Illumos 4881 - zfs send performance regression with embedded data

4881 zfs send performance degradation when embedded block pointers
     are encountered

Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Approved by: Dan McDonald <danmcd@omniti.com>

References:
  https://www.illumos.org/issues/4881
  illumos/illumos-gate@06315b7

Ported by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2547

module/zfs/dmu_traverse.c

@@ -20,7 +20,7 @@
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2013 by Delphix. All rights reserved.
+ * Copyright (c) 2012, 2014 by Delphix. All rights reserved.
  */
 
 #include <sys/zfs_context.h>
@@ -197,6 +197,16 @@ traverse_prefetch_metadata(traverse_data_t *td,
 	    ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, zb);
 }
 
+static boolean_t
+prefetch_needed(prefetch_data_t *pfd, const blkptr_t *bp)
+{
+	ASSERT(pfd->pd_flags & TRAVERSE_PREFETCH_DATA);
+	if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp) ||
+	    BP_GET_TYPE(bp) == DMU_OT_INTENT_LOG)
+		return (B_FALSE);
+	return (B_TRUE);
+}
+
 static int
 traverse_visitbp(traverse_data_t *td, const dnode_phys_t *dnp,
     const blkptr_t *bp, const zbookmark_t *zb)
@@ -239,16 +249,8 @@ traverse_visitbp(traverse_data_t *td, const dnode_phys_t *dnp,
 		return (0);
 	}
 
-	if (BP_IS_HOLE(bp)) {
-		err = td->td_func(td->td_spa, NULL, bp, zb, dnp, td->td_arg);
-		if (err != 0)
-			goto post;
-		return (0);
-	}
-
-	if (td->td_pfd && !td->td_pfd->pd_exited &&
-	    ((td->td_pfd->pd_flags & TRAVERSE_PREFETCH_DATA) ||
-	    BP_GET_TYPE(bp) == DMU_OT_DNODE || BP_GET_LEVEL(bp) > 0)) {
+	if (td->td_pfd != NULL && !td->td_pfd->pd_exited &&
+	    prefetch_needed(td->td_pfd, bp)) {
 		mutex_enter(&td->td_pfd->pd_mtx);
 		ASSERT(td->td_pfd->pd_blks_fetched >= 0);
 		while (td->td_pfd->pd_blks_fetched == 0 &&
@@ -259,6 +261,13 @@ traverse_visitbp(traverse_data_t *td, const dnode_phys_t *dnp,
 		mutex_exit(&td->td_pfd->pd_mtx);
 	}
 
+	if (BP_IS_HOLE(bp)) {
+		err = td->td_func(td->td_spa, NULL, bp, zb, dnp, td->td_arg);
+		if (err != 0)
+			goto post;
+		return (0);
+	}
+
 	if (td->td_flags & TRAVERSE_PRE) {
 		err = td->td_func(td->td_spa, NULL, bp, zb, dnp,
 		    td->td_arg);
@@ -448,10 +457,7 @@ traverse_prefetcher(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
 	if (pfd->pd_cancel)
 		return (SET_ERROR(EINTR));
 
-	if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp) ||
-	    !((pfd->pd_flags & TRAVERSE_PREFETCH_DATA) ||
-	    BP_GET_TYPE(bp) == DMU_OT_DNODE || BP_GET_LEVEL(bp) > 0) ||
-	    BP_GET_TYPE(bp) == DMU_OT_INTENT_LOG)
+	if (!prefetch_needed(pfd, bp))
 		return (0);
 
 	mutex_enter(&pfd->pd_mtx);