[PATCH] VFS: Permit filesystem to perform statfs with a known root dentry

[mirror_ubuntu-artful-kernel.git] / fs / befs / linuxvfs.c

/*
 * linux/fs/befs/linuxvfs.c
 *
 * Copyright (C) 2001 Will Dyson <will_dyson@pobox.com
 *
 */

#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 "befs.h"
#include "btree.h"
#include "inode.h"
#include "datastream.h"
#include "super.h"
#include "io.h"
#include "endian.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 *, struct nameidata *);
static void befs_read_inode(struct inode *ino);
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 = {
        .read_inode     = befs_read_inode,      /* initialize & read inode */
        .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,
};

/* slab cache for befs_inode_info objects */
static kmem_cache_t *befs_inode_cachep;

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

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

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

static 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, struct nameidata *nd)
{
        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 = iget(dir->i_sb, (ino_t) offset);
        if (!inode)
                return ERR_PTR(-EACCES);

        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_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_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,
                                                        SLAB_KERNEL);
        if (!bi)
                return NULL;
        return &bi->vfs_inode;
}

static void
befs_destroy_inode(struct inode *inode)
{
        kmem_cache_free(befs_inode_cachep, BEFS_I(inode));
}

static void init_once(void * foo, kmem_cache_t * cachep, unsigned long flags)
{
        struct befs_inode_info *bi = (struct befs_inode_info *) foo;
        
                if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
                            SLAB_CTOR_CONSTRUCTOR) {
                        inode_init_once(&bi->vfs_inode);
                }
}

static void
befs_read_inode(struct inode *inode)
{
        struct buffer_head *bh = NULL;
        befs_inode *raw_inode = NULL;

        struct super_block *sb = inode->i_sb;
        befs_sb_info *befs_sb = BEFS_SB(sb);
        befs_inode_info *befs_ino = NULL;

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

        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 unaquire_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 unaquire_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 : (uid_t) fs32_to_cpu(sb, raw_inode->uid);
        inode->i_gid = befs_sb->mount_opts.use_gid ?
            befs_sb->mount_opts.gid : (gid_t) fs32_to_cpu(sb, raw_inode->gid);

        inode->i_nlink = 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;
        inode->i_blksize = befs_sb->block_size;

        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);
        } 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 unaquire_bh;
        }

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

      unaquire_bh:
        brelse(bh);

      unaquire_none:
        make_bad_inode(inode);
        befs_debug(sb, "<--- befs_read_inode() - Bad inode");
        return;
}

/* 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, NULL);
        if (befs_inode_cachep == NULL) {
                printk(KERN_ERR "befs_init_inodecache: "
                       "Couldn't initalize inode slabcache\n");
                return -ENOMEM;
        }

        return 0;
}

/* Called at fs teardown.
 * 
 * Taken from NFS implementation by Al Viro.
 */
static void
befs_destroy_inodecache(void)
{
        if (kmem_cache_destroy(befs_inode_cachep))
                printk(KERN_ERR "befs_destroy_inodecache: "
                       "not all structures were freed\n");
}

/*
 * 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;

                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 = 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 *p = nd_get_link(nd);
                if (!IS_ERR(p))
                        kfree(p);
        }
}

/*
 * 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;
        wchar_t uni;
        int unilen, utflen;
        char *result;
        int maxlen = in_len; /* The utf8->nls conversion can't make more chars */

        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_mbtowc(&uni, &in[i], in_len - i);
                if (utflen < 0) {
                        goto conv_err;
                }

                /* convert from Unicode to nls */
                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;
}

/**
 * befs_nls2utf - Convert NLS string to utf8 encodeing
 * @sb: Superblock
 * @src: Input string buffer in NLS format
 * @srclen: Length of input string in bytes
 * @dest: The output string in UTF-8 format
 * @destlen: Length of the output buffer
 * 
 * Converts input string @src, which is in the format of the loaded NLS map,
 * into a utf8 string.
 * 
 * The destination string @dest is allocated by this function and the caller is
 * responsible for freeing it with kfree()
 * 
 * On return, *@destlen is the length of @dest in bytes.
 *
 * On success, the return value is the number of utf8 characters written to
 * the output buffer @dest.
 *  
 * On Failure, a negative number coresponding to the error code is returned.
 */

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;
        int maxlen = 3 * in_len;

        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 = utf8_wctomb(&result[o], uni, 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;
}

/**
 * Use the
 *
 */
enum {
        Opt_uid, Opt_gid, Opt_charset, Opt_debug, Opt_err,
};

static 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;

        /* Initialize options */
        opts->uid = 0;
        opts->gid = 0;
        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;
                        if (option < 0) {
                                printk(KERN_ERR "BeFS: Invalid uid %d, "
                                                "using default\n", option);
                                break;
                        }
                        opts->uid = option;
                        opts->use_uid = 1;
                        break;
                case Opt_gid:
                        if (match_int(&args[0], &option))
                                return 0;
                        if (option < 0) {
                                printk(KERN_ERR "BeFS: Invalid gid %d, "
                                                "using default\n", option);
                                break;
                        }
                        opts->gid = option;
                        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. 
 * Basicly, 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;

        if (BEFS_SB(sb)->nls) {
                unload_nls(BEFS_SB(sb)->nls);
                BEFS_SB(sb)->nls = NULL;
        }

        kfree(sb->s_fs_info);
        sb->s_fs_info = NULL;
        return;
}

/* 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;

        const unsigned long sb_block = 0;
        const off_t x86_sb_off = 512;

        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 unaquire_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 unaquire_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 unaquire_priv_sbp;
        }

        /* account for offset of super block on x86 */
        disk_sb = (befs_super_block *) bh->b_data;
        if ((le32_to_cpu(disk_sb->magic1) == BEFS_SUPER_MAGIC1) ||
            (be32_to_cpu(disk_sb->magic1) == BEFS_SUPER_MAGIC1)) {
                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 unaquire_bh;

        befs_dump_super_block(sb, disk_sb);

        brelse(bh);

        if (befs_check_sb(sb) != BEFS_OK)
                goto unaquire_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 unaquire_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 = (struct super_operations *) &befs_sops;
        root = iget(sb, iaddr2blockno(sb, &(befs_sb->root_dir)));
        sb->s_root = d_alloc_root(root);
        if (!sb->s_root) {
                iput(root);
                befs_error(sb, "get root inode failed");
                goto unaquire_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;
/*****************/
      unaquire_bh:
        brelse(bh);

      unaquire_priv_sbp:
        kfree(sb->s_fs_info);

      unaquire_none:
        sb->s_fs_info = NULL;
        return -EINVAL;
}

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;

        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_namelen = BEFS_NAME_LEN;

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

        return 0;
}

static int
befs_get_sb(struct file_system_type *fs_type, int flags, const char *dev_name,
            void *data, struct vfsmount *mnt)
{
        return get_sb_bdev(fs_type, flags, dev_name, data, befs_fill_super,
                           mnt);
}

static struct file_system_type befs_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "befs",
        .get_sb         = befs_get_sb,
        .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 unaquire_none;

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

        return 0;

unaquire_inodecache:
        befs_destroy_inodecache();

unaquire_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)