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block: simplify ioc_release_fn()

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Reverse double lock dancing in ioc_release_fn() can be simplified by
just using trylock on the queue_lock and back out from ioc lock on
trylock failure.  Simplify it.

Signed-off-by: Tejun Heo <tj@kernel.org>
Tested-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Tejun Heo 2012-02-15 09:45:52 +01:00 committed by Jens Axboe
parent d705ae6b13
commit 2274b029f6
1 changed files with 9 additions and 35 deletions
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42
block/blk-ioc.c
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@ -79,7 +79,6 @@ static void ioc_release_fn(struct work_struct *work)
{ {
struct io_context *ioc = container_of(work, struct io_context, struct io_context *ioc = container_of(work, struct io_context,
release_work); release_work);
struct request_queue *last_q = NULL;
unsigned long flags; unsigned long flags;
/* /*
@ -93,44 +92,19 @@ static void ioc_release_fn(struct work_struct *work)
while (!hlist_empty(&ioc->icq_list)) { while (!hlist_empty(&ioc->icq_list)) {
struct io_cq *icq = hlist_entry(ioc->icq_list.first, struct io_cq *icq = hlist_entry(ioc->icq_list.first,
struct io_cq, ioc_node); struct io_cq, ioc_node);
struct request_queue *this_q = icq->q; struct request_queue *q = icq->q;
if (this_q != last_q) { if (spin_trylock(q->queue_lock)) {
/*
* Need to switch to @this_q. Once we release
* @ioc->lock, it can go away along with @cic.
* Hold on to it.
*/
__blk_get_queue(this_q);
/*
* blk_put_queue() might sleep thanks to kobject
* idiocy. Always release both locks, put and
* restart.
*/
if (last_q) {
spin_unlock(last_q->queue_lock);
spin_unlock_irqrestore(&ioc->lock, flags);
blk_put_queue(last_q);
} else {
spin_unlock_irqrestore(&ioc->lock, flags);
}
last_q = this_q;
spin_lock_irqsave(this_q->queue_lock, flags);
spin_lock_nested(&ioc->lock, 1);
continue;
}
ioc_exit_icq(icq); ioc_exit_icq(icq);
} spin_unlock(q->queue_lock);
if (last_q) {
spin_unlock(last_q->queue_lock);
spin_unlock_irqrestore(&ioc->lock, flags);
blk_put_queue(last_q);
} else { } else {
spin_unlock_irqrestore(&ioc->lock, flags); spin_unlock_irqrestore(&ioc->lock, flags);
cpu_relax();
spin_lock_irqsave_nested(&ioc->lock, flags, 1);
} }
}
spin_unlock_irqrestore(&ioc->lock, flags);
kmem_cache_free(iocontext_cachep, ioc); kmem_cache_free(iocontext_cachep, ioc);
} }