common/rc: wait for udev before creating dm targets

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@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>

diff --git a/common/rc b/common/rc
index 758584dc9998053fdc3e054e542472dfcdc99c5b..197c94157025b8e4a590e5222555237a3df7d5e7 100644 (file)
--- a/common/rc
+++ b/common/rc
@@ -4823,6 +4823,11 @@ _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
        $DMSETUP_PROG create "$@" >>$seqres.full 2>&1 || return 1
        $DMSETUP_PROG mknodes >/dev/null 2>&1
        $UDEV_SETTLE_PROG >/dev/null 2>&1