Subject: mmap sems 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 Signed-off-by: Andrea Arcangeli 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)