/*
 * Example use of vfs_inotab.
 */

int
ffs_mountfs(struct vnode *devvp, struct mount *mp, struct lwp *l)
{
	...
	const ptrdiff_t entoff = offsetof(struct inode, i_inoent);
	ump->um_inotab = vfs_inotab_create(
		offsetof(struct inode, i_vnode) - entoff,
		offsetof(struct inode, i_number) - entoff);
	...
}

int
ffs_unmount(struct mount *mp, int mntflags)
{
	...
	vfs_inotab_destroy(ump->um_inotab);
	...
}

int
ffs_vget(struct mount *mp, ino_t ino, struct vnode *vpp)
{
	struct ufsmount *const ump = VFSTOUFS(mp);
	struct vnode *vp = NULL, *vp0;
	static const struct inode zero_inode;
	struct inode *ip;
	int error = 0;

	/*
	 * Try to get an existing vnode for this inode.
	 */
	if ((vp = vfs_inotab_get(ump->um_inotab, ino, VGET_WAITOK)) != NULL)
		goto out;

	/*
	 * Create a new vnode for it instead.
	 */
	error = getnewvnode(VT_UFS, mp, ffs_vnodeop_p, NULL, &vp);
	if (error)
		goto out;

	ip = pool_cache_get(ffs_inode_cache, PR_WAITOK);
	*ip = zero_inode;
	ip->i_vnode = vp;
	ip->i_ump = ump;
	ip->i_fs = fs = ump->um_fs;
	ip->i_dev = dev;
	ip->i_number = ino;
#if defined(QUOTA) || defined(QUOTA2)
	ufsquota_init(ip);
#endif

	vp->v_data = ip;
	genfs_node_init(vp, &ffs_genfs_ops);

	/*
	 * Lock the vnode before we've published it and until we've
	 * finished initializing it.
	 */
	VOP_LOCK(vp, LK_EXCLUSIVE);

	/*
	 * Try to put this vnode in the table for the inode.  If
	 * someone else beat us to it, release ours and use theirs
	 * instead.
	 */
	if ((vp0 = vfs_inotab_put(ump->um_inotab, &ip->i_inoent, VGET_WAITOK))
	    != NULL) {
		VOP_UNLOCK(vp);
		genfs_vnode_destroy(vp);
#if defined(QUOTA) || defined(QUOTA2)
		ufsquota_free(ip);
#endif
		pool_cache_put(ffs_inode_cache, ip);
		ungetnewvnode(vp);
		vp = vp0;
		goto out;
	}

	/*
	 * Load the inode from disk.
	 */
	error = bread(ump->um_devvp, FFS_FSBTODB(fs, ino_to_fsba(fs, ino)),
	    (int)fs->fs_bsize, NOCRED, 0, &bp);
	if (error) {
		VOP_UNLOCK(vp);
		vrele(vp);
		vp = NULL;
		goto out;
	}
	if (ip->i_ump->um_fstype == UFS1)
		ip->i_din.ffs1_din = pool_cache_get(ffs_dinode1_cache,
		    PR_WAITOK);
	else
		ip->i_din.ffs2_din = pool_cache_get(ffs_dinode2_cache,
		    PR_WAITOK);
	ffs_load_inode(bp, ip, fs, ino);
	brelse(bp, 0);

	/*
	 * Initialize the vnode from the inode.
	 */
	ufs_vinit(mp, ffs_specop_p, ffs_fifoop_p, vp);

	/*
	 * Attach the mount.
	 */
	ip->i_devvp = ump->um_devvp;
	vref(ip->i_devvp);

	/*
	 * Ensure that uid and gid are correct. This is a temporary
	 * fix until fsck has been changed to do the update.
	 */
	if (fs->fs_old_inodefmt < FS_44INODEFMT) {		/* XXX */
		ip->i_uid = ip->i_ffs1_ouid;			/* XXX */
		ip->i_gid = ip->i_ffs1_ogid;			/* XXX */
	}

	/*
	 * Set the uvm size from the inode size.
	 */
	uvm_vnp_setsize(vp, ip->i_size);

	VOP_UNLOCK(vp);
out:	*vpp = vp;
	return error;
}