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


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