linux-kernel - [PATCH 5.10 08/10] mm: fix missing cache flush for all tail pages of compound page

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Date:   Fri, 13 May 2022 16:23:52 +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>,
        Zi Yan <ziy@...dia.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        Fam Zheng <fam.zheng@...edance.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Lars Persson <lars.persson@...s.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Peter Xu <peterx@...hat.com>,
        Xiongchun Duan <duanxiongchun@...edance.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 5.10 08/10] mm: fix missing cache flush for all tail pages of compound page

From: Muchun Song <songmuchun@...edance.com>

commit 2771739a7162782c0aa6424b2e3dd874e884a15d upstream.

The D-cache maintenance inside move_to_new_page() only consider one
page, there is still D-cache maintenance issue for tail pages of
compound page (e.g. THP or HugeTLB).

THP migration is only enabled on x86_64, ARM64 and powerpc, while
powerpc and arm64 need to maintain the consistency between I-Cache and
D-Cache, which depends on flush_dcache_page() to maintain the
consistency between I-Cache and D-Cache.

But there is no issues on arm64 and powerpc since they already considers
the compound page cache flushing in their icache flush function.
HugeTLB migration is enabled on arm, arm64, mips, parisc, powerpc,
riscv, s390 and sh, while arm has handled the compound page cache flush
in flush_dcache_page(), but most others do not.

In theory, the issue exists on many architectures.  Fix this by not
using flush_dcache_folio() since it is not backportable.

Link: https://lkml.kernel.org/r/20220210123058.79206-3-songmuchun@bytedance.com
Fixes: 290408d4a250 ("hugetlb: hugepage migration core")
Signed-off-by: Muchun Song <songmuchun@...edance.com>
Reviewed-by: Zi Yan <ziy@...dia.com>
Cc: Axel Rasmussen <axelrasmussen@...gle.com>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Fam Zheng <fam.zheng@...edance.com>
Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Lars Persson <lars.persson@...s.com>
Cc: Mike Kravetz <mike.kravetz@...cle.com>
Cc: Peter Xu <peterx@...hat.com>
Cc: Xiongchun Duan <duanxiongchun@...edance.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 mm/migrate.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1010,9 +1010,12 @@ static int move_to_new_page(struct page
 		if (!PageMappingFlags(page))
 			page->mapping = NULL;
 
-		if (likely(!is_zone_device_page(newpage)))
-			flush_dcache_page(newpage);
+		if (likely(!is_zone_device_page(newpage))) {
+			int i, nr = compound_nr(newpage);
 
+			for (i = 0; i < nr; i++)
+				flush_dcache_page(newpage + i);
+		}
 	}
 out:
 	return rc;