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    Subject[PATCH 31/70] mm compaction: fix of improper cache flush in migration code
    Date
    3.5.7.14 -stable review patch.  If anyone has any objections, please let me know.

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

    From: Leonid Yegoshin <Leonid.Yegoshin@imgtec.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@imgtec.com>
    Cc: Leonid Yegoshin <yegoshin@mips.com>
    Acked-by: Rik van Riel <riel@redhat.com>
    Cc: Michal Hocko <mhocko@suse.cz>
    Acked-by: Mel Gorman <mgorman@suse.de>
    Cc: Ralf Baechle <ralf@linux-mips.org>
    Cc: Russell King <rmk@arm.linux.org.uk>
    Cc: David Miller <davem@davemloft.net>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Luis Henriques <luis.henriques@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


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