block: introduce the BFQ-v6r2 I/O sched for 3.3

/*

 * BFQ: I/O context handling.

 *

 * Based on ideas and code from CFQ:

 * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>

 *

 * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>

 *		      Paolo Valente <paolo.valente@unimore.it>

 *

 * Copyright (C) 2010 Paolo Valente <paolo.valente@unimore.it>

 */

/**

 * icq_to_bic - convert iocontext queue structure to bfq_io_cq.

 * @icq: the iocontext queue.

 */

static inline struct bfq_io_cq *icq_to_bic(struct io_cq *icq)

{

	/* bic->icq is the first member, %NULL will convert to %NULL */

	return container_of(icq, struct bfq_io_cq, icq);

}

/**

 * bfq_bic_lookup - search into @ioc a bic associated to @bfqd.

 * @bfqd: the lookup key.

 * @ioc: the io_context of the process doing I/O.

 *

 * Queue lock must be held.

 */

static inline struct bfq_io_cq *bfq_bic_lookup(struct bfq_data *bfqd,

					       struct io_context *ioc)

{

	if(ioc)

		return icq_to_bic(ioc_lookup_icq(ioc, bfqd->queue));

	return NULL;

}