block: reorganize throtl_get_tg() and blk_throtl_bio()
blk_throtl_bio() and throtl_get_tg() have rather unusual interface.
* throtl_get_tg() returns pointer to a valid tg or ERR_PTR(-ENODEV),
and drops queue_lock in the latter case. Different locking context
depending on return value is error-prone and DEAD state is scheduled
to be protected by queue_lock anyway. Move DEAD check inside
queue_lock and return valid tg or NULL.
* blk_throtl_bio() indicates return status both with its return value
and in/out param **@bio. The former is used to indicate whether
queue is found to be dead during throtl processing. The latter
whether the bio is throttled.
There's no point in returning DEAD check result from
blk_throtl_bio(). The queue can die after blk_throtl_bio() is
finished but before make_request_fn() grabs queue lock.
Make it take *@bio instead and return boolean result indicating
whether the request is throttled or not.
This patch doesn't cause any visible functional difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index ecba5fc..900a0c9 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -303,10 +303,6 @@
return tg;
}
-/*
- * This function returns with queue lock unlocked in case of error, like
- * request queue is no more
- */
static struct throtl_grp * throtl_get_tg(struct throtl_data *td)
{
struct throtl_grp *tg = NULL, *__tg = NULL;
@@ -330,20 +326,16 @@
spin_unlock_irq(q->queue_lock);
tg = throtl_alloc_tg(td);
- /*
- * We might have slept in group allocation. Make sure queue is not
- * dead
- */
- if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) {
- if (tg)
- kfree(tg);
-
- return ERR_PTR(-ENODEV);
- }
/* Group allocated and queue is still alive. take the lock */
spin_lock_irq(q->queue_lock);
+ /* Make sure @q is still alive */
+ if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) {
+ kfree(tg);
+ return NULL;
+ }
+
/*
* Initialize the new group. After sleeping, read the blkcg again.
*/
@@ -1118,17 +1110,17 @@
.plid = BLKIO_POLICY_THROTL,
};
-int blk_throtl_bio(struct request_queue *q, struct bio **biop)
+bool blk_throtl_bio(struct request_queue *q, struct bio *bio)
{
struct throtl_data *td = q->td;
struct throtl_grp *tg;
- struct bio *bio = *biop;
bool rw = bio_data_dir(bio), update_disptime = true;
struct blkio_cgroup *blkcg;
+ bool throttled = false;
if (bio->bi_rw & REQ_THROTTLED) {
bio->bi_rw &= ~REQ_THROTTLED;
- return 0;
+ goto out;
}
/*
@@ -1147,7 +1139,7 @@
blkiocg_update_dispatch_stats(&tg->blkg, bio->bi_size,
rw, rw_is_sync(bio->bi_rw));
rcu_read_unlock();
- return 0;
+ goto out;
}
}
rcu_read_unlock();
@@ -1156,18 +1148,10 @@
* Either group has not been allocated yet or it is not an unlimited
* IO group
*/
-
spin_lock_irq(q->queue_lock);
tg = throtl_get_tg(td);
-
- if (IS_ERR(tg)) {
- if (PTR_ERR(tg) == -ENODEV) {
- /*
- * Queue is gone. No queue lock held here.
- */
- return -ENODEV;
- }
- }
+ if (unlikely(!tg))
+ goto out_unlock;
if (tg->nr_queued[rw]) {
/*
@@ -1195,7 +1179,7 @@
* So keep on trimming slice even if bio is not queued.
*/
throtl_trim_slice(td, tg, rw);
- goto out;
+ goto out_unlock;
}
queue_bio:
@@ -1207,16 +1191,17 @@
tg->nr_queued[READ], tg->nr_queued[WRITE]);
throtl_add_bio_tg(q->td, tg, bio);
- *biop = NULL;
+ throttled = true;
if (update_disptime) {
tg_update_disptime(td, tg);
throtl_schedule_next_dispatch(td);
}
-out:
+out_unlock:
spin_unlock_irq(q->queue_lock);
- return 0;
+out:
+ return throttled;
}
int blk_throtl_init(struct request_queue *q)