target/configfs: Kill se_device->dev_link_magic

Instead of using a hardcoded magic value in se_device when verifying
a target config_item symlink source during target_fabric_port_link(),
go ahead and use target_core_dev_item_ops directly instead.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Mike Christie <mchristi@redhat.com>
Cc: Hannes Reinecke <hare@suse.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_configfs.c

@@ -2236,7 +2236,11 @@ static void target_core_dev_release(struct config_item *item)
 	target_free_device(dev);
 }
 
-static struct configfs_item_operations target_core_dev_item_ops = {
+/*
+ * Used in target_core_fabric_configfs.c to verify valid se_device symlink
+ * within target_fabric_port_link()
+ */
+struct configfs_item_operations target_core_dev_item_ops = {
 	.release		= target_core_dev_release,
 };
 

drivers/target/target_core_device.c

@@ -756,7 +756,6 @@ struct se_device *target_alloc_device(struct se_hba *hba, const char *name)
 	if (!dev)
 		return NULL;
 
-	dev->dev_link_magic = SE_DEV_LINK_MAGIC;
 	dev->se_hba = hba;
 	dev->transport = hba->backend->ops;
 	dev->prot_length = sizeof(struct t10_pi_tuple);

drivers/target/target_core_fabric_configfs.c

@@ -620,6 +620,8 @@ static struct configfs_attribute *target_fabric_port_attrs[] = {
 	NULL,
 };
 
+extern struct configfs_item_operations target_core_dev_item_ops;
+
 static int target_fabric_port_link(
 	struct config_item *lun_ci,
 	struct config_item *se_dev_ci)
@@ -628,16 +630,16 @@ static int target_fabric_port_link(
 	struct se_lun *lun = container_of(to_config_group(lun_ci),
 				struct se_lun, lun_group);
 	struct se_portal_group *se_tpg;
-	struct se_device *dev =
-		container_of(to_config_group(se_dev_ci), struct se_device, dev_group);
+	struct se_device *dev;
 	struct target_fabric_configfs *tf;
 	int ret;
 
-	if (dev->dev_link_magic != SE_DEV_LINK_MAGIC) {
-		pr_err("Bad dev->dev_link_magic, not a valid se_dev_ci pointer:"
-			" %p to struct se_device: %p\n", se_dev_ci, dev);
+	if (!se_dev_ci->ci_type ||
+	    se_dev_ci->ci_type->ct_item_ops != &target_core_dev_item_ops) {
+		pr_err("Bad se_dev_ci, not a valid se_dev_ci pointer: %p\n", se_dev_ci);
 		return -EFAULT;
 	}
+	dev = container_of(to_config_group(se_dev_ci), struct se_device, dev_group);
 
 	if (!(dev->dev_flags & DF_CONFIGURED)) {
 		pr_err("se_device not configured yet, cannot port link\n");

include/target/target_core_base.h

@@ -746,8 +746,6 @@ struct se_dev_stat_grps {
 };
 
 struct se_device {
-#define SE_DEV_LINK_MAGIC			0xfeeddeef
-	u32			dev_link_magic;
 	/* RELATIVE TARGET PORT IDENTIFER Counter */
 	u16			dev_rpti_counter;
 	/* Used for SAM Task Attribute ordering */