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block: defer timeouts to a workqueue

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Timer context is not very useful for drivers to perform any meaningful abort
action from.  So instead of calling the driver from this useless context
defer it to a workqueue as soon as possible.

Note that while a delayed_work item would seem the right thing here I didn't
dare to use it due to the magic in blk_add_timer that pokes deep into timer
internals.  But maybe this encourages Tejun to add a sensible API for that to
the workqueue API and we'll all be fine in the end :)

Contains a major update from Keith Bush:

"This patch removes synchronizing the timeout work so that the timer can
 start a freeze on its own queue. The timer enters the queue, so timer
 context can only start a freeze, but not wait for frozen."

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Christoph Hellwig
2015-10-30 20:57:30 +08:00
committed by Jens Axboe
parent 8c0b391550
commit 287922eb0b
5 changed files with 24 additions and 6 deletions
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8
block/blk-core.c
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@@ -664,6 +664,13 @@ static void blk_queue_usage_counter_release(struct percpu_ref *ref)
wake_up_all(&q->mq_freeze_wq);
}
static void blk_rq_timed_out_timer(unsigned long data)
{
struct request_queue *q = (struct request_queue *)data;
kblockd_schedule_work(&q->timeout_work);
}
struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
{
struct request_queue *q;
@@ -825,6 +832,7 @@ blk_init_allocated_queue(struct request_queue *q, request_fn_proc *rfn,
if (blk_init_rl(&q->root_rl, q, GFP_KERNEL))
goto fail;
INIT_WORK(&q->timeout_work, blk_timeout_work);
q->request_fn = rfn;
q->prep_rq_fn = NULL;
q->unprep_rq_fn = NULL;