namei.c

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		up(&dir->d_inode->i_sem);
		goto exit;
	}

	/* Negative dentry, just create the file */
	if (!dentry->d_inode) {
		error = vfs_create(dir->d_inode, dentry,
				   mode & ~current->fs->umask);
		up(&dir->d_inode->i_sem);
		dput(nd->dentry);
		nd->dentry = dentry;
		if (error)
			goto exit;
		/* Don't check for write permission, don't truncate */
		acc_mode = 0;
		flag &= ~O_TRUNC;
		goto ok;
	}

	/*
	 * It already exists.
	 */
	up(&dir->d_inode->i_sem);

	error = -EEXIST;
	if (flag & O_EXCL)
		goto exit_dput;

	if (d_mountpoint(dentry)) {
		error = -ELOOP;
		if (flag & O_NOFOLLOW)
			goto exit_dput;
		while (__follow_down(&nd->mnt,&dentry) && d_mountpoint(dentry));
	}
	error = -ENOENT;
	if (!dentry->d_inode)
		goto exit_dput;
	if (dentry->d_inode->i_op && dentry->d_inode->i_op->follow_link)
		goto do_link;

	dput(nd->dentry);
	nd->dentry = dentry;
	error = -EISDIR;
	if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode))
		goto exit;
ok:
	error = -ENOENT;
	inode = dentry->d_inode;
	if (!inode)
		goto exit;

	error = -ELOOP;
	if (S_ISLNK(inode->i_mode))
		goto exit;
	
	error = -EISDIR;
	if (S_ISDIR(inode->i_mode) && (flag & FMODE_WRITE))
		goto exit;

	error = permission(inode,acc_mode);
	if (error)
		goto exit;

	/*
	 * FIFO's, sockets and device files are special: they don't
	 * actually live on the filesystem itself, and as such you
	 * can write to them even if the filesystem is read-only.
	 */
	if (S_ISFIFO(inode->i_mode) || S_ISSOCK(inode->i_mode)) {
	    	flag &= ~O_TRUNC;
	} else if (S_ISBLK(inode->i_mode) || S_ISCHR(inode->i_mode)) {
		error = -EACCES;
		if (nd->mnt->mnt_flags & MNT_NODEV)
			goto exit;

		flag &= ~O_TRUNC;
	} else {
		error = -EROFS;
		if (IS_RDONLY(inode) && (flag & 2))
			goto exit;
	}
	/*
	 * An append-only file must be opened in append mode for writing.
	 */
	error = -EPERM;
	if (IS_APPEND(inode)) {
		if  ((flag & FMODE_WRITE) && !(flag & O_APPEND))
			goto exit;
		if (flag & O_TRUNC)
			goto exit;
	}

	/*
	 * Ensure there are no outstanding leases on the file.
	 */
	error = get_lease(inode, flag);
	if (error)
		goto exit;

	if (flag & O_TRUNC) {
		error = get_write_access(inode);
		if (error)
			goto exit;

		/*
		 * Refuse to truncate files with mandatory locks held on them.
		 */
		error = locks_verify_locked(inode);
		if (!error) {
			DQUOT_INIT(inode);
			
			error = do_truncate(dentry, 0);
		}
		put_write_access(inode);
		if (error)
			goto exit;
	} else
		if (flag & FMODE_WRITE)
			DQUOT_INIT(inode);

	return 0;

exit_dput:
	dput(dentry);
exit:
	path_release(nd);
	return error;

do_link:
	error = -ELOOP;
	if (flag & O_NOFOLLOW)
		goto exit_dput;
	/*
	 * This is subtle. Instead of calling do_follow_link() we do the
	 * thing by hands. The reason is that this way we have zero link_count
	 * and path_walk() (called from ->follow_link) honoring LOOKUP_PARENT.
	 * After that we have the parent and last component, i.e.
	 * we are in the same situation as after the first path_walk().
	 * Well, almost - if the last component is normal we get its copy
	 * stored in nd->last.name and we will have to putname() it when we
	 * are done. Procfs-like symlinks just set LAST_BIND.
	 */
	UPDATE_ATIME(dentry->d_inode);
	error = dentry->d_inode->i_op->follow_link(dentry, nd);
	dput(dentry);
	if (error)
		return error;
	if (nd->last_type == LAST_BIND) {
		dentry = nd->dentry;
		goto ok;
	}
	error = -EISDIR;
	if (nd->last_type != LAST_NORM)
		goto exit;
	if (nd->last.name[nd->last.len]) {
		putname(nd->last.name);
		goto exit;
	}
	error = -ELOOP;
	if (count++==32) {
		putname(nd->last.name);
		goto exit;
	}
	dir = nd->dentry;
	down(&dir->d_inode->i_sem);
	dentry = lookup_hash(&nd->last, nd->dentry);
	putname(nd->last.name);
	goto do_last;
}

/* SMP-safe */
static struct dentry *lookup_create(struct nameidata *nd, int is_dir)
{
	struct dentry *dentry;

	down(&nd->dentry->d_inode->i_sem);
	dentry = ERR_PTR(-EEXIST);
	if (nd->last_type != LAST_NORM)
		goto fail;
	dentry = lookup_hash(&nd->last, nd->dentry);
	if (IS_ERR(dentry))
		goto fail;
	if (!is_dir && nd->last.name[nd->last.len] && !dentry->d_inode)
		goto enoent;
	return dentry;
enoent:
	dput(dentry);
	dentry = ERR_PTR(-ENOENT);
fail:
	return dentry;
}

int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
{
	int error = -EPERM;

	down(&dir->i_zombie);
	if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
		goto exit_lock;

	error = may_create(dir, dentry);
	if (error)
		goto exit_lock;

	error = -EPERM;
	if (!dir->i_op || !dir->i_op->mknod)
		goto exit_lock;

	DQUOT_INIT(dir);
	lock_kernel();
	error = dir->i_op->mknod(dir, dentry, mode, dev);
	unlock_kernel();
exit_lock:
	up(&dir->i_zombie);
	if (!error)
		inode_dir_notify(dir, DN_CREATE);
	return error;
}

asmlinkage long sys_mknod(const char * filename, int mode, dev_t dev)
{
	int error = 0;
	char * tmp;
	struct dentry * dentry;
	struct nameidata nd;

	if (S_ISDIR(mode))
		return -EPERM;
	tmp = getname(filename);
	if (IS_ERR(tmp))
		return PTR_ERR(tmp);

	if (path_init(tmp, LOOKUP_PARENT, &nd))
		error = path_walk(tmp, &nd);
	if (error)
		goto out;
	dentry = lookup_create(&nd, 0);
	error = PTR_ERR(dentry);

	mode &= ~current->fs->umask;
	if (!IS_ERR(dentry)) {
		switch (mode & S_IFMT) {
		case 0: case S_IFREG:
			error = vfs_create(nd.dentry->d_inode,dentry,mode);
			break;
		case S_IFCHR: case S_IFBLK: case S_IFIFO: case S_IFSOCK:
			error = vfs_mknod(nd.dentry->d_inode,dentry,mode,dev);
			break;
		case S_IFDIR:
			error = -EPERM;
			break;
		default:
			error = -EINVAL;
		}
		dput(dentry);
	}
	up(&nd.dentry->d_inode->i_sem);
	path_release(&nd);
out:
	putname(tmp);

	return error;
}

int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
	int error;

	down(&dir->i_zombie);
	error = may_create(dir, dentry);
	if (error)
		goto exit_lock;

	error = -EPERM;
	if (!dir->i_op || !dir->i_op->mkdir)
		goto exit_lock;

	DQUOT_INIT(dir);
	mode &= (S_IRWXUGO|S_ISVTX);
	lock_kernel();
	error = dir->i_op->mkdir(dir, dentry, mode);
	unlock_kernel();

exit_lock:
	up(&dir->i_zombie);
	if (!error)
		inode_dir_notify(dir, DN_CREATE);
	return error;
}

asmlinkage long sys_mkdir(const char * pathname, int mode)
{
	int error = 0;
	char * tmp;

	tmp = getname(pathname);
	error = PTR_ERR(tmp);
	if (!IS_ERR(tmp)) {
		struct dentry *dentry;
		struct nameidata nd;

		if (path_init(tmp, LOOKUP_PARENT, &nd))
			error = path_walk(tmp, &nd);
		if (error)
			goto out;
		dentry = lookup_create(&nd, 1);
		error = PTR_ERR(dentry);
		if (!IS_ERR(dentry)) {
			error = vfs_mkdir(nd.dentry->d_inode, dentry,
					  mode & ~current->fs->umask);
			dput(dentry);
		}
		up(&nd.dentry->d_inode->i_sem);
		path_release(&nd);
out:
		putname(tmp);
	}

	return error;
}

/*
 * We try to drop the dentry early: we should have
 * a usage count of 2 if we're the only user of this
 * dentry, and if that is true (possibly after pruning
 * the dcache), then we drop the dentry now.
 *
 * A low-level filesystem can, if it choses, legally
 * do a
 *
 *	if (!d_unhashed(dentry))
 *		return -EBUSY;
 *
 * if it cannot handle the case of removing a directory
 * that is still in use by something else..
 */
static void d_unhash(struct dentry *dentry)
{
	dget(dentry);
	switch (atomic_read(&dentry->d_count)) {
	default:
		shrink_dcache_parent(dentry);
		if (atomic_read(&dentry->d_count) != 2)
			break;
	case 2:
		d_drop(dentry);
	}
}

int vfs_rmdir(struct inode *dir, struct dentry *dentry)
{
	int error;

	error = may_delete(dir, dentry, 1);
	if (error)
		return error;

	if (!dir->i_op || !dir->i_op->rmdir)
		return -EPERM;

	DQUOT_INIT(dir);

	double_down(&dir->i_zombie, &dentry->d_inode->i_zombie);
	d_unhash(dentry);
	if (IS_DEADDIR(dir))
		error = -ENOENT;
	else if (d_mountpoint(dentry))
		error = -EBUSY;
	else {
		lock_kernel();
		error = dir->i_op->rmdir(dir, dentry);
		unlock_kernel();
		if (!error)
			dentry->d_inode->i_flags |= S_DEAD;
	}
	double_up(&dir->i_zombie, &dentry->d_inode->i_zombie);
	if (!error) {
		inode_dir_notify(dir, DN_DELETE);
		d_delete(dentry);
	}
	dput(dentry);

	return error;
}

asmlinkage long sys_rmdir(const char * pathname)
{
	int error = 0;
	char * name;
	struct dentry *dentry;
	struct nameidata nd;

	name = getname(pathname);
	if(IS_ERR(name))
		return PTR_ERR(name);

	if (path_init(name, LOOKUP_PARENT, &nd))
		error = path_walk(name, &nd);
	if (error)
		goto exit;

	switch(nd.last_type) {
		case LAST_DOTDOT:
			error = -ENOTEMPTY;
			goto exit1;
		case LAST_DOT:
			error = -EINVAL;
			goto exit1;
		case LAST_ROOT:
			error = -EBUSY;
			goto exit1;
	}
	down(&nd.dentry->d_inode->i_sem);
	dentry = lookup_hash(&nd.last, nd.dentry);
	error = PTR_ERR(dentry);
	if (!IS_ERR(dentry)) {
		error = vfs_rmdir(nd.dentry->d_inode, dentry);
		dput(dentry);
	}
	up(&nd.dentry->d_inode->i_sem);
exit1:
	path_release(&nd);
exit:
	putname(name);
	return error;
}

int vfs_unlink(struct inode *dir, struct dentry *dentry)
{
	int error;

	down(&dir->i_zombie);
	error = may_delete(dir, dentry, 0);
	if (!error) {
		error = -EPERM;
		if (dir->i_op && dir->i_op->unlink) {
			DQUOT_INIT(dir);
			if (d_mountpoint(dentry))
				error = -EBUSY;
			else {
				lock_kernel();
				error = dir->i_op->unlink(dir, dentry);
				unlock_kernel();
				if (!error)
					d_delete(dentry);
			}
		}
	}
	up(&dir->i_zombie);
	if (!error)
		inode_dir_notify(dir, DN_DELETE);
	return error;
}

asmlinkage long sys_unlink(const char * pathname)
{
	int error = 0;
	char * name;
	struct dentry *dentry;
	struct nameidata nd;

	name = getname(pathname);
	if(IS_ERR(name))
		return PTR_ERR(name);

	if (path_init(name, LOOKUP_PARENT, &nd))
		error = path_walk(name, &nd);
	if (error)
		goto exit;
	error = -EISDIR;
	if (nd.last_type != LAST_NORM)
		goto exit1;
	down(&nd.dentry->d_inode->i_sem);
	dentry = lookup_hash(&nd.last, nd.dentry);
	error = PTR_ERR(dentry);
	if (!IS_ERR(dentry)) {
		/* Why not before? Because we want correct error value */
		if (nd.last.name[nd.last.len])
			goto slashes;
		error = vfs_unlink(nd.dentry->d_inode, dentry);
	exit2:
		dput(dentry);
	}
	up(&nd.dentry->d_inode->i_sem);
exit1:
	path_release(&nd);
exit:
	putname(name);

	return error;

slashes:
	error = !dentry->d_inode ? -ENOENT :
		S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
	goto exit2;
}

int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
{
	int error;

	down(&dir->i_zombie);
	error = may_create(dir, dentry);
	if (error)
		goto exit_lock;

	error = -EPERM;
	if (!dir->i_op || !dir->i_op->symlink)
		goto exit_lock;