[libvirt] [PATCHv2 08/33] storage: Add storage file API to read file headers

[Eric Blake]

On 05/22/2014 07:47 AM, Peter Krempa wrote:
> Add storage driver based functions to access headers of storage files
> for metadata extraction. Along with this patch a local filesystem and
> gluster via libgfapi implementation is provided. The gluster
> implementation is based on code of the saferead_lim function.
> ---
>  src/storage/storage_backend.h         |  7 ++++
>  src/storage/storage_backend_fs.c      | 30 ++++++++++++++++
>  src/storage/storage_backend_gluster.c | 66 +++++++++++++++++++++++++++++++++++
>  src/storage/storage_driver.c          | 40 +++++++++++++++++++++
>  src/storage/storage_driver.h          |  3 ++
>  5 files changed, 146 insertions(+)
> 

> +++ b/src/storage/storage_backend_gluster.c
> @@ -638,6 +638,71 @@ virStorageFileBackendGlusterStat(virStorageSourcePtr src,
>  }
> 
> 
> +static ssize_t
> +virStorageFileBackendGlusterReadHeader(virStorageSourcePtr src,
> +                                       ssize_t max_len,
> +                                       char **buf)
> +{
> +    virStorageFileBackendGlusterPrivPtr priv = src->drv->priv;
> +    glfs_fd_t *fd = NULL;
> +    size_t alloc = 0;
> +    size_t size = 0;
> +    int save_errno;
> +    ssize_t ret = -1;
> +
> +    *buf = NULL;
> +
> +    if (!(fd = glfs_open(priv->vol, src->path, O_RDONLY))) {
> +        virReportSystemError(errno, _("Failed to open file '%s'"),
> +                             src->path);
> +        goto cleanup;
> +    }
> +
> +    /* code below is shamelesly stolen from saferead_lim */

s/shamelesly/shamelessly/


> +    if (!src->drv->backend->storageFileReadHeader) {
> +        virReportError(VIR_ERR_INTERNAL_ERROR,
> +                       _("storage file header reading is not supported for "
> +                         "storage type %s (protocol: %s)'"),
> +                       virStorageTypeToString(src->type),
> +                       virStorageNetProtocolTypeToString(src->protocol));

Oh slick - the earlier patch that adds protocol==0 as "none" rather than
"nbd" makes this message tolerable even for non-network storage types.
Less special-casing is always good :)

> +        return -1;

Isn't this supposed to be 'return -2' according to the function
documentation?

ACK if you agree about the return value fix, and if it is the only
change you make besides the typo fix.

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

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