From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753723AbbGPH1H (ORCPT ); Thu, 16 Jul 2015 03:27:07 -0400 Received: from cantor2.suse.de ([195.135.220.15]:43106 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751744AbbGPH1E (ORCPT ); Thu, 16 Jul 2015 03:27:04 -0400 Date: Thu, 16 Jul 2015 09:26:54 +0200 From: Jan Kara To: Oleg Nesterov Cc: Jan Kara , Dave Hansen , Al Viro , Linus Torvalds , Paul McKenney , Peter Zijlstra , Daniel Wagner , Davidlohr Bueso , Ingo Molnar , Tejun Heo , linux-kernel@vger.kernel.org Subject: Re: [PATCH RFC 0/4] change sb_writers to use percpu_rw_semaphore Message-ID: <20150716072654.GE22847@quack.suse.cz> References: <20150713212536.GA13855@redhat.com> <20150714104810.GB24369@quack.suse.cz> <20150714133731.GA24837@redhat.com> <55A57C50.1080406@linux.intel.com> <20150714212249.GA18441@redhat.com> <55A581F9.3090507@linux.intel.com> <20150715064705.GA22609@quack.suse.cz> <20150715181920.GA1797@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150715181920.GA1797@redhat.com> 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 On Wed 15-07-15 20:19:20, Oleg Nesterov wrote: > On 07/15, Jan Kara wrote: > > So I'm also in favor of Oleg's approach > > as well. We just have to wait until he fixes the outstanding issues with > > his code. > > Yes. I'll try to make the working version, hopefully this week. > > But, > > > Dave, just send your fsnotify patch separately to AKPM - he > > usually merges fsnotify stuff. > > Perhaps it makes to merge other 2 patches from Dave first? (those which > change __sb_start/end_write to rely on RCU). Afaics these changes are > straightforward and correct. Although I'd suggest to use preempt_disable() > and synchronize_sched() instead. I will be happy to (try to) make this > conversion on top of his changes. > > Because I do not want to delay the performance improvements and I do not > know when exactly I'll send the next version: I need to finish the previous > discussion about rcu_sync first. And the necessary changes in fs/super.c > depend on whether percpu_rw_semaphore will have rcu_sync or not (not too > much, only destroy_super() depends, but still). > > And of course, I am worried that I missed something and percpu_rw_semaphore > can't work for some reason. The code in fs/super.c looks simple, but it > seems that filesystems do the "strange" things with lockdep at least. So Dave's patches would go in only in the next merge window anyway so we still have like two-three weeks to decide which patchset to take. If you think it will take you longer, then merging Dave's patches makes some sense although I personally don't think the issue is so important that we have to fix it ASAP and eventual delay of one more release would be OK for me. Honza -- Jan Kara SUSE Labs, CR