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Message-ID: <20170619131253.GA22128@quack2.suse.cz> Date: Mon, 19 Jun 2017 15:12:53 +0200 From: Jan Kara <jack@...e.cz> To: David Howells <dhowells@...hat.com> Cc: Jan Kara <jack@...e.cz>, linux-mm@...ck.org, Hugh Dickins <hughd@...gle.com>, linux-afs@...ts.infradead.org, Ryusuke Konishi <konishi.ryusuke@....ntt.co.jp>, linux-nilfs@...r.kernel.org, Bob Peterson <rpeterso@...hat.com>, cluster-devel@...hat.com, Jaegeuk Kim <jaegeuk@...nel.org>, linux-f2fs-devel@...ts.sourceforge.net, tytso@....edu, linux-ext4@...r.kernel.org, Ilya Dryomov <idryomov@...il.com>, "Yan, Zheng" <zyan@...hat.com>, ceph-devel@...r.kernel.org, linux-btrfs@...r.kernel.org, David Sterba <dsterba@...e.com>, "Darrick J . Wong" <darrick.wong@...cle.com>, linux-xfs@...r.kernel.org, Nadia Yvette Chambers <nyc@...omorphy.com> Subject: Re: [PATCH 01/35] fscache: Remove unused ->now_uncached callback On Thu 01-06-17 13:34:34, Jan Kara wrote: > On Thu 01-06-17 11:26:08, David Howells wrote: > > Jan Kara <jack@...e.cz> 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 withdrawn - but it will incur a performance penalty (the PG_fscache flag is 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 <jack@...e.com> SUSE Labs, CR
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