Commit 6f55b06f authored Nov 01, 2020 by Mike Christie Committed by Martin K. Petersen Nov 04, 2020

scsi: target: Drop sess_cmd_lock from I/O path

Drop the sess_cmd_lock by:

 - Removing the sess_cmd_list use from LIO core, because it's been
   moved to qla2xxx.

 - Removing sess_tearing_down check in the I/O path. Instead of using that
   bit and the sess_cmd_lock, we rely on the cmd_count percpu ref. To do
   this we switch to percpu_ref_kill_and_confirm/percpu_ref_tryget_live.

Link: https://lore.kernel.org/r/1604257174-4524-7-git-send-email-michael.christie@oracle.com


Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

parent 605e7402

drivers/infiniband/ulp/isert/ib_isert.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -2471,7 +2471,7 @@ isert_wait4cmds(struct iscsi_conn *conn)
		isert_info("iscsi_conn %p\n", conn);

		if (conn->sess) {
		target_sess_cmd_list_set_waiting(conn->sess->se_sess);
		target_stop_session(conn->sess->se_sess);
		target_wait_for_sess_cmds(conn->sess->se_sess);
		}
		}

drivers/infiniband/ulp/srpt/ib_srpt.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -2084,7 +2084,7 @@ static void srpt_release_channel_work(struct work_struct *w)
		se_sess = ch->sess;
		BUG_ON(!se_sess);

		target_sess_cmd_list_set_waiting(se_sess);
		target_stop_session(se_sess);
		target_wait_for_sess_cmds(se_sess);

		target_remove_session(se_sess);

drivers/scsi/qla2xxx/tcm_qla2xxx.c

+2 −7

Original line number	Diff line number	Diff line
		@@ -368,15 +368,10 @@ static void tcm_qla2xxx_put_sess(struct fc_port *sess)
		static void tcm_qla2xxx_close_session(struct se_session *se_sess)
		{
		struct fc_port *sess = se_sess->fabric_sess_ptr;
		struct scsi_qla_host *vha;
		unsigned long flags;

		BUG_ON(!sess);
		vha = sess->vha;

		spin_lock_irqsave(&vha->hw->tgt.sess_lock, flags);
		target_sess_cmd_list_set_waiting(se_sess);
		spin_unlock_irqrestore(&vha->hw->tgt.sess_lock, flags);
		target_stop_session(se_sess);

		sess->explicit_logout = 1;
		tcm_qla2xxx_put_sess(sess);
		@@ -831,7 +826,7 @@ static void tcm_qla2xxx_clear_nacl_from_fcport_map(struct fc_port *sess)

		static void tcm_qla2xxx_shutdown_sess(struct fc_port *sess)
		{
		target_sess_cmd_list_set_waiting(sess->se_sess);
		target_stop_session(sess->se_sess);
		}

		static int tcm_qla2xxx_init_nodeacl(struct se_node_acl *se_nacl,

drivers/target/target_core_tpg.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -328,7 +328,7 @@ static void target_shutdown_sessions(struct se_node_acl *acl)
		restart:
		spin_lock_irqsave(&acl->nacl_sess_lock, flags);
		list_for_each_entry(sess, &acl->acl_sess_list, sess_acl_list) {
		if (sess->sess_tearing_down)
		if (atomic_read(&sess->stopped))
		continue;

		list_del_init(&sess->sess_acl_list);

drivers/target/target_core_transport.c

+33 −44

Original line number	Diff line number	Diff line
		@@ -215,7 +215,7 @@ static void target_release_sess_cmd_refcnt(struct percpu_ref *ref)
		{
		struct se_session sess = container_of(ref, typeof(sess), cmd_count);

		wake_up(&sess->cmd_list_wq);
		wake_up(&sess->cmd_count_wq);
		}

		/**
		@@ -228,9 +228,10 @@ int transport_init_session(struct se_session *se_sess)
		{
		INIT_LIST_HEAD(&se_sess->sess_list);
		INIT_LIST_HEAD(&se_sess->sess_acl_list);
		INIT_LIST_HEAD(&se_sess->sess_cmd_list);
		spin_lock_init(&se_sess->sess_cmd_lock);
		init_waitqueue_head(&se_sess->cmd_list_wq);
		init_waitqueue_head(&se_sess->cmd_count_wq);
		init_completion(&se_sess->stop_done);
		atomic_set(&se_sess->stopped, 0);
		return percpu_ref_init(&se_sess->cmd_count,
		target_release_sess_cmd_refcnt, 0, GFP_KERNEL);
		}
		@@ -239,11 +240,11 @@ EXPORT_SYMBOL(transport_init_session);
		void transport_uninit_session(struct se_session *se_sess)
		{
		/*
		* Drivers like iscsi and loop do not call
		* target_sess_cmd_list_set_waiting during session shutdown so we
		* have to drop the ref taken at init time here.
		* Drivers like iscsi and loop do not call target_stop_session
		* during session shutdown so we have to drop the ref taken at init
		* time here.
		*/
		if (!se_sess->sess_tearing_down)
		if (!atomic_read(&se_sess->stopped))
		percpu_ref_put(&se_sess->cmd_count);

		percpu_ref_exit(&se_sess->cmd_count);
		@@ -1632,9 +1633,8 @@ int target_submit_cmd_map_sgls(struct se_cmd se_cmd, struct se_session se_sess
		if (flags & TARGET_SCF_UNKNOWN_SIZE)
		se_cmd->unknown_data_length = 1;
		/*
		* Obtain struct se_cmd->cmd_kref reference and add new cmd to
		* se_sess->sess_cmd_list. A second kref_get here is necessary
		* for fabrics using TARGET_SCF_ACK_KREF that expect a second
		* Obtain struct se_cmd->cmd_kref reference. A second kref_get here is
		* necessary for fabrics using TARGET_SCF_ACK_KREF that expect a second
		* kref_put() to happen during fabric packet acknowledgement.
		*/
		ret = target_get_sess_cmd(se_cmd, flags & TARGET_SCF_ACK_KREF);
		@@ -2763,14 +2763,13 @@ int transport_generic_free_cmd(struct se_cmd *cmd, int wait_for_tasks)
		EXPORT_SYMBOL(transport_generic_free_cmd);

		/**
		* target_get_sess_cmd - Add command to active ->sess_cmd_list
		* target_get_sess_cmd - Verify the session is accepting cmds and take ref
		* @se_cmd: command descriptor to add
		* @ack_kref: Signal that fabric will perform an ack target_put_sess_cmd()
		*/
		int target_get_sess_cmd(struct se_cmd *se_cmd, bool ack_kref)
		{
		struct se_session *se_sess = se_cmd->se_sess;
		unsigned long flags;
		int ret = 0;

		/*
		@@ -2785,15 +2784,8 @@ int target_get_sess_cmd(struct se_cmd *se_cmd, bool ack_kref)
		se_cmd->se_cmd_flags \|= SCF_ACK_KREF;
		}

		spin_lock_irqsave(&se_sess->sess_cmd_lock, flags);
		if (se_sess->sess_tearing_down) {
		if (!percpu_ref_tryget_live(&se_sess->cmd_count))
		ret = -ESHUTDOWN;
		goto out;
		}
		list_add_tail(&se_cmd->se_cmd_list, &se_sess->sess_cmd_list);
		percpu_ref_get(&se_sess->cmd_count);
		out:
		spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);

		if (ret && ack_kref)
		target_put_sess_cmd(se_cmd);
		@@ -2818,13 +2810,6 @@ static void target_release_cmd_kref(struct kref *kref)
		struct se_session *se_sess = se_cmd->se_sess;
		struct completion *free_compl = se_cmd->free_compl;
		struct completion *abrt_compl = se_cmd->abrt_compl;
		unsigned long flags;

		if (se_sess) {
		spin_lock_irqsave(&se_sess->sess_cmd_lock, flags);
		list_del_init(&se_cmd->se_cmd_list);
		spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
		}

		target_free_cmd_mem(se_cmd);
		se_cmd->se_tfo->release_cmd(se_cmd);
		@@ -2952,21 +2937,25 @@ void target_show_cmd(const char pfx, struct se_cmd cmd)
		}
		EXPORT_SYMBOL(target_show_cmd);

		static void target_stop_session_confirm(struct percpu_ref *ref)
		{
		struct se_session *se_sess = container_of(ref, struct se_session,
		cmd_count);
		complete_all(&se_sess->stop_done);
		}

		/**
		* target_sess_cmd_list_set_waiting - Set sess_tearing_down so no new commands are queued.
		* @se_sess: session to flag
		* target_stop_session - Stop new IO from being queued on the session.
		* @se_sess: session to stop
		*/
		void target_sess_cmd_list_set_waiting(struct se_session *se_sess)
		void target_stop_session(struct se_session *se_sess)
		{
		unsigned long flags;

		spin_lock_irqsave(&se_sess->sess_cmd_lock, flags);
		se_sess->sess_tearing_down = 1;
		spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);

		percpu_ref_kill(&se_sess->cmd_count);
		pr_debug("Stopping session queue.\n");
		if (atomic_cmpxchg(&se_sess->stopped, 0, 1) == 0)
		percpu_ref_kill_and_confirm(&se_sess->cmd_count,
		target_stop_session_confirm);
		}
		EXPORT_SYMBOL(target_sess_cmd_list_set_waiting);
		EXPORT_SYMBOL(target_stop_session);

		/**
		* target_wait_for_sess_cmds - Wait for outstanding commands
		@@ -2974,19 +2963,19 @@ EXPORT_SYMBOL(target_sess_cmd_list_set_waiting);
		*/
		void target_wait_for_sess_cmds(struct se_session *se_sess)
		{
		struct se_cmd *cmd;
		int ret;

		WARN_ON_ONCE(!se_sess->sess_tearing_down);
		WARN_ON_ONCE(!atomic_read(&se_sess->stopped));

		do {
		ret = wait_event_timeout(se_sess->cmd_list_wq,
		pr_debug("Waiting for running cmds to complete.\n");
		ret = wait_event_timeout(se_sess->cmd_count_wq,
		percpu_ref_is_zero(&se_sess->cmd_count),
		180 * HZ);
		list_for_each_entry(cmd, &se_sess->sess_cmd_list, se_cmd_list)
		target_show_cmd("session shutdown: still waiting for ",
		cmd);
		} while (ret <= 0);

		wait_for_completion(&se_sess->stop_done);
		pr_debug("Waiting for cmds done.\n");
		}
		EXPORT_SYMBOL(target_wait_for_sess_cmds);