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    Subject[PATCH 5.10 371/452] mm, compaction: fast_find_migrateblock() should return pfn in the target zone
    Date
    From: Rei Yamamoto <yamamoto.rei@jp.fujitsu.com>

    commit bbe832b9db2e1ad21522f8f0bf02775fff8a0e0e upstream.

    At present, pages not in the target zone are added to cc->migratepages
    list in isolate_migratepages_block(). As a result, pages may migrate
    between nodes unintentionally.

    This would be a serious problem for older kernels without commit
    a984226f457f849e ("mm: memcontrol: remove the pgdata parameter of
    mem_cgroup_page_lruvec"), because it can corrupt the lru list by
    handling pages in list without holding proper lru_lock.

    Avoid returning a pfn outside the target zone in the case that it is
    not aligned with a pageblock boundary. Otherwise
    isolate_migratepages_block() will handle pages not in the target zone.

    Link: https://lkml.kernel.org/r/20220511044300.4069-1-yamamoto.rei@jp.fujitsu.com
    Fixes: 70b44595eafe ("mm, compaction: use free lists to quickly locate a migration source")
    Signed-off-by: Rei Yamamoto <yamamoto.rei@jp.fujitsu.com>
    Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
    Acked-by: Mel Gorman <mgorman@techsingularity.net>
    Reviewed-by: Oscar Salvador <osalvador@suse.de>
    Cc: Don Dutile <ddutile@redhat.com>
    Cc: Wonhyuk Yang <vvghjk1234@gmail.com>
    Cc: Rei Yamamoto <yamamoto.rei@jp.fujitsu.com>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    mm/compaction.c | 2 ++
    1 file changed, 2 insertions(+)

    --- a/mm/compaction.c
    +++ b/mm/compaction.c
    @@ -1747,6 +1747,8 @@ static unsigned long fast_find_migratebl

    update_fast_start_pfn(cc, free_pfn);
    pfn = pageblock_start_pfn(free_pfn);
    + if (pfn < cc->zone->zone_start_pfn)
    + pfn = cc->zone->zone_start_pfn;
    cc->fast_search_fail = 0;
    found_block = true;
    set_pageblock_skip(freepage);

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