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    Subject[PATCH 5.15 433/667] dax: fix cache flush on PMD-mapped pages
    Date
    From: Muchun Song <songmuchun@bytedance.com>

    [ Upstream commit e583b5c472bd23d450e06f148dc1f37be74f7666 ]

    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")

    Link: https://lkml.kernel.org/r/20220403053957.10770-3-songmuchun@bytedance.com
    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>
    Reviewed-by: Christoph Hellwig <hch@lst.de>
    Cc: Alistair Popple <apopple@nvidia.com>
    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Cc: Hugh Dickins <hughd@google.com>
    Cc: Jan Kara <jack@suse.cz>
    Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
    Cc: Matthew Wilcox <willy@infradead.org>
    Cc: Ralph Campbell <rcampbell@nvidia.com>
    Cc: Ross Zwisler <zwisler@kernel.org>
    Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
    Cc: Xiyu Yang <xiyuyang19@fudan.edu.cn>
    Cc: Yang Shi <shy828301@gmail.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    fs/dax.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    diff --git a/fs/dax.c b/fs/dax.c
    index 4e3e5a283a91..1d0658cf9dcf 100644
    --- a/fs/dax.c
    +++ b/fs/dax.c
    @@ -846,7 +846,8 @@ 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);
    pmd = pmdp_invalidate(vma, address, pmdp);
    pmd = pmd_wrprotect(pmd);
    pmd = pmd_mkclean(pmd);
    --
    2.35.1


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