On 08/07/13 14:03, Roger Pau Monne wrote:
> Improve the calculation of required grants to process a request by
> using nr_phys_segments instead of always assuming a request is going
> to use all posible segments.
This isn't obviously correct to me. Why is this correct value for the
number of pages that need to be granted?
David
> --- a/drivers/block/xen-blkfront.c
> +++ b/drivers/block/xen-blkfront.c
> @@ -400,10 +400,13 @@ static int blkif_queue_request(struct request *req)
> if (unlikely(info->connected != BLKIF_STATE_CONNECTED))
> return 1;
>
> - max_grefs = info->max_indirect_segments ?
> - info->max_indirect_segments +
> - INDIRECT_GREFS(info->max_indirect_segments) :
> - BLKIF_MAX_SEGMENTS_PER_REQUEST;
> + max_grefs = req->nr_phys_segments;
> + if (max_grefs > BLKIF_MAX_SEGMENTS_PER_REQUEST)
> + /*
> + * If we are using indirect segments we need to account
> + * for the indirect grefs used in the request.
> + */
> + max_grefs += INDIRECT_GREFS(req->nr_phys_segments);
>
> /* Check if we have enough grants to allocate a requests */
> if (info->persistent_gnts_c < max_grefs) {
--
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