Re: [Qemu-devel] [PATCH 2/2] block/rbd: Attempt to parse legacy filenames

[Jeff Cody <jcody@redhat.com>]

On Tue, Sep 11, 2018 at 01:15:49AM -0400, Jeff Cody wrote:
> When we converted rbd to get rid of the older key/value-centric
> encoding format, we broke compatibility with image files with backing
> file strings encoded in the old format.
> 
> This leaves a bit of an ugly conundrum, and a hacky solution.
> 
> If the initial attempt to parse the "proper" options fails, it assumes
> that we may have an older key/value encoded filename.  Fall back to
> attempting to parse the filename, and extract the required options from
> it.  If that fails, pass along the original error message.
> 
> This approach has a potential drawback: if for some reason there are
> some options supplied the new way, and some the old way, we may not
> catch all the old options if they are not required options (since it
> won't cause the initial failure).
> 
> Signed-off-by: Jeff Cody <jcody@redhat.com>
> ---
>  block/rbd.c | 30 +++++++++++++++++++++++++++---
>  1 file changed, 27 insertions(+), 3 deletions(-)
> 
> diff --git a/block/rbd.c b/block/rbd.c
> index a8e79d01d2..bce86b8bde 100644
> --- a/block/rbd.c
> +++ b/block/rbd.c
> @@ -685,7 +685,7 @@ static int qemu_rbd_open(BlockDriverState *bs, QDict *options, int flags,
>      BlockdevOptionsRbd *opts = NULL;
>      const QDictEntry *e;
>      Error *local_err = NULL;
> -    char *keypairs, *secretid;
> +    char *keypairs, *secretid, *filename;
>      int r;
>  
>      keypairs = g_strdup(qdict_get_try_str(options, "=keyvalue-pairs"));
> @@ -700,8 +700,32 @@ static int qemu_rbd_open(BlockDriverState *bs, QDict *options, int flags,
>  
>      r = qemu_rbd_convert_options(bs, options, &opts, &local_err);
>      if (local_err) {
> -        error_propagate(errp, local_err);
> -        goto out;
> +        /* If the initial attempt to convert and process the options failed,
> +         * we may be attempting to open an image file that has the rbd options
> +         * specified in the older format consisting of all key/value pairs
> +         * encoded in the filename.  Go ahead and attempt to parse the
> +         * filename, and see if we can pull out the required options */
> +        Error *parse_err = NULL;
> +
> +        filename = g_strdup(qdict_get_try_str(options, "filename"));

I'm leaking filename, I'll clean that up (along with any other comments) in
v2.

> +        qdict_del(options, "filename");
> +
> +        qemu_rbd_parse_filename(filename, options, NULL);
> +
> +        g_free(keypairs);
> +        keypairs = g_strdup(qdict_get_try_str(options, "=keyvalue-pairs"));
> +        if (keypairs) {
> +            qdict_del(options, "=keyvalue-pairs");
> +        }
> +
> +        r = qemu_rbd_convert_options(bs, options, &opts, &parse_err);
> +        if (parse_err) {
> +            /* if the second attempt failed, pass along the original error
> +             * message for the current format */
> +            error_propagate(errp, local_err);
> +            error_free(parse_err);
> +            goto out;
> +        }
>      }
>  
>      /* Remove the processed options from the QDict (the visitor processes
> -- 
> 2.17.1
>