[PATCH 9 of 9] This patch adds a lock ordering rule to avoid a potential deadlock when

[Andrea Arcangeli <andrea@qumranet.com>]

# HG changeset patch
# User Andrea Arcangeli <andrea@qumranet.com>
# Date 1207666972 -7200
# Node ID bd55023b22769ecb14b26c2347947f7d6d63bcea
# Parent  3b14e26a4e0491f00bb989be04d8b7e0755ed2d7
This patch adds a lock ordering rule to avoid a potential deadlock when
multiple mmap_sems need to be locked.

Signed-off-by: Dean Nelson <dcn@sgi.com>

diff --git a/mm/filemap.c b/mm/filemap.c
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -79,6 +79,9 @@
  *
  *  ->i_mutex			(generic_file_buffered_write)
  *    ->mmap_sem		(fault_in_pages_readable->do_page_fault)
+ *
+ *    When taking multiple mmap_sems, one should lock the lowest-addressed
+ *    one first proceeding on up to the highest-addressed one.
  *
  *  ->i_mutex
  *    ->i_alloc_sem             (various)