jbd2: Remove t_handle_lock from start_this_handle()

This should remove the last exclusive lock from start_this_handle(),
so that we should now be able to start multiple transactions at the
same time on large SMP systems.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 15d5743..01743b5 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -629,7 +629,7 @@
 	/*
 	 * How many handles used this transaction? [t_handle_lock]
 	 */
-	int t_handle_count;
+	atomic_t		t_handle_count;
 
 	/*
 	 * This transaction is being forced and some process is