[stgt] [PATCH 0/2] [tgt]: Add proper SG_IO struct cmd CDB passthrough

[FUJITA Tomonori]

On Mon, 17 May 2010 22:12:54 -0700
"Nicholas A. Bellinger" <nab at linux-iscsi.org> wrote:

> These are two patches to allow the STGT SG_IO backstore to function using a
> new struct scsi_cmd->sg_iovec member with sg_io_hdr->iovec_count=1, and to update
> usr/scsi.c:scsi_cmd_perform() to allow for a hand off incoming descriptors into the
> struct device_type_template->cmd_passthrough() function pointer.
> 
> I initially updated usr/sbc.c to set sbc_rw() as it's CDB passthrough function for
> TYPE_DISK, but the logic should apply to any device types *_rw() functions.  Please let
> me know if this makes sense, and I will look at updating the other stgt device types.
> 
> So far with this patch, I am able to successfully mkfs new iSCSI TYPE_DISK LUNS with
> Open-iSCSI to the userspace STGT iSCSI fabric module + SG_IO into kernel level TCM_Loop
> virtual iSCSI target ports on a x86 HVM, and bulk 512KB DATA_SG_IO payloads between STGT
> and TCM_Loop are now functioning as expected.
> 
> There is one unresolved issue that I ran into while running initially with TCM_Loop
> and struct scsi_device->max_sectors=256.  SG_IO writes larger than the
> struct scsi_device->max_sectors are being returned with -EINVAL, but it appears that
> the CHECK_CONDITION is not actually being propigated back into STGT/iSCSI.
> 
> After increasing the TCM_Loop ports to struct scsi_device->max_sectors=1024 following
> the Open-iSCSI Initiator default, the 512KB paylods begin work as expected.  I will need
> to have a look at the case for CDB length > max_sectors, which means that bs_sg.c getting
> the correct scsi_status and sense data out of the kernel might still need more work.
> 
> In the mean time, please have a look at applying these patches.
> 
> Best,
> 
> Signed-off-by: Nicholas A. Bellinger <nab at linux-iscsi.org>
> 
> Nicholas Bellinger (2):
>   [tgt]: Add proper CDB passthrough for SG_IO backstores
>   [tgt]: Add support for SG_IO CDB passthrough in scsi_cmd_perform()
> 
>  usr/bs_sg.c     |   31 ++++++++++++++++++++++++-------
>  usr/sbc.c       |    1 +
>  usr/scsi.c      |   11 +++++++++++
>  usr/scsi_cmnd.h |    4 ++++
>  usr/tgtd.h      |    2 ++
>  5 files changed, 42 insertions(+), 7 deletions(-)

Thanks! Surely, the first patch looks fine.

I thought that you want to send all SCSI commands to your in-kernel
target code via SG_IO. That's, you want the proper 'pass-through' code
since tgt's pass-through code is broken.

However, looks like non I/O commands are still performed in user-space
tgt code and only I/O commands goes to kernel via SG_IO. Hmm, that's
what you want to do?
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