cfq-iosched: fix RCU problem in cfq_cic_lookup() (d6de8be7) · Commits · 戴 / test

block/cfq-iosched.c

+26 −2

Original line number	Diff line number	Diff line
		@@ -1142,6 +1142,9 @@ static void cfq_put_queue(struct cfq_queue *cfqq)
		kmem_cache_free(cfq_pool, cfqq);
		}

		/*
		* Must always be called with the rcu_read_lock() held
		*/
		static void
		__call_for_each_cic(struct io_context *ioc,
		void (func)(struct io_context , struct cfq_io_context *))
		@@ -1197,6 +1200,11 @@ static void cic_free_func(struct io_context ioc, struct cfq_io_context cic)
		cfq_cic_free(cic);
		}

		/*
		* Must be called with rcu_read_lock() held or preemption otherwise disabled.
		* Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
		* and ->trim() which is called with the task lock held
		*/
		static void cfq_free_io_context(struct io_context *ioc)
		{
		/*
		@@ -1502,20 +1510,24 @@ static struct cfq_io_context *
		cfq_cic_lookup(struct cfq_data cfqd, struct io_context ioc)
		{
		struct cfq_io_context *cic;
		unsigned long flags;
		void *k;

		if (unlikely(!ioc))
		return NULL;

		rcu_read_lock();

		/*
		* we maintain a last-hit cache, to avoid browsing over the tree
		*/
		cic = rcu_dereference(ioc->ioc_data);
		if (cic && cic->key == cfqd)
		if (cic && cic->key == cfqd) {
		rcu_read_unlock();
		return cic;
		}

		do {
		rcu_read_lock();
		cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd);
		rcu_read_unlock();
		if (!cic)
		@@ -1524,10 +1536,13 @@ cfq_cic_lookup(struct cfq_data cfqd, struct io_context ioc)
		k = cic->key;
		if (unlikely(!k)) {
		cfq_drop_dead_cic(cfqd, ioc, cic);
		rcu_read_lock();
		continue;
		}

		spin_lock_irqsave(&ioc->lock, flags);
		rcu_assign_pointer(ioc->ioc_data, cic);
		spin_unlock_irqrestore(&ioc->lock, flags);
		break;
		} while (1);

		@@ -2134,6 +2149,10 @@ static void cfq_init_queue(struct request_queue q)

		static void cfq_slab_kill(void)
		{
		/*
		* Caller already ensured that pending RCU callbacks are completed,
		* so we should have no busy allocations at this point.
		*/
		if (cfq_pool)
		kmem_cache_destroy(cfq_pool);
		if (cfq_ioc_pool)
		@@ -2292,6 +2311,11 @@ static void __exit cfq_exit(void)
		ioc_gone = &all_gone;
		/* ioc_gone's update must be visible before reading ioc_count */
		smp_wmb();

		/*
		* this also protects us from entering cfq_slab_kill() with
		* pending RCU callbacks
		*/
		if (elv_ioc_count_read(ioc_count))
		wait_for_completion(ioc_gone);
		cfq_slab_kill();

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