linux-kernel - Re: [PATCH v3 30/34] mm: Use flush_icache_pages() in do_set

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Date:   Fri, 3 Mar 2023 16:02:01 +0200
From:   Mike Rapoport <rppt@...nel.org>
To:     "Matthew Wilcox (Oracle)" <willy@...radead.org>
Cc:     linux-mm@...ck.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 30/34] mm: Use flush_icache_pages() in do_set_pmd()

On Tue, Feb 28, 2023 at 09:37:33PM +0000, Matthew Wilcox (Oracle) wrote:
> Push the iteration over each page down to the architectures (many
> can flush the entire THP without iteration).
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> ---
>  mm/memory.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index bfa3100ec5a3..69e844d5f75c 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4222,8 +4222,7 @@ vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page)
>  	if (unlikely(!pmd_none(*vmf->pmd)))
>  		goto out;
>  
> -	for (i = 0; i < HPAGE_PMD_NR; i++)
> -		flush_icache_page(vma, page + i);
> +	flush_icache_pages(vma, page, HPAGE_PMD_NR);
>  
>  	entry = mk_huge_pmd(page, vma->vm_page_prot);
>  	if (write)
> -- 
> 2.39.1

I get this:

  CC      mm/memory.o
/home/mike/git/linux/mm/memory.c: In function 'do_set_pmd':
/home/mike/git/linux/mm/memory.c:4191:13: warning: unused variable 'i' [-Wunused-variable]
 4191 |         int i;
      |             ^

And the patch here makes it go away:

diff --git a/mm/memory.c b/mm/memory.c
index cc7845ff09ba..c359fb8643e5 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4188,7 +4188,6 @@ vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page)
 	bool write = vmf->flags & FAULT_FLAG_WRITE;
 	unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 	pmd_t entry;
-	int i;
 	vm_fault_t ret = VM_FAULT_FALLBACK;
 
 	if (!transhuge_vma_suitable(vma, haddr))

-- 
Sincerely yours,
Mike.