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    Subject[RFC][BUGFIX][PATCH 1/2] memcg: fix charge bypass route of migration
    I'd like to wait until next mmotm comes out. (So, [RFC]) I'll rebase
    This patch is based on
    mmotm-2010/04/05
    +
    mm-migration-take-a-reference-to-the-anon_vma-before-migrating.patch
    mm-migration-do-not-try-to-migrate-unmapped-anonymous-pages.patch
    mm-share-the-anon_vma-ref-counts-between-ksm-and-page-migration.patch
    mm-migration-allow-the-migration-of-pageswapcache-pages.patch
    memcg-fix-prepare-migration.patch

    ==
    From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

    This is an additonal fix to memcg-fix-prepare-migration.patch

    Now, try_charge can bypass charge if TIF_MEMDIE at el are marked on the caller.
    In this case, the charge is bypassed. This makes accounts corrupted.
    (PageCgroup will be marked as PCG_USED even if bypassed, and css->refcnt
    can leak.)

    This patch clears passed "*memcg" in bypass route.

    Because usual page allocater passes memcg=NULL, this patch only affects
    some special case as
    - move account
    - migration
    - swapin.

    Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    ---
    mm/memcontrol.c | 7 +++++--
    1 file changed, 5 insertions(+), 2 deletions(-)

    Index: mmotm-temp/mm/memcontrol.c
    ===================================================================
    --- mmotm-temp.orig/mm/memcontrol.c
    +++ mmotm-temp/mm/memcontrol.c
    @@ -1606,8 +1606,12 @@ static int __mem_cgroup_try_charge(struc
    * MEMDIE process.
    */
    if (unlikely(test_thread_flag(TIF_MEMDIE)
    - || fatal_signal_pending(current)))
    + || fatal_signal_pending(current))) {
    + /* Showing we skipped charge */
    + if (memcg)
    + *memcg = NULL;
    goto bypass;
    + }

    /*
    * We always charge the cgroup the mm_struct belongs to.
    @@ -2523,7 +2527,6 @@ int mem_cgroup_prepare_migration(struct
    ret = __mem_cgroup_try_charge(NULL, GFP_KERNEL, ptr, false);
    css_put(&mem->css);
    }
    - *ptr = mem;
    return ret;
    }






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