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Sat, 15 Aug 2026 00:50:53 +0000 X-Migadu-Flow: FLOW_OUT Date: Fri, 14 Aug 2026 17:50:48 -0700 From: Shakeel Butt To: Michal Hocko Cc: Andrew Morton , Johannes Weiner , Roman Gushchin , Muchun Song , David Hildenbrand , Lorenzo Stoakes , Kairui Song , Qi Zheng , Barry Song , Axel Rasmussen , Meta kernel team , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+12ee2725d5fde63a9c96@syzkaller.appspotmail.com Subject: Re: [PATCH 1/9] memcg: make the v1 soft limit knob inert Message-ID: References: <20260811203203.3456029-1-shakeel.butt@linux.dev> <20260811203203.3456029-2-shakeel.butt@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: F3CE5120002 X-Rspamd-Server: rspam10 X-Rspam-User: X-Stat-Signature: n4ezq37n9psr34o17cm7dhgdbj5t9iwu X-HE-Tag: 1786755054-283185 X-HE-Meta: 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 a1k23iV0 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Aug 13, 2026 at 10:22:57AM +0200, Michal Hocko wrote: > On Tue 11-08-26 13:31:55, Shakeel Butt wrote: > > The v1 soft limit has been deprecated since v6.12 and nobody has > > reported depending on it. Start the removal by decoupling the interface > > from the implementation: keep memory.soft_limit_in_bytes, but ignore > > writes to it and always report the maximum value on read similar to > > what memory.kmem.limit_in_bytes already does. > > > > Writes are still parsed, so malformed input keeps returning -EINVAL. > > The knob now also behaves the same everywhere: it used to return > > -EOPNOTSUPP on PREEMPT_RT, where soft limit reclaim has always been > > disabled. > > Is there any specific reason to not return EOPNOTSUPP for everybody now? I followed the memory.kmem.limit_in_bytes example. If you have strong opinion, I am ok with EOPNOTSUPP as well. > > > This also fixes the syzbot report linked below. Soft limit reclaim is > > the only caller that runs shrink_lruvec() from kswapd against a > > specific memcg, so it is the only way to reach lru_gen_shrink_lruvec() > > and in turn set_mm_walk(), which warns when called from kswapd. > > > > Reported-by: syzbot+12ee2725d5fde63a9c96@syzkaller.appspotmail.com > > Closes: https://lore.kernel.org/all/6a7a6929.b50370da.49fe0.005e.GAE@google.com/ > > Signed-off-by: Shakeel Butt > > Anyway > Acked-by: Michal Hocko Thanks for reviewing the series.