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McKenney" , "Rafael J. Wysocki" , rcu@vger.kernel.org, Steven Rostedt , "Uladzislau Rezki (Sony)" Subject: [PATCH 18/18] rcu/tree: Make kvfree_rcu() tolerate any alignment Date: Sun, 29 Mar 2020 22:32:48 -0400 Message-Id: <20200330023248.164994-19-joel@joelfernandes.org> X-Mailer: git-send-email 2.26.0.rc2.310.g2932bb562d-goog In-Reply-To: <20200330023248.164994-1-joel@joelfernandes.org> References: <20200330023248.164994-1-joel@joelfernandes.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Handle cases where the the object being kvfree_rcu()'d is not aligned by 2-byte boundaries. Signed-off-by: Joel Fernandes (Google) --- kernel/rcu/tree.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 311d216c7faa7..d6536374d12a9 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2827,6 +2827,9 @@ struct kvfree_rcu_bulk_data { #define KVFREE_BULK_MAX_ENTR \ ((PAGE_SIZE - sizeof(struct kvfree_rcu_bulk_data)) / sizeof(void *)) =20 +/* Encoding the offset of a fake rcu_head to indicate the head is a wrap= per. */ +#define RCU_HEADLESS_KFREE BIT(31) + /** * struct kfree_rcu_cpu_work - single batch of kfree_rcu() requests * @rcu_work: Let queue_rcu_work() invoke workqueue handler after grace = period @@ -2970,9 +2973,9 @@ static void kfree_rcu_work(struct work_struct *work= ) next =3D head->next; =20 /* We tag the headless object, if so adjust offset. */ - headless =3D (((unsigned long) head - offset) & BIT(0)); + headless =3D !!(offset & RCU_HEADLESS_KFREE); if (headless) - offset -=3D 1; + offset &=3D ~(RCU_HEADLESS_KFREE); =20 ptr =3D (void *) head - offset; debug_rcu_head_unqueue((struct rcu_head *)ptr); @@ -3221,7 +3224,7 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_cal= lback_t func) * to the original allocated memory, that has to be freed as * well as dynamically attached wrapper/head. */ - func =3D (rcu_callback_t) (sizeof(unsigned long *) + 1); + func =3D (rcu_callback_t)(sizeof(unsigned long *) | RCU_HEADLESS_KFRE= E); } =20 head->func =3D func; --=20 2.26.0.rc2.310.g2932bb562d-goog