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Date:   Tue, 16 Oct 2018 15:27:48 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Mel Gorman <mgorman@techsingularity.net>
Cc:     Johannes Weiner <hannes@cmpxchg.org>,
        Rik van Riel <riel@redhat.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH 3/4] mm: workingset: add vmstat counter for shadow nodes
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        <20181016084923.GH5819@techsingularity.net>
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On Tue, 16 Oct 2018 09:49:23 +0100 Mel Gorman <mgorman@techsingularity.net> wrote:

> > Can we do this?
> > 
> > --- a/mm/workingset.c~mm-workingset-add-vmstat-counter-for-shadow-nodes-fix
> > +++ a/mm/workingset.c
> > @@ -377,6 +377,8 @@ void workingset_update_node(struct radix
> >  	 * already where they should be. The list_empty() test is safe
> >  	 * as node->private_list is protected by the i_pages lock.
> >  	 */
> > +	WARN_ON_ONCE(!irqs_disabled());	/* For __inc_lruvec_page_state */
> > +
> >  	if (node->count && node->count == node->exceptional) {
> >  		if (list_empty(&node->private_list)) {
> >  			list_lru_add(&shadow_nodes, &node->private_list);
> 
> Note that for whatever reason, I've observed that irqs_disabled() is
> actually quite an expensive call. I'm not saying the warning is a bad
> idea but it should not be sprinkled around unnecessary and may be more
> suitable as a debug option.

Yup, it is now VM_WARN_ON_ONCE().