Re: [Xen-devel] [PATCH v7 12/13] xen/pvcalls: implement release command

[Boris Ostrovsky]

On 10/26/2017 03:11 PM, Stefano Stabellini wrote:
> 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 
> CC: boris.ostrov...@oracle.com
> CC: jgr...@suse.com

Reviewed-by: Boris Ostrovsky 


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[Xen-devel] [PATCH v7 12/13] xen/pvcalls: implement release command

[Stefano Stabellini]

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 
CC: boris.ostrov...@oracle.com
CC: jgr...@suse.com
---
 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 eab70ce..8e7426083 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(>socket_lock);
+   if (!list_empty(>list))
+   list_del_init(>list);
+   spin_unlock(>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)
@@ -966,6 +981,89 @@ 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(_front_dev->dev);
+
+   map = (struct sock_mapping *) sock->sk->sk_send_head;
+   if (map == NULL) {
+   pvcalls_exit();
+   return 0;
+   }
+
+   spin_lock(>socket_lock);
+   ret = get_request(bedata, _id);
+   if (ret < 0) {
+   spin_unlock(>socket_lock);
+   pvcalls_exit();
+   return ret;
+   }
+   sock->sk->sk_send_head = NULL;
+
+   req = RING_GET_REQUEST(>ring, req_id);
+   req->req_id = req_id;
+   req->cmd = PVCALLS_RELEASE;
+   req->u.release.id = (uint64_t)map;
+
+   bedata->ring.req_prod_pvt++;
+   RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(>ring, notify);
+   spin_unlock(>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(>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(>active.in_mutex) ||
+  !mutex_trylock(>active.out_mutex))
+   cpu_relax();
+
+   pvcalls_front_free_map(bedata, map);
+   } else {
+   spin_lock(>socket_lock);
+   list_del(>list);
+   spin_unlock(>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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