linux-kernel - [63/94] mm compaction: fix of improper cache flush in migration code

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Date:	Tue, 28 May 2013 04:49:53 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Leonid Yegoshin" <Leonid.Yegoshin@...tec.com>,
	"Russell King" <rmk@....linux.org.uk>,
	"David Miller" <davem@...emloft.net>,
	"Rik van Riel" <riel@...hat.com>,
	"Ralf Baechle" <ralf@...ux-mips.org>,
	"Leonid Yegoshin" <yegoshin@...s.com>,
	"Mel Gorman" <mgorman@...e.de>, "Michal Hocko" <mhocko@...e.cz>
Subject: [63/94] mm compaction: fix of improper cache flush in migration code

3.2.46-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Leonid Yegoshin <Leonid.Yegoshin@...tec.com>

commit c2cc499c5bcf9040a738f49e8051b42078205748 upstream.

Page 'new' during MIGRATION can't be flushed with flush_cache_page().
Using flush_cache_page(vma, addr, pfn) is justified only if the page is
already placed in process page table, and that is done right after
flush_cache_page().  But without it the arch function has no knowledge
of process PTE and does nothing.

Besides that, flush_cache_page() flushes an application cache page, but
the kernel has a different page virtual address and dirtied it.

Replace it with flush_dcache_page(new) which is the proper usage.

The old page is flushed in try_to_unmap_one() before migration.

This bug takes place in Sead3 board with M14Kc MIPS CPU without cache
aliasing (but Harvard arch - separate I and D cache) in tight memory
environment (128MB) each 1-3days on SOAK test.  It fails in cc1 during
kernel build (SIGILL, SIGBUS, SIGSEG) if CONFIG_COMPACTION is switched
ON.

Signed-off-by: Leonid Yegoshin <Leonid.Yegoshin@...tec.com>
Cc: Leonid Yegoshin <yegoshin@...s.com>
Acked-by: Rik van Riel <riel@...hat.com>
Cc: Michal Hocko <mhocko@...e.cz>
Acked-by: Mel Gorman <mgorman@...e.de>
Cc: Ralf Baechle <ralf@...ux-mips.org>
Cc: Russell King <rmk@....linux.org.uk>
Cc: David Miller <davem@...emloft.net>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 mm/migrate.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -147,7 +147,7 @@ static int remove_migration_pte(struct p
 	if (PageHuge(new))
 		pte = pte_mkhuge(pte);
 #endif
-	flush_cache_page(vma, addr, pte_pfn(pte));
+	flush_dcache_page(new);
 	set_pte_at(mm, addr, ptep, pte);

 	if (PageHuge(new)) {

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