[PATCH 12 of 12] This patch adds a lock ordering rule to avoid a potential deadlock when

Andrea Arcangeli
2008-04-22T13:51:28Z

# HG changeset patch
# User Andrea Arcangeli <andrea@qumranet.com>
# Date 1208872187 -7200
# Node ID e847039ee2e815088661933b7195584847dc7540
# Parent 128d705f38c8a774ac11559db445787ce6e91c77
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)