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don't bother with registering rootfs 

init_mount_tree() can get to rootfs_fs_type directly and that simplifies
a lot of things.  We don't need to register it, we don't need to look
it up *and* we don't need to bother with preventing subsequent userland
mounts.  That's the way we should've done that from the very beginning.

There is a user-visible change, namely the disappearance of "rootfs"
from /proc/filesystems.  Note that it's been unmountable all along
and it didn't show up in /proc/mounts; however, it *is* a user-visible
change and theoretically some script might've been using its presence
in /proc/filesystems to tell 2.4.11+ from earlier kernels.

*IF* any complaints about behaviour change do show up, we could fake
it in /proc/filesystems.  I very much doubt we'll have to, though.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2019-05-30 17:48:35 -04:00
parent 14a253ce42
commit fd3e007f6c
3 changed files with 6 additions and 19 deletions
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7
fs/namespace.c
View File

@ -3686,13 +3686,8 @@ static void __init init_mount_tree(void)
struct mount *m; struct mount *m;
struct mnt_namespace *ns; struct mnt_namespace *ns;
struct path root; struct path root;
struct file_system_type *type;
type = get_fs_type("rootfs"); mnt = vfs_kern_mount(&rootfs_fs_type, 0, "rootfs", NULL);
if (!type)
panic("Can't find rootfs type");
mnt = vfs_kern_mount(type, 0, "rootfs", NULL);
put_filesystem(type);
if (IS_ERR(mnt)) if (IS_ERR(mnt))
panic("Can't create rootfs"); panic("Can't create rootfs");

3
include/linux/init.h
View File

@ -137,6 +137,8 @@ extern initcall_entry_t __con_initcall_start[], __con_initcall_end[];
/* Used for contructor calls. */ /* Used for contructor calls. */
typedef void (*ctor_fn_t)(void); typedef void (*ctor_fn_t)(void);
struct file_system_type;
/* Defined in init/main.c */ /* Defined in init/main.c */
extern int do_one_initcall(initcall_t fn); extern int do_one_initcall(initcall_t fn);
extern char __initdata boot_command_line[]; extern char __initdata boot_command_line[];
@ -147,6 +149,7 @@ extern unsigned int reset_devices;
void setup_arch(char **); void setup_arch(char **);
void prepare_namespace(void); void prepare_namespace(void);
int __init init_rootfs(void); int __init init_rootfs(void);
extern struct file_system_type rootfs_fs_type;
#if defined(CONFIG_STRICT_KERNEL_RWX) || defined(CONFIG_STRICT_MODULE_RWX) #if defined(CONFIG_STRICT_KERNEL_RWX) || defined(CONFIG_STRICT_MODULE_RWX)
extern bool rodata_enabled; extern bool rodata_enabled;

15
init/do_mounts.c
View File

@ -629,19 +629,15 @@ static bool is_tmpfs;
static struct dentry *rootfs_mount(struct file_system_type *fs_type, static struct dentry *rootfs_mount(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data) int flags, const char *dev_name, void *data)
{ {
static unsigned long once;
void *fill = ramfs_fill_super; void *fill = ramfs_fill_super;
if (test_and_set_bit(0, &once))
return ERR_PTR(-ENODEV);
if (IS_ENABLED(CONFIG_TMPFS) && is_tmpfs) if (IS_ENABLED(CONFIG_TMPFS) && is_tmpfs)
fill = shmem_fill_super; fill = shmem_fill_super;
return mount_nodev(fs_type, flags, data, fill); return mount_nodev(fs_type, flags, data, fill);
} }
static struct file_system_type rootfs_fs_type = { struct file_system_type rootfs_fs_type = {
.name = "rootfs", .name = "rootfs",
.mount = rootfs_mount, .mount = rootfs_mount,
.kill_sb = kill_litter_super, .kill_sb = kill_litter_super,
@ -649,19 +645,12 @@ static struct file_system_type rootfs_fs_type = {
int __init init_rootfs(void) int __init init_rootfs(void)
{ {
int err = register_filesystem(&rootfs_fs_type); int err = 0;
if (err)
return err;
if (IS_ENABLED(CONFIG_TMPFS) && !saved_root_name[0] && if (IS_ENABLED(CONFIG_TMPFS) && !saved_root_name[0] &&
(!root_fs_names || strstr(root_fs_names, "tmpfs"))) { (!root_fs_names || strstr(root_fs_names, "tmpfs"))) {
err = shmem_init(); err = shmem_init();
is_tmpfs = true; is_tmpfs = true;
} }
if (err)
unregister_filesystem(&rootfs_fs_type);
return err; return err;
} }