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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
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+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;
+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 {