linux-kernel - Re: [patch V2 00/18] mm/highmem: Preemptible variant of kmap

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Message-ID: <CAHk-=wiFxxGapdOyZHE-7LbFPk+jdfoqdeeJg0zWNQ86WvJGXg@mail.gmail.com>
Date:   Thu, 29 Oct 2020 16:11:12 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Paul McKenney <paulmck@...nel.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Ard Biesheuvel <ardb@...nel.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Christoph Hellwig <hch@....de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
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        Max Filippov <jcmvbkbc@...il.com>,
        linux-xtensa@...ux-xtensa.org
Subject: Re: [patch V2 00/18] mm/highmem: Preemptible variant of kmap_atomic & friends

On Thu, Oct 29, 2020 at 3:32 PM Thomas Gleixner <tglx@...utronix.de> wrote:
>
>
> Though I wanted to share the current state of affairs before investigating
> that further. If there is consensus in going forward with this, I'll have a
> deeper look into this issue.

Me likee. I think this looks like the right thing to do.

I didn't actually apply the patches, but just from reading them it
_looks_ to me like you do the migrate_disable() unconditionally, even
if it's not a highmem page..

That sounds like it might be a good thing for debugging, but not
necessarily great in general.

Or am I misreading things?

                Linus