[ 3.5.y.z extended stable ] Patch "mm compaction: fix of improper cache flush in migration code" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    mm compaction: fix of improper cache flush in migration code

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From a2827fda45795970f4d2b41db650dd51e334852c Mon Sep 17 00:00:00 2001
From: Leonid Yegoshin <Leonid.Yegoshin at imgtec.com>
Date: Fri, 24 May 2013 15:55:18 -0700
Subject: [PATCH] mm compaction: fix of improper cache flush in migration code

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 at imgtec.com>
Cc: Leonid Yegoshin <yegoshin at mips.com>
Acked-by: Rik van Riel <riel at redhat.com>
Cc: Michal Hocko <mhocko at suse.cz>
Acked-by: Mel Gorman <mgorman at suse.de>
Cc: Ralf Baechle <ralf at linux-mips.org>
Cc: Russell King <rmk at arm.linux.org.uk>
Cc: David Miller <davem at davemloft.net>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 mm/migrate.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 2e03986..65cc229 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -147,7 +147,7 @@ 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