On 12/26/19 12:47 PM, Gabriel Krisman Bertazi wrote:
> From: Bharath Ravi
>
> Connection failure processing depends on a daemon being present to (at
> least) stop the connection and start recovery. This is a problem on a
> multipath scenario, where if the daemon failed for whatever reason, the
> SCSI path is never marked as down, multipath won't perform the
> failover and IO to the device will be forever waiting for that
> connection to come back.
>
> This patch performs the connection failure entirely inside the kernel.
> This way, the failover can happen and pending IO can continue even if
> the daemon is dead. Once the daemon comes alive again, it can execute
> recovery procedures if applicable.
>
> Changes since v2:
> - Don't hold rx_mutex for too long at once
>
> Changes since v1:
> - Remove module parameter.
> - Always do kernel-side stop work.
> - Block recovery timeout handler if system is dying.
> - send a CONN_TERM stop if the system is dying.
>
> Cc: Mike Christie
> Cc: Lee Duncan
> Cc: Bart Van Assche
> Co-developed-by: Dave Clausen
> Signed-off-by: Dave Clausen
> Co-developed-by: Nick Black
> Signed-off-by: Nick Black
> Co-developed-by: Vaibhav Nagarnaik
> Signed-off-by: Vaibhav Nagarnaik
> Co-developed-by: Anatol Pomazau
> Signed-off-by: Anatol Pomazau
> Co-developed-by: Tahsin Erdogan
> Signed-off-by: Tahsin Erdogan
> Co-developed-by: Frank Mayhar
> Signed-off-by: Frank Mayhar
> Co-developed-by: Junho Ryu
> Signed-off-by: Junho Ryu
> Co-developed-by: Khazhismel Kumykov
> Signed-off-by: Khazhismel Kumykov
> Signed-off-by: Bharath Ravi
> Co-developed-by: Gabriel Krisman Bertazi
> Signed-off-by: Gabriel Krisman Bertazi
> ---
> drivers/scsi/scsi_transport_iscsi.c | 63 +
> include/scsi/scsi_transport_iscsi.h | 1 +
> 2 files changed, 64 insertions(+)
>
> diff --git a/drivers/scsi/scsi_transport_iscsi.c
> b/drivers/scsi/scsi_transport_iscsi.c
> index 271afea654e2..c6db6ded60a1 100644
> --- a/drivers/scsi/scsi_transport_iscsi.c
> +++ b/drivers/scsi/scsi_transport_iscsi.c
> @@ -86,6 +86,12 @@ struct iscsi_internal {
> struct transport_container session_cont;
> };
>
> +/* Worker to perform connection failure on unresponsive connections
> + * completely in kernel space.
> + */
> +static void stop_conn_work_fn(struct work_struct *work);
> +static DECLARE_WORK(stop_conn_work, stop_conn_work_fn);
> +
> static atomic_t iscsi_session_nr; /* sysfs session id for next new session */
> static struct workqueue_struct *iscsi_eh_timer_workq;
>
> @@ -1611,6 +1617,7 @@ static DEFINE_MUTEX(rx_queue_mutex);
> static LIST_HEAD(sesslist);
> static DEFINE_SPINLOCK(sesslock);
> static LIST_HEAD(connlist);
> +static LIST_HEAD(connlist_err);
> static DEFINE_SPINLOCK(connlock);
>
> static uint32_t iscsi_conn_get_sid(struct iscsi_cls_conn *conn)
> @@ -2247,6 +2254,7 @@ iscsi_create_conn(struct iscsi_cls_session *session,
> int dd_size, uint32_t cid)
>
> mutex_init(>ep_mutex);
> INIT_LIST_HEAD(>conn_list);
> + INIT_LIST_HEAD(>conn_list_err);
> conn->transport = transport;
> conn->cid = cid;
>
> @@ -2293,6 +2301,7 @@ int iscsi_destroy_conn(struct iscsi_cls_conn *conn)
>
> spin_lock_irqsave(, flags);
> list_del(>conn_list);
> + list_del(>conn_list_err);
> spin_unlock_irqrestore(, flags);
>
> transport_unregister_device(>dev);
> @@ -2407,6 +2416,51 @@ int iscsi_offload_mesg(struct Scsi_Host *shost,
> }
> EXPORT_SYMBOL_GPL(iscsi_offload_mesg);
>
> +static void stop_conn_work_fn(struct work_struct *work)
> +{
> + struct iscsi_cls_conn *conn, *tmp;
> + unsigned long flags;
> + LIST_HEAD(recovery_list);
> +
> + spin_lock_irqsave(, flags);
> + if (list_empty(_err)) {
> + spin_unlock_irqrestore(, flags);
> + return;
> + }
> + list_splice_init(_err, _list);
> + spin_unlock_irqrestore(, flags);
> +
> + list_for_each_entry_safe(conn, tmp, _list, conn_list_err) {
> + uint32_t sid = iscsi_conn_get_sid(conn);
> + struct iscsi_cls_session *session;
> +
> + mutex_lock(_queue_mutex);
> +
> + session = iscsi_session_lookup(sid);
> + if (session) {
> + if (system_state != SYSTEM_RUNNING) {
> + session->recovery_tmo = 0;
> + conn->transport->stop_conn(conn,
> +STOP_CONN_TERM);
> + } else {
> + conn->transport->stop_conn(conn,
> +STOP_CONN_RECOVER);
> + }
> + }
> +
> + list_del_init(>conn_list_err);
> +
> + mutex_unlock(_queue_mutex);
> +
> + /* we don't want to hold rx_queue_mutex for too long,
> + * for instance if many conns failed at the same time,
> +
