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SubjectRe: [PATCH v2 07/13] xen/pvcalls: implement accept command
On Wed, 26 Jul 2017, Boris Ostrovsky wrote:
> On 07/25/2017 05:22 PM, Stefano Stabellini wrote:
> > Send PVCALLS_ACCEPT to the backend. Allocate a new active socket. Make
> > sure that only one accept command is executed at any given time by
> > setting PVCALLS_FLAG_ACCEPT_INFLIGHT and waiting on the
> > inflight_accept_req waitqueue.
> >
> > sock->sk->sk_send_head is not used for ip sockets: reuse the field to
> > store a pointer to the struct sock_mapping corresponding to the socket.
> >
> > Convert the new struct socket pointer into an uint64_t and use it as id
> > for the new socket to pass to the backend.
> >
> > Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
> > CC: boris.ostrovsky@oracle.com
> > CC: jgross@suse.com
> > ---
> > drivers/xen/pvcalls-front.c | 79 +++++++++++++++++++++++++++++++++++++++++++++
> > drivers/xen/pvcalls-front.h | 3 ++
> > 2 files changed, 82 insertions(+)
> >
> > diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
> > index 3b5d50e..b8c4538 100644
> > --- a/drivers/xen/pvcalls-front.c
> > +++ b/drivers/xen/pvcalls-front.c
> > @@ -413,6 +413,85 @@ int pvcalls_front_listen(struct socket *sock, int backlog)
> > return ret;
> > }
> >
> > +int pvcalls_front_accept(struct socket *sock, struct socket *newsock, int flags)
> > +{
> > + struct pvcalls_bedata *bedata;
> > + struct sock_mapping *map;
> > + struct sock_mapping *map2 = NULL;
> > + struct xen_pvcalls_request *req;
> > + int notify, req_id, ret, evtchn;
> > +
> > + if (!pvcalls_front_dev)
> > + return -ENOTCONN;
> > + bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
> > +
> > + map = (struct sock_mapping *) READ_ONCE(sock->sk->sk_send_head);
> > + if (!map)
> > + return -ENOTSOCK;
> > +
> > + if (map->passive.status != PVCALLS_STATUS_LISTEN)
> > + return -EINVAL;
> > +
> > + /*
> > + * Backend only supports 1 inflight accept request, will return
> > + * errors for the others
> > + */
> > + if (test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
> > + (void *)&map->passive.flags)) {
> > + if (wait_event_interruptible(map->passive.inflight_accept_req,
> > + !test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
> > + (void *)&map->passive.flags))
> > + != 0)
>
> Unnecessary "!=0".

OK


> > + return -EINTR;
> > + }
> > +
> > +
> > + newsock->sk = kzalloc(sizeof(*newsock->sk), GFP_KERNEL);
> > + if (newsock->sk == NULL)
> > + return -ENOMEM;
> > +
> > + spin_lock(&bedata->pvcallss_lock);
> > + req_id = bedata->ring.req_prod_pvt & (RING_SIZE(&bedata->ring) - 1);
> > + if (RING_FULL(&bedata->ring) ||
> > + READ_ONCE(bedata->rsp[req_id].req_id) != PVCALLS_INVALID_ID) {
> > + kfree(newsock->sk);
> > + spin_unlock(&bedata->pvcallss_lock);
> > + return -EAGAIN;
> > + }
> > +
> > + map2 = create_active(&evtchn);
> > +
> > + req = RING_GET_REQUEST(&bedata->ring, req_id);
> > + req->req_id = req_id;
> > + req->cmd = PVCALLS_ACCEPT;
> > + req->u.accept.id = (uint64_t) sock;
> > + req->u.accept.ref = map2->active.ref;
> > + req->u.accept.id_new = (uint64_t) newsock;
> > + req->u.accept.evtchn = evtchn;
> > +
> > + list_add_tail(&map2->list, &bedata->socket_mappings);
> > + WRITE_ONCE(newsock->sk->sk_send_head, (void *)map2);
> > + map2->sock = newsock;
> > +
> > + bedata->ring.req_prod_pvt++;
> > + RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
> > + spin_unlock(&bedata->pvcallss_lock);
> > + if (notify)
> > + notify_remote_via_irq(bedata->irq);
> > +
> > + wait_event(bedata->inflight_req,
> > + READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
> > +
> > + clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT, (void *)&map->passive.flags);
> > + wake_up(&map->passive.inflight_accept_req);
> > +
> > + ret = bedata->rsp[req_id].ret;
> > + /* read ret, then set this rsp slot to be reused */
> > + smp_mb();
> > + WRITE_ONCE(bedata->rsp[req_id].req_id, PVCALLS_INVALID_ID);
> > + return ret;
> > +}
> > +
> > static const struct xenbus_device_id pvcalls_front_ids[] = {
> > { "pvcalls" },
> > { "" }
> > diff --git a/drivers/xen/pvcalls-front.h b/drivers/xen/pvcalls-front.h
> > index aa8fe10..ab4f1da 100644
> > --- a/drivers/xen/pvcalls-front.h
> > +++ b/drivers/xen/pvcalls-front.h
> > @@ -10,5 +10,8 @@ int pvcalls_front_bind(struct socket *sock,
> > struct sockaddr *addr,
> > int addr_len);
> > int pvcalls_front_listen(struct socket *sock, int backlog);
> > +int pvcalls_front_accept(struct socket *sock,
> > + struct socket *newsock,
> > + int flags);
> >
> > #endif
>

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