initmpfs: use initramfs if rootfstype= or root= specified

Command line option rootfstype=ramfs to obtain old initramfs behavior, and
use ramfs instead of tmpfs for stub when root= defined (for cosmetic
reasons).

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Rob Landley <rob@landley.net>
Cc: Jeff Layton <jlayton@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jim Cromie <jim.cromie@gmail.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 11 insertions, 4 deletions

diff --git a/init/do_mounts.c b/init/do_mounts.c
index e27908b949d4..a51cddc2ff8c 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -591,16 +591,20 @@ out:
         sys_chroot(".");
 }
 
+static bool is_tmpfs;
 static struct dentry *rootfs_mount(struct file_system_type *fs_type,
         int flags, const char *dev_name, void *data)
 {
         static unsigned long once;
+        void *fill = ramfs_fill_super;
 
         if (test_and_set_bit(0, &once))
                 return ERR_PTR(-ENODEV);
 
-        return mount_nodev(fs_type, flags, data,
-                IS_ENABLED(CONFIG_TMPFS) ? shmem_fill_super : ramfs_fill_super);
+        if (IS_ENABLED(CONFIG_TMPFS) && is_tmpfs)
+                fill = shmem_fill_super;
+
+        return mount_nodev(fs_type, flags, data, fill);
 }
 
 static struct file_system_type rootfs_fs_type = {
@@ -616,10 +620,13 @@ int __init init_rootfs(void)
         if (err)
                 return err;
 
-        if (IS_ENABLED(CONFIG_TMPFS))
+        if (IS_ENABLED(CONFIG_TMPFS) && !saved_root_name[0] &&
+                (!root_fs_names || strstr(root_fs_names, "tmpfs"))) {
                 err = shmem_init();
-        else
+                is_tmpfs = true;
+        } else {
                 err = init_ramfs_fs();
+        }
 
         if (err)
                 unregister_filesystem(&rootfs_fs_type);