Re: [Xen-devel] [PATCH v5 5/7] xen/9pfs: send requests to the backend

[Juergen Gross <jgross@xxxxxxxx>]

On 20/03/17 18:59, Stefano Stabellini wrote:
> Implement struct p9_trans_module create and close functions by looking
> at the available Xen 9pfs frontend-backend connections. We don't expect
> many frontend-backend connections, thus walking a list is OK.
> 
> Send requests to the backend by copying each request to one of the
> available rings (each frontend-backend connection comes with multiple
> rings). Handle the ring and notifications following the 9pfs
> specification. If there are not enough free bytes on the ring for the
> request, wait on the wait_queue: the backend will send a notification
> after consuming more requests.
> 
> Signed-off-by: Stefano Stabellini <stefano@xxxxxxxxxxx>
> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> CC: groug@xxxxxxxx
> CC: jgross@xxxxxxxx
> CC: Eric Van Hensbergen <ericvh@xxxxxxxxx>
> CC: Ron Minnich <rminnich@xxxxxxxxxx>
> CC: Latchesar Ionkov <lucho@xxxxxxxxxx>
> CC: v9fs-developer@xxxxxxxxxxxxxxxxxxxxx
> ---
>  net/9p/trans_xen.c | 91 
> ++++++++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 89 insertions(+), 2 deletions(-)
> 
> diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c
> index 5279ae0..e51edac 100644
> --- a/net/9p/trans_xen.c
> +++ b/net/9p/trans_xen.c

> +static int p9_xen_write_todo(struct xen_9pfs_dataring *ring, RING_IDX size)
> +{
> +     RING_IDX cons, prod;
> +
> +     cons = ring->intf->out_cons;
> +     prod = ring->intf->out_prod;
> +     virt_mb();
> +
> +     if (XEN_9PFS_RING_SIZE - xen_9pfs_queued(prod, cons,
> +                                              XEN_9PFS_RING_SIZE) >= size)
> +             return 1;
> +     else
> +             return 0;
>  }

Make return type of function bool and use:

return XEN_9PFS_RING_SIZE - xen_9pfs_queued(prod, cons,
                                            XEN_9PFS_RING_SIZE) >= size;

and further below ...

>  
>  static int p9_xen_request(struct p9_client *client, struct p9_req_t *p9_req)
>  {
> +     struct xen_9pfs_front_priv *priv = NULL;
> +     RING_IDX cons, prod, masked_cons, masked_prod;
> +     unsigned long flags;
> +     u32 size = p9_req->tc->size;
> +     struct xen_9pfs_dataring *ring;
> +     int num;
> +
> +     read_lock(&xen_9pfs_lock);
> +     list_for_each_entry(priv, &xen_9pfs_devs, list) {
> +             if (priv->client == client)
> +                     break;
> +     }
> +     read_unlock(&xen_9pfs_lock);
> +     if (!priv || priv->client != client)
> +             return -EINVAL;
> +
> +     num = p9_req->tc->tag % priv->num_rings;
> +     ring = &priv->rings[num];
> +
> +again:
> +     while (wait_event_interruptible(ring->wq,
> +                                     p9_xen_write_todo(ring, size) > 0) != 0)

... you can omit the "> 0".


Juergen

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