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Date:   Tue, 22 Mar 2022 01:34:24 -0700
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,
        hch@infradead.org, linux-fsdevel@vger.kernel.org,
        nvdimm@lists.linux.dev, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, duanxiongchun@bytedance.com, smuchun@gmail.com
Subject: Re: [PATCH v5 2/6] dax: fix cache flush on PMD-mapped pages
Message-ID: <YjmKEEK3fz8a93iN@infradead.org>
References: <20220318074529.5261-1-songmuchun@bytedance.com>
 <20220318074529.5261-3-songmuchun@bytedance.com>
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On Fri, Mar 18, 2022 at 03:45:25PM +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.  This is just a
> documentation issue with the respect to properly documenting the expected
> usage of cache flushing before modifying the pmd.  However, in practice
> this is not a problem due to the fact that DAX is not available on
> architectures with virtually indexed caches per:
> 
>   commit d92576f1167c ("dax: does not work correctly with virtual aliasing caches")
> 
> Fixes: f729c8c9b24f ("dax: wrprotect pmd_t in dax_mapping_entry_mkclean")
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> Reviewed-by: Dan Williams <dan.j.williams@intel.com>

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>