[pve-devel] [PATCH v1 pve-storage 6/8] pluginbase: document image operation methods

[Max Carrara]

Add documentation for the following methods:
- list_images
- create_base
- clone_image
- alloc_image
- free_image

Signed-off-by: Max Carrara <m.carrara at proxmox.com>
Co-authored-by: Maximiliano Sandoval <m.sandoval at proxmox.com>
---
 src/PVE/Storage/PluginBase.pm | 111 ++++++++++++++++++++++++++++++++++
 1 file changed, 111 insertions(+)

diff --git a/src/PVE/Storage/PluginBase.pm b/src/PVE/Storage/PluginBase.pm
index b3ce684..37b1471 100644
--- a/src/PVE/Storage/PluginBase.pm
+++ b/src/PVE/Storage/PluginBase.pm
@@ -721,26 +721,137 @@ sub on_delete_hook {
 
 =cut
 
+=head3 $plugin->list_images($storeid, \%scfg [, $vmid, \@vollist, \%cache])
+
+B<REQUIRED:> Must be implemented in every storage plugin.
+
+Returns a listref of all disk images of a storage. If the storage does not
+support storing disk images, returns an empty listref.
+
+Optionally, if C<\@vollist> is provided, return only disks whose volume ID is
+within C<\@vollist>. Note that this usually has higher precedence than
+C<$vmid>.
+
+C<die>s in case of errors.
+
+This method may reuse L<< cached information via C<\%cache>|/"CACHING EXPENSIVE OPERATIONS" >>.
+
+The returned listref has the following structure:
+
+    [
+	{
+	    ctime => "1689163322", # creation time as unix timestamp
+	    format => "raw",
+	    size => 8589934592, # in bytes!
+	    vmid => 101,
+	    volid => "local-lvm:base-101-disk-0", # volume ID, storage-specific
+	},
+	# [...]
+    ]
+
+=cut
+
 sub list_images {
     my ($class, $storeid, $scfg, $vmid, $vollist, $cache) = @_;
     croak "implement me in sub-class\n";
 }
 
+=head3 $plugin->create_base($storeid, \%scfg, $volname)
+
+B<OPTIONAL:> May be implemented in a storage plugin.
+
+Creates a base volume from an existing volume, allowing the volume to be
+L<< cloned|/"$plugin->clone_image(...)" >>. This cloned volume (usually
+a disk image) may then be used as a base for the purpose of creating linked
+clones. See L<C<PVE::Storage::LvmThinPlugin>> and
+L<C<PVE::Storage::ZFSPoolPlugin>> for example implementations.
+
+On completion, returns the name of the new base volume (the new C<$volname>).
+
+This method is called in the context of C<L<< cluster_lock_storage()|/"cluster_lock_storage(...)" >>>,
+i.e. when the storage is B<locked>.
+
+=cut
+
 sub create_base {
     my ($class, $storeid, $scfg, $volname) = @_;
     croak "implement me in sub-class\n";
 }
 
+=head3 $plugin->clone_image($scfg, $storeid, $volname, $vmid [, $snap])
+
+=head3 $plugin->clone_image(...)
+
+B<REQUIRED:> Must be implemented in every storage plugin.
+
+Clones a disk image or a snapshot of an image, returning the name of the new
+image (the new C<$volname>). Note that I<cloning> here means to create a linked
+clone and not duplicating an image. See L<C<PVE::Storage::LvmThinPlugin>> and
+L<C<PVE::Storage::ZFSPoolPlugin>> for example implementations.
+
+C<die>s in case of an error of if the underlying storage doesn't support
+cloning images.
+
+This method is called in the context of C<L<< cluster_lock_storage()|/"cluster_lock_storage(...)" >>>,
+i.e. when the storage is B<locked>.
+
+=cut
+
 sub clone_image {
     my ($class, $scfg, $storeid, $volname, $vmid, $snap) = @_;
     croak "implement me in sub-class\n";
 }
 
+=head3 $plugin->alloc_image($storeid, $scfg, $vmid, $fmt, $name, $size)
+
+B<REQUIRED:> Must be implemented in every storage plugin.
+
+Allocates a disk image with the given format C<$fmt> and C<$size> in bytes,
+returning the name of the new image (the new C<$volname>). See
+C<L<< plugindata()|/"$plugin->plugindata()" >>> for all disk formats.
+
+Optionally, if given, set the name of the image to C<$name>. If C<$name> isn't
+provided, the next name should be determined via C<L<< find_free_diskname()|/"$plugin->find_free_diskname(...)" >>>.
+
+C<die>s in case of an error of if the underlying storage doesn't support
+allocating images.
+
+This method is called in the context of C<L<< cluster_lock_storage()|/"cluster_lock_storage(...)" >>>,
+i.e. when the storage is B<locked>.
+
+=cut
+
 sub alloc_image {
     my ($class, $storeid, $scfg, $vmid, $fmt, $name, $size) = @_;
     croak "implement me in sub-class\n";
 }
 
+=head3 $plugin->free_image($storeid, $scfg, $volname [, $isBase, $format])
+
+=head3 $plugin->free_image(...)
+
+B<REQUIRED:> Must be implemented in every storage plugin.
+
+Frees (deletes) the disk image given by C<$volname>. Optionally, the image may
+be a base image (C<$isBase>) and have a certain C<$format>. See
+C<L<< plugindata()|/"$plugin->plugindata()" >>> for all disk formats.
+
+If a cleanup is required after freeing the image, returns a reference to a
+subroutine that performs the cleanup, and C<undef> otherwise.
+
+C<die>s in case of errors, if the image has a L<< C<protected> attribute|/"$plugin->get_volume_attribute(...)" >>
+(and may thus not be freed), or if the underlying storage implementation
+doesn't support freeing images.
+
+This method is called in the context of C<L<< cluster_lock_storage()|/"cluster_lock_storage(...)" >>>,
+i.e. when the storage is B<locked>.
+
+B<NOTE:> The returned cleanup subroutine is called in a separate worker and
+should L<< lock|/"$plugin->cluster_lock_storage(...)" >> the underlying storage
+separately.
+
+=cut
+
 sub free_image {
     my ($class, $storeid, $scfg, $volname, $isBase, $format) = @_;
     croak "implement me in sub-class\n";
-- 
2.39.5