| # buf1 = EB_PAGE_SIZE, pebs[m0] = mkpeb(buf0, m1, false), buf1 = emptypage, err = ESUCCESS, m0 < # pebs, mtd-cons(pebs), 2 * EB_PAGE_SIZE ≤ PEB_SIZE, err = ESUCCESS → buf1 = subarray(buf0, EB_PAGE_SIZE, EB_PAGE_SIZE), err = ESUCCESS ∨ ⌊err⌋ ⊦ ⟪avhdr := empty⟫ true |