[Xen-devel] [PATCH v2 07/13] xen/pvcalls: implement accept command

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

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@xxxxxxxxxxx>
CC: boris.ostrovsky@xxxxxxxxxx
CC: jgross@xxxxxxxx
---
 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)
+                       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
-- 
1.9.1


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