[Bug 1654057] Re: btrfs balance crashed

[MichaelE]

Btrfs ran into this issue a couple of times on this partition, always
falling back to read-only.

A btrfs check produced the following log entries:

Jan  5 18:44:01 mothership kernel: [1451559.293128] BTRFS warning (device dm-19): checksum error at logical 105529344 on dev /dev/mapper/VGinternal02-root--backup, sector 206112: metadata leaf (level 0) in tree 7
Jan  5 18:44:01 mothership kernel: [1451559.293134] BTRFS warning (device dm-19): checksum error at logical 105529344 on dev /dev/mapper/VGinternal02-root--backup, sector 206112: metadata leaf (level 0) in tree 7
Jan  5 18:44:01 mothership kernel: [1451559.293140] BTRFS error (device dm-19): bdev /dev/mapper/VGinternal02-root--backup errs: wr 0, rd 0, flush 0, corrupt 1, gen 0
Jan  5 18:44:01 mothership kernel: [1451559.293144] BTRFS error (device dm-19): unable to fixup (regular) error at logical 105529344 on dev /dev/mapper/VGinternal02-root--backup
Jan  5 18:44:02 mothership kernel: [1451559.601334] BTRFS warning (device dm-19): checksum error at logical 105545728 on dev /dev/mapper/VGinternal02-root--backup, sector 206144: metadata leaf (level 0) in tree 7
Jan  5 18:44:02 mothership kernel: [1451559.601336] BTRFS warning (device dm-19): checksum error at logical 105545728 on dev /dev/mapper/VGinternal02-root--backup, sector 206144: metadata leaf (level 0) in tree 7
Jan  5 18:44:02 mothership kernel: [1451559.601338] BTRFS error (device dm-19): bdev /dev/mapper/VGinternal02-root--backup errs: wr 0, rd 0, flush 0, corrupt 2, gen 0
Jan  5 18:44:02 mothership kernel: [1451559.601352] BTRFS error (device dm-19): unable to fixup (regular) error at logical 105545728 on dev /dev/mapper/VGinternal02-root--backup

As the content on the disk did not change since I converted from ext4 to
btrfs, I think that the inconsistency must have been produced by btrfs.
To be sure, I am now also checking the underlying partition for errors -
it is a raid 1 with 3 active disks and lvm on top of it. So far neither
dm nor lvm reported errors.

Then I will backup to tape and buld a new btrfs partition from scratch.

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https://bugs.launchpad.net/bugs/1654057

Title:
  btrfs balance crashed

Status in btrfs-tools package in Ubuntu:
  New

Bug description:
  Converted a lvm partition from ext4 to btrfs, then deleted ext subvolume and started btrfs balance. Balance job crashed after some time leaving the partion in ro status.
  btrfs check on unmounted partition did not work.
  Could remount with -o recovery which also started balance job again.

  Can somebody tell me what caused the crash and whether any data got
  lost?

  I'll attach the part of the kern.log as well.

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: btrfs-tools 4.4-1
  ProcVersionSignature: Ubuntu 4.4.0-53.74-generic 4.4.30
  Uname: Linux 4.4.0-53-generic x86_64
  ApportVersion: 2.20.1-0ubuntu2.4
  Architecture: amd64
  Date: Wed Jan  4 20:40:30 2017
  ProcEnviron:
   LANGUAGE=de_DE
   TERM=xterm-256color
   PATH=(custom, no user)
   LANG=de_DE.UTF-8
   SHELL=/bin/bash
  SourcePackage: btrfs-tools
  UpgradeStatus: Upgraded to xenial on 2014-07-29 (890 days ago)

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