/*
 *  linux/fs/super.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  super.c contains code to handle: - mount structures
 *                                   - super-block tables.
 *                                   - mount system call
 *                                   - umount system call
 *
 *  Added options to /proc/mounts
 *  Torbjörn Lindh (torbjorn.lindh@gopta.se), April 14, 1996.
 *
 * 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
 */

#include <linux/config.h>
#include <linux/malloc.h>
#include <linux/locks.h>
#include <linux/smp_lock.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>

#ifdef CONFIG_KMOD
#include <linux/kmod.h>
#endif

/*
 * 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 struct semaphore mount_sem = MUTEX;

extern void wait_for_keypress(void);
extern struct file_operations * get_blkfops(unsigned int major);

extern int root_mountflags;
extern void rd_load_secondary(void);

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 = 0;
int max_super_blocks = NR_SUPER;
LIST_HEAD(super_blocks);

static struct file_system_type *file_systems = (struct file_system_type *) NULL;
struct vfsmount *vfsmntlist = (struct vfsmount *) NULL;
static struct vfsmount *vfsmnttail = (struct vfsmount *) NULL,
                       *mru_vfsmnt = (struct vfsmount *) NULL;

/* 
 * This part handles the management of the list of mounted filesystems.
 */
struct vfsmount *lookup_vfsmnt(kdev_t dev)
{
        struct vfsmount *lptr;

        if (vfsmntlist == (struct vfsmount *)NULL)
                return ((struct vfsmount *)NULL);

        if (mru_vfsmnt != (struct vfsmount *)NULL &&
            mru_vfsmnt->mnt_dev == dev)
                return (mru_vfsmnt);

        for (lptr = vfsmntlist;
             lptr != (struct vfsmount *)NULL;
             lptr = lptr->mnt_next)
                if (lptr->mnt_dev == dev) {
                        mru_vfsmnt = lptr;
                        return (lptr);
                }

        return ((struct vfsmount *)NULL);
        /* NOTREACHED */
}

static struct vfsmount *add_vfsmnt(struct super_block *sb,
                        const char *dev_name, const char *dir_name)
{
        struct vfsmount *lptr;
        char *tmp, *name;

        lptr = (struct vfsmount *)kmalloc(sizeof(struct vfsmount), GFP_KERNEL);
        if (!lptr)
                goto out;
        memset(lptr, 0, sizeof(struct vfsmount));

        lptr->mnt_sb = sb;
        lptr->mnt_dev = sb->s_dev;
        lptr->mnt_flags = sb->s_flags;

        sema_init(&lptr->mnt_dquot.dqio_sem, 1);
        sema_init(&lptr->mnt_dquot.dqoff_sem, 1);
        lptr->mnt_dquot.flags = 0;

        /* N.B. Is it really OK to have a vfsmount without names? */
        if (dev_name && !IS_ERR(tmp = getname(dev_name))) {
                name = (char *) kmalloc(strlen(tmp)+1, GFP_KERNEL);
                if (name) {
                        strcpy(name, tmp);
                        lptr->mnt_devname = name;
                }
                putname(tmp);
        }
        if (dir_name && !IS_ERR(tmp = getname(dir_name))) {
                name = (char *) kmalloc(strlen(tmp)+1, GFP_KERNEL);
                if (name) {
                        strcpy(name, tmp);
                        lptr->mnt_dirname = name;
                }
                putname(tmp);
        }

        if (vfsmntlist == (struct vfsmount *)NULL) {
                vfsmntlist = vfsmnttail = lptr;
        } else {
                vfsmnttail->mnt_next = lptr;
                vfsmnttail = lptr;
        }
out:
        return lptr;
}

static void remove_vfsmnt(kdev_t dev)
{
        struct vfsmount *lptr, *tofree;

        if (vfsmntlist == (struct vfsmount *)NULL)
                return;
        lptr = vfsmntlist;
        if (lptr->mnt_dev == dev) {
                tofree = lptr;
                vfsmntlist = lptr->mnt_next;
                if (vfsmnttail->mnt_dev == dev)
                        vfsmnttail = vfsmntlist;
        } else {
                while (lptr->mnt_next != (struct vfsmount *)NULL) {
                        if (lptr->mnt_next->mnt_dev == dev)
                                break;
                        lptr = lptr->mnt_next;
                }
                tofree = lptr->mnt_next;
                if (tofree == (struct vfsmount *)NULL)
                        return;
                lptr->mnt_next = lptr->mnt_next->mnt_next;
                if (vfsmnttail->mnt_dev == dev)
                        vfsmnttail = lptr;
        }
        if (tofree == mru_vfsmnt)
                mru_vfsmnt = NULL;
        kfree(tofree->mnt_devname);
        kfree(tofree->mnt_dirname);
        kfree_s(tofree, sizeof(struct vfsmount));
}

int register_filesystem(struct file_system_type * fs)
{
        struct file_system_type ** tmp;

        if (!fs)
                return -EINVAL;
        if (fs->next)
                return -EBUSY;
        tmp = &file_systems;
        while (*tmp) {
                if (strcmp((*tmp)->name, fs->name) == 0)
                        return -EBUSY;
                tmp = &(*tmp)->next;
        }
        *tmp = fs;
        return 0;
}

int unregister_filesystem(struct file_system_type * fs)
{
#ifdef CONFIG_MODULES
        struct file_system_type ** tmp;

        tmp = &file_systems;
        while (*tmp) {
                if (fs == *tmp) {
                        *tmp = fs->next;
                        fs->next = NULL;
                        return 0;
                }
                tmp = &(*tmp)->next;
        }
#endif
        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;

        index = 0;
        for (tmp = file_systems ; tmp ; tmp = tmp->next) {
                if (strcmp(tmp->name, name) == 0) {
                        putname(name);
                        return index;
                }
                index++;
        }
        putname(name);
        return -EINVAL;
}

static int fs_name(unsigned int index, char * buf)
{
        struct file_system_type * tmp;
        int len;

        tmp = file_systems;
        while (tmp && index > 0) {
                tmp = tmp->next;
                index--;
        }
        if (!tmp)
                return -EINVAL;
        len = strlen(tmp->name) + 1;
        return copy_to_user(buf, tmp->name, len) ? -EFAULT : 0;
}

static int fs_maxindex(void)
{
        struct file_system_type * tmp;
        int index;

        index = 0;
        for (tmp = file_systems ; tmp ; tmp = tmp->next)
                index++;
        return index;
}

/*
 * Whee.. Weird sysv syscall. 
 */
asmlinkage int sys_sysfs(int option, unsigned long arg1, unsigned long arg2)
{
        int retval = -EINVAL;

        lock_kernel();
        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;
        }
        unlock_kernel();
        return retval;
}

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;
} nfs_info[] = {
        { NFS_MOUNT_SOFT, ",soft" },
        { NFS_MOUNT_INTR, ",intr" },
        { NFS_MOUNT_POSIX, ",posix" },
        { NFS_MOUNT_TCP, ",tcp" },
        { NFS_MOUNT_NOCTO, ",nocto" },
        { NFS_MOUNT_NOAC, ",noac" },
        { NFS_MOUNT_NONLM, ",nolock" },
        { 0, NULL }
};

int get_filesystem_info( char *buf )
{
        struct vfsmount *tmp = vfsmntlist;
        struct proc_fs_info *fs_infop;
        struct proc_nfs_info *nfs_infop;
        struct nfs_server *nfss;
        int len = 0;

        while ( tmp && len < PAGE_SIZE - 160)
        {
                len += sprintf( buf + len, "%s %s %s %s",
                        tmp->mnt_devname, tmp->mnt_dirname, tmp->mnt_sb->s_type->name,
                        tmp->mnt_flags & MS_RDONLY ? "ro" : "rw" );
                for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {
                  if (tmp->mnt_flags & fs_infop->flag) {
                    strcpy(buf + len, fs_infop->str);
                    len += strlen(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);

                        if (nfss->rsize != NFS_DEF_FILE_IO_BUFFER_SIZE) {
                                len += sprintf(buf+len, ",rsize=%d",
                                               nfss->rsize);
                        }
                        if (nfss->wsize != NFS_DEF_FILE_IO_BUFFER_SIZE) {
                                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++) {
                                if (nfss->flags & nfs_infop->flag) {
                                        strcpy(buf + len, nfs_infop->str);
                                        len += strlen(nfs_infop->str);
                                }
                        }
                        len += sprintf(buf+len, ",addr=%s",
                                       nfss->hostname);
                }
                len += sprintf( buf + len, " 0 0\n" );
                tmp = tmp->mnt_next;
        }

        return len;
}

int get_filesystem_list(char * buf)
{
        int len = 0;
        struct file_system_type * tmp;

        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;
        }
        return len;
}

struct file_system_type *get_fs_type(const char *name)
{
        struct file_system_type * fs = file_systems;
        
        if (!name)
                return fs;
        for (fs = file_systems; fs && strcmp(fs->name, name); fs = fs->next)
                ;
#ifdef CONFIG_KMOD
        if (!fs && (request_module(name) == 0)) {
                for (fs = file_systems; fs && strcmp(fs->name, name); fs = fs->next)
                        ;
        }
#endif

        return fs;
}

void __wait_on_super(struct super_block * sb)
{
        struct wait_queue wait = { current, NULL };

        add_wait_queue(&sb->s_wait, &wait);
repeat:
        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;
                /* N.B. Should lock the superblock while writing */
                wait_on_super(sb);
                if (!sb->s_dev || !sb->s_dirt)
                        continue;
                if (dev && (dev != sb->s_dev))
                        continue;
                if (sb->s_op && sb->s_op->write_super)
                        sb->s_op->write_super(sb);
        }
}

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 int sys_ustat(dev_t dev, struct ustat * ubuf)
{
        struct super_block *s;
        struct ustat tmp;
        struct statfs sbuf;
        mm_segment_t old_fs;
        int err = -EINVAL;

        lock_kernel();
        s = get_super(to_kdev_t(dev));
        if (s == NULL)
                goto out;
        err = -ENOSYS;
        if (!(s->s_op->statfs))
                goto out;

        old_fs = get_fs();
        set_fs(get_ds());
        s->s_op->statfs(s,&sbuf,sizeof(struct statfs));
        set_fs(old_fs);

        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:
        unlock_kernel();
        return err;
}

/*
 * Find a super_block with no device assigned.
 */
static 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);
        }
        return s;
}

static struct super_block * read_super(kdev_t dev,const char *name,int flags,
                                       void *data, int silent)
{
        struct super_block * s;
        struct file_system_type *type;

        if (!dev)
                goto out_null;
        check_disk_change(dev);
        s = get_super(dev);
        if (s)
                goto out;

        type = get_fs_type(name);
        if (!type) {
                printk("VFS: on device %s: get_fs_type(%s) failed\n",
                       kdevname(dev), name);
                goto out;
        }
        s = get_empty_super();
        if (!s)
                goto out;
        s->s_dev = dev;
        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);
        /* N.B. Should lock superblock now ... */
        if (!type->read_super(s, data, silent))
                goto out_fail;
        s->s_dev = dev; /* N.B. why do this again?? */
        s->s_rd_only = 0;
        s->s_type = type;
out:
        return s;

        /* N.B. s_dev should be cleared in type->read_super */
out_fail:
        s->s_dev = 0;
out_null:
        s = NULL;
        goto out;
}

/*
 * Unnamed block devices are dummy devices used by virtual
 * filesystems which don't use real block-devices.  -- jrs
 */

static unsigned long unnamed_dev_in_use[256/(8*sizeof(unsigned long))] = { 0, };

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 int d_umount(struct super_block * sb)
{
        struct dentry * root = sb->s_root;
        struct dentry * covered = root->d_covers;

        if (root->d_count != 1)
                return -EBUSY;

        if (root->d_inode->i_state)
                return -EBUSY;

        sb->s_root = NULL;

        if (covered != root) {
                root->d_covers = root;
                covered->d_mounts = covered;
                dput(covered);
        }
        dput(root);
        return 0;
}

static void d_mount(struct dentry *covered, struct dentry *dentry)
{
        if (covered->d_mounts != covered) {
                printk("VFS: mount - already mounted\n");
                return;
        }
        covered->d_mounts = dentry;
        dentry->d_covers = covered;
}

static int do_umount(kdev_t dev, int unmount_root, int flags)
{
        struct super_block * sb;
        int retval;
        
        retval = -ENOENT;
        sb = get_super(dev);
        if (!sb || !sb->s_root)
                goto out;

        /*
         * Before checking whether the filesystem is still busy,
         * make sure the kernel doesn't hold any quota files open
         * on the device. If the umount fails, too bad -- there
         * are no quotas running any more. Just turn them on again.
         */
        DQUOT_OFF(dev);
        acct_auto_close(dev);

        /*
         * If we may have to abort operations to get out of this
         * mount, and they will themselves hold resources we must
         * allow the fs to do things. In the Unix tradition of
         * 'Gee thats tricky lets do it in userspace' the umount_begin
         * might fail to complete on the first run through as other tasks
         * must return, and the like. Thats for the mount program to worry
         * about for the moment.
         */
         
        if( (flags&MNT_FORCE) && sb->s_op->umount_begin)
                sb->s_op->umount_begin(sb);

        /*
         * Shrink dcache, then fsync. This guarantees that if the
         * filesystem is quiescent at this point, then (a) only the
         * root entry should be in use and (b) that root entry is
         * clean.
         */
        shrink_dcache_sb(sb);
        fsync_dev(dev);

        if (dev==ROOT_DEV && !unmount_root) {
                /*
                 * Special case for "unmounting" root ...
                 * we just try to remount it readonly.
                 */
                retval = 0;
                if (!(sb->s_flags & MS_RDONLY))
                        retval = do_remount_sb(sb, MS_RDONLY, 0);
                return retval;
        }

        retval = d_umount(sb);
        if (retval)
                goto out;

        if (sb->s_op) {
                if (sb->s_op->write_super && sb->s_dirt)
                        sb->s_op->write_super(sb);
        }

        lock_super(sb);
        if (sb->s_op) {
                if (sb->s_op->put_super)
                        sb->s_op->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");
        }

        sb->s_dev = 0;          /* Free the superblock */
        unlock_super(sb);

        remove_vfsmnt(dev);
out:
        return retval;
}

static int umount_dev(kdev_t dev, int flags)
{
        int retval;
        struct inode * inode = get_empty_inode();

        retval = -ENOMEM;
        if (!inode)
                goto out;

        inode->i_rdev = dev;
        retval = -ENXIO;
        if (MAJOR(dev) >= MAX_BLKDEV)
                goto out_iput;

        fsync_dev(dev);

        down(&mount_sem);

        retval = do_umount(dev, 0, flags);
        if (!retval) {
                fsync_dev(dev);
                if (dev != ROOT_DEV) {
                        blkdev_release(inode);
                        put_unnamed_dev(dev);
                }
        }

        up(&mount_sem);
out_iput:
        iput(inode);
out:
        return retval;
}

/*
 * Now umount can handle mount points as well as block devices.
 * This is important for filesystems which use unnamed block devices.
 *
 * There is a little kludge here with the dummy_inode.  The current
 * vfs release functions only use the r_dev field in the inode so
 * we give them the info they need without using a real inode.
 * If any other fields are ever needed by any block device release
 * functions, they should be faked here.  -- jrs
 *
 * We now support a flag for forced unmount like the other 'big iron'
 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
 */

asmlinkage int sys_umount(char * name, int flags)
{
        struct dentry * dentry;
        int retval;

        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;

        lock_kernel();
        dentry = namei(name);
        retval = PTR_ERR(dentry);
        if (!IS_ERR(dentry)) {
                struct inode * inode = dentry->d_inode;
                kdev_t dev = inode->i_rdev;

                retval = 0;             
                if (S_ISBLK(inode->i_mode)) {
                        if (IS_NODEV(inode))
                                retval = -EACCES;
                } else {
                        struct super_block *sb = inode->i_sb;
                        retval = -EINVAL;
                        if (sb && inode == sb->s_root->d_inode) {
                                dev = sb->s_dev;
                                retval = 0;
                        }
                }
                dput(dentry);

                if (!retval)
                        retval = umount_dev(dev, flags);
        }
        unlock_kernel();
        return retval;
}

/*
 *      The 2.0 compatible umount. No flags. 
 */
 
asmlinkage int sys_oldumount(char * name)
{
        return sys_umount(name,0);
}

/*
 * Check whether we can mount the specified device.
 */
int fs_may_mount(kdev_t dev)
{
        struct super_block * sb = get_super(dev);
        int busy;

        busy = sb && sb->s_root &&
               (sb->s_root->d_count != 1 || sb->s_root->d_covers != sb->s_root);
        return !busy;
}

/*
 * do_mount() does the actual mounting after sys_mount has done the ugly
 * parameter parsing. When enough time has gone by, and everything uses the
 * new mount() parameters, sys_mount() can then be cleaned up.
 *
 * We cannot mount a filesystem if it has active, used, or dirty inodes.
 * We also have to flush all inode-data for this device, as the new mount
 * might need new info.
 *
 * [21-Mar-97] T.Schoebel-Theuer: Now this can be overridden when
 * supplying a leading "!" before the dir_name, allowing "stacks" of
 * mounted filesystems. The stacking will only influence any pathname lookups
 * _after_ the mount, but open file descriptors or working directories that
 * are now covered remain valid. For example, when you overmount /home, any
 * process with old cwd /home/joe will continue to use the old versions,
 * as long as relative paths are used, but absolute paths like /home/joe/xxx
 * will go to the new "top of stack" version. In general, crossing a
 * mount point will always go to the top of stack element.
 * Anyone using this new feature must know what he/she is doing.
 */

int do_mount(kdev_t dev, const char * dev_name, const char * dir_name, const char * type, int flags, void * data)
{
        struct dentry * dir_d;
        struct super_block * sb;
        struct vfsmount *vfsmnt;
        int error;

        error = -EACCES;
        if (!(flags & MS_RDONLY) && dev && is_read_only(dev))
                goto out;

        /*
         * Do the lookup first to force automounting.
         */
        dir_d = namei(dir_name);
        error = PTR_ERR(dir_d);
        if (IS_ERR(dir_d))
                goto out;

        down(&mount_sem);
        error = -ENOTDIR;
        if (!S_ISDIR(dir_d->d_inode->i_mode))
                goto dput_and_out;

        error = -EBUSY;
        if (dir_d->d_covers != dir_d)
                goto dput_and_out;

        /*
         * Note: If the superblock already exists,
         * read_super just does a get_super().
         */
        error = -EINVAL;
        sb = read_super(dev, type, flags, data, 0);
        if (!sb)
                goto dput_and_out;

        /*
         * We may have slept while reading the super block, 
         * so we check afterwards whether it's safe to mount.
         */
        error = -EBUSY;
        if (!fs_may_mount(dev))
                goto dput_and_out;

        error = -ENOMEM;
        vfsmnt = add_vfsmnt(sb, dev_name, dir_name);
        if (vfsmnt) {
                d_mount(dget(dir_d), sb->s_root);
                error = 0;
        }

dput_and_out:
        dput(dir_d);
        up(&mount_sem);
out:
        return error;   
}


/*
 * 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.
 * FS-specific mount options can't be altered by remounting.
 */

static int do_remount_sb(struct super_block *sb, int flags, char *data)
{
        int retval;
        struct vfsmount *vfsmnt;
        
        /*
         * Invalidate the inodes, as some mount options may be changed.
         * N.B. If we are changing media, we should check the return
         * from invalidate_inodes ... can't allow _any_ open files.
         */
        invalidate_inodes(sb);

        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) {
                retval = sb->s_op->remount_fs(sb, &flags, data);
                if (retval)
                        return retval;
        }
        sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
        vfsmnt = lookup_vfsmnt(sb->s_dev);
        if (vfsmnt)
                vfsmnt->mnt_flags = sb->s_flags;
        return 0;
}

static int do_remount(const char *dir,int flags,char *data)
{
        struct dentry *dentry;
        int retval;

        dentry = namei(dir);
        retval = PTR_ERR(dentry);
        if (!IS_ERR(dentry)) {
                struct super_block * sb = dentry->d_inode->i_sb;

                retval = -ENODEV;
                if (sb) {
                        retval = -EINVAL;
                        if (dentry == sb->s_root) {
                                /*
                                 * Shrink the dcache and sync the device.
                                 */
                                shrink_dcache_sb(sb);
                                fsync_dev(sb->s_dev);
                                if (flags & MS_RDONLY)
                                        acct_auto_close(sb->s_dev);
                                retval = do_remount_sb(sb, flags, data);
                        }
                }
                dput(dentry);
        }
        return retval;
}

static int copy_mount_options (const void * data, unsigned long *where)
{
        int i;
        unsigned long page;
        struct vm_area_struct * vma;

        *where = 0;
        if (!data)
                return 0;

        /* If this is the kernel, just trust the pointer. */
        if (segment_eq(get_fs(), KERNEL_DS)) {
                *where = (unsigned long) data;
                return 0;
        }

        vma = find_vma(current->mm, (unsigned long) data);
        if (!vma || (unsigned long) data < vma->vm_start)
                return -EFAULT;
        if (!(vma->vm_flags & VM_READ))

                return -EFAULT;
        i = vma->vm_end - (unsigned long) data;
        if (PAGE_SIZE <= (unsigned long) i)
                i = PAGE_SIZE-1;
        if (!(page = __get_free_page(GFP_KERNEL))) {
                return -ENOMEM;
        }
        if (copy_from_user((void *) page,data,i)) {
                free_page(page); 
                return -EFAULT;
        }
        *where = page;
        return 0;
}

static void free_mount_page(unsigned long page)
{
        if (segment_eq(get_fs(), KERNEL_DS))
                return;
        free_page(page);
}

/*
 * Flags is a 16-bit value that allows up to 16 non-fs dependent flags to
 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
 *
 * data is a (void *) that can point to any structure up to
 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
 * information (or be NULL).
 *
 * NOTE! As old versions of mount() didn't use this setup, the flags
 * have to have a special 16-bit magic number in the high word:
 * 0xC0ED. If this magic word isn't present, the flags and data info
 * aren't used, as the syscall assumes we are talking to an older
 * version that didn't understand them.
 */
asmlinkage int sys_mount(char * dev_name, char * dir_name, char * type,
        unsigned long new_flags, void * data)
{
        struct file_system_type * fstype;
        struct dentry * dentry = NULL;
        struct inode * inode = NULL;
        kdev_t dev;
        int retval = -EPERM;
        unsigned long flags = 0;
        unsigned long page = 0;
        struct file dummy;      /* allows read-write or read-only flag */

        lock_kernel();
        if (!capable(CAP_SYS_ADMIN))
                goto out;
        if ((new_flags &
             (MS_MGC_MSK | MS_REMOUNT)) == (MS_MGC_VAL | MS_REMOUNT)) {
                retval = copy_mount_options (data, &page);
                if (retval < 0)
                        goto out;
                retval = do_remount(dir_name,
                                    new_flags & ~MS_MGC_MSK & ~MS_REMOUNT,
                                    (char *) page);
                free_mount_page(page);
                goto out;
        }

        retval = copy_mount_options (type, &page);
        if (retval < 0)
                goto out;
        fstype = get_fs_type((char *) page);
        free_mount_page(page);
        retval = -ENODEV;
        if (!fstype)            
                goto out;

        memset(&dummy, 0, sizeof(dummy));
        if (fstype->fs_flags & FS_REQUIRES_DEV) {
                dentry = namei(dev_name);
                retval = PTR_ERR(dentry);
                if (IS_ERR(dentry))
                        goto out;

                inode = dentry->d_inode;
                retval = -ENOTBLK;
                if (!S_ISBLK(inode->i_mode))
                        goto dput_and_out;

                retval = -EACCES;
                if (IS_NODEV(inode))
                        goto dput_and_out;

                dev = inode->i_rdev;
                retval = -ENXIO;
                if (MAJOR(dev) >= MAX_BLKDEV)
                        goto dput_and_out;

                retval = -ENOTBLK;
                dummy.f_op = get_blkfops(MAJOR(dev));
                if (!dummy.f_op)
                        goto dput_and_out;

                if (dummy.f_op->open) {
                        dummy.f_dentry = dentry;
                        dummy.f_mode = (new_flags & MS_RDONLY) ? 1 : 3;
                        retval = dummy.f_op->open(inode, &dummy);
                        if (retval)
                                goto dput_and_out;
                }

        } else {
                retval = -EMFILE;
                if (!(dev = get_unnamed_dev()))
                        goto out;
        }

        page = 0;
        if ((new_flags & MS_MGC_MSK) == MS_MGC_VAL) {
                flags = new_flags & ~MS_MGC_MSK;
                retval = copy_mount_options(data, &page);
                if (retval < 0)
                        goto clean_up;
        }
        retval = do_mount(dev, dev_name, dir_name, fstype->name, flags,
                                (void *) page);
        free_mount_page(page);
        if (retval)
                goto clean_up;

dput_and_out:
        dput(dentry);
out:
        unlock_kernel();
        return retval;

clean_up:
        if (dummy.f_op) {
                if (dummy.f_op->release)
                        dummy.f_op->release(inode, NULL);
        } else
                put_unnamed_dev(dev);
        goto dput_and_out;
}

void __init mount_root(void)
{
        struct file_system_type * fs_type;
        struct super_block * sb;
        struct vfsmount *vfsmnt;
        struct inode * d_inode = NULL;
        struct file filp;
        int retval;

#ifdef CONFIG_ROOT_NFS
        if (MAJOR(ROOT_DEV) == UNNAMED_MAJOR) {
                ROOT_DEV = 0;
                if ((fs_type = get_fs_type("nfs"))) {
                        sb = get_empty_super(); /* "can't fail" */
                        sb->s_dev = get_unnamed_dev();
                        sb->s_flags = root_mountflags;
                        sema_init(&sb->s_vfs_rename_sem,1);
                        sema_init(&sb->s_nfsd_free_path_sem,1);
                        vfsmnt = add_vfsmnt(sb, "/dev/root", "/");
                        if (vfsmnt) {
                                if (nfs_root_mount(sb) >= 0) {
                                        sb->s_dirt = 0;
                                        sb->s_type = fs_type;
                                        current->fs->root = dget(sb->s_root);
                                        current->fs->pwd = dget(sb->s_root);
                                        ROOT_DEV = sb->s_dev;
                                        printk (KERN_NOTICE "VFS: Mounted root (NFS filesystem)%s.\n", (sb->s_flags & MS_RDONLY) ? " readonly" : "");
                                        return;
                                }
                                remove_vfsmnt(sb->s_dev);
                        }
                        put_unnamed_dev(sb->s_dev);
                        sb->s_dev = 0;
                }
                if (!ROOT_DEV) {
                        printk(KERN_ERR "VFS: Unable to mount root fs via NFS, trying floppy.\n");
                        ROOT_DEV = MKDEV(FLOPPY_MAJOR, 0);
                }
        }
#endif

#ifdef CONFIG_BLK_DEV_FD
        if (MAJOR(ROOT_DEV) == FLOPPY_MAJOR) {
#ifdef CONFIG_BLK_DEV_RAM       
                extern int rd_doload;
#endif          
                floppy_eject();
#ifndef CONFIG_BLK_DEV_RAM
                printk(KERN_NOTICE "(Warning, this kernel has no ramdisk support)\n");
#else
                /* rd_doload is 2 for a dual initrd/ramload setup */
                if(rd_doload==2)
                        rd_load_secondary();
                else
#endif          
                {
                        printk(KERN_NOTICE "VFS: Insert root floppy and press ENTER\n");
                        wait_for_keypress();
                }
        }
#endif

        memset(&filp, 0, sizeof(filp));
        d_inode = get_empty_inode();
        d_inode->i_rdev = ROOT_DEV;
        filp.f_dentry = NULL;
        if ( root_mountflags & MS_RDONLY)
                filp.f_mode = 1; /* read only */
        else
                filp.f_mode = 3; /* read write */
        retval = blkdev_open(d_inode, &filp);
        if (retval == -EROFS) {
                root_mountflags |= MS_RDONLY;
                filp.f_mode = 1;
                retval = blkdev_open(d_inode, &filp);
        }
        iput(d_inode);
        if (retval)
                /*
                 * Allow the user to distinguish between failed open
                 * and bad superblock on root device.
                 */
                printk("VFS: Cannot open root device %s\n",
                       kdevname(ROOT_DEV));
        else for (fs_type = file_systems ; fs_type ; fs_type = fs_type->next) {
                if (!(fs_type->fs_flags & FS_REQUIRES_DEV))
                        continue;
                sb = read_super(ROOT_DEV,fs_type->name,root_mountflags,NULL,1);
                if (sb) {
                        sb->s_flags = root_mountflags;
                        current->fs->root = dget(sb->s_root);
                        current->fs->pwd = dget(sb->s_root);
                        printk ("VFS: Mounted root (%s filesystem)%s.\n",
                                fs_type->name,
                                (sb->s_flags & MS_RDONLY) ? " readonly" : "");
                        vfsmnt = add_vfsmnt(sb, "/dev/root", "/");
                        if (vfsmnt)
                                return;
                        panic("VFS: add_vfsmnt failed for root fs");
                }
        }
        panic("VFS: Unable to mount root fs on %s",
                kdevname(ROOT_DEV));
}


#ifdef CONFIG_BLK_DEV_INITRD

int __init change_root(kdev_t new_root_dev,const char *put_old)
{
        kdev_t old_root_dev;
        struct vfsmount *vfsmnt;
        struct dentry *old_root,*old_pwd,*dir_d = NULL;
        int error;

        old_root = current->fs->root;
        old_pwd = current->fs->pwd;
        old_root_dev = ROOT_DEV;
        if (!fs_may_mount(new_root_dev)) {
                printk(KERN_CRIT "New root is busy. Staying in initrd.\n");
                return -EBUSY;
        }
        ROOT_DEV = new_root_dev;
        mount_root();
        dput(old_root);
        dput(old_pwd);
#if 1
        shrink_dcache();
        printk("change_root: old root has d_count=%d\n", old_root->d_count);
#endif
        /*
         * Get the new mount directory
         */
        dir_d = lookup_dentry(put_old, NULL, 1);
        if (IS_ERR(dir_d)) {
                error = PTR_ERR(dir_d);
        } else if (!dir_d->d_inode) {
                dput(dir_d);
                error = -ENOENT;
        } else {
                error = 0;
        }
        if (!error && dir_d->d_covers != dir_d) {
                dput(dir_d);
                error = -EBUSY;
        }
        if (!error && !S_ISDIR(dir_d->d_inode->i_mode)) {
                dput(dir_d);
                error = -ENOTDIR;
        }
        if (error) {
                int umount_error;

                printk(KERN_NOTICE "Trying to unmount old root ... ");
                umount_error = do_umount(old_root_dev,1, 0);
                if (!umount_error) {
                        printk("okay\n");
                        /* 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(old_root_dev);
                        return 0;
                }
                printk(KERN_ERR "error %d\n",umount_error);
                return error;
        }
        remove_vfsmnt(old_root_dev);
        vfsmnt = add_vfsmnt(old_root->d_sb, "/dev/root.old", put_old);
        if (vfsmnt) {
                d_mount(dir_d,old_root);
                return 0;
        }
        printk(KERN_CRIT "Trouble: add_vfsmnt failed\n");
        return -ENOMEM;
}

#endif