[pve-devel] [PATCH storage v2 1/2] fix #3873: btrfs: check for correct subvolume taking snapshot

[Maximiliano Sandoval <m.sandoval@proxmox.com>]

Suppose we are taking a snapshot of VM 100's disk-0. The
dir_glob_foreach runs over $path=/subvolume/images/100, lists all
snapshot names and appends their names to the path of the disk, e.g.
/subvolume/images/vm-100-disk-0@SNAP_NAME, but the original directory
$path might contain a second disk `vm-100-disk-1` which is also listed
by the dir_glib_foreach.

This change adds a helper foreach_snapshot_of_subvol which only lists
snapshots for the current volume.

The helper is also implemented in the other place where we iterate over
snapshots.

Signed-off-by: Maximiliano Sandoval <m.sandoval@proxmox.com>
---

Differences from v1:
 - Add a helper to run callback on each snapshot.

 src/PVE/Storage/BTRFSPlugin.pm | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/src/PVE/Storage/BTRFSPlugin.pm b/src/PVE/Storage/BTRFSPlugin.pm
index cadd9d1..d21c831 100644
--- a/src/PVE/Storage/BTRFSPlugin.pm
+++ b/src/PVE/Storage/BTRFSPlugin.pm
@@ -419,6 +419,20 @@ my sub foreach_subvol : prototype($$) {
     })
 }
 
+# Calls `$code->($volume, $snap_name)` for each snapshot of the subvolume.
+my sub foreach_snapshot_of_subvol : prototype($$) {
+    my ($subvol, $code) = @_;
+
+    my $basename = basename($subvol);
+    my $dir = dirname($subvol);
+    foreach_subvol($dir, sub {
+	my ($volume, $name, $snap) = @_;
+	return if $name ne $basename;
+	return if !defined $snap;
+	$code->($volume, $snap);
+   });
+}
+
 sub free_image {
     my ($class, $storeid, $scfg, $volname, $isBase, $_format) = @_;
 
@@ -439,10 +453,8 @@ sub free_image {
     my $dir = dirname($subvol);
     my $basename = basename($subvol);
     my @snapshot_vols;
-    foreach_subvol($dir, sub {
-	my ($volume, $name, $snapshot) = @_;
-	return if $name ne $basename;
-	return if !defined $snapshot;
+    foreach_snapshot_of_subvol($dir, sub {
+	my ($volume, $snap_name) = @_;
 	push @snapshot_vols, "$dir/$volume";
     });
 
@@ -782,8 +794,9 @@ sub volume_export {
     if (ref($with_snapshots) eq 'ARRAY') {
 	push @$cmd, (map { "$path\@$_" } ($with_snapshots // [])->@*), $path;
     } else {
-	dir_glob_foreach(dirname($path), $BTRFS_VOL_REGEX, sub {
-	    push @$cmd, "$path\@$_[2]" if !(defined($snapshot) && $_[2] eq $snapshot);
+	foreach_snapshot_of_subvol($path, sub {
+	    my ($volume, $snap_name) = @_;
+	    push @$cmd, "$path\@$snap_name" if !(defined($snapshot) && $snap_name eq $snapshot);
 	});
     }
     $path .= "\@$snapshot" if defined($snapshot);
-- 
2.39.5



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