Commit c66e9708 authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
Browse files

loop: add lo_submit_rw_aio() 



Refactor lo_rw_aio() by extracting the I/O submission logic into a new
helper function lo_submit_rw_aio(). This further improves code organization
by separating the I/O preparation, submission, and completion handling into
distinct phases.

Prepare for using NOWAIT to improve loop performance.

Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent fd858d1c

drivers/block/loop.c

+24 −17
Original line number Diff line number Diff line
@@ -393,38 +393,32 @@ static int lo_rw_aio_prep(struct loop_device *lo, struct loop_cmd *cmd, 
	return 0;

}



static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,

		     loff_t pos, int rw)

static int lo_submit_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,

			    int nr_bvec, int rw)

{

	struct iov_iter iter;

	struct bio_vec *bvec;

	struct request *rq = blk_mq_rq_from_pdu(cmd);

	struct bio *bio = rq->bio;

	struct file *file = lo->lo_backing_file;

	unsigned int offset;

	int nr_bvec = lo_cmd_nr_bvec(cmd);

	struct iov_iter iter;

	int ret;



	ret = lo_rw_aio_prep(lo, cmd, nr_bvec, pos);

	if (unlikely(ret))

		return ret;



	if (cmd->bvec) {

		offset = 0;

		bvec = cmd->bvec;

		iov_iter_bvec(&iter, rw, cmd->bvec, nr_bvec, blk_rq_bytes(rq));

		iter.iov_offset = 0;

	} else {

		struct bio *bio = rq->bio;

		struct bio_vec *bvec = __bvec_iter_bvec(bio->bi_io_vec,

				bio->bi_iter);



		/*

		 * Same here, this bio may be started from the middle of the

		 * 'bvec' because of bio splitting, so offset from the bvec

		 * must be passed to iov iterator

		 */

		offset = bio->bi_iter.bi_bvec_done;

		bvec = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);

		iov_iter_bvec(&iter, rw, bvec, nr_bvec, blk_rq_bytes(rq));

		iter.iov_offset = bio->bi_iter.bi_bvec_done;

	}

	atomic_set(&cmd->ref, 2);



	iov_iter_bvec(&iter, rw, bvec, nr_bvec, blk_rq_bytes(rq));

	iter.iov_offset = offset;



	if (rw == ITER_SOURCE) {

		kiocb_start_write(&cmd->iocb);
@@ -433,7 +427,20 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd, 
		ret = file->f_op->read_iter(&cmd->iocb, &iter);



	lo_rw_aio_do_completion(cmd);

	return ret;

}



static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,

		     loff_t pos, int rw)

{

	int nr_bvec = lo_cmd_nr_bvec(cmd);

	int ret;



	ret = lo_rw_aio_prep(lo, cmd, nr_bvec, pos);

	if (unlikely(ret))

		return ret;



	ret = lo_submit_rw_aio(lo, cmd, nr_bvec, rw);

	if (ret != -EIOCBQUEUED)

		lo_rw_aio_complete(&cmd->iocb, ret);

	return -EIOCBQUEUED;