[Xen-devel] [PATCH v8 12/13] xen/pvcalls: implement release command

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

Send PVCALLS_RELEASE to the backend and wait for a reply. Take both
in_mutex and out_mutex to avoid concurrent accesses. Then, free the
socket.

For passive sockets, check whether we have already pre-allocated an
active socket for the purpose of being accepted. If so, free that as
well.

Signed-off-by: Stefano Stabellini <stefano@xxxxxxxxxxx>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
CC: boris.ostrovsky@xxxxxxxxxx
CC: jgross@xxxxxxxx
---
 drivers/xen/pvcalls-front.c | 98 +++++++++++++++++++++++++++++++++++++++++++++
 drivers/xen/pvcalls-front.h |  1 +
 2 files changed, 99 insertions(+)

diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index c7d4251..0c1ec68 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -199,6 +199,21 @@ static irqreturn_t pvcalls_front_event_handler(int irq, 
void *dev_id)
 static void pvcalls_front_free_map(struct pvcalls_bedata *bedata,
                                   struct sock_mapping *map)
 {
+       int i;
+
+       unbind_from_irqhandler(map->active.irq, map);
+
+       spin_lock(&bedata->socket_lock);
+       if (!list_empty(&map->list))
+               list_del_init(&map->list);
+       spin_unlock(&bedata->socket_lock);
+
+       for (i = 0; i < (1 << PVCALLS_RING_ORDER); i++)
+               gnttab_end_foreign_access(map->active.ring->ref[i], 0, 0);
+       gnttab_end_foreign_access(map->active.ref, 0, 0);
+       free_page((unsigned long)map->active.ring);
+
+       kfree(map);
 }
 
 static irqreturn_t pvcalls_front_conn_handler(int irq, void *sock_map)
@@ -972,6 +987,89 @@ unsigned int pvcalls_front_poll(struct file *file, struct 
socket *sock,
        return ret;
 }
 
+int pvcalls_front_release(struct socket *sock)
+{
+       struct pvcalls_bedata *bedata;
+       struct sock_mapping *map;
+       int req_id, notify, ret;
+       struct xen_pvcalls_request *req;
+
+       if (sock->sk == NULL)
+               return 0;
+
+       pvcalls_enter();
+       if (!pvcalls_front_dev) {
+               pvcalls_exit();
+               return -EIO;
+       }
+
+       bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
+
+       map = (struct sock_mapping *) sock->sk->sk_send_head;
+       if (map == NULL) {
+               pvcalls_exit();
+               return 0;
+       }
+
+       spin_lock(&bedata->socket_lock);
+       ret = get_request(bedata, &req_id);
+       if (ret < 0) {
+               spin_unlock(&bedata->socket_lock);
+               pvcalls_exit();
+               return ret;
+       }
+       sock->sk->sk_send_head = NULL;
+
+       req = RING_GET_REQUEST(&bedata->ring, req_id);
+       req->req_id = req_id;
+       req->cmd = PVCALLS_RELEASE;
+       req->u.release.id = (uintptr_t)map;
+
+       bedata->ring.req_prod_pvt++;
+       RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
+       spin_unlock(&bedata->socket_lock);
+       if (notify)
+               notify_remote_via_irq(bedata->irq);
+
+       wait_event(bedata->inflight_req,
+                  READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
+
+       if (map->active_socket) {
+               /*
+                * Set in_error and wake up inflight_conn_req to force
+                * recvmsg waiters to exit.
+                */
+               map->active.ring->in_error = -EBADF;
+               wake_up_interruptible(&map->active.inflight_conn_req);
+
+               /*
+                * Wait until there are no more waiters on the mutexes.
+                * We know that no new waiters can be added because sk_send_head
+                * is set to NULL -- we only need to wait for the existing
+                * waiters to return.
+                */
+               while (!mutex_trylock(&map->active.in_mutex) ||
+                          !mutex_trylock(&map->active.out_mutex))
+                       cpu_relax();
+
+               pvcalls_front_free_map(bedata, map);
+       } else {
+               spin_lock(&bedata->socket_lock);
+               list_del(&map->list);
+               spin_unlock(&bedata->socket_lock);
+               if (READ_ONCE(map->passive.inflight_req_id) !=
+                   PVCALLS_INVALID_ID) {
+                       pvcalls_front_free_map(bedata,
+                                              map->passive.accept_map);
+               }
+               kfree(map);
+       }
+       WRITE_ONCE(bedata->rsp[req_id].req_id, PVCALLS_INVALID_ID);
+
+       pvcalls_exit();
+       return 0;
+}
+
 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 25e05b8..3332978 100644
--- a/drivers/xen/pvcalls-front.h
+++ b/drivers/xen/pvcalls-front.h
@@ -23,5 +23,6 @@ int pvcalls_front_recvmsg(struct socket *sock,
 unsigned int pvcalls_front_poll(struct file *file,
                                struct socket *sock,
                                poll_table *wait);
+int pvcalls_front_release(struct socket *sock);
 
 #endif
-- 
1.9.1


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