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Date:   Tue, 14 Jan 2020 17:19:30 -0800
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Qian Cai <cai@lca.pw>
Cc:     Michal Hocko <mhocko@kernel.org>,
        David Hildenbrand <david@redhat.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
        pmladek@suse.com, rostedt@goodmis.org, peterz@infradead.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH -next] mm/hotplug: silence a lockdep splat with printk()
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On Tue, 14 Jan 2020 20:02:31 -0500 Qian Cai <cai@lca.pw> wrote:

> 
> 
> >> @@ -8290,8 +8290,10 @@ bool has_unmovable_pages(struct zone *zo
> >> 	return false;
> >> unmovable:
> >> 	WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE);
> >> -	if (flags & REPORT_FAILURE)
> >> -		dump_page(pfn_to_page(pfn + iter), reason);
> >> +	if (flags & REPORT_FAILURE) {
> >> +		page = pfn_to_page(pfn + iter);
> > 
> > This statement appears to be unnecessary.
> 
> dump_page() in set_migratetype_isolate() needs that “page”.

local var `page' is never used after this statement.