Function vm_fault_dirty

freebsd/vm/vm_fault.c:251–292

}

static void
vm_fault_dirty(struct faultstate *fs, vm_page_t m)
{
	bool need_dirty;

	if (((fs->prot & VM_PROT_WRITE) == 0 &&
	    (fs->fault_flags & VM_FAULT_DIRTY) == 0) ||
	    (m->oflags & VPO_UNMANAGED) != 0)
		return;

	VM_PAGE_OBJECT_BUSY_ASSERT(m);

	need_dirty = ((fs->fault_type & VM_PROT_WRITE) != 0 &&
	    (fs->fault_flags & VM_FAULT_WIRE) == 0) ||
	    (fs->fault_flags & VM_FAULT_DIRTY) != 0;

	vm_object_set_writeable_dirty(m->object);

	/*
	 * If the fault is a write, we know that this page is being
	 * written NOW so dirty it explicitly to save on
	 * pmap_is_modified() calls later.
	 *
	 * Also, since the page is now dirty, we can possibly tell
	 * the pager to release any swap backing the page.
	 */
	if (need_dirty && vm_page_set_dirty(m) == 0) {
		/*
		 * If this is a NOSYNC mmap we do not want to set PGA_NOSYNC
		 * if the page is already dirty to prevent data written with
		 * the expectation of being synced from not being synced.
		 * Likewise if this entry does not request NOSYNC then make
		 * sure the page isn't marked NOSYNC.  Applications sharing
		 * data should use the same flags to avoid ping ponging.
		 */
		if ((fs->entry->eflags & MAP_ENTRY_NOSYNC) != 0)
			vm_page_aflag_set(m, PGA_NOSYNC);
		else
			vm_page_aflag_clear(m, PGA_NOSYNC);
	}

}

/*
 * Unlocks fs.first_object and fs.map on success.