receive_freeobjects() skips freeing some objects

module/zfs/dmu_send.c

@@ -2563,12 +2563,10 @@ receive_freeobjects(struct receive_writer_arg *rwa,
 		int err;
 
 		err = dmu_object_info(rwa->os, obj, &doi);
-		if (err == ENOENT) {
-			obj++;
+		if (err == ENOENT)
 			continue;
-		} else if (err != 0) {
+		else if (err != 0)
 			return (err);
-		}
 
 		err = dmu_free_long_object(rwa->os, obj);
 		if (err != 0)

tests/runfiles/linux.run

@@ -525,7 +525,7 @@ tests = ['rsend_001_pos', 'rsend_002_pos', 'rsend_003_pos', 'rsend_004_pos',
     'send-c_lz4_disabled', 'send-c_recv_lz4_disabled',
     'send-c_mixed_compression', 'send-c_stream_size_estimate', 'send-cD',
     'send-c_embedded_blocks', 'send-c_resume', 'send-cpL_varied_recsize',
-    'send-c_recv_dedup', 'send_encrypted_heirarchy']
+    'send-c_recv_dedup', 'send_encrypted_heirarchy', 'send_freeobjects']
 
 [tests/functional/scrub_mirror]
 tests = ['scrub_mirror_001_pos', 'scrub_mirror_002_pos',

tests/zfs-tests/tests/functional/rsend/Makefile.am

@@ -38,4 +38,5 @@ dist_pkgdata_SCRIPTS = \
 	send-c_verify_ratio.ksh \
 	send-c_volume.ksh \
 	send-c_zstreamdump.ksh \
-	send-cpL_varied_recsize.ksh
+	send-cpL_varied_recsize.ksh \
+	send_freeobjects.ksh

tests/zfs-tests/tests/functional/rsend/send_freeobjects.ksh

@@ -0,0 +1,81 @@
+#!/bin/ksh
+
+#
+# This file and its contents are supplied under the terms of the
+# Common Development and Distribution License ("CDDL"), version 1.0.
+# You may only use this file in accordance with the terms of version
+# 1.0 of the CDDL.
+#
+# A full copy of the text of the CDDL should have accompanied this
+# source.  A copy of the CDDL is also available via the Internet at
+# http://www.illumos.org/license/CDDL.
+#
+
+#
+# Copyright (c) 2017 by Lawrence Livermore National Security, LLC.
+#
+
+. $STF_SUITE/include/libtest.shlib
+. $STF_SUITE/tests/functional/rsend/rsend.kshlib
+
+#
+# Description:
+# Verify FREEOBJECTS record frees sequential objects (See
+# https://github.com/zfsonlinux/zfs/issues/6694)
+#
+# Strategy:
+# 1. Create three files with sequential object numbers, f1 f2 and f3
+# 2. Delete f2
+# 3. Take snapshot A
+# 4. Delete f3
+# 5. Take snapshot B
+# 6. Receive a full send of A
+# 7. Receive an incremental send of B
+# 8. Fail test if f3 exists on received snapshot B
+#
+
+verify_runnable "both"
+
+log_assert "Verify FREEOBJECTS record frees sequential objects"
+
+sendds=sendfo
+recvds=recvfo
+f1=/$POOL/$sendds/f1
+f2=/$POOL/$sendds/f2
+f3=/$POOL/$sendds/f3
+
+#
+# We need to set xattr=sa and dnodesize=legacy to guarantee sequential
+# object numbers for this test. Otherwise, if we used directory-based
+# xattrs, SELinux extended attributes might consume intervening object
+# numbers.
+#
+log_must zfs create -o xattr=sa -o dnodesize=legacy $POOL/$sendds
+
+tries=100
+for ((i=0; i<$tries; i++)); do
+	touch $f1 $f2 $f3
+	o1=$(ls -li $f1 | awk '{print $1}')
+	o2=$(ls -li $f2 | awk '{print $1}')
+	o3=$(ls -li $f3 | awk '{print $1}')
+
+	if [[ $o2 -ne $(( $o1 + 1 )) ]] || [[ $o3 -ne $(( $o2 + 1 )) ]]; then
+		rm -f $f1 $f2 $f3
+	else
+		break
+	fi
+done
+
+if [[ $i -eq $tries ]]; then
+	log_fail "Failed to create three sequential objects"
+fi
+
+log_must rm $f2
+log_must zfs snap $POOL/$sendds@A
+log_must rm $f3
+log_must zfs snap $POOL/$sendds@B
+log_must eval "zfs send $POOL/$sendds@A | zfs recv $POOL/$recvds"
+log_must eval "zfs send -i $POOL/$sendds@A $POOL/$sendds@B |" \
+	"zfs recv $POOL/$recvds"
+log_mustnot zdb $POOL/$recvds@B $o3
+log_pass "Verify FREEOBJECTS record frees sequential objects"