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    Subject[PATCH v17 15/21] mm/thp: add tail pages into lru anyway in split_huge_page()
    Date
    Split_huge_page() must start with PageLRU(head), and we are holding the
    lru_lock here. If the head was cleared lru bit unexpected, tracking it.

    Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
    Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    Cc: Kirill A. Shutemov <kirill@shutemov.name>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Johannes Weiner <hannes@cmpxchg.org>
    Cc: Matthew Wilcox <willy@infradead.org>
    Cc: Hugh Dickins <hughd@google.com>
    Cc: Mika Penttilä <mika.penttila@nextfour.com>
    Cc: linux-mm@kvack.org
    Cc: linux-kernel@vger.kernel.org
    ---
    mm/huge_memory.c | 16 ++++++++++------
    1 file changed, 10 insertions(+), 6 deletions(-)

    diff --git a/mm/huge_memory.c b/mm/huge_memory.c
    index d866b6e43434..28538444197b 100644
    --- a/mm/huge_memory.c
    +++ b/mm/huge_memory.c
    @@ -2348,15 +2348,19 @@ static void lru_add_page_tail(struct page *head, struct page *page_tail,
    VM_BUG_ON_PAGE(PageLRU(page_tail), head);
    lockdep_assert_held(&lruvec_pgdat(lruvec)->lru_lock);

    - if (!list)
    - SetPageLRU(page_tail);
    -
    - if (likely(PageLRU(head)))
    - list_add_tail(&page_tail->lru, &head->lru);
    - else if (list) {
    + if (list) {
    /* page reclaim is reclaiming a huge page */
    get_page(page_tail);
    list_add_tail(&page_tail->lru, list);
    + } else {
    + /*
    + * Split start from PageLRU(head), and we are holding the
    + * lru_lock.
    + * Do a warning if the head's lru bit was cleared unexpected.
    + */
    + VM_WARN_ON(!PageLRU(head));
    + SetPageLRU(page_tail);
    + list_add_tail(&page_tail->lru, &head->lru);
    }
    }

    --
    1.8.3.1
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