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SubjectRe: [PATCH][BUGFIX] memcg: fix leak of accounting at failure path of hugepage collapsing.
On Wed, Feb 09, 2011 at 04:23:24PM +0900, KAMEZAWA Hiroyuki wrote:
> There was a big bug. Anyway, thank you for adding new bad_page for memcg.

That check is really awesome :-)

> 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>

Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>

Thanks for debugging this.


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