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Subject[PATCH][BUGFIX] memcg: fix leak of accounting at failure path of hugepage collapsing.
There was a big bug. Anyway, thank you for adding new bad_page for memcg.
==

mem_cgroup_uncharge_page() should be called in all failure case
after mem_cgroup_charge_newpage() is called in
huge_memory.c::collapse_huge_page()

[ 4209.076861] BUG: Bad page state in process khugepaged pfn:1e9800
[ 4209.077601] page:ffffea0006b14000 count:0 mapcount:0 mapping: (null) index:0x2800
[ 4209.078674] page flags: 0x40000000004000(head)
[ 4209.079294] pc:ffff880214a30000 pc->flags:2146246697418756 pc->mem_cgroup:ffffc9000177a000
[ 4209.082177] (/A)
[ 4209.082500] Pid: 31, comm: khugepaged Not tainted 2.6.38-rc3-mm1 #1
[ 4209.083412] Call Trace:
[ 4209.083678] [<ffffffff810f4454>] ? bad_page+0xe4/0x140
[ 4209.084240] [<ffffffff810f53e6>] ? free_pages_prepare+0xd6/0x120
[ 4209.084837] [<ffffffff8155621d>] ? rwsem_down_failed_common+0xbd/0x150
[ 4209.085509] [<ffffffff810f5462>] ? __free_pages_ok+0x32/0xe0
[ 4209.086110] [<ffffffff810f552b>] ? free_compound_page+0x1b/0x20
[ 4209.086699] [<ffffffff810fad6c>] ? __put_compound_page+0x1c/0x30
[ 4209.087333] [<ffffffff810fae1d>] ? put_compound_page+0x4d/0x200
[ 4209.087935] [<ffffffff810fb015>] ? put_page+0x45/0x50
[ 4209.097361] [<ffffffff8113f779>] ? khugepaged+0x9e9/0x1430
[ 4209.098364] [<ffffffff8107c870>] ? autoremove_wake_function+0x0/0x40
[ 4209.099121] [<ffffffff8113ed90>] ? khugepaged+0x0/0x1430
[ 4209.099780] [<ffffffff8107c236>] ? kthread+0x96/0xa0
[ 4209.100452] [<ffffffff8100dda4>] ? kernel_thread_helper+0x4/0x10
[ 4209.101214] [<ffffffff8107c1a0>] ? kthread+0x0/0xa0
[ 4209.101842] [<ffffffff8100dda0>] ? kernel_thread_helper+0x0/0x10


Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
mm/huge_memory.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

Index: mmotm-0204/mm/huge_memory.c
===================================================================
--- mmotm-0204.orig/mm/huge_memory.c
+++ mmotm-0204/mm/huge_memory.c
@@ -1852,7 +1852,6 @@ static void collapse_huge_page(struct mm
set_pmd_at(mm, address, pmd, _pmd);
spin_unlock(&mm->page_table_lock);
anon_vma_unlock(vma->anon_vma);
- mem_cgroup_uncharge_page(new_page);
goto out;
}

@@ -1898,6 +1897,7 @@ out_up_write:
return;

out:
+ mem_cgroup_uncharge_page(new_page);
#ifdef CONFIG_NUMA
put_page(new_page);
#endif


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