inode.c

linux平台下的systv文件系统源代码

/*
 *  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 allocating/freeing inodes and for read/writing
 *  the superblock.
 */

#include <linux/config.h>
#include <linux/module.h>

#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/sysv_fs.h>
#include <linux/stat.h>
#include <linux/string.h>
#include <linux/locks.h>
#include <linux/init.h>
#include <linux/smp_lock.h>
#include <linux/highuid.h>
#include <asm/byteorder.h>
#include <asm/uaccess.h>

#if 0
void sysv_print_inode(struct inode * inode)
{
        printk("ino %lu  mode 0%6.6o  lk %d  uid %d  gid %d"
               "  sz %lu  blks %lu  cnt %u\n",
               inode->i_ino, inode->i_mode, inode->i_nlink, inode->i_uid,
               inode->i_gid, inode->i_size, inode->i_blocks,
               atomic_read(&inode->i_count));
        printk("  db <0x%lx 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx"
               " 0x%lx 0x%lx>\n",
                inode->u.sysv_i.i_data[0], inode->u.sysv_i.i_data[1],
                inode->u.sysv_i.i_data[2], inode->u.sysv_i.i_data[3],
                inode->u.sysv_i.i_data[4], inode->u.sysv_i.i_data[5],
                inode->u.sysv_i.i_data[6], inode->u.sysv_i.i_data[7],
                inode->u.sysv_i.i_data[8], inode->u.sysv_i.i_data[9]);
        printk("  ib <0x%lx 0x%lx 0x%lx>\n",
                inode->u.sysv_i.i_data[10],
                inode->u.sysv_i.i_data[11],
                inode->u.sysv_i.i_data[12]);
}
#endif

static void sysv_delete_inode(struct inode *inode)
{
	lock_kernel();
	inode->i_size = 0;
	sysv_truncate(inode);
	sysv_free_inode(inode);
	unlock_kernel();
}

static void sysv_put_super(struct super_block *);
static void sysv_write_super(struct super_block *);
static void sysv_read_inode(struct inode *);
static int sysv_statfs(struct super_block *, struct statfs *);

static struct super_operations sysv_sops = {
	read_inode:	sysv_read_inode,
	write_inode:	sysv_write_inode,
	delete_inode:	sysv_delete_inode,
	put_super:	sysv_put_super,
	write_super:	sysv_write_super,
	statfs:		sysv_statfs,
};

/* 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.
 * We discriminate among SystemV4 and SystemV2 FS by the assumption that
 * the time stamp is not < 01-01-1980.
 */

static void detected_bs (u_char type, struct super_block *sb)
{
	u_char n_bits = type+8;
	int bsize = 1 << n_bits;
	int bsize_4 = bsize >> 2;
	
	sb->sv_block_size = bsize;
	sb->sv_block_size_1 = bsize-1;
	sb->sv_block_size_bits = n_bits;
	sb->sv_block_size_dec_bits = (bsize==512) ? 1 : 0;
	sb->sv_block_size_inc_bits = (bsize==2048) ? 1 : 0;
	sb->sv_inodes_per_block = bsize >> 6;
	sb->sv_inodes_per_block_1 = (bsize >> 6)-1;
	sb->sv_inodes_per_block_bits = n_bits-6;
	sb->sv_toobig_block = 10 +
	  (sb->sv_ind_per_block = bsize_4) +
	  (sb->sv_ind_per_block_2 = bsize_4*bsize_4) +
	  (sb->sv_ind_per_block_3 = bsize_4*bsize_4*bsize_4);
	sb->sv_ind_per_block_1 = bsize_4-1;
	sb->sv_ind_per_block_2_1 = bsize_4*bsize_4-1;
	sb->sv_ind_per_block_2_bits = 2 *
	  (sb->sv_ind_per_block_bits = n_bits-2);
	sb->sv_ind_per_block_block_size_1 = bsize_4*bsize-1;
	sb->sv_ind_per_block_block_size_bits = 2*n_bits-2;
	sb->sv_ind_per_block_2_block_size_1 = bsize_4*bsize_4*bsize-1;
	sb->sv_ind_per_block_2_block_size_bits = 3*n_bits-4;
	sb->sv_ind0_size = 10 * bsize;
	sb->sv_ind1_size = (10 + bsize_4)* bsize;
	sb->sv_ind2_size = (10 + bsize_4 + bsize_4*bsize_4) * bsize;
}

static const char* detect_xenix (struct super_block *sb, struct buffer_head *bh)
{
	struct xenix_super_block * sbd;

	sbd = (struct xenix_super_block *) bh->b_data;
	if (sbd->s_magic != 0x2b5544)
		return NULL;
	if (sbd->s_type > 2 || sbd->s_type < 1)
		return NULL;
	detected_bs(sbd->s_type, sb);
	sb->sv_type = FSTYPE_XENIX;
	return "Xenix";
}
static struct super_block * detected_xenix (struct super_block *sb, struct buffer_head *bh1, struct buffer_head *bh2)
{
	struct xenix_super_block * sbd1;
	struct xenix_super_block * sbd2;

	if (sb->sv_block_size >= BLOCK_SIZE)
		/* block size >= 1024, so 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 - BLOCK_SIZE/2);
		/* sanity check */
		if (sbd2->s_magic != 0x2b5544)
			return NULL;
	}

	sb->sv_convert = 0;
	sb->sv_kludge_symlinks = 1;
	sb->sv_truncate = 1;
	sb->sv_link_max = XENIX_LINK_MAX;
	sb->sv_fic_size = XENIX_NICINOD;
	sb->sv_flc_size = XENIX_NICFREE;
	sb->sv_bh1 = bh1;
	sb->sv_bh2 = bh2;
	sb->sv_sbd1 = (char *) sbd1;
	sb->sv_sbd2 = (char *) sbd2;
	sb->sv_sb_fic_count = &sbd1->s_ninode;
	sb->sv_sb_fic_inodes = &sbd1->s_inode[0];
	sb->sv_sb_total_free_inodes = &sbd2->s_tinode;
	sb->sv_sb_flc_count = &sbd1->s_nfree;
	sb->sv_sb_flc_blocks = &sbd1->s_free[0];
	sb->sv_sb_total_free_blocks = &sbd2->s_tfree;
	sb->sv_sb_time = &sbd2->s_time;
	sb->sv_firstinodezone = 2;
	sb->sv_firstdatazone = sbd1->s_isize;
	sb->sv_nzones = sbd1->s_fsize;
	sb->sv_ndatazones = sb->sv_nzones - sb->sv_firstdatazone;
	return sb;
}

static const char* detect_sysv4 (struct super_block *sb, struct buffer_head *bh)
{
	struct sysv4_super_block * sbd;

	sbd = (struct sysv4_super_block *) (bh->b_data + BLOCK_SIZE/2);
	if (sbd->s_magic != 0xfd187e20)
		return NULL;
	if (sbd->s_time < 315532800) /* this is likely to happen on SystemV2 FS */
		return NULL;
	if ((sbd->s_type > 3 || sbd->s_type < 1) && (sbd->s_type > 0x30 || sbd->s_type < 0x10))
		return NULL;

	/* 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 (sbd->s_type >= 0x10) {
		printk("SysV FS: can't handle long file names on %s, "
		       "forcing read-only mode.\n", kdevname(sb->s_dev));
		sb->s_flags |= MS_RDONLY;
	}

	detected_bs(sbd->s_type >= 0x10 ? (sbd->s_type >> 4) : sbd->s_type, sb);
	sb->sv_type = FSTYPE_SYSV4;
	return "SystemV";
}

static struct super_block * detected_sysv4 (struct super_block *sb, struct buffer_head *bh)
{
	struct sysv4_super_block * sbd;

	if (sb->sv_block_size >= BLOCK_SIZE)
		sbd = (struct sysv4_super_block *) (bh->b_data + BLOCK_SIZE/2);
	else {
		sbd = (struct sysv4_super_block *) bh->b_data;
		/* sanity check */
		if (sbd->s_magic != 0xfd187e20)
			return NULL;
		if (sbd->s_time < 315532800)
			return NULL;
	}

	sb->sv_convert = 0;
	sb->sv_kludge_symlinks = 0; /* ?? */
	sb->sv_truncate = 1;
	sb->sv_link_max = SYSV_LINK_MAX;
	sb->sv_fic_size = SYSV_NICINOD;
	sb->sv_flc_size = SYSV_NICFREE;
	sb->sv_bh1 = bh;
	sb->sv_bh2 = bh;
	sb->sv_sbd1 = (char *) sbd;
	sb->sv_sbd2 = (char *) sbd;
	sb->sv_sb_fic_count = &sbd->s_ninode;
	sb->sv_sb_fic_inodes = &sbd->s_inode[0];
	sb->sv_sb_total_free_inodes = &sbd->s_tinode;
	sb->sv_sb_flc_count = &sbd->s_nfree;
	sb->sv_sb_flc_blocks = &sbd->s_free[0];
	sb->sv_sb_total_free_blocks = &sbd->s_tfree;
	sb->sv_sb_time = &sbd->s_time;
	sb->sv_sb_state = &sbd->s_state;
	sb->sv_firstinodezone = 2;
	sb->sv_firstdatazone = sbd->s_isize;
	sb->sv_nzones = sbd->s_fsize;
	sb->sv_ndatazones = sb->sv_nzones - sb->sv_firstdatazone;
	return sb;
}

static const char* detect_sysv2 (struct super_block *sb, struct buffer_head *bh)
{
	struct sysv2_super_block * sbd;

	sbd = (struct sysv2_super_block *) (bh->b_data + BLOCK_SIZE/2);
	if (sbd->s_magic != 0xfd187e20)
		return NULL;
	if (sbd->s_time < 315532800) /* this is likely to happen on SystemV4 FS */
		return NULL;
	if (sbd->s_type > 3 || sbd->s_type < 1)
		return NULL;
	detected_bs(sbd->s_type, sb);
	sb->sv_type = FSTYPE_SYSV2;
	return "SystemV Release 2";
}
static struct super_block * detected_sysv2 (struct super_block *sb, struct buffer_head *bh)
{
	struct sysv2_super_block * sbd;

	if (sb->sv_block_size >= BLOCK_SIZE)
		sbd = (struct sysv2_super_block *) (bh->b_data + BLOCK_SIZE/2);
	else {
		sbd = (struct sysv2_super_block *) bh->b_data;
		/* sanity check */
		if (sbd->s_magic != 0xfd187e20)
			return NULL;
		if (sbd->s_time < 315532800)
			return NULL;
	}

	sb->sv_convert = 0;
	sb->sv_kludge_symlinks = 0; /* ?? */
	sb->sv_truncate = 1;
	sb->sv_link_max = SYSV_LINK_MAX;
	sb->sv_fic_size = SYSV_NICINOD;
	sb->sv_flc_size = SYSV_NICFREE;
	sb->sv_bh1 = bh;
	sb->sv_bh2 = bh;
	sb->sv_sbd1 = (char *) sbd;
	sb->sv_sbd2 = (char *) sbd;
	sb->sv_sb_fic_count = &sbd->s_ninode;
	sb->sv_sb_fic_inodes = &sbd->s_inode[0];
	sb->sv_sb_total_free_inodes = &sbd->s_tinode;
	sb->sv_sb_flc_count = &sbd->s_nfree;
	sb->sv_sb_flc_blocks = &sbd->s_free[0];
	sb->sv_sb_total_free_blocks = &sbd->s_tfree;
	sb->sv_sb_time = &sbd->s_time;
	sb->sv_sb_state = &sbd->s_state;
	sb->sv_firstinodezone = 2;
	sb->sv_firstdatazone = sbd->s_isize;
	sb->sv_nzones = sbd->s_fsize;
	sb->sv_ndatazones = sb->sv_nzones - sb->sv_firstdatazone;
	return sb;
}

static const char* detect_coherent (struct super_block *sb, 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 NULL;
	detected_bs(1, sb);
	sb->sv_type = FSTYPE_COH;
	return "Coherent";
}
static struct super_block * detected_coherent (struct super_block *sb, struct buffer_head *bh)
{
	struct coh_super_block * sbd;

	sbd = (struct coh_super_block *) bh->b_data;
	/* sanity check */
	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 NULL;

	sb->sv_convert = 1;
	sb->sv_kludge_symlinks = 1;
	sb->sv_truncate = 1;
	sb->sv_link_max = COH_LINK_MAX;
	sb->sv_fic_size = COH_NICINOD;
	sb->sv_flc_size = COH_NICFREE;
	sb->sv_bh1 = bh;
	sb->sv_bh2 = bh;
	sb->sv_sbd1 = (char *) sbd;
	sb->sv_sbd2 = (char *) sbd;
	sb->sv_sb_fic_count = &sbd->s_ninode;
	sb->sv_sb_fic_inodes = &sbd->s_inode[0];
	sb->sv_sb_total_free_inodes = &sbd->s_tinode;
	sb->sv_sb_flc_count = &sbd->s_nfree;
	sb->sv_sb_flc_blocks = &sbd->s_free[0];
	sb->sv_sb_total_free_blocks = &sbd->s_tfree;
	sb->sv_sb_time = &sbd->s_time;
	sb->sv_firstinodezone = 2;
	sb->sv_firstdatazone = sbd->s_isize;
	sb->sv_nzones = from_coh_ulong(sbd->s_fsize);
	sb->sv_ndatazones = sb->sv_nzones - sb->sv_firstdatazone;
	return sb;
}

static struct super_block *sysv_read_super(struct super_block *sb,
					   void *data, int silent)
{
	struct buffer_head *bh;
	const char *found;
	kdev_t dev = sb->s_dev;
	struct inode *root_inode;
	unsigned long blocknr;
	
	if (1024 != sizeof (struct xenix_super_block))
		panic("Xenix FS: bad super-block size");
	if ((512 != sizeof (struct sysv4_super_block))
            || (512 != sizeof (struct sysv2_super_block)))
		panic("SystemV FS: bad super-block size");
	if (500 != sizeof (struct coh_super_block))
		panic("Coherent FS: bad super-block size");
	if (64 != sizeof (struct sysv_inode))
		panic("sysv fs: bad i-node size");
	set_blocksize(dev,BLOCK_SIZE);
	sb->sv_block_base = 0;

	/* Try to read Xenix superblock */
	if ((bh = bread(dev, 1, BLOCK_SIZE)) != NULL) {
		if ((found = detect_xenix(sb,bh)) != NULL)
			goto ok;
		brelse(bh);
	}
	if ((bh = bread(dev, 0, BLOCK_SIZE)) != NULL) {
		/* Try to recognize SystemV superblock */
		if ((found = detect_sysv4(sb,bh)) != NULL)
			goto ok;
		if ((found = detect_sysv2(sb,bh)) != NULL)
			goto ok;
		/* Try to recognize Coherent superblock */
		if ((found = detect_coherent(sb,bh)) != NULL)
			goto ok;
		brelse(bh);
	}
	/* Try to recognize SystemV superblock */
	/* Offset by 1 track, i.e. most probably 9, 15, or 18 kilobytes. */
	/* 2kB blocks with offset of 9 and 15 kilobytes are not supported. */
	/* Maybe we should also check the device geometry ? */
	{	static int offsets[] = { 9, 15, 18, };
		int i;
		for (i = 0; i < sizeof(offsets)/sizeof(offsets[0]); i++)
			if ((bh = bread(dev, offsets[i], BLOCK_SIZE)) != NULL) {
				/* Try to recognize SystemV superblock */
				if ((found = detect_sysv4(sb,bh)) != NULL) {