[Xen-devel] [PATCH v1 11/13] 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.

Signed-off-by: Stefano Stabellini <stefano@xxxxxxxxxxx>
CC: boris.ostrovsky@xxxxxxxxxx
CC: jgross@xxxxxxxx
---
 drivers/xen/pvcalls-front.c | 86 +++++++++++++++++++++++++++++++++++++++++++++
 drivers/xen/pvcalls-front.h |  1 +
 2 files changed, 87 insertions(+)

diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index b6cfb7d..bd3dfac 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -174,6 +174,24 @@ static irqreturn_t pvcalls_front_conn_handler(int irq, 
void *sock_map)
        return IRQ_HANDLED;
 }
 
+static void pvcalls_front_free_map(struct pvcalls_bedata *bedata,
+                                  struct sock_mapping *map)
+{
+       int i;
+
+       spin_lock(&bedata->pvcallss_lock);
+       if (!list_empty(&map->list))
+               list_del_init(&map->list);
+       spin_unlock(&bedata->pvcallss_lock);
+
+       /* what if the thread waiting still need access? */
+       for (i = 0; i < (1 << map->active.ring->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);
+       unbind_from_irqhandler(map->active.irq, map);
+}
+
 int pvcalls_front_socket(struct socket *sock)
 {
        struct pvcalls_bedata *bedata;
@@ -805,6 +823,74 @@ unsigned int pvcalls_front_poll(struct file *file, struct 
socket *sock,
                return pvcalls_front_poll_passive(file, bedata, map, wait);
 }
 
+int pvcalls_front_release(struct socket *sock)
+{
+       struct pvcalls_bedata *bedata;
+       struct sock_mapping *map;
+       int req_id, notify;
+       struct xen_pvcalls_request *req;
+
+       if (!pvcalls_front_dev)
+               return -EIO;
+       bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
+       if (!bedata)
+               return -EIO;
+
+       if (sock->sk == NULL)
+               return 0;
+
+       map = (struct sock_mapping *) READ_ONCE(sock->sk->sk_send_head);
+       if (map == NULL)
+               return 0;
+       WRITE_ONCE(sock->sk->sk_send_head, NULL);
+
+       spin_lock(&bedata->pvcallss_lock);
+       req_id = bedata->ring.req_prod_pvt & (RING_SIZE(&bedata->ring) - 1);
+       BUG_ON(req_id >= PVCALLS_NR_REQ_PER_RING);
+       if (RING_FULL(&bedata->ring) ||
+           READ_ONCE(bedata->rsp[req_id].req_id) != PVCALLS_INVALID_ID) {
+               spin_unlock(&bedata->pvcallss_lock);
+               return -EAGAIN;
+       }
+       req = RING_GET_REQUEST(&bedata->ring, req_id);
+       req->req_id = req_id;
+       req->cmd = PVCALLS_RELEASE;
+       req->u.release.id = (uint64_t)sock;
+
+       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);
+
+       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);
+
+               mutex_lock(&map->active.in_mutex);
+               mutex_lock(&map->active.out_mutex);
+               pvcalls_front_free_map(bedata, map);
+               mutex_unlock(&map->active.out_mutex);
+               mutex_unlock(&map->active.in_mutex);
+               kfree(map);
+       } else {
+               spin_lock(&bedata->pvcallss_lock);
+               list_del_init(&map->list);
+               kfree(map);
+               spin_unlock(&bedata->pvcallss_lock);
+       }
+       WRITE_ONCE(bedata->rsp[req_id].req_id, PVCALLS_INVALID_ID);
+
+       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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