Libguestfs - Apr 2010 - [PATCH] Target::LibVirt: Don't truncate a volume when opening it

perl's '>' open mode truncates by default, and will create a new
file if
necessary. We don't want to truncate an existing volume when writing to it,
and
it's an error if the volume doesn't already exist. Use sysopen to be
explicit
about this.
---
 lib/Sys/VirtV2V/Target/LibVirt.pm |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/lib/Sys/VirtV2V/Target/LibVirt.pm
b/lib/Sys/VirtV2V/Target/LibVirt.pm
index c8802ac..99a1ad2 100644
--- a/lib/Sys/VirtV2V/Target/LibVirt.pm
+++ b/lib/Sys/VirtV2V/Target/LibVirt.pm
@@ -20,6 +20,8 @@ use warnings;
 
 package Sys::VirtV2V::Target::LibVirt::Vol;
 
+use POSIX;
+
 use Sys::VirtV2V::UserMessage qw(user_message);
 
 sub _new
@@ -106,7 +108,9 @@ sub open
     my $self = shift;
 
     my $path = $self->get_path();
-    open(my $fd, '>', $path)
+
+    # We want to open the existing volume without truncating it
+    sysopen(my $fd, $path, O_WRONLY)
         or die(user_message(__x("Error opening storage volume {path}
".
                                 "for writing: {error}", error =>
$!)));
 
-- 
1.6.6.1

On Wed, Apr 07, 2010 at 12:05:37PM +0100, Matthew Booth
wrote:
> perl's '>' open mode truncates by default, and will create a
new file if
> necessary. We don't want to truncate an existing volume when writing to
it, and
> it's an error if the volume doesn't already exist. Use sysopen to
be explicit
> about this.
> ---
>  lib/Sys/VirtV2V/Target/LibVirt.pm |    6 +++++-
>  1 files changed, 5 insertions(+), 1 deletions(-)
> 
> diff --git a/lib/Sys/VirtV2V/Target/LibVirt.pm
b/lib/Sys/VirtV2V/Target/LibVirt.pm
> index c8802ac..99a1ad2 100644
> --- a/lib/Sys/VirtV2V/Target/LibVirt.pm
> +++ b/lib/Sys/VirtV2V/Target/LibVirt.pm
> @@ -20,6 +20,8 @@ use warnings;
>  
>  package Sys::VirtV2V::Target::LibVirt::Vol;
>  
> +use POSIX;
> +
>  use Sys::VirtV2V::UserMessage qw(user_message);
>  
>  sub _new
> @@ -106,7 +108,9 @@ sub open
>      my $self = shift;
>  
>      my $path = $self->get_path();
> -    open(my $fd, '>', $path)
> +
> +    # We want to open the existing volume without truncating it
> +    sysopen(my $fd, $path, O_WRONLY)
NB There's no need to switch to sysopen. You can use '>>'
instead of '>' if you
want to append instead of truncate


Daniel
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On Wed, Apr 07, 2010 at 12:05:37PM +0100, Matthew Booth
wrote:
> perl's '>' open mode truncates by default, and will create a
new file if
> necessary. We don't want to truncate an existing volume when writing to
it, and
> it's an error if the volume doesn't already exist. Use sysopen to
be explicit
> about this.
Yes, looks fine.  ACK.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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