--- block/cfq-iosched.c

+++ block/cfq-iosched.c

@@ -1680,7 +1680,6 @@ static void changed_ioprio(struct io_con

static void cfq_ioc_set_ioprio(struct io_context *ioc)

{

call_for_each_cic(ioc, changed_ioprio);

- ioc->ioprio_changed = 0;

}

static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,

@@ -1928,8 +1927,13 @@ cfq_get_io_context(struct cfq_data *cfqd

goto err_free;

out:

- smp_read_barrier_depends();

- if (unlikely(ioc->ioprio_changed))

+ /*

+ * test_and_clear_bit() implies a memory barrier, paired with

+ * the wmb() in fs/ioprio.c, so the value seen for ioprio is the

+ * new one.

+ */

+ if (unlikely(test_and_clear_bit(IOC_CFQ_IOPRIO_CHANGED,

+ ioc->ioprio_changed)))

cfq_ioc_set_ioprio(ioc);

return cic;