scsi: target: core: Add RTPI attribute for target port

RELATIVE TARGET PORT IDENTIFIER can be read and configured via configfs:

$ echo 0x10 > $TARGET/tpgt_N/rtpi

RTPI can be changed only on disabled target ports.
Co-developed-by: Roman Bolshakov <r.bolshakov@yadro.com>
Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
Signed-off-by: Dmitry Bogdanov <d.bogdanov@yadro.com>
Link: https://lore.kernel.org/r/20230301084512.21956-5-d.bogdanov@yadro.comReviewed-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/target/target_core_fabric_configfs.c

@@ -844,15 +844,48 @@ static ssize_t target_fabric_tpg_base_enable_store(struct config_item *item,
 		return ret;
 	return count;
 }
+static ssize_t target_fabric_tpg_base_rtpi_show(struct config_item *item, char *page)
+{
+	struct se_portal_group *se_tpg = to_tpg(item);
+
+	return sysfs_emit(page, "%#x\n", se_tpg->tpg_rtpi);
+}
+
+static ssize_t target_fabric_tpg_base_rtpi_store(struct config_item *item,
+				   const char *page, size_t count)
+{
+	struct se_portal_group *se_tpg = to_tpg(item);
+	u16 val;
+	int ret;
+
+	ret = kstrtou16(page, 0, &val);
+	if (ret < 0)
+		return ret;
+	if (val == 0)
+		return -EINVAL;
+
+	if (se_tpg->enabled) {
+		pr_info("%s_TPG[%hu] - Can not change RTPI on enabled TPG",
+			se_tpg->se_tpg_tfo->fabric_name,
+			se_tpg->se_tpg_tfo->tpg_get_tag(se_tpg));
+		return -EINVAL;
+	}
+
+	se_tpg->tpg_rtpi = val;
+	se_tpg->rtpi_manual = true;
+
+	return count;
+}
 
 CONFIGFS_ATTR(target_fabric_tpg_base_, enable);
+CONFIGFS_ATTR(target_fabric_tpg_base_, rtpi);
 
 static int
 target_fabric_setup_tpg_base_cit(struct target_fabric_configfs *tf)
 {
 	struct config_item_type *cit = &tf->tf_tpg_base_cit;
 	struct configfs_attribute **attrs = NULL;
-	size_t nr_attrs = 0;
+	size_t nr_attrs = 1;
 	int i = 0;
 
 	if (tf->tf_ops->tfc_tpg_base_attrs)
@@ -875,7 +908,9 @@ target_fabric_setup_tpg_base_cit(struct target_fabric_configfs *tf)
 			attrs[i] = tf->tf_ops->tfc_tpg_base_attrs[i];
 
 	if (tf->tf_ops->fabric_enable_tpg)
-		attrs[i] = &target_fabric_tpg_base_attr_enable;
+		attrs[i++] = &target_fabric_tpg_base_attr_enable;
+
+	attrs[i++] = &target_fabric_tpg_base_attr_rtpi;
 
 done:
 	cit->ct_item_ops = &target_fabric_tpg_base_item_ops;

drivers/target/target_core_tpg.c

@@ -445,10 +445,21 @@ static int target_tpg_register_rtpi(struct se_portal_group *se_tpg)
 	u32 val;
 	int ret;
 
-	ret = xa_alloc(&tpg_xa, &val, se_tpg,
-		       XA_LIMIT(1, USHRT_MAX), GFP_KERNEL);
-	if (!ret)
-		se_tpg->tpg_rtpi = val;
+	if (se_tpg->rtpi_manual) {
+		ret = xa_insert(&tpg_xa, se_tpg->tpg_rtpi, se_tpg, GFP_KERNEL);
+		if (ret) {
+			pr_info("%s_TPG[%hu] - Can not set RTPI %#x, it is already busy",
+				se_tpg->se_tpg_tfo->fabric_name,
+				se_tpg->se_tpg_tfo->tpg_get_tag(se_tpg),
+				se_tpg->tpg_rtpi);
+			return -EINVAL;
+		}
+	} else {
+		ret = xa_alloc(&tpg_xa, &val, se_tpg,
+			       XA_LIMIT(1, USHRT_MAX), GFP_KERNEL);
+		if (!ret)
+			se_tpg->tpg_rtpi = val;
+	}
 
 	return ret;
 }

include/target/target_core_base.h

@@ -918,6 +918,7 @@ struct se_portal_group {
 	bool			enabled;
 	/* RELATIVE TARGET PORT IDENTIFIER */
 	u16			tpg_rtpi;
+	bool			rtpi_manual;
 	/* Used for PR SPEC_I_PT=1 and REGISTER_AND_MOVE */
 	atomic_t		tpg_pr_ref_count;
 	/* Spinlock for adding/removing ACLed Nodes */