VCBS
uint64_t offset = P2ALIGN(zio->io_offset, VCBS);
ve->ve_abd = abd_alloc_for_io(VCBS, B_TRUE);
uint64_t cache_phase = P2PHASE(zio->io_offset, VCBS);
ASSERT3U(fio->io_size, ==, VCBS);
uint64_t cache_offset = P2ALIGN(zio->io_offset, VCBS);
uint64_t cache_phase = P2PHASE(zio->io_offset, VCBS);
if (P2BOUNDARY(zio->io_offset, zio->io_size, VCBS))
ASSERT3U(cache_phase + zio->io_size, <=, VCBS);
ve->ve_abd, VCBS, ZIO_TYPE_READ, ZIO_PRIORITY_NOW,
uint64_t min_offset = P2ALIGN(io_start, VCBS);
uint64_t max_offset = P2ROUNDUP(io_end, VCBS);
uint64_t end = MIN(ve->ve_offset + VCBS, io_end);