Illumos 5350 - clean up code in dnode_sync()

Author: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Alex Reece <alex.reece@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Richard Elling <richard.elling@richardelling.com>
Approved by: Dan McDonald <danmcd@omniti.com>

References:
  https://www.illumos.org/issues/5350
  illumos/illumos-gate@e651831

Ported-by: Chris Dunlop <chris@onthe.net.au>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #3382

Author: ahrens

module/zfs/dnode_sync.c

@@ -638,12 +638,11 @@ dnode_sync(dnode_t *dn, dmu_tx_t *tx)
 	freeing_dnode = dn->dn_free_txg > 0 && dn->dn_free_txg <= tx->tx_txg;
 
 	/*
-	 * We will either remove a spill block when a file is being removed
-	 * or we have been asked to remove it.
+	 * Remove the spill block if we have been explicitly asked to
+	 * remove it, or if the object is being removed.
 	 */
-	if (dn->dn_rm_spillblk[txgoff] ||
-	    ((dnp->dn_flags & DNODE_FLAG_SPILL_BLKPTR) && freeing_dnode)) {
-		if ((dnp->dn_flags & DNODE_FLAG_SPILL_BLKPTR))
+	if (dn->dn_rm_spillblk[txgoff] || freeing_dnode) {
+		if (dnp->dn_flags & DNODE_FLAG_SPILL_BLKPTR)
 			kill_spill = B_TRUE;
 		dn->dn_rm_spillblk[txgoff] = 0;
 	}