target: Make target_put_sess_cmd use target_release_cmd_kref

This patch moves target_put_sess_cmd() to use a se_cmd->cmd_kref
callback target_release_cmd_kref when performing driver release of
fabric->se_cmd descriptor memory.  It sets the default cmd_kref
count value to '2' within target_get_sess_cmd() setup, and
currently assumes TFO->check_stop_free() usage.

It drops se_tfo->check_release_cmd() usage in the main
transport_release_cmd codepath.

Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

2 files changed, 25 insertions, 15 deletions

diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 122925686de2..176f956665e8 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -3349,13 +3349,13 @@ static void transport_release_cmd(struct se_cmd *cmd)
         if (cmd->t_task_cdb != cmd->__t_task_cdb)
                 kfree(cmd->t_task_cdb);
         /*
-         * Check if target_wait_for_sess_cmds() is expecting to
-         * release se_cmd directly here..
+         * If this cmd has been setup with target_get_sess_cmd(), drop
+         * the kref and call ->release_cmd() in kref callback.
          */
-        if (cmd->check_release != 0 && cmd->se_tfo->check_release_cmd)
-                if (cmd->se_tfo->check_release_cmd(cmd) != 0)
-                        return;
-
+         if (cmd->check_release != 0) {
+                target_put_sess_cmd(cmd->se_sess, cmd);
+                return;
+        }
         cmd->se_tfo->release_cmd(cmd);
 }
 
@@ -3915,6 +3915,9 @@ void target_get_sess_cmd(struct se_session *se_sess, struct se_cmd *se_cmd)
 {
         unsigned long flags;
 
+        kref_init(&se_cmd->cmd_kref);
+        kref_get(&se_cmd->cmd_kref);
+
         spin_lock_irqsave(&se_sess->sess_cmd_lock, flags);
         list_add_tail(&se_cmd->se_cmd_list, &se_sess->sess_cmd_list);
         se_cmd->check_release = 1;
@@ -3922,30 +3925,36 @@ void target_get_sess_cmd(struct se_session *se_sess, struct se_cmd *se_cmd)
 }
 EXPORT_SYMBOL(target_get_sess_cmd);
 
-/* target_put_sess_cmd - Check for active I/O shutdown or list delete
- * @se_sess:    session to reference
- * @se_cmd:     command descriptor to drop
- */
-int target_put_sess_cmd(struct se_session *se_sess, struct se_cmd *se_cmd)
+static void target_release_cmd_kref(struct kref *kref)
 {
+        struct se_cmd *se_cmd = container_of(kref, struct se_cmd, cmd_kref);
+        struct se_session *se_sess = se_cmd->se_sess;
         unsigned long flags;
 
         spin_lock_irqsave(&se_sess->sess_cmd_lock, flags);
         if (list_empty(&se_cmd->se_cmd_list)) {
                 spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
                 WARN_ON(1);
-                return 0;
+                return;
         }
-
         if (se_sess->sess_tearing_down && se_cmd->cmd_wait_set) {
                 spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
                 complete(&se_cmd->cmd_wait_comp);
-                return 1;
+                return;
         }
         list_del(&se_cmd->se_cmd_list);
         spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
 
-        return 0;
+        se_cmd->se_tfo->release_cmd(se_cmd);
+}
+
+/* target_put_sess_cmd - Check for active I/O shutdown via kref_put
+ * @se_sess:    session to reference
+ * @se_cmd:     command descriptor to drop
+ */
+int target_put_sess_cmd(struct se_session *se_sess, struct se_cmd *se_cmd)
+{
+        return kref_put(&se_cmd->cmd_kref, target_release_cmd_kref);
 }
 EXPORT_SYMBOL(target_put_sess_cmd);
 
diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index cadd4f6e57e1..af088a9e4905 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -541,6 +541,7 @@ struct se_cmd {
         struct list_head        se_queue_node;
         struct list_head        se_cmd_list;
         struct completion       cmd_wait_comp;
+        struct kref             cmd_kref;
         struct target_core_fabric_ops *se_tfo;
         int (*execute_task)(struct se_task *);
         void (*transport_complete_callback)(struct se_cmd *);