super.c

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/*
 *  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, unsigned *max_links)
{
    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);
    }

    *max_links = 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, unsigned *max_links)
{
    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;

    *max_links = 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, unsigned *max_links)
{
    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;

    *max_links = 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, unsigned *max_links)
{
    struct coh_super_block * sbd;
    struct buffer_head *bh1 = sbi->s_bh1;

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

    *max_links = 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, unsigned *max_links)
{
    struct buffer_head *bh2 = sbi->s_bh2;
    struct v7_super_block *sbd = (struct v7_super_block *)bh2->b_data;

    *max_links = 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 *, unsigned *) = {
    [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, &sb->s_max_links);
    
    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_make_root(root_inode);
    if (!sb->s_root) {
        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;
    mutex_init(&sbi->s_lock);
    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");