On Tue, Jul 26, 2022 at 12:48:36PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@xxxxxxxxxx>
>
> Every now and then I see a failure when running generic/322 on btrfs:
>
> QA output created by 322
> failed to create flakey device
>
> Looking in the 322.full file, I see:
>
> device-mapper: reload ioctl on flakey-test (253:0) failed: Device or resource busy
> Command failed.
>
> And looking in dmesg, I see:
>
> device-mapper: table: 8:3: linear: Device lookup failed (-16)
> device-mapper: ioctl: error adding target to table
>
> /dev/block/8:3 corresponds to the SCRATCH_DEV on this system. Given the
> failures in 322.out, I think this is caused by generic/322 calling
> _init_flakey -> _dmsetup_create -> $DMSETUP_PROG create being unable to
> open SCRATCH_DEV exclusively. Add a call to $UDEV_SETTLE_PROG prior to
> the creation of the target to try to calm the system down sufficiently
> that the test can proceed.
>
> Note that I don't have any hard evidence that it's udev at fault here --
> the few times I've caught this thing, udev *has* been active spraying
> error messages for nonexistent sysfs paths to journald and adding a
> 'udevadm settle' seems to fix it... but that's still only
> circumstantial. Regardless, it seems to have fixed the test failure.
>
> Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
> ---
> common/rc | 5 +++++
> 1 file changed, 5 insertions(+)
>
>
> diff --git a/common/rc b/common/rc
> index f4469464..60a9bacd 100644
> --- a/common/rc
> +++ b/common/rc
> @@ -4815,6 +4815,11 @@ _dmsetup_remove()
>
> _dmsetup_create()
> {
> + # Wait for udev to settle so that the dm creation doesn't fail because
> + # some udev subprogram opened one of the block devices mentioned in the
> + # table string w/ O_EXCL. Do it again at the end so that an immediate
> + # device open won't also fail.
> + $UDEV_SETTLE_PROG >/dev/null 2>&1
No objection from me, as you've proved it works for your issue:)
Reviewed-by: Zorro Lang <zlang@xxxxxxxxxx>
> $DMSETUP_PROG create "$@" >>$seqres.full 2>&1 || return 1
> $DMSETUP_PROG mknodes >/dev/null 2>&1
> $UDEV_SETTLE_PROG >/dev/null 2>&1
>
