namei.c

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/*
 *  linux/fs/sysv/namei.c
 *
 *  minix/namei.c
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  coh/namei.c
 *  Copyright (C) 1993  Pascal Haible, Bruno Haible
 *
 *  sysv/namei.c
 *  Copyright (C) 1993  Bruno Haible
 *  Copyright (C) 1997, 1998  Krzysztof G. Baranowski
 */


#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/sysv_fs.h>
#include <linux/string.h>
#include <linux/stat.h>
#include <linux/errno.h>

/* compare strings: name[0..len-1] (not zero-terminated) and
 * buffer[0..] (filled with zeroes up to buffer[0..maxlen-1])
 */
static inline int namecompare(int len, int maxlen,
	const char * name, const char * buffer)
{
	if (len > maxlen)
		return 0;
	if (len < maxlen && buffer[len])
		return 0;
	return !memcmp(name, buffer, len);
}

/*
 * ok, we cannot use strncmp, as the name is not in our data space. [Now it is!]
 * Thus we'll have to use sysv_match. No big problem. Match also makes
 * some sanity tests.
 *
 * NOTE! unlike strncmp, sysv_match returns 1 for success, 0 for failure.
 */
static int sysv_match(int len, const char * name, struct sysv_dir_entry * de)
{
	if (!de->inode || len > SYSV_NAMELEN)
		return 0;
	/* "" means "." ---> so paths like "/usr/lib//libc.a" work */
	if (!len && (de->name[0]=='.') && (de->name[1]=='\0'))
		return 1;
	return namecompare(len, SYSV_NAMELEN, name, de->name);
}

/*
 *	sysv_find_entry()
 *
 * finds an entry in the specified directory with the wanted name. It
 * returns the cache buffer in which the entry was found, and the entry
 * itself (as a parameter - res_dir). It does NOT read the inode of the
 * entry - you'll have to do that yourself if you want to.
 */
static struct buffer_head * sysv_find_entry(struct inode * dir,
	const char * name, int namelen, struct sysv_dir_entry ** res_dir)
{
	struct super_block * sb;
	unsigned long pos, block, offset; /* pos = block * block_size + offset */
	struct buffer_head * bh;

	*res_dir = NULL;
	sb = dir->i_sb;
	if (namelen > SYSV_NAMELEN) {
		if (sb->sv_truncate)
			namelen = SYSV_NAMELEN;
		else
			return NULL;
	}
	bh = NULL;
	pos = block = offset = 0;
	while (pos < dir->i_size) {
		if (!bh) {
			bh = sysv_file_bread(dir, block, 0);
			if (!bh) {
				/* offset = 0; */ block++;
				pos += sb->sv_block_size;
				continue;
			}
		}
		if (sysv_match(namelen, name,
			       *res_dir = (struct sysv_dir_entry *) (bh->b_data + offset) ))
			return bh;
		pos += SYSV_DIRSIZE;
		offset += SYSV_DIRSIZE;
		if (offset < sb->sv_block_size)
			continue;
		brelse(bh);
		bh = NULL;
		offset = 0; block++;
	}
	brelse(bh);
	*res_dir = NULL;
	return NULL;
}

struct dentry *sysv_lookup(struct inode * dir, struct dentry * dentry)
{
	struct inode * inode = NULL;
	struct sysv_dir_entry * de;
	struct buffer_head * bh;

	bh = sysv_find_entry(dir, dentry->d_name.name, dentry->d_name.len, &de);

	if (bh) {
		int ino = de->inode;
		brelse(bh);
		inode = iget(dir->i_sb, ino);
	
		if (!inode) 
			return ERR_PTR(-EACCES);
	}
	d_add(dentry, inode);
	return NULL;
}

/*
 *	sysv_add_entry()
 *
 * adds a file entry to the specified directory, returning a possible
 * error value if it fails.
 *
 * NOTE!! The inode part of 'de' is left at 0 - which means you
 * may not sleep between calling this and putting something into
 * the entry, as someone else might have used it while you slept.
 */
static int sysv_add_entry(struct inode * dir,
	const char * name, int namelen,
	struct buffer_head ** res_buf,
	struct sysv_dir_entry ** res_dir)
{
	struct super_block * sb;
	int i;
	unsigned long pos, block, offset; /* pos = block * block_size + offset */
	struct buffer_head * bh;
	struct sysv_dir_entry * de;

	*res_buf = NULL;
	*res_dir = NULL;
	sb = dir->i_sb;
	if (namelen > SYSV_NAMELEN) {
		if (sb->sv_truncate)
			namelen = SYSV_NAMELEN;
		else
			return -ENAMETOOLONG;
	}
	if (!namelen)
		return -ENOENT;
	bh = NULL;
	pos = block = offset = 0;
	while (1) {
		if (!bh) {
			bh = sysv_file_bread(dir, block, 1);
			if (!bh)
				return -ENOSPC;
		}
		de = (struct sysv_dir_entry *) (bh->b_data + offset);
		pos += SYSV_DIRSIZE;
		offset += SYSV_DIRSIZE;
		if (pos > dir->i_size) {
			de->inode = 0;
			dir->i_size = pos;
			mark_inode_dirty(dir);
		}
		if (de->inode) {
			if (namecompare(namelen, SYSV_NAMELEN, name, de->name)) {
				brelse(bh);
				return -EEXIST;
			}
		} else {
			dir->i_mtime = dir->i_ctime = CURRENT_TIME;
			mark_inode_dirty(dir);
			for (i = 0; i < SYSV_NAMELEN ; i++)
				de->name[i] = (i < namelen) ? name[i] : 0;
			mark_buffer_dirty(bh, 1);
			*res_dir = de;
			break;
		}
		if (offset < sb->sv_block_size)
			continue;
		brelse(bh);
		bh = NULL;
		offset = 0; block++;
	}
	*res_buf = bh;
	return 0;
}

int sysv_create(struct inode * dir, struct dentry * dentry, int mode)
{
	int error;
	struct inode * inode;
	struct buffer_head * bh;
	struct sysv_dir_entry * de;

	inode = sysv_new_inode(dir);
	if (!inode) 
		return -ENOSPC;
	inode->i_op = &sysv_file_inode_operations;
	inode->i_mode = mode;
	mark_inode_dirty(inode);
	error = sysv_add_entry(dir, dentry->d_name.name,
			       dentry->d_name.len, &bh, &de);
	if (error) {
		inode->i_nlink--;
		mark_inode_dirty(inode);
		iput(inode);
		return error;
	}
	de->inode = inode->i_ino;
	mark_buffer_dirty(bh, 1);
	brelse(bh);
	d_instantiate(dentry, inode);
	return 0;
}

int sysv_mknod(struct inode * dir, struct dentry * dentry, int mode, int rdev)
{
	int error;
	struct inode * inode;
	struct buffer_head * bh;
	struct sysv_dir_entry * de;

	bh = sysv_find_entry(dir, dentry->d_name.name,
			     dentry->d_name.len, &de);
	if (bh) {
		brelse(bh);
		return -EEXIST;
	}
	inode = sysv_new_inode(dir);
	if (!inode)
		return -ENOSPC;
	inode->i_uid = current->fsuid;
	inode->i_mode = mode;
	inode->i_op = NULL;
	if (S_ISREG(inode->i_mode))
		inode->i_op = &sysv_file_inode_operations;
	else if (S_ISCHR(inode->i_mode))
		inode->i_op = &chrdev_inode_operations;
	else if (S_ISBLK(inode->i_mode))
		inode->i_op = &blkdev_inode_operations;
	else if (S_ISFIFO(inode->i_mode))
		init_fifo(inode);
	if (S_ISBLK(mode) || S_ISCHR(mode))
		inode->i_rdev = to_kdev_t(rdev);
	mark_inode_dirty(inode);
	error = sysv_add_entry(dir, dentry->d_name.name, 
			       dentry->d_name.len, &bh, &de);
	if (error) {
		inode->i_nlink--;
		mark_inode_dirty(inode);
		iput(inode);
		return error;
	}
	de->inode = inode->i_ino;
	mark_buffer_dirty(bh, 1);
	brelse(bh);
	d_instantiate(dentry, inode);
	return 0;
}

int sysv_mkdir(struct inode * dir, struct dentry *dentry, int mode)
{
	int error;
	struct inode * inode;
	struct buffer_head * bh, *dir_block;
	struct sysv_dir_entry * de;

	bh = sysv_find_entry(dir, dentry->d_name.name,
                              dentry->d_name.len, &de);
	if (bh) {
		brelse(bh);
		return -EEXIST;
	}
	if (dir->i_nlink >= dir->i_sb->sv_link_max) 
		return -EMLINK;
	inode = sysv_new_inode(dir);
	if (!inode)
		return -ENOSPC;
	inode->i_op = &sysv_dir_inode_operations;
	inode->i_size = 2 * SYSV_DIRSIZE;
	dir_block = sysv_file_bread(inode,0,1);
	if (!dir_block) {
		inode->i_nlink--;
		mark_inode_dirty(inode);
		iput(inode);
		return -ENOSPC;
	}
	de = (struct sysv_dir_entry *) (dir_block->b_data + 0*SYSV_DIRSIZE);
	de->inode = inode->i_ino;
	strcpy(de->name,"."); /* rest of de->name is zero, see sysv_new_block */
	de = (struct sysv_dir_entry *) (dir_block->b_data + 1*SYSV_DIRSIZE);
	de->inode = dir->i_ino;
	strcpy(de->name,".."); /* rest of de->name is zero, see sysv_new_block */
	inode->i_nlink = 2;
	mark_buffer_dirty(dir_block, 1);
	brelse(dir_block);
	inode->i_mode = S_IFDIR | (mode & 0777 & ~current->fs->umask);
	if (dir->i_mode & S_ISGID)
		inode->i_mode |= S_ISGID;
	mark_inode_dirty(inode);
	error = sysv_add_entry(dir, dentry->d_name.name,
                               dentry->d_name.len, &bh, &de);
 	if (error) {
		inode->i_nlink=0;
		iput(inode);
		return error;
	}
	de->inode = inode->i_ino;
	mark_buffer_dirty(bh, 1);