loop and vhost-scsi do their target cmd submission from driver
workqueues. This allows them to avoid an issue where the backend may
block waiting for resources like tags/requests, mem/locks, etc
and that ends up blocking their entire submission path and for the
case of vhost-scsi both the submission and completion path.
This patch adds a helper these drivers can use to submit from the
lio workqueue. This code will then be extended in the next patches
to fix the plugging of backend devices.
Signed-off-by: Mike Christie <michael.christie@xxxxxxxxxx>
---
drivers/target/target_core_transport.c | 102 ++++++++++++++++++++++++-
include/target/target_core_base.h | 10 ++-
include/target/target_core_fabric.h | 3 +
3 files changed, 111 insertions(+), 4 deletions(-)
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 7c5d37bac561..dec89e911348 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -41,6 +41,7 @@
#include <trace/events/target.h>
static struct workqueue_struct *target_completion_wq;
+static struct workqueue_struct *target_submission_wq;
static struct kmem_cache *se_sess_cache;
struct kmem_cache *se_ua_cache;
struct kmem_cache *t10_pr_reg_cache;
@@ -129,8 +130,15 @@ int init_se_kmem_caches(void)
if (!target_completion_wq)
goto out_free_lba_map_mem_cache;
+ target_submission_wq = alloc_workqueue("target_submission",
+ WQ_MEM_RECLAIM, 0);
+ if (!target_submission_wq)
+ goto out_free_completion_wq;
+
return 0;
+out_free_completion_wq:
+ destroy_workqueue(target_completion_wq);
out_free_lba_map_mem_cache:
kmem_cache_destroy(t10_alua_lba_map_mem_cache);
out_free_lba_map_cache:
@@ -153,6 +161,7 @@ int init_se_kmem_caches(void)
void release_se_kmem_caches(void)
{
+ destroy_workqueue(target_submission_wq);
destroy_workqueue(target_completion_wq);
kmem_cache_destroy(se_sess_cache);
kmem_cache_destroy(se_ua_cache);
@@ -218,6 +227,69 @@ static void target_release_sess_cmd_refcnt(struct percpu_ref *ref)
wake_up(&sess->cmd_count_wq);
}
+static void target_queued_submit_work(struct work_struct *work)
+{
+ struct se_sess_cmd_queue *sq =
+ container_of(work, struct se_sess_cmd_queue,
+ work);
+ struct se_session *se_sess = sq->se_sess;
+ struct se_cmd *se_cmd, *next_cmd;
+ struct llist_node *cmd_list;
+
+ cmd_list = llist_del_all(&sq->cmd_list);
+ if (!cmd_list)
+ /* Previous call took what we were queued to submit */
+ return;
+
+ cmd_list = llist_reverse_order(cmd_list);
+ llist_for_each_entry_safe(se_cmd, next_cmd, cmd_list, se_cmd_list)
+ se_sess->tfo->submit_queued_cmd(se_cmd);
+}
+
+static void target_queue_cmd_work(struct se_sess_cmd_queue *q,
+ struct se_cmd *se_cmd, int cpu)
+{
+ llist_add(&se_cmd->se_cmd_list, &q->cmd_list);
+ queue_work_on(cpu, target_submission_wq, &q->work);
+}
+
+/**
+ * target_queue_cmd_submit - queue a se_cmd to be executed from the lio wq
+ * @se_sess: cmd's session
+ * @cmd_list: cmd to queue
+ */
+void target_queue_cmd_submit(struct se_session *se_sess, struct se_cmd *se_cmd)
+{
+ int cpu = smp_processor_id();
+
+ target_queue_cmd_work(&se_sess->sq[cpu], se_cmd, cpu);
+}
+EXPORT_SYMBOL_GPL(target_queue_cmd_submit);
+
+static void target_flush_queued_cmds(struct se_session *se_sess)
+{
+ int i;
+
+ if (!se_sess->sq)
+ return;
+
+ for (i = 0; i < se_sess->q_cnt; i++)
+ cancel_work_sync(&se_sess->sq[i].work);
+}
+
+static void target_init_sess_cmd_queues(struct se_session *se_sess,
+ struct se_sess_cmd_queue *q,
+ void (*work_fn)(struct work_struct *work))
+{
+ int i;
+
+ for (i = 0; i < se_sess->q_cnt; i++) {
+ init_llist_head(&q[i].cmd_list);
+ INIT_WORK(&q[i].work, work_fn);
+ q[i].se_sess = se_sess;
+ }
+}
+
