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block: extend queue bypassing to cover blkcg policies 

Extend queue bypassing such that dying queue is always bypassing and
blk-throttle is drained on bypass.  With blkcg policies updated to
test blk_queue_bypass() instead of blk_queue_dead(), this ensures that
no bio or request is held by or going through blkcg policies on a
bypassing queue.

This will be used to implement blkg cleanup on elevator switches and
policy changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Tejun Heo 2012-03-05 13:14:59 -08:00 committed by Jens Axboe
parent d732580b4e
commit 6ecf23afab
2 changed files with 10 additions and 6 deletions
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12
block/blk-core.c
View File

@ -372,8 +372,7 @@ void blk_drain_queue(struct request_queue *q, bool drain_all)
if (q->elevator)
elv_drain_elevator(q);
if (drain_all)
blk_throtl_drain(q);
blk_throtl_drain(q);
/*
* This function might be called on a queue which failed
@ -415,8 +414,8 @@ void blk_drain_queue(struct request_queue *q, bool drain_all)
*
* In bypass mode, only the dispatch FIFO queue of @q is used. This
* function makes @q enter bypass mode and drains all requests which were
* issued before. On return, it's guaranteed that no request has ELVPRIV
* set.
* throttled or issued before. On return, it's guaranteed that no request
* is being throttled or has ELVPRIV set.
*/
void blk_queue_bypass_start(struct request_queue *q)
{
@ -461,6 +460,11 @@ void blk_cleanup_queue(struct request_queue *q)
queue_flag_set_unlocked(QUEUE_FLAG_DEAD, q);
spin_lock_irq(lock);
/* dead queue is permanently in bypass mode till released */
q->bypass_depth++;
queue_flag_set(QUEUE_FLAG_BYPASS, q);
queue_flag_set(QUEUE_FLAG_NOMERGES, q);
queue_flag_set(QUEUE_FLAG_NOXMERGES, q);
queue_flag_set(QUEUE_FLAG_DEAD, q);

4
block/blk-throttle.c
View File

@ -310,7 +310,7 @@ static struct throtl_grp * throtl_get_tg(struct throtl_data *td)
struct request_queue *q = td->queue;
/* no throttling for dead queue */
if (unlikely(blk_queue_dead(q)))
if (unlikely(blk_queue_bypass(q)))
return NULL;
rcu_read_lock();
@ -335,7 +335,7 @@ static struct throtl_grp * throtl_get_tg(struct throtl_data *td)
spin_lock_irq(q->queue_lock);
/* Make sure @q is still alive */
if (unlikely(blk_queue_dead(q))) {
if (unlikely(blk_queue_bypass(q))) {
kfree(tg);
return NULL;
}