Re: [PATCH 3/3] xen/blkback: Check for insane amounts of request onthe ring.

[Konrad Rzeszutek Wilk]

On Fri, Jan 25, 2013 at 12:32:32PM -0500, Konrad Rzeszutek Wilk wrote:
> Check that the ring does not have an insane amount of requests
> (more than there could fit on the ring).
.. snip..
> diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
> index 2de3da9..4e9b028 100644
> --- a/drivers/block/xen-blkback/blkback.c
> +++ b/drivers/block/xen-blkback/blkback.c
> @@ -395,7 +395,7 @@ int xen_blkif_schedule(void *arg)
>  {
>  	struct xen_blkif *blkif = arg;
>  	struct xen_vbd *vbd = &blkif->vbd;
> -
> +	int rc = 0;
>  	xen_blkif_get(blkif);
>  
>  	while (!kthread_should_stop()) {
> @@ -415,8 +415,12 @@ int xen_blkif_schedule(void *arg)
>  		blkif->waiting_reqs = 0;
>  		smp_mb(); /* clear flag *before* checking for work */
>  
> -		if (do_block_io_op(blkif))
> +		rc = do_block_io_op(blkif);
> +		if (rc > 0)
>  			blkif->waiting_reqs = 1;
> +		if (rc == -EACCES)
> +			wait_event_interruptible(blkif->shutdown_wq,
> +						 kthread_should_stop());
>  
>  		if (log_stats && time_after(jiffies, blkif->st_print))
>  			print_stats(blkif);
> @@ -780,6 +784,9 @@ __do_block_io_op(struct xen_blkif *blkif)
>  		if (RING_REQUEST_CONS_OVERFLOW(&blk_rings->common, rc))
>  			break;
>  
> +		if (RING_REQUEST_PROD_OVERFLOW(&blk_rings->common, rc, rp))
> +			return -EACCES;
> +


With the new patch for RING_REQUEST_PROD_OVERFLOW I realized that the check
can actually be right before the loop, so: