Commit fd858d1c authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
Browse files

loop: add helper lo_rw_aio_prep() 



Add helper lo_rw_aio_prep() to separate the preparation phase(setting up bio
vectors and initializing the iocb structure) from the actual I/O execution
in the loop block driver.

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 c3e6c111

drivers/block/loop.c

+40 −23
Original line number Diff line number Diff line
@@ -350,21 +350,15 @@ static inline unsigned lo_cmd_nr_bvec(struct loop_cmd *cmd) 
	return nr_bvec;

}



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

		     loff_t pos, int rw)

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

			  unsigned nr_bvec, loff_t pos)

{

	struct iov_iter iter;

	struct req_iterator rq_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;

	struct bio_vec tmp;

	unsigned int offset;

	int nr_bvec = lo_cmd_nr_bvec(cmd);

	int ret;



	if (rq->bio != rq->biotail) {

		struct req_iterator rq_iter;

		struct bio_vec *bvec;

		struct bio_vec tmp;



		bvec = kmalloc_array(nr_bvec, sizeof(struct bio_vec),

				     GFP_NOIO);
@@ -382,8 +376,42 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd, 
			*bvec = tmp;

			bvec++;

		}

		bvec = cmd->bvec;

	} else {

		cmd->bvec = NULL;

	}



	cmd->iocb.ki_pos = pos;

	cmd->iocb.ki_filp = lo->lo_backing_file;

	cmd->iocb.ki_ioprio = req_get_ioprio(rq);

	if (cmd->use_aio) {

		cmd->iocb.ki_complete = lo_rw_aio_complete;

		cmd->iocb.ki_flags = IOCB_DIRECT;

	} else {

		cmd->iocb.ki_complete = NULL;

		cmd->iocb.ki_flags = 0;

	}

	return 0;

}



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

		     loff_t pos, 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);

	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;

	} else {

		/*

		 * Same here, this bio may be started from the middle of the
@@ -398,17 +426,6 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd, 
	iov_iter_bvec(&iter, rw, bvec, nr_bvec, blk_rq_bytes(rq));

	iter.iov_offset = offset;



	cmd->iocb.ki_pos = pos;

	cmd->iocb.ki_filp = file;

	cmd->iocb.ki_ioprio = req_get_ioprio(rq);

	if (cmd->use_aio) {

		cmd->iocb.ki_complete = lo_rw_aio_complete;

		cmd->iocb.ki_flags = IOCB_DIRECT;

	} else {

		cmd->iocb.ki_complete = NULL;

		cmd->iocb.ki_flags = 0;

	}



	if (rw == ITER_SOURCE) {

		kiocb_start_write(&cmd->iocb);

		ret = file->f_op->write_iter(&cmd->iocb, &iter);