init: handle ubi/mtd root mounting like all other root types

Assign a Root_Generic magic value for UBI/MTD root and handle the root
mounting in mount_root like all other root types.  Besides making the
code more clear this also means that UBI/MTD root can be used together
with an initrd (not that anyone should care).

Also factor parsing of the root name into a helper now that it can
be easily done and will get more complicated with subsequent patches.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230531125535.676098-11-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/include/linux/root_dev.h b/include/linux/root_dev.h
index ed3ea8d..847c9a0 100644 (file)
--- a/include/linux/root_dev.h
+++ b/include/linux/root_dev.h
@@ -9,6 +9,7 @@
 enum {
        Root_NFS = MKDEV(UNNAMED_MAJOR, 255),
        Root_CIFS = MKDEV(UNNAMED_MAJOR, 254),
+       Root_Generic = MKDEV(UNNAMED_MAJOR, 253),
        Root_RAM0 = MKDEV(RAMDISK_MAJOR, 0),
 };
 

diff --git a/init/do_mounts.c b/init/do_mounts.c
index 74cc96b..be6d147 100644 (file)
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -591,6 +591,10 @@ void __init mount_root(char *root_device_name)
        case Root_CIFS:
                mount_cifs_root();
                break;
+       case Root_Generic:
+               mount_root_generic(root_device_name, root_device_name,
+                                  root_mountflags);
+               break;
        case 0:
                if (root_device_name && root_fs_names &&
                    mount_nodev_root(root_device_name) == 0)
@@ -602,6 +606,14 @@ void __init mount_root(char *root_device_name)
        }
 }
 
+static dev_t __init parse_root_device(char *root_device_name)
+{
+       if (!strncmp(root_device_name, "mtd", 3) ||
+           !strncmp(root_device_name, "ubi", 3))
+               return Root_Generic;
+       return name_to_dev_t(root_device_name);
+}
+
 /*
  * Prepare the namespace - decide what/where to mount, load ramdisks, etc.
  */
@@ -624,15 +636,8 @@ void __init prepare_namespace(void)
 
        md_run_setup();
 
-       if (saved_root_name[0]) {
-               if (!strncmp(saved_root_name, "mtd", 3) ||
-                   !strncmp(saved_root_name, "ubi", 3)) {
-                       mount_root_generic(saved_root_name, saved_root_name,
-                                          root_mountflags);
-                       goto out;
-               }
-               ROOT_DEV = name_to_dev_t(saved_root_name);
-       }
+       if (saved_root_name[0])
+               ROOT_DEV = parse_root_device(saved_root_name);
 
        if (initrd_load(saved_root_name))
                goto out;