On Wed 11-01-17 20:32:12, David Rientjes wrote:
[...]
> This also restructures mem_cgroup_wait_acct_move() since it is not
> possible for mc.moving_task to be current.
thinking about this some more, I do not think this is the right way to
go. It is true that we will not reach mem_cgroup_wait_acct_move if all
the charges from the task moving code path are __GFP_NORETRY but that
is quite subtle requirement IMHO.
> Fixes: 0029e19ebf84 ("mm: memcontrol: remove explicit OOM parameter in charge path")
> Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
> ---
> mm/memcontrol.c | 32 +++++++++++++++++++-------------
> 1 file changed, 19 insertions(+), 13 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1125,18 +1125,19 @@ static bool mem_cgroup_under_move(struct mem_cgroup *memcg)
>
> static bool mem_cgroup_wait_acct_move(struct mem_cgroup *memcg)
> {
> - if (mc.moving_task && current != mc.moving_task) {
> - if (mem_cgroup_under_move(memcg)) {
> - DEFINE_WAIT(wait);
> - prepare_to_wait(&mc.waitq, &wait, TASK_INTERRUPTIBLE);
> - /* moving charge context might have finished. */
> - if (mc.moving_task)
> - schedule();
> - finish_wait(&mc.waitq, &wait);
> - return true;
> - }
> + DEFINE_WAIT(wait);
> +
> + if (likely(!mem_cgroup_under_move(memcg)))
> + return false;
> +
> + prepare_to_wait(&mc.waitq, &wait, TASK_INTERRUPTIBLE);
> + /* moving charge context might have finished. */
> + if (mc.moving_task) {
> + WARN_ON_ONCE(mc.moving_task == current);
> + schedule();
> }
> - return false;
> + finish_wait(&mc.waitq, &wait);
> + return true;
> }
>
> #define K(x) ((x) << (PAGE_SHIFT-10))
--
Michal Hocko
SUSE Labs
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