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authorTejun Heo <tj@kernel.org>2011-10-19 14:33:01 +0200
committerJens Axboe <axboe@kernel.dk>2011-10-19 14:33:01 +0200
commitbc16a4f933bc5ed50826b20561e4c3515061998b (patch)
tree07c0dc65408932176c32df08e7a8adbbc2ca1d07 /block/blk-throttle.c
parente3c78ca524d230bc145e902625e88c392a58ddf3 (diff)
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>
Diffstat (limited to 'block/blk-throttle.c')
-rw-r--r--block/blk-throttle.c49
1 files changed, 17 insertions, 32 deletions
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index ecba5fcef201..900a0c98745b 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -303,10 +303,6 @@ throtl_grp *throtl_find_tg(struct throtl_data *td, struct blkio_cgroup *blkcg)
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 @@ static struct throtl_grp * throtl_get_tg(struct throtl_data *td)
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 @@ static struct blkio_policy_type blkio_policy_throtl = {
.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 @@ int blk_throtl_bio(struct request_queue *q, struct bio **biop)
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 @@ int blk_throtl_bio(struct request_queue *q, struct bio **biop)
* 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 @@ int blk_throtl_bio(struct request_queue *q, struct bio **biop)
* 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 @@ queue_bio:
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)