Function mqfs_allocv

freebsd/kern/uipc_mqueue.c:735–818

* Allocate a vnode */

 * Allocate a vnode
 */
static int
mqfs_allocv(struct mount *mp, struct vnode **vpp, struct mqfs_node *pn)
{
	struct mqfs_vdata *vd;
	struct mqfs_info  *mqfs;
	struct vnode *newvpp;
	int error;

	mqfs = pn->mn_info;
	*vpp = NULL;
	sx_xlock(&mqfs->mi_lock);
	LIST_FOREACH(vd, &pn->mn_vnodes, mv_link) {
		if (vd->mv_vnode->v_mount == mp) {
			vhold(vd->mv_vnode);
			break;
		}
	}

	if (vd != NULL) {
found:
		*vpp = vd->mv_vnode;
		sx_xunlock(&mqfs->mi_lock);
		error = vget(*vpp, LK_RETRY | LK_EXCLUSIVE);
		vdrop(*vpp);
		return (error);
	}
	sx_xunlock(&mqfs->mi_lock);

	error = getnewvnode("mqueue", mp, &mqfs_vnodeops, &newvpp);
	if (error)
		return (error);
	vn_lock(newvpp, LK_EXCLUSIVE | LK_RETRY);
	error = insmntque(newvpp, mp);
	if (error != 0)
		return (error);

	sx_xlock(&mqfs->mi_lock);
	/*
	 * Check if it has already been allocated
	 * while we were blocked.
	 */
	LIST_FOREACH(vd, &pn->mn_vnodes, mv_link) {
		if (vd->mv_vnode->v_mount == mp) {
			vhold(vd->mv_vnode);
			sx_xunlock(&mqfs->mi_lock);

			vgone(newvpp);
			vput(newvpp);
			goto found;
		}
	}

	*vpp = newvpp;

	vd = uma_zalloc(mvdata_zone, M_WAITOK);
	(*vpp)->v_data = vd;
	vd->mv_vnode = *vpp;
	vd->mv_node = pn;