linux-kernel - Re: [PATCH -next v2] mm/hotplug: silence a lockdep splat with printk()

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Message-ID: <20200115144629.GG19428@dhcp22.suse.cz>
Date:   Wed, 15 Jan 2020 15:46:29 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Qian Cai <cai@....pw>
Cc:     akpm@...ux-foundation.org, sergey.senozhatsky.work@...il.com,
        pmladek@...e.com, rostedt@...dmis.org, peterz@...radead.org,
        david@...hat.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Mike Kravetz <mike.kravetz@...cle.com>
Subject: Re: [PATCH -next v2] mm/hotplug: silence a lockdep splat with
 printk()

On Wed 15-01-20 07:35:45, Qian Cai wrote:
> 
> 
> > On Jan 15, 2020, at 4:22 AM, Michal Hocko <mhocko@...nel.org> wrote:
> > 
> > Is this correct? CMA pages cannot be comound?
> 
> I never saw a CMA page also a compound page. Also, in
> alloc_contig_range(), it calls migrate_pages()—>
> unmap_and_move_huge_page() which will free the old huge page, so I
> think that will clear pageCompound.

This sounds like the implementation detail. I do not think you want to
depend on that. Anyway, see my other response. If you rebase on top of
Vlastimil's patch you do not really have to care.
-- 
Michal Hocko
SUSE Labs