From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752552AbbJXPFw (ORCPT ); Sat, 24 Oct 2015 11:05:52 -0400 Received: from mx2.suse.de ([195.135.220.15]:33062 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751911AbbJXPFu (ORCPT ); Sat, 24 Oct 2015 11:05:50 -0400 Date: Sat, 24 Oct 2015 17:05:46 +0200 From: Jan Kara To: Jeff Layton Cc: Eric Paris , Jan Kara , Andrew Morton , linux-fsdevel@vget.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH RFC] fsnotify: destroy marks with call_srcu instead of dedicated thread Message-ID: <20151024150546.GB14231@quack.suse.cz> References: <1445627219-30565-1-git-send-email-jeff.layton@primarydata.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1445627219-30565-1-git-send-email-jeff.layton@primarydata.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 Fri 23-10-15 15:06:59, Jeff Layton wrote: > At the time that this code was originally written, call_srcu didn't > exist, so this thread was required to ensure that we waited for that > SRCU grace period to settle before finally freeing the object. > > It does exist now however and we can much more efficiently use call_srcu > to handle this. That also allows us to potentially use srcu_barrier > to ensure that they are all of the callbacks have run before proceeding. > In order to conserve space, we union the rcu_head with the g_list. > > This will be necessary for nfsd which will allocate marks from a > dedicated slabcache. We have to be able to ensure that all of the > objects are destroyed before destroying the cache. That's fairly > difficult to ensure with dedicated thread doing the destruction. The patch looks good. Just one nit below: > diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h > index 533c4408529a..6b7e89f45aa4 100644 > --- a/include/linux/fsnotify_backend.h > +++ b/include/linux/fsnotify_backend.h > @@ -220,7 +220,10 @@ struct fsnotify_mark { > /* List of marks by group->i_fsnotify_marks. Also reused for queueing > * mark into destroy_list when it's waiting for the end of SRCU period > * before it can be freed. [group->mark_mutex] */ Please update this comment to not speak about destroy_list. After that feel free to add: Reviewed-by: Jan Kara Honza > - struct list_head g_list; > + union { > + struct list_head g_list; > + struct rcu_head g_rcu; > + }; > /* Protects inode / mnt pointers, flags, masks */ > spinlock_t lock; > /* List of marks for inode / vfsmount [obj_lock] */ Honza -- Jan Kara SUSE Labs, CR