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[94.245.46.61]) by smtp.gmail.com with ESMTPSA id i4sm4338061lfu.33.2021.04.14.05.12.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 Apr 2021 05:12:35 -0700 (PDT) From: "Uladzislau Rezki (Sony)" To: LKML , RCU , "Paul E . McKenney" Cc: Michal Hocko , Andrew Morton , Daniel Axtens , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Peter Zijlstra , Thomas Gleixner , "Theodore Y . Ts'o" , Sebastian Andrzej Siewior , Uladzislau Rezki , Oleksiy Avramchenko Subject: [PATCH 2/6] kvfree_rcu: use [READ/WRITE]_ONCE() macros to access to nr_bkv_objs Date: Wed, 14 Apr 2021 14:12:22 +0200 Message-Id: <20210414121226.2650-2-urezki@gmail.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210414121226.2650-1-urezki@gmail.com> References: <20210414121226.2650-1-urezki@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org nr_bkv_objs represents the counter of objects in the page-cache. Accessing to it requires taking the lock. Switch to READ_ONCE() WRITE_ONCE() macros to provide an atomic access to that counter. A shrinker is one of the user of it. Signed-off-by: Uladzislau Rezki (Sony) --- kernel/rcu/tree.c | 18 ++++++------------ 1 file changed, 6 insertions(+), 12 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 8b74edcd11d4..1b0289fa1cdd 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3220,10 +3220,10 @@ krc_this_cpu_unlock(struct kfree_rcu_cpu *krcp, unsigned long flags) static inline struct kvfree_rcu_bulk_data * get_cached_bnode(struct kfree_rcu_cpu *krcp) { - if (!krcp->nr_bkv_objs) + if (!READ_ONCE(krcp->nr_bkv_objs)) return NULL; - krcp->nr_bkv_objs--; + WRITE_ONCE(krcp->nr_bkv_objs, krcp->nr_bkv_objs - 1); return (struct kvfree_rcu_bulk_data *) llist_del_first(&krcp->bkvcache); } @@ -3233,13 +3233,12 @@ put_cached_bnode(struct kfree_rcu_cpu *krcp, struct kvfree_rcu_bulk_data *bnode) { // Check the limit. - if (krcp->nr_bkv_objs >= rcu_min_cached_objs) + if (READ_ONCE(krcp->nr_bkv_objs) >= rcu_min_cached_objs) return false; llist_add((struct llist_node *) bnode, &krcp->bkvcache); - krcp->nr_bkv_objs++; + WRITE_ONCE(krcp->nr_bkv_objs, krcp->nr_bkv_objs + 1); return true; - } static int @@ -3251,7 +3250,7 @@ drain_page_cache(struct kfree_rcu_cpu *krcp) raw_spin_lock_irqsave(&krcp->lock, flags); page_list = llist_del_all(&krcp->bkvcache); - krcp->nr_bkv_objs = 0; + WRITE_ONCE(krcp->nr_bkv_objs, 0); raw_spin_unlock_irqrestore(&krcp->lock, flags); llist_for_each_safe(pos, n, page_list) { @@ -3655,18 +3654,13 @@ kfree_rcu_shrink_count(struct shrinker *shrink, struct shrink_control *sc) { int cpu; unsigned long count = 0; - unsigned long flags; /* Snapshot count of all CPUs */ for_each_possible_cpu(cpu) { struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu); count += READ_ONCE(krcp->count); - - raw_spin_lock_irqsave(&krcp->lock, flags); - count += krcp->nr_bkv_objs; - raw_spin_unlock_irqrestore(&krcp->lock, flags); - + count += READ_ONCE(krcp->nr_bkv_objs); atomic_set(&krcp->backoff_page_cache_fill, 1); } -- 2.20.1