[Bug 1893667] Re: Btrfs commands don't work when using user-space emulation of other architectures

[Thomas Huth]

Released with QEMU v5.2.0.

** Changed in: qemu
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1893667

Title:
  Btrfs commands don't work when using user-space emulation of other
  architectures

Status in QEMU:
  Fix Released
Status in qemu package in Fedora:
  Unknown

Bug description:
  Description of problem:
  When doing cross-arch builds with mock, it uses qemu-user-static under the 
hood, and qemu-user-static lacks support for Btrfs ioctls to emulate so that 
btrfs(8) commands work correctly.

  This is especially important for being able to do cross-arch image
  builds.

  How reproducible:
  Always (on Fedora 33 with qemu-5.1.0-2.fc33)

  Steps to Reproduce:

  $ sudo dnf install mock qemu-user-static wget
  $ sudo usermod -a -G mock $USER
  $ newgrp mock
  $ mock --root fedora-rawhide-armhfp --install btrfs-progs util-linux
  $ mock --root fedora-rawhide-armhfp --chroot 'rm -f foo.img && dd 
if=/dev/zero of=foo.img bs=1G count=1 && losetup /dev/loop9 foo.img &&  
mkfs.btrfs /dev/loop9 && mkdir /foo && mount /dev/loop9 /foo && btrfs subvol 
create /foo/subvol && umount /foo && losetup -d /dev/loop9'

  
  Actual results:
  Fails with errors like "ERROR: cannot create subvolume: Function not 
implemented"

  Expected results:
  Succeeds and creates subvolumes properly.

  Additional info:
  There is a patch series from a few days ago to add support for many btrfs 
ioctls which could fix this...

  https://lists.gnu.org/archive/html/qemu-devel/2020-08/msg05594.html

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