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Date:   Wed, 29 Nov 2023 12:00:01 -0500
From:   Johannes Weiner <hannes@cmpxchg.org>
To:     Nhat Pham <nphamcs@gmail.com>
Cc:     akpm@linux-foundation.org, cerasuolodomenico@gmail.com,
        yosryahmed@google.com, sjenning@redhat.com, ddstreet@ieee.org,
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        roman.gushchin@linux.dev, shakeelb@google.com,
        muchun.song@linux.dev, chrisl@kernel.org, linux-mm@kvack.org,
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        linux-kselftest@vger.kernel.org, shuah@kernel.org
Subject: Re: [PATCH v7 2/6] memcontrol: add a new function to traverse
 online-only memcg hierarchy
Message-ID: <20231129170001.GF135852@cmpxchg.org>
References: <20231127234600.2971029-1-nphamcs@gmail.com>
 <20231127234600.2971029-3-nphamcs@gmail.com>
 <20231129150403.GB135852@cmpxchg.org>
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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@linux-foundation.org>
> > Signed-off-by: Nhat Pham <nphamcs@gmail.com>
> 
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>

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.