scsi: qedi: Fix host removal with running sessions

qedi_clear_session_ctx() could race with the in-kernel or userspace driven
recovery/removal and we could access a NULL conn or do a double free.

We should be using iscsi_host_remove() to start the removal process from
the driver. It will start the in-kernel recovery and notify userspace that
the driver's scsi_hosts are being removed. iscsid will then drive the
session removal like is done when the logout command is run. When the
sessions are removed, iscsi_host_remove() will return so qedi can finish
knowing there are no running sessions and no new sessions will be allowed.

This also fixes an issue where we check for a NULL conn after already
accessing it introduced in commit 27e98628 ("scsi: iscsi: Drop suspend
calls from ep_disconnect") by just removing the function completely.

Link: https://lore.kernel.org/r/20210609192709.5094-1-michael.christie@oracle.com
Fixes: 27e98628 ("scsi: iscsi: Drop suspend calls from ep_disconnect")
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/qedi/qedi_gbl.h

@@ -72,6 +72,5 @@ void qedi_remove_sysfs_ctx_attr(struct qedi_ctx *qedi);
 void qedi_clearsq(struct qedi_ctx *qedi,
 		  struct qedi_conn *qedi_conn,
 		  struct iscsi_task *task);
-void qedi_clear_session_ctx(struct iscsi_cls_session *cls_sess);
 
 #endif

drivers/scsi/qedi/qedi_iscsi.c

@@ -1659,23 +1659,6 @@ void qedi_process_iscsi_error(struct qedi_endpoint *ep,
 		qedi_start_conn_recovery(qedi_conn->qedi, qedi_conn);
 }
 
-void qedi_clear_session_ctx(struct iscsi_cls_session *cls_sess)
-{
-	struct iscsi_session *session = cls_sess->dd_data;
-	struct iscsi_conn *conn = session->leadconn;
-	struct qedi_conn *qedi_conn = conn->dd_data;
-
-	if (iscsi_is_session_online(cls_sess)) {
-		if (conn)
-			iscsi_suspend_queue(conn);
-		qedi_ep_disconnect(qedi_conn->iscsi_ep);
-	}
-
-	qedi_conn_destroy(qedi_conn->cls_conn);
-
-	qedi_session_destroy(cls_sess);
-}
-
 void qedi_process_tcp_error(struct qedi_endpoint *ep,
 			    struct iscsi_eqe_data *data)
 {

drivers/scsi/qedi/qedi_main.c

@@ -2417,11 +2417,9 @@ static void __qedi_remove(struct pci_dev *pdev, int mode)
 	int rval;
 	u16 retry = 10;
 
-	if (mode == QEDI_MODE_SHUTDOWN)
-		iscsi_host_for_each_session(qedi->shost,
-					    qedi_clear_session_ctx);
-
 	if (mode == QEDI_MODE_NORMAL || mode == QEDI_MODE_SHUTDOWN) {
+		iscsi_host_remove(qedi->shost);
+
 		if (qedi->tmf_thread) {
 			flush_workqueue(qedi->tmf_thread);
 			destroy_workqueue(qedi->tmf_thread);
@@ -2482,7 +2480,6 @@ static void __qedi_remove(struct pci_dev *pdev, int mode)
 		if (qedi->boot_kset)
 			iscsi_boot_destroy_kset(qedi->boot_kset);
 
-		iscsi_host_remove(qedi->shost);
 		iscsi_host_free(qedi->shost);
 	}
 }