Re: [Qemu-devel] [RFC v9 22/27] virtio-blk: Fix request merging

[Michael S. Tsirkin]

On Wed, Jul 18, 2012 at 04:07:49PM +0100, Stefan Hajnoczi wrote:
> Khoa Huynh <address@hidden> discovered that request merging is broken.
> The merged iocb is not updated to reflect the total number of iovecs and
> the offset is also outdated.
> 
> This patch fixes request merging.
> 
> Signed-off-by: Stefan Hajnoczi <address@hidden>

So all these fixups need to be folded in making it correct first time.

> ---
>  hw/virtio-blk.c |   10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
> index 9131a7a..51807b5 100644
> --- a/hw/virtio-blk.c
> +++ b/hw/virtio-blk.c
> @@ -178,13 +178,17 @@ static void merge_request(struct iocb *iocb_a, struct 
> iocb *iocb_b)
>          req_a->len = iocb_nbytes(iocb_a);
>      }
>  
> -    iocb_b->u.v.vec = iovec;
> -    req_b->len = iocb_nbytes(iocb_b);
> -    req_b->next_merged = req_a;
>      /*
>      fprintf(stderr, "merged %p (%u) and %p (%u), %u iovecs in total\n",
>              req_a, iocb_a->u.v.nr, req_b, iocb_b->u.v.nr, iocb_a->u.v.nr + 
> iocb_b->u.v.nr);
>      */
> +
> +    iocb_b->u.v.vec = iovec;
> +    iocb_b->u.v.nr += iocb_a->u.v.nr;
> +    iocb_b->u.v.offset = iocb_a->u.v.offset;
> +
> +    req_b->len = iocb_nbytes(iocb_b);
> +    req_b->next_merged = req_a;
>  }
>  
>  static void process_request(IOQueue *ioq, struct iovec iov[], unsigned int 
> out_num, unsigned int in_num, unsigned int head)
> -- 
> 1.7.10.4