block: strip out locking optimization in put_io_context() (11a3122f) · Commits · 戴 / test

block/blk-cgroup.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1659,7 +1659,7 @@ static void blkiocg_attach(struct cgroup_subsys ss, struct cgroup cgrp,
		ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE);
		if (ioc) {
		ioc_cgroup_changed(ioc);
		put_io_context(ioc, NULL);
		put_io_context(ioc);
		}
		}
		}

block/blk-core.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -642,7 +642,7 @@ static inline void blk_free_request(struct request_queue q, struct request rq)
		if (rq->cmd_flags & REQ_ELVPRIV) {
		elv_put_request(q, rq);
		if (rq->elv.icq)
		put_io_context(rq->elv.icq->ioc, q);
		put_io_context(rq->elv.icq->ioc);
		}

		mempool_free(rq, q->rq.rq_pool);

block/blk-ioc.c

+11 −81

Original line number	Diff line number	Diff line
		@@ -29,21 +29,6 @@ void get_io_context(struct io_context *ioc)
		}
		EXPORT_SYMBOL(get_io_context);

		/*
		* Releasing ioc may nest into another put_io_context() leading to nested
		* fast path release. As the ioc's can't be the same, this is okay but
		* makes lockdep whine. Keep track of nesting and use it as subclass.
		*/
		#ifdef CONFIG_LOCKDEP
		#define ioc_release_depth(q) ((q) ? (q)->ioc_release_depth : 0)
		#define ioc_release_depth_inc(q) (q)->ioc_release_depth++
		#define ioc_release_depth_dec(q) (q)->ioc_release_depth--
		#else
		#define ioc_release_depth(q) 0
		#define ioc_release_depth_inc(q) do { } while (0)
		#define ioc_release_depth_dec(q) do { } while (0)
		#endif

		static void icq_free_icq_rcu(struct rcu_head *head)
		{
		struct io_cq *icq = container_of(head, struct io_cq, __rcu_head);
		@@ -75,11 +60,8 @@ static void ioc_exit_icq(struct io_cq *icq)
		if (rcu_dereference_raw(ioc->icq_hint) == icq)
		rcu_assign_pointer(ioc->icq_hint, NULL);

		if (et->ops.elevator_exit_icq_fn) {
		ioc_release_depth_inc(q);
		if (et->ops.elevator_exit_icq_fn)
		et->ops.elevator_exit_icq_fn(icq);
		ioc_release_depth_dec(q);
		}

		/*
		* @icq->q might have gone away by the time RCU callback runs
		@@ -149,81 +131,29 @@ static void ioc_release_fn(struct work_struct *work)
		/**
		* put_io_context - put a reference of io_context
		* @ioc: io_context to put
		* @locked_q: request_queue the caller is holding queue_lock of (hint)
		*
		* Decrement reference count of @ioc and release it if the count reaches
		* zero. If the caller is holding queue_lock of a queue, it can indicate
		* that with @locked_q. This is an optimization hint and the caller is
		* allowed to pass in %NULL even when it's holding a queue_lock.
		* zero.
		*/
		void put_io_context(struct io_context ioc, struct request_queue locked_q)
		void put_io_context(struct io_context *ioc)
		{
		struct request_queue *last_q = locked_q;
		unsigned long flags;

		if (ioc == NULL)
		return;

		BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
		if (locked_q)
		lockdep_assert_held(locked_q->queue_lock);

		if (!atomic_long_dec_and_test(&ioc->refcount))
		return;

		/*
		* Destroy @ioc. This is a bit messy because icq's are chained
		* from both ioc and queue, and ioc->lock nests inside queue_lock.
		* The inner ioc->lock should be held to walk our icq_list and then
		* for each icq the outer matching queue_lock should be grabbed.
		* ie. We need to do reverse-order double lock dancing.
		*
		* Another twist is that we are often called with one of the
		* matching queue_locks held as indicated by @locked_q, which
		* prevents performing double-lock dance for other queues.
		*
		* So, we do it in two stages. The fast path uses the queue_lock
		* the caller is holding and, if other queues need to be accessed,
		* uses trylock to avoid introducing locking dependency. This can
		* handle most cases, especially if @ioc was performing IO on only
		* single device.
		*
		* If trylock doesn't cut it, we defer to @ioc->release_work which
		* can do all the double-locking dancing.
		* Releasing ioc requires reverse order double locking and we may
		* already be holding a queue_lock. Do it asynchronously from wq.
		*/
		spin_lock_irqsave_nested(&ioc->lock, flags,
		ioc_release_depth(locked_q));

		while (!hlist_empty(&ioc->icq_list)) {
		struct io_cq *icq = hlist_entry(ioc->icq_list.first,
		struct io_cq, ioc_node);
		struct request_queue *this_q = icq->q;

		if (this_q != last_q) {
		if (last_q && last_q != locked_q)
		spin_unlock(last_q->queue_lock);
		last_q = NULL;

		/* spin_trylock() always successes in UP case */
		if (this_q != locked_q &&
		!spin_trylock(this_q->queue_lock))
		break;
		last_q = this_q;
		continue;
		}
		ioc_exit_icq(icq);
		}

		if (last_q && last_q != locked_q)
		spin_unlock(last_q->queue_lock);

		spin_unlock_irqrestore(&ioc->lock, flags);

		/* if no icq is left, we're done; otherwise, kick release_work */
		if (hlist_empty(&ioc->icq_list))
		kmem_cache_free(iocontext_cachep, ioc);
		else
		if (atomic_long_dec_and_test(&ioc->refcount)) {
		spin_lock_irqsave(&ioc->lock, flags);
		if (!hlist_empty(&ioc->icq_list))
		schedule_work(&ioc->release_work);
		spin_unlock_irqrestore(&ioc->lock, flags);
		}
		}
		EXPORT_SYMBOL(put_io_context);

		@@ -238,7 +168,7 @@ void exit_io_context(struct task_struct *task)
		task_unlock(task);

		atomic_dec(&ioc->nr_tasks);
		put_io_context(ioc, NULL);
		put_io_context(ioc);
		}

		/**

block/cfq-iosched.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1794,7 +1794,7 @@ __cfq_slice_expired(struct cfq_data cfqd, struct cfq_queue cfqq,
		cfqd->active_queue = NULL;

		if (cfqd->active_cic) {
		put_io_context(cfqd->active_cic->icq.ioc, cfqd->queue);
		put_io_context(cfqd->active_cic->icq.ioc);
		cfqd->active_cic = NULL;
		}
		}

fs/ioprio.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -51,7 +51,7 @@ int set_task_ioprio(struct task_struct *task, int ioprio)
		ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE);
		if (ioc) {
		ioc_ioprio_changed(ioc, ioprio);
		put_io_context(ioc, NULL);
		put_io_context(ioc);
		}

		return err;

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