NFS: Fix up two use-after-free issues with the new tracing code

We don't want to pass the context argument to trace_nfs_atomic_open_exit()
after it has been released.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/dir.c

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 4ce7f76..d8149e9 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1399,7 +1399,6 @@
 	nfs_file_set_open_context(file, ctx);
 
 out:
-	put_nfs_open_context(ctx);
 	return err;
 }
 
@@ -1460,9 +1459,9 @@
 	inode = NFS_PROTO(dir)->open_context(dir, ctx, open_flags, &attr);
 	nfs_unblock_sillyrename(dentry->d_parent);
 	if (IS_ERR(inode)) {
-		put_nfs_open_context(ctx);
 		err = PTR_ERR(inode);
 		trace_nfs_atomic_open_exit(dir, ctx, open_flags, err);
+		put_nfs_open_context(ctx);
 		switch (err) {
 		case -ENOENT:
 			d_drop(dentry);
@@ -1484,6 +1483,7 @@
 
 	err = nfs_finish_open(ctx, ctx->dentry, file, open_flags, opened);
 	trace_nfs_atomic_open_exit(dir, ctx, open_flags, err);
+	put_nfs_open_context(ctx);
 out:
 	return err;