linux-kernel - Re: [PATCH 1/3] mm: change huge_ptep_clear

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Message-ID: <6c8a5b23-e470-63ca-cc82-f8b5ff1bafaf@linux.alibaba.com>
Date:   Fri, 6 May 2022 11:02:12 +0800
From:   Baolin Wang <baolin.wang@...ux.alibaba.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>, akpm@...ux-foundation.org,
        catalin.marinas@....com, will@...nel.org
Cc:     tsbogend@...ha.franken.de, James.Bottomley@...senPartnership.com,
        deller@....de, mpe@...erman.id.au, benh@...nel.crashing.org,
        paulus@...ba.org, hca@...ux.ibm.com, gor@...ux.ibm.com,
        agordeev@...ux.ibm.com, borntraeger@...ux.ibm.com,
        svens@...ux.ibm.com, ysato@...rs.sourceforge.jp, dalias@...c.org,
        davem@...emloft.net, arnd@...db.de,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-ia64@...r.kernel.org, linux-mips@...r.kernel.org,
        linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
        sparclinux@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH 1/3] mm: change huge_ptep_clear_flush() to return the
 original pte



On 5/6/2022 7:15 AM, Mike Kravetz wrote:
> On 4/29/22 01:14, Baolin Wang wrote:
>> It is incorrect to use ptep_clear_flush() to nuke a hugetlb page
>> table when unmapping or migrating a hugetlb page, and will change
>> to use huge_ptep_clear_flush() instead in the following patches.
>>
>> So this is a preparation patch, which changes the huge_ptep_clear_flush()
>> to return the original pte to help to nuke a hugetlb page table.
>>
>> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
>> ---
>>   arch/arm64/include/asm/hugetlb.h   |  4 ++--
>>   arch/arm64/mm/hugetlbpage.c        | 12 +++++-------
>>   arch/ia64/include/asm/hugetlb.h    |  4 ++--
>>   arch/mips/include/asm/hugetlb.h    |  9 ++++++---
>>   arch/parisc/include/asm/hugetlb.h  |  4 ++--
>>   arch/powerpc/include/asm/hugetlb.h |  9 ++++++---
>>   arch/s390/include/asm/hugetlb.h    |  6 +++---
>>   arch/sh/include/asm/hugetlb.h      |  4 ++--
>>   arch/sparc/include/asm/hugetlb.h   |  4 ++--
>>   include/asm-generic/hugetlb.h      |  4 ++--
>>   10 files changed, 32 insertions(+), 28 deletions(-)
> 
> The above changes look straight forward.
> Happy that you Cc'ed impacted arch maintainers so they can at least
> have a look.
> 
> The only user of huge_ptep_clear_flush() today is hugetlb_cow/wp() in
> mm/hugetlb.c.  Any reason why you did not change that code?  At least

Cause we did not use the return value of huge_ptep_clear_flush() in 
mm/hugetlb.c.

> cast the return of huge_ptep_clear_flush() to void with a comment?

Sure. Will add an explicit casting in next version.

> Not absolutely necessary.
> 
> Acked-by: Mike Kravetz <mike.kravetz@...cle.com>

Thanks.