diff options
Diffstat (limited to 'Documentation/target')
| -rw-r--r-- | Documentation/target/index.rst | 19 | ||||
| -rw-r--r-- | Documentation/target/scripts.rst | 11 | ||||
| -rwxr-xr-x | Documentation/target/target-export-device | 80 | ||||
| -rwxr-xr-x | Documentation/target/tcm_mod_builder.py | 656 | ||||
| -rw-r--r-- | Documentation/target/tcm_mod_builder.rst | 149 | ||||
| -rw-r--r-- | Documentation/target/tcmu-design.rst | 405 |
6 files changed, 1320 insertions, 0 deletions
diff --git a/Documentation/target/index.rst b/Documentation/target/index.rst new file mode 100644 index 000000000..4b24f81f7 --- /dev/null +++ b/Documentation/target/index.rst @@ -0,0 +1,19 @@ +.. SPDX-License-Identifier: GPL-2.0 + +================== +TCM Virtual Device +================== + +.. toctree:: + :maxdepth: 1 + + tcmu-design + tcm_mod_builder + scripts + +.. only:: subproject and html + + Indices + ======= + + * :ref:`genindex` diff --git a/Documentation/target/scripts.rst b/Documentation/target/scripts.rst new file mode 100644 index 000000000..172d42b52 --- /dev/null +++ b/Documentation/target/scripts.rst @@ -0,0 +1,11 @@ +TCM mod builder script +---------------------- + +.. literalinclude:: tcm_mod_builder.py + :language: perl + +Target export device script +--------------------------- + +.. literalinclude:: target-export-device + :language: shell diff --git a/Documentation/target/target-export-device b/Documentation/target/target-export-device new file mode 100755 index 000000000..b803f4f88 --- /dev/null +++ b/Documentation/target/target-export-device @@ -0,0 +1,80 @@ +#!/bin/sh +# +# This script illustrates the sequence of operations in configfs to +# create a very simple LIO iSCSI target with a file or block device +# backstore. +# +# (C) Copyright 2014 Christophe Vu-Brugier <cvubrugier@fastmail.fm> +# + +print_usage() { + cat <<EOF +Usage: $(basename $0) [-p PORTAL] DEVICE|FILE +Export a block device or a file as an iSCSI target with a single LUN +EOF +} + +die() { + echo $1 + exit 1 +} + +while getopts "hp:" arg; do + case $arg in + h) print_usage; exit 0;; + p) PORTAL=${OPTARG};; + esac +done +shift $(($OPTIND - 1)) + +DEVICE=$1 +[ -n "$DEVICE" ] || die "Missing device or file argument" +[ -b $DEVICE -o -f $DEVICE ] || die "Invalid device or file: ${DEVICE}" +IQN="iqn.2003-01.org.linux-iscsi.$(hostname):$(basename $DEVICE)" +[ -n "$PORTAL" ] || PORTAL="0.0.0.0:3260" + +CONFIGFS=/sys/kernel/config +CORE_DIR=$CONFIGFS/target/core +ISCSI_DIR=$CONFIGFS/target/iscsi + +# Load the target modules and mount the config file system +lsmod | grep -q configfs || modprobe configfs +lsmod | grep -q target_core_mod || modprobe target_core_mod +mount | grep -q ^configfs || mount -t configfs none $CONFIGFS +mkdir -p $ISCSI_DIR + +# Create a backstore +if [ -b $DEVICE ]; then + BACKSTORE_DIR=$CORE_DIR/iblock_0/data + mkdir -p $BACKSTORE_DIR + echo "udev_path=${DEVICE}" > $BACKSTORE_DIR/control +else + BACKSTORE_DIR=$CORE_DIR/fileio_0/data + mkdir -p $BACKSTORE_DIR + DEVICE_SIZE=$(du -b $DEVICE | cut -f1) + echo "fd_dev_name=${DEVICE}" > $BACKSTORE_DIR/control + echo "fd_dev_size=${DEVICE_SIZE}" > $BACKSTORE_DIR/control + echo 1 > $BACKSTORE_DIR/attrib/emulate_write_cache +fi +echo 1 > $BACKSTORE_DIR/enable + +# Create an iSCSI target and a target portal group (TPG) +mkdir $ISCSI_DIR/$IQN +mkdir $ISCSI_DIR/$IQN/tpgt_1/ + +# Create a LUN +mkdir $ISCSI_DIR/$IQN/tpgt_1/lun/lun_0 +ln -s $BACKSTORE_DIR $ISCSI_DIR/$IQN/tpgt_1/lun/lun_0/data +echo 1 > $ISCSI_DIR/$IQN/tpgt_1/enable + +# Create a network portal +mkdir $ISCSI_DIR/$IQN/tpgt_1/np/$PORTAL + +# Disable authentication +echo 0 > $ISCSI_DIR/$IQN/tpgt_1/attrib/authentication +echo 1 > $ISCSI_DIR/$IQN/tpgt_1/attrib/generate_node_acls + +# Allow write access for non authenticated initiators +echo 0 > $ISCSI_DIR/$IQN/tpgt_1/attrib/demo_mode_write_protect + +echo "Target ${IQN}, portal ${PORTAL} has been created" diff --git a/Documentation/target/tcm_mod_builder.py b/Documentation/target/tcm_mod_builder.py new file mode 100755 index 000000000..54492aa81 --- /dev/null +++ b/Documentation/target/tcm_mod_builder.py @@ -0,0 +1,656 @@ +#!/usr/bin/env python +# The TCM v4 multi-protocol fabric module generation script for drivers/target/$NEW_MOD +# +# Copyright (c) 2010 Rising Tide Systems +# Copyright (c) 2010 Linux-iSCSI.org +# +# Author: nab@kernel.org +# +import os, sys +import subprocess as sub +import string +import re +import optparse + +tcm_dir = "" + +fabric_ops = [] +fabric_mod_dir = "" +fabric_mod_port = "" +fabric_mod_init_port = "" + +def tcm_mod_err(msg): + print msg + sys.exit(1) + +def tcm_mod_create_module_subdir(fabric_mod_dir_var): + + if os.path.isdir(fabric_mod_dir_var) == True: + return 1 + + print "Creating fabric_mod_dir: " + fabric_mod_dir_var + ret = os.mkdir(fabric_mod_dir_var) + if ret: + tcm_mod_err("Unable to mkdir " + fabric_mod_dir_var) + + return + +def tcm_mod_build_FC_include(fabric_mod_dir_var, fabric_mod_name): + global fabric_mod_port + global fabric_mod_init_port + buf = "" + + f = fabric_mod_dir_var + "/" + fabric_mod_name + "_base.h" + print "Writing file: " + f + + p = open(f, 'w'); + if not p: + tcm_mod_err("Unable to open file: " + f) + + buf = "#define " + fabric_mod_name.upper() + "_VERSION \"v0.1\"\n" + buf += "#define " + fabric_mod_name.upper() + "_NAMELEN 32\n" + buf += "\n" + buf += "struct " + fabric_mod_name + "_tpg {\n" + buf += " /* FC lport target portal group tag for TCM */\n" + buf += " u16 lport_tpgt;\n" + buf += " /* Pointer back to " + fabric_mod_name + "_lport */\n" + buf += " struct " + fabric_mod_name + "_lport *lport;\n" + buf += " /* Returned by " + fabric_mod_name + "_make_tpg() */\n" + buf += " struct se_portal_group se_tpg;\n" + buf += "};\n" + buf += "\n" + buf += "struct " + fabric_mod_name + "_lport {\n" + buf += " /* Binary World Wide unique Port Name for FC Target Lport */\n" + buf += " u64 lport_wwpn;\n" + buf += " /* ASCII formatted WWPN for FC Target Lport */\n" + buf += " char lport_name[" + fabric_mod_name.upper() + "_NAMELEN];\n" + buf += " /* Returned by " + fabric_mod_name + "_make_lport() */\n" + buf += " struct se_wwn lport_wwn;\n" + buf += "};\n" + + ret = p.write(buf) + if ret: + tcm_mod_err("Unable to write f: " + f) + + p.close() + + fabric_mod_port = "lport" + fabric_mod_init_port = "nport" + + return + +def tcm_mod_build_SAS_include(fabric_mod_dir_var, fabric_mod_name): + global fabric_mod_port + global fabric_mod_init_port + buf = "" + + f = fabric_mod_dir_var + "/" + fabric_mod_name + "_base.h" + print "Writing file: " + f + + p = open(f, 'w'); + if not p: + tcm_mod_err("Unable to open file: " + f) + + buf = "#define " + fabric_mod_name.upper() + "_VERSION \"v0.1\"\n" + buf += "#define " + fabric_mod_name.upper() + "_NAMELEN 32\n" + buf += "\n" + buf += "struct " + fabric_mod_name + "_tpg {\n" + buf += " /* SAS port target portal group tag for TCM */\n" + buf += " u16 tport_tpgt;\n" + buf += " /* Pointer back to " + fabric_mod_name + "_tport */\n" + buf += " struct " + fabric_mod_name + "_tport *tport;\n" + buf += " /* Returned by " + fabric_mod_name + "_make_tpg() */\n" + buf += " struct se_portal_group se_tpg;\n" + buf += "};\n\n" + buf += "struct " + fabric_mod_name + "_tport {\n" + buf += " /* Binary World Wide unique Port Name for SAS Target port */\n" + buf += " u64 tport_wwpn;\n" + buf += " /* ASCII formatted WWPN for SAS Target port */\n" + buf += " char tport_name[" + fabric_mod_name.upper() + "_NAMELEN];\n" + buf += " /* Returned by " + fabric_mod_name + "_make_tport() */\n" + buf += " struct se_wwn tport_wwn;\n" + buf += "};\n" + + ret = p.write(buf) + if ret: + tcm_mod_err("Unable to write f: " + f) + + p.close() + + fabric_mod_port = "tport" + fabric_mod_init_port = "iport" + + return + +def tcm_mod_build_iSCSI_include(fabric_mod_dir_var, fabric_mod_name): + global fabric_mod_port + global fabric_mod_init_port + buf = "" + + f = fabric_mod_dir_var + "/" + fabric_mod_name + "_base.h" + print "Writing file: " + f + + p = open(f, 'w'); + if not p: + tcm_mod_err("Unable to open file: " + f) + + buf = "#define " + fabric_mod_name.upper() + "_VERSION \"v0.1\"\n" + buf += "#define " + fabric_mod_name.upper() + "_NAMELEN 32\n" + buf += "\n" + buf += "struct " + fabric_mod_name + "_tpg {\n" + buf += " /* iSCSI target portal group tag for TCM */\n" + buf += " u16 tport_tpgt;\n" + buf += " /* Pointer back to " + fabric_mod_name + "_tport */\n" + buf += " struct " + fabric_mod_name + "_tport *tport;\n" + buf += " /* Returned by " + fabric_mod_name + "_make_tpg() */\n" + buf += " struct se_portal_group se_tpg;\n" + buf += "};\n\n" + buf += "struct " + fabric_mod_name + "_tport {\n" + buf += " /* ASCII formatted TargetName for IQN */\n" + buf += " char tport_name[" + fabric_mod_name.upper() + "_NAMELEN];\n" + buf += " /* Returned by " + fabric_mod_name + "_make_tport() */\n" + buf += " struct se_wwn tport_wwn;\n" + buf += "};\n" + + ret = p.write(buf) + if ret: + tcm_mod_err("Unable to write f: " + f) + + p.close() + + fabric_mod_port = "tport" + fabric_mod_init_port = "iport" + + return + +def tcm_mod_build_base_includes(proto_ident, fabric_mod_dir_val, fabric_mod_name): + + if proto_ident == "FC": + tcm_mod_build_FC_include(fabric_mod_dir_val, fabric_mod_name) + elif proto_ident == "SAS": + tcm_mod_build_SAS_include(fabric_mod_dir_val, fabric_mod_name) + elif proto_ident == "iSCSI": + tcm_mod_build_iSCSI_include(fabric_mod_dir_val, fabric_mod_name) + else: + print "Unsupported proto_ident: " + proto_ident + sys.exit(1) + + return + +def tcm_mod_build_configfs(proto_ident, fabric_mod_dir_var, fabric_mod_name): + buf = "" + + f = fabric_mod_dir_var + "/" + fabric_mod_name + "_configfs.c" + print "Writing file: " + f + + p = open(f, 'w'); + if not p: + tcm_mod_err("Unable to open file: " + f) + + buf = "#include <linux/module.h>\n" + buf += "#include <linux/moduleparam.h>\n" + buf += "#include <linux/version.h>\n" + buf += "#include <generated/utsrelease.h>\n" + buf += "#include <linux/utsname.h>\n" + buf += "#include <linux/init.h>\n" + buf += "#include <linux/slab.h>\n" + buf += "#include <linux/kthread.h>\n" + buf += "#include <linux/types.h>\n" + buf += "#include <linux/string.h>\n" + buf += "#include <linux/configfs.h>\n" + buf += "#include <linux/ctype.h>\n" + buf += "#include <asm/unaligned.h>\n" + buf += "#include <scsi/scsi_proto.h>\n\n" + buf += "#include <target/target_core_base.h>\n" + buf += "#include <target/target_core_fabric.h>\n" + buf += "#include \"" + fabric_mod_name + "_base.h\"\n" + buf += "#include \"" + fabric_mod_name + "_fabric.h\"\n\n" + + buf += "static const struct target_core_fabric_ops " + fabric_mod_name + "_ops;\n\n" + + buf += "static struct se_portal_group *" + fabric_mod_name + "_make_tpg(\n" + buf += " struct se_wwn *wwn,\n" + buf += " struct config_group *group,\n" + buf += " const char *name)\n" + buf += "{\n" + buf += " struct " + fabric_mod_name + "_" + fabric_mod_port + "*" + fabric_mod_port + " = container_of(wwn,\n" + buf += " struct " + fabric_mod_name + "_" + fabric_mod_port + ", " + fabric_mod_port + "_wwn);\n\n" + buf += " struct " + fabric_mod_name + "_tpg *tpg;\n" + buf += " unsigned long tpgt;\n" + buf += " int ret;\n\n" + buf += " if (strstr(name, \"tpgt_\") != name)\n" + buf += " return ERR_PTR(-EINVAL);\n" + buf += " if (kstrtoul(name + 5, 10, &tpgt) || tpgt > UINT_MAX)\n" + buf += " return ERR_PTR(-EINVAL);\n\n" + buf += " tpg = kzalloc(sizeof(struct " + fabric_mod_name + "_tpg), GFP_KERNEL);\n" + buf += " if (!tpg) {\n" + buf += " printk(KERN_ERR \"Unable to allocate struct " + fabric_mod_name + "_tpg\");\n" + buf += " return ERR_PTR(-ENOMEM);\n" + buf += " }\n" + buf += " tpg->" + fabric_mod_port + " = " + fabric_mod_port + ";\n" + buf += " tpg->" + fabric_mod_port + "_tpgt = tpgt;\n\n" + + if proto_ident == "FC": + buf += " ret = core_tpg_register(wwn, &tpg->se_tpg, SCSI_PROTOCOL_FCP);\n" + elif proto_ident == "SAS": + buf += " ret = core_tpg_register(wwn, &tpg->se_tpg, SCSI_PROTOCOL_SAS);\n" + elif proto_ident == "iSCSI": + buf += " ret = core_tpg_register(wwn, &tpg->se_tpg, SCSI_PROTOCOL_ISCSI);\n" + + buf += " if (ret < 0) {\n" + buf += " kfree(tpg);\n" + buf += " return NULL;\n" + buf += " }\n" + buf += " return &tpg->se_tpg;\n" + buf += "}\n\n" + buf += "static void " + fabric_mod_name + "_drop_tpg(struct se_portal_group *se_tpg)\n" + buf += "{\n" + buf += " struct " + fabric_mod_name + "_tpg *tpg = container_of(se_tpg,\n" + buf += " struct " + fabric_mod_name + "_tpg, se_tpg);\n\n" + buf += " core_tpg_deregister(se_tpg);\n" + buf += " kfree(tpg);\n" + buf += "}\n\n" + + buf += "static struct se_wwn *" + fabric_mod_name + "_make_" + fabric_mod_port + "(\n" + buf += " struct target_fabric_configfs *tf,\n" + buf += " struct config_group *group,\n" + buf += " const char *name)\n" + buf += "{\n" + buf += " struct " + fabric_mod_name + "_" + fabric_mod_port + " *" + fabric_mod_port + ";\n" + + if proto_ident == "FC" or proto_ident == "SAS": + buf += " u64 wwpn = 0;\n\n" + + buf += " /* if (" + fabric_mod_name + "_parse_wwn(name, &wwpn, 1) < 0)\n" + buf += " return ERR_PTR(-EINVAL); */\n\n" + buf += " " + fabric_mod_port + " = kzalloc(sizeof(struct " + fabric_mod_name + "_" + fabric_mod_port + "), GFP_KERNEL);\n" + buf += " if (!" + fabric_mod_port + ") {\n" + buf += " printk(KERN_ERR \"Unable to allocate struct " + fabric_mod_name + "_" + fabric_mod_port + "\");\n" + buf += " return ERR_PTR(-ENOMEM);\n" + buf += " }\n" + + if proto_ident == "FC" or proto_ident == "SAS": + buf += " " + fabric_mod_port + "->" + fabric_mod_port + "_wwpn = wwpn;\n" + + buf += " /* " + fabric_mod_name + "_format_wwn(&" + fabric_mod_port + "->" + fabric_mod_port + "_name[0], " + fabric_mod_name.upper() + "_NAMELEN, wwpn); */\n\n" + buf += " return &" + fabric_mod_port + "->" + fabric_mod_port + "_wwn;\n" + buf += "}\n\n" + buf += "static void " + fabric_mod_name + "_drop_" + fabric_mod_port + "(struct se_wwn *wwn)\n" + buf += "{\n" + buf += " struct " + fabric_mod_name + "_" + fabric_mod_port + " *" + fabric_mod_port + " = container_of(wwn,\n" + buf += " struct " + fabric_mod_name + "_" + fabric_mod_port + ", " + fabric_mod_port + "_wwn);\n" + buf += " kfree(" + fabric_mod_port + ");\n" + buf += "}\n\n" + + buf += "static const struct target_core_fabric_ops " + fabric_mod_name + "_ops = {\n" + buf += " .module = THIS_MODULE,\n" + buf += " .name = \"" + fabric_mod_name + "\",\n" + buf += " .get_fabric_name = " + fabric_mod_name + "_get_fabric_name,\n" + buf += " .tpg_get_wwn = " + fabric_mod_name + "_get_fabric_wwn,\n" + buf += " .tpg_get_tag = " + fabric_mod_name + "_get_tag,\n" + buf += " .tpg_check_demo_mode = " + fabric_mod_name + "_check_false,\n" + buf += " .tpg_check_demo_mode_cache = " + fabric_mod_name + "_check_true,\n" + buf += " .tpg_check_demo_mode_write_protect = " + fabric_mod_name + "_check_true,\n" + buf += " .tpg_check_prod_mode_write_protect = " + fabric_mod_name + "_check_false,\n" + buf += " .tpg_get_inst_index = " + fabric_mod_name + "_tpg_get_inst_index,\n" + buf += " .release_cmd = " + fabric_mod_name + "_release_cmd,\n" + buf += " .sess_get_index = " + fabric_mod_name + "_sess_get_index,\n" + buf += " .sess_get_initiator_sid = NULL,\n" + buf += " .write_pending = " + fabric_mod_name + "_write_pending,\n" + buf += " .set_default_node_attributes = " + fabric_mod_name + "_set_default_node_attrs,\n" + buf += " .get_cmd_state = " + fabric_mod_name + "_get_cmd_state,\n" + buf += " .queue_data_in = " + fabric_mod_name + "_queue_data_in,\n" + buf += " .queue_status = " + fabric_mod_name + "_queue_status,\n" + buf += " .queue_tm_rsp = " + fabric_mod_name + "_queue_tm_rsp,\n" + buf += " .aborted_task = " + fabric_mod_name + "_aborted_task,\n" + buf += " /*\n" + buf += " * Setup function pointers for generic logic in target_core_fabric_configfs.c\n" + buf += " */\n" + buf += " .fabric_make_wwn = " + fabric_mod_name + "_make_" + fabric_mod_port + ",\n" + buf += " .fabric_drop_wwn = " + fabric_mod_name + "_drop_" + fabric_mod_port + ",\n" + buf += " .fabric_make_tpg = " + fabric_mod_name + "_make_tpg,\n" + buf += " .fabric_drop_tpg = " + fabric_mod_name + "_drop_tpg,\n" + buf += "};\n\n" + + buf += "static int __init " + fabric_mod_name + "_init(void)\n" + buf += "{\n" + buf += " return target_register_template(&" + fabric_mod_name + "_ops);\n" + buf += "};\n\n" + + buf += "static void __exit " + fabric_mod_name + "_exit(void)\n" + buf += "{\n" + buf += " target_unregister_template(&" + fabric_mod_name + "_ops);\n" + buf += "};\n\n" + + buf += "MODULE_DESCRIPTION(\"" + fabric_mod_name.upper() + " series fabric driver\");\n" + buf += "MODULE_LICENSE(\"GPL\");\n" + buf += "module_init(" + fabric_mod_name + "_init);\n" + buf += "module_exit(" + fabric_mod_name + "_exit);\n" + + ret = p.write(buf) + if ret: + tcm_mod_err("Unable to write f: " + f) + + p.close() + + return + +def tcm_mod_scan_fabric_ops(tcm_dir): + + fabric_ops_api = tcm_dir + "include/target/target_core_fabric.h" + + print "Using tcm_mod_scan_fabric_ops: " + fabric_ops_api + process_fo = 0; + + p = open(fabric_ops_api, 'r') + + line = p.readline() + while line: + if process_fo == 0 and re.search('struct target_core_fabric_ops {', line): + line = p.readline() + continue + + if process_fo == 0: + process_fo = 1; + line = p.readline() + # Search for function pointer + if not re.search('\(\*', line): + continue + + fabric_ops.append(line.rstrip()) + continue + + line = p.readline() + # Search for function pointer + if not re.search('\(\*', line): + continue + + fabric_ops.append(line.rstrip()) + + p.close() + return + +def tcm_mod_dump_fabric_ops(proto_ident, fabric_mod_dir_var, fabric_mod_name): + buf = "" + bufi = "" + + f = fabric_mod_dir_var + "/" + fabric_mod_name + "_fabric.c" + print "Writing file: " + f + + p = open(f, 'w') + if not p: + tcm_mod_err("Unable to open file: " + f) + + fi = fabric_mod_dir_var + "/" + fabric_mod_name + "_fabric.h" + print "Writing file: " + fi + + pi = open(fi, 'w') + if not pi: + tcm_mod_err("Unable to open file: " + fi) + + buf = "#include <linux/slab.h>\n" + buf += "#include <linux/kthread.h>\n" + buf += "#include <linux/types.h>\n" + buf += "#include <linux/list.h>\n" + buf += "#include <linux/types.h>\n" + buf += "#include <linux/string.h>\n" + buf += "#include <linux/ctype.h>\n" + buf += "#include <asm/unaligned.h>\n" + buf += "#include <scsi/scsi_common.h>\n" + buf += "#include <scsi/scsi_proto.h>\n" + buf += "#include <target/target_core_base.h>\n" + buf += "#include <target/target_core_fabric.h>\n" + buf += "#include \"" + fabric_mod_name + "_base.h\"\n" + buf += "#include \"" + fabric_mod_name + "_fabric.h\"\n\n" + + buf += "int " + fabric_mod_name + "_check_true(struct se_portal_group *se_tpg)\n" + buf += "{\n" + buf += " return 1;\n" + buf += "}\n\n" + bufi += "int " + fabric_mod_name + "_check_true(struct se_portal_group *);\n" + + buf += "int " + fabric_mod_name + "_check_false(struct se_portal_group *se_tpg)\n" + buf += "{\n" + buf += " return 0;\n" + buf += "}\n\n" + bufi += "int " + fabric_mod_name + "_check_false(struct se_portal_group *);\n" + + total_fabric_ops = len(fabric_ops) + i = 0 + + while i < total_fabric_ops: + fo = fabric_ops[i] + i += 1 +# print "fabric_ops: " + fo + + if re.search('get_fabric_name', fo): + buf += "char *" + fabric_mod_name + "_get_fabric_name(void)\n" + buf += "{\n" + buf += " return \"" + fabric_mod_name + "\";\n" + buf += "}\n\n" + bufi += "char *" + fabric_mod_name + "_get_fabric_name(void);\n" + continue + + if re.search('get_wwn', fo): + buf += "char *" + fabric_mod_name + "_get_fabric_wwn(struct se_portal_group *se_tpg)\n" + buf += "{\n" + buf += " struct " + fabric_mod_name + "_tpg *tpg = container_of(se_tpg,\n" + buf += " struct " + fabric_mod_name + "_tpg, se_tpg);\n" + buf += " struct " + fabric_mod_name + "_" + fabric_mod_port + " *" + fabric_mod_port + " = tpg->" + fabric_mod_port + ";\n\n" + buf += " return &" + fabric_mod_port + "->" + fabric_mod_port + "_name[0];\n" + buf += "}\n\n" + bufi += "char *" + fabric_mod_name + "_get_fabric_wwn(struct se_portal_group *);\n" + + if re.search('get_tag', fo): + buf += "u16 " + fabric_mod_name + "_get_tag(struct se_portal_group *se_tpg)\n" + buf += "{\n" + buf += " struct " + fabric_mod_name + "_tpg *tpg = container_of(se_tpg,\n" + buf += " struct " + fabric_mod_name + "_tpg, se_tpg);\n" + buf += " return tpg->" + fabric_mod_port + "_tpgt;\n" + buf += "}\n\n" + bufi += "u16 " + fabric_mod_name + "_get_tag(struct se_portal_group *);\n" + + if re.search('tpg_get_inst_index\)\(', fo): + buf += "u32 " + fabric_mod_name + "_tpg_get_inst_index(struct se_portal_group *se_tpg)\n" + buf += "{\n" + buf += " return 1;\n" + buf += "}\n\n" + bufi += "u32 " + fabric_mod_name + "_tpg_get_inst_index(struct se_portal_group *);\n" + + if re.search('\*release_cmd\)\(', fo): + buf += "void " + fabric_mod_name + "_release_cmd(struct se_cmd *se_cmd)\n" + buf += "{\n" + buf += " return;\n" + buf += "}\n\n" + bufi += "void " + fabric_mod_name + "_release_cmd(struct se_cmd *);\n" + + if re.search('sess_get_index\)\(', fo): + buf += "u32 " + fabric_mod_name + "_sess_get_index(struct se_session *se_sess)\n" + buf += "{\n" + buf += " return 0;\n" + buf += "}\n\n" + bufi += "u32 " + fabric_mod_name + "_sess_get_index(struct se_session *);\n" + + if re.search('write_pending\)\(', fo): + buf += "int " + fabric_mod_name + "_write_pending(struct se_cmd *se_cmd)\n" + buf += "{\n" + buf += " return 0;\n" + buf += "}\n\n" + bufi += "int " + fabric_mod_name + "_write_pending(struct se_cmd *);\n" + + if re.search('set_default_node_attributes\)\(', fo): + buf += "void " + fabric_mod_name + "_set_default_node_attrs(struct se_node_acl *nacl)\n" + buf += "{\n" + buf += " return;\n" + buf += "}\n\n" + bufi += "void " + fabric_mod_name + "_set_default_node_attrs(struct se_node_acl *);\n" + + if re.search('get_cmd_state\)\(', fo): + buf += "int " + fabric_mod_name + "_get_cmd_state(struct se_cmd *se_cmd)\n" + buf += "{\n" + buf += " return 0;\n" + buf += "}\n\n" + bufi += "int " + fabric_mod_name + "_get_cmd_state(struct se_cmd *);\n" + + if re.search('queue_data_in\)\(', fo): + buf += "int " + fabric_mod_name + "_queue_data_in(struct se_cmd *se_cmd)\n" + buf += "{\n" + buf += " return 0;\n" + buf += "}\n\n" + bufi += "int " + fabric_mod_name + "_queue_data_in(struct se_cmd *);\n" + + if re.search('queue_status\)\(', fo): + buf += "int " + fabric_mod_name + "_queue_status(struct se_cmd *se_cmd)\n" + buf += "{\n" + buf += " return 0;\n" + buf += "}\n\n" + bufi += "int " + fabric_mod_name + "_queue_status(struct se_cmd *);\n" + + if re.search('queue_tm_rsp\)\(', fo): + buf += "void " + fabric_mod_name + "_queue_tm_rsp(struct se_cmd *se_cmd)\n" + buf += "{\n" + buf += " return;\n" + buf += "}\n\n" + bufi += "void " + fabric_mod_name + "_queue_tm_rsp(struct se_cmd *);\n" + + if re.search('aborted_task\)\(', fo): + buf += "void " + fabric_mod_name + "_aborted_task(struct se_cmd *se_cmd)\n" + buf += "{\n" + buf += " return;\n" + buf += "}\n\n" + bufi += "void " + fabric_mod_name + "_aborted_task(struct se_cmd *);\n" + + ret = p.write(buf) + if ret: + tcm_mod_err("Unable to write f: " + f) + + p.close() + + ret = pi.write(bufi) + if ret: + tcm_mod_err("Unable to write fi: " + fi) + + pi.close() + return + +def tcm_mod_build_kbuild(fabric_mod_dir_var, fabric_mod_name): + + buf = "" + f = fabric_mod_dir_var + "/Makefile" + print "Writing file: " + f + + p = open(f, 'w') + if not p: + tcm_mod_err("Unable to open file: " + f) + + buf += fabric_mod_name + "-objs := " + fabric_mod_name + "_fabric.o \\\n" + buf += " " + fabric_mod_name + "_configfs.o\n" + buf += "obj-$(CONFIG_" + fabric_mod_name.upper() + ") += " + fabric_mod_name + ".o\n" + + ret = p.write(buf) + if ret: + tcm_mod_err("Unable to write f: " + f) + + p.close() + return + +def tcm_mod_build_kconfig(fabric_mod_dir_var, fabric_mod_name): + + buf = "" + f = fabric_mod_dir_var + "/Kconfig" + print "Writing file: " + f + + p = open(f, 'w') + if not p: + tcm_mod_err("Unable to open file: " + f) + + buf = "config " + fabric_mod_name.upper() + "\n" + buf += " tristate \"" + fabric_mod_name.upper() + " fabric module\"\n" + buf += " depends on TARGET_CORE && CONFIGFS_FS\n" + buf += " default n\n" + buf += " help\n" + buf += " Say Y here to enable the " + fabric_mod_name.upper() + " fabric module\n" + + ret = p.write(buf) + if ret: + tcm_mod_err("Unable to write f: " + f) + + p.close() + return + +def tcm_mod_add_kbuild(tcm_dir, fabric_mod_name): + buf = "obj-$(CONFIG_" + fabric_mod_name.upper() + ") += " + fabric_mod_name.lower() + "/\n" + kbuild = tcm_dir + "/drivers/target/Makefile" + + f = open(kbuild, 'a') + f.write(buf) + f.close() + return + +def tcm_mod_add_kconfig(tcm_dir, fabric_mod_name): + buf = "source \"drivers/target/" + fabric_mod_name.lower() + "/Kconfig\"\n" + kconfig = tcm_dir + "/drivers/target/Kconfig" + + f = open(kconfig, 'a') + f.write(buf) + f.close() + return + +def main(modname, proto_ident): +# proto_ident = "FC" +# proto_ident = "SAS" +# proto_ident = "iSCSI" + + tcm_dir = os.getcwd(); + tcm_dir += "/../../" + print "tcm_dir: " + tcm_dir + fabric_mod_name = modname + fabric_mod_dir = tcm_dir + "drivers/target/" + fabric_mod_name + print "Set fabric_mod_name: " + fabric_mod_name + print "Set fabric_mod_dir: " + fabric_mod_dir + print "Using proto_ident: " + proto_ident + + if proto_ident != "FC" and proto_ident != "SAS" and proto_ident != "iSCSI": + print "Unsupported proto_ident: " + proto_ident + sys.exit(1) + + ret = tcm_mod_create_module_subdir(fabric_mod_dir) + if ret: + print "tcm_mod_create_module_subdir() failed because module already exists!" + sys.exit(1) + + tcm_mod_build_base_includes(proto_ident, fabric_mod_dir, fabric_mod_name) + tcm_mod_scan_fabric_ops(tcm_dir) + tcm_mod_dump_fabric_ops(proto_ident, fabric_mod_dir, fabric_mod_name) + tcm_mod_build_configfs(proto_ident, fabric_mod_dir, fabric_mod_name) + tcm_mod_build_kbuild(fabric_mod_dir, fabric_mod_name) + tcm_mod_build_kconfig(fabric_mod_dir, fabric_mod_name) + + input = raw_input("Would you like to add " + fabric_mod_name + " to drivers/target/Makefile..? [yes,no]: ") + if input == "yes" or input == "y": + tcm_mod_add_kbuild(tcm_dir, fabric_mod_name) + + input = raw_input("Would you like to add " + fabric_mod_name + " to drivers/target/Kconfig..? [yes,no]: ") + if input == "yes" or input == "y": + tcm_mod_add_kconfig(tcm_dir, fabric_mod_name) + + return + +parser = optparse.OptionParser() +parser.add_option('-m', '--modulename', help='Module name', dest='modname', + action='store', nargs=1, type='string') +parser.add_option('-p', '--protoident', help='Protocol Ident', dest='protoident', + action='store', nargs=1, type='string') + +(opts, args) = parser.parse_args() + +mandatories = ['modname', 'protoident'] +for m in mandatories: + if not opts.__dict__[m]: + print "mandatory option is missing\n" + parser.print_help() + exit(-1) + +if __name__ == "__main__": + + main(str(opts.modname), opts.protoident) diff --git a/Documentation/target/tcm_mod_builder.rst b/Documentation/target/tcm_mod_builder.rst new file mode 100644 index 000000000..9bfc9822e --- /dev/null +++ b/Documentation/target/tcm_mod_builder.rst @@ -0,0 +1,149 @@ +========================================= +The TCM v4 fabric module script generator +========================================= + +Greetings all, + +This document is intended to be a mini-HOWTO for using the tcm_mod_builder.py +script to generate a brand new functional TCM v4 fabric .ko module of your very own, +that once built can be immediately be loaded to start access the new TCM/ConfigFS +fabric skeleton, by simply using:: + + modprobe $TCM_NEW_MOD + mkdir -p /sys/kernel/config/target/$TCM_NEW_MOD + +This script will create a new drivers/target/$TCM_NEW_MOD/, and will do the following + + 1) Generate new API callers for drivers/target/target_core_fabric_configs.c logic + ->make_tpg(), ->drop_tpg(), ->make_wwn(), ->drop_wwn(). These are created + into $TCM_NEW_MOD/$TCM_NEW_MOD_configfs.c + 2) Generate basic infrastructure for loading/unloading LKMs and TCM/ConfigFS fabric module + using a skeleton struct target_core_fabric_ops API template. + 3) Based on user defined T10 Proto_Ident for the new fabric module being built, + the TransportID / Initiator and Target WWPN related handlers for + SPC-3 persistent reservation are automatically generated in $TCM_NEW_MOD/$TCM_NEW_MOD_fabric.c + using drivers/target/target_core_fabric_lib.c logic. + 4) NOP API calls for all other Data I/O path and fabric dependent attribute logic + in $TCM_NEW_MOD/$TCM_NEW_MOD_fabric.c + +tcm_mod_builder.py depends upon the mandatory '-p $PROTO_IDENT' and '-m +$FABRIC_MOD_name' parameters, and actually running the script looks like:: + + target:/mnt/sdb/lio-core-2.6.git/Documentation/target# python tcm_mod_builder.py -p iSCSI -m tcm_nab5000 + tcm_dir: /mnt/sdb/lio-core-2.6.git/Documentation/target/../../ + Set fabric_mod_name: tcm_nab5000 + Set fabric_mod_dir: + /mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000 + Using proto_ident: iSCSI + Creating fabric_mod_dir: + /mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000 + Writing file: + /mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000/tcm_nab5000_base.h + Using tcm_mod_scan_fabric_ops: + /mnt/sdb/lio-core-2.6.git/Documentation/target/../../include/target/target_core_fabric_ops.h + Writing file: + /mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000/tcm_nab5000_fabric.c + Writing file: + /mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000/tcm_nab5000_fabric.h + Writing file: + /mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000/tcm_nab5000_configfs.c + Writing file: + /mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000/Kbuild + Writing file: + /mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000/Kconfig + Would you like to add tcm_nab5000to drivers/target/Kbuild..? [yes,no]: yes + Would you like to add tcm_nab5000to drivers/target/Kconfig..? [yes,no]: yes + +At the end of tcm_mod_builder.py. the script will ask to add the following +line to drivers/target/Kbuild:: + + obj-$(CONFIG_TCM_NAB5000) += tcm_nab5000/ + +and the same for drivers/target/Kconfig:: + + source "drivers/target/tcm_nab5000/Kconfig" + +#) Run 'make menuconfig' and select the new CONFIG_TCM_NAB5000 item:: + + <M> TCM_NAB5000 fabric module + +#) Build using 'make modules', once completed you will have:: + + target:/mnt/sdb/lio-core-2.6.git# ls -la drivers/target/tcm_nab5000/ + total 1348 + drwxr-xr-x 2 root root 4096 2010-10-05 03:23 . + drwxr-xr-x 9 root root 4096 2010-10-05 03:22 .. + -rw-r--r-- 1 root root 282 2010-10-05 03:22 Kbuild + -rw-r--r-- 1 root root 171 2010-10-05 03:22 Kconfig + -rw-r--r-- 1 root root 49 2010-10-05 03:23 modules.order + -rw-r--r-- 1 root root 738 2010-10-05 03:22 tcm_nab5000_base.h + -rw-r--r-- 1 root root 9096 2010-10-05 03:22 tcm_nab5000_configfs.c + -rw-r--r-- 1 root root 191200 2010-10-05 03:23 tcm_nab5000_configfs.o + -rw-r--r-- 1 root root 40504 2010-10-05 03:23 .tcm_nab5000_configfs.o.cmd + -rw-r--r-- 1 root root 5414 2010-10-05 03:22 tcm_nab5000_fabric.c + -rw-r--r-- 1 root root 2016 2010-10-05 03:22 tcm_nab5000_fabric.h + -rw-r--r-- 1 root root 190932 2010-10-05 03:23 tcm_nab5000_fabric.o + -rw-r--r-- 1 root root 40713 2010-10-05 03:23 .tcm_nab5000_fabric.o.cmd + -rw-r--r-- 1 root root 401861 2010-10-05 03:23 tcm_nab5000.ko + -rw-r--r-- 1 root root 265 2010-10-05 03:23 .tcm_nab5000.ko.cmd + -rw-r--r-- 1 root root 459 2010-10-05 03:23 tcm_nab5000.mod.c + -rw-r--r-- 1 root root 23896 2010-10-05 03:23 tcm_nab5000.mod.o + -rw-r--r-- 1 root root 22655 2010-10-05 03:23 .tcm_nab5000.mod.o.cmd + -rw-r--r-- 1 root root 379022 2010-10-05 03:23 tcm_nab5000.o + -rw-r--r-- 1 root root 211 2010-10-05 03:23 .tcm_nab5000.o.cmd + +#) Load the new module, create a lun_0 configfs group, and add new TCM Core + IBLOCK backstore symlink to port:: + + target:/mnt/sdb/lio-core-2.6.git# insmod drivers/target/tcm_nab5000.ko + target:/mnt/sdb/lio-core-2.6.git# mkdir -p /sys/kernel/config/target/nab5000/iqn.foo/tpgt_1/lun/lun_0 + target:/mnt/sdb/lio-core-2.6.git# cd /sys/kernel/config/target/nab5000/iqn.foo/tpgt_1/lun/lun_0/ + target:/sys/kernel/config/target/nab5000/iqn.foo/tpgt_1/lun/lun_0# ln -s /sys/kernel/config/target/core/iblock_0/lvm_test0 nab5000_port + + target:/sys/kernel/config/target/nab5000/iqn.foo/tpgt_1/lun/lun_0# cd - + target:/mnt/sdb/lio-core-2.6.git# tree /sys/kernel/config/target/nab5000/ + /sys/kernel/config/target/nab5000/ + |-- discovery_auth + |-- iqn.foo + | `-- tpgt_1 + | |-- acls + | |-- attrib + | |-- lun + | | `-- lun_0 + | | |-- alua_tg_pt_gp + | | |-- alua_tg_pt_offline + | | |-- alua_tg_pt_status + | | |-- alua_tg_pt_write_md + | | `-- nab5000_port -> ../../../../../../target/core/iblock_0/lvm_test0 + | |-- np + | `-- param + `-- version + + target:/mnt/sdb/lio-core-2.6.git# lsmod + Module Size Used by + tcm_nab5000 3935 4 + iscsi_target_mod 193211 0 + target_core_stgt 8090 0 + target_core_pscsi 11122 1 + target_core_file 9172 2 + target_core_iblock 9280 1 + target_core_mod 228575 31 + tcm_nab5000,iscsi_target_mod,target_core_stgt,target_core_pscsi,target_core_file,target_core_iblock + libfc 73681 0 + scsi_debug 56265 0 + scsi_tgt 8666 1 target_core_stgt + configfs 20644 2 target_core_mod + +---------------------------------------------------------------------- + +Future TODO items +================= + + 1) Add more T10 proto_idents + 2) Make tcm_mod_dump_fabric_ops() smarter and generate function pointer + defs directly from include/target/target_core_fabric_ops.h:struct target_core_fabric_ops + structure members. + +October 5th, 2010 + +Nicholas A. Bellinger <nab@linux-iscsi.org> diff --git a/Documentation/target/tcmu-design.rst b/Documentation/target/tcmu-design.rst new file mode 100644 index 000000000..e47047e32 --- /dev/null +++ b/Documentation/target/tcmu-design.rst @@ -0,0 +1,405 @@ +==================== +TCM Userspace Design +==================== + + +.. Contents: + + 1) Design + a) Background + b) Benefits + c) Design constraints + d) Implementation overview + i. Mailbox + ii. Command ring + iii. Data Area + e) Device discovery + f) Device events + g) Other contingencies + 2) Writing a user pass-through handler + a) Discovering and configuring TCMU uio devices + b) Waiting for events on the device(s) + c) Managing the command ring + 3) A final note + + +Design +====== + +TCM is another name for LIO, an in-kernel iSCSI target (server). +Existing TCM targets run in the kernel. TCMU (TCM in Userspace) +allows userspace programs to be written which act as iSCSI targets. +This document describes the design. + +The existing kernel provides modules for different SCSI transport +protocols. TCM also modularizes the data storage. There are existing +modules for file, block device, RAM or using another SCSI device as +storage. These are called "backstores" or "storage engines". These +built-in modules are implemented entirely as kernel code. + +Background +---------- + +In addition to modularizing the transport protocol used for carrying +SCSI commands ("fabrics"), the Linux kernel target, LIO, also modularizes +the actual data storage as well. These are referred to as "backstores" +or "storage engines". The target comes with backstores that allow a +file, a block device, RAM, or another SCSI device to be used for the +local storage needed for the exported SCSI LUN. Like the rest of LIO, +these are implemented entirely as kernel code. + +These backstores cover the most common use cases, but not all. One new +use case that other non-kernel target solutions, such as tgt, are able +to support is using Gluster's GLFS or Ceph's RBD as a backstore. The +target then serves as a translator, allowing initiators to store data +in these non-traditional networked storage systems, while still only +using standard protocols themselves. + +If the target is a userspace process, supporting these is easy. tgt, +for example, needs only a small adapter module for each, because the +modules just use the available userspace libraries for RBD and GLFS. + +Adding support for these backstores in LIO is considerably more +difficult, because LIO is entirely kernel code. Instead of undertaking +the significant work to port the GLFS or RBD APIs and protocols to the +kernel, another approach is to create a userspace pass-through +backstore for LIO, "TCMU". + + +Benefits +-------- + +In addition to allowing relatively easy support for RBD and GLFS, TCMU +will also allow easier development of new backstores. TCMU combines +with the LIO loopback fabric to become something similar to FUSE +(Filesystem in Userspace), but at the SCSI layer instead of the +filesystem layer. A SUSE, if you will. + +The disadvantage is there are more distinct components to configure, and +potentially to malfunction. This is unavoidable, but hopefully not +fatal if we're careful to keep things as simple as possible. + +Design constraints +------------------ + +- Good performance: high throughput, low latency +- Cleanly handle if userspace: + + 1) never attaches + 2) hangs + 3) dies + 4) misbehaves + +- Allow future flexibility in user & kernel implementations +- Be reasonably memory-efficient +- Simple to configure & run +- Simple to write a userspace backend + + +Implementation overview +----------------------- + +The core of the TCMU interface is a memory region that is shared +between kernel and userspace. Within this region is: a control area +(mailbox); a lockless producer/consumer circular buffer for commands +to be passed up, and status returned; and an in/out data buffer area. + +TCMU uses the pre-existing UIO subsystem. UIO allows device driver +development in userspace, and this is conceptually very close to the +TCMU use case, except instead of a physical device, TCMU implements a +memory-mapped layout designed for SCSI commands. Using UIO also +benefits TCMU by handling device introspection (e.g. a way for +userspace to determine how large the shared region is) and signaling +mechanisms in both directions. + +There are no embedded pointers in the memory region. Everything is +expressed as an offset from the region's starting address. This allows +the ring to still work if the user process dies and is restarted with +the region mapped at a different virtual address. + +See target_core_user.h for the struct definitions. + +The Mailbox +----------- + +The mailbox is always at the start of the shared memory region, and +contains a version, details about the starting offset and size of the +command ring, and head and tail pointers to be used by the kernel and +userspace (respectively) to put commands on the ring, and indicate +when the commands are completed. + +version - 1 (userspace should abort if otherwise) + +flags: + - TCMU_MAILBOX_FLAG_CAP_OOOC: + indicates out-of-order completion is supported. + See "The Command Ring" for details. + +cmdr_off + The offset of the start of the command ring from the start + of the memory region, to account for the mailbox size. +cmdr_size + The size of the command ring. This does *not* need to be a + power of two. +cmd_head + Modified by the kernel to indicate when a command has been + placed on the ring. +cmd_tail + Modified by userspace to indicate when it has completed + processing of a command. + +The Command Ring +---------------- + +Commands are placed on the ring by the kernel incrementing +mailbox.cmd_head by the size of the command, modulo cmdr_size, and +then signaling userspace via uio_event_notify(). Once the command is +completed, userspace updates mailbox.cmd_tail in the same way and +signals the kernel via a 4-byte write(). When cmd_head equals +cmd_tail, the ring is empty -- no commands are currently waiting to be +processed by userspace. + +TCMU commands are 8-byte aligned. They start with a common header +containing "len_op", a 32-bit value that stores the length, as well as +the opcode in the lowest unused bits. It also contains cmd_id and +flags fields for setting by the kernel (kflags) and userspace +(uflags). + +Currently only two opcodes are defined, TCMU_OP_CMD and TCMU_OP_PAD. + +When the opcode is CMD, the entry in the command ring is a struct +tcmu_cmd_entry. Userspace finds the SCSI CDB (Command Data Block) via +tcmu_cmd_entry.req.cdb_off. This is an offset from the start of the +overall shared memory region, not the entry. The data in/out buffers +are accessible via tht req.iov[] array. iov_cnt contains the number of +entries in iov[] needed to describe either the Data-In or Data-Out +buffers. For bidirectional commands, iov_cnt specifies how many iovec +entries cover the Data-Out area, and iov_bidi_cnt specifies how many +iovec entries immediately after that in iov[] cover the Data-In +area. Just like other fields, iov.iov_base is an offset from the start +of the region. + +When completing a command, userspace sets rsp.scsi_status, and +rsp.sense_buffer if necessary. Userspace then increments +mailbox.cmd_tail by entry.hdr.length (mod cmdr_size) and signals the +kernel via the UIO method, a 4-byte write to the file descriptor. + +If TCMU_MAILBOX_FLAG_CAP_OOOC is set for mailbox->flags, kernel is +capable of handling out-of-order completions. In this case, userspace can +handle command in different order other than original. Since kernel would +still process the commands in the same order it appeared in the command +ring, userspace need to update the cmd->id when completing the +command(a.k.a steal the original command's entry). + +When the opcode is PAD, userspace only updates cmd_tail as above -- +it's a no-op. (The kernel inserts PAD entries to ensure each CMD entry +is contiguous within the command ring.) + +More opcodes may be added in the future. If userspace encounters an +opcode it does not handle, it must set UNKNOWN_OP bit (bit 0) in +hdr.uflags, update cmd_tail, and proceed with processing additional +commands, if any. + +The Data Area +------------- + +This is shared-memory space after the command ring. The organization +of this area is not defined in the TCMU interface, and userspace +should access only the parts referenced by pending iovs. + + +Device Discovery +---------------- + +Other devices may be using UIO besides TCMU. Unrelated user processes +may also be handling different sets of TCMU devices. TCMU userspace +processes must find their devices by scanning sysfs +class/uio/uio*/name. For TCMU devices, these names will be of the +format:: + + tcm-user/<hba_num>/<device_name>/<subtype>/<path> + +where "tcm-user" is common for all TCMU-backed UIO devices. <hba_num> +and <device_name> allow userspace to find the device's path in the +kernel target's configfs tree. Assuming the usual mount point, it is +found at:: + + /sys/kernel/config/target/core/user_<hba_num>/<device_name> + +This location contains attributes such as "hw_block_size", that +userspace needs to know for correct operation. + +<subtype> will be a userspace-process-unique string to identify the +TCMU device as expecting to be backed by a certain handler, and <path> +will be an additional handler-specific string for the user process to +configure the device, if needed. The name cannot contain ':', due to +LIO limitations. + +For all devices so discovered, the user handler opens /dev/uioX and +calls mmap():: + + mmap(NULL, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0) + +where size must be equal to the value read from +/sys/class/uio/uioX/maps/map0/size. + + +Device Events +------------- + +If a new device is added or removed, a notification will be broadcast +over netlink, using a generic netlink family name of "TCM-USER" and a +multicast group named "config". This will include the UIO name as +described in the previous section, as well as the UIO minor +number. This should allow userspace to identify both the UIO device and +the LIO device, so that after determining the device is supported +(based on subtype) it can take the appropriate action. + + +Other contingencies +------------------- + +Userspace handler process never attaches: + +- TCMU will post commands, and then abort them after a timeout period + (30 seconds.) + +Userspace handler process is killed: + +- It is still possible to restart and re-connect to TCMU + devices. Command ring is preserved. However, after the timeout period, + the kernel will abort pending tasks. + +Userspace handler process hangs: + +- The kernel will abort pending tasks after a timeout period. + +Userspace handler process is malicious: + +- The process can trivially break the handling of devices it controls, + but should not be able to access kernel memory outside its shared + memory areas. + + +Writing a user pass-through handler (with example code) +======================================================= + +A user process handing a TCMU device must support the following: + +a) Discovering and configuring TCMU uio devices +b) Waiting for events on the device(s) +c) Managing the command ring: Parsing operations and commands, + performing work as needed, setting response fields (scsi_status and + possibly sense_buffer), updating cmd_tail, and notifying the kernel + that work has been finished + +First, consider instead writing a plugin for tcmu-runner. tcmu-runner +implements all of this, and provides a higher-level API for plugin +authors. + +TCMU is designed so that multiple unrelated processes can manage TCMU +devices separately. All handlers should make sure to only open their +devices, based opon a known subtype string. + +a) Discovering and configuring TCMU UIO devices:: + + /* error checking omitted for brevity */ + + int fd, dev_fd; + char buf[256]; + unsigned long long map_len; + void *map; + + fd = open("/sys/class/uio/uio0/name", O_RDONLY); + ret = read(fd, buf, sizeof(buf)); + close(fd); + buf[ret-1] = '\0'; /* null-terminate and chop off the \n */ + + /* we only want uio devices whose name is a format we expect */ + if (strncmp(buf, "tcm-user", 8)) + exit(-1); + + /* Further checking for subtype also needed here */ + + fd = open(/sys/class/uio/%s/maps/map0/size, O_RDONLY); + ret = read(fd, buf, sizeof(buf)); + close(fd); + str_buf[ret-1] = '\0'; /* null-terminate and chop off the \n */ + + map_len = strtoull(buf, NULL, 0); + + dev_fd = open("/dev/uio0", O_RDWR); + map = mmap(NULL, map_len, PROT_READ|PROT_WRITE, MAP_SHARED, dev_fd, 0); + + + b) Waiting for events on the device(s) + + while (1) { + char buf[4]; + + int ret = read(dev_fd, buf, 4); /* will block */ + + handle_device_events(dev_fd, map); + } + + +c) Managing the command ring:: + + #include <linux/target_core_user.h> + + int handle_device_events(int fd, void *map) + { + struct tcmu_mailbox *mb = map; + struct tcmu_cmd_entry *ent = (void *) mb + mb->cmdr_off + mb->cmd_tail; + int did_some_work = 0; + + /* Process events from cmd ring until we catch up with cmd_head */ + while (ent != (void *)mb + mb->cmdr_off + mb->cmd_head) { + + if (tcmu_hdr_get_op(ent->hdr.len_op) == TCMU_OP_CMD) { + uint8_t *cdb = (void *)mb + ent->req.cdb_off; + bool success = true; + + /* Handle command here. */ + printf("SCSI opcode: 0x%x\n", cdb[0]); + + /* Set response fields */ + if (success) + ent->rsp.scsi_status = SCSI_NO_SENSE; + else { + /* Also fill in rsp->sense_buffer here */ + ent->rsp.scsi_status = SCSI_CHECK_CONDITION; + } + } + else if (tcmu_hdr_get_op(ent->hdr.len_op) != TCMU_OP_PAD) { + /* Tell the kernel we didn't handle unknown opcodes */ + ent->hdr.uflags |= TCMU_UFLAG_UNKNOWN_OP; + } + else { + /* Do nothing for PAD entries except update cmd_tail */ + } + + /* update cmd_tail */ + mb->cmd_tail = (mb->cmd_tail + tcmu_hdr_get_len(&ent->hdr)) % mb->cmdr_size; + ent = (void *) mb + mb->cmdr_off + mb->cmd_tail; + did_some_work = 1; + } + + /* Notify the kernel that work has been finished */ + if (did_some_work) { + uint32_t buf = 0; + + write(fd, &buf, 4); + } + + return 0; + } + + +A final note +============ + +Please be careful to return codes as defined by the SCSI +specifications. These are different than some values defined in the +scsi/scsi.h include file. For example, CHECK CONDITION's status code +is 2, not 1. |