+ mm-fix-missing-cache-flush-for-all-tail-pages-of-compound-page.patch added to -mm tree

* + mm-fix-missing-cache-flush-for-all-tail-pages-of-compound-page.patch added to -mm tree
@ 2022-02-08 21:15 Andrew Morton
  0 siblings, 0 replies; 3+ messages in thread
From: Andrew Morton @ 2022-02-08 21:15 UTC (permalink / raw)
  To: mm-commits, ziy, willy, rientjes, mike.kravetz, lars.persson,
	kirill.shutemov, duanxiongchun, almasrymina, songmuchun, akpm


The patch titled
     Subject: mm: fix missing cache flush for all tail pages of compound page
has been added to the -mm tree.  Its filename is
     mm-fix-missing-cache-flush-for-all-tail-pages-of-compound-page.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-fix-missing-cache-flush-for-all-tail-pages-of-compound-page.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-fix-missing-cache-flush-for-all-tail-pages-of-compound-page.patch

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------------------------------------------------------
From: Muchun Song <songmuchun@bytedance.com>
Subject: mm: fix missing cache flush for all tail pages of compound page

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 are no issues on arm64 and powerpc since they already consider
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/20220208073617.70342-3-songmuchun@bytedance.com
Fixes: 290408d4a250 ("hugetlb: hugepage migration core")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lars Persson <lars.persson@axis.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/migrate.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/mm/migrate.c~mm-fix-missing-cache-flush-for-all-tail-pages-of-compound-page
+++ a/mm/migrate.c
@@ -916,9 +916,12 @@ 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;
_

Patches currently in -mm which might be from songmuchun@bytedance.com are

mm-thp-fix-wrong-cache-flush-in-remove_migration_pmd.patch
mm-fix-missing-cache-flush-for-all-tail-pages-of-compound-page.patch
mm-hugetlb-fix-missing-cache-flush-in-copy_huge_page_from_user.patch
mm-hugetlb-fix-missing-cache-flush-in-hugetlb_mcopy_atomic_pte.patch
mm-replace-multiple-dcache-flush-with-flush_dcache_folio.patch
mm-hugetlb-free-the-2nd-vmemmap-page-associated-with-each-hugetlb-page.patch
mm-hugetlb-replace-hugetlb_free_vmemmap_enabled-with-a-static_key.patch
mm-sparsemem-use-page-table-lock-to-protect-kernel-pmd-operations.patch
selftests-vm-add-a-hugetlb-test-case.patch
mm-sparsemem-move-vmemmap-related-to-hugetlb-to-config_hugetlb_page_free_vmemmap.patch


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