[pve-devel] [PATCH container] Move volume activation to vm_start

[Stoiko Ivanov]

currently all volumes for a container are activated in the pre-start hook,
which runs in a separate mount namespace (lxc.monitor.unshare is set to 1
in our container config).
This leads to problems with ZFS, if a pool is imported by this call the
filesystems are mounted only inside the containers mount namespace.

by running the volume activation inside vm_start, right before starting the
container via systemctl there should be no regression when using the API/our
CLI tools.

Starting a container manually using lxc-start is usually done for obtaining
debug-logs (after starting failed with our tooling) - so the potential for
regression in that case should also be small.

The $loopdevlist variable is not used anywhere in our codebase since 2015
(da6298481ea4dfe7d894f42fa105cda015ebe5ce).

Tested by creating a zpool, two containers with 'onboot: 1' stored on it,
`echo -n '' > /etc/zfs/zpool.cache`, `update-initramfs -k all -u`, reboot

Signed-off-by: Stoiko Ivanov <s.ivanov at proxmox.com>
---
This should address multiple reports in the forum (e.g. [0,1,2]), about
containers on ZFS not starting after a reboot (mitigated by setting the correct
cache-file, thus making the pool get imported through zfs-import-cache.service
+ zfs-mount.service)

Huge Thanks to Fabian and Wolfgang for providing input on this!

[0] https://forum.proxmox.com/threads/zfs-mount-on-start-problem-segfault-at-0-error-4-in-libc-2-28-so-subvolumes-not-mounted.68519/
[1] https://forum.proxmox.com/threads/kann-keine-container-mehr-starten.69975/
[2] https://forum.proxmox.com/threads/why-i-need-to-mount-zfs-volume-manualy-for-container-after-update-initramfs-usage.71008/


 src/PVE/LXC.pm            | 5 +++++
 src/lxc-pve-prestart-hook | 5 -----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/PVE/LXC.pm b/src/PVE/LXC.pm
index f3aca7a..db5b8ca 100644
--- a/src/PVE/LXC.pm
+++ b/src/PVE/LXC.pm
@@ -2186,6 +2186,11 @@ sub vm_start {
 	close($fh);
     }
 
+    my $storage_cfg = PVE::Storage::config();
+    my $vollist = PVE::LXC::Config->get_vm_volumes($conf);
+
+    PVE::Storage::activate_volumes($storage_cfg, $vollist);
+
     my $cmd = ['systemctl', 'start', "pve-container\@$vmid"];
 
     PVE::GuestHelpers::exec_hookscript($conf, $vmid, 'pre-start', 1);
diff --git a/src/lxc-pve-prestart-hook b/src/lxc-pve-prestart-hook
index ed25aa4..8823cad 100755
--- a/src/lxc-pve-prestart-hook
+++ b/src/lxc-pve-prestart-hook
@@ -38,11 +38,6 @@ PVE::LXC::Tools::lxc_hook('pre-start', 'lxc', sub {
 
     my $storage_cfg = PVE::Storage::config();
 
-    my $vollist = PVE::LXC::Config->get_vm_volumes($conf);
-    my $loopdevlist = PVE::LXC::Config->get_vm_volumes($conf, 'rootfs');
-
-    PVE::Storage::activate_volumes($storage_cfg, $vollist);
-
     my $rootdir = $vars->{ROOTFS_PATH};
 
     # Delete any leftover reboot-trigger file
-- 
2.20.1