+/*
+ * Allocate a loaned anonymous arc buffer.
+ */
+arc_buf_t *
+dmu_request_arcbuf(dmu_buf_t *handle, int size)
+{
+ dnode_t *dn = ((dmu_buf_impl_t *)handle)->db_dnode;
+
+ return (arc_loan_buf(dn->dn_objset->os_spa, size));
+}
+
+/*
+ * Free a loaned arc buffer.
+ */
+void
+dmu_return_arcbuf(arc_buf_t *buf)
+{
+ arc_return_buf(buf, FTAG);
+ VERIFY(arc_buf_remove_ref(buf, FTAG) == 1);
+}
+
+/*
+ * When possible directly assign passed loaned arc buffer to a dbuf.
+ * If this is not possible copy the contents of passed arc buf via
+ * dmu_write().
+ */
+void
+dmu_assign_arcbuf(dmu_buf_t *handle, uint64_t offset, arc_buf_t *buf,
+ dmu_tx_t *tx)
+{
+ dnode_t *dn = ((dmu_buf_impl_t *)handle)->db_dnode;
+ dmu_buf_impl_t *db;
+ uint32_t blksz = (uint32_t)arc_buf_size(buf);
+ uint64_t blkid;
+
+ rw_enter(&dn->dn_struct_rwlock, RW_READER);
+ blkid = dbuf_whichblock(dn, offset);
+ VERIFY((db = dbuf_hold(dn, blkid, FTAG)) != NULL);
+ rw_exit(&dn->dn_struct_rwlock);
+
+ if (offset == db->db.db_offset && blksz == db->db.db_size) {
+ dbuf_assign_arcbuf(db, buf, tx);
+ dbuf_rele(db, FTAG);
+ } else {
+ dbuf_rele(db, FTAG);
+ ASSERT(dn->dn_objset->os.os == dn->dn_objset);
+ dmu_write(&dn->dn_objset->os, dn->dn_object, offset, blksz,
+ buf->b_data, tx);
+ dmu_return_arcbuf(buf);
+ }
+}
+