[pve-devel] [PATCH storage 1/1] add check for fsfreeze before snapshot

[Stoiko Ivanov <s.ivanov@proxmox.com>]

In order to take a snapshot of a container volume, which can be mounted
read-only with RBD, the volume needs to be frozen (fsfreeze (8)) before taking
the snapshot. Only RBD is affected by this (for LVMThin this is handled
by the devicemapper).

This commit adds helpers to determine if the FIFREEZE ioctl needs to be called
for the volume.

Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>
---
 PVE/Storage.pm           | 12 ++++++++++++
 PVE/Storage/Plugin.pm    |  4 ++++
 PVE/Storage/RBDPlugin.pm |  5 +++++
 3 files changed, 21 insertions(+)

diff --git a/PVE/Storage.pm b/PVE/Storage.pm
index cd7b5ff..27223b6 100755
--- a/PVE/Storage.pm
+++ b/PVE/Storage.pm
@@ -287,6 +287,18 @@ sub volume_snapshot_delete {
     }
 }
 
+# check if a filesystem on top of a volume needs to flush it's journal for
+# constency (see fsfreeze(8)) before a snapshot is taken - needed for
+# container mountpoints
+sub volume_snapshot_needs_fsfreeze {
+    my ($cfg, $volid) = @_;
+
+    my ($storeid, $volname) = parse_volume_id($volid);
+    my $scfg = storage_config($cfg, $storeid);
+    my $plugin = PVE::Storage::Plugin->lookup($scfg->{type});
+    return $plugin->volume_snapshot_needs_fsfreeze();
+}
+
 # check if a volume or snapshot supports a given feature
 # $feature - one of:
 #            clone - linked clone is possible
diff --git a/PVE/Storage/Plugin.pm b/PVE/Storage/Plugin.pm
index 63f68da..a046640 100644
--- a/PVE/Storage/Plugin.pm
+++ b/PVE/Storage/Plugin.pm
@@ -888,6 +888,10 @@ sub volume_snapshot_delete {
     return undef;
 }
 
+sub volume_snapshot_needs_fsfreeze {
+
+    return 0;
+}
 sub storage_can_replicate {
     my ($class, $scfg, $storeid, $format) = @_;
 
diff --git a/PVE/Storage/RBDPlugin.pm b/PVE/Storage/RBDPlugin.pm
index 38f2b46..94df89d 100644
--- a/PVE/Storage/RBDPlugin.pm
+++ b/PVE/Storage/RBDPlugin.pm
@@ -694,6 +694,11 @@ sub volume_snapshot_delete {
     return undef;
 }
 
+sub volume_snapshot_needs_fsfreeze {
+
+    return 1;
+}
+
 sub volume_has_feature {
     my ($class, $scfg, $feature, $storeid, $volname, $snapname, $running) = @_;
 
-- 
2.20.1