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    Subject[PATCHv3, RFC 06/34] thp, mm: avoid PageUnevictable on active/inactive lru lists
    Date
    From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>

    active/inactive lru lists can contain unevicable pages (i.e. ramfs pages
    that have been placed on the LRU lists when first allocated), but these
    pages must not have PageUnevictable set - otherwise shrink_active_list
    goes crazy:

    kernel BUG at /home/space/kas/git/public/linux-next/mm/vmscan.c:1122!
    invalid opcode: 0000 [#1] SMP
    CPU 0
    Pid: 293, comm: kswapd0 Not tainted 3.8.0-rc6-next-20130202+ #531
    RIP: 0010:[<ffffffff81110478>] [<ffffffff81110478>] isolate_lru_pages.isra.61+0x138/0x260
    RSP: 0000:ffff8800796d9b28 EFLAGS: 00010082
    RAX: 00000000ffffffea RBX: 0000000000000012 RCX: 0000000000000001
    RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffffea0001de8040
    RBP: ffff8800796d9b88 R08: ffff8800796d9df0 R09: 0000000000000000
    R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000012
    R13: ffffea0001de8060 R14: ffffffff818818e8 R15: ffff8800796d9bf8
    FS: 0000000000000000(0000) GS:ffff88007a200000(0000) knlGS:0000000000000000
    CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 00007f1bfc108000 CR3: 000000000180b000 CR4: 00000000000406f0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
    Process kswapd0 (pid: 293, threadinfo ffff8800796d8000, task ffff880079e0a6e0)
    Stack:
    ffff8800796d9b48 ffffffff81881880 ffff8800796d9df0 ffff8800796d9be0
    0000000000000002 000000000000001f ffff8800796d9b88 ffffffff818818c8
    ffffffff81881480 ffff8800796d9dc0 0000000000000002 000000000000001f
    Call Trace:
    [<ffffffff81111e98>] shrink_inactive_list+0x108/0x4a0
    [<ffffffff8109ce3d>] ? trace_hardirqs_off+0xd/0x10
    [<ffffffff8107b8bf>] ? local_clock+0x4f/0x60
    [<ffffffff8110ff5d>] ? shrink_slab+0x1fd/0x4c0
    [<ffffffff811125a1>] shrink_zone+0x371/0x610
    [<ffffffff8110ff75>] ? shrink_slab+0x215/0x4c0
    [<ffffffff81112dfc>] kswapd+0x5bc/0xb60
    [<ffffffff81112840>] ? shrink_zone+0x610/0x610
    [<ffffffff81066676>] kthread+0xd6/0xe0
    [<ffffffff810665a0>] ? __kthread_bind+0x40/0x40
    [<ffffffff814fed6c>] ret_from_fork+0x7c/0xb0
    [<ffffffff810665a0>] ? __kthread_bind+0x40/0x40
    Code: 1f 40 00 49 8b 45 08 49 8b 75 00 48 89 46 08 48 89 30 49 8b 06 4c 89 68 08 49 89 45 00 4d 89 75 08 4d 89 2e eb 9c 0f 1f 44 00 00 <0f> 0b 66 0f 1f 44 00 00 31 db 45 31 e4 eb 9b 0f 0b 0f 0b 65 48
    RIP [<ffffffff81110478>] isolate_lru_pages.isra.61+0x138/0x260
    RSP <ffff8800796d9b28>

    For lru_add_page_tail(), it means we should not set PageUnevictable()
    for tail pages unless we're sure that it will go to LRU_UNEVICTABLE.
    Let's just copy PG_active and PG_unevictable from head page in
    __split_huge_page_refcount(), it will simplify lru_add_page_tail().

    This will fix one more bug in lru_add_page_tail():
    if page_evictable(page_tail) is false and PageLRU(page) is true, page_tail
    will go to the same lru as page, but nobody cares to sync page_tail
    active/inactive state with page. So we can end up with inactive page on
    active lru.
    The patch will fix it as well since we copy PG_active from head page.

    Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    ---
    mm/huge_memory.c | 4 +++-
    mm/swap.c | 20 ++------------------
    2 files changed, 5 insertions(+), 19 deletions(-)

    diff --git a/mm/huge_memory.c b/mm/huge_memory.c
    index e2f7f5aa..46a44ac 100644
    --- a/mm/huge_memory.c
    +++ b/mm/huge_memory.c
    @@ -1613,7 +1613,9 @@ static void __split_huge_page_refcount(struct page *page)
    ((1L << PG_referenced) |
    (1L << PG_swapbacked) |
    (1L << PG_mlocked) |
    - (1L << PG_uptodate)));
    + (1L << PG_uptodate) |
    + (1L << PG_active) |
    + (1L << PG_unevictable)));
    page_tail->flags |= (1L << PG_dirty);

    /* clear PageTail before overwriting first_page */
    diff --git a/mm/swap.c b/mm/swap.c
    index 92a9be5..20d78b6 100644
    --- a/mm/swap.c
    +++ b/mm/swap.c
    @@ -740,8 +740,6 @@ EXPORT_SYMBOL(__pagevec_release);
    void lru_add_page_tail(struct page *page, struct page *page_tail,
    struct lruvec *lruvec)
    {
    - int uninitialized_var(active);
    - enum lru_list lru;
    const int file = 0;

    VM_BUG_ON(!PageHead(page));
    @@ -752,20 +750,6 @@ void lru_add_page_tail(struct page *page, struct page *page_tail,

    SetPageLRU(page_tail);

    - if (page_evictable(page_tail)) {
    - if (PageActive(page)) {
    - SetPageActive(page_tail);
    - active = 1;
    - lru = LRU_ACTIVE_ANON;
    - } else {
    - active = 0;
    - lru = LRU_INACTIVE_ANON;
    - }
    - } else {
    - SetPageUnevictable(page_tail);
    - lru = LRU_UNEVICTABLE;
    - }
    -
    if (likely(PageLRU(page)))
    list_add_tail(&page_tail->lru, &page->lru);
    else {
    @@ -777,13 +761,13 @@ void lru_add_page_tail(struct page *page, struct page *page_tail,
    * Use the standard add function to put page_tail on the list,
    * but then correct its position so they all end up in order.
    */
    - add_page_to_lru_list(page_tail, lruvec, lru);
    + add_page_to_lru_list(page_tail, lruvec, page_lru(page_tail));
    list_head = page_tail->lru.prev;
    list_move_tail(&page_tail->lru, list_head);
    }

    if (!PageUnevictable(page))
    - update_page_reclaim_stat(lruvec, file, active);
    + update_page_reclaim_stat(lruvec, file, PageActive(page_tail));
    }
    #endif /* CONFIG_TRANSPARENT_HUGEPAGE */

    --
    1.7.10.4


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