target: Fix residual overflow handling in target_complete_cmd_with_length

This patch fixes residual overflow handling to correctly set the
residual_count using SPDTL, instead of SCSI Allocation Length.

Allocation Length is the maximum value of the SPDTL and not substitute
for it, hence it shouldn’t be used to calculate ResidualCount except for
cases where SPDTL > Allocation Length and Data is truncated (in that
case both Alloc Len and SPDTL are same). (SPC 5r01 Section 4.2.5.6).

Thanks to Ajay Nair in assisting with this patch.

Signed-off-by: Sumit Rai <sumitrai96@gmail.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 42c2a44b83ddbcb3183e92ec86be9ec38024d38e..6094a6beddde9fb5d045644b6b11b32e6bd149c1 100644 (file)
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -754,7 +754,15 @@ EXPORT_SYMBOL(target_complete_cmd);
 
 void target_complete_cmd_with_length(struct se_cmd *cmd, u8 scsi_status, int length)
 {
-       if (scsi_status == SAM_STAT_GOOD && length < cmd->data_length) {
+       if (scsi_status != SAM_STAT_GOOD) {
+               return;
+       }
+
+       /*
+        * Calculate new residual count based upon length of SCSI data
+        * transferred.
+        */
+       if (length < cmd->data_length) {
                if (cmd->se_cmd_flags & SCF_UNDERFLOW_BIT) {
                        cmd->residual_count += cmd->data_length - length;
                } else {
@@ -763,6 +771,12 @@ void target_complete_cmd_with_length(struct se_cmd *cmd, u8 scsi_status, int len
                }
 
                cmd->data_length = length;
+       } else if (length > cmd->data_length) {
+               cmd->se_cmd_flags |= SCF_OVERFLOW_BIT;
+               cmd->residual_count = length - cmd->data_length;
+       } else {
+               cmd->se_cmd_flags &= ~(SCF_OVERFLOW_BIT | SCF_UNDERFLOW_BIT);
+               cmd->residual_count = 0;
        }
 
        target_complete_cmd(cmd, scsi_status);