Re: [pve-devel] [PATCH storage 2/2] lvm thin: don't assume that a thin pool and its volumes are active

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

Am 05.11.21 um 11:29 schrieb Fabian Ebner:
> There are cases where autoactivation can fail, as reported in the
> community forum [0]. And it could also be that a volume was
> deactivated by something outside of our control.
> 
> It doesn't seem strictly necessary to activate the thin pool itself
> (creating/removing/activating LVs within the pool still works if it's
> not active), but it does not report usage information as long as
> neither the pool nor any of its LVs are active. Activate the pool for
> that, for being able to use the flag in status(), and it should also
> serve as a good indicator that there's a problem with the pool if it
> can't be activated.

For the user reporting the issue, the autoactivation manages to activate 
the _tdata _tmeta component LVs [0] and then crashes (or at least fails 
without reverting the partial activation). But as long as the component 
LVs are activate, neither the pool LV nor any LVs in the pool can be 
activated. Meaning that this patch does not help for that scenario.

[0]: 
https://forum.proxmox.com/threads/local-lvm-not-available-after-kernel-update-on-pve-7.97406/post-428298

> 
> Before activating, check the (cached) lv_state from lvm_list_volumes.
> It's necessary to update the cache in activate_storage, because the
> flag is re-used in status(). Also update it for other (de)activations
> to be more future-proof.
> 
> [0]: https://forum.proxmox.com/threads/local-lvm-not-available-after-kernel-update-on-pve-7.97406
> 
> Signed-off-by: Fabian Ebner <f.ebner@proxmox.com>
> ---
>   PVE/Storage/LVMPlugin.pm     |  1 +
>   PVE/Storage/LvmThinPlugin.pm | 64 +++++++++++++++++++++++-------------
>   2 files changed, 42 insertions(+), 23 deletions(-)
> 
> diff --git a/PVE/Storage/LVMPlugin.pm b/PVE/Storage/LVMPlugin.pm
> index 139d391..b44aeb8 100644
> --- a/PVE/Storage/LVMPlugin.pm
> +++ b/PVE/Storage/LVMPlugin.pm
> @@ -173,6 +173,7 @@ sub lvm_list_volumes {
>   
>   	my $d = {
>   	    lv_size => int($lv_size),
> +	    lv_state => substr($lv_attr, 4, 1),
>   	    lv_type => $lv_type,
>   	};
>   	$d->{pool_lv} = $pool_lv if $pool_lv;
> diff --git a/PVE/Storage/LvmThinPlugin.pm b/PVE/Storage/LvmThinPlugin.pm
> index 34e57b2..ea7b9b3 100644
> --- a/PVE/Storage/LvmThinPlugin.pm
> +++ b/PVE/Storage/LvmThinPlugin.pm
> @@ -202,43 +202,61 @@ sub status {
>   
>       return if !$info || $info->{lv_type} ne 't' || !$info->{lv_size};
>   
> -    return ($info->{lv_size}, $info->{lv_size} - $info->{used}, $info->{used}, 1);
> +    return (
> +	$info->{lv_size},
> +	$info->{lv_size} - $info->{used},
> +	$info->{used},
> +	$info->{lv_state} eq 'a' ? 1 : 0,
> +    );
> +}
> +
> +my $activate_lv = sub {
> +    my ($vg, $lv, $cache) = @_;
> +
> +    my $lvs = $cache->{lvs} ||= PVE::Storage::LVMPlugin::lvm_list_volumes();
> +
> +    die "no such logical volume $vg/$lv" if !$lvs->{$vg} || !$lvs->{$vg}->{$lv};
> +
> +    return if $lvs->{$vg}->{$lv}->{lv_state} eq 'a';
> +
> +    run_command(['lvchange', '-ay', '-K', "$vg/$lv"], errmsg => "activating LV '$vg/$lv' failed");
> +
> +    $lvs->{$vg}->{$lv}->{lv_state} = 'a'; # update cache
> +
> +    return;
> +};
> +
> +sub activate_storage {
> +    my ($class, $storeid, $scfg, $cache) = @_;
> +
> +    $class->SUPER::activate_storage($storeid, $scfg, $cache);
> +
> +    $activate_lv->($scfg->{vgname}, $scfg->{thinpool}, $cache);
>   }
>   
>   sub activate_volume {
>       my ($class, $storeid, $scfg, $volname, $snapname, $cache) = @_;
>   
>       my $vg = $scfg->{vgname};
> +    my $lv = $snapname ? "snap_${volname}_$snapname" : $volname;
>   
> -    # only snapshot volumes needs activation
> -    if ($snapname) {
> -	my $snapvol = "snap_${volname}_$snapname";
> -	my $cmd = ['/sbin/lvchange', '-ay', '-K', "$vg/$snapvol"];
> -	run_command($cmd, errmsg => "activate_volume '$vg/$snapvol' error");
> -    } elsif ($volname =~ /^base-/) {
> -	my $cmd = ['/sbin/lvchange', '-ay', '-K', "$vg/$volname"];
> -	run_command($cmd, errmsg => "activate_volume '$vg/$volname' error");
> -    } else {
> -	# other volumes are active by default
> -    }
> +    $activate_lv->($vg, $lv, $cache);
>   }
>   
>   sub deactivate_volume {
>       my ($class, $storeid, $scfg, $volname, $snapname, $cache) = @_;
>   
> +    return if !$snapname && $volname !~ /^base-/; # other volumes are kept active
> +
>       my $vg = $scfg->{vgname};
> +    my $lv = $snapname ? "snap_${volname}_$snapname" : $volname;
>   
> -    # we only deactivate snapshot volumes
> -    if ($snapname) {
> -	my $snapvol = "snap_${volname}_$snapname";
> -	my $cmd = ['/sbin/lvchange', '-an', "$vg/$snapvol"];
> -	run_command($cmd, errmsg => "deactivate_volume '$vg/$snapvol' error");
> -    } elsif ($volname =~ /^base-/) {
> -	my $cmd = ['/sbin/lvchange', '-an', "$vg/$volname"];
> -	run_command($cmd, errmsg => "deactivate_volume '$vg/$volname' error");
> -    } else {
> -	# other volumes are kept active
> -    }
> +    run_command(['lvchange', '-an', "$vg/$lv"], errmsg => "deactivate_volume '$vg/$lv' error");
> +
> +    $cache->{lvs}->{$vg}->{$lv}->{lv_state} = '-' # update cache
> +	if $cache->{lvs} && $cache->{lvs}->{$vg} && $cache->{lvs}->{$vg}->{$lv};
> +
> +    return;
>   }
>   
>   sub clone_image {
>