[libvirt] [PATCH 1/7] Add virFileTouch for creating empty files

[Eric Blake]

On 01/11/2012 09:33 AM, Daniel P. Berrange wrote:
> From: "Daniel P. Berrange" <berrange at redhat.com>
> 
> Add a virFileTouch API which ensures that a file will always
> exist, even if zero length
> 
> * src/lxc/lxc_container.c, src/util/virfile.h: virFileTouch

This line is not quite accurate,

> ---
>  src/util/virfile.c |   21 +++++++++++++++++++++
>  src/util/virfile.h |    2 ++
>  2 files changed, 23 insertions(+), 0 deletions(-)

to this diffstat (drop lxc_container).  Otherwise, looks like a useful API.

> 
> diff --git a/src/util/virfile.c b/src/util/virfile.c
> index cbc3fcc..e6b469c 100644
> --- a/src/util/virfile.c
> +++ b/src/util/virfile.c
> @@ -390,3 +390,24 @@ cleanup:
>      }
>      return ret;
>  }
> +
> +
> +int virFileTouch(const char *path, mode_t mode)
> +{
> +    int fd = -1;
> +
> +    if ((fd = open(path, O_WRONLY | O_CREAT, mode)) < 0) {
> +        virReportSystemError(errno, _("cannot create file '%s'"),
> +                             path);
> +        return -1;

Should we be using virFileOpenAs() for the sake of touching a file with
different permissions on a root-squash NFS server?

In particular, I wonder if any of qemu_driver.c could reuse this
function, if it were to use virFileOpenAs() - for example, creating a
qemu snapshot requires that a file already exist and be empty before
making the monitor call.

ACK - any change to use virFileOpenAs can come as a later patch.

-- 
Eric Blake   eblake at redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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