[pve-devel] applied: [PATCH container v2] Move volume activation to vm_start

[Fabian Grünbichler]

On July 14, 2020 7:50 pm, Stoiko Ivanov wrote:
> 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 the volume activation happens before the unshare.
> 
> The other site where a container is started via systemctl is in
> 'pve-container-stop-wrapper' when a container is rebooted from the inside:
> By activating the volumes in 'lxc-pve-poststop-hook' we avoid to try starting
> a container with an inactive volume (LVM, kRBD), occuring when having a
> mp-addtion pending during such a reboot
> 
> 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 $loopdevlist variable is not used anywhere in our codebase since 2015
> (da6298481ea4dfe7d894f42fa105cda015ebe5ce).
> 
> Signed-off-by: Stoiko Ivanov <s.ivanov at proxmox.com>
> ---
> v1 -> v2:
> * added the volume activation to lxc-pve-poststop-hook, after the great review
>   from Fabian caught the case of container reboots (huge thanks!)
> * decided to put it in lxc-pve-poststop-hook instead of
>   pve-container-stop-wrapper, since this avoids pulling in quite a few parts
>   of our code-base into the latter, which currently has no imports.
>   AFAICU the only case where this could lead to a problem is if someone uses
>   `touch /var/lib/lxc/$vmid/reboot && systemctl restart pve-container@$vmid`
>   for rebooting containers
> 
> 
>  src/PVE/LXC.pm            | 5 +++++
>  src/lxc-pve-poststop-hook | 6 ++++++
>  src/lxc-pve-prestart-hook | 5 -----
>  3 files changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/src/PVE/LXC.pm b/src/PVE/LXC.pm
> index f3aca7a..db5b8ca 100644
> --- a/src/PVE/LXC.pm
> +++ b/src/PVE/LXC.pm
> @@ -2186,6 +2186,11 @@ sub vm_start {
>  	close($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-poststop-hook b/src/lxc-pve-poststop-hook
> index 2683ae2..0fdd49e 100755
> --- a/src/lxc-pve-poststop-hook
> +++ b/src/lxc-pve-poststop-hook
> @@ -75,6 +75,12 @@ PVE::LXC::Tools::lxc_hook('post-stop', 'lxc', sub {
>  	open(my $fh, '>', "/var/lib/lxc/$vmid/reboot")
>  	    or die "failed to create reboot trigger file: $!\n";
>  	close($fh);
> +
> +	# activate all volumes of the container in case pending changes added
> +	# a not yet activated volume
> +	my $vollist = PVE::LXC::Config->get_vm_volumes($conf);
> +	PVE::Storage::activate_volumes($storage_cfg, $vollist);
> +
>  	# cause lxc to stop instead of rebooting
>  	exit(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
> 
> 
> 
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