nfs: do not start the callback thread until we set rqstp->rq_task

This fixes an Oopsable race when starting up the callback server.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Reviewed-by: Jeff Layton <jlayton@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/nfs/callback.c b/fs/nfs/callback.c
index e3dd1cd175d9..b8fb3a4ef649 100644
--- a/fs/nfs/callback.c
+++ b/fs/nfs/callback.c
@@ -235,7 +235,7 @@ static int nfs_callback_start_svc(int minorversion, struct rpc_xprt *xprt,
 
         cb_info->serv = serv;
         cb_info->rqst = rqstp;
-        cb_info->task = kthread_run(callback_svc, cb_info->rqst,
+        cb_info->task = kthread_create(callback_svc, cb_info->rqst,
                                     "nfsv4.%u-svc", minorversion);
         if (IS_ERR(cb_info->task)) {
                 ret = PTR_ERR(cb_info->task);
@@ -245,6 +245,7 @@ static int nfs_callback_start_svc(int minorversion, struct rpc_xprt *xprt,
                 return ret;
         }
         rqstp->rq_task = cb_info->task;
+        wake_up_process(cb_info->task);
         dprintk("nfs_callback_up: service started\n");
         return 0;
 }