Re: [PATCH 6/7] xen/9pfs: receive responses

[Boris Ostrovsky <boris.ostrovsky@oracle.com>]

On 03/06/2017 03:01 PM, Stefano Stabellini wrote:
> Upon receiving a notification from the backend, schedule the
> p9_xen_response work_struct. p9_xen_response checks if any responses are
> available, if so, it reads them one by one, calling p9_client_cb to send
> them up to the 9p layer (p9_client_cb completes the request). Handle the
> ring following the Xen 9pfs specification.
> 
> Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
> CC: boris.ostrovsky@oracle.com
> CC: jgross@suse.com
> CC: Eric Van Hensbergen <ericvh@gmail.com>
> CC: Ron Minnich <rminnich@sandia.gov>
> CC: Latchesar Ionkov <lucho@ionkov.net>
> CC: v9fs-developer@lists.sourceforge.net
> ---
>  net/9p/trans_xen.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 53 insertions(+)
> 
> diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c
> index 4e26556..1ca9246 100644
> --- a/net/9p/trans_xen.c
> +++ b/net/9p/trans_xen.c
> @@ -149,6 +149,59 @@ static int p9_xen_request(struct p9_client *client, struct p9_req_t *p9_req)
>  
>  static void p9_xen_response(struct work_struct *work)
>  {
> +	struct xen_9pfs_front_priv *priv;
> +	struct xen_9pfs_dataring *ring;
> +	RING_IDX cons, prod, masked_cons, masked_prod;
> +	struct xen_9pfs_header h;
> +	struct p9_req_t *req;
> +	int status = REQ_STATUS_ERROR;


Doesn't this need to go inside the loop?

> +
> +	ring = container_of(work, struct xen_9pfs_dataring, work);
> +	priv = ring->priv;
> +
> +	while (1) {
> +		cons = ring->intf->in_cons;
> +		prod = ring->intf->in_prod;
> +		rmb();


Is this rmb() or mb()? (Or, in fact, virt_XXX()?) You used mb() in the
previous patch.


> +
> +		if (xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE) < sizeof(h)) {
> +			notify_remote_via_irq(ring->irq);
> +			return;
> +		}
> +
> +		masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE);
> +		masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE);
> +
> +		xen_9pfs_read_packet(ring->ring.in,
> +				masked_prod, &masked_cons,
> +				XEN_9PFS_RING_SIZE, &h, sizeof(h));
> +
> +		req = p9_tag_lookup(priv->client, h.tag);
> +		if (!req || req->status != REQ_STATUS_SENT) {
> +			dev_warn(&priv->dev->dev, "Wrong req tag=%x\n", h.tag);
> +			cons += h.size;
> +			mb();
> +			ring->intf->in_cons = cons;
> +			continue;


I don't know what xen_9pfs_read_packet() does so perhaps it's done there
but shouldn't the pointers be updated regardless of the 'if' condition?

-boris


> +		}
> +
> +		memcpy(req->rc, &h, sizeof(h));
> +		req->rc->offset = 0;
> +
> +		masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE);
> +		xen_9pfs_read_packet(ring->ring.in,
> +				masked_prod, &masked_cons,
> +				XEN_9PFS_RING_SIZE, req->rc->sdata, h.size);
> +
> +		mb();
> +		cons += h.size;
> +		ring->intf->in_cons = cons;
> +
> +		if (req->status != REQ_STATUS_ERROR)
> +			status = REQ_STATUS_RCVD;
> +
> +		p9_client_cb(priv->client, req, status);
> +	}
>  }
>  
>  static irqreturn_t xen_9pfs_front_event_handler(int irq, void *r)
>