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Sun, 06 Sep 2026 00:47:28 -0700 (PDT) From: Jianyue Wu Date: Sun, 06 Sep 2026 15:47:17 +0800 Subject: [PATCH v6 1/3] mm/zswap: release retired pools via queue_rcu_work() instead of synchronize_rcu() 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="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260906-shrink_zswap_entry_v6-v6-1-ac4cf61565fb@gmail.com> References: <20260906-shrink_zswap_entry_v6-v6-0-ac4cf61565fb@gmail.com> In-Reply-To: <20260906-shrink_zswap_entry_v6-v6-0-ac4cf61565fb@gmail.com> To: Johannes Weiner , Yosry Ahmed , Nhat Pham , Chengming Zhou , Andrew Morton Cc: Chris Li , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Jianyue Wu X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=openssh-sha256; t=1788680840; l=2137; i=wujianyue000@gmail.com; s=id_ed25519; h=from:subject:message-id; bh=WwjbCGbpKx3pybwGrUA8/VZT5w49m4g/k61kb6kkG0c=; b=U1NIU0lHAAAAAQAAADMAAAALc3NoLWVkMjU1MTkAAAAgW51Zh3v9nG0Wlld2Ti8ylp1TnO7yB H+z9CbXty/WEAQAAAAGcGF0YXR0AAAAAAAAAAZzaGE1MTIAAABTAAAAC3NzaC1lZDI1NTE5AAAA QMYNV8pIDrz+M/tSuqNBmingl1zVngKIT7QYZIxy2wkQbA4+uO1BijhHckb3wo/z69o0S4pYyv9 Nlj2JS8UmdAg= X-Developer-Key: i=wujianyue000@gmail.com; a=openssh; fpr=SHA256:gVWBPJbHGWlCIw+V8F63Ff0k21S7AB5+rZt8+huemvg When a pool's last reference is dropped, __zswap_pool_empty() removes it from the pool list and schedules __zswap_pool_release(), which calls synchronize_rcu() to wait for readers before tearing the pool down. synchronize_rcu() is a synchronous, potentially long wait. Replace it with queue_rcu_work(): __zswap_pool_empty() hands the pool to queue_rcu_work(), which waits for a grace period asynchronously and then runs __zswap_pool_release() from a worker for the sleepable teardown (__zswap_pool_empty() can run in atomic context and must not block). The grace-period guarantee is unchanged; the retirement path just no longer blocks on it. Suggested-by: Yosry Ahmed Signed-off-by: Jianyue Wu Acked-by: Yosry Ahmed --- mm/zswap.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/mm/zswap.c b/mm/zswap.c index f3ae3c81e48e..e456e5080531 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -155,7 +155,7 @@ struct zswap_pool { struct crypto_acomp_ctx __percpu *acomp_ctx; struct percpu_ref ref; struct list_head list; - struct work_struct release_work; + struct rcu_work release_rwork; struct hlist_node node; char tfm_name[CRYPTO_MAX_ALG_NAME]; }; @@ -379,10 +379,8 @@ static void zswap_pool_destroy(struct zswap_pool *pool) static void __zswap_pool_release(struct work_struct *work) { - struct zswap_pool *pool = container_of(work, typeof(*pool), - release_work); - - synchronize_rcu(); + struct zswap_pool *pool = container_of(to_rcu_work(work), + typeof(*pool), release_rwork); /* nobody should have been able to get a ref... */ WARN_ON(!percpu_ref_is_zero(&pool->ref)); @@ -406,8 +404,8 @@ static void __zswap_pool_empty(struct percpu_ref *ref) list_del_rcu(&pool->list); - INIT_WORK(&pool->release_work, __zswap_pool_release); - schedule_work(&pool->release_work); + INIT_RCU_WORK(&pool->release_rwork, __zswap_pool_release); + queue_rcu_work(system_percpu_wq, &pool->release_rwork); spin_unlock_bh(&zswap_pools_lock); } -- 2.43.0