[PATCH] tcm_qla2xxx: Fix residual for underrun commands that fail

[PATCH] tcm_qla2xxx: Fix residual for underrun commands that fail

[Roland Dreier]

From: Roland Dreier <roland@purestorage.com>

Suppose an initiator sends a DATA IN command with an allocation length
shorter than the FC transfer length -- we get a target message like

    TARGET_CORE[qla2xxx]: Expected Transfer Length: 256 does not match SCSI CDB Length: 0 for SAM Opcode: 0x12

In that case, the target core adjusts the data_length and sets
se_cmd->residual_count for the underrun.  But now suppose that command
fails and we end up in tcm_qla2xxx_queue_status() -- that function
unconditionally overwrites residual_count with the already adjusted
data_length, and the initiator will burp with a message like

    qla2xxx [0000:00:06.0]-301d:0: Dropped frame(s) detected (0x100 of 0x100 bytes).

Fix this by adding on to the existing underflow residual count instead.

Signed-off-by: Roland Dreier <roland@purestorage.com>
---
 drivers/scsi/qla2xxx/tcm_qla2xxx.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/qla2xxx/tcm_qla2xxx.c b/drivers/scsi/qla2xxx/tcm_qla2xxx.c
index 7a3870f..66b0b26 100644
--- a/drivers/scsi/qla2xxx/tcm_qla2xxx.c
+++ b/drivers/scsi/qla2xxx/tcm_qla2xxx.c
@@ -688,8 +688,12 @@ static int tcm_qla2xxx_queue_status(struct se_cmd *se_cmd)
 		 * For FCP_READ with CHECK_CONDITION status, clear cmd->bufflen
 		 * for qla_tgt_xmit_response LLD code
 		 */
+		if (se_cmd->se_cmd_flags & SCF_OVERFLOW_BIT) {
+			se_cmd->se_cmd_flags &= ~SCF_OVERFLOW_BIT;
+			se_cmd->residual_count = 0;
+		}
 		se_cmd->se_cmd_flags |= SCF_UNDERFLOW_BIT;
-		se_cmd->residual_count = se_cmd->data_length;
+		se_cmd->residual_count += se_cmd->data_length;
 
 		cmd->bufflen = 0;
 	}
-- 
1.8.1.2

Re: [PATCH] tcm_qla2xxx: Fix residual for underrun commands that fail

[Nicholas A. Bellinger]

Hi Roland,

On Wed, 2013-06-05 at 09:54 -0700, Roland Dreier wrote:
> From: Roland Dreier <roland@purestorage.com>
> 
> Suppose an initiator sends a DATA IN command with an allocation length
> shorter than the FC transfer length -- we get a target message like
> 
>     TARGET_CORE[qla2xxx]: Expected Transfer Length: 256 does not match SCSI CDB Length: 0 for SAM Opcode: 0x12
> 
> In that case, the target core adjusts the data_length and sets
> se_cmd->residual_count for the underrun.  But now suppose that command
> fails and we end up in tcm_qla2xxx_queue_status() -- that function
> unconditionally overwrites residual_count with the already adjusted
> data_length, and the initiator will burp with a message like
> 
>     qla2xxx [0000:00:06.0]-301d:0: Dropped frame(s) detected (0x100 of 0x100 bytes).
> 
> Fix this by adding on to the existing underflow residual count instead.
> 
> Signed-off-by: Roland Dreier <roland@purestorage.com>
> ---

Apologies for the delay, finally catching up on the backlog..

Applied to target-pending/master, with a CC' to stable.

Also including QLogic folks on the CC'.

Thanks!

--nab

>  drivers/scsi/qla2xxx/tcm_qla2xxx.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/qla2xxx/tcm_qla2xxx.c b/drivers/scsi/qla2xxx/tcm_qla2xxx.c
> index 7a3870f..66b0b26 100644
> --- a/drivers/scsi/qla2xxx/tcm_qla2xxx.c
> +++ b/drivers/scsi/qla2xxx/tcm_qla2xxx.c
> @@ -688,8 +688,12 @@ static int tcm_qla2xxx_queue_status(struct se_cmd *se_cmd)
>  		 * For FCP_READ with CHECK_CONDITION status, clear cmd->bufflen
>  		 * for qla_tgt_xmit_response LLD code
>  		 */
> +		if (se_cmd->se_cmd_flags & SCF_OVERFLOW_BIT) {
> +			se_cmd->se_cmd_flags &= ~SCF_OVERFLOW_BIT;
> +			se_cmd->residual_count = 0;
> +		}
>  		se_cmd->se_cmd_flags |= SCF_UNDERFLOW_BIT;
> -		se_cmd->residual_count = se_cmd->data_length;
> +		se_cmd->residual_count += se_cmd->data_length;
>  
>  		cmd->bufflen = 0;
>  	}