Re: [PATCH] block/rbd: report a better error when namespace does not exist

[Ilya Dryomov]

On Mon, May 16, 2022 at 12:03 PM Stefano Garzarella <sgarzare@redhat.com> wrote:
>
> If the namespace does not exist, rbd_create() fails with -ENOENT and
> QEMU reports a generic "error rbd create: No such file or directory":
>
>     $ qemu-img create rbd:rbd/namespace/image 1M
>     Formatting 'rbd:rbd/namespace/image', fmt=raw size=1048576
>     qemu-img: rbd:rbd/namespace/image: error rbd create: No such file or 
> directory
>
> Unfortunately rados_ioctx_set_namespace() does not fail if the namespace
> does not exist, so let's use rbd_namespace_exists() in qemu_rbd_connect()
> to check if the namespace exists, reporting a more understandable error:
>
>     $ qemu-img create rbd:rbd/namespace/image 1M
>     Formatting 'rbd:rbd/namespace/image', fmt=raw size=1048576
>     qemu-img: rbd:rbd/namespace/image: namespace 'namespace' does not exist
>
> Reported-by: Tingting Mao <timao@redhat.com>
> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> ---
>  meson.build |  6 ++++++
>  block/rbd.c | 24 ++++++++++++++++++++++++
>  2 files changed, 30 insertions(+)
>
> diff --git a/meson.build b/meson.build
> index 9b20dcd143..e6c0afd62b 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -1828,6 +1828,12 @@ config_host_data.set('HAVE_GETIFADDRS', 
> cc.has_function('getifaddrs'))
>  config_host_data.set('HAVE_OPENPTY', cc.has_function('openpty', 
> dependencies: util))
>  config_host_data.set('HAVE_STRCHRNUL', cc.has_function('strchrnul'))
>  config_host_data.set('HAVE_SYSTEM_FUNCTION', cc.has_function('system', 
> prefix: '#include <stdlib.h>'))
> +if rbd.found()
> +  config_host_data.set('HAVE_RBD_NAMESPACE_EXISTS',
> +                       cc.has_function('rbd_namespace_exists',
> +                                       dependencies: rbd,
> +                                       prefix: '#include <rbd/librbd.h>'))
> +endif
>  if rdma.found()
>    config_host_data.set('HAVE_IBV_ADVISE_MR',
>                         cc.has_function('ibv_advise_mr',
> diff --git a/block/rbd.c b/block/rbd.c
> index 6caf35cbba..0ff23c5b26 100644
> --- a/block/rbd.c
> +++ b/block/rbd.c
> @@ -831,6 +831,26 @@ static int qemu_rbd_connect(rados_t *cluster, 
> rados_ioctx_t *io_ctx,
>          error_setg_errno(errp, -r, "error opening pool %s", opts->pool);
>          goto failed_shutdown;
>      }
> +
> +#ifdef HAVE_RBD_NAMESPACE_EXISTS
> +    if (opts->has_q_namespace && strlen(opts->q_namespace) > 0) {
> +        bool exists;
> +
> +        r = rbd_namespace_exists(*io_ctx, opts->q_namespace, &exists);
> +        if (r != 0) {

Nit: r < 0 for consistency (librbd errors are always negative).

> +            error_setg_errno(errp, -r, "error checking namespace");
> +            goto failed_ioctx_destroy;
> +        }
> +
> +        if (!exists) {
> +            error_setg(errp, "namespace '%s' does not exist",
> +                       opts->q_namespace);
> +            r = -ENOENT;
> +            goto failed_ioctx_destroy;
> +        }
> +    }
> +#endif
> +
>      /*
>       * Set the namespace after opening the io context on the pool,
>       * if nspace == NULL or if nspace == "", it is just as we did nothing
> @@ -840,6 +860,10 @@ static int qemu_rbd_connect(rados_t *cluster, 
> rados_ioctx_t *io_ctx,
>      r = 0;
>      goto out;
>
> +#ifdef HAVE_RBD_NAMESPACE_EXISTS
> +failed_ioctx_destroy:
> +    rados_ioctx_destroy(*io_ctx);
> +#endif
>  failed_shutdown:
>      rados_shutdown(*cluster);
>  out:
> --
> 2.35.3
>

Reviewed-by: Ilya Dryomov <idryomov@gmail.com>

Thanks,

                Ilya