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Date:   Sun, 23 Jan 2022 23:34:36 -0800
From:   Christoph Hellwig <hch@infradead.org>
To:     Muchun Song <songmuchun@bytedance.com>
Cc:     dan.j.williams@intel.com, willy@infradead.org, jack@suse.cz,
        viro@zeniv.linux.org.uk, akpm@linux-foundation.org,
        apopple@nvidia.com, shy828301@gmail.com, rcampbell@nvidia.com,
        hughd@google.com, xiyuyang19@fudan.edu.cn,
        kirill.shutemov@linux.intel.com, zwisler@kernel.org,
        linux-fsdevel@vger.kernel.org, nvdimm@lists.linux.dev,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 2/5] dax: fix cache flush on PMD-mapped pages
Message-ID: <Ye5WjF6xOV3WMcvh@infradead.org>
References: <20220121075515.79311-1-songmuchun@bytedance.com>
 <20220121075515.79311-2-songmuchun@bytedance.com>
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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@bytedance.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.