linuxvfs.c

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/*
 * linux/fs/befs/linuxvfs.c
 *
 * Copyright (C) 2001 Will Dyson <[email protected]
 *
 */

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/stat.h>
#include <linux/nls.h>
#include <linux/buffer_head.h>
#include <linux/vfs.h>
#include <linux/parser.h>
#include <linux/namei.h>
#include <linux/sched.h>

#include "befs.h"
#include "btree.h"
#include "inode.h"
#include "datastream.h"
#include "super.h"
#include "io.h"

MODULE_DESCRIPTION("BeOS File System (BeFS) driver");
MODULE_AUTHOR("Will Dyson");
MODULE_LICENSE("GPL");

/* The units the vfs expects inode->i_blocks to be in */
#define VFS_BLOCK_SIZE 512

static int befs_readdir(struct file *, void *, filldir_t);
static int befs_get_block(struct inode *, sector_t, struct buffer_head *, int);
static int befs_readpage(struct file *file, struct page *page);
static sector_t befs_bmap(struct address_space *mapping, sector_t block);
static struct dentry *befs_lookup(struct inode *, struct dentry *, unsigned int);
static struct inode *befs_iget(struct super_block *, unsigned long);
static struct inode *befs_alloc_inode(struct super_block *sb);
static void befs_destroy_inode(struct inode *inode);
static int befs_init_inodecache(void);
static void befs_destroy_inodecache(void);
static void *befs_follow_link(struct dentry *, struct nameidata *);
static void befs_put_link(struct dentry *, struct nameidata *, void *);
static int befs_utf2nls(struct super_block *sb, const char *in, int in_len,
            char **out, int *out_len);
static int befs_nls2utf(struct super_block *sb, const char *in, int in_len,
            char **out, int *out_len);
static void befs_put_super(struct super_block *);
static int befs_remount(struct super_block *, int *, char *);
static int befs_statfs(struct dentry *, struct kstatfs *);
static int parse_options(char *, befs_mount_options *);

static const struct super_operations befs_sops = {
    .alloc_inode    = befs_alloc_inode, /* allocate a new inode */
    .destroy_inode  = befs_destroy_inode, /* deallocate an inode */
    .put_super  = befs_put_super,   /* uninit super */
    .statfs     = befs_statfs,  /* statfs */
    .remount_fs = befs_remount,
    .show_options   = generic_show_options,
};

/* slab cache for befs_inode_info objects */
static struct kmem_cache *befs_inode_cachep;

static const struct file_operations befs_dir_operations = {
    .read       = generic_read_dir,
    .readdir    = befs_readdir,
    .llseek     = generic_file_llseek,
};

static const struct inode_operations befs_dir_inode_operations = {
    .lookup     = befs_lookup,
};

static const struct address_space_operations befs_aops = {
    .readpage   = befs_readpage,
    .bmap       = befs_bmap,
};

static const struct inode_operations befs_symlink_inode_operations = {
    .readlink   = generic_readlink,
    .follow_link    = befs_follow_link,
    .put_link   = befs_put_link,
};

/* 
 * Called by generic_file_read() to read a page of data
 * 
 * In turn, simply calls a generic block read function and
 * passes it the address of befs_get_block, for mapping file
 * positions to disk blocks.
 */
static int
befs_readpage(struct file *file, struct page *page)
{
    return block_read_full_page(page, befs_get_block);
}

static sector_t
befs_bmap(struct address_space *mapping, sector_t block)
{
    return generic_block_bmap(mapping, block, befs_get_block);
}

/* 
 * Generic function to map a file position (block) to a 
 * disk offset (passed back in bh_result).
 *
 * Used by many higher level functions.
 *
 * Calls befs_fblock2brun() in datastream.c to do the real work.
 *
 * -WD 10-26-01
 */

static int
befs_get_block(struct inode *inode, sector_t block,
           struct buffer_head *bh_result, int create)
{
    struct super_block *sb = inode->i_sb;
    befs_data_stream *ds = &BEFS_I(inode)->i_data.ds;
    befs_block_run run = BAD_IADDR;
    int res = 0;
    ulong disk_off;

    befs_debug(sb, "---> befs_get_block() for inode %lu, block %ld",
           inode->i_ino, block);

    if (block < 0) {
        befs_error(sb, "befs_get_block() was asked for a block "
               "number less than zero: block %ld in inode %lu",
               block, inode->i_ino);
        return -EIO;
    }

    if (create) {
        befs_error(sb, "befs_get_block() was asked to write to "
               "block %ld in inode %lu", block, inode->i_ino);
        return -EPERM;
    }

    res = befs_fblock2brun(sb, ds, block, &run);
    if (res != BEFS_OK) {
        befs_error(sb,
               "<--- befs_get_block() for inode %lu, block "
               "%ld ERROR", inode->i_ino, block);
        return -EFBIG;
    }

    disk_off = (ulong) iaddr2blockno(sb, &run);

    map_bh(bh_result, inode->i_sb, disk_off);

    befs_debug(sb, "<--- befs_get_block() for inode %lu, block %ld, "
           "disk address %lu", inode->i_ino, block, disk_off);

    return 0;
}

static struct dentry *
befs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
{
    struct inode *inode = NULL;
    struct super_block *sb = dir->i_sb;
    befs_data_stream *ds = &BEFS_I(dir)->i_data.ds;
    befs_off_t offset;
    int ret;
    int utfnamelen;
    char *utfname;
    const char *name = dentry->d_name.name;

    befs_debug(sb, "---> befs_lookup() "
           "name %s inode %ld", dentry->d_name.name, dir->i_ino);

    /* Convert to UTF-8 */
    if (BEFS_SB(sb)->nls) {
        ret =
            befs_nls2utf(sb, name, strlen(name), &utfname, &utfnamelen);
        if (ret < 0) {
            befs_debug(sb, "<--- befs_lookup() ERROR");
            return ERR_PTR(ret);
        }
        ret = befs_btree_find(sb, ds, utfname, &offset);
        kfree(utfname);

    } else {
        ret = befs_btree_find(sb, ds, dentry->d_name.name, &offset);
    }

    if (ret == BEFS_BT_NOT_FOUND) {
        befs_debug(sb, "<--- befs_lookup() %s not found",
               dentry->d_name.name);
        return ERR_PTR(-ENOENT);

    } else if (ret != BEFS_OK || offset == 0) {
        befs_warning(sb, "<--- befs_lookup() Error");
        return ERR_PTR(-ENODATA);
    }

    inode = befs_iget(dir->i_sb, (ino_t) offset);
    if (IS_ERR(inode))
        return ERR_CAST(inode);

    d_add(dentry, inode);

    befs_debug(sb, "<--- befs_lookup()");

    return NULL;
}

static int
befs_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
    struct inode *inode = filp->f_path.dentry->d_inode;
    struct super_block *sb = inode->i_sb;
    befs_data_stream *ds = &BEFS_I(inode)->i_data.ds;
    befs_off_t value;
    int result;
    size_t keysize;
    unsigned char d_type;
    char keybuf[BEFS_NAME_LEN + 1];
    char *nlsname;
    int nlsnamelen;
    const char *dirname = filp->f_path.dentry->d_name.name;

    befs_debug(sb, "---> befs_readdir() "
           "name %s, inode %ld, filp->f_pos %Ld",
           dirname, inode->i_ino, filp->f_pos);

    result = befs_btree_read(sb, ds, filp->f_pos, BEFS_NAME_LEN + 1,
                 keybuf, &keysize, &value);

    if (result == BEFS_ERR) {
        befs_debug(sb, "<--- befs_readdir() ERROR");
        befs_error(sb, "IO error reading %s (inode %lu)",
               dirname, inode->i_ino);
        return -EIO;

    } else if (result == BEFS_BT_END) {
        befs_debug(sb, "<--- befs_readdir() END");
        return 0;

    } else if (result == BEFS_BT_EMPTY) {
        befs_debug(sb, "<--- befs_readdir() Empty directory");
        return 0;
    }

    d_type = DT_UNKNOWN;

    /* Convert to NLS */
    if (BEFS_SB(sb)->nls) {
        result =
            befs_utf2nls(sb, keybuf, keysize, &nlsname, &nlsnamelen);
        if (result < 0) {
            befs_debug(sb, "<--- befs_readdir() ERROR");
            return result;
        }
        result = filldir(dirent, nlsname, nlsnamelen, filp->f_pos,
                 (ino_t) value, d_type);
        kfree(nlsname);

    } else {
        result = filldir(dirent, keybuf, keysize, filp->f_pos,
                 (ino_t) value, d_type);
    }

    filp->f_pos++;

    befs_debug(sb, "<--- befs_readdir() filp->f_pos %Ld", filp->f_pos);

    return 0;
}

static struct inode *
befs_alloc_inode(struct super_block *sb)
{
        struct befs_inode_info *bi;
        bi = (struct befs_inode_info *)kmem_cache_alloc(befs_inode_cachep,
                            GFP_KERNEL);
        if (!bi)
                return NULL;
        return &bi->vfs_inode;
}

static void befs_i_callback(struct rcu_head *head)
{
    struct inode *inode = container_of(head, struct inode, i_rcu);
        kmem_cache_free(befs_inode_cachep, BEFS_I(inode));
}

static void befs_destroy_inode(struct inode *inode)
{
    call_rcu(&inode->i_rcu, befs_i_callback);
}

static void init_once(void *foo)
{
        struct befs_inode_info *bi = (struct befs_inode_info *) foo;

    inode_init_once(&bi->vfs_inode);
}

static struct inode *befs_iget(struct super_block *sb, unsigned long ino)
{
    struct buffer_head *bh = NULL;
    befs_inode *raw_inode = NULL;

    befs_sb_info *befs_sb = BEFS_SB(sb);
    befs_inode_info *befs_ino = NULL;
    struct inode *inode;
    long ret = -EIO;

    befs_debug(sb, "---> befs_read_inode() " "inode = %lu", ino);

    inode = iget_locked(sb, ino);
    if (IS_ERR(inode))
        return inode;
    if (!(inode->i_state & I_NEW))
        return inode;

    befs_ino = BEFS_I(inode);

    /* convert from vfs's inode number to befs's inode number */
    befs_ino->i_inode_num = blockno2iaddr(sb, inode->i_ino);

    befs_debug(sb, "  real inode number [%u, %hu, %hu]",
           befs_ino->i_inode_num.allocation_group,
           befs_ino->i_inode_num.start, befs_ino->i_inode_num.len);

    bh = befs_bread(sb, inode->i_ino);
    if (!bh) {
        befs_error(sb, "unable to read inode block - "
               "inode = %lu", inode->i_ino);
        goto unacquire_none;
    }

    raw_inode = (befs_inode *) bh->b_data;

    befs_dump_inode(sb, raw_inode);

    if (befs_check_inode(sb, raw_inode, inode->i_ino) != BEFS_OK) {
        befs_error(sb, "Bad inode: %lu", inode->i_ino);
        goto unacquire_bh;
    }

    inode->i_mode = (umode_t) fs32_to_cpu(sb, raw_inode->mode);

    /*
     * set uid and gid.  But since current BeOS is single user OS, so
     * you can change by "uid" or "gid" options.
     */   

    inode->i_uid = befs_sb->mount_opts.use_uid ?
        befs_sb->mount_opts.uid :
        make_kuid(&init_user_ns, fs32_to_cpu(sb, raw_inode->uid));
    inode->i_gid = befs_sb->mount_opts.use_gid ?
        befs_sb->mount_opts.gid :
        make_kgid(&init_user_ns, fs32_to_cpu(sb, raw_inode->gid));

    set_nlink(inode, 1);

    /*
     * BEFS's time is 64 bits, but current VFS is 32 bits...
     * BEFS don't have access time. Nor inode change time. VFS
     * doesn't have creation time.
     * Also, the lower 16 bits of the last_modified_time and 
     * create_time are just a counter to help ensure uniqueness
     * for indexing purposes. (PFD, page 54)
     */

    inode->i_mtime.tv_sec =
        fs64_to_cpu(sb, raw_inode->last_modified_time) >> 16;
    inode->i_mtime.tv_nsec = 0;   /* lower 16 bits are not a time */    
    inode->i_ctime = inode->i_mtime;
    inode->i_atime = inode->i_mtime;

    befs_ino->i_inode_num = fsrun_to_cpu(sb, raw_inode->inode_num);
    befs_ino->i_parent = fsrun_to_cpu(sb, raw_inode->parent);
    befs_ino->i_attribute = fsrun_to_cpu(sb, raw_inode->attributes);
    befs_ino->i_flags = fs32_to_cpu(sb, raw_inode->flags);

    if (S_ISLNK(inode->i_mode) && !(befs_ino->i_flags & BEFS_LONG_SYMLINK)){
        inode->i_size = 0;
        inode->i_blocks = befs_sb->block_size / VFS_BLOCK_SIZE;
        strncpy(befs_ino->i_data.symlink, raw_inode->data.symlink,
            BEFS_SYMLINK_LEN - 1);
        befs_ino->i_data.symlink[BEFS_SYMLINK_LEN - 1] = '\0';
    } else {
        int num_blks;

        befs_ino->i_data.ds =
            fsds_to_cpu(sb, &raw_inode->data.datastream);

        num_blks = befs_count_blocks(sb, &befs_ino->i_data.ds);
        inode->i_blocks =
            num_blks * (befs_sb->block_size / VFS_BLOCK_SIZE);
        inode->i_size = befs_ino->i_data.ds.size;
    }

    inode->i_mapping->a_ops = &befs_aops;

    if (S_ISREG(inode->i_mode)) {
        inode->i_fop = &generic_ro_fops;
    } else if (S_ISDIR(inode->i_mode)) {
        inode->i_op = &befs_dir_inode_operations;
        inode->i_fop = &befs_dir_operations;
    } else if (S_ISLNK(inode->i_mode)) {
        inode->i_op = &befs_symlink_inode_operations;
    } else {
        befs_error(sb, "Inode %lu is not a regular file, "
               "directory or symlink. THAT IS WRONG! BeFS has no "
               "on disk special files", inode->i_ino);
        goto unacquire_bh;
    }

    brelse(bh);
    befs_debug(sb, "<--- befs_read_inode()");
    unlock_new_inode(inode);
    return inode;

      unacquire_bh:
    brelse(bh);

      unacquire_none:
    iget_failed(inode);
    befs_debug(sb, "<--- befs_read_inode() - Bad inode");
    return ERR_PTR(ret);
}

/* Initialize the inode cache. Called at fs setup.
 *
 * Taken from NFS implementation by Al Viro.
 */
static int
befs_init_inodecache(void)
{
    befs_inode_cachep = kmem_cache_create("befs_inode_cache",
                          sizeof (struct befs_inode_info),
                          0, (SLAB_RECLAIM_ACCOUNT|
                        SLAB_MEM_SPREAD),
                          init_once);
    if (befs_inode_cachep == NULL) {
        printk(KERN_ERR "befs_init_inodecache: "
               "Couldn't initialize inode slabcache\n");
        return -ENOMEM;
    }

    return 0;
}

/* Called at fs teardown.
 * 
 * Taken from NFS implementation by Al Viro.
 */
static void
befs_destroy_inodecache(void)
{
    /*
     * Make sure all delayed rcu free inodes are flushed before we
     * destroy cache.
     */
    rcu_barrier();
    kmem_cache_destroy(befs_inode_cachep);
}

/*
 * The inode of symbolic link is different to data stream.
 * The data stream become link name. Unless the LONG_SYMLINK
 * flag is set.
 */
static void *
befs_follow_link(struct dentry *dentry, struct nameidata *nd)
{
    befs_inode_info *befs_ino = BEFS_I(dentry->d_inode);
    char *link;

    if (befs_ino->i_flags & BEFS_LONG_SYMLINK) {
        struct super_block *sb = dentry->d_sb;
        befs_data_stream *data = &befs_ino->i_data.ds;
        befs_off_t len = data->size;

        if (len == 0) {
            befs_error(sb, "Long symlink with illegal length");
            link = ERR_PTR(-EIO);
        } else {
            befs_debug(sb, "Follow long symlink");

            link = kmalloc(len, GFP_NOFS);
            if (!link) {
                link = ERR_PTR(-ENOMEM);
            } else if (befs_read_lsymlink(sb, data, link, len) != len) {
                kfree(link);
                befs_error(sb, "Failed to read entire long symlink");
                link = ERR_PTR(-EIO);
            } else {
                link[len - 1] = '\0';
            }
        }
    } else {
        link = befs_ino->i_data.symlink;
    }

    nd_set_link(nd, link);
    return NULL;
}

static void befs_put_link(struct dentry *dentry, struct nameidata *nd, void *p)
{
    befs_inode_info *befs_ino = BEFS_I(dentry->d_inode);
    if (befs_ino->i_flags & BEFS_LONG_SYMLINK) {
        char *link = nd_get_link(nd);
        if (!IS_ERR(link))
            kfree(link);
    }
}

/*
 * UTF-8 to NLS charset  convert routine
 * 
 *
 * Changed 8/10/01 by Will Dyson. Now use uni2char() / char2uni() rather than
 * the nls tables directly
 */

static int
befs_utf2nls(struct super_block *sb, const char *in,
         int in_len, char **out, int *out_len)
{
    struct nls_table *nls = BEFS_SB(sb)->nls;
    int i, o;
    unicode_t uni;
    int unilen, utflen;
    char *result;
    /* The utf8->nls conversion won't make the final nls string bigger
     * than the utf one, but if the string is pure ascii they'll have the
     * same width and an extra char is needed to save the additional \0
     */
    int maxlen = in_len + 1;

    befs_debug(sb, "---> utf2nls()");

    if (!nls) {
        befs_error(sb, "befs_utf2nls called with no NLS table loaded");
        return -EINVAL;
    }

    *out = result = kmalloc(maxlen, GFP_NOFS);
    if (!*out) {
        befs_error(sb, "befs_utf2nls() cannot allocate memory");
        *out_len = 0;
        return -ENOMEM;
    }

    for (i = o = 0; i < in_len; i += utflen, o += unilen) {

        /* convert from UTF-8 to Unicode */
        utflen = utf8_to_utf32(&in[i], in_len - i, &uni);
        if (utflen < 0)
            goto conv_err;

        /* convert from Unicode to nls */
        if (uni > MAX_WCHAR_T)
            goto conv_err;
        unilen = nls->uni2char(uni, &result[o], in_len - o);
        if (unilen < 0)
            goto conv_err;
    }
    result[o] = '\0';
    *out_len = o;

    befs_debug(sb, "<--- utf2nls()");

    return o;

      conv_err:
    befs_error(sb, "Name using character set %s contains a character that "
           "cannot be converted to unicode.", nls->charset);
    befs_debug(sb, "<--- utf2nls()");
    kfree(result);
    return -EILSEQ;
}

static int
befs_nls2utf(struct super_block *sb, const char *in,
         int in_len, char **out, int *out_len)
{
    struct nls_table *nls = BEFS_SB(sb)->nls;
    int i, o;
    wchar_t uni;
    int unilen, utflen;
    char *result;
    /* There're nls characters that will translate to 3-chars-wide UTF-8
     * characters, a additional byte is needed to save the final \0
     * in special cases */
    int maxlen = (3 * in_len) + 1;

    befs_debug(sb, "---> nls2utf()\n");

    if (!nls) {
        befs_error(sb, "befs_nls2utf called with no NLS table loaded.");
        return -EINVAL;
    }

    *out = result = kmalloc(maxlen, GFP_NOFS);
    if (!*out) {
        befs_error(sb, "befs_nls2utf() cannot allocate memory");
        *out_len = 0;
        return -ENOMEM;
    }

    for (i = o = 0; i < in_len; i += unilen, o += utflen) {

        /* convert from nls to unicode */
        unilen = nls->char2uni(&in[i], in_len - i, &uni);
        if (unilen < 0)
            goto conv_err;

        /* convert from unicode to UTF-8 */
        utflen = utf32_to_utf8(uni, &result[o], 3);
        if (utflen <= 0)
            goto conv_err;
    }

    result[o] = '\0';
    *out_len = o;

    befs_debug(sb, "<--- nls2utf()");

    return i;

      conv_err:
    befs_error(sb, "Name using charecter set %s contains a charecter that "
           "cannot be converted to unicode.", nls->charset);
    befs_debug(sb, "<--- nls2utf()");
    kfree(result);
    return -EILSEQ;
}

enum {
    Opt_uid, Opt_gid, Opt_charset, Opt_debug, Opt_err,
};

static const match_table_t befs_tokens = {
    {Opt_uid, "uid=%d"},
    {Opt_gid, "gid=%d"},
    {Opt_charset, "iocharset=%s"},
    {Opt_debug, "debug"},
    {Opt_err, NULL}
};

static int
parse_options(char *options, befs_mount_options * opts)
{
    char *p;
    substring_t args[MAX_OPT_ARGS];
    int option;
    kuid_t uid;
    kgid_t gid;

    /* Initialize options */
    opts->uid = GLOBAL_ROOT_UID;
    opts->gid = GLOBAL_ROOT_GID;
    opts->use_uid = 0;
    opts->use_gid = 0;
    opts->iocharset = NULL;
    opts->debug = 0;

    if (!options)
        return 1;

    while ((p = strsep(&options, ",")) != NULL) {
        int token;
        if (!*p)
            continue;

        token = match_token(p, befs_tokens, args);
        switch (token) {
        case Opt_uid:
            if (match_int(&args[0], &option))
                return 0;
            uid = INVALID_UID;
            if (option >= 0)
                uid = make_kuid(current_user_ns(), option);
            if (!uid_valid(uid)) {
                printk(KERN_ERR "BeFS: Invalid uid %d, "
                        "using default\n", option);
                break;
            }
            opts->uid = uid;
            opts->use_uid = 1;
            break;
        case Opt_gid:
            if (match_int(&args[0], &option))
                return 0;
            gid = INVALID_GID;
            if (option >= 0)
                gid = make_kgid(current_user_ns(), option);
            if (!gid_valid(gid)) {
                printk(KERN_ERR "BeFS: Invalid gid %d, "
                        "using default\n", option);
                break;
            }
            opts->gid = gid;
            opts->use_gid = 1;
            break;
        case Opt_charset:
            kfree(opts->iocharset);
            opts->iocharset = match_strdup(&args[0]);
            if (!opts->iocharset) {
                printk(KERN_ERR "BeFS: allocation failure for "
                        "iocharset string\n");
                return 0;
            }
            break;
        case Opt_debug:
            opts->debug = 1;
            break;
        default:
            printk(KERN_ERR "BeFS: Unrecognized mount option \"%s\" "
                    "or missing value\n", p);
            return 0;
        }
    }
    return 1;
}

/* This function has the responsibiltiy of getting the
 * filesystem ready for unmounting. 
 * Basically, we free everything that we allocated in
 * befs_read_inode
 */
static void
befs_put_super(struct super_block *sb)
{
    kfree(BEFS_SB(sb)->mount_opts.iocharset);
    BEFS_SB(sb)->mount_opts.iocharset = NULL;
    unload_nls(BEFS_SB(sb)->nls);
    kfree(sb->s_fs_info);
    sb->s_fs_info = NULL;
}

/* Allocate private field of the superblock, fill it.
 *
 * Finish filling the public superblock fields
 * Make the root directory
 * Load a set of NLS translations if needed.
 */
static int
befs_fill_super(struct super_block *sb, void *data, int silent)
{
    struct buffer_head *bh;
    befs_sb_info *befs_sb;
    befs_super_block *disk_sb;
    struct inode *root;
    long ret = -EINVAL;
    const unsigned long sb_block = 0;
    const off_t x86_sb_off = 512;

    save_mount_options(sb, data);

    sb->s_fs_info = kmalloc(sizeof (*befs_sb), GFP_KERNEL);
    if (sb->s_fs_info == NULL) {
        printk(KERN_ERR
               "BeFS(%s): Unable to allocate memory for private "
               "portion of superblock. Bailing.\n", sb->s_id);
        goto unacquire_none;
    }
    befs_sb = BEFS_SB(sb);
    memset(befs_sb, 0, sizeof(befs_sb_info));

    if (!parse_options((char *) data, &befs_sb->mount_opts)) {
        befs_error(sb, "cannot parse mount options");
        goto unacquire_priv_sbp;
    }

    befs_debug(sb, "---> befs_fill_super()");

#ifndef CONFIG_BEFS_RW
    if (!(sb->s_flags & MS_RDONLY)) {
        befs_warning(sb,
                 "No write support. Marking filesystem read-only");
        sb->s_flags |= MS_RDONLY;
    }
#endif              /* CONFIG_BEFS_RW */

    /*
     * Set dummy blocksize to read super block.
     * Will be set to real fs blocksize later.
     *
     * Linux 2.4.10 and later refuse to read blocks smaller than
     * the hardsect size for the device. But we also need to read at 
     * least 1k to get the second 512 bytes of the volume.
     * -WD 10-26-01
     */ 
    sb_min_blocksize(sb, 1024);

    if (!(bh = sb_bread(sb, sb_block))) {
        befs_error(sb, "unable to read superblock");
        goto unacquire_priv_sbp;
    }

    /* account for offset of super block on x86 */
    disk_sb = (befs_super_block *) bh->b_data;
    if ((disk_sb->magic1 == BEFS_SUPER_MAGIC1_LE) ||
        (disk_sb->magic1 == BEFS_SUPER_MAGIC1_BE)) {
        befs_debug(sb, "Using PPC superblock location");
    } else {
        befs_debug(sb, "Using x86 superblock location");
        disk_sb =
            (befs_super_block *) ((void *) bh->b_data + x86_sb_off);
    }

    if (befs_load_sb(sb, disk_sb) != BEFS_OK)
        goto unacquire_bh;

    befs_dump_super_block(sb, disk_sb);

    brelse(bh);

    if (befs_check_sb(sb) != BEFS_OK)
        goto unacquire_priv_sbp;

    if( befs_sb->num_blocks > ~((sector_t)0) ) {
        befs_error(sb, "blocks count: %Lu "
            "is larger than the host can use",
            befs_sb->num_blocks);
        goto unacquire_priv_sbp;
    }

    /*
     * set up enough so that it can read an inode
     * Fill in kernel superblock fields from private sb
     */
    sb->s_magic = BEFS_SUPER_MAGIC;
    /* Set real blocksize of fs */
    sb_set_blocksize(sb, (ulong) befs_sb->block_size);
    sb->s_op = &befs_sops;
    root = befs_iget(sb, iaddr2blockno(sb, &(befs_sb->root_dir)));
    if (IS_ERR(root)) {
        ret = PTR_ERR(root);
        goto unacquire_priv_sbp;
    }
    sb->s_root = d_make_root(root);
    if (!sb->s_root) {
        befs_error(sb, "get root inode failed");
        goto unacquire_priv_sbp;
    }

    /* load nls library */
    if (befs_sb->mount_opts.iocharset) {
        befs_debug(sb, "Loading nls: %s",
               befs_sb->mount_opts.iocharset);
        befs_sb->nls = load_nls(befs_sb->mount_opts.iocharset);
        if (!befs_sb->nls) {
            befs_warning(sb, "Cannot load nls %s"
                    " loading default nls",
                    befs_sb->mount_opts.iocharset);
            befs_sb->nls = load_nls_default();
        }
    /* load default nls if none is specified  in mount options */
    } else {
        befs_debug(sb, "Loading default nls");
        befs_sb->nls = load_nls_default();
    }

    return 0;
/*****************/
      unacquire_bh:
    brelse(bh);

      unacquire_priv_sbp:
    kfree(befs_sb->mount_opts.iocharset);
    kfree(sb->s_fs_info);

      unacquire_none:
    sb->s_fs_info = NULL;
    return ret;
}

static int
befs_remount(struct super_block *sb, int *flags, char *data)
{
    if (!(*flags & MS_RDONLY))
        return -EINVAL;
    return 0;
}

static int
befs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
    struct super_block *sb = dentry->d_sb;
    u64 id = huge_encode_dev(sb->s_bdev->bd_dev);

    befs_debug(sb, "---> befs_statfs()");

    buf->f_type = BEFS_SUPER_MAGIC;
    buf->f_bsize = sb->s_blocksize;
    buf->f_blocks = BEFS_SB(sb)->num_blocks;
    buf->f_bfree = BEFS_SB(sb)->num_blocks - BEFS_SB(sb)->used_blocks;
    buf->f_bavail = buf->f_bfree;
    buf->f_files = 0;   /* UNKNOWN */
    buf->f_ffree = 0;   /* UNKNOWN */
    buf->f_fsid.val[0] = (u32)id;
    buf->f_fsid.val[1] = (u32)(id >> 32);
    buf->f_namelen = BEFS_NAME_LEN;

    befs_debug(sb, "<--- befs_statfs()");

    return 0;
}

static struct dentry *
befs_mount(struct file_system_type *fs_type, int flags, const char *dev_name,
        void *data)
{
    return mount_bdev(fs_type, flags, dev_name, data, befs_fill_super);
}

static struct file_system_type befs_fs_type = {
    .owner      = THIS_MODULE,
    .name       = "befs",
    .mount      = befs_mount,
    .kill_sb    = kill_block_super,
    .fs_flags   = FS_REQUIRES_DEV,  
};

static int __init
init_befs_fs(void)
{
    int err;

    printk(KERN_INFO "BeFS version: %s\n", BEFS_VERSION);

    err = befs_init_inodecache();
    if (err)
        goto unacquire_none;

    err = register_filesystem(&befs_fs_type);
    if (err)
        goto unacquire_inodecache;

    return 0;

unacquire_inodecache:
    befs_destroy_inodecache();

unacquire_none:
    return err;
}

static void __exit
exit_befs_fs(void)
{
    befs_destroy_inodecache();

    unregister_filesystem(&befs_fs_type);
}

/*
Macros that typecheck the init and exit functions,
ensures that they are called at init and cleanup,
and eliminates warnings about unused functions.
*/
module_init(init_befs_fs)
module_exit(exit_befs_fs)