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[Mauricio Faria de Oliveira <1867916@xxxxxxxxxxxxxxxxxx>]

Also marking Ubuntu / Groovy as Fix Released, as Groovy/devel has the
5.8 kernel already, which ships the fix.

** Changed in: linux (Ubuntu)
       Status: Fix Committed => Fix Released

** Changed in: linux (Ubuntu Groovy)
       Status: Won't Fix => Fix Released

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https://bugs.launchpad.net/bugs/1867916

Title:
  Regression in kernel 4.15.0-91 causes kernel panic with Bcache

Status in Linux:
  Confirmed
Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Xenial:
  Fix Released
Status in linux source package in Bionic:
  Fix Released
Status in linux source package in Eoan:
  Won't Fix
Status in linux source package in Focal:
  Fix Released
Status in linux source package in Groovy:
  Fix Released

Bug description:
  [Impact]

   * Users of bcache who manually specified a block size
     greater than the page size when creating the device
     with 'make-bcache' started to hit a kernel BUG/oops
     after kernel upgrades.  (This is not widely used.)

   * The issue has been exposed with commit ad6bf88a6c19
     ("block: fix an integer overflow in logical block size")
     because it increased the range of values accepted as
     logical block size, which used to overflow to zero,
     and thus receive a default of 512 via block layer.

   * The issue existed previously, but with fewer values
     exposed (e.g. 8k, 16k, 32k); the regression reports
     happened with larger values (512k) for RAID stripes.

  [Fix]

   * The upstream commit dcacbc1242c7 ("bcache: check and
     adjust logical block size for backing devices") checks
     the block size and adjusts it if needed, to the value
     of the underlying device's logical block size.

   * It is merged as of v5.8-rcN, and sent to v5.7 stable.

  [Test Case]

   * Run make-bcache with block size greater than page size.
     $ sudo make-bcache --bdev $DEV --block 8k

   * Expected results: bcache device registered; no BUG/oops.
   * Details steps on comment #43.

  [Regression Potential]

   * Restricted to users who specify a bcache block size
     greater than page size.

   * Regressions could theoretically manifest on bcache
     device probe/register, if the underlying device's
     logical block size for whatever triggers issues not
     seen previously with the overflow/default 512 bytes.

  [Other Info]

   * Unstable has the patch on both master/master-5.7.
   * Groovy should get it on rebase.

  [Original Bug Description]
  After upgrading from kernel 4.15.0-88 to 4.15.0-91 one of our systems does not boot any longer. It always crashes during boot with a kernel panic.

  I suspect that this crash might be related to Bcache because this is
  the only one of our systems where we use Bcache and the kernel panic
  appears right after Bcache initialization.

  I already checked that this bug still exists in the 4.15.0-92.93
  kernel from proposed.

  Unfortunately, I cannot do a bisect because this is a critical
  production system and we do not have any other system with a similar
  configuration.

  I attached a screenshot with the trace of the kernel panic.

  The last message that appears before the kernel panic (or rather the
  last one that I can see - there is a rather long pause between that
  message and the panic and I cannot scroll up far enough to ensure that
  there are no other messages in between) is:

  bcache: register_bcache() error /dev/dm-0: device already registered

  When booting with kernel 4.15.0-88 that does not have this problem,
  the next message is

  bcache: register_bcache() error /dev/dm-12: device already registered
  (emitting change event)

  After that the next message is:

  Begin: Loading essential drivers ... done

  This message also appears after the kernel panic, but the boot process
  stalls and the system can only be recovered by doing a hardware reset.

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: linux-image-4.15.0-88-generic 4.15.0-88.88
  ProcVersionSignature: Ubuntu 4.15.0-88.88-generic 4.15.18
  Uname: Linux 4.15.0-88-generic x86_64
  AlsaDevices:
   total 0
   crw-rw---- 1 root audio 116,  1 Mar 17 21:08 seq
   crw-rw---- 1 root audio 116, 33 Mar 17 21:08 timer
  AplayDevices: Error: [Errno 2] No such file or directory: 'aplay': 'aplay'
  ApportVersion: 2.20.9-0ubuntu7.11
  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:
  Date: Wed Mar 18 12:55:18 2020
  HibernationDevice: RESUME=UUID=40512ea2-9fce-40f5-8362-5daf955cc26a
  InstallationDate: Installed on 2013-07-02 (2450 days ago)
  InstallationMedia: Ubuntu-Server 12.04.2 LTS "Precise Pangolin" - Release amd64 (20130214)
  MachineType: HP ProLiant DL160 G6
  PciMultimedia:

  ProcFB: 0 mgadrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.15.0-88-generic root=/dev/mapper/vg0-root ro nosmt nomdmonddf nomdmonisw nomdmonddf nomdmonisw nomdmonddf nomdmonisw nomdmonddf nomdmonisw nomdmonddf nomdmonisw
  RelatedPackageVersions:
   linux-restricted-modules-4.15.0-88-generic N/A
   linux-backports-modules-4.15.0-88-generic  N/A
   linux-firmware                             1.173.16
  RfKill: Error: [Errno 2] No such file or directory: 'rfkill': 'rfkill'
  SourcePackage: linux
  UpgradeStatus: Upgraded to bionic on 2018-09-23 (541 days ago)
  dmi.bios.date: 11/06/2009
  dmi.bios.vendor: HP
  dmi.bios.version: O33
  dmi.chassis.asset.tag: 0191525
  dmi.chassis.type: 23
  dmi.chassis.vendor: HP
  dmi.modalias: dmi:bvnHP:bvrO33:bd11/06/2009:svnHP:pnProLiantDL160G6:pvr:cvnHP:ct23:cvr:
  dmi.product.name: ProLiant DL160 G6
  dmi.sys.vendor: HP

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