linux-kernel - Re: [PATCH 1/2] mm: call flush_dcache_page in memcpy_to_page and memzero

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Date:   Wed, 14 Jul 2021 01:09:35 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 1/2] mm: call flush_dcache_page in memcpy_to_page and
 memzero_page

On Tue, Jul 13, 2021 at 07:52:30AM +0200, Christoph Hellwig wrote:
> memcpy_to_page and memzero_page can write to arbitrary pages, which could
> be in the page cache or in high memory, so  call flush_kernel_dcache_pages
> to flush the dcache.
> 
> Fixes: bb90d4bc7b6a ("mm/highmem: Lift memcpy_[to|from]_page to core")
> Fixes: 28961998f858 ("iov_iter: lift memzero_page() to highmem.h")
> Signed-off-by: Christoph Hellwig <hch@....de>

Reviewed-by: Ira Weiny <ira.weiny@...el.com>

> ---
>  include/linux/highmem.h | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/include/linux/highmem.h b/include/linux/highmem.h
> index 8c6e8e996c87..8e7e50a53a12 100644
> --- a/include/linux/highmem.h
> +++ b/include/linux/highmem.h
> @@ -318,6 +318,7 @@ static inline void memcpy_to_page(struct page *page, size_t offset,
>  
>  	VM_BUG_ON(offset + len > PAGE_SIZE);
>  	memcpy(to + offset, from, len);
> +	flush_dcache_page(page);
>  	kunmap_local(to);
>  }
>  
> @@ -325,6 +326,7 @@ static inline void memzero_page(struct page *page, size_t offset, size_t len)
>  {
>  	char *addr = kmap_atomic(page);
>  	memset(addr + offset, 0, len);
> +	flush_dcache_page(page);
>  	kunmap_atomic(addr);
>  }
>  
> -- 
> 2.30.2
>