vfs: use helper for calling f_op->fsync()

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
diff --git a/ipc/shm.c b/ipc/shm.c
index 4329fe3..258aff2 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -452,7 +452,7 @@
 
 	if (!sfd->file->f_op->fsync)
 		return -EINVAL;
-	return sfd->file->f_op->fsync(sfd->file, start, end, datasync);
+	return call_fsync(sfd->file, start, end, datasync);
 }
 
 static long shm_fallocate(struct file *file, int mode, loff_t offset,