[libvirt] [PATCH] Access qemu backing_file with relative pool path

[Daniel P. Berrange]

On Thu, Mar 03, 2011 at 09:06:25PM -0600, Jesse Cook wrote:
> This patch enables the relative backing file path support provided by
> qemu-img create.
> 
> If the storage pool is not found with the specified path, check if the
> file exists relative to the pool where the new image will be created by
> prepending the storage pool path.
> ---
>  src/storage/storage_backend.c |   32 ++++++++++++++++++++++++++++----
>  1 files changed, 28 insertions(+), 4 deletions(-)
> 
> diff --git a/src/storage/storage_backend.c b/src/storage/storage_backend.c
> index 2eede74..bb49f22 100644
> --- a/src/storage/storage_backend.c
> +++ b/src/storage/storage_backend.c
> @@ -687,10 +687,34 @@ virStorageBackendCreateQemuImg(virConnectPtr conn,
>              return -1;
>          }
>          if (access(vol->backingStore.path, R_OK) != 0) {
> -            virReportSystemError(errno,
> -                                 _("inaccessible backing store volume %s"),
> -                                 vol->backingStore.path);
> -            return -1;
> +            /* If the backing store image is not found with the specified path,
> +             * check for the file relative to the pool path. */
> +            int accessRetCode = -1;
> +
> +            char *absolutePath = NULL;
> +
> +            virBuffer absPathBuf = VIR_BUFFER_INITIALIZER;
> +
> +            virBufferVSprintf(&absPathBuf,
> +                              "%s/%s",
> +                              pool->def->target.path,
> +                              vol->backingStore.path);
> +
> +            if (virBufferError(&absPathBuf)) {
> +                virBufferFreeAndReset(&absPathBuf);
> +                virReportOOMError();
> +                return -1;
> +            }
> +
> +            absolutePath = virBufferContentAndReset(&absPathBuf);

Since you're only doing one single virBufferVSprintf() call, using
virBuffer is overkill. You can get away with the simpler

   virAsprintf(&absolutePath, "%s/%s",
               pool->def->target.path,
               vol->backingStore.path);

> +            accessRetCode = access(absolutePath, R_OK);
> +            VIR_FREE(absolutePath);
> +            if (accessRetCode != 0) {
> +                virReportSystemError(errno,
> +                                     _("inaccessible backing store volume %s"),
> +                                     vol->backingStore.path);
> +                return -1;
> +            }
>          }
>      }

Regards,
Daniel
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