Re: [PATCH v7 2/6] memcontrol: add a new function to traverse online-only memcg hierarchy

[Johannes Weiner]

On Wed, Nov 29, 2023 at 10:04:05AM -0500, Johannes Weiner wrote:
> On Mon, Nov 27, 2023 at 03:45:56PM -0800, Nhat Pham wrote:
> > The new zswap writeback scheme requires an online-only memcg hierarchy
> > traversal. Add this functionality via the new mem_cgroup_iter_online()
> > function - the old mem_cgroup_iter() is a special case of this new
> > function.
> > 
> > Suggested-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Nhat Pham <nphamcs@xxxxxxxxx>
> 
> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>

I saw Michal's reply on the other thread only after I sent this.

I agree with him it would be better to just check mem_cgroup_online()
in the shinker callsite and leave mem_cgroup_iter() as-is. If it's
offline, just continue to the next mem_cgroup_iter() invocation.