Various ZED fixes

* Teach ZED to handle spares usingi the configured ashift: if the zpool
   'ashift' property is set then ZED should use its value when kicking
   in a hotspare; with this change 512e disks can be used as spares
   for VDEVs that were created with ashift=9, even if ZFS natively
   detects them as 4K block devices.

 * Introduce an additional auto_spare test case which verifies that in
   the face of multiple device failures an appropiate number of spares
   are kicked in.

 * Fix zed_stop() in "libtest.shlib" which did not correctly wait the
   target pid.

 * Fix ZED crashing on startup caused by a race condition in libzfs
   when used in multi-threaded context.

 * Convert ZED over to using the tpool library which is already present
   in the Illumos FMA code.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: loli10K <ezomori.nozomu@gmail.com>
Closes #2562 
Closes #6858

tests/zfs-tests/include/blkdev.shlib

@@ -353,16 +353,35 @@ function insert_disk #disk scsi_host
 
 #
 # Load scsi_debug module with specified parameters
+# $blksz can be either one of: < 512b | 512e | 4Kn >
 #
-function load_scsi_debug # dev_size_mb add_host num_tgts max_luns
+function load_scsi_debug # dev_size_mb add_host num_tgts max_luns blksz
 {
 	typeset devsize=$1
 	typeset hosts=$2
 	typeset tgts=$3
 	typeset luns=$4
+	typeset blksz=$5
 
 	[[ -z $devsize ]] || [[ -z $hosts ]] || [[ -z $tgts ]] || \
-	    [[ -z $luns ]] && log_fail "Arguments invalid or missing"
+	    [[ -z $luns ]] || [[ -z $blksz ]] && \
+	    log_fail "Arguments invalid or missing"
+
+	case "$5" in
+		'512b')
+			typeset sector=512
+			typeset blkexp=0
+		;;
+		'512e')
+			typeset sector=512
+			typeset blkexp=3
+		;;
+		'4Kn')
+			typeset sector=4096
+			typeset blkexp=0
+		;;
+		*) log_fail "Unsupported blksz value: $5" ;;
+	esac
 
 	if is_linux; then
 		modprobe -n scsi_debug
@@ -375,7 +394,8 @@ function load_scsi_debug # dev_size_mb add_host num_tgts max_luns
 			log_fail "scsi_debug module already installed"
 		else
 			log_must modprobe scsi_debug dev_size_mb=$devsize \
-			    add_host=$hosts num_tgts=$tgts max_luns=$luns
+			    add_host=$hosts num_tgts=$tgts max_luns=$luns \
+			    sector_size=$sector physblk_exp=$blkexp
 			block_device_wait
 			lsscsi | egrep scsi_debug > /dev/null
 			if (($? == 1)); then
@@ -385,6 +405,16 @@ function load_scsi_debug # dev_size_mb add_host num_tgts max_luns
 	fi
 }
 
+#
+# Unload scsi_debug module, if needed.
+#
+function unload_scsi_debug
+{
+	if lsmod | grep scsi_debug >/dev/null; then
+		log_must modprobe -r scsi_debug
+	fi
+}
+
 #
 # Get scsi_debug device name.
 # Returns basename of scsi_debug device (for example "sdb").

tests/zfs-tests/include/libtest.shlib

@@ -3158,13 +3158,25 @@ function zed_stop
 	if [[ -f ${ZEDLET_DIR}/zed.pid ]]; then
 		zedpid=$(cat ${ZEDLET_DIR}/zed.pid)
 		kill $zedpid
-		wait $zedpid
+		while ps -p $zedpid > /dev/null; do
+			sleep 1
+		done
 		rm -f ${ZEDLET_DIR}/zed.pid
 	fi
-
 	return 0
 }
 
+#
+# Drain all zevents
+#
+function zed_events_drain
+{
+	while [ $(zpool events -H | wc -l) -ne 0 ]; do
+		sleep 1
+		zpool events -c >/dev/null
+	done
+}
+
 #
 # Check is provided device is being active used as a swap device.
 #