linux-kernel - Re: [PATCH v10 4/8] highmem: do range clearing in clear_user

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Message-ID: <87ldizy2xp.fsf@oracle.com>
Date: Thu, 18 Dec 2025 12:01:38 -0800
From: Ankur Arora <ankur.a.arora@...cle.com>
To: "David Hildenbrand (Red Hat)" <david@...nel.org>
Cc: Ankur Arora <ankur.a.arora@...cle.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, x86@...nel.org, akpm@...ux-foundation.org,
        bp@...en8.de, dave.hansen@...ux.intel.com, hpa@...or.com,
        mingo@...hat.com, mjguzik@...il.com, luto@...nel.org,
        peterz@...radead.org, tglx@...utronix.de, willy@...radead.org,
        raghavendra.kt@....com, chleroy@...nel.org, ioworker0@...il.com,
        boris.ostrovsky@...cle.com, konrad.wilk@...cle.com
Subject: Re: [PATCH v10 4/8] highmem: do range clearing in
 clear_user_highpages()


David Hildenbrand (Red Hat) <david@...nel.org> writes:

> On 12/15/25 21:49, Ankur Arora wrote:
>> Use the range clearing primitive clear_user_pages() when clearing
>> contiguous pages in clear_user_highpages().
>> We can safely do that when we have !CONFIG_HIGHMEM and when the
>> architecture does not have clear_user_highpage.
>> The first is necessary because not doing intermediate maps for
>> pages lets contiguous page ranges stay contiguous. The second,
>> because if the architecture has clear_user_highpage(), it likely
>> needs flushing magic when clearing the page, magic that we aren't
>> privy to.
>> Signed-off-by: Ankur Arora <ankur.a.arora@...cle.com>
>> ---
>
> Can't you squash #4 into #2 if you move #3 in front of them? Or is there a
> dependency with #2 that I am missing?

I thought it would be clearer to split this into #2 and #4 but #2
is completely obvious so doesn't help much.

Will squash.

--
ankur