> On Oct 29, 2020, at 1:49 AM, Mike Christie <michael.christie@xxxxxxxxxx> wrote:
>
> To remove the sess_cmd_lock this patch does:
>
> - Removes the sess_cmd_list use from lio core, because it's been
> moved to qla2xxx.
>
> - Removes sess_tearing_down check in the IO 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.
>
> Signed-off-by: Mike Christie <michael.christie@xxxxxxxxxx>
> ---
> drivers/infiniband/ulp/isert/ib_isert.c | 2 +-
> drivers/infiniband/ulp/srpt/ib_srpt.c | 2 +-
> drivers/scsi/qla2xxx/tcm_qla2xxx.c | 9 +---
> drivers/target/target_core_tpg.c | 2 +-
> drivers/target/target_core_transport.c | 77 ++++++++++++++-------------------
> drivers/target/tcm_fc/tfc_sess.c | 2 +-
> include/target/target_core_base.h | 6 +--
> include/target/target_core_fabric.h | 2 +-
> 8 files changed, 43 insertions(+), 59 deletions(-)
>
> diff --git a/drivers/infiniband/ulp/isert/ib_isert.c b/drivers/infiniband/ulp/isert/ib_isert.c
> index 436e17f..3d21bf3 100644
> --- a/drivers/infiniband/ulp/isert/ib_isert.c
> +++ b/drivers/infiniband/ulp/isert/ib_isert.c
> @@ -2471,7 +2471,7 @@ static void isert_release_work(struct work_struct *work)
> 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);
> }
> }
> diff --git a/drivers/infiniband/ulp/srpt/ib_srpt.c b/drivers/infiniband/ulp/srpt/ib_srpt.c
> index 0065eb1..8377113 100644
> --- a/drivers/infiniband/ulp/srpt/ib_srpt.c
> +++ b/drivers/infiniband/ulp/srpt/ib_srpt.c
> @@ -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);
> diff --git a/drivers/scsi/qla2xxx/tcm_qla2xxx.c b/drivers/scsi/qla2xxx/tcm_qla2xxx.c
> index e122da9..784b43f 100644
> --- a/drivers/scsi/qla2xxx/tcm_qla2xxx.c
> +++ b/drivers/scsi/qla2xxx/tcm_qla2xxx.c
> @@ -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,
> diff --git a/drivers/target/target_core_tpg.c b/drivers/target/target_core_tpg.c
> index 62aa5fa..736847c 100644
> --- a/drivers/target/target_core_tpg.c
> +++ b/drivers/target/target_core_tpg.c
> @@ -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);
> diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
> index 465b6583..b228c66 100644
> --- a/drivers/target/target_core_transport.c
> +++ b/drivers/target/target_core_transport.c
> @@ -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 @@ int transport_init_session(struct se_session *se_sess)
> 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 @@ void target_sess_cmd_list_set_waiting(struct se_session *se_sess)
> */
> 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);
>
> diff --git a/drivers/target/tcm_fc/tfc_sess.c b/drivers/target/tcm_fc/tfc_sess.c
> index 4fd6a1d..23ce506 100644
> --- a/drivers/target/tcm_fc/tfc_sess.c
> +++ b/drivers/target/tcm_fc/tfc_sess.c
> @@ -275,7 +275,7 @@ static struct ft_sess *ft_sess_delete(struct ft_tport *tport, u32 port_id)
>
> static void ft_close_sess(struct ft_sess *sess)
> {
> - target_sess_cmd_list_set_waiting(sess->se_sess);
> + target_stop_session(sess->se_sess);
> target_wait_for_sess_cmds(sess->se_sess);
> ft_sess_put(sess);
> }
> diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
> index b3c9946..2824463 100644
> --- a/include/target/target_core_base.h
> +++ b/include/target/target_core_base.h
> @@ -608,7 +608,7 @@ static inline struct se_node_acl *fabric_stat_to_nacl(struct config_item *item)
> }
>
> struct se_session {
> - unsigned sess_tearing_down:1;
> + atomic_t stopped;
> u64 sess_bin_isid;
> enum target_prot_op sup_prot_ops;
> enum target_prot_type sess_prot_type;
> @@ -618,9 +618,9 @@ struct se_session {
> struct percpu_ref cmd_count;
> struct list_head sess_list;
> struct list_head sess_acl_list;
> - struct list_head sess_cmd_list;
> spinlock_t sess_cmd_lock;
> - wait_queue_head_t cmd_list_wq;
> + wait_queue_head_t cmd_count_wq;
> + struct completion stop_done;
> void *sess_cmd_map;
> struct sbitmap_queue sess_tag_pool;
> };
> diff --git a/include/target/target_core_fabric.h b/include/target/target_core_fabric.h
> index 6adf4d7..d60a3eb 100644
> --- a/include/target/target_core_fabric.h
> +++ b/include/target/target_core_fabric.h
> @@ -178,7 +178,7 @@ int transport_send_check_condition_and_sense(struct se_cmd *,
> int target_send_busy(struct se_cmd *cmd);
> int target_get_sess_cmd(struct se_cmd *, bool);
> int target_put_sess_cmd(struct se_cmd *);
> -void target_sess_cmd_list_set_waiting(struct se_session *);
> +void target_stop_session(struct se_session *se_sess);
> void target_wait_for_sess_cmds(struct se_session *);
> void target_show_cmd(const char *pfx, struct se_cmd *cmd);
>
> --
> 1.8.3.1
>
For target and tcm_qla2xxx piece,
Reviewed-by: Himanshu Madhani <himanshu.madhani@xxxxxxxxxx>
--
Himanshu Madhani Oracle Linux Engineering
