[pve-devel] [PATCH storage 2/2] fix #4997: lvm: set "activation skip" flag for newly created LVs

[Friedrich Weber <f.weber@proxmox.com>]

Activating an LV creates a device-mapper device. In a cluster with a
shared LVM VG (e.g. on top of iSCSI) where an LV is active on nodes 1
and 2, deleting the LV on node 1 will not clean up the device-mapper
device on node 2. If an LV with the same name is recreated later, the
leftover device-mapper device will cause activation of that LV on node
2 to fail with:

> device-mapper: create ioctl on [...] failed: Device or resource busy

By default, LVM autoactivates all discovered LVs after boot, thus
creating device-mapper device for all discovered LVs. As a result,
certain combinations of guest removal (and thus LV removals) and node
reboots can cause guest creation or VM live migration (which both
entail LV activation) to fail with the above error message, see [1].

To avoid this issue in the future, adjust the LVM plugin to create new
LVs with the "activation skip" flag. LVs with that flag are not
activated unless `-K` is passed to the activation command. Consequently,
new LVs will not be autoactivated after boot anymore, and removing LVs
will not leave behind device-mapper devices on other nodes anymore.

The LVM plugin is still able to activate LVs, as it already passes
`-K` to all activation commands.

Note that the flag is only set for newly created LVs, so LVs created
before this patch can still trigger #4997. To avoid this, users can
manually set the "activation skip" flag on existing LVs.

[1] https://bugzilla.proxmox.com/show_bug.cgi?id=4997

Suggested-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
Signed-off-by: Friedrich Weber <f.weber@proxmox.com>
---

Notes:
    Should only be applied close to the next major release, see cover
    letter.

 src/PVE/Storage/LVMPlugin.pm | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/PVE/Storage/LVMPlugin.pm b/src/PVE/Storage/LVMPlugin.pm
index 66b42de..191e8d3 100644
--- a/src/PVE/Storage/LVMPlugin.pm
+++ b/src/PVE/Storage/LVMPlugin.pm
@@ -342,7 +342,7 @@ sub lvcreate {
 	$size .= "k"; # default to kilobytes
     }
 
-    my $cmd = ['/sbin/lvcreate', '-aly', '-K', '-Wy', '--yes', '--size', $size, '--name', $name];
+    my $cmd = ['/sbin/lvcreate', '-aly', '-K', '-ky', '-Wy', '--yes', '--size', $size, '--name', $name];
     for my $tag (@$tags) {
 	push @$cmd, '--addtag', $tag;
     }
-- 
2.39.2