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Howlett" , Usama Arif , Kiryl Shutsemau , Vlastimil Babka , Kairui Song , Mikhail Zaslonko , Vasily Gorbik , Baolin Wang , Barry Song , Dev Jain , Lance Yang , Nico Pache , Ryan Roberts , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 1/9] mm: list_lru: fix set_shrinker_bit() call during race with cgroup deletion Message-ID: <20260530023802.l5f6ywulxl2bpafg@master> Reply-To: Wei Yang References: <20260527204757.2544958-1-hannes@cmpxchg.org> <20260527204757.2544958-2-hannes@cmpxchg.org> 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: <20260527204757.2544958-2-hannes@cmpxchg.org> User-Agent: NeoMutt/20170113 (1.7.2) On Wed, May 27, 2026 at 04:45:08PM -0400, Johannes Weiner wrote: >When list_lru_add() races with cgroup deletion, the shrinker bit is set >on the wrong group and lost. This can cause a shrinker run to miss the >cgroup that actually has the object. > >When the passed in memcg is dead, the function finds the first non-dead >parent from the passed in memcg and adds the object there; but the >shrinker bit is set on the memcg that was passed in. > This means we just miss to reclaim some obj, but won't crash the kernel. >This bug is as old as the shrinker bitmap itself. > >Fix it by returning the "effective" memcg from the locking function, and >have the caller use that. > >Fixes: fae91d6d8be5 ("mm/list_lru.c: set bit in memcg shrinker bitmap on first list_lru item appearance") >Reported-by: Usama Arif >Reported-by: Sashiko >Signed-off-by: Johannes Weiner So we don't want to cc stable, right? The fix looks right, so Reviewed-by: Wei Yang -- Wei Yang Help you, Help me