Function rman_adjust_resource

freebsd/kern/subr_rman.c:314–433

Shrink or extend one or both ends of an allocated resource. */

/* Shrink or extend one or both ends of an allocated resource. */
int
rman_adjust_resource(struct resource *rr, rman_res_t start, rman_res_t end)
{
	struct resource_i *r, *s, *t, *new;
	struct rman *rm;

	/* Not supported for shared resources. */
	r = rr->__r_i;
	if (r->r_flags & RF_SHAREABLE)
		return (EINVAL);

	/*
	 * This does not support wholesale moving of a resource.  At
	 * least part of the desired new range must overlap with the
	 * existing resource.
	 */
	if (end < r->r_start || r->r_end < start)
		return (EINVAL);

	/*
	 * Find the two resource regions immediately adjacent to the
	 * allocated resource.
	 */
	rm = r->r_rm;
	mtx_lock(rm->rm_mtx);
#ifdef INVARIANTS
	TAILQ_FOREACH(s, &rm->rm_list, r_link) {
		if (s == r)
			break;
	}
	if (s == NULL)
		panic("resource not in list");
#endif
	s = TAILQ_PREV(r, resource_head, r_link);
	t = TAILQ_NEXT(r, r_link);
	KASSERT(s == NULL || s->r_end + 1 == r->r_start,
	    ("prev resource mismatch"));
	KASSERT(t == NULL || r->r_end + 1 == t->r_start,
	    ("next resource mismatch"));

	/*
	 * See if the changes are permitted.  Shrinking is always allowed,
	 * but growing requires sufficient room in the adjacent region.
	 */
	if (start < r->r_start && (s == NULL || (s->r_flags & RF_ALLOCATED) ||
	    s->r_start > start)) {
		mtx_unlock(rm->rm_mtx);
		return (EBUSY);
	}
	if (end > r->r_end && (t == NULL || (t->r_flags & RF_ALLOCATED) ||
	    t->r_end < end)) {
		mtx_unlock(rm->rm_mtx);
		return (EBUSY);
	}

	/*
	 * While holding the lock, grow either end of the resource as
	 * needed and shrink either end if the shrinking does not require