Commit f6e8d01b authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

block: add io_context->active_ref 



Currently ioc->nr_tasks is used to decide two things - whether an ioc
is done issuing IOs and whether it's shared by multiple tasks.  This
patch separate out the first into ioc->active_ref, which is acquired
and released using {get|put}_io_context_active() respectively.

This will be used to associate bio's with a given task.  This patch
doesn't introduce any visible behavior change.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 3d48749d

block/blk-ioc.c

+25 −11
Original line number Diff line number Diff line
@@ -149,20 +149,20 @@ void put_io_context(struct io_context *ioc) 
}

EXPORT_SYMBOL(put_io_context);



/* Called by the exiting task */

void exit_io_context(struct task_struct *task)

/**

 * put_io_context_active - put active reference on ioc

 * @ioc: ioc of interest

 *

 * Undo get_io_context_active().  If active reference reaches zero after

 * put, @ioc can never issue further IOs and ioscheds are notified.

 */

void put_io_context_active(struct io_context *ioc)

{

	struct io_context *ioc;

	struct io_cq *icq;

	struct hlist_node *n;

	unsigned long flags;

	struct io_cq *icq;



	task_lock(task);

	ioc = task->io_context;

	task->io_context = NULL;

	task_unlock(task);



	if (!atomic_dec_and_test(&ioc->nr_tasks)) {

	if (!atomic_dec_and_test(&ioc->active_ref)) {

		put_io_context(ioc);

		return;

	}
@@ -191,6 +191,20 @@ retry: 
	put_io_context(ioc);

}



/* Called by the exiting task */

void exit_io_context(struct task_struct *task)

{

	struct io_context *ioc;



	task_lock(task);

	ioc = task->io_context;

	task->io_context = NULL;

	task_unlock(task);



	atomic_dec(&ioc->nr_tasks);

	put_io_context_active(ioc);

}



/**

 * ioc_clear_queue - break any ioc association with the specified queue

 * @q: request_queue being cleared
@@ -223,7 +237,7 @@ int create_task_io_context(struct task_struct *task, gfp_t gfp_flags, int node) 


	/* initialize */

	atomic_long_set(&ioc->refcount, 1);

	atomic_set(&ioc->nr_tasks, 1);

	atomic_set(&ioc->active_ref, 1);

	spin_lock_init(&ioc->lock);

	INIT_RADIX_TREE(&ioc->icq_tree, GFP_ATOMIC | __GFP_HIGH);

	INIT_HLIST_HEAD(&ioc->icq_list);

block/cfq-iosched.c

+2 −2
Original line number Diff line number Diff line
@@ -1865,7 +1865,7 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd) 
	 * task has exited, don't wait

	 */

	cic = cfqd->active_cic;

	if (!cic || !atomic_read(&cic->icq.ioc->nr_tasks))

	if (!cic || !atomic_read(&cic->icq.ioc->active_ref))

		return;



	/*
@@ -2841,7 +2841,7 @@ cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq, 


	if (cfqq->next_rq && (cfqq->next_rq->cmd_flags & REQ_NOIDLE))

		enable_idle = 0;

	else if (!atomic_read(&cic->icq.ioc->nr_tasks) ||

	else if (!atomic_read(&cic->icq.ioc->active_ref) ||

		 !cfqd->cfq_slice_idle ||

		 (!cfq_cfqq_deep(cfqq) && CFQQ_SEEKY(cfqq)))

		enable_idle = 0;

include/linux/iocontext.h

+20 −2
Original line number Diff line number Diff line
@@ -100,6 +100,7 @@ struct io_cq { 
 */

struct io_context {

	atomic_long_t refcount;

	atomic_t active_ref;

	atomic_t nr_tasks;



	/* all the fields below are protected by this lock */
@@ -120,17 +121,34 @@ struct io_context { 
	struct work_struct release_work;

};



static inline void ioc_task_link(struct io_context *ioc)

/**

 * get_io_context_active - get active reference on ioc

 * @ioc: ioc of interest

 *

 * Only iocs with active reference can issue new IOs.  This function

 * acquires an active reference on @ioc.  The caller must already have an

 * active reference on @ioc.

 */

static inline void get_io_context_active(struct io_context *ioc)

{

	WARN_ON_ONCE(atomic_long_read(&ioc->refcount) <= 0);

	WARN_ON_ONCE(atomic_read(&ioc->nr_tasks) <= 0);

	WARN_ON_ONCE(atomic_read(&ioc->active_ref) <= 0);

	atomic_long_inc(&ioc->refcount);

	atomic_inc(&ioc->active_ref);

}



static inline void ioc_task_link(struct io_context *ioc)

{

	get_io_context_active(ioc);



	WARN_ON_ONCE(atomic_read(&ioc->nr_tasks) <= 0);

	atomic_inc(&ioc->nr_tasks);

}



struct task_struct;

#ifdef CONFIG_BLOCK

void put_io_context(struct io_context *ioc);

void put_io_context_active(struct io_context *ioc);

void exit_io_context(struct task_struct *task);

struct io_context *get_task_io_context(struct task_struct *task,

				       gfp_t gfp_flags, int node);

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