[PATCH pve-storage 2/5] qcow2: add external snapshot support
Alexandre Derumier
alexandre.derumier at groupe-cyllene.com
Tue Apr 22 13:51:26 CEST 2025
add a snapext option to enable the feature
When a snapshot is taken, the current volume is renamed to snap volname
and a current image is created with the snap volume as backing file
Signed-off-by: Alexandre Derumier <alexandre.derumier at groupe-cyllene.com>
---
src/PVE/Storage.pm | 5 +-
src/PVE/Storage/DirPlugin.pm | 1 +
src/PVE/Storage/Plugin.pm | 277 ++++++++++++++++++++++++++++++-----
3 files changed, 242 insertions(+), 41 deletions(-)
diff --git a/src/PVE/Storage.pm b/src/PVE/Storage.pm
index 1a37cc8..db9d190 100755
--- a/src/PVE/Storage.pm
+++ b/src/PVE/Storage.pm
@@ -348,13 +348,13 @@ sub volume_rollback_is_possible {
}
sub volume_snapshot {
- my ($cfg, $volid, $snap) = @_;
+ my ($cfg, $volid, $snap, $running) = @_;
my ($storeid, $volname) = parse_volume_id($volid, 1);
if ($storeid) {
my $scfg = storage_config($cfg, $storeid);
my $plugin = PVE::Storage::Plugin->lookup($scfg->{type});
- return $plugin->volume_snapshot($scfg, $storeid, $volname, $snap);
+ return $plugin->volume_snapshot($scfg, $storeid, $volname, $snap, $running);
} elsif ($volid =~ m|^(/.+)$| && -e $volid) {
die "snapshot file/device '$volid' is not possible\n";
} else {
@@ -378,7 +378,6 @@ sub volume_snapshot_rollback {
}
}
-# FIXME PVE 8.x remove $running parameter (needs APIAGE reset)
sub volume_snapshot_delete {
my ($cfg, $volid, $snap, $running) = @_;
diff --git a/src/PVE/Storage/DirPlugin.pm b/src/PVE/Storage/DirPlugin.pm
index 734309f..54d8d74 100644
--- a/src/PVE/Storage/DirPlugin.pm
+++ b/src/PVE/Storage/DirPlugin.pm
@@ -83,6 +83,7 @@ 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 85f761c..3f83fae 100644
--- a/src/PVE/Storage/Plugin.pm
+++ b/src/PVE/Storage/Plugin.pm
@@ -215,6 +215,11 @@ my $defaultData = {
maximum => 65535,
optional => 1,
},
+ 'snapext' => {
+ type => 'boolean',
+ description => 'enable external snapshot.',
+ optional => 1,
+ },
},
};
@@ -734,6 +739,8 @@ sub filesystem_path {
my ($vtype, $name, $vmid, undef, undef, $isBase, $format) =
$class->parse_volname($volname);
+ $name = $class->get_snap_name($volname, $snapname) if $scfg->{snapext} && $snapname;
+
# 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"
@@ -926,14 +933,8 @@ sub alloc_image {
umask $old_umask;
die $err if $err;
} else {
- my $cmd = ['/usr/bin/qemu-img', 'create'];
-
- my $prealloc_opt = preallocation_cmd_option($scfg, $fmt);
- push @$cmd, '-o', $prealloc_opt if defined($prealloc_opt);
- push @$cmd, '-f', $fmt, $path, "${size}K";
-
- eval { run_command($cmd, errmsg => "unable to create image"); };
+ eval { qemu_img_create($scfg, $fmt, $size, $path) };
if ($@) {
unlink $path;
rmdir $imagedir;
@@ -944,6 +945,19 @@ sub alloc_image {
return "$vmid/$name";
}
+sub alloc_snap_image {
+ my ($class, $storeid, $scfg, $volname, $backing_snap) = @_;
+
+ my $path = $class->path($scfg, $volname, $storeid);
+ my $backing_path = $class->path($scfg, $volname, $storeid, $backing_snap);
+
+ eval { qemu_img_create($scfg, 'qcow2', undef, $path, $backing_path) };
+ if ($@) {
+ unlink $path;
+ die "$@";
+ }
+}
+
sub free_image {
my ($class, $storeid, $scfg, $volname, $isBase, $format) = @_;
@@ -980,6 +994,51 @@ sub free_image {
# TODO taken from PVE/QemuServer/Drive.pm, avoiding duplication would be nice
my @checked_qemu_img_formats = qw(raw qcow qcow2 qed vmdk cloop);
+sub qemu_img_create {
+ my ($scfg, $fmt, $size, $path, $backing_path) = @_;
+
+ my $cmd = ['/usr/bin/qemu-img', 'create'];
+
+ my $options = [];
+
+ if($backing_path) {
+ push @$cmd, '-b', $backing_path, '-F', 'qcow2';
+ push @$options, 'extended_l2=on','cluster_size=128k';
+ };
+ push @$options, preallocation_cmd_option($scfg, $fmt);
+ push @$cmd, '-o', join(',', @$options) if @$options > 0;
+ push @$cmd, '-f', $fmt, $path;
+ push @$cmd, "${size}K" if !$backing_path;
+
+ run_command($cmd, errmsg => "unable to create image");
+}
+
+sub qemu_img_info {
+ my ($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 $untrusted if the file in question might be malicious since it isn't
# created by our stack
# this makes certain checks fatal, and adds extra checks for known problems like
@@ -1043,25 +1102,9 @@ sub file_size_info {
warn "file_size_info: '$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 $untrusted;
# skip decoding if there was no output, e.g. if there was a timeout.
@@ -1183,15 +1226,37 @@ sub volume_resize {
}
sub volume_snapshot {
- my ($class, $scfg, $storeid, $volname, $snap) = @_;
+ my ($class, $scfg, $storeid, $volname, $snap, $running) = @_;
die "can't snapshot this image format\n" if $volname !~ m/\.(qcow2|qed)$/;
- my $path = $class->filesystem_path($scfg, $volname);
+ if($scfg->{snapext}) {
+
+ if ($running) {
+ #rename with blockdev-reopen is done at qemu level when running
+ $class->alloc_snap_image($storeid, $scfg, $volname, $snap);
+ return;
+ }
- my $cmd = ['/usr/bin/qemu-img', 'snapshot','-c', $snap, $path];
+ #rename current volume to snap volume
+ my $vmid = ($class->parse_volname($volname))[2];
+ $class->rename_volume($scfg, $storeid, $volname, $vmid, undef, 'current', $snap);
- run_command($cmd);
+ $class->alloc_snap_image($storeid, $scfg, $volname, $snap);
+
+ if ($@) {
+ eval { $class->free_image($storeid, $scfg, $volname, 0) };
+ warn $@ if $@;
+ eval { $class->rename_volume($scfg, $storeid, $volname, $vmid, undef, $snap, 'current') };
+ warn $@ if $@;
+ }
+
+ } else {
+
+ my $path = $class->filesystem_path($scfg, $volname);
+ my $cmd = ['/usr/bin/qemu-img', 'snapshot','-c', $snap, $path];
+ run_command($cmd);
+ }
return undef;
}
@@ -1202,6 +1267,21 @@ 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 $parentsnap eq $snap;
+
+ die "can't rollback, '$snap' is not most recent snapshot on '$volname'\n";
+ }
+
return 1;
}
@@ -1212,9 +1292,21 @@ sub volume_snapshot_rollback {
my $path = $class->filesystem_path($scfg, $volname);
- my $cmd = ['/usr/bin/qemu-img', 'snapshot','-a', $snap, $path];
+ if ($scfg->{snapext}) {
+ #simply delete the current snapshot and recreate it
+ eval { $class->free_image($storeid, $scfg, $volname, 0) };
+ if ($@) {
+ die "can't delete old volume $volname: $@\n";
+ }
- run_command($cmd);
+ eval { $class->alloc_snap_image($storeid, $scfg, $volname, $snap) };
+ if ($@) {
+ die "can't allocate new volume $volname: $@\n";
+ }
+ } else {
+ my $cmd = ['/usr/bin/qemu-img', 'snapshot','-a', $snap, $path];
+ run_command($cmd);
+ }
return undef;
}
@@ -1224,15 +1316,65 @@ sub volume_snapshot_delete {
die "can't delete snapshot for this image format\n" if $volname !~ m/\.(qcow2|qed)$/;
- return 1 if $running;
-
+ my $cmd = "";
my $path = $class->filesystem_path($scfg, $volname);
- $class->deactivate_volume($storeid, $scfg, $volname, $snap, {});
+ if ($scfg->{snapext}) {
+
+ if ($running) {
+ my ($vtype, $name, $vmid, $basename, $basevmid, $isBase, $format) = $class->parse_volname($volname);
+ $volname = $class->get_snap_volname($volname, $snap);
+ $class->free_image($storeid, $scfg, $volname, $isBase, $format);
+ return;
+ }
+
+ my $snapshots = $class->volume_snapshot_info($scfg, $storeid, $volname);
+ my $snappath = $snapshots->{$snap}->{file};
+ my $snap_volname = $snapshots->{$snap}->{volname};
+ die "volume $snappath is missing" if !-e $snappath;
+
+ my $parentsnap = $snapshots->{$snap}->{parent};
+ my $childsnap = $snapshots->{$snap}->{child};
+ my $childpath = $snapshots->{$childsnap}->{file};
+
+ #if first snapshot,as it should be bigger, we merge child, and rename the snapshot to child
+ if(!$parentsnap) {
+ print "commit: merge content of $childpath into $snappath\n";
+ $cmd = ['/usr/bin/qemu-img', 'commit', $childpath];
+ eval { run_command($cmd) };
+ if ($@) {
+ die "error commiting $childpath to $snappath; $@\n";
+ }
+ print"rename $snappath to $childpath\n";
+ eval { rename($snappath, $childpath) };
+ if ($@) {
+ die "error renaming snapshot: $@\n";
+ }
+ } else {
+ #we rebase the child image on the parent as new backing image
+ my $parentpath = $snapshots->{$parentsnap}->{file};
+ print "rebase: merge diff content between $parentpath and $childpath into $childpath\n";
+ $cmd = ['/usr/bin/qemu-img', 'rebase', '-b', $parentpath, '-F', 'qcow2', '-f', 'qcow2', $childpath];
+ eval { run_command($cmd) };
+ if ($@) {
+ die "error rebase $childpath from $parentpath; $@\n";
+ }
+ #delete the snapshot
+ eval { $class->free_image($storeid, $scfg, $snap_volname, 0); };
+ if ($@) {
+ die "error delete old snapshot volume $snap_volname: $@\n";
+ }
+ }
+
+ } else {
- my $cmd = ['/usr/bin/qemu-img', 'snapshot','-d', $snap, $path];
+ return 1 if $running;
- run_command($cmd);
+ $class->deactivate_volume($storeid, $scfg, $volname, $snap, {});
+
+ $cmd = ['/usr/bin/qemu-img', 'snapshot','-d', $snap, $path];
+ run_command($cmd);
+ }
return undef;
}
@@ -1271,7 +1413,7 @@ 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},
},
};
@@ -1506,7 +1648,40 @@ 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, $volname);
+ my ($vtype, $name, $vmid, $basename, $basevmid, $isBase, $format) = $class->parse_volname($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) };
+ if ($@) {
+ die "Can't decode qemu snapshot list. Invalid JSON\n";
+ }
+ 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 $info;
}
sub activate_storage {
@@ -1907,4 +2082,30 @@ sub config_aware_base_mkdir {
}
}
+sub get_snap_name {
+ my ($class, $volname, $snapname) = @_;
+
+ my ($vtype, $name, $vmid, $basename, $basevmid, $isBase, $format) = $class->parse_volname($volname);
+ $name = !$snapname || $snapname eq 'current' ? $name : "snap-$snapname-$name";
+ return $name;
+}
+
+sub get_snap_volname {
+ my ($class, $volname, $snapname) = @_;
+
+ my $vmid = ($class->parse_volname($volname))[2];
+ my $name = $class->get_snap_name($volname, $snapname);
+ return "$vmid/$name";
+}
+
+sub parse_snapname {
+ my ($name) = @_;
+
+ my $basename = basename($name);
+ if ($basename =~ m/^snap-(.*)-vm(.*)$/) {
+ return $1;
+ }
+ return undef;
+}
+
1;
--
2.39.5
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