[067/227] mm: fix missing cache flush for all tail pages of compound page

Commit Message

Andrew Morton March 22, 2022, 9:41 p.m. UTC

From: Muchun Song <[e-mail]>
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 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/[e-mail]
Fixes: 290408d4a250 ("hugetlb: hugepage migration core")
Signed-off-by: Muchun Song <[e-mail]>
Reviewed-by: Zi Yan <[e-mail]>
Cc: Axel Rasmussen <[e-mail]>
Cc: David Rientjes <[e-mail]>
Cc: Fam Zheng <[e-mail]>
Cc: Kirill A. Shutemov <[e-mail]>
Cc: Lars Persson <[e-mail]>
Cc: Mike Kravetz <[e-mail]>
Cc: Peter Xu <[e-mail]>
Cc: Xiongchun Duan <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

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

Patch

--- 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;