Illumos openzfs#4082

4082 zfs receive gets EFBIG from dmu_tx_hold_free()
Reviewed by: Eric Schrock <eric.schrock@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Approved by: Richard Lowe <richlowe@richlowe.net>

References:
  https://www.illumos.org/issues/4082
  illumos/illumos-gate@5253393

Ported-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue openzfs#1775

module/zfs/dmu.c

@@ -672,6 +672,16 @@ dmu_free_long_range(objset_t *os, uint64_t object,
 	if (err != 0)
 		return (err);
 	err = dmu_free_long_range_impl(os, dn, offset, length);
+
+	/*
+	 * It is important to zero out the maxblkid when freeing the entire
+	 * file, so that (a) subsequent calls to dmu_free_long_range_impl()
+	 * will take the fast path, and (b) dnode_reallocate() can verify
+	 * that the entire file has been freed.
+	 */
+	if (offset == 0 && length == DMU_OBJECT_END)
+		dn->dn_maxblkid = 0;
+
 	dnode_rele(dn, FTAG);
 	return (err);
 }

module/zfs/dmu_tx.c

@@ -633,7 +633,7 @@ dmu_tx_hold_free(dmu_tx_t *tx, uint64_t object, uint64_t off, uint64_t len)
 	 */
 	if (dn->dn_datablkshift == 0) {
 		if (off != 0 || len < dn->dn_datablksz)
-			dmu_tx_count_write(txh, off, len);
+			dmu_tx_count_write(txh, 0, dn->dn_datablksz);
 	} else {
 		/* first block will be modified if it is not aligned */
 		if (!IS_P2ALIGNED(off, 1 << dn->dn_datablkshift))