TCM v4 fabric module script generator

생성기의 목적과 산출 code

이 mini-HOWTO는 `tcm_mod_builder.py`로 새 TCM v4 fabric kernel module을 생성하는 방법을 설명한다. build한 `.ko`는 `modprobe $TCM_NEW_MOD`로 load하고 `/sys/kernel/config/target/$TCM_NEW_MOD`를 만들어 TCM/ConfigFS fabric skeleton에 즉시 접근할 수 있다.

script는 `drivers/target/$TCM_NEW_MOD/` directory를 새로 만든다. `target_core_fabric_configs.c` logic에 대응하는 `make_tpg()`, `drop_tpg()`, `make_wwn()`, `drop_wwn()` API caller를 `$TCM_NEW_MOD_configfs.c`에 생성한다.

LKM load/unload와 TCM/ConfigFS fabric module을 위한 기본 infrastructure를 `struct target_core_fabric_ops` skeleton template로 만든다.

사용자가 정한 T10 `Proto_Ident`를 바탕으로 SPC-3 persistent reservation에 필요한 TransportID, Initiator, Target WWPN handler를 `target_core_fabric_lib.c` logic을 이용해 `$TCM_NEW_MOD_fabric.c`에 자동 생성한다.

그 밖의 Data I/O path와 fabric-dependent attribute logic에는 NOP API call을 `$TCM_NEW_MOD_fabric.c`에 생성한다.

=========================================
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

필수 option과 생성 file

`tcm_mod_builder.py`는 필수 option `-p $PROTO_IDENT`와 `-m $FABRIC_MOD_name`을 요구한다. 예제는 protocol `iSCSI`, module name `tcm_nab5000`으로 실행한다.

출력은 source tree root와 fabric module 이름·directory·protocol identifier를 확인한 뒤 `drivers/target/tcm_nab5000`을 만든다.

생성 file은 `tcm_nab5000_base.h`, `tcm_nab5000_fabric.c`, `tcm_nab5000_fabric.h`, `tcm_nab5000_configfs.c`, `Kbuild`, `Kconfig`다. fabric ops template는 `include/target/target_core_fabric_ops.h`에서 scan한다.

마지막에 새 module을 상위 `drivers/target/Kbuild`와 `drivers/target/Kconfig`에 추가할지 각각 묻고 예제에서는 둘 다 yes로 답한다.

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

Kbuild·Kconfig와 build

script 끝에서 상위 `drivers/target/Kbuild`에는 `obj-$(CONFIG_TCM_NAB5000) += tcm_nab5000/`를, `drivers/target/Kconfig`에는 `source "drivers/target/tcm_nab5000/Kconfig"`를 추가한다.

`make menuconfig`에서 `TCM_NAB5000 fabric module`을 module로 선택하고 `make modules`로 build한다.

예제 build directory에는 source와 header, Kbuild/Kconfig, object와 command metadata, `modules.order`, module metadata, 최종 `tcm_nab5000.ko`가 생성된다. 원문은 각 file의 당시 크기와 2010-10-05 timestamp를 그대로 보여 준다.

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

Module load와 LUN 구성

새 module을 `insmod drivers/target/tcm_nab5000.ko`로 load한 뒤 ConfigFS에 `nab5000/iqn.foo/tpgt_1/lun/lun_0` group을 만든다.

`lun_0`에서 `/sys/kernel/config/target/core/iblock_0/lvm_test0` backstore를 `nab5000_port`라는 symbolic link로 연결한다.

원문의 `tree` 출력은 root에 `discovery_auth`, `iqn.foo`, `version`이 있고 `iqn.foo/tpgt_1` 아래에 `acls`, `attrib`, `lun`, `np`, `param`이 있음을 보여 준다. `lun/lun_0`에는 ALUA attribute file들과 backstore를 가리키는 `nab5000_port` link가 있다.

#) 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

Load된 module 관계

`lsmod` 예에서는 `tcm_nab5000`이 load되어 있고 사용 count는 4다. `target_core_mod`는 새 module과 `iscsi_target_mod`, `target_core_stgt`, `target_core_pscsi`, `target_core_file`, `target_core_iblock`에서 사용된다.

그 밖에 `libfc`, `scsi_debug`, `scsi_tgt`, `configfs`가 표시된다. `configfs`는 `target_core_mod`가 사용하며 target object hierarchy를 userspace에 노출한다.

    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

향후 작업과 저자

향후 TODO는 더 많은 T10 `proto_ident`를 추가하는 것과 `tcm_mod_dump_fabric_ops()`를 개선하는 것이다.

두 번째 항목은 `include/target/target_core_fabric_ops.h`의 `struct target_core_fabric_ops` member를 직접 읽어 function pointer definition을 생성하도록 만드는 계획이다.

문서는 2010년 10월 5일 Nicholas A. Bellinger가 작성했다.

----------------------------------------------------------------------

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>