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 22321cf..77d760b 100644
--- 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_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;