From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:51128 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750928AbdFSNM4 (ORCPT ); Mon, 19 Jun 2017 09:12:56 -0400 Date: Mon, 19 Jun 2017 15:12:53 +0200 From: Jan Kara Subject: Re: [PATCH 01/35] fscache: Remove unused ->now_uncached callback Message-ID: <20170619131253.GA22128@quack2.suse.cz> References: <20170601093245.29238-2-jack@suse.cz> <20170601093245.29238-1-jack@suse.cz> <10376.1496312768@warthog.procyon.org.uk> <20170601113434.GC23077@quack2.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170601113434.GC23077@quack2.suse.cz> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: David Howells Cc: Jan Kara , linux-mm@kvack.org, Hugh Dickins , linux-afs@lists.infradead.org, Ryusuke Konishi , linux-nilfs@vger.kernel.org, Bob Peterson , cluster-devel@redhat.com, Jaegeuk Kim , linux-f2fs-devel@lists.sourceforge.net, tytso@mit.edu, linux-ext4@vger.kernel.org, Ilya Dryomov , "Yan, Zheng" , ceph-devel@vger.kernel.org, linux-btrfs@vger.kernel.org, David Sterba , "Darrick J . Wong" , linux-xfs@vger.kernel.org, Nadia Yvette Chambers On Thu 01-06-17 13:34:34, Jan Kara wrote: > On Thu 01-06-17 11:26:08, David Howells wrote: > > Jan Kara wrote: > > > > > The callback doesn't ever get called. Remove it. > > > > Hmmm... I should perhaps be calling this. I'm not sure why I never did. > > > > At the moment, it doesn't strictly matter as ops on pages marked with > > PG_fscache get ignored if the cache has suffered an I/O error or has been > > withdrawn - but it will incur a performance penalty (the PG_fscache flag is > > checked in the netfs before calling into fscache). > > > > The downside of calling this is that when a cache is removed, fscache would go > > through all the cookies for that cache and iterate over all the pages > > associated with those cookies - which could cause a performance dip in the > > system. > > So I know nothing about fscache. If you decide these functions should stay > in as you are going to use them soon, then I can just convert them to the > new API as everything else. What just caught my eye and why I had a more > detailed look is that I didn't understand that 'PAGEVEC_SIZE - > pagevec_count(&pvec)' as a pagevec_lookup() argument since pagevec_count() > should always return 0 at that point? David, what is your final decision regarding this? Do you want to keep these unused functions (and I will just update my patch to convert them to the new calling convention) or will you apply the patch to remove them? Honza -- Jan Kara SUSE Labs, CR