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Commit 9d6064a3 authored by Asias He's avatar Asias He Committed by Nicholas Bellinger
Browse files

tcm_vhost: Use llist for cmd completion list 



This drops the cmd completion list spin lock and makes the cmd
completion queue lock-less.

Signed-off-by: default avatarAsias He <asias@redhat.com>
Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
parent 703d641d

drivers/vhost/tcm_vhost.c

+13 −33
Original line number Diff line number Diff line
@@ -47,6 +47,7 @@ 
#include <linux/vhost.h>

#include <linux/virtio_net.h> /* TODO vhost.h currently depends on this */

#include <linux/virtio_scsi.h>

#include <linux/llist.h>



#include "vhost.c"

#include "vhost.h"
@@ -64,8 +65,7 @@ struct vhost_scsi { 
	struct vhost_virtqueue vqs[3];



	struct vhost_work vs_completion_work; /* cmd completion work item */

	struct list_head vs_completion_list;  /* cmd completion queue */

	spinlock_t vs_completion_lock;        /* protects s_completion_list */

	struct llist_head vs_completion_list; /* cmd completion queue */

};



/* Local pointer to allocated TCM configfs fabric module */
@@ -301,9 +301,7 @@ static void vhost_scsi_complete_cmd(struct tcm_vhost_cmd *tv_cmd) 
{

	struct vhost_scsi *vs = tv_cmd->tvc_vhost;



	spin_lock_bh(&vs->vs_completion_lock);

	list_add_tail(&tv_cmd->tvc_completion_list, &vs->vs_completion_list);

	spin_unlock_bh(&vs->vs_completion_lock);

	llist_add(&tv_cmd->tvc_completion_list, &vs->vs_completion_list);



	vhost_work_queue(&vs->dev, &vs->vs_completion_work);

}
@@ -347,27 +345,6 @@ static void vhost_scsi_free_cmd(struct tcm_vhost_cmd *tv_cmd) 
	kfree(tv_cmd);

}



/* Dequeue a command from the completion list */

static struct tcm_vhost_cmd *vhost_scsi_get_cmd_from_completion(

	struct vhost_scsi *vs)

{

	struct tcm_vhost_cmd *tv_cmd = NULL;



	spin_lock_bh(&vs->vs_completion_lock);

	if (list_empty(&vs->vs_completion_list)) {

		spin_unlock_bh(&vs->vs_completion_lock);

		return NULL;

	}



	list_for_each_entry(tv_cmd, &vs->vs_completion_list,

			    tvc_completion_list) {

		list_del(&tv_cmd->tvc_completion_list);

		break;

	}

	spin_unlock_bh(&vs->vs_completion_lock);

	return tv_cmd;

}



/* Fill in status and signal that we are done processing this command

 *

 * This is scheduled in the vhost work queue so we are called with the owner
@@ -377,13 +354,19 @@ static void vhost_scsi_complete_cmd_work(struct vhost_work *work) 
{

	struct vhost_scsi *vs = container_of(work, struct vhost_scsi,

					vs_completion_work);

	struct tcm_vhost_cmd *tv_cmd;



	while ((tv_cmd = vhost_scsi_get_cmd_from_completion(vs))) {

	struct virtio_scsi_cmd_resp v_rsp;

		struct se_cmd *se_cmd = &tv_cmd->tvc_se_cmd;

	struct tcm_vhost_cmd *tv_cmd;

	struct llist_node *llnode;

	struct se_cmd *se_cmd;

	int ret;



	llnode = llist_del_all(&vs->vs_completion_list);

	while (llnode) {

		tv_cmd = llist_entry(llnode, struct tcm_vhost_cmd,

				     tvc_completion_list);

		llnode = llist_next(llnode);

		se_cmd = &tv_cmd->tvc_se_cmd;



		pr_debug("%s tv_cmd %p resid %u status %#02x\n", __func__,

			tv_cmd, se_cmd->residual_count, se_cmd->scsi_status);
@@ -426,7 +409,6 @@ static struct tcm_vhost_cmd *vhost_scsi_allocate_cmd( 
		pr_err("Unable to allocate struct tcm_vhost_cmd\n");

		return ERR_PTR(-ENOMEM);

	}

	INIT_LIST_HEAD(&tv_cmd->tvc_completion_list);

	tv_cmd->tvc_tag = v_req->tag;

	tv_cmd->tvc_task_attr = v_req->task_attr;

	tv_cmd->tvc_exp_data_len = exp_data_len;
@@ -857,8 +839,6 @@ static int vhost_scsi_open(struct inode *inode, struct file *f) 
		return -ENOMEM;



	vhost_work_init(&s->vs_completion_work, vhost_scsi_complete_cmd_work);

	INIT_LIST_HEAD(&s->vs_completion_list);

	spin_lock_init(&s->vs_completion_lock);



	s->vqs[VHOST_SCSI_VQ_CTL].handle_kick = vhost_scsi_ctl_handle_kick;

	s->vqs[VHOST_SCSI_VQ_EVT].handle_kick = vhost_scsi_evt_handle_kick;

drivers/vhost/tcm_vhost.h

+1 −1
Original line number Diff line number Diff line
@@ -34,7 +34,7 @@ struct tcm_vhost_cmd { 
	/* Sense buffer that will be mapped into outgoing status */

	unsigned char tvc_sense_buf[TRANSPORT_SENSE_BUFFER];

	/* Completed commands list, serviced from vhost worker thread */

	struct list_head tvc_completion_list;

	struct llist_node tvc_completion_list;

};



struct tcm_vhost_nexus {