[pve-devel] [PATCH v2 storage] ZFS: mount subvols in activate_volume

[Fabian Ebner <f.ebner@proxmox.com>]

Makes it possible to clone and start a container whose
ZFS subvols are not yet mounted for some reason. If a
subvol cannot be mounted, there's a better error now:
zfs error: cannot mount '/myzpool/subvol-103-disk-0': directory is not empty

Previously, cloning would quietly do an "empty" clone,
and startup would fail with:
mount_autodev: 1074 Permission denied - Failed to create "/dev" directory
lxc_setup: 3238 Failed to mount "/dev"
do_start: 1224 Failed to setup container "103"
__sync_wait: 41 An error occurred in another process (expected sequence number 5)

Signed-off-by: Fabian Ebner <f.ebner@proxmox.com>
---

Changes from v1:
    * not a change in this patch, but important:
      commit e8bb92bd2b1af95fd20db1b4aeb3dabc2811f571 moved volume activation
      to vm_start, meaning that the mount operation introduced by this patch
      does not happen (and fail) in the restricted apparmor context anymore
    * adapt commit message to reflect current behavior (when the first version
      was sent, starting failed quietly without producing an error)
    * rebase against current master

Previous discussion:
https://lists.proxmox.com/pipermail/pve-devel/2020-April/043088.html

 PVE/Storage/ZFSPoolPlugin.pm | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/PVE/Storage/ZFSPoolPlugin.pm b/PVE/Storage/ZFSPoolPlugin.pm
index 7c180ea..215b703 100644
--- a/PVE/Storage/ZFSPoolPlugin.pm
+++ b/PVE/Storage/ZFSPoolPlugin.pm
@@ -549,9 +549,14 @@ sub activate_volume {
 
     my (undef, undef, undef, undef, undef, undef, $format) = $class->parse_volname($volname);
 
-    return 1 if $format ne 'raw';
-
-    $class->zfs_wait_for_zvol_link($scfg, $volname);
+    if ($format eq 'raw') {
+	$class->zfs_wait_for_zvol_link($scfg, $volname);
+    } elsif ($format eq 'subvol') {
+	my $mounted = $class->zfs_get_properties($scfg, 'mounted', "$scfg->{pool}/$volname");
+	if ($mounted !~ m/^yes$/) {
+	    $class->zfs_request($scfg, undef, 'mount', "$scfg->{pool}/$volname");
+	}
+    }
 
     return 1;
 }
-- 
2.20.1