namei.c

LINUX1.0内核源代码,学习LINUX编程的一定要看。

		    de->d_rec_len != 12 ) {
	        printk("XIA-FS: bad directory (%s %d)\n", WHERE_ERR);
		brelse(bh);
		return 1;	 
	    }
	    de=(struct xiafs_direct *)(12 + bh->b_data);
	    if (!de->d_ino || strcmp("..", de->d_name)) {
	    	printk("XIA-FS: bad directory (%s %d)\n", WHERE_ERR);
		brelse(bh);
		return 1;
	    }
	    offset=de->d_rec_len+12;
	}
	else
	    offset = 0;
	if (!bh)
	    continue;
	while (offset < XIAFS_ZSIZE(inode->i_sb)) {
	    de=(struct xiafs_direct *)(bh->b_data+offset);
	    if (de->d_ino > inode->i_sb->u.xiafs_sb.s_ninodes ||
		de->d_rec_len < 12 || 
		(char *)de+de->d_rec_len > bh->b_data+XIAFS_ZSIZE(inode->i_sb) ||
		de->d_name_len + 8 > de->d_rec_len ||
		de->d_name[de->d_name_len]) {
	        printk("XIA-FS: bad directory (%s %d)\n", WHERE_ERR);
		brelse(bh);
		return 1;
	    }
	    if (de->d_ino) {
	        brelse(bh);
		return 0;
	    }
	    offset+=de->d_rec_len;
	}
	brelse(bh);
    }
    return 1;
}

static void xiafs_rm_entry(struct xiafs_direct *de, struct xiafs_direct * de_pre)
{
    if (de==de_pre) {
        de->d_ino=0;
	return;
    }
    while (de_pre->d_rec_len+(u_char *)de_pre < (u_char *)de) {
        if (de_pre->d_rec_len < 12) {
	    printk("XIA-FS: bad directory entry (%s %d)\n", WHERE_ERR);
	    return;
	}
        de_pre=(struct xiafs_direct *)(de_pre->d_rec_len+(u_char *)de_pre);
    }
    if (de_pre->d_rec_len+(u_char *)de_pre > (u_char *)de) {
        printk("XIA-FS: bad directory entry (%s %d)\n", WHERE_ERR);
	return;
    }
    de_pre->d_rec_len+=de->d_rec_len;
}

int xiafs_rmdir(struct inode * dir, const char * name, int len)
{
    int retval;
    struct inode * inode;
    struct buffer_head * bh;
    struct xiafs_direct * de, * de_pre;

    inode = NULL;
    bh = xiafs_find_entry(dir, name, len, &de, &de_pre);
    retval = -ENOENT;
    if (!bh)
        goto end_rmdir;
    retval = -EPERM;
    if (!(inode = iget(dir->i_sb, de->d_ino)))
        goto end_rmdir;
    if ((dir->i_mode & S_ISVTX) && current->euid &&
	    inode->i_uid != current->euid)
        goto end_rmdir;
    if (inode->i_dev != dir->i_dev)
        goto end_rmdir;
    if (inode == dir)	/* we may not delete ".", but "../dir" is ok */
        goto end_rmdir;
    if (!S_ISDIR(inode->i_mode)) {
        retval = -ENOTDIR;
	goto end_rmdir;
    }
    if (!empty_dir(inode)) {
        retval = -ENOTEMPTY;
	goto end_rmdir;
    }
    if (inode->i_count > 1) {
        retval = -EBUSY;
	goto end_rmdir;
    }
    if (inode->i_nlink != 2)
        printk("XIA-FS: empty directory has nlink!=2 (%s %d)\n", WHERE_ERR);
    xiafs_rm_entry(de, de_pre);
    bh->b_dirt = 1;
    inode->i_nlink=0;
    inode->i_dirt=1;
    dir->i_nlink--;
    inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
    dir->i_dirt=1;
    retval = 0;
end_rmdir:
    iput(dir);
    iput(inode);
    brelse(bh);
    return retval;
}

int xiafs_unlink(struct inode * dir, const char * name, int len)
{
    int retval;
    struct inode * inode;
    struct buffer_head * bh;
    struct xiafs_direct * de, * de_pre;

repeat:
    retval = -ENOENT;
    inode = NULL;
    bh = xiafs_find_entry(dir, name, len, &de, &de_pre);
    if (!bh)
        goto end_unlink;
    if (!(inode = iget(dir->i_sb, de->d_ino)))
        goto end_unlink;
    retval = -EPERM;
    if (S_ISDIR(inode->i_mode))
        goto end_unlink;
    if (de->d_ino != inode->i_ino) {
        iput(inode);
	brelse(bh);
	current->counter = 0;
	schedule();
	goto repeat;
    }
    if ((dir->i_mode & S_ISVTX) && !suser() &&
	    current->euid != inode->i_uid &&
	    current->euid != dir->i_uid)
        goto end_unlink;
    if (!inode->i_nlink) {
        printk("XIA-FS: Deleting nonexistent file (%s %d)\n", WHERE_ERR);
	inode->i_nlink=1;
    }
    xiafs_rm_entry(de, de_pre);
    bh->b_dirt = 1;
    inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
    dir->i_dirt = 1;
    inode->i_nlink--;
    inode->i_dirt = 1;
    retval = 0;
end_unlink:
    brelse(bh);
    iput(inode);
    iput(dir);
    return retval;
}

int xiafs_symlink(struct inode * dir, const char * name, 
		int len, const char * symname)
{
    struct xiafs_direct * de;
    struct inode * inode = NULL;
    struct buffer_head * bh = NULL, * name_block = NULL;
    int i;
    char c;

    bh = xiafs_find_entry(dir,name,len, &de, NULL);
    if (bh) {
	brelse(bh);
	iput(dir);
	return -EEXIST;
    }
    if (!(inode = xiafs_new_inode(dir))) {
        iput(dir);
	return -ENOSPC;
    }
    inode->i_mode = S_IFLNK | S_IRWXUGO;
    inode->i_op = &xiafs_symlink_inode_operations;
    name_block = xiafs_bread(inode,0,1);
    if (!name_block) {
        iput(dir);
	inode->i_nlink--;
	inode->i_dirt = 1;
	iput(inode);
	return -ENOSPC;
    }
    for (i = 0; i < BLOCK_SIZE-1 && (c=*symname++); i++)
        name_block->b_data[i] = c;
    name_block->b_data[i] = 0;
    name_block->b_dirt = 1;
    brelse(name_block);
    inode->i_size = i;
    inode->i_dirt = 1;
    bh = xiafs_add_entry(dir, name, len, &de, NULL);
    if (!bh) {
        inode->i_nlink--;
	inode->i_dirt = 1;
	iput(inode);
	iput(dir);
	return -ENOSPC;
    }
    de->d_ino = inode->i_ino;
    bh->b_dirt = 1;
    brelse(bh);
    iput(dir);
    iput(inode);
    return 0;
}

int xiafs_link(struct inode * oldinode, struct inode * dir, 
	     const char * name, int len)
{
    struct xiafs_direct * de;
    struct buffer_head * bh;

    if (S_ISDIR(oldinode->i_mode)) {
        iput(oldinode);
	iput(dir);
	return -EPERM;
    }
    if (oldinode->i_nlink > 64000) {
        iput(oldinode);
	iput(dir);
	return -EMLINK;
    }
    bh = xiafs_find_entry(dir, name, len, &de, NULL);
    if (bh) {
        brelse(bh);
	iput(dir);
	iput(oldinode);
	return -EEXIST;
    }
    bh = xiafs_add_entry(dir, name, len, &de, NULL);
    if (!bh) {
        iput(dir);
	iput(oldinode);
	return -ENOSPC;
    }
    de->d_ino = oldinode->i_ino;
    bh->b_dirt = 1;
    brelse(bh);
    iput(dir);
    oldinode->i_nlink++;
    oldinode->i_ctime = CURRENT_TIME;
    oldinode->i_dirt = 1;
    iput(oldinode);
    return 0;
}

static int subdir(struct inode * new_inode, struct inode * old_inode)
{
    int ino;
    int result;

    new_inode->i_count++;
    result = 0;
    for (;;) {
        if (new_inode == old_inode) {
	    result = 1;
	    break;
	}
	if (new_inode->i_dev != old_inode->i_dev)
	    break;
	ino = new_inode->i_ino;
	if (xiafs_lookup(new_inode,"..",2,&new_inode))
	    break;
	if (new_inode->i_ino == ino)
	    break;
    }
    iput(new_inode);
    return result;
}

#define PARENT_INO(buffer) \
    (((struct xiafs_direct *) ((u_char *)(buffer) + 12))->d_ino)

/*
 * rename uses retry to avoid race-conditions: at least they should be minimal.
 * it tries to allocate all the blocks, then sanity-checks, and if the sanity-
 * checks fail, it tries to restart itself again. Very practical - no changes
 * are done until we know everything works ok.. and then all the changes can be
 * done in one fell swoop when we have claimed all the buffers needed.
 *
 * Anybody can rename anything with this: the permission checks are left to the
 * higher-level routines.
 */
static int do_xiafs_rename(struct inode * old_dir, const char * old_name, 
			 int old_len, struct inode * new_dir, 
			 const char * new_name, int new_len)
{
    struct inode * old_inode, * new_inode;
    struct buffer_head * old_bh, * new_bh, * dir_bh;
    struct xiafs_direct * old_de, * old_de_pre, * new_de, * new_de_pre;
    int retval;

try_again:
    old_inode = new_inode = NULL;
    old_bh = new_bh = dir_bh = NULL;
    old_bh = xiafs_find_entry(old_dir, old_name, old_len, &old_de, &old_de_pre);
    retval = -ENOENT;
    if (!old_bh)
        goto end_rename;
    old_inode = __iget(old_dir->i_sb, old_de->d_ino, 0); /* don't cross mnt-points */
    if (!old_inode)
        goto end_rename;
    retval = -EPERM;
    if ((old_dir->i_mode & S_ISVTX) && 
	    current->euid != old_inode->i_uid &&
	    current->euid != old_dir->i_uid && !suser())
        goto end_rename;
    new_bh = xiafs_find_entry(new_dir, new_name, new_len, &new_de, NULL);
    if (new_bh) {
        new_inode = __iget(new_dir->i_sb, new_de->d_ino, 0);
	if (!new_inode) {
	    brelse(new_bh);
	    new_bh = NULL;
	}
    }
    if (new_inode == old_inode) {
        retval = 0;
	goto end_rename;
    }
    if (new_inode && S_ISDIR(new_inode->i_mode)) {
        retval = -EEXIST;
	goto end_rename;
    }
    retval = -EPERM;
    if (new_inode && (new_dir->i_mode & S_ISVTX) && 
	    current->euid != new_inode->i_uid &&
 	    current->euid != new_dir->i_uid && !suser())
        goto end_rename;
    if (S_ISDIR(old_inode->i_mode)) {
        retval = -EEXIST;
	if (new_bh)
	    goto end_rename;
	retval = -EACCES;
	if (!permission(old_inode, MAY_WRITE))
	    goto end_rename;
	retval = -EINVAL;
	if (subdir(new_dir, old_inode))
	    goto end_rename;
	retval = -EIO;
	dir_bh = xiafs_bread(old_inode,0,0);
	if (!dir_bh)
	    goto end_rename;
	if (PARENT_INO(dir_bh->b_data) != old_dir->i_ino)
	    goto end_rename;
	retval = -EMLINK;
	if (new_dir->i_nlink > 64000)
	    goto end_rename;
    }
    if (!new_bh)
        new_bh = xiafs_add_entry(new_dir, new_name, new_len, &new_de, &new_de_pre);
    retval = -ENOSPC;
    if (!new_bh) 
        goto end_rename;
    /* sanity checking */
    if ( (new_inode && (new_de->d_ino != new_inode->i_ino))
	    || (new_de->d_ino && !new_inode)
	    || (old_de->d_ino != old_inode->i_ino)) {
        xiafs_rm_entry(new_de, new_de_pre);
        brelse(old_bh);
	brelse(new_bh);
	brelse(dir_bh);
	iput(old_inode);
	iput(new_inode);
	current->counter=0;
	schedule();
	goto try_again;
    }
    xiafs_rm_entry(old_de, old_de_pre);
    new_de->d_ino = old_inode->i_ino;
    if (new_inode) {
        new_inode->i_nlink--;
	new_inode->i_dirt = 1;
    }
    old_bh->b_dirt = 1;
    new_bh->b_dirt = 1;
    if (dir_bh) {
        PARENT_INO(dir_bh->b_data) = new_dir->i_ino;
	dir_bh->b_dirt = 1;
	old_dir->i_nlink--;
	new_dir->i_nlink++;
	old_dir->i_dirt = 1;
	new_dir->i_dirt = 1;
    }
    retval = 0;
end_rename:
    brelse(dir_bh);
    brelse(old_bh);
    brelse(new_bh);
    iput(old_inode);
    iput(new_inode);
    iput(old_dir);
    iput(new_dir);
    return retval;
}

/*
 * Ok, rename also locks out other renames, as they can change the parent of
 * a directory, and we don't want any races. Other races are checked for by
 * "do_rename()", which restarts if there are inconsistencies.
 *
 * Note that there is no race between different filesystems: it's only within
 * the same device that races occur: many renames can happen at once, as long
 * as they are on different partitions.
 */
int xiafs_rename(struct inode * old_dir, const char * old_name, int old_len,
	struct inode * new_dir, const char * new_name, int new_len)
{
    static struct wait_queue * wait = NULL;
    static int lock = 0;
    int result;

    while (lock)
        sleep_on(&wait);
    lock = 1;
    result = do_xiafs_rename(old_dir, old_name, old_len,
			   new_dir, new_name, new_len);
    lock = 0;
    wake_up(&wait);
    return result;
}