Re: [pve-devel] [PATCH pve-storage v3 3/3] lvmthin: disable autoactivation for new logical volumes

["Michael Köppl" <m.koeppl@proxmox.com>]

On 4/29/25 13:36, Friedrich Weber wrote:
> When discovering a new volume group (VG), for example on boot, LVM
> triggers autoactivation. With the default settings, this activates all
> logical volumes (LVs) in the VG. Activating an LV creates a
> device-mapper device and a block device under /dev/mapper.
> 
> Autoactivation is problematic for shared LVM storages, see #4997 [1].
> For the inherently local LVM-thin storage it is less problematic, but
> it still makes sense to avoid unnecessarily activating LVs and thus
> making them visible on the host at boot.
> 
> Hence, disable autoactivation after creating new LVs. As lvcreate
> doesn't accept the --setautoactivation flag for thin LVs, this is done
> with an additional lvchange command. With this setting, LVM
> autoactivation will not activate these LVs, and the storage stack will
> take care of activating/deactivating LVs when needed.
> 
> [1] https://bugzilla.proxmox.com/show_bug.cgi?id=4997
> 
> Signed-off-by: Friedrich Weber <f.weber@proxmox.com>
> ---
> 
> Notes:
>     - would be great to get your opinion on whether we should consider
>       LVM-thin storages in this series or not.
>     
>     - passing --setautoactivation n to lvcreate for a thin volume says:
>     
>         Option --setautoactivation is unsupported with thins.
>     
>       But lvchange --setautoactivation seems to work on thin LVs, so the
>       fact that lvcreate doesn't accept it may be a bug. I reported it
>       upstream [1].
>     
>     new in v3
>     
>     [1] https://gitlab.com/lvmteam/lvm2/-/issues/32

Since the upstream issue has not been addressed yet and the change to
LVM-thin does, AFAICT, not mitigate problems like in #4997 (or am I
missing something here?), but is mostly done to streamline behavior,
could the changes for LVM-thin be held back until it's clear that
lvcreate not supporting --setautoactivation for LVM-thin is not on purpose?

> 
>  src/PVE/Storage/LvmThinPlugin.pm | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/src/PVE/Storage/LvmThinPlugin.pm b/src/PVE/Storage/LvmThinPlugin.pm
> index 49a4dcb..3f75ba1 100644
> --- a/src/PVE/Storage/LvmThinPlugin.pm
> +++ b/src/PVE/Storage/LvmThinPlugin.pm
> @@ -82,6 +82,19 @@ sub filesystem_path {
>      return wantarray ? ($path, $vmid, $vtype) : $path;
>  }
>  
> +# lvcreate refuses --setautoactivation for thin volumes, so set it via lvchange
> +my $set_lv_autoactivation = sub {
> +    my ($vg, $lv, $autoactivation) = @_;
> +
> +    my $cmd = [
> +	'/sbin/lvchange',
> +	'--setautoactivation', $autoactivation ? 'y' : 'n',
> +	"$vg/$lv"
> +    ];
> +    eval { run_command($cmd); };
> +    warn "could not set autoactivation: $@" if $@;
> +};
> +
>  sub alloc_image {
>      my ($class, $storeid, $scfg, $vmid, $fmt, $name, $size) = @_;
>  
> @@ -103,6 +116,7 @@ sub alloc_image {
>  	       '--thinpool', "$vg/$scfg->{thinpool}" ];
>  
>      run_command($cmd, errmsg => "lvcreate '$vg/$name' error");
> +    $set_lv_autoactivation->($vg, $name, 0);
>  
>      return $name;
>  }
> @@ -283,6 +297,7 @@ sub clone_image {
>  
>      my $cmd = ['/sbin/lvcreate', '-n', $name, '-prw', '-kn', '-s', $lv];
>      run_command($cmd, errmsg => "clone image '$lv' error");
> +    $set_lv_autoactivation->($vg, $name, 0);
>  
>      return $name;
>  }
> @@ -332,7 +347,7 @@ sub volume_snapshot {
>  
>      my $cmd = ['/sbin/lvcreate', '-n', $snapvol, '-pr', '-s', "$vg/$volname"];
>      run_command($cmd, errmsg => "lvcreate snapshot '$vg/$snapvol' error");
> -
> +    # disabling autoactivation not needed, as -s defaults to --setautoactivationskip y
>  }
>  
>  sub volume_snapshot_rollback {
> @@ -346,6 +361,7 @@ sub volume_snapshot_rollback {
>  
>      $cmd = ['/sbin/lvcreate', '-kn', '-n', $volname, '-s', "$vg/$snapvol"];
>      run_command($cmd, errmsg => "lvm rollback '$vg/$snapvol' error");
> +    $set_lv_autoactivation->($vg, $volname, 0);
>  }
>  
>  sub volume_snapshot_delete {



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