init/do_mounts.c - linux/kernel/git/hid/hid - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 #include <linux/module.h>
 #include <linux/sched.h>
 #include <linux/ctype.h>
 #include <linux/fd.h>
 #include <linux/tty.h>
 #include <linux/suspend.h>
 #include <linux/root_dev.h>
 #include <linux/security.h>
 #include <linux/delay.h>
 #include <linux/mount.h>
 #include <linux/device.h>
 #include <linux/init.h>
 #include <linux/fs.h>
 #include <linux/initrd.h>
 #include <linux/async.h>
 #include <linux/fs_struct.h>
 #include <linux/slab.h>
 #include <linux/ramfs.h>
 #include <linux/shmem_fs.h>
 #include <linux/ktime.h>

 #include <linux/nfs_fs.h>
 #include <linux/nfs_fs_sb.h>
 #include <linux/nfs_mount.h>
 #include <linux/raid/detect.h>
 #include <uapi/linux/mount.h>

 #include "do_mounts.h"

 int root_mountflags = MS_RDONLY | MS_SILENT;
 static char __initdata saved_root_name[64];
 static int root_wait;

 dev_t ROOT_DEV;

 static int __init load_ramdisk(char *str)
 {
 	pr_warn("ignoring the deprecated load_ramdisk= option\n");
 	return 1;
 }
 __setup("load_ramdisk=", load_ramdisk);

 static int __init readonly(char *str)
 {
 	if (*str)
 		return 0;
 	root_mountflags |= MS_RDONLY;
 	return 1;
 }

 static int __init readwrite(char *str)
 {
 	if (*str)
 		return 0;
 	root_mountflags &= ~MS_RDONLY;
 	return 1;
 }

 __setup("ro", readonly);
 __setup("rw", readwrite);

 static int __init root_dev_setup(char *line)
 {
 	strscpy(saved_root_name, line, sizeof(saved_root_name));
 	return 1;
 }

 __setup("root=", root_dev_setup);

 static int __init rootwait_setup(char *str)
 {
 	if (*str)
 		return 0;
 	root_wait = -1;
 	return 1;
 }

 __setup("rootwait", rootwait_setup);

 static int __init rootwait_timeout_setup(char *str)
 {
 	int sec;

 	if (kstrtoint(str, 0, &sec) || sec < 0) {
 		pr_warn("ignoring invalid rootwait value\n");
 		goto ignore;
 	}

 	if (check_mul_overflow(sec, MSEC_PER_SEC, &root_wait)) {
 		pr_warn("ignoring excessive rootwait value\n");
 		goto ignore;
 	}

 	return 1;

 ignore:
 	/* Fallback to indefinite wait */
 	root_wait = -1;

 	return 1;
 }

 __setup("rootwait=", rootwait_timeout_setup);

 static char * __initdata root_mount_data;
 static int __init root_data_setup(char *str)
 {
 	root_mount_data = str;
 	return 1;
 }

 static char * __initdata root_fs_names;
 static int __init fs_names_setup(char *str)
 {
 	root_fs_names = str;
 	return 1;
 }

 static unsigned int __initdata root_delay;
 static int __init root_delay_setup(char *str)
 {
 	root_delay = simple_strtoul(str, NULL, 0);
 	return 1;
 }

 __setup("rootflags=", root_data_setup);
 __setup("rootfstype=", fs_names_setup);
 __setup("rootdelay=", root_delay_setup);

 /* This can return zero length strings. Caller should check */
 static int __init split_fs_names(char *page, size_t size)
 {
 	int count = 1;
 	char *p = page;

 	strscpy(p, root_fs_names, size);
 	while (*p++) {
 		if (p[-1] == ',') {
 			p[-1] = '\0';
 			count++;
 		}
 	}

 	return count;
 }

 static int __init do_mount_root(const char *name, const char *fs,
 				 const int flags, const void *data)
 {
 	struct super_block *s;
 	struct page *p = NULL;
 	char *data_page = NULL;
 	int ret;

 	if (data) {
 		/* init_mount() requires a full page as fifth argument */
 		p = alloc_page(GFP_KERNEL);
 		if (!p)
 			return -ENOMEM;
 		data_page = page_address(p);
 		/* zero-pad. init_mount() will make sure it's terminated */
 		strncpy(data_page, data, PAGE_SIZE);
 	}

 	ret = init_mount(name, "/root", fs, flags, data_page);
 	if (ret)
 		goto out;

 	init_chdir("/root");
 	s = current->fs->pwd.dentry->d_sb;
 	ROOT_DEV = s->s_dev;
 	printk(KERN_INFO
 	       "VFS: Mounted root (%s filesystem)%s on device %u:%u.\n",
 	       s->s_type->name,
 	       sb_rdonly(s) ? " readonly" : "",
 	       MAJOR(ROOT_DEV), MINOR(ROOT_DEV));

 out:
 	if (p)
 		put_page(p);
 	return ret;
 }

 void __init mount_root_generic(char *name, char *pretty_name, int flags)
 {
 	struct page *page = alloc_page(GFP_KERNEL);
 	char *fs_names = page_address(page);
 	char *p;
 	char b[BDEVNAME_SIZE];
 	int num_fs, i;

 	scnprintf(b, BDEVNAME_SIZE, "unknown-block(%u,%u)",
 		  MAJOR(ROOT_DEV), MINOR(ROOT_DEV));
 	if (root_fs_names)
 		num_fs = split_fs_names(fs_names, PAGE_SIZE);
 	else
 		num_fs = list_bdev_fs_names(fs_names, PAGE_SIZE);
 retry:
 	for (i = 0, p = fs_names; i < num_fs; i++, p += strlen(p)+1) {
 		int err;

 		if (!*p)
 			continue;
 		err = do_mount_root(name, p, flags, root_mount_data);
 		switch (err) {
 			case 0:
 				goto out;
 			case -EACCES:
 			case -EINVAL:
 #ifdef CONFIG_BLOCK
 				init_flush_fput();
 #endif
 				continue;
 		}
 	        /*
 		 * Allow the user to distinguish between failed sys_open
 		 * and bad superblock on root device.
 		 * and give them a list of the available devices
 		 */
 		printk("VFS: Cannot open root device \"%s\" or %s: error %d\n",
 				pretty_name, b, err);
 		printk("Please append a correct \"root=\" boot option; here are the available partitions:\n");
 		printk_all_partitions();

 		if (root_fs_names)
 			num_fs = list_bdev_fs_names(fs_names, PAGE_SIZE);
 		if (!num_fs)
 			pr_err("Can't find any bdev filesystem to be used for mount!\n");
 		else {
 			pr_err("List of all bdev filesystems:\n");
 			for (i = 0, p = fs_names; i < num_fs; i++, p += strlen(p)+1)
 				pr_err(" %s", p);
 			pr_err("\n");
 		}

 		panic("VFS: Unable to mount root fs on %s", b);
 	}
 	if (!(flags & SB_RDONLY)) {
 		flags |= SB_RDONLY;
 		goto retry;
 	}

 	printk("List of all partitions:\n");
 	printk_all_partitions();
 	printk("No filesystem could mount root, tried: ");
 	for (i = 0, p = fs_names; i < num_fs; i++, p += strlen(p)+1)
 		printk(" %s", p);
 	printk("\n");
 	panic("VFS: Unable to mount root fs on \"%s\" or %s", pretty_name, b);
 out:
 	put_page(page);
 }

 #ifdef CONFIG_ROOT_NFS

 #define NFSROOT_TIMEOUT_MIN	5
 #define NFSROOT_TIMEOUT_MAX	30
 #define NFSROOT_RETRY_MAX	5

 static void __init mount_nfs_root(void)
 {
 	char *root_dev, *root_data;
 	unsigned int timeout;
 	int try;

 	if (nfs_root_data(&root_dev, &root_data))
 		goto fail;

 	/*
 	 * The server or network may not be ready, so try several
 	 * times.  Stop after a few tries in case the client wants
 	 * to fall back to other boot methods.
 	 */
 	timeout = NFSROOT_TIMEOUT_MIN;
 	for (try = 1; ; try++) {
 		if (!do_mount_root(root_dev, "nfs", root_mountflags, root_data))
 			return;
 		if (try > NFSROOT_RETRY_MAX)
 			break;

 		/* Wait, in case the server refused us immediately */
 		ssleep(timeout);
 		timeout <<= 1;
 		if (timeout > NFSROOT_TIMEOUT_MAX)
 			timeout = NFSROOT_TIMEOUT_MAX;
 	}
 fail:
 	pr_err("VFS: Unable to mount root fs via NFS.\n");
 }
 #else
 static inline void mount_nfs_root(void)
 {
 }
 #endif /* CONFIG_ROOT_NFS */

 #ifdef CONFIG_CIFS_ROOT

 #define CIFSROOT_TIMEOUT_MIN	5
 #define CIFSROOT_TIMEOUT_MAX	30
 #define CIFSROOT_RETRY_MAX	5

 static void __init mount_cifs_root(void)
 {
 	char *root_dev, *root_data;
 	unsigned int timeout;
 	int try;

 	if (cifs_root_data(&root_dev, &root_data))
 		goto fail;

 	timeout = CIFSROOT_TIMEOUT_MIN;
 	for (try = 1; ; try++) {
 		if (!do_mount_root(root_dev, "cifs", root_mountflags,
 				   root_data))
 			return;
 		if (try > CIFSROOT_RETRY_MAX)
 			break;

 		ssleep(timeout);
 		timeout <<= 1;
 		if (timeout > CIFSROOT_TIMEOUT_MAX)
 			timeout = CIFSROOT_TIMEOUT_MAX;
 	}
 fail:
 	pr_err("VFS: Unable to mount root fs via SMB.\n");
 }
 #else
 static inline void mount_cifs_root(void)
 {
 }
 #endif /* CONFIG_CIFS_ROOT */

 static bool __init fs_is_nodev(char *fstype)
 {
 	struct file_system_type *fs = get_fs_type(fstype);
 	bool ret = false;

 	if (fs) {
 		ret = !(fs->fs_flags & FS_REQUIRES_DEV);
 		put_filesystem(fs);
 	}

 	return ret;
 }

 static int __init mount_nodev_root(char *root_device_name)
 {
 	char *fs_names, *fstype;
 	int err = -EINVAL;
 	int num_fs, i;

 	fs_names = (void *)__get_free_page(GFP_KERNEL);
 	if (!fs_names)
 		return -EINVAL;
 	num_fs = split_fs_names(fs_names, PAGE_SIZE);

 	for (i = 0, fstype = fs_names; i < num_fs;
 	     i++, fstype += strlen(fstype) + 1) {
 		if (!*fstype)
 			continue;
 		if (!fs_is_nodev(fstype))
 			continue;
 		err = do_mount_root(root_device_name, fstype, root_mountflags,
 				    root_mount_data);
 		if (!err)
 			break;
 	}

 	free_page((unsigned long)fs_names);
 	return err;
 }

 #ifdef CONFIG_BLOCK
 static void __init mount_block_root(char *root_device_name)
 {
 	int err = create_dev("/dev/root", ROOT_DEV);

 	if (err < 0)
 		pr_emerg("Failed to create /dev/root: %d\n", err);
 	mount_root_generic("/dev/root", root_device_name, root_mountflags);
 }
 #else
 static inline void mount_block_root(char *root_device_name)
 {
 }
 #endif /* CONFIG_BLOCK */

 void __init mount_root(char *root_device_name)
 {
 	switch (ROOT_DEV) {
 	case Root_NFS:
 		mount_nfs_root();
 		break;
 	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)
 			break;
 		fallthrough;
 	default:
 		mount_block_root(root_device_name);
 		break;
 	}
 }

 /* wait for any asynchronous scanning to complete */
 static void __init wait_for_root(char *root_device_name)
 {
 	ktime_t end;

 	if (ROOT_DEV != 0)
 		return;

 	pr_info("Waiting for root device %s...\n", root_device_name);

 	end = ktime_add_ms(ktime_get_raw(), root_wait);

 	while (!driver_probe_done() ||
 	       early_lookup_bdev(root_device_name, &ROOT_DEV) < 0) {
 		msleep(5);
 		if (root_wait > 0 && ktime_after(ktime_get_raw(), end))
 			break;
 	}

 	async_synchronize_full();

 }

 static dev_t __init parse_root_device(char *root_device_name)
 {
 	int error;
 	dev_t dev;

 	if (!strncmp(root_device_name, "mtd", 3) ||
 	    !strncmp(root_device_name, "ubi", 3))
 		return Root_Generic;
 	if (strcmp(root_device_name, "/dev/nfs") == 0)
 		return Root_NFS;
 	if (strcmp(root_device_name, "/dev/cifs") == 0)
 		return Root_CIFS;
 	if (strcmp(root_device_name, "/dev/ram") == 0)
 		return Root_RAM0;

 	error = early_lookup_bdev(root_device_name, &dev);
 	if (error) {
 		if (error == -EINVAL && root_wait) {
 			pr_err("Disabling rootwait; root= is invalid.\n");
 			root_wait = 0;
 		}
 		return 0;
 	}
 	return dev;
 }

 /*
  * Prepare the namespace - decide what/where to mount, load ramdisks, etc.
  */
 void __init prepare_namespace(void)
 {
 	if (root_delay) {
 		printk(KERN_INFO "Waiting %d sec before mounting root device...\n",
 		       root_delay);
 		ssleep(root_delay);
 	}

 	/*
 	 * wait for the known devices to complete their probing
 	 *
 	 * Note: this is a potential source of long boot delays.
 	 * For example, it is not atypical to wait 5 seconds here
 	 * for the touchpad of a laptop to initialize.
 	 */
 	wait_for_device_probe();

 	md_run_setup();

 	if (saved_root_name[0])
 		ROOT_DEV = parse_root_device(saved_root_name);

 	if (initrd_load(saved_root_name))
 		goto out;

 	if (root_wait)
 		wait_for_root(saved_root_name);
 	mount_root(saved_root_name);
 out:
 	devtmpfs_mount();
 	init_mount(".", "/", NULL, MS_MOVE, NULL);
 	init_chroot(".");
 }

 static bool is_tmpfs;
 static int rootfs_init_fs_context(struct fs_context *fc)
 {
 	if (IS_ENABLED(CONFIG_TMPFS) && is_tmpfs)
 		return shmem_init_fs_context(fc);

 	return ramfs_init_fs_context(fc);
 }

 struct file_system_type rootfs_fs_type = {
 	.name		= "rootfs",
 	.init_fs_context = rootfs_init_fs_context,
 	.kill_sb	= kill_litter_super,
 };

 void __init init_rootfs(void)
 {
 	if (IS_ENABLED(CONFIG_TMPFS)) {
 		if (!saved_root_name[0] && !root_fs_names)
 			is_tmpfs = true;
 		else if (root_fs_names && !!strstr(root_fs_names, "tmpfs"))
 			is_tmpfs = true;
 	}
 }
	// SPDX-License-Identifier: GPL-2.0-only
	#include <linux/module.h>
	#include <linux/sched.h>
	#include <linux/ctype.h>
	#include <linux/fd.h>
	#include <linux/tty.h>
	#include <linux/suspend.h>
	#include <linux/root_dev.h>
	#include <linux/security.h>
	#include <linux/delay.h>
	#include <linux/mount.h>
	#include <linux/device.h>
	#include <linux/init.h>
	#include <linux/fs.h>
	#include <linux/initrd.h>
	#include <linux/async.h>
	#include <linux/fs_struct.h>
	#include <linux/slab.h>
	#include <linux/ramfs.h>
	#include <linux/shmem_fs.h>
	#include <linux/ktime.h>

	#include <linux/nfs_fs.h>
	#include <linux/nfs_fs_sb.h>
	#include <linux/nfs_mount.h>
	#include <linux/raid/detect.h>
	#include <uapi/linux/mount.h>

	#include "do_mounts.h"

	int root_mountflags = MS_RDONLY \| MS_SILENT;
	static char __initdata saved_root_name[64];
	static int root_wait;

	dev_t ROOT_DEV;

	static int __init load_ramdisk(char *str)
	{
	pr_warn("ignoring the deprecated load_ramdisk= option\n");
	return 1;
	}
	__setup("load_ramdisk=", load_ramdisk);

	static int __init readonly(char *str)
	{
	if (*str)
	return 0;
	root_mountflags \|= MS_RDONLY;
	return 1;
	}

	static int __init readwrite(char *str)
	{
	if (*str)
	return 0;
	root_mountflags &= ~MS_RDONLY;
	return 1;
	}

	__setup("ro", readonly);
	__setup("rw", readwrite);

	static int __init root_dev_setup(char *line)
	{
	strscpy(saved_root_name, line, sizeof(saved_root_name));
	return 1;
	}

	__setup("root=", root_dev_setup);

	static int __init rootwait_setup(char *str)
	{
	if (*str)
	return 0;
	root_wait = -1;
	return 1;
	}

	__setup("rootwait", rootwait_setup);

	static int __init rootwait_timeout_setup(char *str)
	{
	int sec;

	if (kstrtoint(str, 0, &sec) \|\| sec < 0) {
	pr_warn("ignoring invalid rootwait value\n");
	goto ignore;
	}

	if (check_mul_overflow(sec, MSEC_PER_SEC, &root_wait)) {
	pr_warn("ignoring excessive rootwait value\n");
	goto ignore;
	}

	return 1;

	ignore:
	/* Fallback to indefinite wait */
	root_wait = -1;

	return 1;
	}

	__setup("rootwait=", rootwait_timeout_setup);

	static char * __initdata root_mount_data;
	static int __init root_data_setup(char *str)
	{
	root_mount_data = str;
	return 1;
	}

	static char * __initdata root_fs_names;
	static int __init fs_names_setup(char *str)
	{
	root_fs_names = str;
	return 1;
	}

	static unsigned int __initdata root_delay;
	static int __init root_delay_setup(char *str)
	{
	root_delay = simple_strtoul(str, NULL, 0);
	return 1;
	}

	__setup("rootflags=", root_data_setup);
	__setup("rootfstype=", fs_names_setup);
	__setup("rootdelay=", root_delay_setup);

	/* This can return zero length strings. Caller should check */
	static int __init split_fs_names(char *page, size_t size)
	{
	int count = 1;
	char *p = page;

	strscpy(p, root_fs_names, size);
	while (*p++) {
	if (p[-1] == ',') {
	p[-1] = '\0';
	count++;
	}
	}

	return count;
	}

	static int __init do_mount_root(const char name, const char fs,
	const int flags, const void *data)
	{
	struct super_block *s;
	struct page *p = NULL;
	char *data_page = NULL;
	int ret;

	if (data) {
	/* init_mount() requires a full page as fifth argument */
	p = alloc_page(GFP_KERNEL);
	if (!p)
	return -ENOMEM;
	data_page = page_address(p);
	/* zero-pad. init_mount() will make sure it's terminated */
	strncpy(data_page, data, PAGE_SIZE);
	}

	ret = init_mount(name, "/root", fs, flags, data_page);
	if (ret)
	goto out;

	init_chdir("/root");
	s = current->fs->pwd.dentry->d_sb;
	ROOT_DEV = s->s_dev;
	printk(KERN_INFO
	"VFS: Mounted root (%s filesystem)%s on device %u:%u.\n",
	s->s_type->name,
	sb_rdonly(s) ? " readonly" : "",
	MAJOR(ROOT_DEV), MINOR(ROOT_DEV));

	out:
	if (p)
	put_page(p);
	return ret;
	}

	void __init mount_root_generic(char name, char pretty_name, int flags)
	{
	struct page *page = alloc_page(GFP_KERNEL);
	char *fs_names = page_address(page);
	char *p;
	char b[BDEVNAME_SIZE];
	int num_fs, i;

	scnprintf(b, BDEVNAME_SIZE, "unknown-block(%u,%u)",
	MAJOR(ROOT_DEV), MINOR(ROOT_DEV));
	if (root_fs_names)
	num_fs = split_fs_names(fs_names, PAGE_SIZE);
	else
	num_fs = list_bdev_fs_names(fs_names, PAGE_SIZE);
	retry:
	for (i = 0, p = fs_names; i < num_fs; i++, p += strlen(p)+1) {
	int err;

	if (!*p)
	continue;
	err = do_mount_root(name, p, flags, root_mount_data);
	switch (err) {
	case 0:
	goto out;
	case -EACCES:
	case -EINVAL:
	#ifdef CONFIG_BLOCK
	init_flush_fput();
	#endif
	continue;
	}
	/*
	* Allow the user to distinguish between failed sys_open
	* and bad superblock on root device.
	* and give them a list of the available devices
	*/
	printk("VFS: Cannot open root device \"%s\" or %s: error %d\n",
	pretty_name, b, err);
	printk("Please append a correct \"root=\" boot option; here are the available partitions:\n");
	printk_all_partitions();

	if (root_fs_names)
	num_fs = list_bdev_fs_names(fs_names, PAGE_SIZE);
	if (!num_fs)
	pr_err("Can't find any bdev filesystem to be used for mount!\n");
	else {
	pr_err("List of all bdev filesystems:\n");
	for (i = 0, p = fs_names; i < num_fs; i++, p += strlen(p)+1)
	pr_err(" %s", p);
	pr_err("\n");
	}

	panic("VFS: Unable to mount root fs on %s", b);
	}
	if (!(flags & SB_RDONLY)) {
	flags \|= SB_RDONLY;
	goto retry;
	}

	printk("List of all partitions:\n");
	printk_all_partitions();
	printk("No filesystem could mount root, tried: ");
	for (i = 0, p = fs_names; i < num_fs; i++, p += strlen(p)+1)
	printk(" %s", p);
	printk("\n");
	panic("VFS: Unable to mount root fs on \"%s\" or %s", pretty_name, b);
	out:
	put_page(page);
	}

	#ifdef CONFIG_ROOT_NFS

	#define NFSROOT_TIMEOUT_MIN 5
	#define NFSROOT_TIMEOUT_MAX 30
	#define NFSROOT_RETRY_MAX 5

	static void __init mount_nfs_root(void)
	{
	char root_dev, root_data;
	unsigned int timeout;
	int try;

	if (nfs_root_data(&root_dev, &root_data))
	goto fail;

	/*
	* The server or network may not be ready, so try several
	* times. Stop after a few tries in case the client wants
	* to fall back to other boot methods.
	*/
	timeout = NFSROOT_TIMEOUT_MIN;
	for (try = 1; ; try++) {
	if (!do_mount_root(root_dev, "nfs", root_mountflags, root_data))
	return;
	if (try > NFSROOT_RETRY_MAX)
	break;

	/* Wait, in case the server refused us immediately */
	ssleep(timeout);
	timeout <<= 1;
	if (timeout > NFSROOT_TIMEOUT_MAX)
	timeout = NFSROOT_TIMEOUT_MAX;
	}
	fail:
	pr_err("VFS: Unable to mount root fs via NFS.\n");
	}
	#else
	static inline void mount_nfs_root(void)
	{
	}
	#endif /* CONFIG_ROOT_NFS */

	#ifdef CONFIG_CIFS_ROOT

	#define CIFSROOT_TIMEOUT_MIN 5
	#define CIFSROOT_TIMEOUT_MAX 30
	#define CIFSROOT_RETRY_MAX 5

	static void __init mount_cifs_root(void)
	{
	char root_dev, root_data;
	unsigned int timeout;
	int try;

	if (cifs_root_data(&root_dev, &root_data))
	goto fail;

	timeout = CIFSROOT_TIMEOUT_MIN;
	for (try = 1; ; try++) {
	if (!do_mount_root(root_dev, "cifs", root_mountflags,
	root_data))
	return;
	if (try > CIFSROOT_RETRY_MAX)
	break;

	ssleep(timeout);
	timeout <<= 1;
	if (timeout > CIFSROOT_TIMEOUT_MAX)
	timeout = CIFSROOT_TIMEOUT_MAX;
	}
	fail:
	pr_err("VFS: Unable to mount root fs via SMB.\n");
	}
	#else
	static inline void mount_cifs_root(void)
	{
	}
	#endif /* CONFIG_CIFS_ROOT */

	static bool __init fs_is_nodev(char *fstype)
	{
	struct file_system_type *fs = get_fs_type(fstype);
	bool ret = false;

	if (fs) {
	ret = !(fs->fs_flags & FS_REQUIRES_DEV);
	put_filesystem(fs);
	}

	return ret;
	}

	static int __init mount_nodev_root(char *root_device_name)
	{
	char fs_names, fstype;
	int err = -EINVAL;
	int num_fs, i;

	fs_names = (void *)__get_free_page(GFP_KERNEL);
	if (!fs_names)
	return -EINVAL;
	num_fs = split_fs_names(fs_names, PAGE_SIZE);

	for (i = 0, fstype = fs_names; i < num_fs;
	i++, fstype += strlen(fstype) + 1) {
	if (!*fstype)
	continue;
	if (!fs_is_nodev(fstype))
	continue;
	err = do_mount_root(root_device_name, fstype, root_mountflags,
	root_mount_data);
	if (!err)
	break;
	}

	free_page((unsigned long)fs_names);
	return err;
	}

	#ifdef CONFIG_BLOCK
	static void __init mount_block_root(char *root_device_name)
	{
	int err = create_dev("/dev/root", ROOT_DEV);

	if (err < 0)
	pr_emerg("Failed to create /dev/root: %d\n", err);
	mount_root_generic("/dev/root", root_device_name, root_mountflags);
	}
	#else
	static inline void mount_block_root(char *root_device_name)
	{
	}
	#endif /* CONFIG_BLOCK */

	void __init mount_root(char *root_device_name)
	{
	switch (ROOT_DEV) {
	case Root_NFS:
	mount_nfs_root();
	break;
	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)
	break;
	fallthrough;
	default:
	mount_block_root(root_device_name);
	break;
	}
	}

	/* wait for any asynchronous scanning to complete */
	static void __init wait_for_root(char *root_device_name)
	{
	ktime_t end;

	if (ROOT_DEV != 0)
	return;

	pr_info("Waiting for root device %s...\n", root_device_name);

	end = ktime_add_ms(ktime_get_raw(), root_wait);

	while (!driver_probe_done() \|\|
	early_lookup_bdev(root_device_name, &ROOT_DEV) < 0) {
	msleep(5);
	if (root_wait > 0 && ktime_after(ktime_get_raw(), end))
	break;
	}

	async_synchronize_full();

	}

	static dev_t __init parse_root_device(char *root_device_name)
	{
	int error;
	dev_t dev;

	if (!strncmp(root_device_name, "mtd", 3) \|\|
	!strncmp(root_device_name, "ubi", 3))
	return Root_Generic;
	if (strcmp(root_device_name, "/dev/nfs") == 0)
	return Root_NFS;
	if (strcmp(root_device_name, "/dev/cifs") == 0)
	return Root_CIFS;
	if (strcmp(root_device_name, "/dev/ram") == 0)
	return Root_RAM0;

	error = early_lookup_bdev(root_device_name, &dev);
	if (error) {
	if (error == -EINVAL && root_wait) {
	pr_err("Disabling rootwait; root= is invalid.\n");
	root_wait = 0;
	}
	return 0;
	}
	return dev;
	}

	/*
	* Prepare the namespace - decide what/where to mount, load ramdisks, etc.
	*/
	void __init prepare_namespace(void)
	{
	if (root_delay) {
	printk(KERN_INFO "Waiting %d sec before mounting root device...\n",
	root_delay);
	ssleep(root_delay);
	}

	/*
	* wait for the known devices to complete their probing
	*
	* Note: this is a potential source of long boot delays.
	* For example, it is not atypical to wait 5 seconds here
	* for the touchpad of a laptop to initialize.
	*/
	wait_for_device_probe();

	md_run_setup();

	if (saved_root_name[0])
	ROOT_DEV = parse_root_device(saved_root_name);

	if (initrd_load(saved_root_name))
	goto out;

	if (root_wait)
	wait_for_root(saved_root_name);
	mount_root(saved_root_name);
	out:
	devtmpfs_mount();
	init_mount(".", "/", NULL, MS_MOVE, NULL);
	init_chroot(".");
	}

	static bool is_tmpfs;
	static int rootfs_init_fs_context(struct fs_context *fc)
	{
	if (IS_ENABLED(CONFIG_TMPFS) && is_tmpfs)
	return shmem_init_fs_context(fc);

	return ramfs_init_fs_context(fc);
	}

	struct file_system_type rootfs_fs_type = {
	.name = "rootfs",
	.init_fs_context = rootfs_init_fs_context,
	.kill_sb = kill_litter_super,
	};

	void __init init_rootfs(void)
	{
	if (IS_ENABLED(CONFIG_TMPFS)) {
	if (!saved_root_name[0] && !root_fs_names)
	is_tmpfs = true;
	else if (root_fs_names && !!strstr(root_fs_names, "tmpfs"))
	is_tmpfs = true;
	}
	}