linux-kernel - Re: [PATCH] mm/page-flags: Check enforce parameter in PF_ONLY

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Message-ID: <e84f6e20-ccf5-5779-2733-7b259dc2493a@arm.com>
Date:   Wed, 27 Mar 2019 19:29:57 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        hannes@...xchg.org, david@...hat.com, vbabka@...e.cz,
        willy@...radead.org, akpm@...ux-foundation.org,
        Nicholas Piggin <npiggin@...il.com>
Subject: Re: [PATCH] mm/page-flags: Check enforce parameter in PF_ONLY_HEAD()



On 03/27/2019 06:45 PM, Michal Hocko wrote:
> [Cc Nick]
> 
> On Wed 27-03-19 17:57:52, Anshuman Khandual wrote:
>> Just check for enforce parameter in PF_ONLY_HEAD() wrapper before calling
>> VM_BUG_ON_PGFLAGS() for tail pages.
> Why is this an actual fix? Only TESTPAGEFLAG doesn't enforce the check
> but I suspect that Nick just wanted the check to be _always_ performed
> as the name suggests. What kind of problem are you trying to solve?

Did not hit any problem directly. Just from code inspection it seemed that
the enforce check was missing as compared to other wrappers there. I felt
that the commit could have probably omitted the check by mistake.