Function vm_fault

freebsd/vm/vm_fault.c:1276–1634

}

int
vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
    int fault_flags, vm_page_t *m_hold)
{
	struct faultstate fs;
	int ahead, behind, faultcount;
	int nera, result, rv;
	bool dead, hardfault;

	VM_CNT_INC(v_vm_faults);

	if ((curthread->td_pflags & TDP_NOFAULTING) != 0)
		return (KERN_PROTECTION_FAILURE);

	fs.vp = NULL;
	fs.vaddr = vaddr;
	fs.m_hold = m_hold;
	fs.fault_flags = fault_flags;
	fs.map = map;
	fs.lookup_still_valid = false;
	fs.oom = 0;
	faultcount = 0;
	nera = -1;
	hardfault = false;

RetryFault:
	fs.fault_type = fault_type;

	/*
	 * Find the backing store object and offset into it to begin the
	 * search.
	 */
	result = vm_fault_lookup(&fs);
	if (result != KERN_SUCCESS) {
		if (result == KERN_RESOURCE_SHORTAGE)
			goto RetryFault;
		return (result);
	}

	/*
	 * Try to avoid lock contention on the top-level object through
	 * special-case handling of some types of page faults, specifically,
	 * those that are mapping an existing page from the top-level object.
	 * Under this condition, a read lock on the object suffices, allowing
	 * multiple page faults of a similar type to run in parallel.
	 */
	if (fs.vp == NULL /* avoid locked vnode leak */ &&
	    (fs.entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK) == 0 &&
	    (fs.fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0) {
		VM_OBJECT_RLOCK(fs.first_object);
		rv = vm_fault_soft_fast(&fs);
		if (rv == KERN_SUCCESS)
			return (rv);
		if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) {
			VM_OBJECT_RUNLOCK(fs.first_object);
			VM_OBJECT_WLOCK(fs.first_object);
		}
	} else {