[pve-devel] [PATCH v2 storage 1/1] fix #3580: plugins: make preallocation mode selectable for qcow2 and raw images

[Lorenz Stechauner]

the plugins for file based storages
 * BTRFS
 * CIFS
 * Dir
 * Glusterfs
 * NFS
now allow the option 'preallocation'.

'preallocation' can have four values:
 * default
 * off
 * metadata
 * falloc
 * full
see man pages for `qemu-img` for what these mean exactly. [0]

the defualt value was chosen to be
 * qcow2: metadata (as previously)
 * raw: off (I was unable to find any documentation on this, so
    could only test this and found, that 'off' was the most
    fitting.)

when using 'metadata' as preallocation mode, for raw images 'off'
is used.

[0] https://qemu.readthedocs.io/en/latest/system/images.html#disk-image-file-formats

Signed-off-by: Lorenz Stechauner <l.stechauner at proxmox.com>
---
 PVE/Storage/BTRFSPlugin.pm     |  1 +
 PVE/Storage/CIFSPlugin.pm      |  1 +
 PVE/Storage/DirPlugin.pm       |  1 +
 PVE/Storage/GlusterfsPlugin.pm |  4 ++-
 PVE/Storage/NFSPlugin.pm       |  1 +
 PVE/Storage/Plugin.pm          | 48 +++++++++++++++++++++++++++++++++-
 6 files changed, 54 insertions(+), 2 deletions(-)

diff --git a/PVE/Storage/BTRFSPlugin.pm b/PVE/Storage/BTRFSPlugin.pm
index b30000b..97633a2 100644
--- a/PVE/Storage/BTRFSPlugin.pm
+++ b/PVE/Storage/BTRFSPlugin.pm
@@ -73,6 +73,7 @@ sub options {
 	is_mountpoint => { optional => 1 },
 	nocow => { optional => 1 },
 	mkdir => { optional => 1 },
+	preallocation => { optional => 1 },
 	# TODO: The new variant of mkdir with  `populate` vs `create`...
     };
 }
diff --git a/PVE/Storage/CIFSPlugin.pm b/PVE/Storage/CIFSPlugin.pm
index c5f3894..3a7e638 100644
--- a/PVE/Storage/CIFSPlugin.pm
+++ b/PVE/Storage/CIFSPlugin.pm
@@ -142,6 +142,7 @@ sub options {
 	smbversion => { optional => 1},
 	mkdir => { optional => 1 },
 	bwlimit => { optional => 1 },
+	preallocation => { optional => 1 },
     };
 }
 
diff --git a/PVE/Storage/DirPlugin.pm b/PVE/Storage/DirPlugin.pm
index 2267f11..3eeec98 100644
--- a/PVE/Storage/DirPlugin.pm
+++ b/PVE/Storage/DirPlugin.pm
@@ -59,6 +59,7 @@ sub options {
 	mkdir => { optional => 1 },
 	is_mountpoint => { optional => 1 },
 	bwlimit => { optional => 1 },
+	preallocation => { optional => 1 },
    };
 }
 
diff --git a/PVE/Storage/GlusterfsPlugin.pm b/PVE/Storage/GlusterfsPlugin.pm
index ea4df82..d8d2b88 100644
--- a/PVE/Storage/GlusterfsPlugin.pm
+++ b/PVE/Storage/GlusterfsPlugin.pm
@@ -137,6 +137,7 @@ sub options {
 	format => { optional => 1 },
 	mkdir => { optional => 1 },
 	bwlimit => { optional => 1 },
+	preallocation => { optional => 1 },
     };
 }
 
@@ -260,7 +261,8 @@ sub alloc_image {
 
     my $cmd = ['/usr/bin/qemu-img', 'create'];
 
-    push @$cmd, '-o', 'preallocation=metadata' if $fmt eq 'qcow2';
+    my $prealloc_opt = PVE::Storage::Plugin::preallocation_cmd_option($scfg, $fmt);
+    push @$cmd, '-o', $prealloc_opt if defined($prealloc_opt);
 
     push @$cmd, '-f', $fmt, $volumepath, "${size}K";
 
diff --git a/PVE/Storage/NFSPlugin.pm b/PVE/Storage/NFSPlugin.pm
index 39bf15a..21b288a 100644
--- a/PVE/Storage/NFSPlugin.pm
+++ b/PVE/Storage/NFSPlugin.pm
@@ -90,6 +90,7 @@ sub options {
 	format => { optional => 1 },
 	mkdir => { optional => 1 },
 	bwlimit => { optional => 1 },
+	preallocation => { optional => 1 },
     };
 }
 
diff --git a/PVE/Storage/Plugin.pm b/PVE/Storage/Plugin.pm
index 417d1fd..4308522 100644
--- a/PVE/Storage/Plugin.pm
+++ b/PVE/Storage/Plugin.pm
@@ -41,6 +41,19 @@ our @SHARED_STORAGE = (
     'pbs',
 );
 
+our $QCOW2_PREALLOCATION = {
+    off => 1,
+    metadata => 1,
+    falloc => 1,
+    full => 1,
+};
+
+our $RAW_PREALLOCATION = {
+    off => 1,
+    falloc => 1,
+    full => 1,
+};
+
 our $MAX_VOLUMES_PER_GUEST = 1024;
 
 cfs_register_file ('storage.cfg',
@@ -152,6 +165,13 @@ my $defaultData = {
 	    type => 'string', format => 'pve-storage-format',
 	    optional => 1,
 	},
+	preallocation => {
+	    description => "Preallocation mode for raw and qcow2 images. " .
+		"Using 'metadata' on raw images results in preallocation=off.",
+	    type => 'string', enum => ['off', 'metadata', 'falloc', 'full'],
+	    default => 'metadata',
+	    optional => 1,
+	},
     },
 };
 
@@ -444,6 +464,31 @@ sub parse_config {
     return $cfg;
 }
 
+sub preallocation_cmd_option {
+    my ($scfg, $fmt) = @_;
+
+    my $prealloc = $scfg->{preallocation};
+
+    if ($fmt eq 'qcow2') {
+	$prealloc = $prealloc // 'metadata';
+
+	die "preallocation mode '$prealloc' not supported by format '$fmt'\n"
+	    if !$QCOW2_PREALLOCATION->{$prealloc};
+
+	return "preallocation=$prealloc";
+    } elsif ($fmt eq 'raw') {
+	$prealloc = $prealloc // 'off';
+	$prealloc = 'off' if $prealloc eq 'metadata';
+
+	die "preallocation mode '$prealloc' not supported by format '$fmt'\n"
+	    if !$RAW_PREALLOCATION->{$prealloc};
+
+	return "preallocation=$prealloc";
+    }
+
+    return;
+}
+
 # Storage implementation
 
 # called during addition of storage (before the new storage config got written)
@@ -764,7 +809,8 @@ sub alloc_image {
     } else {
 	my $cmd = ['/usr/bin/qemu-img', 'create'];
 
-	push @$cmd, '-o', 'preallocation=metadata' if $fmt eq 'qcow2';
+	my $prealloc_opt = preallocation_cmd_option($scfg, $fmt);
+	push @$cmd, '-o', $prealloc_opt if defined($prealloc_opt);
 
 	push @$cmd, '-f', $fmt, $path, "${size}K";
 
-- 
2.30.2