Re: [ANNOUNCE]: ConfigFS enabled Generic Target Mode and iSCSI Target Stack on v2.6.27-rc7

["Nicholas A. Bellinger" <nab@linux-iscsi.org>]

On Thu, 2008-10-02 at 21:00 +0400, Vladislav Bolkhovitin wrote:
> Nicholas A. Bellinger wrote:
> >>> # Add some more HBA and storage Objects
> >>> target:~# mkdir -p $TARGET/fileio_0/file_object
> >>> target:~# mkdir -p $TARGET/rd_mcp_0/ramdisk0
> >>> target:~# mkdir -p $TARGET/rd_dr_0/ramdisk0
> >>>
> >>> target:~# mkdir -p $TARGET/pscsi_0/sdd
> >>> target:~# echo scsi_channel_id=0,scsi_target_id=3,scsi_lun_id=0 > $TARGET/pscsi_0/sdd/dev_control   
> >>> target:~# echo 1 > $TARGET/pscsi_0/sdd/dev_enable 
> >>>
> >>> # Now, create LUN 1 and another Port Symlink to a new device on the same $IQN/tpgt_1
> >>> mkdir -p "$FABRIC/$DEF_IQN/tpgt_1/lun/lun_1"
> >>> # Create the iSCSI Target Port Mapping for $DEF_IN/tpgt_1 LUN 1
> >>> # to lvm_test0 and give it the port symbolic name of lio_east_port
> >>> ln -s $TARGET/pscsi_0/sdd/ "$FABRIC/$DEF_IQN/tpgt_1/lun/lun_1/lio_east_port"
> >>>
> >>> target:~# tree $CONFIGFS
> >>> /sys/kernel/config/
> >>> `-- target
> >>>     |-- core
> >>>     |   |-- fileio_0
> >>>     |   |   |-- file_object
> >>>     |   |   |   |-- dev_control
> >>>     |   |   |   |-- dev_enable
> >>>     |   |   |   `-- dev_info
> >>>     |   |   `-- hba_info
> >>>     |   |-- iblock_0
> >>>     |   |   |-- hba_info
> >>>     |   |   `-- lvm_test0
> >>>     |   |       |-- dev_control
> >>>     |   |       |-- dev_enable
> >>>     |   |       `-- dev_info
> >>>     |   |-- pscsi_0
> >>>     |   |   |-- hba_info
> >>>     |   |   `-- sdd
> >>>     |   |       |-- dev_control
> >>>     |   |       |-- dev_enable
> >>>     |   |       `-- dev_info
> >>>     |   |-- rd_dr_0
> >>>     |   |   |-- hba_info
> >>>     |   |   `-- ramdisk0
> >>>     |   |       |-- dev_control
> >>>     |   |       |-- dev_enable
> >>>     |   |       `-- dev_info
> >>>     |   `-- rd_mcp_0
> >>>     |       |-- hba_info
> >>>     |       `-- ramdisk0
> >>>     |           |-- dev_control
> >>>     |           |-- dev_enable
> >>>     |           `-- dev_info
> >>>     |-- iscsi
> >>>     |   |-- iqn.2003-01.org.linux-iscsi.target.i686:sn.e475ed6fcdd0
> >>>     |   |   `-- tpgt_1
> >>>     |   |       |-- lun
> >>>     |   |       |   |-- lun_0
> >>>     |   |       |   |   |-- lio_west_port -> ../../../../../../target/core/iblock_0/lvm_test0
> >>>     |   |       |   |   |-- port_control
> >>>     |   |       |   |   `-- port_info
> >>>     |   |       |   `-- lun_1
> >>>     |   |       |       |-- lio_east_port -> ../../../../../../target/core/pscsi_0/sdd
> >>>     |   |       |       |-- port_control
> >>>     |   |       |       `-- port_info
> >>>     |   |       |-- np
> >>>     |   |       |   `-- 172.16.201.137:3260
> >>>     |   |       |       `-- portal_info
> >>>     |   |       |-- tpg_control
> >>>     |   |       `-- tpg_enable
> >>>     |   `-- lio_version
> >>>     `-- version
> >>>
> >>> 22 directories, 29 files
> >> It's good, I like it. The only thing concerns me that, considering how 
> >> much time *I* spent to understand it, for an average user understanding 
> >> it can be an unbearable nightmare ;)
> >>
> > 
> > Well, the idea is not necessarily making the configfs interface the
> > easiest to use in the world by user directly through $CONFIGFS, but to
> > make the CLI scripts that speak $CONFIGFS/target CLI, and of course the
> > actual UIs for user that interact with generic target core and
> > $FABRIC_MODs be as simple and elegent as possible.  
> > 
> > That is what I believe the balance that a configfs enabled generic
> > target core provides to both the $CONFIGFS/target API and to $FABRIC_MOD
> > maintainers looking to port their code to use a generic control
> > infrastructure.  :-)
> > 
> >> In a few days I'll write a proposed configfs hierarchy for existing SCST 
> >> /proc interface.
> > 
> > Sounds good!  Please let me know if you have questions.
> 
> There's one unsolved problem. As I've already written, SCST core needs 
> an ability to provide to user space a large amount of data, which may 
> not fit to a single page.
>
> A list of connected initiators ("sessions" 
> file in /proc), for instance. Each initiator in that list has a number 
> of attributes: initiator name, target template name, count of 
> outstanding commands, etc. The logical way for that would be to create a 
> subdirectory for each initiator, like:
> 
> /sys/kernel/config/
> `-- target
>      `-- sessions
>          `-- session1
>          |   |-- initiator_name
>          |   |-- template_name
>          |   `-- commands
>          |
>          `-- session2
>              |-- initiator_name
>              `-- template_name
>              `-- commands
>

The the Initiator Port ACLs need to go
under /sys/kernel/config/target/$FABRIC because the struct fabric_acl *
will always contain fabric dependent config items.  For example, Since
these struct fabric_acl_t do *NOT* symlink directly back to
target_core_mod under /sys/kernel/config/target/core/$HBA/$DEV, but to
fabric_lun_t (iscsi_lun_t in my case) to Symlink to
a /sys/kernel/config/target/core/$HBA/$DEV that has been registered with
the generic target configfs infrastructure.

Here is what I am thinking wrt /sys/kernel/config/target/iscsi and iSCSI
Initiator Node ACLs to iSCSI Portal Groups and iSCSI LUNs attached to
those Portal Groups.  There are two cases:

*) The production case with with user creating those ACLs under $FABRIC
(which is what I will focus on now).

* And "Demo Mode" case where any Initiator logging into
$FABRIC/$ENDPOINT/$PORTAL can have access to all
$FABRIC/$ENDPOINT/lun/lun_*/*my_ports*

The production ACL case would look like:

export CONFIGFS=/sys/kernel/config/
export TARGET=/sys/kernel/config/target/core/
export FABRIC=/sys/kernel/config/target/iscsi/

TARGET_IQN=iqn.2003-01.org.linux-iscsi.ps3-cell.ppc64:sn.f8f651bd5fec
INITIATOR_IQN=iqn.1993-08.org.debian:01.f82074ca555f

<Setup $STORAGE_OBJECTs under $TARGET>

# Create the LIO-target endpoint
mkdir -p "$FABRIC/$TARGET_IQN/tpgt_1/np/172.16.201.137:3260"
mkdir -p "$FABRIC/$TARGET_IQN/tpgt_1/lun/lun_0"

<Setup Port Symlinks from $TARGET to $TARGET_IQN/tpgt_1/lun/lun_0>

# Create the Initiator ACL under $TARGET_IQN/tpgt_1
mkdir -p $"FABRIC/$TARGET_IQN/tpgt_1/initiators/$INITIATOR_IQN"
# Allow $INITIATOR_IQN access to tpgt_1/lun/lun_0/
ln -s "$FABRIC/$TARGET_IQN/tpgt_1/lun/lun_0" \
	"$FABRIC/$TARGET_IQN/tpgt_1/initiators/$INITIATOR_IQN/lun_0"

>From there, you don't have to worry about PAGE_SIZE limitiations w/o, I
can simply use use:

cat $FABRIC/iqn*/tpgt*/initiators/*/session

to see which acl'ed iSCSI Initiators are logged in on all iSCSI Target
Ports.

Also I should add that I am currently using /proc/scsi_target/mib
and /proc/iscsi_target_mib for READ-ONLY data with target_core_mod.ko
and iscsi_target_mod.ko respectively.  For the other "Demo Mode" case
mentioned above, I am currently using /proc/iscsi_target/mib/sess_attr
to see the active sessions for LIO-Target.

I will be implementing this model over the next days..  I will post the
commit once its up and you can have a look..

--nab

>
>
> But looks like configfs requires each subdirectory to be created 
> manually by user via, e.g., mkdir command. It would be really strange if 
> we require user to manually create "sessions" subdirectory to be able to 
> see a list of connected initiators. Do I miss anything?
> 
> Vlad
>