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>

diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
index 22321cf84fbe2ce4c19090928ba5ecb83b8e5486..77d760bb2e44b4fb7626ab460e00b0f95bd10f1b 100644 (file)
--- a/drivers/vhost/tcm_vhost.c
+++ b/drivers/vhost/tcm_vhost.c
@@ -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
@@ -377,12 +354,18 @@ 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 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 @@ 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;

diff --git a/drivers/vhost/tcm_vhost.h b/drivers/vhost/tcm_vhost.h
index 7e87c63ecbcd84aa38b89d0568b8007cfa6cdd83..47ee80b3adee73b0261e79a5055f079c4ea0bd6e 100644 (file)
--- a/drivers/vhost/tcm_vhost.h
+++ b/drivers/vhost/tcm_vhost.h
@@ -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 {