| n1 = 0, v = default-volid, avols[default-volid][m2].mapped?, m2 < # avols[default-volid], n1 < n, ebm-cons(avols), is-aligned(m1, EB_PAGE_SIZE), is-aligned(n, EB_PAGE_SIZE), is-aligned(n1, EB_PAGE_SIZE), default-volid ∈ avols, m1 + n ≤ LEB_SIZE, n + n2 ≤ # buf, avols[default-volid][m2].mapped? → avols[default-volid][m2].fill ≤ m1, ⌊err0⌋ ∨ err0 = ESUCCESS ⊦ [skip] (ebm-cons(avols) → default-volid ∈ avols), err0 = ESUCCESS |