On June 26, 2025 4:40 pm, Fiona Ebner wrote:
> This is mostly in preparation for external qcow2 snapshot support.
>
> For internal qcow2 snapshots, which currently are the only supported
> variant, it is not possible to attach the snapshot only. If access to
> that is required it will need to be handled differently, e.g. via a
> FUSE/NBD export.
just for the avoidance of doubt since it's only implied and not spelled
out explicitly - we don't do any such accesses at the moment, right?
linked clones cannot be done for running VMs, full clones of snapshots
don't happen within the running VM but via qemu-img convert, and nothing
else besides replication (which is ZFS specific) and manual `pvesm
export` calls (which are on the storage level by definition) directly
reads from a storage snapshot?
>
> Signed-off-by: Fiona Ebner <f.eb...@proxmox.com>
> ---
>
> No changes in v3. RFC, because it depends on the previous one.
>
> src/PVE/Storage/ISCSIDirectPlugin.pm | 3 +++
> src/PVE/Storage/Plugin.pm | 13 ++++++++++++-
> src/PVE/Storage/RBDPlugin.pm | 2 ++
> src/PVE/Storage/ZFSPlugin.pm | 3 +++
> src/PVE/Storage/ZFSPoolPlugin.pm | 2 ++
> 5 files changed, 22 insertions(+), 1 deletion(-)
>
> diff --git a/src/PVE/Storage/ISCSIDirectPlugin.pm
> b/src/PVE/Storage/ISCSIDirectPlugin.pm
> index 12b894d..e0f8a62 100644
> --- a/src/PVE/Storage/ISCSIDirectPlugin.pm
> +++ b/src/PVE/Storage/ISCSIDirectPlugin.pm
> @@ -113,6 +113,9 @@ sub path {
> sub qemu_blockdev_options {
> my ($class, $scfg, $storeid, $volname, $options) = @_;
>
> + die "volume snapshot is not possible on iscsi device\n"
> + if $options->{'snapshot-name'};
> +
> my $lun = ($class->parse_volname($volname))[1];
>
> return {
> diff --git a/src/PVE/Storage/Plugin.pm b/src/PVE/Storage/Plugin.pm
> index 7a274a3..e6892ec 100644
> --- a/src/PVE/Storage/Plugin.pm
> +++ b/src/PVE/Storage/Plugin.pm
> @@ -2004,6 +2004,11 @@ A hash reference with additional options.
>
> =over
>
> +=item C<< $options->{'snapshot-name'} >>
> +
> +(optional) The snapshot name. Set when the associated snapshot should be
> opened rather than the
> +volume itself.
> +
> =item C<< $options->{hints} >>
>
> A hash reference with hints indicating what the volume will be used for.
> This can be safely ignored
> @@ -2030,9 +2035,15 @@ sub qemu_blockdev_options {
>
> my $blockdev = {};
>
> - my ($path) = $class->filesystem_path($scfg, $volname);
> + my ($path) = $class->filesystem_path($scfg, $volname,
> $options->{'snapshot-name'});
>
> if ($path =~ m|^/|) {
> + # For qcow2 and qed the path of a snapshot will be the same, but
> it's not possible to attach
> + # the snapshot alone.
> + my $format = ($class->parse_volname($volname))[6];
> + die "cannot attach only the snapshot of a '$format' image\n"
> + if $options->{'snapshot-name'} && ($format eq 'qcow2' || $format
> eq 'qed');
> +
> # The 'file' driver only works for regular files. The check below is
> taken from
> # block/file-posix.c:hdev_probe_device() in QEMU. Do not bother with
> detecting 'host_cdrom'
> # devices here, those are not managed by the storage layer.
> diff --git a/src/PVE/Storage/RBDPlugin.pm b/src/PVE/Storage/RBDPlugin.pm
> index 6b37ba3..cf3d354 100644
> --- a/src/PVE/Storage/RBDPlugin.pm
> +++ b/src/PVE/Storage/RBDPlugin.pm
> @@ -530,6 +530,7 @@ sub qemu_blockdev_options {
> my ($name) = ($class->parse_volname($volname))[1];
>
> if ($scfg->{krbd}) {
> + $name .= '@' . $options->{'snapshot-name'} if
> $options->{'snapshot-name'};
> my $rbd_dev_path = get_rbd_dev_path($scfg, $storeid, $name);
> return { driver => 'host_device', filename => $rbd_dev_path };
> }
> @@ -540,6 +541,7 @@ sub qemu_blockdev_options {
> image => "$name",
> };
> $blockdev->{namespace} = "$scfg->{namespace}" if
> defined($scfg->{namespace});
> + $blockdev->{snapshot} = $options->{'snapshot-name'} if
> $options->{'snapshot-name'};
>
> $blockdev->{conf} = $cmd_option->{ceph_conf} if $cmd_option->{ceph_conf};
>
> diff --git a/src/PVE/Storage/ZFSPlugin.pm b/src/PVE/Storage/ZFSPlugin.pm
> index 0f64898..940d4f0 100644
> --- a/src/PVE/Storage/ZFSPlugin.pm
> +++ b/src/PVE/Storage/ZFSPlugin.pm
> @@ -250,6 +250,9 @@ sub path {
> sub qemu_blockdev_options {
> my ($class, $scfg, $storeid, $volname, $options) = @_;
>
> + die "direct access to snapshots not implemented\n"
> + if $options->{'snapshot-name'};
> +
> my $name = ($class->parse_volname($volname))[1];
> my $guid = $class->zfs_get_lu_name($scfg, $name);
> my $lun = $class->zfs_get_lun_number($scfg, $guid);
> diff --git a/src/PVE/Storage/ZFSPoolPlugin.pm
> b/src/PVE/Storage/ZFSPoolPlugin.pm
> index 677f88c..86f83a2 100644
> --- a/src/PVE/Storage/ZFSPoolPlugin.pm
> +++ b/src/PVE/Storage/ZFSPoolPlugin.pm
> @@ -165,6 +165,8 @@ sub path {
> sub qemu_blockdev_options {
> my ($class, $scfg, $storeid, $volname, $options) = @_;
>
> + die "cannot attach only the snapshot of a zvol\n" if
> $options->{'snapshot-name'};
> +
> my ($path) = $class->path($scfg, $volname, $storeid);
>
> my $blockdev = { driver => 'host_device', filename => $path };
> --
> 2.47.2
>
>
>
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>
>
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