init: refactor mount_root

Provide stubs for all the lower level mount helpers, and just switch
on ROOT_DEV in the main function.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230531125535.676098-8-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

init/do_mounts.c

@@ -453,15 +453,14 @@ void __init mount_root_generic(char *name, int flags)
 #define NFSROOT_TIMEOUT_MAX	30
 #define NFSROOT_RETRY_MAX	5
 
-static int __init mount_nfs_root(void)
+static void __init mount_nfs_root(void)
 {
 	char *root_dev, *root_data;
 	unsigned int timeout;
-	int try, err;
+	int try;
 
-	err = nfs_root_data(&root_dev, &root_data);
-	if (err != 0)
-		return 0;
+	if (nfs_root_data(&root_dev, &root_data))
+		goto fail;
 
 	/*
 	 * The server or network may not be ready, so try several
@@ -470,10 +469,8 @@ static int __init mount_nfs_root(void)
 	 */
 	timeout = NFSROOT_TIMEOUT_MIN;
 	for (try = 1; ; try++) {
-		err = do_mount_root(root_dev, "nfs",
-					root_mountflags, root_data);
-		if (err == 0)
-			return 1;
+		if (!do_mount_root(root_dev, "nfs", root_mountflags, root_data))
+			return;
 		if (try > NFSROOT_RETRY_MAX)
 			break;
 
@@ -483,9 +480,14 @@ static int __init mount_nfs_root(void)
 		if (timeout > NFSROOT_TIMEOUT_MAX)
 			timeout = NFSROOT_TIMEOUT_MAX;
 	}
-	return 0;
+fail:
+	pr_err("VFS: Unable to mount root fs via NFS.\n");
 }
-#endif
+#else
+static inline void mount_nfs_root(void)
+{
+}
+#endif /* CONFIG_ROOT_NFS */
 
 #ifdef CONFIG_CIFS_ROOT
 
@@ -495,22 +497,20 @@ extern int cifs_root_data(char **dev, char **opts);
 #define CIFSROOT_TIMEOUT_MAX	30
 #define CIFSROOT_RETRY_MAX	5
 
-static int __init mount_cifs_root(void)
+static void __init mount_cifs_root(void)
 {
 	char *root_dev, *root_data;
 	unsigned int timeout;
-	int try, err;
+	int try;
 
-	err = cifs_root_data(&root_dev, &root_data);
-	if (err != 0)
-		return 0;
+	if (cifs_root_data(&root_dev, &root_data))
+		goto fail;
 
 	timeout = CIFSROOT_TIMEOUT_MIN;
 	for (try = 1; ; try++) {
-		err = do_mount_root(root_dev, "cifs", root_mountflags,
-				    root_data);
-		if (err == 0)
-			return 1;
+		if (!do_mount_root(root_dev, "cifs", root_mountflags,
+				   root_data))
+			return;
 		if (try > CIFSROOT_RETRY_MAX)
 			break;
 
@@ -519,9 +519,14 @@ static int __init mount_cifs_root(void)
 		if (timeout > CIFSROOT_TIMEOUT_MAX)
 			timeout = CIFSROOT_TIMEOUT_MAX;
 	}
-	return 0;
+fail:
+	pr_err("VFS: Unable to mount root fs via SMB.\n");
 }
-#endif
+#else
+static inline void mount_cifs_root(void)
+{
+}
+#endif /* CONFIG_CIFS_ROOT */
 
 static bool __init fs_is_nodev(char *fstype)
 {
@@ -563,35 +568,38 @@ static int __init mount_nodev_root(void)
 	return err;
 }
 
-void __init mount_root(void)
-{
-#ifdef CONFIG_ROOT_NFS
-	if (ROOT_DEV == Root_NFS) {
-		if (!mount_nfs_root())
-			printk(KERN_ERR "VFS: Unable to mount root fs via NFS.\n");
-		return;
-	}
-#endif
-#ifdef CONFIG_CIFS_ROOT
-	if (ROOT_DEV == Root_CIFS) {
-		if (!mount_cifs_root())
-			printk(KERN_ERR "VFS: Unable to mount root fs via SMB.\n");
-		return;
-	}
-#endif
-	if (ROOT_DEV == 0 && root_device_name && root_fs_names) {
-		if (mount_nodev_root() == 0)
-			return;
-	}
 #ifdef CONFIG_BLOCK
-	{
-		int err = create_dev("/dev/root", ROOT_DEV);
+static void __init mount_block_root(void)
+{
+	int err = create_dev("/dev/root", ROOT_DEV);
+
+	if (err < 0)
+		pr_emerg("Failed to create /dev/root: %d\n", err);
+	mount_root_generic("/dev/root", root_mountflags);
+}
+#else
+static inline void mount_block_root(void)
+{
+}
+#endif /* CONFIG_BLOCK */
 
-		if (err < 0)
-			pr_emerg("Failed to create /dev/root: %d\n", err);
-		mount_root_generic("/dev/root", root_mountflags);
+void __init mount_root(void)
+{
+	switch (ROOT_DEV) {
+	case Root_NFS:
+		mount_nfs_root();
+		break;
+	case Root_CIFS:
+		mount_cifs_root();
+		break;
+	case 0:
+		if (root_device_name && root_fs_names && mount_nodev_root() == 0)
+			break;
+		fallthrough;
+	default:
+		mount_block_root();
+		break;
 	}
-#endif
 }
 
 /*