Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753434Ab3IKAjS (ORCPT ); Tue, 10 Sep 2013 20:39:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39409 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751871Ab3IKAjQ (ORCPT ); Tue, 10 Sep 2013 20:39:16 -0400 Date: Wed, 11 Sep 2013 10:39:05 +1000 From: Dave Chinner To: Linus Torvalds Cc: Al Viro , Andrew Morton , Stephen Rothwell , linux-next , Linux Kernel Mailing List , Glauber Costa Subject: Re: linux-next: manual merge of the akpm tree with Linus' tree Message-ID: <20130911003905.GD2445@devil.localdomain> References: <20130910152753.662599171456233c5f91edb4@linux-foundation.org> <20130910222924.GB13318@ZenIV.linux.org.uk> <20130910153520.14e49cd32feb16d45eb8abac@linux-foundation.org> <20130910223624.GC13318@ZenIV.linux.org.uk> <20130910154116.cc4afe048213a779040ea3cc@linux-foundation.org> <20130910224823.GE13318@ZenIV.linux.org.uk> <20130910225934.GF13318@ZenIV.linux.org.uk> <20130910235349.GG13318@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1529 Lines: 36 On Tue, Sep 10, 2013 at 05:01:23PM -0700, Linus Torvalds wrote: > On Tue, Sep 10, 2013 at 4:53 PM, Al Viro wrote: > > > > list_lru_add() can fail if it's already on the list; leaving the counter > > alone should've been conditional on that, setting the flag - no. Said > > that, it probably should be WARN_ON(!...); this_cpu_inc(); ... |= ...; > > That WARN_ON_(!..) might indeed be better (maybe just WARN_ON_ONCE()).. > > That DCACHE_LRU_LIST bit needs to be coherent with "the dentry->d_lru > entry is on _some_ list" (whether it's the dentry one or the shrinker > one), so if that list_lru_add() ever fails, that would be a sign of > badness. > > And that whole function is very performance-critical, to the point > where we not only don't want to call down to list_lry_add(), we don't > even want to touch the d_lru list entry itself to even _look_ if it's > empty or not, because that will take a cache miss. Which was obviously > the whole reason for that DCACHE_LRU_LIST bit existing... Guys, I'm about to be out of the office for 4-5 days, so this is real bad timing for me. When I get back I'll put some effort into validating that everything still works properly and performs as expected. Cheers, Dave. -- Dave Chinner dchinner@redhat.com -- 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/