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From:   "Uladzislau Rezki (Sony)" <urezki@gmail.com>
To:     LKML <linux-kernel@vger.kernel.org>, linux-mm@kvack.org
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        "Paul E . McKenney" <paulmck@kernel.org>,
        "Theodore Y . Ts'o" <tytso@mit.edu>,
        Matthew Wilcox <willy@infradead.org>,
        Joel Fernandes <joel@joelfernandes.org>,
        RCU <rcu@vger.kernel.org>, Uladzislau Rezki <urezki@gmail.com>,
        Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>,
        Boqun Feng <boqun.feng@gmail.com>
Subject: [PATCH 06/24] rcu/tree: Simplify KFREE_BULK_MAX_ENTR macro
Date:   Tue, 28 Apr 2020 22:58:45 +0200
Message-Id: <20200428205903.61704-7-urezki@gmail.com>
In-Reply-To: <20200428205903.61704-1-urezki@gmail.com>
References: <20200428205903.61704-1-urezki@gmail.com>
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We can simplify KFREE_BULK_MAX_ENTR macro and get rid of
magic numbers which were used to make the structure to be
exactly one page.

Suggested-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 kernel/rcu/tree.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 767aed49d7fd..eebd7f627794 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2848,13 +2848,6 @@ EXPORT_SYMBOL_GPL(call_rcu);
 #define KFREE_DRAIN_JIFFIES (HZ / 50)
 #define KFREE_N_BATCHES 2
 
-/*
- * This macro defines how many entries the "records" array
- * will contain. It is based on the fact that the size of
- * kfree_rcu_bulk_data structure becomes exactly one page.
- */
-#define KFREE_BULK_MAX_ENTR ((PAGE_SIZE / sizeof(void *)) - 3)
-
 /**
  * struct kfree_rcu_bulk_data - single block to store kfree_rcu() pointers
  * @nr_records: Number of active pointers in the array
@@ -2863,10 +2856,18 @@ EXPORT_SYMBOL_GPL(call_rcu);
  */
 struct kfree_rcu_bulk_data {
 	unsigned long nr_records;
-	void *records[KFREE_BULK_MAX_ENTR];
 	struct kfree_rcu_bulk_data *next;
+	void *records[];
 };
 
+/*
+ * This macro defines how many entries the "records" array
+ * will contain. It is based on the fact that the size of
+ * kfree_rcu_bulk_data structure becomes exactly one page.
+ */
+#define KFREE_BULK_MAX_ENTR \
+	((PAGE_SIZE - sizeof(struct kfree_rcu_bulk_data)) / sizeof(void *))
+
 /**
  * struct kfree_rcu_cpu_work - single batch of kfree_rcu() requests
  * @rcu_work: Let queue_rcu_work() invoke workqueue handler after grace period
-- 
2.20.1