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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1772711814; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ZbG23+zJ5fPDETZsA4JYiiScdZSpnAwzCU/omjW9+7Y=; b=fe+nMrSJbiyNEjT8QnfP2jiU7zSCtJUFDhUkZ6xW8MCf6wGdRSGgSko4Kwhc4zPQBedWa5 DmrzF7ubIzkhASX91nLHrdY9b0eWVYN48Ccc0XZJ8LXDN4O7BgEnue4o3MoZ2JmNDreaDv bQfDWzg57Ggq6hClfYxiaK4sGUfw26M= From: Qi Zheng To: hannes@cmpxchg.org, hughd@google.com, mhocko@suse.com, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, david@kernel.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com, harry.yoo@oracle.com, yosry.ahmed@linux.dev, imran.f.khan@oracle.com, kamalesh.babulal@oracle.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, chenridong@huaweicloud.com, mkoutny@suse.com, akpm@linux-foundation.org, hamzamahfooz@linux.microsoft.com, apais@linux.microsoft.com, lance.yang@linux.dev, bhe@redhat.com, usamaarif642@gmail.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Muchun Song , Qi Zheng Subject: [PATCH v6 16/33] mm: workingset: prevent memory cgroup release in lru_gen_eviction() Date: Thu, 5 Mar 2026 19:52:34 +0800 Message-ID: In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 3227AA000B X-Stat-Signature: gighfhax4se6kma8pztrj9qu61w3ukn8 X-Rspam-User: X-HE-Tag: 1772711815-297178 X-HE-Meta: U2FsdGVkX19I86lqxlC/AMbisGfH+I7xk6+L1JczOEf9yDBoLc19cqlp5lw7b0SgyLAJgAszyI2xokKs02K7KpfTuy+2aH4LkU1TYvsnh9+mOjGtIQuqxOHZtvkLino5yRtmorOT6wb9d9UOwU/AzuGsTNYtzAW8A8iLvyTV8SpPiOMtMsg+K0YE5kGZSIkqqoI9niNY1RhaKkdzsdQ4qcaQKeZr1MM4lTqw6KGtEJMLUuEOj+vWV8MALw7OejefcsC0TpPqw/Q+/AP3+CRfWBRlOaRWgnhv9E8FFsDh8I5yHWT/LZI3Vjlt0fNTNSZFs7mLwlm9EaDVN0MkMUiDb7TgD5ABYCVwYhrdFs1sTjrSE4lqhWETRP7wnq30NghdukY3fcfaEh7T6SL7i4ErcM2t5+LkFqRbLXXdIYz+XKIr4DK9TFMoETyK+ENJOEau3hj8F8hg4a5XI5Q+Wl9Eayzo/DYRgZ6erTexr/8bSFw7eWKt2Kj4KzL3XLyZ7OZPNX05uWECqDQstFOZ3v34YWJ92uJEBwrPx6m4OdcYM4J2M/OddUxPeZQSGpheVkjCvnRyXAKPsNsthoqe53spRBpq3kHmITxbxdBZkjtASO+l3jNcjnf3EF8QwWHgQlZ90+F35ysXDmn9SypT6oQIxoF55bvxPhVCY09+OPM2v0alLIi92Zx+LL8j4ClTZRd9dsQVB70MLQIxVJyH3ppHUYgMJ5bdMIf9Nvu+Jtn7mX8FX7C3d/BzX8WRHvGOER++WG+6obmDOCigcJotuwzQ2t4zngs79D8MwvJAPxzZ4Wy819ETCAU/G+00UXjIv45OLB/Mn3heD5kSl+b6gQL5JpDkaQNH5IfyOhqJNOmhy1JqSazeURDXoy1GIGbiJgjWejhvTJ5umCRw6UTQsBJHxd5T7vb5m5f9 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Muchun Song In the near future, a folio will no longer pin its corresponding memory cgroup. To ensure safety, it will only be appropriate to hold the rcu read lock or acquire a reference to the memory cgroup returned by folio_memcg(), thereby preventing it from being released. In the current patch, the rcu read lock is employed to safeguard against the release of the memory cgroup in lru_gen_eviction(). This serves as a preparatory measure for the reparenting of the LRU pages. Signed-off-by: Muchun Song Signed-off-by: Qi Zheng Reviewed-by: Harry Yoo Acked-by: Johannes Weiner Acked-by: Shakeel Butt --- mm/workingset.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/mm/workingset.c b/mm/workingset.c index 5e8b6e62a6175..6971aa163e466 100644 --- a/mm/workingset.c +++ b/mm/workingset.c @@ -244,12 +244,15 @@ static void *lru_gen_eviction(struct folio *folio) int refs = folio_lru_refs(folio); bool workingset = folio_test_workingset(folio); int tier = lru_tier_from_refs(refs, workingset); - struct mem_cgroup *memcg = folio_memcg(folio); + struct mem_cgroup *memcg; struct pglist_data *pgdat = folio_pgdat(folio); + unsigned short memcg_id; BUILD_BUG_ON(LRU_GEN_WIDTH + LRU_REFS_WIDTH > BITS_PER_LONG - max(EVICTION_SHIFT, EVICTION_SHIFT_ANON)); + rcu_read_lock(); + memcg = folio_memcg(folio); lruvec = mem_cgroup_lruvec(memcg, pgdat); lrugen = &lruvec->lrugen; min_seq = READ_ONCE(lrugen->min_seq[type]); @@ -257,8 +260,10 @@ static void *lru_gen_eviction(struct folio *folio) hist = lru_hist_from_seq(min_seq); atomic_long_add(delta, &lrugen->evicted[hist][type][tier]); + memcg_id = mem_cgroup_private_id(memcg); + rcu_read_unlock(); - return pack_shadow(mem_cgroup_private_id(memcg), pgdat, token, workingset, type); + return pack_shadow(memcg_id, pgdat, token, workingset, type); } /* -- 2.20.1