Commit 302990ac authored by Mike Christie's avatar Mike Christie Committed by Martin K. Petersen
Browse files

scsi: target: core: Fix backend plugging 

target_core_iblock is plugging and unplugging on every command and this is
causing perf issues for drivers that prefer batched cmds. With recent
patches we can now take multiple cmds from a fabric driver queue and then
pass them down the backend drivers in a batch. This patch adds this support
by adding 2 callouts to the backend for plugging and unplugging the
device. Subsequent commits will add support for iblock and tcmu device
plugging.

Link: https://lore.kernel.org/r/20210227170006.5077-22-michael.christie@oracle.com


Reviewed-by: default avatarBodo Stroesser <bostroesser@gmail.com>
Signed-off-by: default avatarMike Christie <michael.christie@oracle.com>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent 802ec4f6

drivers/target/target_core_transport.c

+42 −1
Original line number Diff line number Diff line
@@ -1807,10 +1807,42 @@ void target_submit_cmd(struct se_cmd *se_cmd, struct se_session *se_sess, 
}

EXPORT_SYMBOL(target_submit_cmd);





static struct se_dev_plug *target_plug_device(struct se_device *se_dev)

{

	struct se_dev_plug *se_plug;



	if (!se_dev->transport->plug_device)

		return NULL;



	se_plug = se_dev->transport->plug_device(se_dev);

	if (!se_plug)

		return NULL;



	se_plug->se_dev = se_dev;

	/*

	 * We have a ref to the lun at this point, but the cmds could

	 * complete before we unplug, so grab a ref to the se_device so we

	 * can call back into the backend.

	 */

	config_group_get(&se_dev->dev_group);

	return se_plug;

}



static void target_unplug_device(struct se_dev_plug *se_plug)

{

	struct se_device *se_dev = se_plug->se_dev;



	se_dev->transport->unplug_device(se_plug);

	config_group_put(&se_dev->dev_group);

}



void target_queued_submit_work(struct work_struct *work)

{

	struct se_cmd_queue *sq = container_of(work, struct se_cmd_queue, work);

	struct se_cmd *se_cmd, *next_cmd;

	struct se_dev_plug *se_plug = NULL;

	struct se_device *se_dev = NULL;

	struct llist_node *cmd_list;



	cmd_list = llist_del_all(&sq->cmd_list);
@@ -1819,10 +1851,19 @@ void target_queued_submit_work(struct work_struct *work) 
		return;



	cmd_list = llist_reverse_order(cmd_list);

	llist_for_each_entry_safe(se_cmd, next_cmd, cmd_list, se_cmd_list)

	llist_for_each_entry_safe(se_cmd, next_cmd, cmd_list, se_cmd_list) {

		if (!se_dev) {

			se_dev = se_cmd->se_dev;

			se_plug = target_plug_device(se_dev);

		}



		target_submit(se_cmd);

	}



	if (se_plug)

		target_unplug_device(se_plug);

}



/**

 * target_queue_submission - queue the cmd to run on the LIO workqueue

 * @se_cmd: command descriptor to submit

include/target/target_core_backend.h

+2 −0
Original line number Diff line number Diff line
@@ -34,6 +34,8 @@ struct target_backend_ops { 
	int (*configure_device)(struct se_device *);

	void (*destroy_device)(struct se_device *);

	void (*free_device)(struct se_device *device);

	struct se_dev_plug *(*plug_device)(struct se_device *se_dev);

	void (*unplug_device)(struct se_dev_plug *se_plug);



	ssize_t (*set_configfs_dev_params)(struct se_device *,

					   const char *, ssize_t);

include/target/target_core_base.h

+4 −0
Original line number Diff line number Diff line
@@ -770,6 +770,10 @@ struct se_cmd_queue { 
	struct work_struct	work;

};



struct se_dev_plug {

	struct se_device	*se_dev;

};



struct se_device_queue {

	struct list_head	state_list;

	spinlock_t		lock;