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    Subject[PATCH 4/4] memcg: fix rmdir, force_empty with THP

    Now, when THP is enabled, memcg's rmdir() function is broken
    because move_account() for THP page is not supported.

    This will cause account leak or -EBUSY issue at rmdir().
    This patch fixes the issue by supporting move_account() THP pages.

    Changelog:
    - style fix.
    - add compound_lock for avoiding races.

    Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    ---
    mm/memcontrol.c | 37 ++++++++++++++++++++++++++-----------
    1 file changed, 26 insertions(+), 11 deletions(-)

    Index: mmotm-0107/mm/memcontrol.c
    ===================================================================
    --- mmotm-0107.orig/mm/memcontrol.c
    +++ mmotm-0107/mm/memcontrol.c
    @@ -2197,8 +2197,11 @@ void mem_cgroup_split_huge_fixup(struct
    */

    static void __mem_cgroup_move_account(struct page_cgroup *pc,
    - struct mem_cgroup *from, struct mem_cgroup *to, bool uncharge)
    + struct mem_cgroup *from, struct mem_cgroup *to, bool uncharge,
    + int charge_size)
    {
    + int nr_pages = charge_size >> PAGE_SHIFT;
    +
    VM_BUG_ON(from == to);
    VM_BUG_ON(PageLRU(pc->page));
    VM_BUG_ON(!page_is_cgroup_locked(pc));
    @@ -2212,14 +2215,14 @@ static void __mem_cgroup_move_account(st
    __this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
    preempt_enable();
    }
    - mem_cgroup_charge_statistics(from, PageCgroupCache(pc), -1);
    + mem_cgroup_charge_statistics(from, PageCgroupCache(pc), -nr_pages);
    if (uncharge)
    /* This is not "cancel", but cancel_charge does all we need. */
    - mem_cgroup_cancel_charge(from, PAGE_SIZE);
    + mem_cgroup_cancel_charge(from, charge_size);

    /* caller should have done css_get */
    pc->mem_cgroup = to;
    - mem_cgroup_charge_statistics(to, PageCgroupCache(pc), 1);
    + mem_cgroup_charge_statistics(to, PageCgroupCache(pc), nr_pages);
    /*
    * We charges against "to" which may not have any tasks. Then, "to"
    * can be under rmdir(). But in current implementation, caller of
    @@ -2234,15 +2237,19 @@ static void __mem_cgroup_move_account(st
    * __mem_cgroup_move_account()
    */
    static int mem_cgroup_move_account(struct page_cgroup *pc,
    - struct mem_cgroup *from, struct mem_cgroup *to, bool uncharge)
    + struct mem_cgroup *from, struct mem_cgroup *to,
    + bool uncharge, int charge_size)
    {
    int ret = -EINVAL;
    unsigned long flags;

    + if ((charge_size > PAGE_SIZE) && !PageTransHuge(pc->page))
    + return -EBUSY;
    +
    lock_page_cgroup(pc);
    if (PageCgroupUsed(pc) && pc->mem_cgroup == from) {
    move_lock_page_cgroup(pc, &flags);
    - __mem_cgroup_move_account(pc, from, to, uncharge);
    + __mem_cgroup_move_account(pc, from, to, uncharge, charge_size);
    move_unlock_page_cgroup(pc, &flags);
    ret = 0;
    }
    @@ -2267,6 +2274,8 @@ static int mem_cgroup_move_parent(struct
    struct cgroup *cg = child->css.cgroup;
    struct cgroup *pcg = cg->parent;
    struct mem_cgroup *parent;
    + int charge = PAGE_SIZE;
    + unsigned long flags;
    int ret;

    /* Is ROOT ? */
    @@ -2278,17 +2287,23 @@ static int mem_cgroup_move_parent(struct
    goto out;
    if (isolate_lru_page(page))
    goto put;
    + /* The page is isolated from LRU and we have no race with splitting */
    + charge = PAGE_SIZE << compound_order(page);

    parent = mem_cgroup_from_cont(pcg);
    - ret = __mem_cgroup_try_charge(NULL, gfp_mask, &parent, false,
    - PAGE_SIZE);
    + ret = __mem_cgroup_try_charge(NULL, gfp_mask, &parent, false, charge);
    if (ret || !parent)
    goto put_back;

    - ret = mem_cgroup_move_account(pc, child, parent, true);
    + if (charge > PAGE_SIZE)
    + flags = compound_lock_irqsave(page);
    +
    + ret = mem_cgroup_move_account(pc, child, parent, true, charge);
    if (ret)
    - mem_cgroup_cancel_charge(parent, PAGE_SIZE);
    + mem_cgroup_cancel_charge(parent, charge);
    put_back:
    + if (charge > PAGE_SIZE)
    + compound_unlock_irqrestore(page, flags);
    putback_lru_page(page);
    put:
    put_page(page);
    @@ -4868,7 +4883,7 @@ retry:
    goto put;
    pc = lookup_page_cgroup(page);
    if (!mem_cgroup_move_account(pc,
    - mc.from, mc.to, false)) {
    + mc.from, mc.to, false, PAGE_SIZE)) {
    mc.precharge--;
    /* we uncharge from mc.from later. */
    mc.moved_charge++;


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