[sheepdog] [Qemu-devel] [PATCH v5] sheepdog: add discard/trim support for sheepdog

[Stefan Hajnoczi]

On Tue, Apr 16, 2013 at 12:15:04AM +0800, Liu Yuan wrote:
> @@ -727,6 +730,20 @@ static void coroutine_fn aio_read_response(void *opaque)
>              rsp.result = SD_RES_SUCCESS;
>          }
>          break;
> +    case AIOCB_DISCARD_OBJ:
> +        switch (rsp.result) {
> +        case SD_RES_INVALID_PARMS:
> +            error_report("you are running the old sheep that doesn't support "
> +                         "discard command.\n");

error_report() does not need '\n'.

The recently added ssh block driver has a similar case when the server
does not support fsync.  It does the following:

1. Print the error message once only per volume, avoid filling up logs
   on the host.
2. Include details of the volume/server in case the users is connected
   to multiple volumes/servers.  This allows them to figure out which
   server is outdated.

This makes the error messages safe from denial-of-service and includes
more useful information.