/* When did we start a new slice */
unsigned long slice_start[2];
unsigned long slice_end[2];
+
+ /* Some throttle limits got updated for the group */
+ bool limits_changed;
};
struct throtl_data
/* Work for dispatching throttled bios */
struct delayed_work throtl_work;
+
+ atomic_t limits_changed;
};
enum tg_state_flags {
min_wait = min(read_wait, write_wait);
disptime = jiffies + min_wait;
- /*
- * If group is already on active tree, then update dispatch time
- * only if it is lesser than existing dispatch time. Otherwise
- * always update the dispatch time
- */
-
- if (throtl_tg_on_rr(tg) && time_before(disptime, tg->disptime))
- return;
-
/* Update dispatch time */
throtl_dequeue_tg(td, tg);
tg->disptime = disptime;
return nr_disp;
}
+static void throtl_process_limit_change(struct throtl_data *td)
+{
+ struct throtl_grp *tg;
+ struct hlist_node *pos, *n;
+
+ /*
+ * Make sure atomic_inc() effects from
+ * throtl_update_blkio_group_read_bps(), group of functions are
+ * visible.
+ * Is this required or smp_mb__after_atomic_inc() was suffcient
+ * after the atomic_inc().
+ */
+ smp_rmb();
+ if (!atomic_read(&td->limits_changed))
+ return;
+
+ throtl_log(td, "limit changed =%d", atomic_read(&td->limits_changed));
+
+ hlist_for_each_entry_safe(tg, pos, n, &td->tg_list, tg_node) {
+ /*
+ * Do I need an smp_rmb() here to make sure tg->limits_changed
+ * update is visible. I am relying on smp_rmb() at the
+ * beginning of function and not putting a new one here.
+ */
+
+ if (throtl_tg_on_rr(tg) && tg->limits_changed) {
+ throtl_log_tg(td, tg, "limit change rbps=%llu wbps=%llu"
+ " riops=%u wiops=%u", tg->bps[READ],
+ tg->bps[WRITE], tg->iops[READ],
+ tg->iops[WRITE]);
+ tg_update_disptime(td, tg);
+ tg->limits_changed = false;
+ }
+ }
+
+ smp_mb__before_atomic_dec();
+ atomic_dec(&td->limits_changed);
+ smp_mb__after_atomic_dec();
+}
+
/* Dispatch throttled bios. Should be called without queue lock held. */
static int throtl_dispatch(struct request_queue *q)
{
spin_lock_irq(q->queue_lock);
+ throtl_process_limit_change(td);
+
if (!total_nr_queued(td))
goto out;
spin_unlock_irqrestore(td->queue->queue_lock, flags);
}
-static void throtl_update_blkio_group_read_bps (struct blkio_group *blkg,
- u64 read_bps)
+/*
+ * For all update functions, key should be a valid pointer because these
+ * update functions are called under blkcg_lock, that means, blkg is
+ * valid and in turn key is valid. queue exit path can not race becuase
+ * of blkcg_lock
+ *
+ * Can not take queue lock in update functions as queue lock under blkcg_lock
+ * is not allowed. Under other paths we take blkcg_lock under queue_lock.
+ */
+static void throtl_update_blkio_group_read_bps(void *key,
+ struct blkio_group *blkg, u64 read_bps)
{
+ struct throtl_data *td = key;
+
tg_of_blkg(blkg)->bps[READ] = read_bps;
+ /* Make sure read_bps is updated before setting limits_changed */
+ smp_wmb();
+ tg_of_blkg(blkg)->limits_changed = true;
+
+ /* Make sure tg->limits_changed is updated before td->limits_changed */
+ smp_mb__before_atomic_inc();
+ atomic_inc(&td->limits_changed);
+ smp_mb__after_atomic_inc();
+
+ /* Schedule a work now to process the limit change */
+ throtl_schedule_delayed_work(td->queue, 0);
}
-static void throtl_update_blkio_group_write_bps (struct blkio_group *blkg,
- u64 write_bps)
+static void throtl_update_blkio_group_write_bps(void *key,
+ struct blkio_group *blkg, u64 write_bps)
{
+ struct throtl_data *td = key;
+
tg_of_blkg(blkg)->bps[WRITE] = write_bps;
+ smp_wmb();
+ tg_of_blkg(blkg)->limits_changed = true;
+ smp_mb__before_atomic_inc();
+ atomic_inc(&td->limits_changed);
+ smp_mb__after_atomic_inc();
+ throtl_schedule_delayed_work(td->queue, 0);
}
-static void throtl_update_blkio_group_read_iops (struct blkio_group *blkg,
- unsigned int read_iops)
+static void throtl_update_blkio_group_read_iops(void *key,
+ struct blkio_group *blkg, unsigned int read_iops)
{
+ struct throtl_data *td = key;
+
tg_of_blkg(blkg)->iops[READ] = read_iops;
+ smp_wmb();
+ tg_of_blkg(blkg)->limits_changed = true;
+ smp_mb__before_atomic_inc();
+ atomic_inc(&td->limits_changed);
+ smp_mb__after_atomic_inc();
+ throtl_schedule_delayed_work(td->queue, 0);
}
-static void throtl_update_blkio_group_write_iops (struct blkio_group *blkg,
- unsigned int write_iops)
+static void throtl_update_blkio_group_write_iops(void *key,
+ struct blkio_group *blkg, unsigned int write_iops)
{
+ struct throtl_data *td = key;
+
tg_of_blkg(blkg)->iops[WRITE] = write_iops;
+ smp_wmb();
+ tg_of_blkg(blkg)->limits_changed = true;
+ smp_mb__before_atomic_inc();
+ atomic_inc(&td->limits_changed);
+ smp_mb__after_atomic_inc();
+ throtl_schedule_delayed_work(td->queue, 0);
}
void throtl_shutdown_timer_wq(struct request_queue *q)
/*
* There is already another bio queued in same dir. No
* need to update dispatch time.
+ * Still update the disptime if rate limits on this group
+ * were changed.
*/
- update_disptime = false;
+ if (!tg->limits_changed)
+ update_disptime = false;
+ else
+ tg->limits_changed = false;
+
goto queue_bio;
}
INIT_HLIST_HEAD(&td->tg_list);
td->tg_service_tree = THROTL_RB_ROOT;
+ atomic_set(&td->limits_changed, 0);
/* Init root group */
tg = &td->root_tg;
*/
if (wait)
synchronize_rcu();
+
+ /*
+ * Just being safe to make sure after previous flush if some body did
+ * update limits through cgroup and another work got queued, cancel
+ * it.
+ */
+ throtl_shutdown_timer_wq(q);
throtl_td_free(td);
}
git://bbs.cooldavid.org / net-next-2.6.git / blobdiff