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super.c
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super.c
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/*
* linux/fs/super.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*
* super.c contains code to handle: - mount structures
* - super-block tables
* - filesystem drivers list
* - mount system call
* - umount system call
* - ustat system call
*
* GK 2/5/95 - Changed to support mounting the root fs via NFS
*
* Added kerneld support: Jacques Gelinas and Bjorn Ekwall
* Added change_root: Werner Almesberger & Hans Lermen, Feb '96
* Added options to /proc/mounts:
* Torbj鰎n Lindh (torbjorn.lindh@gopta.se), April 14, 1996.
* Added devfs support: Richard Gooch <rgooch@atnf.csiro.au>, 13-JAN-1998
* Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 2000
*/
#include <linux/config.h>
#include <linux/string.h>
#include <linux/malloc.h>
#include <linux/locks.h>
#include <linux/smp_lock.h>
#include <linux/devfs_fs_kernel.h>
#include <linux/fd.h>
#include <linux/init.h>
#include <linux/quotaops.h>
#include <linux/acct.h>
#include <asm/uaccess.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_fs_sb.h>
#include <linux/nfs_mount.h>
#include <linux/kmod.h>
#define __NO_VERSION__
#include <linux/module.h>
/*
* We use a semaphore to synchronize all mount/umount
* activity - imagine the mess if we have a race between
* unmounting a filesystem and re-mounting it (or something
* else).
*/
static DECLARE_MUTEX(mount_sem);
extern void wait_for_keypress(void);
extern int root_mountflags;
static int do_remount_sb(struct super_block *sb, int flags, char * data);
/* this is initialized in init/main.c */
kdev_t ROOT_DEV;
int nr_super_blocks;
int max_super_blocks = NR_SUPER;
LIST_HEAD(super_blocks);
/*
* Handling of filesystem drivers list.
* Rules:
* Inclusion to/removals from/scanning of list are protected by spinlock.
* During the unload module must call unregister_filesystem().
* We can access the fields of list element if:
* 1) spinlock is held or
* 2) we hold the reference to the module.
* The latter can be guaranteed by call of try_inc_mod_count(); if it
* returned 0 we must skip the element, otherwise we got the reference.
* Once the reference is obtained we can drop the spinlock.
*/
static struct file_system_type *file_systems;
static rwlock_t file_systems_lock = RW_LOCK_UNLOCKED;
/* WARNING: This can be used only if we _already_ own a reference */
static void get_filesystem(struct file_system_type *fs)
{
if (fs->owner)
__MOD_INC_USE_COUNT(fs->owner);
}
static void put_filesystem(struct file_system_type *fs)
{
if (fs->owner)
__MOD_DEC_USE_COUNT(fs->owner);
}
static struct file_system_type **find_filesystem(const char *name)
{
struct file_system_type **p;
for (p=&file_systems; *p; p=&(*p)->next)
if (strcmp((*p)->name,name) == 0)
break;
return p;
}
/**
* register_filesystem - register a new filesystem
* @fs: the file system structure
*
* Adds the file system passed to the list of file systems the kernel
* is aware of for mount and other syscalls. Returns 0 on success,
* or a negative errno code on an error.
*
* The &struct file_system_type that is passed is linked into the kernel
* structures and must not be freed until the file system has been
* unregistered.
*/
int register_filesystem(struct file_system_type * fs)
{
int res = 0;
struct file_system_type ** p;
if (!fs)
return -EINVAL;
if (fs->next)
return -EBUSY;
write_lock(&file_systems_lock);
p = find_filesystem(fs->name);
if (*p)
res = -EBUSY;
else
*p = fs;
write_unlock(&file_systems_lock);
return res;
}
/**
* unregister_filesystem - unregister a file system
* @fs: filesystem to unregister
*
* Remove a file system that was previously successfully registered
* with the kernel. An error is returned if the file system is not found.
* Zero is returned on a success.
*
* Once this function has returned the &struct file_system_type structure
* may be freed or reused.
*/
int unregister_filesystem(struct file_system_type * fs)
{
struct file_system_type ** tmp;
write_lock(&file_systems_lock);
tmp = &file_systems;
while (*tmp) {
if (fs == *tmp) {
*tmp = fs->next;
fs->next = NULL;
write_unlock(&file_systems_lock);
return 0;
}
tmp = &(*tmp)->next;
}
write_unlock(&file_systems_lock);
return -EINVAL;
}
static int fs_index(const char * __name)
{
struct file_system_type * tmp;
char * name;
int err, index;
name = getname(__name);
err = PTR_ERR(name);
if (IS_ERR(name))
return err;
err = -EINVAL;
read_lock(&file_systems_lock);
for (tmp=file_systems, index=0 ; tmp ; tmp=tmp->next, index++) {
if (strcmp(tmp->name,name) == 0) {
err = index;
break;
}
}
read_unlock(&file_systems_lock);
putname(name);
return err;
}
static int fs_name(unsigned int index, char * buf)
{
struct file_system_type * tmp;
int len, res;
read_lock(&file_systems_lock);
for (tmp = file_systems; tmp; tmp = tmp->next, index--)
if (index <= 0 && try_inc_mod_count(tmp->owner))
break;
read_unlock(&file_systems_lock);
if (!tmp)
return -EINVAL;
/* OK, we got the reference, so we can safely block */
len = strlen(tmp->name) + 1;
res = copy_to_user(buf, tmp->name, len) ? -EFAULT : 0;
put_filesystem(tmp);
return res;
}
static int fs_maxindex(void)
{
struct file_system_type * tmp;
int index;
read_lock(&file_systems_lock);
for (tmp = file_systems, index = 0 ; tmp ; tmp = tmp->next, index++)
;
read_unlock(&file_systems_lock);
return index;
}
/*
* Whee.. Weird sysv syscall.
*/
asmlinkage long sys_sysfs(int option, unsigned long arg1, unsigned long arg2)
{
int retval = -EINVAL;
switch (option) {
case 1:
retval = fs_index((const char *) arg1);
break;
case 2:
retval = fs_name(arg1, (char *) arg2);
break;
case 3:
retval = fs_maxindex();
break;
}
return retval;
}
int get_filesystem_list(char * buf)
{
int len = 0;
struct file_system_type * tmp;
read_lock(&file_systems_lock);
tmp = file_systems;
while (tmp && len < PAGE_SIZE - 80) {
len += sprintf(buf+len, "%s\t%s\n",
(tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
tmp->name);
tmp = tmp->next;
}
read_unlock(&file_systems_lock);
return len;
}
struct file_system_type *get_fs_type(const char *name)
{
struct file_system_type *fs;
read_lock(&file_systems_lock);
fs = *(find_filesystem(name));
if (fs && !try_inc_mod_count(fs->owner))
fs = NULL;
read_unlock(&file_systems_lock);
if (!fs && (request_module(name) == 0)) {
read_lock(&file_systems_lock);
fs = *(find_filesystem(name));
if (fs && !try_inc_mod_count(fs->owner))
fs = NULL;
read_unlock(&file_systems_lock);
}
return fs;
}
static LIST_HEAD(vfsmntlist);
/**
* add_vfsmnt - add a new mount node
* @nd: location of mountpoint or %NULL if we want a root node
* @root: root of (sub)tree to be mounted
* @dev_name: device name to show in /proc/mounts or %NULL (for "none").
*
* This is VFS idea of mount. New node is allocated, bound to a tree
* we are mounting and optionally (OK, usually) registered as mounted
* on a given mountpoint. Returns a pointer to new node or %NULL in
* case of failure.
*
* Potential reason for failure (aside of trivial lack of memory) is a
* deleted mountpoint. Caller must hold ->i_zombie on mountpoint
* dentry (if any).
*
* Node is marked as MNT_VISIBLE (visible in /proc/mounts) unless both
* @nd and @devname are %NULL. It works since we pass non-%NULL @devname
* when we are mounting root and kern_mount() filesystems are deviceless.
* If we will get a kern_mount() filesystem with nontrivial @devname we
* will have to pass the visibility flag explicitly, so if we will add
* support for such beasts we'll have to change prototype.
*/
static struct vfsmount *add_vfsmnt(struct nameidata *nd,
struct dentry *root,
const char *dev_name)
{
struct vfsmount *mnt;
struct super_block *sb = root->d_inode->i_sb;
char *name;
mnt = kmalloc(sizeof(struct vfsmount), GFP_KERNEL);
if (!mnt)
goto out;
memset(mnt, 0, sizeof(struct vfsmount));
if (nd || dev_name)
mnt->mnt_flags = MNT_VISIBLE;
/* It may be NULL, but who cares? */
if (dev_name) {
name = kmalloc(strlen(dev_name)+1, GFP_KERNEL);
if (name) {
strcpy(name, dev_name);
mnt->mnt_devname = name;
}
}
/*填充vfsmount 结构*/
/*
*注：dentry中的sb并不是指向该目录下挂载设备的super_block，而是
* 指向了dentry所在的设备的super_block
* */
mnt->mnt_owner = current->uid;
atomic_set(&mnt->mnt_count,1);
mnt->mnt_sb = sb;
spin_lock(&dcache_lock);
if (nd && !IS_ROOT(nd->dentry) && d_unhashed(nd->dentry))
goto fail;
mnt->mnt_root = dget(root);
/*
* 如果nd结构不为空，则安装到它的dentry中，这里是do_mount中指定的安装节点
* 否则就安装到super_block的root内，这里是作为根目录来安装的。
* */
mnt->mnt_mountpoint = nd ? dget(nd->dentry) : dget(root);
/*如果nd中有mnt，即安装待安装文件系统之前安装节点处在另一个文件系统内，则该
* 文件系统就是待安装文件系统的父系统*/
mnt->mnt_parent = nd ? mntget(nd->mnt) : mnt;
if (nd) {
/*vfsmount注册到父文件系统的mnt_mounts链表上*/
list_add(&mnt->mnt_child, &nd->mnt->mnt_mounts);
/*vfsmount注册到安装节点dentry的d_vfsmnt上*/
list_add(&mnt->mnt_clash, &nd->dentry->d_vfsmnt);
} else {
INIT_LIST_HEAD(&mnt->mnt_child);
INIT_LIST_HEAD(&mnt->mnt_clash);
}
/*初始化vfsmount->mnt_mounts，该链表上以后可以挂接该文件系统的子文件系统
*即有另外的文件系统可能会被安装到该文件系统的某个子目录下
* */
INIT_LIST_HEAD(&mnt->mnt_mounts);
/*vfsmount注册到super_block的s_mounts上，因为同一个设备可能会被安装到多个
* 目录节点下*/
list_add(&mnt->mnt_instances, &sb->s_mounts);
list_add(&mnt->mnt_list, vfsmntlist.prev);
spin_unlock(&dcache_lock);
out:
return mnt;
fail:
spin_unlock(&dcache_lock);
if (mnt->mnt_devname)
kfree(mnt->mnt_devname);
kfree(mnt);
return NULL;
}
static void move_vfsmnt(struct vfsmount *mnt,
struct dentry *mountpoint,
struct vfsmount *parent,
const char *dev_name)
{
struct dentry *old_mountpoint;
struct vfsmount *old_parent;
char *new_devname = NULL;
if (dev_name) {
new_devname = kmalloc(strlen(dev_name)+1, GFP_KERNEL);
if (new_devname)
strcpy(new_devname, dev_name);
}
spin_lock(&dcache_lock);
old_mountpoint = mnt->mnt_mountpoint;
old_parent = mnt->mnt_parent;
/* flip names */
if (new_devname) {
if (mnt->mnt_devname)
kfree(mnt->mnt_devname);
mnt->mnt_devname = new_devname;
}
/* flip the linkage */
mnt->mnt_mountpoint = dget(mountpoint);
mnt->mnt_parent = parent ? mntget(parent) : mnt;
list_del(&mnt->mnt_clash);
list_del(&mnt->mnt_child);
if (parent) {
list_add(&mnt->mnt_child, &parent->mnt_mounts);
list_add(&mnt->mnt_clash, &mountpoint->d_vfsmnt);
} else {
INIT_LIST_HEAD(&mnt->mnt_child);
INIT_LIST_HEAD(&mnt->mnt_clash);
}
spin_unlock(&dcache_lock);
/* put the old stuff */
dput(old_mountpoint);
if (old_parent != mnt)
mntput(old_parent);
}
/*
* Called with spinlock held, releases it.
*/
static void remove_vfsmnt(struct vfsmount *mnt)
{
/* First of all, remove it from all lists */
list_del(&mnt->mnt_instances);//从super_block链表中移除
list_del(&mnt->mnt_clash);//从dentry链表中移除
list_del(&mnt->mnt_list);//从全局vfsmount链表中移除
list_del(&mnt->mnt_child);//从父文件系统的链表中移除
spin_unlock(&dcache_lock);
/* Now we can work safely */
if (mnt->mnt_parent != mnt)
mntput(mnt->mnt_parent);
dput(mnt->mnt_mountpoint);
dput(mnt->mnt_root);
if (mnt->mnt_devname)
kfree(mnt->mnt_devname);
kfree(mnt);
}
/* Use octal escapes, like mount does, for embedded spaces etc. */
static unsigned char need_escaping[] = { ' ', '\t', '\n', '\\' };
static int
mangle(const unsigned char *s, char *buf, int len) {
char *sp;
int n;
sp = buf;
while(*s && sp-buf < len-3) {
for (n = 0; n < sizeof(need_escaping); n++) {
if (*s == need_escaping[n]) {
*sp++ = '\\';
*sp++ = '0' + ((*s & 0300) >> 6);
*sp++ = '0' + ((*s & 070) >> 3);
*sp++ = '0' + (*s & 07);
goto next;
}
}
*sp++ = *s;
next:
s++;
}
return sp - buf; /* no trailing NUL */
}
static struct proc_fs_info {
int flag;
char *str;
} fs_info[] = {
{ MS_NOEXEC, ",noexec" },
{ MS_NOSUID, ",nosuid" },
{ MS_NODEV, ",nodev" },
{ MS_SYNCHRONOUS, ",sync" },
{ MS_MANDLOCK, ",mand" },
{ MS_NOATIME, ",noatime" },
{ MS_NODIRATIME, ",nodiratime" },
#ifdef MS_NOSUB /* Can't find this except in mount.c */
{ MS_NOSUB, ",nosub" },
#endif
{ 0, NULL }
};
static struct proc_nfs_info {
int flag;
char *str;
char *nostr;
} nfs_info[] = {
{ NFS_MOUNT_SOFT, ",soft", ",hard" },
{ NFS_MOUNT_INTR, ",intr", "" },
{ NFS_MOUNT_POSIX, ",posix", "" },
{ NFS_MOUNT_TCP, ",tcp", ",udp" },
{ NFS_MOUNT_NOCTO, ",nocto", "" },
{ NFS_MOUNT_NOAC, ",noac", "" },
{ NFS_MOUNT_NONLM, ",nolock", ",lock" },
{ NFS_MOUNT_BROKEN_SUID, ",broken_suid", "" },
{ 0, NULL, NULL }
};
int get_filesystem_info( char *buf )
{
struct list_head *p;
struct proc_fs_info *fs_infop;
struct proc_nfs_info *nfs_infop;
struct nfs_server *nfss;
int len, prevlen;
char *path, *buffer = (char *) __get_free_page(GFP_KERNEL);
if (!buffer) return 0;
len = prevlen = 0;
#define FREEROOM ((int)PAGE_SIZE-200-len)
#define MANGLE(s) len += mangle((s), buf+len, FREEROOM);
for (p = vfsmntlist.next; p != &vfsmntlist; p = p->next) {
struct vfsmount *tmp = list_entry(p, struct vfsmount, mnt_list);
if (!(tmp->mnt_flags & MNT_VISIBLE))
continue;
path = d_path(tmp->mnt_root, tmp, buffer, PAGE_SIZE);
if (!path)
continue;
MANGLE(tmp->mnt_devname ? tmp->mnt_devname : "none");
buf[len++] = ' ';
MANGLE(path);
buf[len++] = ' ';
MANGLE(tmp->mnt_sb->s_type->name);
len += sprintf(buf+len, " %s",
tmp->mnt_sb->s_flags & MS_RDONLY ? "ro" : "rw");
for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {
if (tmp->mnt_sb->s_flags & fs_infop->flag)
MANGLE(fs_infop->str);
}
if (!strcmp("nfs", tmp->mnt_sb->s_type->name)) {
nfss = &tmp->mnt_sb->u.nfs_sb.s_server;
len += sprintf(buf+len, ",v%d", nfss->rpc_ops->version);
len += sprintf(buf+len, ",rsize=%d", nfss->rsize);
len += sprintf(buf+len, ",wsize=%d", nfss->wsize);
#if 0
if (nfss->timeo != 7*HZ/10) {
len += sprintf(buf+len, ",timeo=%d",
nfss->timeo*10/HZ);
}
if (nfss->retrans != 3) {
len += sprintf(buf+len, ",retrans=%d",
nfss->retrans);
}
#endif
if (nfss->acregmin != 3*HZ) {
len += sprintf(buf+len, ",acregmin=%d",
nfss->acregmin/HZ);
}
if (nfss->acregmax != 60*HZ) {
len += sprintf(buf+len, ",acregmax=%d",
nfss->acregmax/HZ);
}
if (nfss->acdirmin != 30*HZ) {
len += sprintf(buf+len, ",acdirmin=%d",
nfss->acdirmin/HZ);
}
if (nfss->acdirmax != 60*HZ) {
len += sprintf(buf+len, ",acdirmax=%d",
nfss->acdirmax/HZ);
}
for (nfs_infop = nfs_info; nfs_infop->flag; nfs_infop++) {
char *str;
if (nfss->flags & nfs_infop->flag)
str = nfs_infop->str;
else
str = nfs_infop->nostr;
MANGLE(str);
}
len += sprintf(buf+len, ",addr=");
MANGLE(nfss->hostname);
}
len += sprintf(buf + len, " 0 0\n");
if (FREEROOM <= 3) {
len = prevlen;
len += sprintf(buf+len, "# truncated\n");
break;
}
prevlen = len;
}
free_page((unsigned long) buffer);
return len;
#undef MANGLE
#undef FREEROOM
}
/**
* __wait_on_super - wait on a superblock
* @sb: superblock to wait on
*
* Waits for a superblock to become unlocked and then returns. It does
* not take the lock. This is an internal function. See wait_on_super().
*/
void __wait_on_super(struct super_block * sb)
{
DECLARE_WAITQUEUE(wait, current);
add_wait_queue(&sb->s_wait, &wait);
repeat:
set_current_state(TASK_UNINTERRUPTIBLE);
if (sb->s_lock) {
schedule();
goto repeat;
}
remove_wait_queue(&sb->s_wait, &wait);
current->state = TASK_RUNNING;
}
/*
* Note: check the dirty flag before waiting, so we don't
* hold up the sync while mounting a device. (The newly
* mounted device won't need syncing.)
*/
void sync_supers(kdev_t dev)
{
struct super_block * sb;
for (sb = sb_entry(super_blocks.next);
sb != sb_entry(&super_blocks);
sb = sb_entry(sb->s_list.next)) {
if (!sb->s_dev)
continue;
if (dev && sb->s_dev != dev)
continue;
if (!sb->s_dirt)
continue;
lock_super(sb);
if (sb->s_dev && sb->s_dirt && (!dev || dev == sb->s_dev))
if (sb->s_op && sb->s_op->write_super)
sb->s_op->write_super(sb);
unlock_super(sb);
}
}
/**
* get_super - get the superblock of a device
* @dev: device to get the superblock for
*
* Scans the superblock list and finds the superblock of the file system
* mounted on the device given. %NULL is returned if no match is found.
*/
struct super_block * get_super(kdev_t dev)
{
struct super_block * s;
if (!dev)
return NULL;
restart:
s = sb_entry(super_blocks.next);
while (s != sb_entry(&super_blocks))
if (s->s_dev == dev) {
wait_on_super(s);
if (s->s_dev == dev)
return s;
goto restart;
} else
s = sb_entry(s->s_list.next);
return NULL;
}
asmlinkage long sys_ustat(dev_t dev, struct ustat * ubuf)
{
struct super_block *s;
struct ustat tmp;
struct statfs sbuf;
int err = -EINVAL;
lock_kernel();
s = get_super(to_kdev_t(dev));
unlock_kernel();
if (s == NULL)
goto out;
err = vfs_statfs(s, &sbuf);
if (err)
goto out;
memset(&tmp,0,sizeof(struct ustat));
tmp.f_tfree = sbuf.f_bfree;
tmp.f_tinode = sbuf.f_ffree;
err = copy_to_user(ubuf,&tmp,sizeof(struct ustat)) ? -EFAULT : 0;
out:
return err;
}
/**
* get_empty_super - find empty superblocks
*
* Find a superblock with no device assigned. A free superblock is
* found and returned. If neccessary new superblocks are allocated.
* %NULL is returned if there are insufficient resources to complete
* the request.
*/
struct super_block *get_empty_super(void)
{
struct super_block *s;
for (s = sb_entry(super_blocks.next);
s != sb_entry(&super_blocks);
s = sb_entry(s->s_list.next)) {
if (s->s_dev)
continue;
if (!s->s_lock)
return s;
printk("VFS: empty superblock %p locked!\n", s);
}
/* Need a new one... */
if (nr_super_blocks >= max_super_blocks)
return NULL;
s = kmalloc(sizeof(struct super_block), GFP_USER);
if (s) {
nr_super_blocks++;
memset(s, 0, sizeof(struct super_block));
INIT_LIST_HEAD(&s->s_dirty);
list_add (&s->s_list, super_blocks.prev);
init_waitqueue_head(&s->s_wait);
INIT_LIST_HEAD(&s->s_files);
INIT_LIST_HEAD(&s->s_mounts);
}
return s;
}
static struct super_block * read_super(kdev_t dev, struct block_device *bdev,
struct file_system_type *type, int flags,
void *data, int silent)
{
struct super_block * s;
s = get_empty_super();
if (!s)
goto out;
/*先作一些VSF层的相关初始化*/
s->s_dev = dev;
s->s_bdev = bdev;
s->s_flags = flags;
s->s_dirt = 0;
sema_init(&s->s_vfs_rename_sem,1);
sema_init(&s->s_nfsd_free_path_sem,1);
s->s_type = type;
sema_init(&s->s_dquot.dqio_sem, 1);
sema_init(&s->s_dquot.dqoff_sem, 1);
s->s_dquot.flags = 0;
lock_super(s);
/*读入具体文件系统的super_block*/
if (!type->read_super(s, data, silent))
goto out_fail;
unlock_super(s);
/* tell bdcache that we are going to keep this one */
if (bdev)
atomic_inc(&bdev->bd_count);
out:
return s;
out_fail:
s->s_dev = 0;
s->s_bdev = 0;
s->s_type = NULL;
unlock_super(s);
return NULL;
}
/*
* Unnamed block devices are dummy devices used by virtual
* filesystems which don't use real block-devices. -- jrs
*/
static unsigned int unnamed_dev_in_use[256/(8*sizeof(unsigned int))];
kdev_t get_unnamed_dev(void)
{
int i;
for (i = 1; i < 256; i++) {
if (!test_and_set_bit(i,unnamed_dev_in_use))
return MKDEV(UNNAMED_MAJOR, i);
}
return 0;
}
void put_unnamed_dev(kdev_t dev)
{
if (!dev || MAJOR(dev) != UNNAMED_MAJOR)
return;
if (test_and_clear_bit(MINOR(dev), unnamed_dev_in_use))
return;
printk("VFS: put_unnamed_dev: freeing unused device %s\n",
kdevname(dev));
}
static struct super_block *get_sb_bdev(struct file_system_type *fs_type,
char *dev_name, int flags, void * data)
{
struct inode *inode;
struct block_device *bdev;
struct block_device_operations *bdops;
struct super_block * sb;
struct nameidata nd;
kdev_t dev;
int error = 0;
/* What device it is? */
if (!dev_name || !*dev_name)
return ERR_PTR(-EINVAL);
if (path_init(dev_name, LOOKUP_FOLLOW|LOOKUP_POSITIVE, &nd))
error = path_walk(dev_name, &nd);
if (error)
return ERR_PTR(error);
/*
* 查找到待安装文件系统所在的设备文件dentry对象
* */
inode = nd.dentry->d_inode;
error = -ENOTBLK;
if (!S_ISBLK(inode->i_mode))
goto out;
error = -EACCES;
if (IS_NODEV(inode))
goto out;
/*获取设备对象*/
bdev = inode->i_bdev;
/*获取操作函数表*/
bdops = devfs_get_ops ( devfs_get_handle_from_inode (inode) );
if (bdops) bdev->bd_op = bdops;
/* Done with lookups, semaphore down */
down(&mount_sem);
dev = to_kdev_t(bdev->bd_dev);
/*查找内存中该文件系统的super_block*/
sb = get_super(dev);
if (sb) {
if (fs_type == sb->s_type &&
((flags ^ sb->s_flags) & MS_RDONLY) == 0) {
path_release(&nd);
return sb;
}
} else {
/*如果没有查找到的话，就需要从设备中读入*/
mode_t mode = FMODE_READ; /* we always need it ;-) */
if (!(flags & MS_RDONLY))
mode |= FMODE_WRITE;
/*打开设备*/
error = blkdev_get(bdev, mode, 0, BDEV_FS);
if (error)
goto out;
check_disk_change(dev);
error = -EACCES;
if (!(flags & MS_RDONLY) && is_read_only(dev))
goto out1;
error = -EINVAL;
/*读入超级块*/
sb = read_super(dev, bdev, fs_type, flags, data, 0);
if (sb) {
get_filesystem(fs_type);
path_release(&nd);
return sb;
}
out1:
blkdev_put(bdev, BDEV_FS);
}
out:
path_release(&nd);
up(&mount_sem);
return ERR_PTR(error);
}
static struct super_block *get_sb_nodev(struct file_system_type *fs_type,
int flags, void * data)
{
kdev_t dev;
int error = -EMFILE;
down(&mount_sem);
dev = get_unnamed_dev();
if (dev) {
struct super_block * sb;
error = -EINVAL;
sb = read_super(dev, NULL, fs_type, flags, data, 0);
if (sb) {
get_filesystem(fs_type);
return sb;
}
put_unnamed_dev(dev);
}
up(&mount_sem);
return ERR_PTR(error);
}
static struct super_block *get_sb_single(struct file_system_type *fs_type,
int flags, void *data)
{
struct super_block * sb;
/*
* Get the superblock of kernel-wide instance, but
* keep the reference to fs_type.
*/
down(&mount_sem);
sb = fs_type->kern_mnt->mnt_sb;
if (!sb)
BUG();
get_filesystem(fs_type);
do_remount_sb(sb, flags, data);
return sb;
}
static void kill_super(struct super_block *sb, int umount_root)
{
struct block_device *bdev;
kdev_t dev;
struct dentry *root = sb->s_root;
struct file_system_type *fs = sb->s_type;
struct super_operations *sop = sb->s_op;
sb->s_root = NULL;
/* Need to clean after the sucker */
if (fs->fs_flags & FS_LITTER)
d_genocide(root);
if (fs->fs_flags & (FS_SINGLE|FS_LITTER))
shrink_dcache_parent(root);
dput(root);
lock_super(sb);
if (sop) {
if (sop->write_super && sb->s_dirt)
sop->write_super(sb);
if (sop->put_super)
sop->put_super(sb);
}
/* Forget any remaining inodes */
if (invalidate_inodes(sb)) {
printk("VFS: Busy inodes after unmount. "
"Self-destruct in 5 seconds. Have a nice day...\n");
}
dev = sb->s_dev;
sb->s_dev = 0; /* Free the superblock */
bdev = sb->s_bdev;
sb->s_bdev = NULL;
put_filesystem(fs);
sb->s_type = NULL;
unlock_super(sb);
if (umount_root) {
/* special: the old device driver is going to be
a ramdisk and the point of this call is to free its
protected memory (even if dirty). */
destroy_buffers(dev);
}
if (bdev) {
blkdev_put(bdev, BDEV_FS);
bdput(bdev);
} else
put_unnamed_dev(dev);
}
/*
* Alters the mount flags of a mounted file system. Only the mount point
* is used as a reference - file system type and the device are ignored.
*/
static int do_remount_sb(struct super_block *sb, int flags, char *data)
{
int retval;
if (!(flags & MS_RDONLY) && sb->s_dev && is_read_only(sb->s_dev))
return -EACCES;
/*flags |= MS_RDONLY;*/
/* If we are remounting RDONLY, make sure there are no rw files open */
if ((flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY))
if (!fs_may_remount_ro(sb))
return -EBUSY;
if (sb->s_op && sb->s_op->remount_fs) {
lock_super(sb);
retval = sb->s_op->remount_fs(sb, &flags, data);
unlock_super(sb);
if (retval)
return retval;
}
sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
/*
* We can't invalidate inodes as we can loose data when remounting
* (someone might manage to alter data while we are waiting in lock_super()
* or in foo_remount_fs()))
*/
return 0;
}