scst.h, scst, device handlers: Fix scst_replace_port_info

scst_pass_through_cmd_done can run in interrupt context, and call
scst_replace_port_info, which in turn was calling scst_lookup_tg_id.
Since scst_lookup_tg_id does a mutex_lock, we should not call it from
interrupt context.

Add scst_cmd_inquired_dev_ident and use in various locations.

scst/include/scst.h

@@ -2315,6 +2315,8 @@ struct scst_cmd {
 
 	uint32_t tgt_sn; /* SN set by target driver (for TM purposes) */
 
+	uint16_t tg_id; /* Only used during TYPE_DISK INQUIRY EVPD=0x83 */
+
 	uint8_t *cdb; /* Pointer on CDB. Points on cdb_buf for small CDBs. */
 	unsigned short cdb_len;
 	uint8_t cdb_buf[SCST_MAX_CDB_SIZE];
@@ -4520,6 +4522,13 @@ static inline bool scst_get_cmd_dev_d_sense(struct scst_cmd *cmd)
 	return (cmd->dev != NULL) ? cmd->dev->d_sense : 0;
 }
 
+/* Returns if command is INQUIRY EVPD=0x83 (device identification) */
+static inline bool scst_cmd_inquired_dev_ident(struct scst_cmd *cmd)
+{
+	return (cmd->cdb[0] == INQUIRY) && ((cmd->cdb[1] & 0x01/*EVPD*/) == 0x01) &&
+		(cmd->cdb[2] == 0x83/*device identification*/);
+}
+
 /*
  * Get/Set functions for expected data direction, transfer length
  * and its validity flag

scst/src/dev_handlers/scst_disk.c

@@ -374,6 +374,15 @@ static enum scst_exec_res disk_exec(struct scst_cmd *cmd)
 		}
 	}
 
+	/*
+	 * If we are passing thru a INQUIRY VPD=0x83 (device identification) then
+	 * we will call scst_replace_port_info on success in scst_pass_through_cmd_done.
+	 * This will run in interrupt context, so we should not perform operations that
+	 * involve mutexes.  Call scst_lookup_tg_id here intead and save the output.
+	 */
+	if (unlikely(scst_cmd_inquired_dev_ident(cmd)))
+		cmd->tg_id = scst_lookup_tg_id(dev, tgt);
+
 	/*
 	 * For PC requests we are going to submit max_hw_sectors used instead
 	 * of max_sectors.

scst/src/scst_targ.c

@@ -2227,8 +2227,7 @@ static void scst_replace_port_info(struct scst_cmd *cmd)
 	uint8_t *buf, *end, *p, designator_length;
 	int32_t length, page_length;
 
-	if (cmd->cdb[0] != INQUIRY || (cmd->cdb[1] & 0x01/*EVPD*/) == 0 ||
-	    cmd->cdb[2] != 0x83/*device identification*/)
+	if (!scst_cmd_inquired_dev_ident(cmd))
 		return;
 
 	length = scst_get_buf_full_sense(cmd, &buf);
@@ -2242,7 +2241,6 @@ static void scst_replace_port_info(struct scst_cmd *cmd)
 		const uint8_t code_set = p[0] & 0xf;
 		const uint8_t association = (p[1] & 0x30) >> 4;
 		const uint8_t designator_type = p[1] & 0xf;
-		uint16_t tg_id;
 
 		designator_length = p[3];
 
@@ -2259,9 +2257,7 @@ static void scst_replace_port_info(struct scst_cmd *cmd)
 			break;
 		case 5:
 			/* target port group */
-			tg_id = scst_lookup_tg_id(cmd->dev, cmd->tgt);
-			if (tg_id)
-				put_unaligned_be16(tg_id, p + 6);
+			put_unaligned_be16(cmd->tg_id, p + 6);
 			break;
 		}
 	}
@@ -2622,6 +2618,9 @@ static enum scst_exec_res scst_do_real_exec(struct scst_cmd *cmd)
 		  scsi_dev->host->host_no, scsi_dev->channel, scsi_dev->id,
 		  (u64)scsi_dev->lun);
 
+	if (unlikely(scst_cmd_inquired_dev_ident(cmd)))
+		cmd->tg_id = scst_lookup_tg_id(dev, cmd->tgt);
+
 	rc = scst_scsi_exec_async(cmd, cmd, scst_pass_through_cmd_done);
 	if (unlikely(rc != 0)) {
 		PRINT_ERROR("scst pass-through exec failed: %d", rc);