Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S939210AbZDJR5b (ORCPT ); Fri, 10 Apr 2009 13:57:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1764624AbZDJR5U (ORCPT ); Fri, 10 Apr 2009 13:57:20 -0400 Received: from smtp-out.google.com ([216.239.45.13]:26286 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758441AbZDJR5S (ORCPT ); Fri, 10 Apr 2009 13:57:18 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=mime-version:in-reply-to:references:date:message-id:subject:from:to: cc:content-type:content-transfer-encoding:x-system-of-record; b=QTVjwyg2rMOUbDJ+5GZsIRJdKNd9d/YIMfkSbQFaq1pNXkoZhdntBOPnLTpcwoWSl 8SIqnbluRdWP1wZCpetFg== MIME-Version: 1.0 In-Reply-To: References: <604427e00904081302m7b29c538u7781cd8f4dd576f2@mail.gmail.com> <20090409230205.310c68a7.akpm@linux-foundation.org> <20090410073042.GB21149@localhost> Date: Fri, 10 Apr 2009 10:57:12 -0700 Message-ID: <604427e00904101057o78868d84y58e3531ac8334505@mail.gmail.com> Subject: Re: [PATCH][1/2]page_fault retry with NOPAGE_RETRY From: Ying Han To: Linus Torvalds Cc: Wu Fengguang , Andrew Morton , "linux-mm@kvack.org" , linux-kernel , Ingo Molnar , Mike Waychison , Rohit Seth , Hugh Dickins , Peter Zijlstra , "H. Peter Anvin" , =?ISO-8859-1?Q?T=F6r=F6k_Edwin?= , Lee Schermerhorn , Nick Piggin Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2231 Lines: 66 2009/4/10 Linus Torvalds : > > > 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); Fengguang: thank you for your comments. i agree this is confusing... > > 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 .. !!! Thanks Linus for your comments. I will take Peter Zijlstra's patches (the _untested_ part) which basically replaces the write_access as a flag as you mentioned and start from there. My next step is to cleanup the patch with comments in the thread so far and post the new version. Anything else i missed, please let me know. thanks --Ying > > 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/