[Bug 2045586] Re: livecd-rootfs uses losetup -P for theoretically reliable/synchronous partition setup but it's not reliable

[dann frazier]

On Tue, Jan 23, 2024 at 8:55 PM Michael Hudson-Doyle
<2045586 at bugs.launchpad.net> wrote:
>
> Amazing debugging Dann. Until we can get a kernel fix, what's the way
> forward here? Run losetup without -P, run udevadm settle, run partprobe
> on the device (then maybe run udevadm settle again??)

That seems logical. I don't see the need for the 2nd udevadm settle -
but I also don't see the harm.

I've a test fix kernel building in a PPA. I think Łukasz mentioned
that there's a way to have an autopkgtest run on a specific kernel?
Can someone give me those steps?

  -dann

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https://bugs.launchpad.net/bugs/2045586

Title:
  livecd-rootfs uses losetup -P for theoretically reliable/synchronous
  partition setup but it's not reliable

Status in linux package in Ubuntu:
  New
Status in livecd-rootfs package in Ubuntu:
  New
Status in util-linux package in Ubuntu:
  New

Bug description:
  In mantic, we migrated livecd-rootfs to use losetup -P instead of
  kpartx, with the expectation that this would give us a reliable, race-
  free way of loop-mounting partitions from a disk image during image
  build.

  In noble, we are finding that it is no longer reliable, and in fact
  fails rather often.

  It is most noticeable with riscv64 builds, which is the architecture
  where we most frequently ran into problems before with kpartx.  The
  first riscv64+generic build in noble where the expected loop partition
  device is not available is

    https://launchpad.net/~ubuntu-
  cdimage/+livefs/ubuntu/noble/cpc/+build/531790

  The failure is however not unique to riscv64, and the autopkgtest for
  the latest version of livecd-rootfs (24.04.7) - an update that
  specifically tries to add more debugging code for this scenario - has
  also failed on ppc64el.

    https://autopkgtest.ubuntu.com/packages/l/livecd-
  rootfs/noble/ppc64el

  The first failure happened on November 16.  While there has been an
  update to the util-linux package in noble, this did not land until
  November 23.

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