scsi: lpfc: Fix reusing an ndlp that is marked NLP_DROPPED during FLOGI

It's possible for an unstable link to repeatedly bounce allowing a FLOGI
retry, but then bounce again forcing an abort of the FLOGI.  Ensure that
the initial reference count on the FLOGI ndlp is restored in this faulty
link scenario.

Signed-off-by: Justin Tee <justin.tee@broadcom.com>
Link: https://patch.msgid.link/20251106224639.139176-8-justintee8345@gmail.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/lpfc/lpfc_els.c

@@ -934,10 +934,15 @@ lpfc_cmpl_els_flogi(struct lpfc_hba *phba, struct lpfc_iocbq *cmdiocb,
 	/* Check to see if link went down during discovery */
 	if (lpfc_els_chk_latt(vport)) {
 		/* One additional decrement on node reference count to
-		 * trigger the release of the node
+		 * trigger the release of the node.  Make sure the ndlp
+		 * is marked NLP_DROPPED.
 		 */
-		if (!(ndlp->fc4_xpt_flags & SCSI_XPT_REGD))
+		if (!test_bit(NLP_IN_DEV_LOSS, &ndlp->nlp_flag) &&
+		    !test_bit(NLP_DROPPED, &ndlp->nlp_flag) &&
+		    !(ndlp->fc4_xpt_flags & SCSI_XPT_REGD)) {
+			set_bit(NLP_DROPPED, &ndlp->nlp_flag);
 			lpfc_nlp_put(ndlp);
+		}
 		goto out;
 	}
 
@@ -995,9 +1000,10 @@ stop_rr_fcf_flogi:
 					IOERR_LOOP_OPEN_FAILURE)))
 			lpfc_vlog_msg(vport, KERN_WARNING, LOG_ELS,
 				      "2858 FLOGI Status:x%x/x%x TMO"
-				      ":x%x Data x%lx x%x\n",
+				      ":x%x Data x%lx x%x x%lx x%x\n",
 				      ulp_status, ulp_word4, tmo,
-				      phba->hba_flag, phba->fcf.fcf_flag);
+				      phba->hba_flag, phba->fcf.fcf_flag,
+				      ndlp->nlp_flag, ndlp->fc4_xpt_flags);
 
 		/* Check for retry */
 		if (lpfc_els_retry(phba, cmdiocb, rspiocb)) {
@@ -1015,14 +1021,17 @@ stop_rr_fcf_flogi:
 		 * reference to trigger node release.
 		 */
 		if (!test_bit(NLP_IN_DEV_LOSS, &ndlp->nlp_flag) &&
-		    !(ndlp->fc4_xpt_flags & SCSI_XPT_REGD))
+		    !test_bit(NLP_DROPPED, &ndlp->nlp_flag) &&
+		    !(ndlp->fc4_xpt_flags & SCSI_XPT_REGD)) {
+			set_bit(NLP_DROPPED, &ndlp->nlp_flag);
 			lpfc_nlp_put(ndlp);
+		}
 
 		lpfc_printf_vlog(vport, KERN_WARNING, LOG_ELS,
 				 "0150 FLOGI Status:x%x/x%x "
-				 "xri x%x TMO:x%x refcnt %d\n",
+				 "xri x%x iotag x%x TMO:x%x refcnt %d\n",
 				 ulp_status, ulp_word4, cmdiocb->sli4_xritag,
-				 tmo, kref_read(&ndlp->kref));
+				 cmdiocb->iotag, tmo, kref_read(&ndlp->kref));
 
 		/* If this is not a loop open failure, bail out */
 		if (!(ulp_status == IOSTAT_LOCAL_REJECT &&
@@ -1279,6 +1288,19 @@ lpfc_issue_els_flogi(struct lpfc_vport *vport, struct lpfc_nodelist *ndlp,
 	uint32_t tmo, did;
 	int rc;
 
+	/* It's possible for lpfc to reissue a FLOGI on an ndlp that is marked
+	 * NLP_DROPPED.  This happens when the FLOGI completed with the XB bit
+	 * set causing lpfc to reference the ndlp until the XRI_ABORTED CQE is
+	 * issued. The time window for the XRI_ABORTED CQE can be as much as
+	 * 2*2*RA_TOV allowing for ndlp reuse of this type when the link is
+	 * cycling quickly.  When true, restore the initial reference and remove
+	 * the NLP_DROPPED flag as lpfc is retrying.
+	 */
+	if (test_and_clear_bit(NLP_DROPPED, &ndlp->nlp_flag)) {
+		if (!lpfc_nlp_get(ndlp))
+			return 1;
+	}
+
 	cmdsize = (sizeof(uint32_t) + sizeof(struct serv_parm));
 	elsiocb = lpfc_prep_els_iocb(vport, 1, cmdsize, retry, ndlp,
 				     ndlp->nlp_DID, ELS_CMD_FLOGI);

drivers/scsi/lpfc/lpfc_hbadisc.c

@@ -424,6 +424,7 @@ lpfc_check_nlp_post_devloss(struct lpfc_vport *vport,
 			    struct lpfc_nodelist *ndlp)
 {
 	if (test_and_clear_bit(NLP_IN_RECOV_POST_DEV_LOSS, &ndlp->save_flags)) {
+		clear_bit(NLP_DROPPED, &ndlp->nlp_flag);
 		lpfc_nlp_get(ndlp);
 		lpfc_printf_vlog(vport, KERN_INFO, LOG_DISCOVERY | LOG_NODE,
 				 "8438 Devloss timeout reversed on DID x%x "
@@ -566,6 +567,7 @@ lpfc_dev_loss_tmo_handler(struct lpfc_nodelist *ndlp)
 			return fcf_inuse;
 		}
 
+		if (!test_and_set_bit(NLP_DROPPED, &ndlp->nlp_flag))
 			lpfc_nlp_put(ndlp);
 		return fcf_inuse;
 	}