From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with ESMTP id 3C4B15F0001 for ; Fri, 10 Apr 2009 12:09:38 -0400 (EDT) Date: Fri, 10 Apr 2009 09:01:18 -0700 (PDT) From: Linus Torvalds 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> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org 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 List-ID: 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org