From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nick Piggin Subject: [patch 05/44] mm: debug write deadlocks Date: Tue, 24 Apr 2007 11:23:51 +1000 Message-ID: <20070424013432.655279000@suse.de> References: <20070424012346.696840000@suse.de> Cc: Linux Filesystems , Mark Fasheh , Linux Memory Management To: Andrew Morton Return-path: Received: from ns1.suse.de ([195.135.220.2]:60271 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753255AbXDXFUv (ORCPT ); Tue, 24 Apr 2007 01:20:51 -0400 Content-Disposition: inline; filename=mm-debug-write-deadlocks.patch Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Allow CONFIG_DEBUG_VM to switch off the prefaulting logic, to simulate the difficult race where the page may be unmapped before calling copy_from_user. Makes the race much easier to hit. This is useful for demonstration and testing purposes, but is removed in a subsequent patch. Cc: Linux Memory Management Cc: Linux Filesystems Signed-off-by: Nick Piggin mm/filemap.c | 2 ++ 1 file changed, 2 insertions(+) Index: linux-2.6/mm/filemap.c =================================================================== --- linux-2.6.orig/mm/filemap.c +++ linux-2.6/mm/filemap.c @@ -1984,6 +1984,7 @@ generic_file_buffered_write(struct kiocb if (maxlen > bytes) maxlen = bytes; +#ifndef CONFIG_DEBUG_VM /* * Bring in the user page that we will copy from _first_. * Otherwise there's a nasty deadlock on copying from the @@ -1991,6 +1992,7 @@ generic_file_buffered_write(struct kiocb * up-to-date. */ fault_in_pages_readable(buf, maxlen); +#endif page = __grab_cache_page(mapping,index,&cached_page,&lru_pvec); if (!page) { --