target: Add device attribute to expose config_item_name for INQUIRY model

This patch changes LIO to use the configfs backend device name as the
model if you echo '1' to an individual device's emulate_model_alias attribute.
This is a valid operation only on devices with an export count of 0.

Signed-off-by: Tregaron Bayly <tbayly@bluehost.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_configfs.c

@@ -609,6 +609,9 @@ static struct target_core_dev_attrib_attribute				\
 	__CONFIGFS_EATTR_RO(_name,					\
 	target_core_dev_show_attr_##_name);
 
+DEF_DEV_ATTRIB(emulate_model_alias);
+SE_DEV_ATTR(emulate_model_alias, S_IRUGO | S_IWUSR);
+
 DEF_DEV_ATTRIB(emulate_dpo);
 SE_DEV_ATTR(emulate_dpo, S_IRUGO | S_IWUSR);
 
@@ -681,6 +684,7 @@ SE_DEV_ATTR(max_write_same_len, S_IRUGO | S_IWUSR);
 CONFIGFS_EATTR_OPS(target_core_dev_attrib, se_dev_attrib, da_group);
 
 static struct configfs_attribute *target_core_dev_attrib_attrs[] = {
+	&target_core_dev_attrib_emulate_model_alias.attr,
 	&target_core_dev_attrib_emulate_dpo.attr,
 	&target_core_dev_attrib_emulate_fua_write.attr,
 	&target_core_dev_attrib_emulate_fua_read.attr,

drivers/target/target_core_device.c

@@ -713,6 +713,44 @@ int se_dev_set_max_write_same_len(
 	return 0;
 }
 
+static void dev_set_t10_wwn_model_alias(struct se_device *dev)
+{
+	const char *configname;
+
+	configname = config_item_name(&dev->dev_group.cg_item);
+	if (strlen(configname) >= 16) {
+		pr_warn("dev[%p]: Backstore name '%s' is too long for "
+			"INQUIRY_MODEL, truncating to 16 bytes\n", dev,
+			configname);
+	}
+	snprintf(&dev->t10_wwn.model[0], 16, "%s", configname);
+}
+
+int se_dev_set_emulate_model_alias(struct se_device *dev, int flag)
+{
+	if (dev->export_count) {
+		pr_err("dev[%p]: Unable to change model alias"
+			" while export_count is %d\n",
+			dev, dev->export_count);
+			return -EINVAL;
+	}
+
+	if (flag != 0 && flag != 1) {
+		pr_err("Illegal value %d\n", flag);
+		return -EINVAL;
+	}
+
+	if (flag) {
+		dev_set_t10_wwn_model_alias(dev);
+	} else {
+		strncpy(&dev->t10_wwn.model[0],
+			dev->transport->inquiry_prod, 16);
+	}
+	dev->dev_attrib.emulate_model_alias = flag;
+
+	return 0;
+}
+
 int se_dev_set_emulate_dpo(struct se_device *dev, int flag)
 {
 	if (flag != 0 && flag != 1) {
@@ -1396,6 +1434,7 @@ struct se_device *target_alloc_device(struct se_hba *hba, const char *name)
 	dev->t10_alua.t10_dev = dev;
 
 	dev->dev_attrib.da_dev = dev;
+	dev->dev_attrib.emulate_model_alias = DA_EMULATE_MODEL_ALIAS;
 	dev->dev_attrib.emulate_dpo = DA_EMULATE_DPO;
 	dev->dev_attrib.emulate_fua_write = DA_EMULATE_FUA_WRITE;
 	dev->dev_attrib.emulate_fua_read = DA_EMULATE_FUA_READ;

drivers/target/target_core_internal.h

@@ -25,6 +25,7 @@ int	se_dev_set_max_unmap_block_desc_count(struct se_device *, u32);
 int	se_dev_set_unmap_granularity(struct se_device *, u32);
 int	se_dev_set_unmap_granularity_alignment(struct se_device *, u32);
 int	se_dev_set_max_write_same_len(struct se_device *, u32);
+int	se_dev_set_emulate_model_alias(struct se_device *, int);
 int	se_dev_set_emulate_dpo(struct se_device *, int);
 int	se_dev_set_emulate_fua_write(struct se_device *, int);
 int	se_dev_set_emulate_fua_read(struct se_device *, int);

include/target/target_core_base.h

@@ -75,6 +75,8 @@
 #define DA_MAX_WRITE_SAME_LEN			0
 /* Default max transfer length */
 #define DA_FABRIC_MAX_SECTORS			8192
+/* Use a model alias based on the configfs backend device name */
+#define DA_EMULATE_MODEL_ALIAS			0
 /* Emulation for Direct Page Out */
 #define DA_EMULATE_DPO				0
 /* Emulation for Forced Unit Access WRITEs */
@@ -591,6 +593,7 @@ struct se_dev_entry {
 };
 
 struct se_dev_attrib {
+	int		emulate_model_alias;
 	int		emulate_dpo;
 	int		emulate_fua_write;
 	int		emulate_fua_read;