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

[FUJITA Tomonori]

On Wed, 16 Jun 2010 22:42:08 -0700
"Nicholas A. Bellinger" <nab at linux-iscsi.org> wrote:

> From: Nicholas Bellinger <nab at linux-iscsi.org>
> 
> This patch adds 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 adds BSG specific major checks in bs_sg_open() and for getting max_queue using
> SG_GET_COMMAND_Q and calling SG_SET_RESERVED_SIZE following init_sg_device().
> 
> 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.  This code has also been tested with SG_IO and the
> legacy codepath.
> 
> Signed-off-by: Nicholas A. Bellinger <nab at linux-iscsi.org>
> ---
>  usr/bs_sg.c     |  161 +++++++++++++++++++++++++++++++++++++++++++++++++++---
>  usr/scsi_cmnd.h |    3 +
>  2 files changed, 155 insertions(+), 9 deletions(-)
> 
> diff --git a/usr/bs_sg.c b/usr/bs_sg.c
> index bb03d46..e8e3551 100644
> --- a/usr/bs_sg.c
> +++ b/usr/bs_sg.c
> @@ -3,6 +3,9 @@
>   *
>   * Copyright (C) 2008 Alexander Nezhinsky <nezhinsky at gmail.com>
>   *
> + * Added linux/block/bsg.c support using struct sg_io_v4.
> + * Copyright (C) 2010 Nicholas A. Bellinger <nab at linux-iscsi.org>
> + *
>   * This program is free software; you can redistribute it and/or
>   * modify it under the terms of the GNU General Public License as
>   * published by the Free Software Foundation, version 2 of the
> @@ -33,6 +36,7 @@
>  #include <sys/stat.h>
>  #include <sys/epoll.h>
>  #include <scsi/sg.h>
> +#include <linux/bsg.h>

This breaks distributions that don't have linux/bsg.h. At least, I
care about RHEL5 so please copy linux/bsg.h into tgt's tree instead of
using linux/bsg.h.


>  #include "list.h"
>  #include "util.h"
> @@ -45,6 +49,14 @@
>  #define BS_SG_TIMEOUT	2000
>  #define BS_SG_SHIFT	9
>  
> +//#define BSG_DEBUG_IO
> +
> +#ifdef BSG_DEBUG_IO
> +#define BSG_IO(x...) eprintf(x)
> +#else
> +#define BSG_IO(x...)
> +#endif
> +

Hmm, can we avoid it?  We can enable/disable the debugging option on
the fly.


>  static int graceful_read(int fd, void *p_read, int to_read)
>  {
>  	int err;
> @@ -107,7 +119,7 @@ static int bs_sg_rw(int host_no, struct scsi_cmd *cmd)
>  	return SAM_STAT_CHECK_CONDITION;
>  }
>  
> -static void set_cmd_failed(struct scsi_cmd *cmd)
> +static int set_cmd_failed(struct scsi_cmd *cmd)
>  {
>  	int result = SAM_STAT_CHECK_CONDITION;
>  	uint16_t asc = ASC_READ_ERROR;
> @@ -115,6 +127,52 @@ static void set_cmd_failed(struct scsi_cmd *cmd)
>  
>  	scsi_set_result(cmd, result);
>  	sense_data_build(cmd, key, asc);
> +
> +	return result;
> +}
> +
> +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;

Hmm, why do we need to add struct sg_io_v4 to scsi_cmd? Can't we do
like bs_sg_cmd_submit?

I really like to avoid to fatten struct scsi_cmd.
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