// 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/genhd.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/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 root_
device_name;
static char __initdata saved_root_name[64];
static int root_wait;
dev_t ROOT_
DEV;
static int __init load_ramd
isk(char *str)
{
pr_warn("ignoring the deprecated load_ramd
isk= option\n");
return 1;
}
__setup("load_ramd
isk=", load_ramd
isk);
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);
#ifdef CONFIG_BLOCK
struct uuidcmp {
const char *uuid;
int len;
};
/**
* match_
dev_by_uuid - callback for finding a partition using its uuid
* @
dev:
device passed in by the caller
* @data: opaque pointer to the desired struct uuidcmp to match
*
* Returns 1 if the
device matches, and 0 otherw
ise.
*/
static int match_
dev_by_uuid(struct
device *
dev, const void *data)
{
const struct uuidcmp *cmp = data;
struct hd_struct *part =
dev_to_part(
dev);
if (
!part->info)
goto no_match;
if (strncasecmp(cmp->uuid, part->info->uuid, cmp->len))
goto no_match;
return 1;
no_match:
return 0;
}
/**
*
devt_from_partuuid - looks up the
dev_t of a partition by its UUID
* @uuid_str: char array containing ascii UUID
*
* The function
will return the first partition which contains a matching
* UUID value in its partition_meta_info struct. Th
is does
not search
* by
filesystem UUIDs.
*
* If @uuid_str
is followed by a "/PARTNROFF=%d", then the number
will be
* extracted and used as an offset from the partition identified by the UUID.
*
* Returns the matching
dev_t on success or 0 on failure.
*/
static
dev_t
devt_from_partuuid(const char *uuid_str)
{
dev_t res = 0;
struct uuidcmp cmp;
struct
device *
dev = NULL;
struct gend
isk *d
isk;
struct hd_struct *part;
int offset = 0;
bool clear_root_wait = false;
char *slash;
cmp.uuid = uuid_str;
slash = strchr(uuid_str, '/');
/* Check for optional partition number offset attributes. */
if (slash) {
char c = 0;
/* Explicitly fail on poor PARTUUID syntax. */
if (sscanf(slash + 1,
"PARTNROFF=%d%c", &offset, &c)
!= 1) {
clear_root_wait = true;
goto done;
}
cmp.len = slash - uuid_str;
} else {
cmp.len = strlen(uuid_str);
}
if (
!cmp.len) {
clear_root_wait = true;
goto done;
}
dev = class_find_
device(&block_class, NULL, &cmp,
&match_
dev_by_uuid);
if (
!dev)
goto done;
res =
dev->
devt;
/* Attempt to find the partition by offset. */
if (
!offset)
goto no_offset;
res = 0;
d
isk = part_to_d
isk(
dev_to_part(
dev));
part = d
isk_get_part(d
isk,
dev_to_part(
dev)->partno + offset);
if (part) {
res = part_
devt(part);
put_
device(part_to_
dev(part));
}
no_offset:
put_
device(
dev);
done:
if (clear_root_wait) {
pr_err("VFS: PARTUUID=
is invalid.\n"
"Expected PARTUUID=<valid-uuid-id>[/PARTNROFF=%%d]\n");
if (root_wait)
pr_err("D
isabling rootwait; root=
is invalid.\n");
root_wait = 0;
}
return res;
}
/**
* match_
dev_by_label - callback for finding a partition using its label
* @
dev:
device passed in by the caller
* @data: opaque pointer to the label to match
*
* Returns 1 if the
device matches, and 0 otherw
ise.
*/
static int match_
dev_by_label(struct
device *
dev, const void *data)
{
const char *label = data;
struct hd_struct *part =
dev_to_part(
dev);
if (part->info &&
!strcmp(label, part->info->volname))
return 1;
return 0;
}
#endif
/*
* Convert a name into
device number. We accept the following variants:
*
* 1) <hex_major><hex_minor>
device number in hexadecimal represents itself
* no leading 0x, for example b30
2.
*
2) /
dev/nfs represents Root_NFS (0xff)
* 3) /
dev/<d
isk_name> represents the
device number of d
isk
* 4) /
dev/<d
isk_name><decimal> represents the
device number
* of partition -
device number of d
isk plus the partition number
* 5) /
dev/<d
isk_name>p<decimal> - same as the above, that form
is
* used when d
isk name of partitioned d
isk ends on a digit.
* 6) PARTUUID=0011
2233-4455-6677-8899-AABBCCDDEEFF representing the
* unique id of a partition if the partition table provides it.
* The UUID may be either an EFI/GPT UUID, or refer to an MSDOS
* partition using the format SSSSSSSS-PP, w
here SSSSSSSS
is a zero-
* filled hex representation of the 3
2-bit "NT d
isk signature", and PP
*
is a zero-filled hex representation of the 1-based partition number.
* 7) PARTUUID=<UUID>/PARTNROFF=<int> to select a partition in relation to
* a partition with a known unique id.
* 8) <major>:<minor> major and minor number of the
device separated by
* a colon.
* 9) PARTLABEL=<name> with name being the GPT partition label.
* MSDOS partitions do
not support labels
!
* 10) /
dev/cifs represents Root_CIFS (0xfe)
*
* If name doesn't have fall into the categories above, we return (0,0).
* block_class
is used to check if something
is a d
isk name. If the d
isk
* name contains slashes, the
device name has them replaced with
* bangs.
*/
dev_t name_to_
dev_t(const char *name)
{
char s[3
2];
char *p;
dev_t res = 0;
int part;
#ifdef CONFIG_BLOCK
if (strncmp(name, "PARTUUID=", 9) == 0) {
name += 9;
res =
devt_from_partuuid(name);
if (
!res)
goto fail;
goto done;
} else if (strncmp(name, "PARTLABEL=", 10) == 0) {
struct
device *
dev;
dev = class_find_
device(&block_class, NULL, name + 10,
&match_
dev_by_label);
if (
!dev)
goto fail;
res =
dev->
devt;
put_
device(
dev);
goto done;
}
#endif
if (strncmp(name, "/
dev/", 5)
!= 0) {
unsigned maj, min, offset;
char dummy;
if ((sscanf(name, "%u:%u%c", &maj, &min, &dummy) ==
2) ||
(sscanf(name, "%u:%u:%u:%c", &maj, &min, &offset, &dummy) == 3)) {
res = MK
DEV(maj, min);
if (maj
!= MAJOR(res) || min
!= MINOR(res))
goto fail;
} else {
res = new_decode_
dev(simple_strtoul(name, &p, 16));
if (*p)
goto fail;
}
goto done;
}
name += 5;
res = Root_NFS;
if (strcmp(name, "nfs") == 0)
goto done;
res = Root_CIFS;
if (strcmp(name, "cifs") == 0)
goto done;
res = Root_RAM0;
if (strcmp(name, "ram") == 0)
goto done;
if (strlen(name) > 31)
goto fail;
strcpy(s, name);
for (p = s; *p; p++)
if (*p == '/')
*p = '
!';
res = blk_lookup_
devt(s, 0);
if (res)
goto done;
/*
* try non-ex
istent, but valid partition, which may only ex
ist
* after revalidating the d
isk, like partitioned md
devices
*/
while (p > s &&
isdigit(p[-1]))
p--;
if (p == s ||
!*p || *p == '0')
goto fail;
/* try d
isk name without <part number> */
part = simple_strtoul(p, NULL, 10);
*p = '\0';
res = blk_lookup_
devt(s, part);
if (res)
goto done;
/* try d
isk name without p<part number> */
if (p < s +
2 ||
!isdigit(p[-
2]) || p[-1]
!= 'p')
goto fail;
p[-1] = '\0';
res = blk_lookup_
devt(s, part);
if (res)
goto done;
fail:
return 0;
done:
return res;
}
EXPORT_SYMBOL_GPL(name_to_
dev_t);
static int __init root_
dev_setup(char *line)
{
strlcpy(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 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);
static void __init get_fs_names(char *page)
{
char *s = page;
if (root_fs_names) {
strcpy(page, root_fs_names);
while (*s++) {
if (s[-1] == ',')
s[-1] = '\0';
}
} else {
int len = get_
filesystem_l
ist(page);
char *p, *next;
page[len] = '\0';
for (p = page-1; p; p = next) {
next = strchr(++p, '\n');
if (*p++
!= '\t')
continue;
while ((*s++ = *p++)
!= '\n')
;
s[-1] = '\0';
}
}
*s = '\0';
}
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_block_root(char *name, int flags)
{
struct page *page = alloc_page(GFP_KERNEL);
char *fs_names = page_address(page);
char *p;
char b[B
DEVNAME_SIZE];
scnprintf(b, B
DEVNAME_SIZE, "unknown-block(%u,%u)",
MAJOR(ROOT_
DEV), MINOR(ROOT_
DEV));
get_fs_names(fs_names);
retry:
for (p = fs_names; *p; p += strlen(p)+1) {
int err = do_mount_root(name, p, flags, root_mount_data);
switch (err) {
case 0:
goto out;
case -EACCES:
case -EINVAL:
continue;
}
/*
* Allow the user to d
istingu
ish between failed sys_open
* and bad superblock on root
device.
* and give them a l
ist of the available
devices
*/
printk("VFS: Can
not open root
device \"%s\" or %s: error %d\n",
root_
device_name, b, err);
printk("Please append a correct \"root=\" boot option;
here are the available partitions:\n");
printk_all_partitions();
#ifdef CONFIG_DEBUG_BLOCK_EXT_
DEVT
printk("DEBUG_BLOCK_EXT_
DEVT
is enabled, you need to specify "
"explicit textual name for \"root=\" boot option.\n");
#endif
panic("VFS: Unable to mount root fs on %s", b);
}
if (
!(flags & SB_RDONLY)) {
flags |= SB_RDONLY;
goto retry;
}
printk("L
ist of all partitions:\n");
printk_all_partitions();
printk("No
filesystem could mount root, tried: ");
for (p = fs_names; *p; p += strlen(p)+1)
printk(" %s", p);
printk("\n");
panic("VFS: Unable to mount root fs on %s", 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 int __init mount_nfs_root(void)
{
char *root_
dev, *root_data;
unsigned int timeout;
int try, err;
err = nfs_root_data(&root_
dev, &root_data);
if (err
!= 0)
return 0;
/*
* 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++) {
err = do_mount_root(root_
dev, "nfs",
root_mountflags, root_data);
if (err == 0)
return 1;
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;
}
return 0;
}
#endif
#ifdef CONFIG_CIFS_ROOT
extern int cifs_root_data(char **
dev, char **opts);
#define CIFSROOT_TIMEOUT_MIN 5
#define CIFSROOT_TIMEOUT_MAX 30
#define CIFSROOT_RETRY_MAX 5
static int __init mount_cifs_root(void)
{
char *root_
dev, *root_data;
unsigned int timeout;
int try, err;
err = cifs_root_data(&root_
dev, &root_data);
if (err
!= 0)
return 0;
timeout = CIFSROOT_TIMEOUT_MIN;
for (try = 1; ; try++) {
err = do_mount_root(root_
dev, "cifs", root_mountflags,
root_data);
if (err == 0)
return 1;
if (try > CIFSROOT_RETRY_MAX)
break;
ssleep(timeout);
timeout <<= 1;
if (timeout > CIFSROOT_TIMEOUT_MAX)
timeout = CIFSROOT_TIMEOUT_MAX;
}
return 0;
}
#endif
void __init mount_root(void)
{
#ifdef CONFIG_ROOT_NFS
if (ROOT_
DEV == Root_NFS) {
if (
!mount_nfs_root())
printk(KERN_ERR "VFS: Unable to mount root fs via NFS.\n");
return;
}
#endif
#ifdef CONFIG_CIFS_ROOT
if (ROOT_
DEV == Root_CIFS) {
if (
!mount_cifs_root())
printk(KERN_ERR "VFS: Unable to mount root fs via SMB.\n");
return;
}
#endif
#ifdef CONFIG_BLOCK
{
int err = create_
dev("/
dev/root", ROOT_
DEV);
if (err < 0)
pr_emerg("Failed to create /
dev/root: %d\n", err);
mount_block_root("/
dev/root", root_mountflags);
}
#endif
}
/*
* Prepare the namespace - decide what/w
here to mount, load ramd
isks, 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: th
is 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_
device_name = saved_root_name;
if (
!strncmp(root_
device_name, "mtd", 3) ||
!strncmp(root_
device_name, "ubi", 3)) {
mount_block_root(root_
device_name, root_mountflags);
goto out;
}
ROOT_
DEV = name_to_
dev_t(root_
device_name);
if (strncmp(root_
device_name, "/
dev/", 5) == 0)
root_
device_name += 5;
}
if (initrd_load())
goto out;
/* wait for any asynchronous scanning to complete */
if ((ROOT_
DEV == 0) && root_wait) {
printk(KERN_INFO "Waiting for root
device %s...\n",
saved_root_name);
while (driver_probe_done()
!= 0 ||
(ROOT_
DEV = name_to_
dev_t(saved_root_name)) == 0)
msleep(5);
async_synchronize_full();
}
mount_root();
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) &&
!saved_root_name[0] &&
(
!root_fs_names || strstr(root_fs_names, "tmpfs")))
is_tmpfs = true;
}
详细解析一下
本文解决了一个常见的Linux操作误区，即在挂载分区后尝试直接格式化的错误做法。文章指导读者应先使用'umount'命令卸载分区，再用'mkfs'命令进行格式化，最后重新挂载分区，确保操作流程正确无误。
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