linux-kernel - Re: linux-next: build failure after merge of the mm tree

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Date:   Thu, 12 May 2022 19:13:18 +0800
From:   Baolin Wang <baolin.wang@...ux.alibaba.com>
To:     Catalin Marinas <catalin.marinas@....com>,
        Stephen Rothwell <sfr@...b.auug.org.au>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Will Deacon <will@...nel.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Next Mailing List <linux-next@...r.kernel.org>
Subject: Re: linux-next: build failure after merge of the mm tree



On 5/12/2022 7:07 PM, Catalin Marinas wrote:
> On Thu, May 12, 2022 at 07:38:55PM +1000, Stephen Rothwell wrote:
>> After merging the mm tree, today's linux-next build (arm64 defconfig)
>> failed like this:
>>
>> arch/arm64/mm/hugetlbpage.c: In function 'huge_ptep_clear_flush':
>> arch/arm64/mm/hugetlbpage.c:493:16: error: implicit declaration of function 'get_clear_flush'; did you mean 'ptep_clear_flush'? [-Werror=implicit-function-declaration]
>>    493 |         return get_clear_flush(vma->vm_mm, addr, ptep, pgsize, ncontig);
>>        |                ^~~~~~~~~~~~~~~
>>        |                ptep_clear_flush
>> arch/arm64/mm/hugetlbpage.c:493:16: error: incompatible types when returning type 'int' but 'pte_t' was expected
>>    493 |         return get_clear_flush(vma->vm_mm, addr, ptep, pgsize, ncontig);
>>        |                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> arch/arm64/mm/hugetlbpage.c:494:1: error: control reaches end of non-void function [-Werror=return-type]
>>    494 | }
>>        | ^
>>
>> Caused by commit
>>
>>    00df1f1a133b ("mm: change huge_ptep_clear_flush() to return the original pte")
>>
>> interacting with commit
>>
>>    fb396bb459c1 ("arm64/hugetlb: Drop TLB flush from get_clear_flush()")
>>
>> I have applied the following merg fix patch for today.
>>
>> From: Stephen Rothwell <sfr@...b.auug.org.au>
>> Date: Thu, 12 May 2022 19:33:11 +1000
>> Subject: [PATCH] fixup for "mm: change huge_ptep_clear_flush() to return the original pte"
>>
>> It interacts with commit
>>
>>    fb396bb459c1 ("arm64/hugetlb: Drop TLB flush from get_clear_flush()")
>>
>> from the arm64 tree
>>
>> Signed-off-by: Stephen Rothwell <sfr@...b.auug.org.au>
>> ---
>>   arch/arm64/mm/hugetlbpage.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
>> index 5bdf913dedc7..30f5b76aabe9 100644
>> --- a/arch/arm64/mm/hugetlbpage.c
>> +++ b/arch/arm64/mm/hugetlbpage.c
>> @@ -490,7 +490,7 @@ pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,
>>   		return ptep_clear_flush(vma, addr, ptep);
>>   
>>   	ncontig = find_num_contig(vma->vm_mm, addr, ptep, &pgsize);
>> -	return get_clear_flush(vma->vm_mm, addr, ptep, pgsize, ncontig);
>> +	return get_clear_contig(vma->vm_mm, addr, ptep, pgsize, ncontig);
>>   }
> 
> Note that after the arm64 commit, get_clear_contig() no longer flushes
> the TLB. So maybe something like:
> 
> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
> index 30f5b76aabe9..9a999550df8e 100644
> --- a/arch/arm64/mm/hugetlbpage.c
> +++ b/arch/arm64/mm/hugetlbpage.c
> @@ -485,12 +485,15 @@ pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,
>   {
>   	size_t pgsize;
>   	int ncontig;
> +	pte_t orig_pte;
> 
>   	if (!pte_cont(READ_ONCE(*ptep)))
>   		return ptep_clear_flush(vma, addr, ptep);
> 
>   	ncontig = find_num_contig(vma->vm_mm, addr, ptep, &pgsize);
> -	return get_clear_contig(vma->vm_mm, addr, ptep, pgsize, ncontig);
> +	orig_pte = get_clear_contig(vma->vm_mm, addr, ptep, pgsize, ncontig);
> +	flush_tlb_range(vma, addr, addr + pgsize * ncontig);
> +	return orig_pte;
>   }

Yes, after checking this fb396bb459c1 ("arm64/hugetlb: Drop TLB flush 
from get_clear_flush()"), I also realized it will miss TLB flush.

So I am not sure I need send a incremental patch to fix this issue? Or 
resend my patch set [1] with rebasing on the arm64 changes?

Catalin and Andrew, how do you think? Thanks.

[1] 
https://lore.kernel.org/all/cover.1652270205.git.baolin.wang@linux.alibaba.com/