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    SubjectRe: [PATCH v2 07/13] xen/pvcalls: implement accept command
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    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".

    -boris

    > + 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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