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[Bug 1579106] Re: Using bcache for / leads to hung processes


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
v4.6 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:

Once testing of the upstream kernel is complete, please mark this bug as

Thanks in advance.

[0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.6-rc6-wily/

** Tags added: kernel-da-key

** Changed in: linux (Ubuntu)
   Importance: Undecided => Medium

** Changed in: linux (Ubuntu)
       Status: Confirmed => Incomplete

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  Using bcache for / leads to hung processes

Status in linux package in Ubuntu:

Bug description:
  I've used maas 1.9.1 to setup a bcache partition mount as /. The
  bcache is made of a 400GB SSD backed by sda-part2. The sda drive is a
  1TB disk with 1GB carved out for /boot (sda-part1) and the rest given
  to sda-part2. I believe the bcache mode is set to write-through.

  Within an hour of this machine being deployed (it's being used as a
  node in a landscape autopilot openstack deployment) it starts showing
  hung processes. The output of 'ps faxw' (attached as 'amco-process-
  list.txt) shows lots of process in the 'D' state and launching more
  processes that write to the disk will likely get stuck (for example
  the 'apt-get install python-jenkins' process).

  This is reproducible.

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: linux-image-3.13.0-85-generic 3.13.0-85.129
  ProcVersionSignature: User Name 3.13.0-85.129-generic 3.13.11-ckt36
  Uname: Linux 3.13.0-85-generic x86_64
   total 0
   crw-rw---- 1 root audio 116,  1 May  6 03:07 seq
   crw-rw---- 1 root audio 116, 33 May  6 03:07 timer
  AplayDevices: Error: [Errno 2] No such file or directory: 'aplay'
  ApportVersion: 2.14.1-0ubuntu3.19
  Architecture: amd64
  ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord'
  AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
  Date: Fri May  6 14:24:20 2016
  IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig'
  MachineType: HP ProLiant DL360e Gen8
   PATH=(custom, no user)
  ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.13.0-85-generic root=UUID=cd48c2ff-f38e-4892-a5e2-8862e4412c29 ro console=ttyS0
   linux-restricted-modules-3.13.0-85-generic N/A
   linux-backports-modules-3.13.0-85-generic  N/A
   linux-firmware                             1.127.22
  RfKill: Error: [Errno 2] No such file or directory: 'rfkill'
  SourcePackage: linux
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 08/02/2014
  dmi.bios.vendor: HP
  dmi.bios.version: P73
  dmi.chassis.type: 23
  dmi.chassis.vendor: HP
  dmi.modalias: dmi:bvnHP:bvrP73:bd08/02/2014:svnHP:pnProLiantDL360eGen8:pvr:cvnHP:ct23:cvr:
  dmi.product.name: ProLiant DL360e Gen8
  dmi.sys.vendor: HP

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