linux-kernel - Re: [PATCH v2 00/10] change the implementation of the PageHighMem()

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Message-ID: <20200501123429.GA26861@infradead.org>
Date:   Fri, 1 May 2020 05:34:29 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Joonsoo Kim <js1304@...il.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Laura Abbott <labbott@...hat.com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Michal Hocko <mhocko@...e.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Roman Gushchin <guro@...com>, Minchan Kim <minchan@...nel.org>,
        Rik van Riel <riel@...riel.com>,
        Christian Koenig <christian.koenig@....com>,
        Huang Rui <ray.huang@....com>,
        Eric Biederman <ebiederm@...ssion.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Pavel Machek <pavel@....cz>, kernel-team@....com,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH v2 00/10] change the implementation of the PageHighMem()

On Fri, May 01, 2020 at 09:15:30PM +0900, Joonsoo Kim wrote:
> I think that PageHighMemZone() is long and complicated enough to have
> a macro.

It is.  But then again it also shouldn't really be used by anything
but MM internals.

> 
> PageHighMemZone(page) = is_highmem_idx(zone_idx(page_zone(page))
> 
> Instead of open-code, how about changing the style of macro like as
> page_from_highmem()? What PageHighMemZone() represent is derivated
> attribute from the page so PageXXX() style may not be appropriate.

Maybe page_is_highmem_zone() with a big kerneldoc comment explaining
the use case?  Bonus points of killing enough users that it can be
in mm/internal.h.