Commit d38ecf93 authored by Jens Axboe's avatar Jens Axboe
Browse files

io context sharing: preliminary support 



Detach task state from ioc, instead keep track of how many processes
are accessing the ioc.

Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent fd0928df

block/ll_rw_blk.c

+30 −16
Original line number Diff line number Diff line
@@ -3854,12 +3854,13 @@ int __init blk_dev_init(void) 
}



/*

 * IO Context helper functions

 * IO Context helper functions. put_io_context() returns 1 if there are no

 * more users of this io context, 0 otherwise.

 */

void put_io_context(struct io_context *ioc)

int put_io_context(struct io_context *ioc)

{

	if (ioc == NULL)

		return;

		return 1;



	BUG_ON(atomic_read(&ioc->refcount) == 0);
@@ -3878,7 +3879,9 @@ void put_io_context(struct io_context *ioc) 
		rcu_read_unlock();



		kmem_cache_free(iocontext_cachep, ioc);

		return 1;

	}

	return 0;

}

EXPORT_SYMBOL(put_io_context);
@@ -3893,16 +3896,18 @@ void exit_io_context(void) 
	current->io_context = NULL;

	task_unlock(current);



	ioc->task = NULL;

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

		if (ioc->aic && ioc->aic->exit)

			ioc->aic->exit(ioc->aic);

		if (ioc->cic_root.rb_node != NULL) {

		cic = rb_entry(rb_first(&ioc->cic_root), struct cfq_io_context, rb_node);

			cic = rb_entry(rb_first(&ioc->cic_root),

				struct cfq_io_context, rb_node);

			cic->exit(ioc);

		}



		put_io_context(ioc);

	}

}



struct io_context *alloc_io_context(gfp_t gfp_flags, int node)

{
@@ -3911,7 +3916,8 @@ struct io_context *alloc_io_context(gfp_t gfp_flags, int node) 
	ret = kmem_cache_alloc_node(iocontext_cachep, gfp_flags, node);

	if (ret) {

		atomic_set(&ret->refcount, 1);

		ret->task = current;

		atomic_set(&ret->nr_tasks, 1);

		spin_lock_init(&ret->lock);

		ret->ioprio_changed = 0;

		ret->ioprio = 0;

		ret->last_waited = jiffies; /* doesn't matter... */
@@ -3959,10 +3965,18 @@ static struct io_context *current_io_context(gfp_t gfp_flags, int node) 
 */

struct io_context *get_io_context(gfp_t gfp_flags, int node)

{

	struct io_context *ret;

	struct io_context *ret = NULL;



	/*

	 * Check for unlikely race with exiting task. ioc ref count is

	 * zero when ioc is being detached.

	 */

	do {

		ret = current_io_context(gfp_flags, node);

	if (likely(ret))

		atomic_inc(&ret->refcount);

		if (unlikely(!ret))

			break;

	} while (!atomic_inc_not_zero(&ret->refcount));



	return ret;

}

EXPORT_SYMBOL(get_io_context);

fs/ioprio.c

+0 −1
Original line number Diff line number Diff line
@@ -54,7 +54,6 @@ static int set_task_ioprio(struct task_struct *task, int ioprio) 
			break;

		}

		task->io_context = ioc;

		ioc->task = task;

	} while (1);



	if (!err) {

include/linux/blkdev.h

+1 −1
Original line number Diff line number Diff line
@@ -34,7 +34,7 @@ struct sg_io_hdr; 
#define BLKDEV_MIN_RQ	4

#define BLKDEV_MAX_RQ	128	/* Default maximum */



void put_io_context(struct io_context *ioc);

int put_io_context(struct io_context *ioc);

void exit_io_context(void);

struct io_context *get_io_context(gfp_t gfp_flags, int node);

struct io_context *alloc_io_context(gfp_t gfp_flags, int node);

include/linux/iocontext.h

+18 −4
Original line number Diff line number Diff line
@@ -54,13 +54,15 @@ struct cfq_io_context { 
};



/*

 * This is the per-process I/O subsystem state.  It is refcounted and

 * kmalloc'ed. Currently all fields are modified in process io context

 * (apart from the atomic refcount), so require no locking.

 * I/O subsystem state of the associated processes.  It is refcounted

 * and kmalloc'ed. These could be shared between processes.

 */

struct io_context {

	atomic_t refcount;

	struct task_struct *task;

	atomic_t nr_tasks;



	/* all the fields below are protected by this lock */

	spinlock_t lock;



	unsigned short ioprio;

	unsigned short ioprio_changed;
@@ -76,4 +78,16 @@ struct io_context { 
	void *ioc_data;

};



static inline struct io_context *ioc_task_link(struct io_context *ioc)

{

	/*

	 * if ref count is zero, don't allow sharing (ioc is going away, it's

	 * a race).

	 */

	if (ioc && atomic_inc_not_zero(&ioc->refcount))

		return ioc;



	return NULL;

}



#endif

kernel/fork.c

+0 −1
Original line number Diff line number Diff line
@@ -805,7 +805,6 @@ static int copy_io(struct task_struct *tsk) 
		if (unlikely(!tsk->io_context))

			return -ENOMEM;



		tsk->io_context->task = tsk;

		tsk->io_context->ioprio = ioc->ioprio;

	}

#endif