xen/pvcalls: implement release command

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@aporeto.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
CC: boris.ostrovsky@oracle.com
CC: jgross@suse.com
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

2 files changed, 99 insertions, 0 deletions

diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index c7d4251c3678..0c1ec6894cc4 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -199,6 +199,21 @@ again:
 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 25e05b8f2d72..3332978f4fcd 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