Subject: mmap_sem lock ordering rule 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 --- mm/filemap.c | 3 +++ 1 file changed, 3 insertions(+) Index: linux-2.6/mm/filemap.c =================================================================== --- linux-2.6.orig/mm/filemap.c 2008-04-18 14:06:14.000000000 -0700 +++ linux-2.6/mm/filemap.c 2008-04-18 14:08:46.000000000 -0700 @@ -80,6 +80,9 @@ generic_file_direct_IO(int rw, struct ki * ->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) *