Add -c to zpool iostat & status to run command

This patch adds a command (-c) option to zpool status and zpool iostat.  The
-c option allows you to run an arbitrary command on each vdev and display
the first line of output in zpool status/iostat.  The environment vars
VDEV_PATH and VDEV_UPATH are set to the vdev's path and "underlying path"
before running the command.  For device mapper, multipath, or partitioned
vdevs, VDEV_UPATH is the actual underlying /dev/sd* disk.  This can be useful
if the command you're running requires a /dev/sd* device.

The patch also uses /sys/block/<dev>/slaves/ to lookup the underlying device
instead of using libdevmapper.  This not only removes the libdevmapper
requirement at build time, but also allows you to resolve device mapper
devices without being root.  This means that UDEV_UPATH get set correctly
when running zpool status/iostat as an unprivileged user.

Example:

$ zpool status -c 'echo I am $VDEV_PATH, $VDEV_UPATH'

NAME        STATE     READ WRITE CKSUM
mypool      ONLINE       0     0     0
  mirror-0  ONLINE       0     0     0
    mpatha  ONLINE       0     0     0  I am /dev/mapper/mpatha, /dev/sdc
    sdb     ONLINE       0     0     0  I am /dev/sdb1, /dev/sdb

Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tony Hutter <hutter2@llnl.gov>
Closes #5368

tests/zfs-tests/tests/functional/cli_user/misc/zpool_status_001_neg.ksh

@@ -69,6 +69,21 @@ check_pool_status
 log_must eval "$ZPOOL status -v $TESTPOOL > /tmp/pool-status.$$"
 check_pool_status
 
+# Make sure -c option works, and that VDEV_PATH and VDEV_UPATH get set.
+#
+# grep for '^\s+/' to just get the vdevs (not pools).  All vdevs will start with
+# a '/' when we specify the path (-P) flag. We check for "{}" to see if one
+# of the VDEV variables isn't set.
+C1=$($ZPOOL status -P | $GREP -E '^\s+/' | $WC -l)
+C2=$($ZPOOL status -P -c 'echo vdev_test{$VDEV_PATH}{$VDEV_UPATH}' | \
+    $GREP -E '^\s+/' | $GREP -v '{}' | $WC -l)
+
+if [ "$C1" != "$C2" ] ; then
+	log_fail "zpool status -c option failed.  Expected $C1 vdevs, got $C2"
+else
+	log_pass "zpool status -c option passed.  Expected $C1 vdevs, got $C2"
+fi
+
 # $TESTPOOL.virt has an offline device, so -x will show it
 log_must eval "$ZPOOL status -x $TESTPOOL.virt > /tmp/pool-status.$$"
 check_pool_status

tests/zfs-tests/tests/functional/cli_user/zpool_iostat/Makefile.am

@@ -5,4 +5,5 @@ dist_pkgdata_SCRIPTS = \
 	zpool_iostat_001_neg.ksh \
 	zpool_iostat_002_pos.ksh \
 	zpool_iostat_003_neg.ksh \
-	zpool_iostat_004_pos.ksh
+	zpool_iostat_004_pos.ksh \
+	zpool_iostat_005_pos.ksh

tests/zfs-tests/tests/functional/cli_user/zpool_iostat/zpool_iostat_005_pos.ksh

@@ -0,0 +1,63 @@
+#!/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.
+#
+
+#
+# Copyright (c) 2016 by Lawrence Livermore National Security, LLC.
+#
+
+
+. $STF_SUITE/include/libtest.shlib
+
+verify_runnable "both"
+
+typeset testpool
+if is_global_zone ; then
+	testpool=$TESTPOOL
+else
+	testpool=${TESTPOOL%%/*}
+fi
+
+#
+# DESCRIPTION:
+# Verify 'zpool iostat -c CMD' works, and that VDEV_PATH and VDEV_UPATH get set.
+#
+# STRATEGY:
+# grep for '^\s+/' to just get the vdevs (not pools).  All vdevs will start with
+# a '/' when we specify the path (-P) flag. We check for "{}" to see if one
+# of the VDEV variables isn't set.
+#
+C1=$($ZPOOL iostat -Pv | $GREP -E '^\s+/' | $WC -l)
+C2=$($ZPOOL iostat -Pv -c 'echo vdev_test{$VDEV_PATH}{$VDEV_UPATH}' | $GREP -E '^\s+/' | $GREP -v '{}' | $WC -l)
+if [ "$C1" != "$C2" ] ; then
+	log_fail "zpool iostat -c failed, expected $C1 vdevs, got $C2"
+else
+	log_pass "zpool iostat -c passed, expected $C1 vdevs, got $C2"
+fi