Function vmem_alloc

freebsd/kern/subr_vmem.c:1325–1352

* vmem_alloc: allocate resource from the arena. */

 * vmem_alloc: allocate resource from the arena.
 */
int
vmem_alloc(vmem_t *vm, vmem_size_t size, int flags, vmem_addr_t *addrp)
{
	const int strat __unused = flags & VMEM_FITMASK;
	qcache_t *qc;

	flags &= VMEM_FLAGS;
	MPASS(size > 0);
	MPASS(strat == M_BESTFIT || strat == M_FIRSTFIT || strat == M_NEXTFIT);
	if ((flags & M_NOWAIT) == 0)
		WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "vmem_alloc");

	if (size <= vm->vm_qcache_max) {
		/*
		 * Resource 0 cannot be cached, so avoid a blocking allocation
		 * in qc_import() and give the vmem_xalloc() call below a chance
		 * to return 0.
		 */
		qc = &vm->vm_qcache[(size - 1) >> vm->vm_quantum_shift];
		*addrp = (vmem_addr_t)uma_zalloc(qc->qc_cache,
		    (flags & ~M_WAITOK) | M_NOWAIT);
		if (__predict_true(*addrp != 0))
			return (0);
	}

	return (vmem_xalloc(vm, size, 0, 0, 0, VMEM_ADDR_MIN, VMEM_ADDR_MAX,
	    flags, addrp));
}

int
vmem_xalloc(vmem_t *vm, const vmem_size_t size0, vmem_size_t align,