Function vn_dirty_blk

freebsd/vm/vnode_pager.c:1250–1259

}

static bool
vn_dirty_blk(vm_page_t m, vm_ooffset_t offset)
{

	KASSERT(IDX_TO_OFF(m->pindex) <= offset &&
	    offset < IDX_TO_OFF(m->pindex + 1),
	    ("page %p pidx %ju offset %ju", m, (uintmax_t)m->pindex,
	    (uintmax_t)offset));
	return ((m->dirty & ((vm_page_bits_t)1 << vn_off2bidx(offset))) != 0);
}

/*
 * This is now called from local media FS's to operate against their