[pve-devel] [PATCH storage 3/6] plugin: volume export formats: avoid superfluous file_size_info() call

[Fiona Ebner]

The result from the file_size_info() call is not used by
volume_export_formats() and most failure scenarios of file_size_info()
lead to an undefined return value rather than a failure. This includes
the case for a non-existent file. The default path() implementation
doesn't do any existence check either.

An interesting scenario where file_size_info() does fail, is when the
volume is corrupted or not in the queried format. But this is a rare
edge case, so an early check doesn't seem worth it. It will be caught
by volume_export() itself, or in case of VM migration, also when
querying the size during scanning of local volumes.

While checking for the definedness of $size could serve as an early
sanity check, it is not currently done and other plugins don't do such
early checks in their implementation of volume_export_formats()
either. Keep the implementation abstract in Plugin.pm too and avoid
doing IO. Callers that want to do early existence checks or similar
can do so themselves explicitly, covering all plugins.

Signed-off-by: Fiona Ebner <f.ebner at proxmox.com>
---
 src/PVE/Storage/Plugin.pm | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/src/PVE/Storage/Plugin.pm b/src/PVE/Storage/Plugin.pm
index ce1530e..ca70c03 100644
--- a/src/PVE/Storage/Plugin.pm
+++ b/src/PVE/Storage/Plugin.pm
@@ -1733,10 +1733,7 @@ sub volume_export {
 sub volume_export_formats {
     my ($class, $scfg, $storeid, $volname, $snapshot, $base_snapshot, $with_snapshots) = @_;
     if ($scfg->{path} && !defined($snapshot) && !defined($base_snapshot)) {
-	my ($file) = $class->path($scfg, $volname, $storeid)
-	    or return;
 	my $format = ($class->parse_volname($volname))[6];
-	my $size = file_size_info($file, undef, $format);
 
 	if ($with_snapshots) {
 	    return ($format.'+size') if ($format eq 'qcow2' || $format eq 'vmdk');
-- 
2.39.5