linux-kernel - Re: [PATCH 3/3] dcache: account external names as indirectly reclaimable memory

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Message-Id: <20180405151123.df20d12168d8a38f7a6b02b5@linux-foundation.org>
Date:   Thu, 5 Apr 2018 15:11:23 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Al Viro <viro@...IV.linux.org.uk>
Cc:     Roman Gushchin <guro@...com>, linux-mm@...ck.org,
        Michal Hocko <mhocko@...e.com>,
        Johannes Weiner <hannes@...xchg.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com
Subject: Re: [PATCH 3/3] dcache: account external names as indirectly
 reclaimable memory

On Tue, 13 Mar 2018 00:45:32 +0000 Al Viro <viro@...IV.linux.org.uk> wrote:

> On Mon, Mar 12, 2018 at 10:36:38PM +0000, Roman Gushchin wrote:
> 
> > Ah, I see...
> > 
> > I think, it's better to account them when we're actually freeing,
> > otherwise we will have strange path:
> > (indirectly) reclaimable -> unreclaimable -> free
> > 
> > Do you agree?
> 
> > +static void __d_free_external_name(struct rcu_head *head)
> > +{
> > +	struct external_name *name;
> > +
> > +	name = container_of(head, struct external_name, u.head);
> > +
> > +	mod_node_page_state(page_pgdat(virt_to_page(name)),
> > +			    NR_INDIRECTLY_RECLAIMABLE_BYTES,
> > +			    -ksize(name));
> > +
> > +	kfree(name);
> > +}
> 
> Maybe, but then you want to call that from __d_free_external() and from
> failure path in __d_alloc() as well.  Duplicating something that convoluted
> and easy to get out of sync is just asking for trouble.

So.. where are we at with this issue?