a.patch

diff --git a/configure.ac b/configure.ac
index 0893af4..4433cde 100644
--- a/configure.ac
+++ b/configure.ac
@@ -252,6 +252,7 @@ AC_CONFIG_FILES([
 	tests/zfs-tests/tests/functional/cli_user/zpool_iostat/Makefile
 	tests/zfs-tests/tests/functional/cli_user/zpool_list/Makefile
 	tests/zfs-tests/tests/functional/compression/Makefile
+	tests/zfs-tests/tests/functional/cp_files/Makefile
 	tests/zfs-tests/tests/functional/ctime/Makefile
 	tests/zfs-tests/tests/functional/deadman/Makefile
 	tests/zfs-tests/tests/functional/delegate/Makefile
diff --git a/module/zfs/zap.c b/module/zfs/zap.c
index 1c2030b..d899ccd 100644
--- a/module/zfs/zap.c
+++ b/module/zfs/zap.c
@@ -818,19 +818,15 @@ fzap_lookup(zap_name_t *zn,
 	return (err);
 }
 
-#define	MAX_EXPAND_RETRIES  2
-
 int
 fzap_add_cd(zap_name_t *zn,
     uint64_t integer_size, uint64_t num_integers,
     const void *val, uint32_t cd, void *tag, dmu_tx_t *tx)
 {
 	zap_leaf_t *l;
-	zap_leaf_t *prev_l = NULL;
 	int err;
 	zap_entry_handle_t zeh;
 	zap_t *zap = zn->zn_zap;
-	int expand_retries = 0;
 
 	ASSERT(RW_LOCK_HELD(&zap->zap_rwlock));
 	ASSERT(!zap->zap_ismicro);
@@ -854,20 +850,9 @@ retry:
 	if (err == 0) {
 		zap_increment_num_entries(zap, 1, tx);
 	} else if (err == EAGAIN) {
-		/*
-		 * If the last two expansions did not help, there is no point
-		 * trying to expand again
-		 */
-		if (expand_retries > MAX_EXPAND_RETRIES && prev_l == l) {
-			err = SET_ERROR(ENOSPC);
-			goto out;
-		}
-
 		err = zap_expand_leaf(zn, l, tag, tx, &l);
 		zap = zn->zn_zap;	/* zap_expand_leaf() may change zap */
 		if (err == 0) {
-			prev_l = l;
-			expand_retries++;
 			goto retry;
 		} else if (err == ENOSPC) {
 			/*
diff --git a/module/zfs/zap_micro.c b/module/zfs/zap_micro.c
index ad9a621..791cbee 100644
--- a/module/zfs/zap_micro.c
+++ b/module/zfs/zap_micro.c
@@ -673,16 +673,15 @@ mzap_upgrade(zap_t **zapp, void *tag, dmu_tx_t *tx, zap_flags_t flags)
 		dprintf("adding %s=%llu\n",
 		    mze->mze_name, mze->mze_value);
 		zn = zap_name_alloc(zap, mze->mze_name, 0);
-		err = fzap_add_cd(zn, 8, 1, &mze->mze_value, mze->mze_cd,
-		    tag, tx);
+		/* If we fail here, we would end up losing entries */
+		VERIFY0(fzap_add_cd(zn, 8, 1, &mze->mze_value, mze->mze_cd,
+		    tag, tx));
 		zap = zn->zn_zap;	/* fzap_add_cd() may change zap */
 		zap_name_free(zn);
-		if (err)
-			break;
 	}
 	vmem_free(mzp, sz);
 	*zapp = zap;
-	return (err);
+	return (0);
 }
 
 /*
diff --git a/tests/runfiles/linux.run b/tests/runfiles/linux.run
index 1852937..65b4c97 100644
--- a/tests/runfiles/linux.run
+++ b/tests/runfiles/linux.run
@@ -469,6 +469,10 @@ tests = ['compress_001_pos', 'compress_002_pos', 'compress_003_pos',
     'compress_004_pos']
 tags = ['functional', 'compression']
 
+[tests/functional/cp_files]
+tests = ['cp_files_001_pos']
+tags = ['functional', 'cp_files']
+
 [tests/functional/ctime]
 tests = ['ctime_001_pos' ]
 tags = ['functional', 'ctime']
diff --git a/tests/zfs-tests/tests/functional/Makefile.am b/tests/zfs-tests/tests/functional/Makefile.am
index 4510d51..0aa0c94 100644
--- a/tests/zfs-tests/tests/functional/Makefile.am
+++ b/tests/zfs-tests/tests/functional/Makefile.am
@@ -13,6 +13,7 @@ SUBDIRS = \
 	cli_root \
 	cli_user \
 	compression \
+	cp_files \
 	ctime \
 	deadman \
 	delegate \
diff --git a/tests/zfs-tests/tests/functional/cp_files/.gitignore b/tests/zfs-tests/tests/functional/cp_files/.gitignore
new file mode 100644
index 0000000..eac05e1
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/cp_files/.gitignore
@@ -0,0 +1 @@
+/cp_files
diff --git a/tests/zfs-tests/tests/functional/cp_files/Makefile.am b/tests/zfs-tests/tests/functional/cp_files/Makefile.am
new file mode 100644
index 0000000..06c31f5
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/cp_files/Makefile.am
@@ -0,0 +1,13 @@
+include $(top_srcdir)/config/Rules.am
+
+pkgdatadir = $(datadir)/@PACKAGE@/zfs-tests/tests/functional/cp_files
+
+dist_pkgdata_SCRIPTS = \
+	cp_files_001_pos.ksh \
+	cleanup.ksh \
+	setup.ksh
+
+pkgexecdir = $(datadir)/@PACKAGE@/zfs-tests/tests/functional/cp_files
+
+pkgexec_PROGRAMS = cp_files
+cp_files_SOURCES= cp_files.c
diff --git a/tests/zfs-tests/tests/functional/cp_files/cleanup.ksh b/tests/zfs-tests/tests/functional/cp_files/cleanup.ksh
new file mode 100755
index 0000000..3166bd6
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/cp_files/cleanup.ksh
@@ -0,0 +1,34 @@
+#!/bin/ksh -p
+#
+# CDDL HEADER START
+#
+# The contents of this file are subject to the terms of the
+# Common Development and Distribution License (the "License").
+# You may not use this file except in compliance with the License.
+#
+# You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+# or http://www.opensolaris.org/os/licensing.
+# See the License for the specific language governing permissions
+# and limitations under the License.
+#
+# When distributing Covered Code, include this CDDL HEADER in each
+# file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+# If applicable, add the following below this CDDL HEADER, with the
+# fields enclosed by brackets "[]" replaced with your own identifying
+# information: Portions Copyright [yyyy] [name of copyright owner]
+#
+# CDDL HEADER END
+#
+
+#
+# Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
+# Use is subject to license terms.
+#
+
+#
+# Copyright (c) 2013 by Delphix. All rights reserved.
+#
+
+. $STF_SUITE/include/libtest.shlib
+
+default_cleanup
diff --git a/tests/zfs-tests/tests/functional/cp_files/cp_files.c b/tests/zfs-tests/tests/functional/cp_files/cp_files.c
new file mode 100644
index 0000000..9af64a1
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/cp_files/cp_files.c
@@ -0,0 +1,58 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <dirent.h>
+#include <errno.h>
+#include <string.h>
+
+int
+main(int argc, char *argv[])
+{
+	int tfd;
+	DIR *sdir;
+	struct dirent *dirent;
+
+	if (argc != 3) {
+		fprintf(stderr, "Usage: %s SRC DST\n", argv[0]);
+		exit(1);
+	}
+
+	sdir = opendir(argv[1]);
+	if (sdir == NULL) {
+		fprintf(stderr, "Failed to open %s: %s\n",
+		    argv[1], strerror(errno));
+		exit(2);
+	}
+
+	tfd = open(argv[2], O_DIRECTORY);
+	if (tfd < 0) {
+		fprintf(stderr, "Failed to open %s: %s\n",
+		    argv[2], strerror(errno));
+		closedir(sdir);
+		exit(3);
+	}
+
+	while ((dirent = readdir(sdir)) != NULL) {
+		if (dirent->d_name[0] == '.' &&
+		    (dirent->d_name[1] == '.' || dirent->d_name[1] == '\0'))
+			continue;
+
+		int fd = openat(tfd, dirent->d_name, O_CREAT|O_WRONLY, 0666);
+		if (fd < 0) {
+			fprintf(stderr, "Failed to create %s/%s: %s\n",
+			    argv[2], dirent->d_name, strerror(errno));
+			closedir(sdir);
+			close(tfd);
+			exit(4);
+		}
+		close(fd);
+	}
+
+	closedir(sdir);
+	close(tfd);
+
+	return (0);
+}
diff --git a/tests/zfs-tests/tests/functional/cp_files/cp_files_001_pos.ksh b/tests/zfs-tests/tests/functional/cp_files/cp_files_001_pos.ksh
new file mode 100755
index 0000000..3e138cf
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/cp_files/cp_files_001_pos.ksh
@@ -0,0 +1,74 @@
+#! /bin/ksh -p
+#
+# CDDL HEADER START
+#
+# The contents of this file are subject to the terms of the
+# Common Development and Distribution License (the "License").
+# You may not use this file except in compliance with the License.
+#
+# You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+# or http://www.opensolaris.org/os/licensing.
+# See the License for the specific language governing permissions
+# and limitations under the License.
+#
+# When distributing Covered Code, include this CDDL HEADER in each
+# file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+# If applicable, add the following below this CDDL HEADER, with the
+# fields enclosed by brackets "[]" replaced with your own identifying
+# information: Portions Copyright [yyyy] [name of copyright owner]
+#
+# CDDL HEADER END
+#
+
+#
+# Copyright (c) 2018 by Nutanix. All rights reserved.
+#
+
+. $STF_SUITE/include/libtest.shlib
+
+#
+# DESCRIPTION:
+# Copy a large number of files between 2 directories
+# within a zfs filesystem works without errors.
+# This make sure zap upgrading and expanding works.
+#
+# STRATEGY:
+#
+# 1. Create NR_FILES files in directory src
+# 2. Check the number of files is correct
+# 3. Copy files from src to dst in readdir order
+# 4. Check the number of files is correct
+#
+
+verify_runnable "global"
+
+function cleanup
+{
+	rm -rf $TESTDIR/src $TESTDIR/dst
+}
+
+log_assert "Copy a large number of files between 2 directories" \
+	"within a zfs filesystem works without errors"
+
+log_onexit cleanup
+
+NR_FILES=60000
+BATCH=1000
+
+log_must mkdir $TESTDIR/src
+log_must mkdir $TESTDIR/dst
+
+WD=$(pwd)
+cd $TESTDIR/src
+# create NR_FILES in BATCH at a time to prevent overflowing argument buffer
+for i in $(seq $(($NR_FILES/$BATCH))); do touch $(seq $((($i-1)*$BATCH+1)) $(($i*$BATCH))); done
+cd $WD
+
+log_must test $NR_FILES -eq $(ls -U $TESTDIR/src | wc -l)
+
+# copy files from src to dst, use cp_files to make sure we copy in readdir order
+log_must $STF_SUITE/tests/functional/cp_files/cp_files $TESTDIR/src $TESTDIR/dst
+
+log_must test $NR_FILES -eq $(ls -U $TESTDIR/dst | wc -l)
+
+log_pass
diff --git a/tests/zfs-tests/tests/functional/cp_files/setup.ksh b/tests/zfs-tests/tests/functional/cp_files/setup.ksh
new file mode 100755
index 0000000..fc5cec3
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/cp_files/setup.ksh
@@ -0,0 +1,35 @@
+#!/bin/ksh -p
+#
+# CDDL HEADER START
+#
+# The contents of this file are subject to the terms of the
+# Common Development and Distribution License (the "License").
+# You may not use this file except in compliance with the License.
+#
+# You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+# or http://www.opensolaris.org/os/licensing.
+# See the License for the specific language governing permissions
+# and limitations under the License.
+#
+# When distributing Covered Code, include this CDDL HEADER in each
+# file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+# If applicable, add the following below this CDDL HEADER, with the
+# fields enclosed by brackets "[]" replaced with your own identifying
+# information: Portions Copyright [yyyy] [name of copyright owner]
+#
+# CDDL HEADER END
+#
+
+#
+# Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
+# Use is subject to license terms.
+#
+
+#
+# Copyright (c) 2013 by Delphix. All rights reserved.
+#
+
+. $STF_SUITE/include/libtest.shlib
+
+DISK=${DISKS%% *}
+default_setup $DISK