From ea6626f7edd9eb40a3510eaf6816a77cac4f63d0 Mon Sep 17 00:00:00 2001 From: Ian Jackson Date: Mon, 21 Oct 2019 14:23:55 +0100 Subject: [PATCH] guest_prepare_disk: Only do the umount if we set an env var MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit This call to guest_umount_lv is here for the benefit of ad-hoc reruns of (eg) ts-guest-start tidy up any ad-hoc messing about (eg from earlier runs of ts-debian-fixup or something). It is not needed in production runs. Serendipitously, this osstest code discovered a bug in the Linux blkback: when tearing down, it sets the backend state to 6 before it has closed the underlying block devices. This ultimately means that after "xl destroy" or "xl shutdown -w" there is a period when the guest's open handle onto its storage is still open. This is wrong. This detection depends on us winning a tricky race. So it shows up in osstest as a very low probability heisenbug. The bug is currently in all versions of Linux and causing a bit of a nuisance. It would be best to add a proper check for this bug. However, this is quite fiddly: really, it ought to be done as close to the xl command completion as possible, in the same ssh invocation. That would involve a fair bit of plumbing and ad-hocery. I don't think that would be proportionate for such a low-impact bug. So instead in this patch I just disable this cleanup code in the troublesome case, unless it is explicitly requested by the user setting OSSTEST_GUEST_DISK_MOUNT_CLEANUP to a trueish value. (This would be reasonably convenient for the ad-hoc testing that this call serves.) Thanks to Roger for diagnosing the Linux kernel bug. CC: Jürgen Groß Signed-off-by: Ian Jackson Reviewed-by: Roger Pau Monne --- Osstest/TestSupport.pm | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/Osstest/TestSupport.pm b/Osstest/TestSupport.pm index 78f4748..6b0ee7a 100644 --- a/Osstest/TestSupport.pm +++ b/Osstest/TestSupport.pm @@ -1938,7 +1938,8 @@ sub guest_create_paused ($) { sub guest_prepare_disk ($) { my ($gho) = @_; - guest_umount_lv($gho->{Host}, $gho); + guest_umount_lv($gho->{Host}, $gho) + if $ENV{'OSSTEST_GUEST_DISK_MOUNT_CLEANUP'}; return if ($gho->{Diskfmt} // 'none') eq "none"; -- 2.39.5