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block, cfq: move ioc ioprio/cgroup changed handling to cic

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ioprio/cgroup change was handled by marking the changed state in ioc
and, on the following access to the ioc, performing RCU-protected
iteration through all cic's grabbing the matching queue_lock.

This patch moves the changed state to each cic.  When ioprio or cgroup
changes, the respective bit is set on all cic's of the ioc and when
each of those cic (not ioc) is accessed, change is applied for that
specific ioc-queue pair.

This also fixes the following two race conditions between setting and
clearing of changed states.

* Missing barrier between assign/load of ioprio and ioprio_changed
  allowed applying old ioprio.

* Change requests could happen between application of change and
  clearing of changed variables.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Tejun Heo
2011-12-14 00:33:38 +01:00
committed by Jens Axboe
parent 283287a52e
commit dc86900e0a
5 changed files with 65 additions and 27 deletions
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block/cfq-iosched.c
+9 -19
View File
@@ -2904,7 +2904,7 @@ static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
cfq_clear_cfqq_prio_changed(cfqq);
}
static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
static void changed_ioprio(struct cfq_io_context *cic)
{
struct cfq_data *cfqd = cic_to_cfqd(cic);
struct cfq_queue *cfqq;
@@ -2933,12 +2933,6 @@ static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
}
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,
pid_t pid, bool is_sync)
{
@@ -2960,7 +2954,7 @@ static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
}
#ifdef CONFIG_CFQ_GROUP_IOSCHED
static void changed_cgroup(struct io_context *ioc, struct cfq_io_context *cic)
static void changed_cgroup(struct cfq_io_context *cic)
{
struct cfq_queue *sync_cfqq = cic_to_cfqq(cic, 1);
struct cfq_data *cfqd = cic_to_cfqd(cic);
@@ -2986,12 +2980,6 @@ static void changed_cgroup(struct io_context *ioc, struct cfq_io_context *cic)
spin_unlock_irqrestore(q->queue_lock, flags);
}
static void cfq_ioc_set_cgroup(struct io_context *ioc)
{
call_for_each_cic(ioc, changed_cgroup);
ioc->cgroup_changed = 0;
}
#endif /* CONFIG_CFQ_GROUP_IOSCHED */
static struct cfq_queue *
@@ -3222,13 +3210,15 @@ cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
out:
get_io_context(ioc);
if (unlikely(ioc->ioprio_changed))
cfq_ioc_set_ioprio(ioc);
if (unlikely(cic->changed)) {
if (test_and_clear_bit(CIC_IOPRIO_CHANGED, &cic->changed))
changed_ioprio(cic);
#ifdef CONFIG_CFQ_GROUP_IOSCHED
if (unlikely(ioc->cgroup_changed))
cfq_ioc_set_cgroup(ioc);
if (test_and_clear_bit(CIC_CGROUP_CHANGED, &cic->changed))
changed_cgroup(cic);
#endif
}
return cic;
err:
if (cic)