[pve-devel] [PATCH storage 15/26] common: add is_volume_type and is_type_change_allowed helpers

[Wolfgang Bumiller]

Generally we want to allow transitioning from 'images' or 'rootdir' to
'vm-vol' or 'ct-vol' respectively, but not the other way round.
Obviously, staying *within* any of the types is also allowed.

The `is_volume_type` helper is just a convenience helper for
functionality such as, for directory based storages, deciding whether
a volume needs a VMID subdirectory.

Signed-off-by: Wolfgang Bumiller <w.bumiller at proxmox.com>
---
 src/PVE/Storage/Common.pm | 42 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/src/PVE/Storage/Common.pm b/src/PVE/Storage/Common.pm
index bab1260..7086e1c 100644
--- a/src/PVE/Storage/Common.pm
+++ b/src/PVE/Storage/Common.pm
@@ -313,4 +313,46 @@ sub should_list_images : prototype($$) ($expected_content_type, $volume_type) {
     return $expected_content_type eq $volume_type;
 }
 
+=head3 is_volume_type
+
+    is_volume_type($vtype)
+
+Returns true if C<$vtype> is C<images>, C<rootdir>, C<vm-vol> or C<ct-vol>.
+
+Convenience helper to distinguish volume vtypes and content types from other types.
+
+=cut
+
+my %VOLUME_TYPE = map { $_ => 1 } qw(images vm-vol rootdir ct-vol);
+
+sub is_volume_type : prototype($) ($vtype) {
+    return $VOLUME_TYPE{$vtype};
+}
+
+=head3 is_type_change_allowed
+
+    is_type_change_allowed($source_vtype, $target_vtype)
+
+Returns true if a volume may change from C<$source_vtype> to C<$target_vtype>.
+
+This is generally allowed if the target vtype is equal or "more strict" than the source vtype. That
+is, if the source vtype is not known, is C<"images">, or equal to C<$target_vtype>.
+
+Note that without a target vtype, only generic source vtypes (C<undef> or C<"images">) are allowed.
+
+=cut
+
+sub is_type_change_allowed : prototype($$) ($from, $to) {
+    # If the source is unknown we don't care:
+    return 1 if !defined($from);
+
+    # Likewise, if the source is "images" we don't actually know what it represents.
+    return 1 if $from eq 'images';
+
+    # Otherwise if *both* are defined they must be equal.
+    return 1 if defined($from) && defined($to) && $from eq $to; #
+
+    return undef;
+}
+
 1;
-- 
2.47.2