Re: [PATCH] mm: memcontrol: drop unnecessary task_will_free_mem() check.

[Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>]

Michal Hocko wrote:
> On Wed 09-03-16 00:15:10, Tetsuo Handa wrote:
> > Since mem_cgroup_out_of_memory() is called by
> > mem_cgroup_oom_synchronize(true) via pagefault_out_of_memory() via
> > page fault, and possible allocations between setting PF_EXITING and
> > calling exit_mm() are tty_audit_exit() and taskstats_exit() which will
> > not trigger page fault, task_will_free_mem(current) in
> > mem_cgroup_out_of_memory() is never true.
> 
> What about exit_robust_list called from mm_release?
> 
> Anyway I guess we can indeed remove the check because try_charge will
> bypass the charge if we are exiting so we shouldn't even reach this path
> with PF_EXITING. But I haven't double checked. The above changelog seems
> to be incorrect, though.
> 

Indeed. do_exit()->exit_mm()->mm_release()->exit_robust_list()->get_user()
can trigger page fault.

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