Re: [Qemu-devel] [PATCH 3/4] rbd: make qemu's cache setting override any ceph setting

[Jeff Cody <jcody@redhat.com>]

On Wed, Jun 10, 2015 at 08:28:45PM -0700, Josh Durgin wrote:
> To be safe, when cache=none is used ceph settings should not be able
> to override it to turn on caching. This was previously possible with
> rbd_cache=true in the rbd device configuration or a ceph configuration
> file. Similarly, rbd settings could have turned off caching when qemu
> requested it, although this would just be a performance problem.
> 
> Fix this by changing rbd's cache setting to match qemu after all other
> ceph settings have been applied.
> 
> Signed-off-by: Josh Durgin <jdurgin@redhat.com>
> ---
>  block/rbd.c | 24 ++++++++++++------------
>  1 file changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/block/rbd.c b/block/rbd.c
> index 50b5f6b..00d027d 100644
> --- a/block/rbd.c
> +++ b/block/rbd.c
> @@ -460,6 +460,18 @@ static int qemu_rbd_open(BlockDriverState *bs, QDict *options, int flags,
>          s->snap = g_strdup(snap_buf);
>      }
>  
> +    if (strstr(conf, "conf=") == NULL) {
> +        /* try default location, but ignore failure */
> +        rados_conf_read_file(s->cluster, NULL);
> +    }
> +
> +    if (conf[0] != '\0') {
> +        r = qemu_rbd_set_conf(s->cluster, conf, errp);
> +        if (r < 0) {
> +            goto failed_shutdown;
> +        }
> +    }
> +
>      /*
>       * Fallback to more conservative semantics if setting cache
>       * options fails. Ignore errors from setting rbd_cache because the
> @@ -473,18 +485,6 @@ static int qemu_rbd_open(BlockDriverState *bs, QDict *options, int flags,
>          rados_conf_set(s->cluster, "rbd_cache", "true");
>      }
>  
> -    if (strstr(conf, "conf=") == NULL) {
> -        /* try default location, but ignore failure */
> -        rados_conf_read_file(s->cluster, NULL);
> -    }
> -
> -    if (conf[0] != '\0') {
> -        r = qemu_rbd_set_conf(s->cluster, conf, errp);
> -        if (r < 0) {
> -            goto failed_shutdown;
> -        }
> -    }
> -
>      r = rados_connect(s->cluster);
>      if (r < 0) {
>          error_setg(errp, "error connecting");
> -- 
> 1.9.1
> 
Reviewed-by: Jeff Cody <jcody@redhat.com>