Re: [PATCH 05/11] target: support zero allocation length in REQUEST SENSE

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

On Fri, 2012-09-07 at 17:30 +0200, Paolo Bonzini wrote:
> Similar to INQUIRY and MODE SENSE, construct the sense data in a
> buffer and later copy it to the scatterlist.  Do not do anything,
> but still clear a pending unit attention condition, if the allocation
> length is zero.
> 
> However, SPC tells us that "If a REQUEST SENSE command is terminated with
> CHECK CONDITION status [and] the REQUEST SENSE command was received on
> an I_T nexus with a pending unit attention condition (i.e., before the
> device server reports CHECK CONDITION status), then the device server
> shall not clear the pending unit attention condition."  Do the
> transport_kmap_data_sg early to detect this case.
> 
> It also tells us "Device servers shall not adjust the additional sense
> length to reflect truncation if the allocation length is less than the
> sense data available", so do not do that!  Note that the err variable
> is write-only.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---

Ditto on this one as well.  Applied to target-pending/master.

Thanks Paolo!

>  drivers/target/target_core_spc.c  |   35 ++++++++++++++++++-----------------
>  include/target/target_core_base.h |    1 +
>  2 files changed, 19 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/target/target_core_spc.c b/drivers/target/target_core_spc.c
> index 4c861de..b905fb2 100644
> --- a/drivers/target/target_core_spc.c
> +++ b/drivers/target/target_core_spc.c
> @@ -877,9 +877,11 @@ static int spc_emulate_modesense(struct se_cmd *cmd)
>  static int spc_emulate_request_sense(struct se_cmd *cmd)
>  {
>  	unsigned char *cdb = cmd->t_task_cdb;
> -	unsigned char *buf;
> +	unsigned char *rbuf;
>  	u8 ua_asc = 0, ua_ascq = 0;
> -	int err = 0;
> +	unsigned char buf[SE_SENSE_BUF];
> +
> +	memset(buf, 0, SE_SENSE_BUF);
>  
>  	if (cdb[1] & 0x01) {
>  		pr_err("REQUEST_SENSE description emulation not"
> @@ -888,20 +890,21 @@ static int spc_emulate_request_sense(struct se_cmd *cmd)
>  		return -ENOSYS;
>  	}
>  
> -	buf = transport_kmap_data_sg(cmd);
> -
> -	if (!core_scsi3_ua_clear_for_request_sense(cmd, &ua_asc, &ua_ascq)) {
> +	rbuf = transport_kmap_data_sg(cmd);
> +	if (cmd->scsi_sense_reason != 0) {
> +		/*
> +		 * Out of memory.  We will fail with CHECK CONDITION, so
> +		 * we must not clear the unit attention condition.
> +		 */
> +		target_complete_cmd(cmd, CHECK_CONDITION);
> +		return 0;
> +	} else if (!core_scsi3_ua_clear_for_request_sense(cmd, &ua_asc, &ua_ascq)) {
>  		/*
>  		 * CURRENT ERROR, UNIT ATTENTION
>  		 */
>  		buf[0] = 0x70;
>  		buf[SPC_SENSE_KEY_OFFSET] = UNIT_ATTENTION;
>  
> -		if (cmd->data_length < 18) {
> -			buf[7] = 0x00;
> -			err = -EINVAL;
> -			goto end;
> -		}
>  		/*
>  		 * The Additional Sense Code (ASC) from the UNIT ATTENTION
>  		 */
> @@ -915,11 +916,6 @@ static int spc_emulate_request_sense(struct se_cmd *cmd)
>  		buf[0] = 0x70;
>  		buf[SPC_SENSE_KEY_OFFSET] = NO_SENSE;
>  
> -		if (cmd->data_length < 18) {
> -			buf[7] = 0x00;
> -			err = -EINVAL;
> -			goto end;
> -		}
>  		/*
>  		 * NO ADDITIONAL SENSE INFORMATION
>  		 */
> @@ -927,8 +923,11 @@ static int spc_emulate_request_sense(struct se_cmd *cmd)
>  		buf[7] = 0x0A;
>  	}
>  
> -end:
> -	transport_kunmap_data_sg(cmd);
> +	if (rbuf) {
> +		memcpy(rbuf, buf, min_t(u32, sizeof(buf), cmd->data_length));
> +		transport_kunmap_data_sg(cmd);
> +	}
> +
>  	target_complete_cmd(cmd, GOOD);
>  	return 0;
>  }
> diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
> index 015cea0..5be8937 100644
> --- a/include/target/target_core_base.h
> +++ b/include/target/target_core_base.h
> @@ -121,6 +121,7 @@
>  
>  #define SE_INQUIRY_BUF				512
>  #define SE_MODE_PAGE_BUF			512
> +#define SE_SENSE_BUF				96
>  
>  /* struct se_hba->hba_flags */
>  enum hba_flags_table {