fix autofs/afs/etc. magic mountpoint breakage

We end up trying to kfree() nd.last.name on open("/mnt/tmp", O_CREAT)
if /mnt/tmp is an autofs direct mount.  The reason is that nd.last_type
is bogus here; we want LAST_BIND for everything of that kind and we
get LAST_NORM left over from finding parent directory.

So make sure that it *is* set properly; set to LAST_BIND before
doing ->follow_link() - for normal symlinks it will be changed
by __vfs_follow_link() and everything else needs it set that way.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
static int do_lookup(struct nameidata *nd, struct qstr *name,
		     struct path *path)
{
	struct vfsmount *mnt = nd->path.mnt;
	struct dentry *dentry, *parent;
	struct inode *dir;
	/*
	 * See if the low-level filesystem might want
	 * to use its own hash..
	 */
	if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) {
		int err = nd->path.dentry->d_op->d_hash(nd->path.dentry, name);
		if (err < 0)
			return err;
	}

	dentry = __d_lookup(nd->path.dentry, name);
	if (!dentry)
		goto need_lookup;
	if (dentry->d_op && dentry->d_op->d_revalidate)
		goto need_revalidate;
done:
	path->mnt = mnt;
	path->dentry = dentry;
	__follow_mount(path);
	return 0;

need_lookup:
	parent = nd->path.dentry;
	dir = parent->d_inode;

	mutex_lock(&dir->i_mutex);
	/*
	 * First re-do the cached lookup just in case it was created
	 * while we waited for the directory semaphore..
	 *
	 * FIXME! This could use version numbering or similar to
	 * avoid unnecessary cache lookups.
	 *
	 * The "dcache_lock" is purely to protect the RCU list walker
	 * from concurrent renames at this point (we mustn't get false
	 * negatives from the RCU list walk here, unlike the optimistic
	 * fast walk).
	 *
	 * so doing d_lookup() (with seqlock), instead of lockfree __d_lookup
	 */
	dentry = d_lookup(parent, name);
	if (!dentry) {
		struct dentry *new;

		/* Don't create child dentry for a dead directory. */
		dentry = ERR_PTR(-ENOENT);
		if (IS_DEADDIR(dir))
			goto out_unlock;

		new = d_alloc(parent, name);
		dentry = ERR_PTR(-ENOMEM);
		if (new) {
			dentry = dir->i_op->lookup(dir, new, nd);
			if (dentry)
				dput(new);
			else
				dentry = new;
		}
out_unlock:
		mutex_unlock(&dir->i_mutex);
		if (IS_ERR(dentry))
			goto fail;
		goto done;
	}

	/*
	 * Uhhuh! Nasty case: the cache was re-populated while
	 * we waited on the semaphore. Need to revalidate.
	 */
	mutex_unlock(&dir->i_mutex);
	if (dentry->d_op && dentry->d_op->d_revalidate) {
		dentry = do_revalidate(dentry, nd);
		if (!dentry)
			dentry = ERR_PTR(-ENOENT);
	}
	if (IS_ERR(dentry))
		goto fail;
	goto done;

need_revalidate:
	dentry = do_revalidate(dentry, nd);
	if (!dentry)
		goto need_lookup;
	if (IS_ERR(dentry))
		goto fail;
	goto done;

fail:
	return PTR_ERR(dentry);
}

static int do_lookup(struct nameidata *nd, struct qstr *name,
		     struct path *path)
{
	struct vfsmount *mnt = nd->path.mnt;
	struct dentry *dentry, *parent;
	struct inode *dir;
	/*
	 * See if the low-level filesystem might want
	 * to use its own hash..
	 */
	if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) {
		int err = nd->path.dentry->d_op->d_hash(nd->path.dentry, name);
		if (err < 0)
			return err;
	}

	dentry = __d_lookup(nd->path.dentry, name);
	if (!dentry)
		goto need_lookup;
	if (dentry->d_op && dentry->d_op->d_revalidate)
		goto need_revalidate;
done:
	path->mnt = mnt;
	path->dentry = dentry;
	__follow_mount(path);
	return 0;

need_lookup:
	parent = nd->path.dentry;
	dir = parent->d_inode;

	mutex_lock(&dir->i_mutex);
	/*
	 * First re-do the cached lookup just in case it was created
	 * while we waited for the directory semaphore..
	 *
	 * FIXME! This could use version numbering or similar to
	 * avoid unnecessary cache lookups.
	 *
	 * The "dcache_lock" is purely to protect the RCU list walker
	 * from concurrent renames at this point (we mustn't get false
	 * negatives from the RCU list walk here, unlike the optimistic
	 * fast walk).
	 *
	 * so doing d_lookup() (with seqlock), instead of lockfree __d_lookup
	 */
	dentry = d_lookup(parent, name);
	if (!dentry) {
		struct dentry *new;

		/* Don't create child dentry for a dead directory. */
		dentry = ERR_PTR(-ENOENT);
		if (IS_DEADDIR(dir))
			goto out_unlock;

		new = d_alloc(parent, name);
		dentry = ERR_PTR(-ENOMEM);
		if (new) {
			dentry = dir->i_op->lookup(dir, new, nd);
			if (dentry)
				dput(new);
			else
				dentry = new;
		}
out_unlock:
		mutex_unlock(&dir->i_mutex);
		if (IS_ERR(dentry))
			goto fail;
		goto done;
	}

	/*
	 * Uhhuh! Nasty case: the cache was re-populated while
	 * we waited on the semaphore. Need to revalidate.
	 */
	mutex_unlock(&dir->i_mutex);
	if (dentry->d_op && dentry->d_op->d_revalidate) {
		dentry = do_revalidate(dentry, nd);
		if (!dentry)
			dentry = ERR_PTR(-ENOENT);
	}
	if (IS_ERR(dentry))
		goto fail;
	goto done;

need_revalidate:
	dentry = do_revalidate(dentry, nd);
	if (!dentry)
		goto need_lookup;
	if (IS_ERR(dentry))
		goto fail;
	goto done;

fail:
	return PTR_ERR(dentry);
}
