+/*
+ * DMU support for xuio
+ */
+kstat_t *xuio_ksp = NULL;
+
+int
+dmu_xuio_init(xuio_t *xuio, int nblk)
+{
+ dmu_xuio_t *priv;
+ uio_t *uio = &xuio->xu_uio;
+
+ uio->uio_iovcnt = nblk;
+ uio->uio_iov = kmem_zalloc(nblk * sizeof (iovec_t), KM_SLEEP);
+
+ priv = kmem_zalloc(sizeof (dmu_xuio_t), KM_SLEEP);
+ priv->cnt = nblk;
+ priv->bufs = kmem_zalloc(nblk * sizeof (arc_buf_t *), KM_SLEEP);
+ priv->iovp = uio->uio_iov;
+ XUIO_XUZC_PRIV(xuio) = priv;
+
+ if (XUIO_XUZC_RW(xuio) == UIO_READ)
+ XUIOSTAT_INCR(xuiostat_onloan_rbuf, nblk);
+ else
+ XUIOSTAT_INCR(xuiostat_onloan_wbuf, nblk);
+
+ return (0);
+}
+
+void
+dmu_xuio_fini(xuio_t *xuio)
+{
+ dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
+ int nblk = priv->cnt;
+
+ kmem_free(priv->iovp, nblk * sizeof (iovec_t));
+ kmem_free(priv->bufs, nblk * sizeof (arc_buf_t *));
+ kmem_free(priv, sizeof (dmu_xuio_t));
+
+ if (XUIO_XUZC_RW(xuio) == UIO_READ)
+ XUIOSTAT_INCR(xuiostat_onloan_rbuf, -nblk);
+ else
+ XUIOSTAT_INCR(xuiostat_onloan_wbuf, -nblk);
+}
+
+/*
+ * Initialize iov[priv->next] and priv->bufs[priv->next] with { off, n, abuf }
+ * and increase priv->next by 1.
+ */
+int
+dmu_xuio_add(xuio_t *xuio, arc_buf_t *abuf, offset_t off, size_t n)
+{
+ struct iovec *iov;
+ uio_t *uio = &xuio->xu_uio;
+ dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
+ int i = priv->next++;
+
+ ASSERT(i < priv->cnt);
+ ASSERT(off + n <= arc_buf_size(abuf));
+ iov = uio->uio_iov + i;
+ iov->iov_base = (char *)abuf->b_data + off;
+ iov->iov_len = n;
+ priv->bufs[i] = abuf;
+ return (0);
+}
+
+int
+dmu_xuio_cnt(xuio_t *xuio)
+{
+ dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
+ return (priv->cnt);
+}
+
+arc_buf_t *
+dmu_xuio_arcbuf(xuio_t *xuio, int i)
+{
+ dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
+
+ ASSERT(i < priv->cnt);
+ return (priv->bufs[i]);
+}
+
+void
+dmu_xuio_clear(xuio_t *xuio, int i)
+{
+ dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
+
+ ASSERT(i < priv->cnt);
+ priv->bufs[i] = NULL;
+}
+
+static void
+xuio_stat_init(void)
+{
+ xuio_ksp = kstat_create("zfs", 0, "xuio_stats", "misc",
+ KSTAT_TYPE_NAMED, sizeof (xuio_stats) / sizeof (kstat_named_t),
+ KSTAT_FLAG_VIRTUAL);
+ if (xuio_ksp != NULL) {
+ xuio_ksp->ks_data = &xuio_stats;
+ kstat_install(xuio_ksp);
+ }
+}
+
+static void
+xuio_stat_fini(void)
+{
+ if (xuio_ksp != NULL) {
+ kstat_delete(xuio_ksp);
+ xuio_ksp = NULL;
+ }
+}
+
+void
+xuio_stat_wbuf_copied()
+{
+ XUIOSTAT_BUMP(xuiostat_wbuf_copied);
+}
+
+void
+xuio_stat_wbuf_nocopy()
+{
+ XUIOSTAT_BUMP(xuiostat_wbuf_nocopy);
+}
+