linux-kernel - [PATCH 50/75] mm compaction: fix of improper cache flush in migration code

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Message-Id: <1370364959-9475-51-git-send-email-kamal@canonical.com>
Date:	Tue,  4 Jun 2013 09:55:34 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Leonid Yegoshin <Leonid.Yegoshin@...tec.com>,
	Leonid Yegoshin <yegoshin@...s.com>,
	Michal Hocko <mhocko@...e.cz>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Russell King <rmk@....linux.org.uk>,
	David Miller <davem@...emloft.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 50/75] mm compaction: fix of improper cache flush in migration code

3.8.13.2 -stable 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: Kamal Mostafa <kamal@...onical.com>
---
 mm/migrate.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 2fd8b4a..4c6250a 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -165,7 +165,7 @@ static int remove_migration_pte(struct page *new, struct vm_area_struct *vma,
 		pte = arch_make_huge_pte(pte, vma, new, 0);
 	}
 #endif
-	flush_cache_page(vma, addr, pte_pfn(pte));
+	flush_dcache_page(new);
 	set_pte_at(mm, addr, ptep, pte);

 	if (PageHuge(new)) {
-- 
1.8.1.2

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