Re: [Qemu-devel] [PATCH 09/10] block/qapi: Ignore filters on top for format name

["Benoît Canet" <benoit.canet@irqsave.net>]

The Monday 03 Mar 2014 à 16:28:52 (+0100), Max Reitz wrote :
> bdrv_query_image_info() currently deduces the image filename and the
> format name from the top BDS. However, it is probably more reasonable to
> ignore as many filters as possible on top of the BDS chain since those
> neither change the type nor the filename of the underlying image.
> 
> Filters like quorum which have multiple underlying BDS should not be
> removed, however, since the underlying BDS chains may lead to different
> image formats and most certainly to different filenames. Therefore, only
> simple filters with a single underlying BDS may be skipped.
> 
> In addition, any "raw" BDS on top of such a simple filter should be
> removed, since they have probably been automatically created by
> bdrv_open() but basically function as a simple filter as well.
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  block/qapi.c | 20 ++++++++++++++++++--
>  1 file changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/block/qapi.c b/block/qapi.c
> index 8f2b4db..c4ddced 100644
> --- a/block/qapi.c
> +++ b/block/qapi.c
> @@ -171,11 +171,27 @@ void bdrv_query_image_info(BlockDriverState *bs,
>      int ret;
>      Error *err = NULL;
>      ImageInfo *info = g_new0(ImageInfo, 1);
> +    BlockDriverState *ubs;
>  
>      bdrv_get_geometry(bs, &total_sectors);
>  
> -    info->filename        = g_strdup(bs->filename);
> -    info->format          = g_strdup(bdrv_get_format_name(bs));
> +    /* Remove the top layer of filters; that is, remove every "raw" BDS on top
> +     * of a simple filter and every simple filter itself until a BDS is
> +     * encountered which cannot be removed through these rules; a simple filter
> +     * is a filter BDS which has its child in .file (that is,
> +     * bdrv_recurse_is_first_non_filter is NULL). */
> +    ubs = bs;
> +    while ((ubs->drv && ubs->drv->authorizations[BS_IS_A_FILTER]) ||
> +           (ubs->drv && !strcmp(ubs->drv->format_name, "raw") && ubs->file &&
> +            ubs->file->drv && ubs->file->drv->authorizations[BS_IS_A_FILTER] &&
> +            !ubs->file->drv->bdrv_recurse_is_first_non_filter))
> +    {
> +        ubs = ubs->file;
> +    }

The rewrite Paolo asked me to do don't allow to do it anymore: there is no
distinction between simple filter driver and quorum like filter drivers.

Maybe this rewrite was not so nice.

Best regards

Benoît

> +
> +    info->filename        = g_strdup(ubs->filename);
> +    info->format          = g_strdup(bdrv_get_format_name(ubs));
> +
>      info->virtual_size    = total_sectors * 512;
>      info->actual_size     = bdrv_get_allocated_file_size(bs);
>      info->has_actual_size = info->actual_size >= 0;
> -- 
> 1.9.0
> 
>