/*
 *  linux/fs/sysv/inode.c
 *
 *  minix/inode.c
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  xenix/inode.c
 *  Copyright (C) 1992  Doug Evans
 *
 *  coh/inode.c
 *  Copyright (C) 1993  Pascal Haible, Bruno Haible
 *
 *  sysv/inode.c
 *  Copyright (C) 1993  Paul B. Monday
 *
 *  sysv/inode.c
 *  Copyright (C) 1993  Bruno Haible
 *  Copyright (C) 1997, 1998  Krzysztof G. Baranowski
 *
 *  This file contains code for read/parsing the superblock.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/buffer_head.h>
#include "sysv.h"

/*
 * The following functions try to recognize specific filesystems.
 *
 * We recognize:
 * - Xenix FS by its magic number.
 * - SystemV FS by its magic number.
 * - Coherent FS by its funny fname/fpack field.
 * - SCO AFS by s_nfree == 0xffff
 * - V7 FS has no distinguishing features.
 *
 * We discriminate among SystemV4 and SystemV2 FS by the assumption that
 * the time stamp is not < 01-01-1980.
 */

enum {
        JAN_1_1980 = (10*365 + 2) * 24 * 60 * 60
};

static void detected_xenix(struct sysv_sb_info *sbi)
{
        struct buffer_head *bh1 = sbi->s_bh1;
        struct buffer_head *bh2 = sbi->s_bh2;
        struct xenix_super_block * sbd1;
        struct xenix_super_block * sbd2;

        if (bh1 != bh2)
                sbd1 = sbd2 = (struct xenix_super_block *) bh1->b_data;
        else {
                /* block size = 512, so bh1 != bh2 */
                sbd1 = (struct xenix_super_block *) bh1->b_data;
                sbd2 = (struct xenix_super_block *) (bh2->b_data - 512);
        }

        sbi->s_link_max = XENIX_LINK_MAX;
        sbi->s_fic_size = XENIX_NICINOD;
        sbi->s_flc_size = XENIX_NICFREE;
        sbi->s_sbd1 = (char *)sbd1;
        sbi->s_sbd2 = (char *)sbd2;
        sbi->s_sb_fic_count = &sbd1->s_ninode;
        sbi->s_sb_fic_inodes = &sbd1->s_inode[0];
        sbi->s_sb_total_free_inodes = &sbd2->s_tinode;
        sbi->s_bcache_count = &sbd1->s_nfree;
        sbi->s_bcache = &sbd1->s_free[0];
        sbi->s_free_blocks = &sbd2->s_tfree;
        sbi->s_sb_time = &sbd2->s_time;
        sbi->s_firstdatazone = fs16_to_cpu(sbi, sbd1->s_isize);
        sbi->s_nzones = fs32_to_cpu(sbi, sbd1->s_fsize);
}

static void detected_sysv4(struct sysv_sb_info *sbi)
{
        struct sysv4_super_block * sbd;
        struct buffer_head *bh1 = sbi->s_bh1;
        struct buffer_head *bh2 = sbi->s_bh2;

        if (bh1 == bh2)
                sbd = (struct sysv4_super_block *) (bh1->b_data + BLOCK_SIZE/2);
        else
                sbd = (struct sysv4_super_block *) bh2->b_data;

        sbi->s_link_max = SYSV_LINK_MAX;
        sbi->s_fic_size = SYSV_NICINOD;
        sbi->s_flc_size = SYSV_NICFREE;
        sbi->s_sbd1 = (char *)sbd;
        sbi->s_sbd2 = (char *)sbd;
        sbi->s_sb_fic_count = &sbd->s_ninode;
        sbi->s_sb_fic_inodes = &sbd->s_inode[0];
        sbi->s_sb_total_free_inodes = &sbd->s_tinode;
        sbi->s_bcache_count = &sbd->s_nfree;
        sbi->s_bcache = &sbd->s_free[0];
        sbi->s_free_blocks = &sbd->s_tfree;
        sbi->s_sb_time = &sbd->s_time;
        sbi->s_sb_state = &sbd->s_state;
        sbi->s_firstdatazone = fs16_to_cpu(sbi, sbd->s_isize);
        sbi->s_nzones = fs32_to_cpu(sbi, sbd->s_fsize);
}

static void detected_sysv2(struct sysv_sb_info *sbi)
{
        struct sysv2_super_block *sbd;
        struct buffer_head *bh1 = sbi->s_bh1;
        struct buffer_head *bh2 = sbi->s_bh2;

        if (bh1 == bh2)
                sbd = (struct sysv2_super_block *) (bh1->b_data + BLOCK_SIZE/2);
        else
                sbd = (struct sysv2_super_block *) bh2->b_data;

        sbi->s_link_max = SYSV_LINK_MAX;
        sbi->s_fic_size = SYSV_NICINOD;
        sbi->s_flc_size = SYSV_NICFREE;
        sbi->s_sbd1 = (char *)sbd;
        sbi->s_sbd2 = (char *)sbd;
        sbi->s_sb_fic_count = &sbd->s_ninode;
        sbi->s_sb_fic_inodes = &sbd->s_inode[0];
        sbi->s_sb_total_free_inodes = &sbd->s_tinode;
        sbi->s_bcache_count = &sbd->s_nfree;
        sbi->s_bcache = &sbd->s_free[0];
        sbi->s_free_blocks = &sbd->s_tfree;
        sbi->s_sb_time = &sbd->s_time;
        sbi->s_sb_state = &sbd->s_state;
        sbi->s_firstdatazone = fs16_to_cpu(sbi, sbd->s_isize);
        sbi->s_nzones = fs32_to_cpu(sbi, sbd->s_fsize);
}

static void detected_coherent(struct sysv_sb_info *sbi)
{
        struct coh_super_block * sbd;
        struct buffer_head *bh1 = sbi->s_bh1;

        sbd = (struct coh_super_block *) bh1->b_data;

        sbi->s_link_max = COH_LINK_MAX;
        sbi->s_fic_size = COH_NICINOD;
        sbi->s_flc_size = COH_NICFREE;
        sbi->s_sbd1 = (char *)sbd;
        sbi->s_sbd2 = (char *)sbd;
        sbi->s_sb_fic_count = &sbd->s_ninode;
        sbi->s_sb_fic_inodes = &sbd->s_inode[0];
        sbi->s_sb_total_free_inodes = &sbd->s_tinode;
        sbi->s_bcache_count = &sbd->s_nfree;
        sbi->s_bcache = &sbd->s_free[0];
        sbi->s_free_blocks = &sbd->s_tfree;
        sbi->s_sb_time = &sbd->s_time;
        sbi->s_firstdatazone = fs16_to_cpu(sbi, sbd->s_isize);
        sbi->s_nzones = fs32_to_cpu(sbi, sbd->s_fsize);
}

static void detected_v7(struct sysv_sb_info *sbi)
{
        struct buffer_head *bh2 = sbi->s_bh2;
        struct v7_super_block *sbd = (struct v7_super_block *)bh2->b_data;

        sbi->s_link_max = V7_LINK_MAX;
        sbi->s_fic_size = V7_NICINOD;
        sbi->s_flc_size = V7_NICFREE;
        sbi->s_sbd1 = (char *)sbd;
        sbi->s_sbd2 = (char *)sbd;
        sbi->s_sb_fic_count = &sbd->s_ninode;
        sbi->s_sb_fic_inodes = &sbd->s_inode[0];
        sbi->s_sb_total_free_inodes = &sbd->s_tinode;
        sbi->s_bcache_count = &sbd->s_nfree;
        sbi->s_bcache = &sbd->s_free[0];
        sbi->s_free_blocks = &sbd->s_tfree;
        sbi->s_sb_time = &sbd->s_time;
        sbi->s_firstdatazone = fs16_to_cpu(sbi, sbd->s_isize);
        sbi->s_nzones = fs32_to_cpu(sbi, sbd->s_fsize);
}

static int detect_xenix(struct sysv_sb_info *sbi, struct buffer_head *bh)
{
        struct xenix_super_block *sbd = (struct xenix_super_block *)bh->b_data;
        if (*(__le32 *)&sbd->s_magic == cpu_to_le32(0x2b5544))
                sbi->s_bytesex = BYTESEX_LE;
        else if (*(__be32 *)&sbd->s_magic == cpu_to_be32(0x2b5544))
                sbi->s_bytesex = BYTESEX_BE;
        else
                return 0;
        switch (fs32_to_cpu(sbi, sbd->s_type)) {
        case 1:
                sbi->s_type = FSTYPE_XENIX;
                return 1;
        case 2:
                sbi->s_type = FSTYPE_XENIX;
                return 2;
        default:
                return 0;
        }
}

static int detect_sysv(struct sysv_sb_info *sbi, struct buffer_head *bh)
{
        struct super_block *sb = sbi->s_sb;
        /* All relevant fields are at the same offsets in R2 and R4 */
        struct sysv4_super_block * sbd;
        u32 type;

        sbd = (struct sysv4_super_block *) (bh->b_data + BLOCK_SIZE/2);
        if (*(__le32 *)&sbd->s_magic == cpu_to_le32(0xfd187e20))
                sbi->s_bytesex = BYTESEX_LE;
        else if (*(__be32 *)&sbd->s_magic == cpu_to_be32(0xfd187e20))
                sbi->s_bytesex = BYTESEX_BE;
        else
                return 0;

        type = fs32_to_cpu(sbi, sbd->s_type);
 
        if (fs16_to_cpu(sbi, sbd->s_nfree) == 0xffff) {
                sbi->s_type = FSTYPE_AFS;
                sbi->s_forced_ro = 1;
                if (!(sb->s_flags & MS_RDONLY)) {
                        printk("SysV FS: SCO EAFS on %s detected, " 
                                "forcing read-only mode.\n", 
                                sb->s_id);
                }
                return type;
        }
 
        if (fs32_to_cpu(sbi, sbd->s_time) < JAN_1_1980) {
                /* this is likely to happen on SystemV2 FS */
                if (type > 3 || type < 1)
                        return 0;
                sbi->s_type = FSTYPE_SYSV2;
                return type;
        }
        if ((type > 3 || type < 1) && (type > 0x30 || type < 0x10))
                return 0;

        /* On Interactive Unix (ISC) Version 4.0/3.x s_type field = 0x10,
           0x20 or 0x30 indicates that symbolic links and the 14-character
           filename limit is gone. Due to lack of information about this
           feature read-only mode seems to be a reasonable approach... -KGB */

        if (type >= 0x10) {
                printk("SysV FS: can't handle long file names on %s, "
                       "forcing read-only mode.\n", sb->s_id);
                sbi->s_forced_ro = 1;
        }

        sbi->s_type = FSTYPE_SYSV4;
        return type >= 0x10 ? type >> 4 : type;
}

static int detect_coherent(struct sysv_sb_info *sbi, struct buffer_head *bh)
{
        struct coh_super_block * sbd;

        sbd = (struct coh_super_block *) (bh->b_data + BLOCK_SIZE/2);
        if ((memcmp(sbd->s_fname,"noname",6) && memcmp(sbd->s_fname,"xxxxx ",6))
            || (memcmp(sbd->s_fpack,"nopack",6) && memcmp(sbd->s_fpack,"xxxxx\n",6)))
                return 0;
        sbi->s_bytesex = BYTESEX_PDP;
        sbi->s_type = FSTYPE_COH;
        return 1;
}

static int detect_sysv_odd(struct sysv_sb_info *sbi, struct buffer_head *bh)
{
        int size = detect_sysv(sbi, bh);

        return size>2 ? 0 : size;
}

static struct {
        int block;
        int (*test)(struct sysv_sb_info *, struct buffer_head *);
} flavours[] = {
        {1, detect_xenix},
        {0, detect_sysv},
        {0, detect_coherent},
        {9, detect_sysv_odd},
        {15,detect_sysv_odd},
        {18,detect_sysv},
};

static char *flavour_names[] = {
        [FSTYPE_XENIX]  = "Xenix",
        [FSTYPE_SYSV4]  = "SystemV",
        [FSTYPE_SYSV2]  = "SystemV Release 2",
        [FSTYPE_COH]    = "Coherent",
        [FSTYPE_V7]     = "V7",
        [FSTYPE_AFS]    = "AFS",
};

static void (*flavour_setup[])(struct sysv_sb_info *) = {
        [FSTYPE_XENIX]  = detected_xenix,
        [FSTYPE_SYSV4]  = detected_sysv4,
        [FSTYPE_SYSV2]  = detected_sysv2,
        [FSTYPE_COH]    = detected_coherent,
        [FSTYPE_V7]     = detected_v7,
        [FSTYPE_AFS]    = detected_sysv4,
};

static int complete_read_super(struct super_block *sb, int silent, int size)
{
        struct sysv_sb_info *sbi = SYSV_SB(sb);
        struct inode *root_inode;
        char *found = flavour_names[sbi->s_type];
        u_char n_bits = size+8;
        int bsize = 1 << n_bits;
        int bsize_4 = bsize >> 2;

        sbi->s_firstinodezone = 2;

        flavour_setup[sbi->s_type](sbi);
        
        sbi->s_truncate = 1;
        sbi->s_ndatazones = sbi->s_nzones - sbi->s_firstdatazone;
        sbi->s_inodes_per_block = bsize >> 6;
        sbi->s_inodes_per_block_1 = (bsize >> 6)-1;
        sbi->s_inodes_per_block_bits = n_bits-6;
        sbi->s_ind_per_block = bsize_4;
        sbi->s_ind_per_block_2 = bsize_4*bsize_4;
        sbi->s_toobig_block = 10 + bsize_4 * (1 + bsize_4 * (1 + bsize_4));
        sbi->s_ind_per_block_bits = n_bits-2;

        sbi->s_ninodes = (sbi->s_firstdatazone - sbi->s_firstinodezone)
                << sbi->s_inodes_per_block_bits;

        if (!silent)
                printk("VFS: Found a %s FS (block size = %ld) on device %s\n",
                       found, sb->s_blocksize, sb->s_id);

        sb->s_magic = SYSV_MAGIC_BASE + sbi->s_type;
        /* set up enough so that it can read an inode */
        sb->s_op = &sysv_sops;
        if (sbi->s_forced_ro)
                sb->s_flags |= MS_RDONLY;
        if (sbi->s_truncate)
                sb->s_d_op = &sysv_dentry_operations;
        root_inode = sysv_iget(sb, SYSV_ROOT_INO);
        if (IS_ERR(root_inode)) {
                printk("SysV FS: get root inode failed\n");
                return 0;
        }
        sb->s_root = d_alloc_root(root_inode);
        if (!sb->s_root) {
                iput(root_inode);
                printk("SysV FS: get root dentry failed\n");
                return 0;
        }
        return 1;
}

static int sysv_fill_super(struct super_block *sb, void *data, int silent)
{
        struct buffer_head *bh1, *bh = NULL;
        struct sysv_sb_info *sbi;
        unsigned long blocknr;
        int size = 0, i;
        
        BUILD_BUG_ON(1024 != sizeof (struct xenix_super_block));
        BUILD_BUG_ON(512 != sizeof (struct sysv4_super_block));
        BUILD_BUG_ON(512 != sizeof (struct sysv2_super_block));
        BUILD_BUG_ON(500 != sizeof (struct coh_super_block));
        BUILD_BUG_ON(64 != sizeof (struct sysv_inode));

        sbi = kzalloc(sizeof(struct sysv_sb_info), GFP_KERNEL);
        if (!sbi)
                return -ENOMEM;

        sbi->s_sb = sb;
        sbi->s_block_base = 0;
        sb->s_fs_info = sbi;

        sb_set_blocksize(sb, BLOCK_SIZE);

        for (i = 0; i < ARRAY_SIZE(flavours) && !size; i++) {
                brelse(bh);
                bh = sb_bread(sb, flavours[i].block);
                if (!bh)
                        continue;
                size = flavours[i].test(SYSV_SB(sb), bh);
        }

        if (!size)
                goto Eunknown;

        switch (size) {
                case 1:
                        blocknr = bh->b_blocknr << 1;
                        brelse(bh);
                        sb_set_blocksize(sb, 512);
                        bh1 = sb_bread(sb, blocknr);
                        bh = sb_bread(sb, blocknr + 1);
                        break;
                case 2:
                        bh1 = bh;
                        break;
                case 3:
                        blocknr = bh->b_blocknr >> 1;
                        brelse(bh);
                        sb_set_blocksize(sb, 2048);
                        bh1 = bh = sb_bread(sb, blocknr);
                        break;
                default:
                        goto Ebadsize;
        }

        if (bh && bh1) {
                sbi->s_bh1 = bh1;
                sbi->s_bh2 = bh;
                if (complete_read_super(sb, silent, size))
                        return 0;
        }

        brelse(bh1);
        brelse(bh);
        sb_set_blocksize(sb, BLOCK_SIZE);
        printk("oldfs: cannot read superblock\n");
failed:
        kfree(sbi);
        return -EINVAL;

Eunknown:
        brelse(bh);
        if (!silent)
                printk("VFS: unable to find oldfs superblock on device %s\n",
                        sb->s_id);
        goto failed;
Ebadsize:
        brelse(bh);
        if (!silent)
                printk("VFS: oldfs: unsupported block size (%dKb)\n",
                        1<<(size-2));
        goto failed;
}

static int v7_sanity_check(struct super_block *sb, struct buffer_head *bh)
{
        struct v7_super_block *v7sb;
        struct sysv_inode *v7i;
        struct buffer_head *bh2;
        struct sysv_sb_info *sbi;

        sbi = sb->s_fs_info;

        /* plausibility check on superblock */
        v7sb = (struct v7_super_block *) bh->b_data;
        if (fs16_to_cpu(sbi, v7sb->s_nfree) > V7_NICFREE ||
            fs16_to_cpu(sbi, v7sb->s_ninode) > V7_NICINOD ||
            fs32_to_cpu(sbi, v7sb->s_fsize) > V7_MAXSIZE)
                return 0;

        /* plausibility check on root inode: it is a directory,
           with a nonzero size that is a multiple of 16 */
        bh2 = sb_bread(sb, 2);
        if (bh2 == NULL)
                return 0;

        v7i = (struct sysv_inode *)(bh2->b_data + 64);
        if ((fs16_to_cpu(sbi, v7i->i_mode) & ~0777) != S_IFDIR ||
            (fs32_to_cpu(sbi, v7i->i_size) == 0) ||
            (fs32_to_cpu(sbi, v7i->i_size) & 017) ||
            (fs32_to_cpu(sbi, v7i->i_size) > V7_NFILES *
             sizeof(struct sysv_dir_entry))) {
                brelse(bh2);
                return 0;
        }

        brelse(bh2);
        return 1;
}

static int v7_fill_super(struct super_block *sb, void *data, int silent)
{
        struct sysv_sb_info *sbi;
        struct buffer_head *bh;

        if (440 != sizeof (struct v7_super_block))
                panic("V7 FS: bad super-block size");
        if (64 != sizeof (struct sysv_inode))
                panic("sysv fs: bad i-node size");

        sbi = kzalloc(sizeof(struct sysv_sb_info), GFP_KERNEL);
        if (!sbi)
                return -ENOMEM;

        sbi->s_sb = sb;
        sbi->s_block_base = 0;
        sbi->s_type = FSTYPE_V7;
        sb->s_fs_info = sbi;
        
        sb_set_blocksize(sb, 512);

        if ((bh = sb_bread(sb, 1)) == NULL) {
                if (!silent)
                        printk("VFS: unable to read V7 FS superblock on "
                               "device %s.\n", sb->s_id);
                goto failed;
        }

        /* Try PDP-11 UNIX */
        sbi->s_bytesex = BYTESEX_PDP;
        if (v7_sanity_check(sb, bh))
                goto detected;

        /* Try PC/IX, v7/x86 */
        sbi->s_bytesex = BYTESEX_LE;
        if (v7_sanity_check(sb, bh))
                goto detected;

        goto failed;

detected:
        sbi->s_bh1 = bh;
        sbi->s_bh2 = bh;
        if (complete_read_super(sb, silent, 1))
                return 0;

failed:
        printk(KERN_ERR "VFS: could not find a valid V7 on %s.\n",
                sb->s_id);
        brelse(bh);
        kfree(sbi);
        return -EINVAL;
}

/* Every kernel module contains stuff like this. */

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

static struct dentry *v7_mount(struct file_system_type *fs_type,
        int flags, const char *dev_name, void *data)
{
        return mount_bdev(fs_type, flags, dev_name, data, v7_fill_super);
}

static struct file_system_type sysv_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "sysv",
        .mount          = sysv_mount,
        .kill_sb        = kill_block_super,
        .fs_flags       = FS_REQUIRES_DEV,
};

static struct file_system_type v7_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "v7",
        .mount          = v7_mount,
        .kill_sb        = kill_block_super,
        .fs_flags       = FS_REQUIRES_DEV,
};

static int __init init_sysv_fs(void)
{
        int error;

        error = sysv_init_icache();
        if (error)
                goto out;
        error = register_filesystem(&sysv_fs_type);
        if (error)
                goto destroy_icache;
        error = register_filesystem(&v7_fs_type);
        if (error)
                goto unregister;
        return 0;

unregister:
        unregister_filesystem(&sysv_fs_type);
destroy_icache:
        sysv_destroy_icache();
out:
        return error;
}

static void __exit exit_sysv_fs(void)
{
        unregister_filesystem(&sysv_fs_type);
        unregister_filesystem(&v7_fs_type);
        sysv_destroy_icache();
}

module_init(init_sysv_fs)
module_exit(exit_sysv_fs)
MODULE_ALIAS("v7");
MODULE_LICENSE("GPL");