linux-kernel - [PATCH 5.15 433/667] dax: fix cache flush on PMD-mapped pages

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Date:   Tue,  7 Jun 2022 19:01:38 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Muchun Song <songmuchun@...edance.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Christoph Hellwig <hch@....de>,
        Alistair Popple <apopple@...dia.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Hugh Dickins <hughd@...gle.com>, Jan Kara <jack@...e.cz>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Matthew Wilcox <willy@...radead.org>,
        Ralph Campbell <rcampbell@...dia.com>,
        Ross Zwisler <zwisler@...nel.org>,
        Xiongchun Duan <duanxiongchun@...edance.com>,
        Xiyu Yang <xiyuyang19@...an.edu.cn>,
        Yang Shi <shy828301@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 433/667] dax: fix cache flush on PMD-mapped pages

From: Muchun Song <songmuchun@...edance.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@...edance.com>
Reviewed-by: Dan Williams <dan.j.williams@...el.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Cc: Alistair Popple <apopple@...dia.com>
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: Jan Kara <jack@...e.cz>
Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: Ralph Campbell <rcampbell@...dia.com>
Cc: Ross Zwisler <zwisler@...nel.org>
Cc: Xiongchun Duan <duanxiongchun@...edance.com>
Cc: Xiyu Yang <xiyuyang19@...an.edu.cn>
Cc: Yang Shi <shy828301@...il.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.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