ZFS send fails to dump objects larger than 128PiB

When dumping objects larger than 128PiB it's possible for do_dump() to
miscalculate the FREE_RECORD offset due to an integer overflow
condition: this prevents the receiving end from correctly restoring
the dumped object.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
Signed-off-by: loli10K <ezomori.nozomu@gmail.com>
Closes #6760

tests/runfiles/linux.run

@@ -167,7 +167,8 @@ tests = ['zfs_rollback_001_pos', 'zfs_rollback_002_pos',
 [tests/functional/cli_root/zfs_send]
 tests = ['zfs_send_001_pos', 'zfs_send_002_pos', 'zfs_send_003_pos',
     'zfs_send_004_neg', 'zfs_send_005_pos', 'zfs_send_006_pos',
-    'zfs_send_007_pos', 'zfs_send_encrypted', 'zfs_send_raw']
+    'zfs_send_007_pos', 'zfs_send_encrypted', 'zfs_send_raw',
+    'zfs_send_sparse']
 
 [tests/functional/cli_root/zfs_set]
 tests = ['cache_001_pos', 'cache_002_neg', 'canmount_001_pos',

tests/zfs-tests/tests/functional/cli_root/zfs_send/Makefile.am

@@ -11,4 +11,5 @@ dist_pkgdata_SCRIPTS = \
 	zfs_send_006_pos.ksh \
 	zfs_send_007_pos.ksh \
 	zfs_send_encrypted.ksh \
-	zfs_send_raw.ksh
+	zfs_send_raw.ksh \
+	zfs_send_sparse.ksh

tests/zfs-tests/tests/functional/cli_root/zfs_send/zfs_send_sparse.ksh

@@ -0,0 +1,83 @@
+#!/bin/ksh -p
+#
+# 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 2017, loli10K <ezomori.nozomu@gmail.com>. All rights reserved.
+#
+
+. $STF_SUITE/include/libtest.shlib
+
+#
+# DESCRIPTION:
+# 'zfs send' should be able to send (big) sparse files correctly.
+#
+# STRATEGY:
+# 1. Create sparse files of various size
+# 2. Snapshot and send these sparse files
+# 3. Verify these files are received correctly and we don't trigger any issue
+#    like the one described in https://github.com/zfsonlinux/zfs/pull/6760
+#
+
+verify_runnable "both"
+
+function cleanup
+{
+        datasetexists $SENDFS && log_must zfs destroy -r $SENDFS
+        datasetexists $RECVFS && log_must zfs destroy -r $RECVFS
+}
+
+#
+# Write 1 random byte at $offset of "source" file in $sendfs dataset
+# Snapshot and send $sendfs dataset to $recvfs
+# Compare the received file with its source
+#
+function write_compare_files # <sendfs> <recvfs> <offset>
+{
+	typeset sendfs="$1"
+	typeset recvfs="$2"
+	typeset offset="$3"
+
+	# create source filesystem
+	log_must zfs create $sendfs
+	# write sparse file
+	sendfile="$(get_prop mountpoint $sendfs)/data.bin"
+	log_must dd if=/dev/urandom of=$sendfile bs=1 count=1 seek=$offset
+	# send/receive the file
+	log_must zfs snapshot $sendfs@snap
+	log_must eval "zfs send $sendfs@snap | zfs receive $recvfs"
+	# compare sparse files
+	recvfile="$(get_prop mountpoint $recvfs)/data.bin"
+	log_must cmp $sendfile $recvfile $offset $offset
+	sendsz=$(stat -c '%s' $sendfile)
+	recvsz=$(stat -c '%s' $recvfile)
+	if [[ $sendsz -ne $recvsz ]]; then
+		log_fail "$sendfile ($sendsz) and $recvfile ($recvsz) differ."
+	fi
+	# cleanup
+	log_must zfs destroy -r $sendfs
+	log_must zfs destroy -r $recvfs
+}
+
+log_assert "'zfs send' should be able to send (big) sparse files correctly."
+log_onexit cleanup
+
+SENDFS="$TESTPOOL/sendfs"
+RECVFS="$TESTPOOL/recvfs"
+OFF_T_MAX="$(echo '2 ^ 40 * 8 - 1' | bc)"
+
+for i in {1..60}; do
+	offset=$(echo "2 ^ $i" | bc)
+	[[ is_32bit ]] && [[ $offset -ge $OFF_T_MAX ]] && continue;
+	write_compare_files $SENDFS $RECVFS $offset
+done
+
+log_pass "'zfs send' sends (big) sparse files correctly."