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[109.81.88.11]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-486f4bbe471sm41130335e9.27.2026.03.19.02.29.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Mar 2026 02:29:16 -0700 (PDT) Date: Thu, 19 Mar 2026 10:29:15 +0100 From: Michal Hocko To: Bing Jiao Cc: akpm@linux-foundation.org, axelrasmussen@google.com, baohua@kernel.org, bhe@redhat.com, cgroups@vger.kernel.org, chrisl@kernel.org, david@kernel.org, hannes@cmpxchg.org, joshua.hahnjy@gmail.com, kasong@tencent.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ljs@kernel.org, muchun.song@linux.dev, nphamcs@gmail.com, rientjes@google.com, roman.gushchin@linux.dev, shakeel.butt@linux.dev, shikemeng@huaweicloud.com, weixugc@google.com, yosry@kernel.org, youngjun.park@lge.com, yuanchu@google.com, zhengqi.arch@bytedance.com Subject: Re: [PATCH v3] mm/memcontrol: fix reclaim_options leak in try_charge_memcg() Message-ID: References: <20260318215629.2849052-1-bingjiao@google.com> <20260318221957.2979346-1-bingjiao@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260318221957.2979346-1-bingjiao@google.com> On Wed 18-03-26 22:19:46, Bing Jiao wrote: > In try_charge_memcg(), the 'reclaim_options' variable is initialized > once at the start of the function. However, the function contains a > retry loop. If reclaim_options were modified during an iteration > (e.g., by encountering a memsw limit), the modified state would > persist into subsequent retries. > > This leads to incorrect reclaim behavior. Specifically, > MEMCG_RECLAIM_MAY_SWAP is cleared when the combined memcg->memsw limit > is reached. After reclaimation attemps, a subsequent retry may > successfully charge memcg->memsw but fail on the memcg->memory charge. > In this case, swapping should be permitted, but the carried-over state > prevents it. Have you noticed this happening in practice or is this based on the code reading? > Fix by moving the initialization of 'reclaim_options' inside the > retry loop, ensuring a clean state for every reclaim attempt. > > Fixes: 6539cc053869 ("mm: memcontrol: fold mem_cgroup_do_charge()") > Signed-off-by: Bing Jiao > Reviewed-by: Yosry Ahmed Acked-by: Michal Hocko Thanks! > --- > v3: > - Corrected the Fixes tag (Yosry). > > mm/memcontrol.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index a47fb68dd65f..303ac622d22d 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -2558,7 +2558,7 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask, > struct page_counter *counter; > unsigned long nr_reclaimed; > bool passed_oom = false; > - unsigned int reclaim_options = MEMCG_RECLAIM_MAY_SWAP; > + unsigned int reclaim_options; > bool drained = false; > bool raised_max_event = false; > unsigned long pflags; > @@ -2572,6 +2572,7 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask, > /* Avoid the refill and flush of the older stock */ > batch = nr_pages; > > + reclaim_options = MEMCG_RECLAIM_MAY_SWAP; > if (!do_memsw_account() || > page_counter_try_charge(&memcg->memsw, batch, &counter)) { > if (page_counter_try_charge(&memcg->memory, batch, &counter)) > -- > 2.53.0.851.ga537e3e6e9-goog -- Michal Hocko SUSE Labs