tcm_qla2xxx: Fix residual for underrun commands that fail

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>
Cc: Giridhar Malavali <giridhar.malavali@qlogic.com>
Cc: Chad Dupuis <chad.dupuis@qlogic.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 5 insertions, 1 deletions

diff --git a/drivers/scsi/qla2xxx/tcm_qla2xxx.c b/drivers/scsi/qla2xxx/tcm_qla2xxx.c
index 7a3870f385f6..66b0b26a1381 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;
         }