[pve-devel] [PATCH v3 pve-storage 1/3] qcow2: add external snapshot support

[Alexandre Derumier via pve-devel <pve-devel@lists.proxmox.com>]

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From: Alexandre Derumier <alexandre.derumier@groupe-cyllene.com>
To: pve-devel@lists.proxmox.com
Subject: [PATCH v3 pve-storage 1/3] qcow2: add external snapshot support
Date: Mon, 16 Dec 2024 10:12:17 +0100
Message-ID: <20241216091229.3142660-4-alexandre.derumier@groupe-cyllene.com>

Signed-off-by: Alexandre Derumier <alexandre.derumier@groupe-cyllene.com>
---
 src/PVE/Storage/DirPlugin.pm |   1 +
 src/PVE/Storage/Plugin.pm    | 207 +++++++++++++++++++++++++++++------
 2 files changed, 176 insertions(+), 32 deletions(-)

diff --git a/src/PVE/Storage/DirPlugin.pm b/src/PVE/Storage/DirPlugin.pm
index fb23e0a..1cd7ac3 100644
--- a/src/PVE/Storage/DirPlugin.pm
+++ b/src/PVE/Storage/DirPlugin.pm
@@ -81,6 +81,7 @@ sub options {
 	is_mountpoint => { optional => 1 },
 	bwlimit => { optional => 1 },
 	preallocation => { optional => 1 },
+	snapext => { optional => 1 },
    };
 }
 
diff --git a/src/PVE/Storage/Plugin.pm b/src/PVE/Storage/Plugin.pm
index fececa1..aeba8d3 100644
--- a/src/PVE/Storage/Plugin.pm
+++ b/src/PVE/Storage/Plugin.pm
@@ -214,6 +214,11 @@ my $defaultData = {
 	    maximum => 65535,
 	    optional => 1,
 	},
+        'snapext' => {
+	    type => 'boolean',
+	    description => 'enable external snapshot.',
+	    optional => 1,
+        },
     },
 };
 
@@ -710,11 +715,15 @@ sub filesystem_path {
     # Note: qcow2/qed has internal snapshot, so path is always
     # the same (with or without snapshot => same file).
     die "can't snapshot this image format\n"
-	if defined($snapname) && $format !~ m/^(qcow2|qed)$/;
+	if defined($snapname) && !$scfg->{snapext} && $format !~ m/^(qcow2|qed)$/;
 
     my $dir = $class->get_subdir($scfg, $vtype);
 
-    $dir .= "/$vmid" if $vtype eq 'images';
+    if ($scfg->{snapext} && $snapname) {
+	$name = $class->get_snap_volname($volname, $snapname);
+    } else {
+	$dir .= "/$vmid" if $vtype eq 'images';
+    }
 
     my $path = "$dir/$name";
 
@@ -953,6 +962,31 @@ sub free_image {
 # TODO taken from PVE/QemuServer/Drive.pm, avoiding duplication would be nice
 my @checked_qemu_img_formats = qw(raw cow qcow qcow2 qed vmdk cloop);
 
+sub qemu_img_info {
+    my ($filename, $file_format, $timeout, $follow_backing_files) = @_;
+
+    my $cmd = ['/usr/bin/qemu-img', 'info', '--output=json', $filename];
+    push $cmd->@*, '-f', $file_format if $file_format;
+    push $cmd->@*, '--backing-chain' if $follow_backing_files;
+
+    my $json = '';
+    my $err_output = '';
+    eval {
+        run_command($cmd,
+            timeout => $timeout,
+            outfunc => sub { $json .= shift },
+            errfunc => sub { $err_output .= shift . "\n"},
+        );
+    };
+    warn $@ if $@;
+    if ($err_output) {
+        # if qemu did not output anything to stdout we die with stderr as an error
+        die $err_output if !$json;
+        # otherwise we warn about it and try to parse the json
+        warn $err_output;
+    }
+    return $json;
+}
 # set $untrusted if the file in question might be malicious since it isn't
 # created by our stack
 # this makes certain checks fatal, and adds extra checks for known problems like
@@ -1016,25 +1050,9 @@ sub file_size_info {
 	warn "file_size_info: '$filename': falling back to 'raw' from unknown format '$file_format'\n";
 	$file_format = 'raw';
     }
-    my $cmd = ['/usr/bin/qemu-img', 'info', '--output=json', $filename];
-    push $cmd->@*, '-f', $file_format if $file_format;
 
-    my $json = '';
-    my $err_output = '';
-    eval {
-	run_command($cmd,
-	    timeout => $timeout,
-	    outfunc => sub { $json .= shift },
-	    errfunc => sub { $err_output .= shift . "\n"},
-	);
-    };
-    warn $@ if $@;
-    if ($err_output) {
-	# if qemu did not output anything to stdout we die with stderr as an error
-	die $err_output if !$json;
-	# otherwise we warn about it and try to parse the json
-	warn $err_output;
-    }
+    my $json = qemu_img_info($filename, $file_format, $timeout);
+
     if (!$json) {
 	die "failed to query file information with qemu-img\n" if $untrusted;
 	# skip decoding if there was no output, e.g. if there was a timeout.
@@ -1162,11 +1180,28 @@ sub volume_snapshot {
 
     die "can't snapshot this image format\n" if $volname !~ m/\.(qcow2|qed)$/;
 
-    my $path = $class->filesystem_path($scfg, $volname);
+    if($scfg->{snapext}) {
 
-    my $cmd = ['/usr/bin/qemu-img', 'snapshot','-c', $snap, $path];
+	my $path = $class->path($scfg, $volname, $storeid);
+	my $snappath = $class->path($scfg, $volname, $storeid, $snap);
+	my $format = ($class->parse_volname($volname))[6];
+	#rename current volume to snap volume
+	rename($path, $snappath) if -e $path && !-e $snappath;
+
+	my $cmd = ['/usr/bin/qemu-img', 'create', '-b', $snappath,
+		   '-F', $format, '-f', 'qcow2', $path];
+
+	my $options = "extended_l2=on,cluster_size=128k,";
+	$options .= preallocation_cmd_option($scfg, 'qcow2');
+	push @$cmd, '-o', $options;
+	run_command($cmd);
 
-    run_command($cmd);
+    } else {
+
+	my $path = $class->filesystem_path($scfg, $volname);
+	my $cmd = ['/usr/bin/qemu-img', 'snapshot','-c', $snap, $path];
+	run_command($cmd);
+    }
 
     return undef;
 }
@@ -1177,6 +1212,21 @@ sub volume_snapshot {
 sub volume_rollback_is_possible {
     my ($class, $scfg, $storeid, $volname, $snap, $blockers) = @_;
 
+    if ($scfg->{snapext}) {
+	#technically, we could manage multibranch, we it need lot more work for snapshot delete
+	#we need to implemente block-stream from deleted snapshot to all others child branchs
+	#when online, we need to do a transaction for multiple disk when delete the last snapshot
+	#and need to merge in current running file
+
+	my $snappath = $class->path($scfg, $volname, $storeid, $snap);
+	my $snapshots = $class->volume_snapshot_info($scfg, $storeid, $volname);
+	my $parentsnap = $snapshots->{current}->{parent};
+
+	return 1 if !-e $snappath || $snapshots->{$parentsnap}->{file} eq $snappath;
+
+	die "can't rollback, '$snap' is not most recent snapshot on '$volname'\n";
+    }
+
     return 1;
 }
 
@@ -1187,9 +1237,15 @@ sub volume_snapshot_rollback {
 
     my $path = $class->filesystem_path($scfg, $volname);
 
-    my $cmd = ['/usr/bin/qemu-img', 'snapshot','-a', $snap, $path];
-
-    run_command($cmd);
+    if ($scfg->{snapext}) {
+	#simply delete the current snapshot and recreate it
+	my $path = $class->filesystem_path($scfg, $volname);
+	unlink($path);
+	$class->volume_snapshot($scfg, $storeid, $volname, $snap);
+    } else {
+	my $cmd = ['/usr/bin/qemu-img', 'snapshot','-a', $snap, $path];
+	run_command($cmd);
+    }
 
     return undef;
 }
@@ -1201,13 +1257,52 @@ sub volume_snapshot_delete {
 
     return 1 if $running;
 
+    my $cmd = "";
     my $path = $class->filesystem_path($scfg, $volname);
 
-    $class->deactivate_volume($storeid, $scfg, $volname, $snap, {});
+    if ($scfg->{snapext}) {
 
-    my $cmd = ['/usr/bin/qemu-img', 'snapshot','-d', $snap, $path];
+	my $snapshots = $class->volume_snapshot_info($scfg, $storeid, $volname);
+	my $snappath = $snapshots->{$snap}->{file};
+	return if !-e $snappath;  #already deleted ?
+
+	my $parentsnap = $snapshots->{$snap}->{parent};
+	my $childsnap = $snapshots->{$snap}->{child};
+
+	my $parentpath = $snapshots->{$parentsnap}->{file} if $parentsnap;
+	my $childpath = $snapshots->{$childsnap}->{file} if $childsnap;
+
+
+	#if first snapshot, we merge child, and rename the snapshot to child
+	if(!$parentsnap) {
+	    #we use commit here, as it's faster than rebase
+	    #https://lists.gnu.org/archive/html/qemu-discuss/2019-08/msg00041.html
+	    print"commit $childpath\n";
+	    $cmd = ['/usr/bin/qemu-img', 'commit', $childpath];
+	    run_command($cmd);
+	    print"delete $childpath\n";
+
+	    unlink($childpath);
+	    print"rename $snappath to $childpath\n";
+	    rename($snappath, $childpath);
+	} else {
+	    print"commit $snappath\n";
+	    $cmd = ['/usr/bin/qemu-img', 'commit', $snappath];
+	    #if we delete an intermediate snapshot, we need to link upper snapshot to base snapshot
+	    die "missing parentsnap snapshot to rebase child $childpath\n" if !$parentpath;
+	    print "link $childsnap to $parentsnap\n";
+	    $cmd = ['/usr/bin/qemu-img', 'rebase', '-u', '-b', $parentpath, '-F', 'qcow2', '-f', 'qcow2', $childpath];
+	    run_command($cmd);
+	    #delete the snapshot
+	    unlink($snappath);
+	}
+
+    } else {
+	$class->deactivate_volume($storeid, $scfg, $volname, $snap, {});
 
-    run_command($cmd);
+	$cmd = ['/usr/bin/qemu-img', 'snapshot','-d', $snap, $path];
+	run_command($cmd);
+    }
 
     return undef;
 }
@@ -1246,8 +1341,8 @@ sub volume_has_feature {
 	    current => { qcow2 => 1, raw => 1, vmdk => 1 },
 	},
 	rename => {
-	    current => {qcow2 => 1, raw => 1, vmdk => 1},
-	},
+	    current => { qcow2 => 1, raw => 1, vmdk => 1},
+	}
     };
 
     if ($feature eq 'clone') {
@@ -1481,7 +1576,37 @@ sub status {
 sub volume_snapshot_info {
     my ($class, $scfg, $storeid, $volname) = @_;
 
-    die "volume_snapshot_info is not implemented for $class";
+    my $path = $class->filesystem_path($scfg, $volname);
+
+    my $backing_chain = 1;
+    my $json = qemu_img_info($path, undef, 10, $backing_chain);
+    die "failed to query file information with qemu-img\n" if !$json;
+    my $snapshots = eval { decode_json($json) };
+
+    my $info = {};
+    my $order = 0;
+    for my $snap (@$snapshots) {
+
+	my $snapfile = $snap->{filename};
+	my $snapname = parse_snapname($snapfile);
+	$snapname = 'current' if !$snapname;
+	my $snapvolname = $class->get_snap_volname($volname, $snapname);
+
+	$info->{$snapname}->{order} = $order;
+	$info->{$snapname}->{file}= $snapfile;
+	$info->{$snapname}->{volname} = $snapvolname;
+	$info->{$snapname}->{volid} = "$storeid:$snapvolname";
+	$info->{$snapname}->{ext} = 1;
+
+	my $parentfile = $snap->{'backing-filename'};
+	if ($parentfile) {
+	    my $parentname = parse_snapname($parentfile);
+	    $info->{$snapname}->{parent} = $parentname;
+	    $info->{$parentname}->{child} = $snapname;
+	}
+	$order++;
+    }
+    return $info;
 }
 
 sub activate_storage {
@@ -1867,4 +1992,22 @@ sub config_aware_base_mkdir {
     }
 }
 
+sub get_snap_volname {
+    my ($class, $volname, $snapname) = @_;
+
+    my ($vtype, $name, $vmid, $basename, $basevmid, $isBase, $format) = $class->parse_volname($volname);
+    $name = !$snapname || $snapname eq 'current' ? $volname : "$vmid/snap-$snapname-$name";
+    return $name;
+}
+
+sub parse_snapname {
+    my ($name) = @_;
+
+    my $basename = basename($name);
+    if ($basename =~ m/^snap-(.*)-vm(.*)$/) {
+	return $1;
+    }
+    return undef;
+}
+
 1;
-- 
2.39.5



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