Libguestfs - Jan 2011 - [PATCH] Don't use libvirt for volume information when converting with libvirtxml

Unless you're lucky, the target volumes won't be in a storage pool, so
libvirt
will return an error. For libvirtxml we know that the storage is local, so we
can inspect it directly. We use qemu-img to determine format and file size.
---
 lib/Sys/VirtV2V/Connection/LibVirtXMLSource.pm |   48 ++++++++++++++++++++---
 1 files changed, 41 insertions(+), 7 deletions(-)

diff --git a/lib/Sys/VirtV2V/Connection/LibVirtXMLSource.pm
b/lib/Sys/VirtV2V/Connection/LibVirtXMLSource.pm
index ffb9309..4bb5eb7 100644
--- a/lib/Sys/VirtV2V/Connection/LibVirtXMLSource.pm
+++ b/lib/Sys/VirtV2V/Connection/LibVirtXMLSource.pm
@@ -20,13 +20,14 @@ package Sys::VirtV2V::Connection::LibVirtXMLSource;
 use strict;
 use warnings;
 
+use File::stat;
 use Sys::Virt;
 use XML::DOM;
 use XML::DOM::XPath;
 
 use Sys::VirtV2V::Connection::Source;
 use Sys::VirtV2V::Transfer::Local;
-use Sys::VirtV2V::Util qw(user_message parse_libvirt_volinfo);
+use Sys::VirtV2V::Util qw(user_message);
 
 use Locale::TextDomain 'virt-v2v';
 
@@ -115,12 +116,45 @@ sub get_volume
     my $self = shift;
     my ($path) = @_;
 
-    # Use a libvirt session connection to inspect local volumes
-    my $vmm = Sys::Virt->new(uri => 'qemu:///session');
-    my $vol = $vmm->get_storage_volume_by_path($path);
-
-    my ($name, $format, $size, $usage, $is_sparse, $is_block) -       
parse_libvirt_volinfo($vol, $path);
+    # Use the output of qemu-img to inspect the path
+    open(my $qemuimg, '-|', 'env', 'LANG=C',
'qemu-img', 'info', $path)
+        or die("Unable to execute qemu-img: $!");
+
+    # qemu-img outputs data similar to:
+    # image: /var/lib/libvirt/images/p2v.img
+    # file format: raw
+    # virtual size: 8.0G (8589934592 bytes)
+    # disk size: 8.0G
+    my %info;
+    while(<$qemuimg>) {
+        next unless /^([^:]+):\s+(.*?)\s*$/;
+        $info{$1} = $2;
+    }
+
+    my (undef, undef, $name) = File::Spec->splitpath($path);
+    my $format = $info{'file format'};
+
+    my $vsize = $info{'virtual size'};
+    $vsize =~ /\s+\((\d+)\s+bytes\)$/
+        or die("qemu-img returned unexpected virtual size: $vsize");
+    my $size = $1;
+
+    # For $usage, $is_sparse and $is_block, we need to know if it's a block
+    # device
+    # N.B. qemu-img's 'disk size' output isn't useful here
+    my ($usage, $is_sparse, $is_block);
+    if (-b $path) {
+        $is_block = 1;
+        $usage = $size;
+        $is_sparse = 0;
+    } else {
+        $is_block = 0;
+        my $st = stat($path);
+        $usage = $st->blocks * 512;
+        $is_sparse = $usage < $size ? 1 : 0;
+    }
+
+    die("size ($size) < usage ($usage)") if $size < $usage;
 
     my $transfer = new Sys::VirtV2V::Transfer::Local($path, $format,
                                                      $is_sparse);
-- 
1.7.3.5

On Wed, Jan 26, 2011 at 02:34:49PM +0000, Matthew Booth
wrote:
> Unless you're lucky, the target volumes won't be in a storage pool,
so libvirt
> will return an error. For libvirtxml we know that the storage is local, so
we
> can inspect it directly. We use qemu-img to determine format and file size.
[...]
> +    # Use the output of qemu-img to inspect the path
> +    open(my $qemuimg, '-|', 'env', 'LANG=C',
'qemu-img', 'info', $path)
> +        or die("Unable to execute qemu-img: $!");
You need to make sure qemu-img is an explicit Requires in the
spec file, ie:

  Requires: /usr/bin/qemu-img

and it should be mentioned in the README file too for other distros.
Also other distros name this differently, eg: 'kvm-qemu-img' and maybe
other variations.
> +    # For $usage, $is_sparse and $is_block, we need to know if it's a
block
> +    # device
> +    # N.B. qemu-img's 'disk size' output isn't useful here
> +    my ($usage, $is_sparse, $is_block);
> +    if (-b $path) {
> +        $is_block = 1;
> +        $usage = $size;
> +        $is_sparse = 0;
> +    } else {
> +        $is_block = 0;
> +        my $st = stat($path);
> +        $usage = $st->blocks * 512;
> +        $is_sparse = $usage < $size ? 1 : 0;
> +    }
> +
> +    die("size ($size) < usage ($usage)") if $size <
$usage;
Agreed that qemu-img gets it wrong:

# qemu-img info /dev/vg_pin/CentOS5x64 
image: /dev/vg_pin/CentOS5x64
file format: raw
virtual size: 10G (10737418240 bytes)
disk size: 0

*but* I'm not sure your code is correct.  I don't know if $st->blocks
is always valid, and you can't assume 512-sized blocks.

I suggest calling 'blockdev --getsize64', with the caveats above about
dependencies and README file.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
virt-p2v converts physical machines to virtual machines.  Boot with a
live CD or over the network (PXE) and turn machines into Xen guests.
http://et.redhat.com/~rjones/virt-p2v