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: Asias He <asias@redhat.com> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

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: Asias He <asias@redhat.com> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Asias He · Nicholas Bellinger
1 parent 703d641d87
Showing 2 changed files with 14 additions and 34 deletions Side-by-side Diff
drivers/vhost/tcm_vhost.c
drivers/vhost/tcm_vhost.h
@@ -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_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 @@
 {
 	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 @@
 	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
  
  
@@ -377,12 +354,18 @@
 {
 	struct vhost_scsi *vs = container_of(work, struct vhost_scsi,
 					vs_completion_work);
+	struct virtio_scsi_cmd_resp v_rsp;
 	struct tcm_vhost_cmd *tv_cmd;
+	struct llist_node *llnode;
+	struct se_cmd *se_cmd;
+	int ret;
  
-	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;
-		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 @@
 		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 @@
 		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;
@@ -34,7 +34,7 @@
 	/* 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 {
...	...	@@ -47,6 +47,7 @@
47	47	#include <linux/vhost.h>
48	48	#include <linux/virtio_net.h> /* TODO vhost.h currently depends on this */
49	49	#include <linux/virtio_scsi.h>
	50	+#include <linux/llist.h>
50	51
51	52	#include "vhost.c"
52	53	#include "vhost.h"
...	...	@@ -64,8 +65,7 @@
64	65	struct vhost_virtqueue vqs[3];
65	66
66	67	struct vhost_work vs_completion_work; /* cmd completion work item */
67		- struct list_head vs_completion_list; /* cmd completion queue */
68		- spinlock_t vs_completion_lock; /* protects s_completion_list */
	68	+ struct llist_head vs_completion_list; /* cmd completion queue */
69	69	};
70	70
71	71	/* Local pointer to allocated TCM configfs fabric module */
...	...	@@ -301,9 +301,7 @@
301	301	{
302	302	struct vhost_scsi *vs = tv_cmd->tvc_vhost;
303	303
304		- spin_lock_bh(&vs->vs_completion_lock);
305		- list_add_tail(&tv_cmd->tvc_completion_list, &vs->vs_completion_list);
306		- spin_unlock_bh(&vs->vs_completion_lock);
	304	+ llist_add(&tv_cmd->tvc_completion_list, &vs->vs_completion_list);
307	305
308	306	vhost_work_queue(&vs->dev, &vs->vs_completion_work);
309	307	}
...	...	@@ -347,27 +345,6 @@
347	345	kfree(tv_cmd);
348	346	}
349	347
350		-/* Dequeue a command from the completion list */
351		-static struct tcm_vhost_cmd *vhost_scsi_get_cmd_from_completion(
352		- struct vhost_scsi *vs)
353		-{
354		- struct tcm_vhost_cmd *tv_cmd = NULL;
355		-
356		- spin_lock_bh(&vs->vs_completion_lock);
357		- if (list_empty(&vs->vs_completion_list)) {
358		- spin_unlock_bh(&vs->vs_completion_lock);
359		- return NULL;
360		- }
361		-
362		- list_for_each_entry(tv_cmd, &vs->vs_completion_list,
363		- tvc_completion_list) {
364		- list_del(&tv_cmd->tvc_completion_list);
365		- break;
366		- }
367		- spin_unlock_bh(&vs->vs_completion_lock);
368		- return tv_cmd;
369		-}
370		-
371	348	/* Fill in status and signal that we are done processing this command
372	349	*
373	350	* This is scheduled in the vhost work queue so we are called with the owner
374	351
375	352
...	...	@@ -377,12 +354,18 @@
377	354	{
378	355	struct vhost_scsi *vs = container_of(work, struct vhost_scsi,
379	356	vs_completion_work);
	357	+ struct virtio_scsi_cmd_resp v_rsp;
380	358	struct tcm_vhost_cmd *tv_cmd;
	359	+ struct llist_node *llnode;
	360	+ struct se_cmd *se_cmd;
	361	+ int ret;
381	362
382		- while ((tv_cmd = vhost_scsi_get_cmd_from_completion(vs))) {
383		- struct virtio_scsi_cmd_resp v_rsp;
384		- struct se_cmd *se_cmd = &tv_cmd->tvc_se_cmd;
385		- int ret;
	363	+ llnode = llist_del_all(&vs->vs_completion_list);
	364	+ while (llnode) {
	365	+ tv_cmd = llist_entry(llnode, struct tcm_vhost_cmd,
	366	+ tvc_completion_list);
	367	+ llnode = llist_next(llnode);
	368	+ se_cmd = &tv_cmd->tvc_se_cmd;
386	369
387	370	pr_debug("%s tv_cmd %p resid %u status %#02x\n", __func__,
388	371	tv_cmd, se_cmd->residual_count, se_cmd->scsi_status);
...	...	@@ -426,7 +409,6 @@
426	409	pr_err("Unable to allocate struct tcm_vhost_cmd\n");
427	410	return ERR_PTR(-ENOMEM);
428	411	}
429		- INIT_LIST_HEAD(&tv_cmd->tvc_completion_list);
430	412	tv_cmd->tvc_tag = v_req->tag;
431	413	tv_cmd->tvc_task_attr = v_req->task_attr;
432	414	tv_cmd->tvc_exp_data_len = exp_data_len;
...	...	@@ -857,8 +839,6 @@
857	839	return -ENOMEM;
858	840
859	841	vhost_work_init(&s->vs_completion_work, vhost_scsi_complete_cmd_work);
860		- INIT_LIST_HEAD(&s->vs_completion_list);
861		- spin_lock_init(&s->vs_completion_lock);
862	842
863	843	s->vqs[VHOST_SCSI_VQ_CTL].handle_kick = vhost_scsi_ctl_handle_kick;
864	844	s->vqs[VHOST_SCSI_VQ_EVT].handle_kick = vhost_scsi_evt_handle_kick;
...	...	@@ -34,7 +34,7 @@
34	34	/* Sense buffer that will be mapped into outgoing status */
35	35	unsigned char tvc_sense_buf[TRANSPORT_SENSE_BUFFER];
36	36	/* Completed commands list, serviced from vhost worker thread */
37		- struct list_head tvc_completion_list;
	37	+ struct llist_node tvc_completion_list;
38	38	};
39	39
40	40	struct tcm_vhost_nexus {