This is in preparation to switch qemu-server from using '-drive' to
the modern '-blockdev' in the QEMU commandline options as well as for
the qemu-storage-daemon, which only supports '-blockdev'. The plugins
know best what driver and options are needed to access an image, so
a dedicated plugin method returning the necessary parameters for
'-blockdev' is the most straight-forward.
There intentionally is only handling for absolute paths in the default
plugin implementation. Any plugin requiring more needs to implement
the method itself. With PVE 9 being a major release and most popular
plugins not using special protocols like 'rbd://', this seems
acceptable.
For NBD, etc. qemu-server should construct the blockdev object.
Signed-off-by: Fiona Ebner <f.eb...@proxmox.com>
---
Changes in v2:
* Remove $snapname, is added in later patch as an option.
* Check result for stat() call.
* Use filesystem_path(), rather than path().
src/PVE/Storage.pm | 17 +++++++++++
src/PVE/Storage/Plugin.pm | 59 +++++++++++++++++++++++++++++++++++++++
2 files changed, 76 insertions(+)
diff --git a/src/PVE/Storage.pm b/src/PVE/Storage.pm
index d0a696a..d671080 100755
--- a/src/PVE/Storage.pm
+++ b/src/PVE/Storage.pm
@@ -710,6 +710,23 @@ sub abs_filesystem_path {
return $path;
}
+# see the documentation for the plugin method
+sub qemu_blockdev_options {
+ my ($cfg, $volid) = @_;
+
+ my ($storeid, $volname) = parse_volume_id($volid);
+
+ my $scfg = storage_config($cfg, $storeid);
+
+ my $plugin = PVE::Storage::Plugin->lookup($scfg->{type});
+
+ my ($vtype) = $plugin->parse_volname($volname);
+ die "cannot use volume of type '$vtype' as a QEMU blockdevice\n"
+ if $vtype ne 'images' && $vtype ne 'iso' && $vtype ne 'import';
+
+ return $plugin->qemu_blockdev_options($scfg, $storeid, $volname);
+}
+
# used as last resort to adapt volnames when migrating
my $volname_for_storage = sub {
my ($cfg, $storeid, $name, $vmid, $format) = @_;
diff --git a/src/PVE/Storage/Plugin.pm b/src/PVE/Storage/Plugin.pm
index 4e16420..f162a13 100644
--- a/src/PVE/Storage/Plugin.pm
+++ b/src/PVE/Storage/Plugin.pm
@@ -1880,6 +1880,65 @@ sub rename_volume {
return "${storeid}:${base}${target_vmid}/${target_volname}";
}
+=pod
+
+=head3 qemu_blockdev_options
+
+ $blockdev = $plugin->qemu_blockdev_options($scfg, $storeid, $volname)
+
+Returns a hash reference with the basic options needed to open the volume via
QEMU's C<-blockdev>
+API. This at least requires a C<< $blockdev->{driver} >> and a reference to
the image, e.g.
+C<< $blockdev->{filename} >> for the C<file> driver. For files, the C<file>
driver can be used. For
+host block devices, the C<host_device> driver can be used. The plugin must not
set options like
+C<cache> or C<aio>. Those are managed by qemu-server and will be overwritten.
For other available
+drivers and the exact specification of the options, see
+L<https://qemu.readthedocs.io/en/master/interop/qemu-qmp-ref.html#object-QMP-block-core.BlockdevOptions>
+
+While Perl does not have explicit types, the result will need to be converted
to JSON later and
+match the QMP specification (see link above), so implicit types are important.
In the return value,
+use C<JSON::true> and C<JSON::false> for booleans, C<"$value"> for strings,
and C<int($value)> for
+integers.
+
+Arguments:
+
+=over
+
+=item C<$scfg>
+
+The hash reference with the storage configuration.
+
+=item C<$storeid>
+
+The storage ID.
+
+=item C<$volume>
+
+The volume name.
+
+=back
+
+=cut
+sub qemu_blockdev_options {
+ my ($class, $scfg, $storeid, $volname) = @_;
+
+ my $blockdev = {};
+
+ my ($path) = $class->filesystem_path($scfg, $volname);
+
+ if ($path =~ m|^/|) {
+ # 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.
+ my $st = File::stat::stat($path) or die "stat for '$path' failed -
$!\n";
+ my $driver = (S_ISCHR($st->mode) || S_ISBLK($st->mode)) ? 'host_device'
: 'file';
+ $blockdev = { driver => $driver, filename => $path };
+ } else {
+ die "storage plugin doesn't implement qemu_blockdev_options() method\n";
+ }
+
+ return $blockdev;
+}
+
# Used by storage plugins for external backup providers. See
PVE::BackupProvider::Plugin for the API
# the provider needs to implement.
#
--
2.39.5
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