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From:   Muchun Song <songmuchun@bytedance.com>
Date:   Thu, 10 Mar 2022 21:48:01 +0800
Message-ID: <CAMZfGtUNRAb3qnx5-ZV1uPEx1aLNbkzjJw5JrUzX8tMbR9AGNg@mail.gmail.com>
Subject: Re: [PATCH v4 2/6] dax: fix cache flush on PMD-mapped pages
To:     Dan Williams <dan.j.williams@intel.com>
Cc:     Matthew Wilcox <willy@infradead.org>, Jan Kara <jack@suse.cz>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Andrew Morton <akpm@linux-foundation.org>,
        Alistair Popple <apopple@nvidia.com>,
        Yang Shi <shy828301@gmail.com>,
        Ralph Campbell <rcampbell@nvidia.com>,
        Hugh Dickins <hughd@google.com>,
        Xiyu Yang <xiyuyang19@fudan.edu.cn>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Ross Zwisler <zwisler@kernel.org>,
        Christoph Hellwig <hch@infradead.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Linux NVDIMM <nvdimm@lists.linux.dev>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux MM <linux-mm@kvack.org>,
        Xiongchun duan <duanxiongchun@bytedance.com>,
        Muchun Song <smuchun@gmail.com>
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On Thu, Mar 10, 2022 at 8:06 AM Dan Williams <dan.j.williams@intel.com> wrote:
>
> On Wed, Mar 2, 2022 at 12:29 AM Muchun Song <songmuchun@bytedance.com> 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 needs to clarify that 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:

Right. I'll add this into the commit log.

>
> d92576f1167c dax: does not work correctly with virtual aliasing caches
>
> Otherwise, you can add:
>
> Reviewed-by: Dan Williams <dan.j.williams@intel.com>

Thanks.