I'm seeing messages like this in dmesg:
[ 2400.951071] INFO: task btrfs-cleaner:325 blocked for more than 120 seconds.
[ 2400.958293] Not tainted 4.4.0-24-generic #43-Ubuntu
[ 2400.963918] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 2400.972037] btrfs-cleaner D ffff880071f77ce8 0 325 2 0x00000000
[ 2400.972049] ffff880071f77ce8 ffff8800045ac020 ffff88007a110c80 ffff88007d4b1900
[ 2400.972062] ffff880071f78000 ffff88007e31b9f0 ffff88007e31b800 ffff88007e31b9f0
[ 2400.972073] 0000000000000001 ffff880071f77d00 ffffffff81821b15 ffff880079a97950
[ 2400.972088] Call Trace:
[ 2400.972103] [<ffffffff81821b15>] schedule+0x35/0x80
[ 2400.972163] [<ffffffffc0262fb3>] wait_current_trans.isra.21+0xd3/0x120 [btrfs]
[ 2400.972174] [<ffffffff810c3b80>] ? wake_atomic_t_function+0x60/0x60
[ 2400.972225] [<ffffffffc02648db>] start_transaction+0x2cb/0x4c0 [btrfs]
[ 2400.972276] [<ffffffffc0264ae8>] btrfs_start_transaction+0x18/0x20 [btrfs]
[ 2400.972324] [<ffffffffc024d27f>] btrfs_drop_snapshot+0x54f/0x830 [btrfs]
[ 2400.972334] [<ffffffff81821466>] ? __schedule+0x3b6/0xa30
[ 2400.972385] [<ffffffffc0263ae2>] btrfs_clean_one_deleted_snapshot+0xb2/0x100 [btrfs]
[ 2400.972435] [<ffffffffc025c3af>] cleaner_kthread+0xcf/0x220 [btrfs]
[ 2400.972484] [<ffffffffc025c2e0>] ? check_leaf+0x360/0x360 [btrfs]
[ 2400.972493] [<ffffffff810a06a8>] kthread+0xd8/0xf0
[ 2400.972501] [<ffffffff810a05d0>] ? kthread_create_on_node+0x1e0/0x1e0
[ 2400.972509] [<ffffffff81825f8f>] ret_from_fork+0x3f/0x70
[ 2400.972517] [<ffffffff810a05d0>] ? kthread_create_on_node+0x1e0/0x1e0
Also, Sometimes btrfs quota rescan will stop making progress on this system and never recover until a reboot.
ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: linux-image-generic 4.4.0.24.25
ProcVersionSignature: Ubuntu 4.4.0-24.43-generic 4.4.10
Uname: Linux 4.4.0-24-generic x86_64
AlsaVersion: Advanced Linux Sound Architecture Driver Version k4.4.0-24-generic.
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay'
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord'
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/by-path', '/dev/snd/hwC0D1', '/dev/snd/pcmC0D3p', '/dev/snd/controlC0', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
Card0.Amixer.info: Error: [Errno 2] No such file or directory: 'amixer'
Card0.Amixer.values: Error: [Errno 2] No such file or directory: 'amixer'
Date: Tue Jun 14 08:40:00 2016
EcryptfsInUse: Yes
IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig'
MachineType: NETGEAR ReadyNAS 314
ProcEnviron:
TERM=screen
PATH=(custom, no user)
LANG=en_US.UTF-8
SHELL=/bin/bash
ProcFB: 0 psbdrmfb
ProcKernelCmdLine: ro rootflags=subvol=ubuntu console=tty0 console=ttyS0,115200n8 root=/dev/md127
RelatedPackageVersions:
linux-restricted-modules-4.4.0-24-generic N/A
linux-backports-modules-4.4.0-24-generic N/A
linux-firmware 1.157
RfKill: Error: [Errno 2] No such file or directory: 'rfkill'
SourcePackage: linux
UpgradeStatus: Upgraded to xenial on 2016-06-02 (12 days ago)
dmi.bios.date: 11/05/2013
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 4.6.5
dmi.board.asset.tag: To be filled by O.E.M.
dmi.board.name: To be filled by O.E.M.
dmi.board.vendor: To be filled by O.E.M.
dmi.board.version: To be filled by O.E.M.
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: NETGEAR
dmi.chassis.version: To Be Filled By O.E.M.
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr4.6.5:bd11/05/2013:svnNETGEAR:pnReadyNAS314:pvr11/05/2013ReadyNAS-314V1.0:rvnTobefilledbyO.E.M.:rnTobefilledbyO.E.M.:rvrTobefilledbyO.E.M.:cvnNETGEAR:ct3:cvrToBeFilledByO.E.M.:
dmi.product.name: ReadyNAS 314
dmi.product.version: 11/05/2013 ReadyNAS-314 V1.0
dmi.sys.vendor: NETGEAR
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