Re: [PATCH 4/4] block/file: Add file-specific image info

[Eric Blake]

On Tue, May 03, 2022 at 04:55:29PM +0200, Hanna Reitz wrote:
> Add some (optional) information that the file driver can provide for
> image files, namely the extent size.
> 
> Signed-off-by: Hanna Reitz <hreitz@redhat.com>
> ---
>  qapi/block-core.json | 26 ++++++++++++++++++++++++--
>  block/file-posix.c   | 30 ++++++++++++++++++++++++++++++
>  2 files changed, 54 insertions(+), 2 deletions(-)
> 

> +++ b/block/file-posix.c
> @@ -3068,6 +3068,34 @@ static int raw_get_info(BlockDriverState *bs, 
> BlockDriverInfo *bdi)
>      return 0;
>  }
>  
> +static ImageInfoSpecific *raw_get_specific_info(BlockDriverState *bs,
> +                                                Error **errp)
> +{
> +    BDRVRawState *s = bs->opaque;
> +    ImageInfoSpecificFile *file_info = g_new0(ImageInfoSpecificFile, 1);
> +    ImageInfoSpecific *spec_info = g_new(ImageInfoSpecific, 1);
> +
> +    *spec_info = (ImageInfoSpecific){
> +        .type = IMAGE_INFO_SPECIFIC_KIND_FILE,
> +        .u.file.data = file_info,
> +    };
> +
> +#ifdef FS_IOC_FSGETXATTR
> +    {
> +        struct fsxattr attr;
> +        int ret;
> +
> +        ret = ioctl(s->fd, FS_IOC_FSGETXATTR, &attr);
> +        if (!ret && attr.fsx_extsize != 0) {
> +            file_info->has_extent_size = true;
> +            file_info->extent_size = attr.fsx_extsize;
> +        }
> +    }
> +#endif

Can/should we fall back to stat's st_blksize when the ioctl produces
nothing?

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org