Multipath device manageability improvements

Update udev helper scripts to deal with device-mapper devices created
by multipathd.  These enhancements are targeted at a particular
storage network topology under evaluation at LLNL consisting of two
SAS switches providing redundant connectivity between multiple server
nodes and disk enclosures.

The key to making these systems manageable is to create shortnames for
each disk that conveys its physical location in a drawer.  In a
direct-attached topology we infer a disk's enclosure from the PCI bus
number and HBA port number in the by-path name provided by udev.  In a
switched topology, however, multiple drawers are accessed via a single
HBA port.  We therefore resort to assigning drawer identifiers based
on which switch port a drive's enclosure is connected to.  This
information is available from sysfs.

Add options to zpool_layout to generate an /etc/zfs/zdev.conf using
symbolic links in /dev/disk/by-id of the form
<label>-<UUID>-switch-port:<X>-slot:<Y>.  <label> is a string that
depends on the subsystem that created the link and defaults to
"dm-uuid-mpath" (this prefix is used by multipathd).  <UUID> is a
unique identifier for the disk typically obtained from the scsi_id
program, and <X> and <Y> denote the switch port and disk slot numbers,
respectively.

Add a callout script sas_switch_id for use by multipathd to help
create symlinks of the form described above.  Update zpool_id and the
udev zpool rules file to handle both multipath devices and
conventional drives.

3 files changed, 609 insertions, 0 deletions

diff --git a/cmd/sas_switch_id/Makefile.am b/cmd/sas_switch_id/Makefile.am
new file mode 100644
index 000000000..092766369
--- /dev/null
+++ b/cmd/sas_switch_id/Makefile.am
@@ -0,0 +1 @@
+dist_bin_SCRIPTS = sas_switch_id
diff --git a/cmd/sas_switch_id/Makefile.in b/cmd/sas_switch_id/Makefile.in
new file mode 100644
index 000000000..770277677
--- /dev/null
+++ b/cmd/sas_switch_id/Makefile.in
@@ -0,0 +1,512 @@
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+	dvi-am html html-am info info-am install install-am \
+	install-data install-data-am install-dist_binSCRIPTS \
+	install-dvi install-dvi-am install-exec install-exec-am \
+	install-html install-html-am install-info install-info-am \
+	install-man install-pdf install-pdf-am install-ps \
+	install-ps-am install-strip installcheck installcheck-am \
+	installdirs maintainer-clean maintainer-clean-generic \
+	mostlyclean mostlyclean-generic mostlyclean-libtool pdf pdf-am \
+	ps ps-am uninstall uninstall-am uninstall-dist_binSCRIPTS
+
+
+# Tell versions [3.59,3.63) of GNU make to not export all variables.
+# Otherwise a system limit (for SysV at least) may be exceeded.
+.NOEXPORT:
diff --git a/cmd/sas_switch_id/sas_switch_id b/cmd/sas_switch_id/sas_switch_id
new file mode 100755
index 000000000..ecaabc028
--- /dev/null
+++ b/cmd/sas_switch_id/sas_switch_id
@@ -0,0 +1,96 @@
+#!/bin/sh
+#
+# sas_switch_id
+#
+# Callout script for multipathd to obtain disk UUIDs.  Combine the UUID
+# from the scsi_id program with the SAS switch port number and enclosure
+# bay number, if available.  This naming convention enables easier
+# identification of the physical drive location when multiple disk
+# enclosures are accessed via a SAS switch.  For other storage
+# topologies just return the undecorated UUID of the drive.
+
+PHYS_PER_PORT=4
+DEV=
+
+usage() {
+        cat << EOF
+Usage: sas_switch_id [-d disk] [-p phys_per_port]
+  -d    Basename of the disk device [default=none]
+  -p    Number of PHYs per switch port [default=${PHYS_PER_PORT}]
+  -h    Show this message
+EOF
+        exit 0
+}
+
+while getopts 'd:p:h' OPTION; do
+        case ${OPTION} in
+        d)
+                DEV=${OPTARG}
+                ;;
+        p)
+                PHYS_PER_PORT=${OPTARG}
+                ;;
+        h)
+                usage
+                ;;
+        esac
+done
+
+if [ -z "$DEV" ] ; then
+	echo "Error: missing required option -d"
+	exit 1
+fi
+
+UUID=`/lib/udev/scsi_id --whitelisted --device=/dev/$DEV`
+if [ $? != 0 -o -z "$UUID" ] ; then
+	exit 1
+fi
+sys_path=`udevadm info -q path -p /sys/block/$DEV`
+dirs=(`echo "$sys_path" | tr / ' '`)
+switch_port_dir="/sys"
+
+# Get path up to /sys/.../hostX
+for (( i=0; i<${#dirs[*]}; i++ )); do
+	d=${dirs[$i]}
+	switch_port_dir=$switch_port_dir/$d
+	echo $d | egrep -q -e '^host[0-9]+$' && break
+done
+
+if [ $i = ${#dirs[*]} ] ; then
+	echo $UUID
+	exit 0
+fi
+
+# The directory three levels beneath /sys/.../hostX contains
+# symlinks to phy devices that reveal the switch port number.
+# Lowest phy number is $PHYS_PER_PORT*switch_port_number.
+for (( j=(($i+1)) ; j<(($i+4)); j++ )); do
+	switch_port_dir=$switch_port_dir/${dirs[$j]}
+done
+pushd $switch_port_dir > /dev/null
+PHY=`ls -d phy* 2>/dev/null | head -1 | awk -F: '{print $NF}'`
+PORT=$(( $PHY / $PHYS_PER_PORT ))
+popd > /dev/null
+if [ -z "$PHY" ] ; then
+	echo $UUID
+	exit 0
+fi
+
+# Look in /sys/.../sas_device/end_device-X for the bay_identifier
+# attribute.
+end_device_dir=$switch_port_dir
+for (( k=$j ; k<${#dirs[*]} ; k++ )); do
+	d=${dirs[$k]}
+	end_device_dir=$end_device_dir/$d
+	if echo $d | egrep -q -e '^end_device' ; then
+		end_device_dir=$end_device_dir/sas_device/$d
+		break
+	fi
+done
+SLOT=`cat $end_device_dir/bay_identifier 2>/dev/null`
+if [ -z "$SLOT" ] ; then
+	echo $UUID
+	exit 0
+fi
+
+echo "$UUID-switch-port:$PORT-slot:$SLOT"