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Date:   Wed, 4 May 2022 07:09:37 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Minchan Kim <minchan@kernel.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>,
        Suren Baghdasaryan <surenb@google.com>,
        Michal Hocko <mhocko@suse.com>,
        John Dias <joaodias@google.com>,
        Tim Murray <timmurray@google.com>
Subject: Re: [PATCH] mm: don't be stuck to rmap lock on reclaim path
Message-ID: <YnIYofrw/GGEvc0U@casper.infradead.org>
References: <20220503170341.1413961-1-minchan@kernel.org>
 <YnHzvV2Uz2ynENnG@casper.infradead.org>
 <YnIBbjRYACzvuZpp@google.com>
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On Tue, May 03, 2022 at 09:30:38PM -0700, Minchan Kim wrote:
> On Wed, May 04, 2022 at 04:32:13AM +0100, Matthew Wilcox wrote:
> > On Tue, May 03, 2022 at 10:03:41AM -0700, Minchan Kim wrote:
> > > -void rmap_walk(struct folio *folio, const struct rmap_walk_control *rwc);
> > > -void rmap_walk_locked(struct folio *folio, const struct rmap_walk_control *rwc);
> > > +void rmap_walk(struct folio *folio, struct rmap_walk_control *rwc);
> > > +void rmap_walk_locked(struct folio *folio, struct rmap_walk_control *rwc);
> > 
> > I see the build bot already beat me to pointing out why this is wrong,
> > but do you not look at git log to figure out why code was changed to be
> > the way it is now, before you change it back?
> 
> This patch added a new field as out param like compact_control so
> the rmap_walk_control is not immutable.

... but we have a user which treats it as if it is.