nvmet: return a specified error it subsys_alloc fails

nvmet_subsys_alloc() returns its pointer or NULL if it fails.  We can
see three different steps in this function:
  1. memory allocation
  2. argument check
  3. memory allocation for string

But now the callers of this function do not seem to handle case 2 by
returning -ENOMEM only even if it fails with an invalid parameter.

This patch specifies error codes so that caller can pass it to its own
caller.
Signed-off-by: Minwoo Im <minwoo.im.dev@gmail.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>.
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/target/configfs.c

@@ -898,8 +898,8 @@ static struct config_group *nvmet_subsys_make(struct config_group *group,
 	}
 
 	subsys = nvmet_subsys_alloc(name, NVME_NQN_NVME);
-	if (!subsys)
-		return ERR_PTR(-ENOMEM);
+	if (IS_ERR(subsys))
+		return ERR_CAST(subsys);
 
 	config_group_init_type_name(&subsys->group, name, &nvmet_subsys_type);
 

drivers/nvme/target/core.c

@@ -1367,7 +1367,7 @@ struct nvmet_subsys *nvmet_subsys_alloc(const char *subsysnqn,
 
 	subsys = kzalloc(sizeof(*subsys), GFP_KERNEL);
 	if (!subsys)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	subsys->ver = NVME_VS(1, 3, 0); /* NVMe 1.3.0 */
 	/* generate a random serial number as our controllers are ephemeral: */
@@ -1383,14 +1383,14 @@ struct nvmet_subsys *nvmet_subsys_alloc(const char *subsysnqn,
 	default:
 		pr_err("%s: Unknown Subsystem type - %d\n", __func__, type);
 		kfree(subsys);
-		return NULL;
+		return ERR_PTR(-EINVAL);
 	}
 	subsys->type = type;
 	subsys->subsysnqn = kstrndup(subsysnqn, NVMF_NQN_SIZE,
 			GFP_KERNEL);
 	if (!subsys->subsysnqn) {
 		kfree(subsys);
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 	}
 
 	kref_init(&subsys->ref);

drivers/nvme/target/discovery.c

@@ -372,8 +372,8 @@ int __init nvmet_init_discovery(void)
 {
 	nvmet_disc_subsys =
 		nvmet_subsys_alloc(NVME_DISC_SUBSYS_NAME, NVME_NQN_DISC);
-	if (!nvmet_disc_subsys)
-		return -ENOMEM;
+	if (IS_ERR(nvmet_disc_subsys))
+		return PTR_ERR(nvmet_disc_subsys);
 	return 0;
 }