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Commit 6e19eded authored by Rob Landley's avatar Rob Landley Committed by Linus Torvalds
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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: default avatarRob 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 16203a7a

Documentation/filesystems/ramfs-rootfs-initramfs.txt

+4 −0
Original line number Diff line number Diff line
@@ -79,6 +79,10 @@ to just make sure certain lists can't become empty. 
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?

------------------

init/do_mounts.c

+11 −4
Original line number Diff line number Diff line
@@ -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);