+#ifdef HAVE_BLK_QUEUE_DISCARD
+static void
+zvol_discard(void *arg)
+{
+ struct request *req = (struct request *)arg;
+ struct request_queue *q = req->q;
+ zvol_state_t *zv = q->queuedata;
+ uint64_t offset = blk_rq_pos(req) << 9;
+ uint64_t size = blk_rq_bytes(req);
+ int error;
+ rl_t *rl;
+
+ if (offset + size > zv->zv_volsize) {
+ blk_end_request(req, -EIO, size);
+ return;
+ }
+
+ if (size == 0) {
+ blk_end_request(req, 0, size);
+ return;
+ }
+
+ rl = zfs_range_lock(&zv->zv_znode, offset, size, RL_WRITER);
+
+ error = dmu_free_long_range(zv->zv_objset, ZVOL_OBJ, offset, size);
+
+ /*
+ * TODO: maybe we should add the operation to the log.
+ */
+
+ zfs_range_unlock(rl);
+
+ blk_end_request(req, -error, size);
+}
+#endif /* HAVE_BLK_QUEUE_DISCARD */
+