401', '/dev/bcache0'] with allowed return codes [0] (capture=True) [ 242.652018] INFO: task kworker/u4:0:5 blocked for more than 120 seconds. [ 242.653767] Tainted: P O 4.15.0-29-generic #31-Ubuntu [ 242.655391] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 242.657397] INFO: task kworker/0:2:410 blocked for more than 120 seconds. [ 242.659126] Tainted: P O 4.15.0-29-generic #31-Ubuntu [ 242.660980] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 242.663000] INFO: task bcache_allocato:2326 blocked for more than 120 seconds. [ 242.664807] Tainted: P O 4.15.0-29-generic #31-Ubuntu [ 242.666516] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 242.668503] INFO: task bcache_writebac:2345 blocked for more than 120 seconds. [ 242.670301] Tainted: P O 4.15.0-29-generic #31-Ubuntu [ 242.671936] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 242.673909] INFO: task mkfs.ext4:2803 blocked for more than 120 seconds. [ 242.675414] Tainted: P O 4.15.0-29-generic #31-Ubuntu [ 242.677038] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 363.483998] INFO: task kworker/u4:0:5 blocked for more than 120 seconds. [ 363.488441] Tainted: P O 4.15.0-29-generic #31-Ubuntu [ 363.489598] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 363.491043] INFO: task kworker/0:2:410 blocked for more than 120 seconds. [ 363.492252] Tainted: P O 4.15.0-29-generic #31-Ubuntu [ 363.494085] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 363.495659] INFO: task bcache_allocato:2326 blocked for more than 120 seconds. [ 363.496957] Tainted: P O 4.15.0-29-generic #31-Ubuntu [ 363.498454] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 363.499866] INFO: task bcache_writebac:2345 blocked for more than 120 seconds. [ 363.501156] Tainted: P O 4.15.0-29-generic #31-Ubuntu [ 363.502597] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 363.504048] INFO: task mkfs.ext4:2803 blocked for more than 120 seconds. [ 363.505505] Tainted: P O 4.15.0-29-generic #31-Ubuntu [ 363.506677] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. System has two virtio block devices. bcache was created like so: make-bcache -C /dev/vdb make-bcache -B /dev/vda2 resulting in /dev/bcache0 ProblemType: Bug DistroRelease: Ubuntu 18.10 Package: linux-image-4.15.0-29-generic 4.15.0-29.31 ProcVersionSignature: User Name 4.15.0-29.31-generic 4.15.18 Uname: Linux 4.15.0-29-generic x86_64 AlsaDevices: total 0 crw-rw---- 1 root audio 116, 1 Jul 31 15:52 seq crw-rw---- 1 root audio 116, 33 Jul 31 15:52 timer AplayDevices: Error: [Errno 2] No such file or directory: 'aplay': 'aplay' ApportVersion: 2.20.10-0ubuntu7 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: Tue Jul 31 15:53:56 2018 IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig': 'iwconfig' Lsusb: Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub MachineType: QEMU Standard PC (i440FX + PIIX, 1996) 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-4.15.0-29-generic root=LABEL=cloudimg-rootfs ro console=tty1 console=ttyS0 RelatedPackageVersions: linux-restricted-modules-4.15.0-29-generic N/A linux-backports-modules-4.15.0-29-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: 1.11.1-1 dmi.chassis.type: 1 dmi.chassis.vendor: QEMU dmi.chassis.version: pc-i440fx-bionic dmi.modalias: dmi:bvnSeaBIOS:bvr1.11.1-1:bd04/01/2014:svnQEMU:pnStandardPC(i440FX+PIIX,1996):pvrpc-i440fx-bionic:cvnQEMU:ct1:cvrpc-i440fx-bionic: dmi.product.name: Standard PC (i440FX + PIIX, 1996) dmi.product.version: pc-i440fx-bionic dmi.sys.vendor: QEMU To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1784665/+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