linux-kernel - Re: [PATCH 2/5] dax: fix cache flush on PMD-mapped pages

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Message-ID: <Ye5WjF6xOV3WMcvh@infradead.org>
Date:   Sun, 23 Jan 2022 23:34:36 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     Muchun Song <songmuchun@...edance.com>
Cc:     dan.j.williams@...el.com, willy@...radead.org, jack@...e.cz,
        viro@...iv.linux.org.uk, akpm@...ux-foundation.org,
        apopple@...dia.com, shy828301@...il.com, rcampbell@...dia.com,
        hughd@...gle.com, xiyuyang19@...an.edu.cn,
        kirill.shutemov@...ux.intel.com, zwisler@...nel.org,
        linux-fsdevel@...r.kernel.org, nvdimm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 2/5] dax: fix cache flush on PMD-mapped pages

On Fri, Jan 21, 2022 at 03:55:12PM +0800, Muchun Song wrote:
> The flush_cache_page() only remove a PAGE_SIZE sized range from the cache.
> However, it does not cover the full pages in a THP except a head page.
> Replace it with flush_cache_range() to fix this issue.
> 
> Fixes: f729c8c9b24f ("dax: wrprotect pmd_t in dax_mapping_entry_mkclean")
> Signed-off-by: Muchun Song <songmuchun@...edance.com>
> ---
>  fs/dax.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/dax.c b/fs/dax.c
> index 88be1c02a151..2955ec65eb65 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -857,7 +857,7 @@ static void dax_entry_mkclean(struct address_space *mapping, pgoff_t index,
>  			if (!pmd_dirty(*pmdp) && !pmd_write(*pmdp))
>  				goto unlock_pmd;
>  
> -			flush_cache_page(vma, address, pfn);
> +			flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);

Same comment as for the previous one.