Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761959AbZDJQKS (ORCPT ); Fri, 10 Apr 2009 12:10:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759385AbZDJQKA (ORCPT ); Fri, 10 Apr 2009 12:10:00 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:45529 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758122AbZDJQKA (ORCPT ); Fri, 10 Apr 2009 12:10:00 -0400 Date: Fri, 10 Apr 2009 09:01:18 -0700 (PDT) From: Linus Torvalds X-X-Sender: torvalds@localhost.localdomain To: Wu Fengguang cc: Andrew Morton , Ying Han , "linux-mm@kvack.org" , linux-kernel , Ingo Molnar , Mike Waychison , Rohit Seth , Hugh Dickins , Peter Zijlstra , "H. Peter Anvin" , =?ISO-8859-15?Q?T=F6r=F6k_Edwin?= , Lee Schermerhorn , Nick Piggin Subject: Re: [PATCH][1/2]page_fault retry with NOPAGE_RETRY In-Reply-To: <20090410073042.GB21149@localhost> Message-ID: References: <604427e00904081302m7b29c538u7781cd8f4dd576f2@mail.gmail.com> <20090409230205.310c68a7.akpm@linux-foundation.org> <20090410073042.GB21149@localhost> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1671 Lines: 51 On Fri, 10 Apr 2009, Wu Fengguang wrote: > On Fri, Apr 10, 2009 at 02:02:05PM +0800, Andrew Morton wrote: > > > Can we please redo this as: > > > > > > int write; > > unsigned int flags; > > > > /* > > * Big fat comment explaining the next three lines goes here > > */ > > Basically it's doing a > (is_write_access | FAULT_FLAG_RETRY) => > (FAULT_FLAG_WRITE | FAULT_FLAG_RETRY) > by extracting the bool part: > > write = write_access & ~FAULT_FLAG_RETRY; > convert bool to a bit flag: > > unsigned int flags = (write ? FAULT_FLAG_WRITE : 0); The point is, we shouldn't do that. Your code is confused, because it uses "write_access" as if it had the old behaviour (boolean to say "write") _plus_ the new behavior (bitmask to say "retry"), and that's just wrong. Just get rid of "write_access" entirely, and switch it over to something that is a pure bitmask. Yes, it means a couple of new preliminary patches that switch all callers of handle_mm_fault() over to using the VM_FLAGS, but that's not a big deal. I'm following up this email with two _example_ patches. They are untested, but they look sane. I'd like the series to _start_ with these, and then you can pass FAULT_FLAGS_WRITE | FAULT_FLAGS_RETRY down to handle_mm_fault() cleanly. Hmm? Note the _untested_ part on the patches to follow. It was done very mechanically, and the patches look sane, but .. !!! Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/