Re: [PATCH 3/3] [tgt]: Add BSG v4 backstore support to usr/bs_sg.c

[Boaz Harrosh <bharrosh@panasas.com>]

On 06/07/2010 12:02 PM, Nicholas A. Bellinger wrote:
> On Mon, 2010-06-07 at 11:40 +0300, Boaz Harrosh wrote:
>> On 06/07/2010 06:50 AM, Nicholas A. Bellinger wrote:
>>> From: Nicholas Bellinger <nab@linux-iscsi.org>
>>>
>>> This patch adds initial support for the block layer implementation of the sg v4 interface
>>> (BSG) -> STGT with a new struct backingstore_template bsg_bst sharing code with the
>>> original sg_bst.  It adds for new function bs_bsg_cmd_submit() for incoming write I/O
>>> and bs_bsg_cmd_complete() for polling read I/O using include/linux/bsg.h:struct sg_io_v4.
>>>
>>> This patch also splits up bs_sg_open() to support both BSG and SG looking for the
>>> path "/dev/bsg" in bs_sg_open(), and getting max_queue using SG_GET_COMMAND_Q and
>>> calling SG_SET_RESERVED_SIZE (following the original bs_sg code in init_sg_device)
>>>
>>> Also chk_bsg_device() currently using a hardcoded 254 major as def for BSG does not
>>> appear in include/linux/major.h just yet..
>>>
>>> So far this has been tested with STGT/iSCSI <-> BSG <-> TCM_Loop SPC-4 iSCSI Target
>>> Port emulation and is able to mkfs, fsck and mount a filesystem from a TCM/IBLOCK
>>> Linux LVM kernel level backstore
>>>
>>> Signed-off-by: Nicholas A. Bellinger <nab@linux-iscsi.org>
>>> ---
>>>  usr/bs_sg.c     |  178 +++++++++++++++++++++++++++++++++++++++++++++++++++---
>>>  usr/scsi_cmnd.h |    7 ++
>>>  2 files changed, 175 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/usr/bs_sg.c b/usr/bs_sg.c
>>> index 23676ef..d071714 100644
>>> --- a/usr/bs_sg.c
>>> +++ b/usr/bs_sg.c
> 
> <SNIP>
> 
>>> +
>>> +static int bs_bsg_cmd_submit(struct scsi_cmd *cmd)
>>> +{
>>> +	struct scsi_lu *dev = cmd->dev;
>>> +	int fd = dev->fd;
>>> +	struct sg_io_v4 *io_hdr = &cmd->cmd_bsg_hdr;
>>> +	int err = 0;
>>> +	/*
>>> +	 * Following linux/include/linux/bsg.h
>>> +	 */
>>> +	/* [i] 'Q' to differentiate from v3 */
>>> +	io_hdr->guard = 'Q';
>>> +	io_hdr->protocol = BSG_PROTOCOL_SCSI;
>>> +	io_hdr->subprotocol = BSG_SUB_PROTOCOL_SCSI_CMD;
>>> +	io_hdr->request_len = cmd->scb_len;
>>> +	io_hdr->request = (unsigned long )cmd->scb;
>>> +
>>> +	if (scsi_get_data_dir(cmd) == DATA_WRITE) {
>>
>> Why the if? both sides are fully bidi just remove the ifs
>> and: OUT <= OUT, IN <= IN
>>
> 
> Whoops, thanks for pointing this one out (again).  Tested with
> unidirection commands and included into my local tgt.git/pass that I
> will send along to Tomo-san..
> 
> Btw, I still need to sort out BIDI support for TCM_Loop at some point in
> the not too distant future.  What would be a good way to generate BIDI
> traffic into STGT or a local SCSI LLD..?
> 
> Best,
> 
> --nab
> 

scsi_debug has some emulation for XOR commands, does that help?

Boaz