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>
diff --git a/Documentation/filesystems/ramfs-rootfs-initramfs.txt b/Documentation/filesystems/ramfs-rootfs-initramfs.txt
index 59b4a096..b176928 100644
--- a/Documentation/filesystems/ramfs-rootfs-initramfs.txt
+++ b/Documentation/filesystems/ramfs-rootfs-initramfs.txt
@@ -79,6 +79,10 @@
Most systems just mount another filesystem over rootfs and ignore it. The
amount of space an empty instance of ramfs takes up is tiny.
+If CONFIG_TMPFS is enabled, rootfs will use tmpfs instead of ramfs by
+default. To force ramfs, add "rootfstype=ramfs" to the kernel command
+line.
+
What is initramfs?
------------------
diff --git a/init/do_mounts.c b/init/do_mounts.c
index e27908b..a51cddc 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -591,16 +591,20 @@
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 @@
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);