libceph: fix mutex coverage for ceph_con_close

(cherry picked from commit 8c50c817566dfa4581f82373aac39f3e608a7dc8)

Hold the mutex while twiddling all of the state bits to avoid possible
races.  While we're here, make not of why we cannot close the socket
directly.

Signed-off-by: Sage Weil <sage@inktank.com>
Reviewed-by: Alex Elder <elder@inktank.com>
Reviewed-by: Yehuda Sadeh <yehuda@inktank.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index 96d9c99..7ccecf3 100644 (file)
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -503,6 +503,7 @@ static void reset_connection(struct ceph_connection *con)
  */
 void ceph_con_close(struct ceph_connection *con)
 {
+       mutex_lock(&con->mutex);
        dout("con_close %p peer %s\n", con,
             ceph_pr_addr(&con->peer_addr.in_addr));
        clear_bit(NEGOTIATING, &con->state);
@@ -515,11 +516,16 @@ void ceph_con_close(struct ceph_connection *con)
        clear_bit(KEEPALIVE_PENDING, &con->flags);
        clear_bit(WRITE_PENDING, &con->flags);
 
-       mutex_lock(&con->mutex);
        reset_connection(con);
        con->peer_global_seq = 0;
        cancel_delayed_work(&con->work);
        mutex_unlock(&con->mutex);
+
+       /*
+        * We cannot close the socket directly from here because the
+        * work threads use it without holding the mutex.  Instead, let
+        * con_work() do it.
+        */
        queue_con(con);
 }
 EXPORT_SYMBOL(ceph_con_close);