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

From: Catalin Marinas <[email-masked]>
Date: Thu, 12 May 2022 12:07:41 +0100

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 <[email-masked]>
> 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 <[email-masked]>
> ---
>  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;
 }

 static int __init hugetlbpage_init(void)

-- 
Catalin