Re: [PATCH 1/2] scsi: target: core: Add cmd length set before cmd complete

TCM doesn't properly handle underflow case for service actions. One way to
prevent it is to always complete command with
target_complete_cmd_with_length, however it requires access to data_sg,
which is not always available.

This change introduces target_set_cmd_data_length function which allows to
set command data length before completing it.

Signed-off-by: Aleksandr Miloserdov <redacted>
Reviewed-by: Roman Bolshakov <redacted>
---
  drivers/target/target_core_transport.c | 15 +++++++++++----
  include/target/target_core_backend.h   |  1 +
  2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index fca4bd079d02..c98540355512 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c

@@ -879,11 +879,9 @@ void target_complete_cmd(struct se_cmd *cmd, u8 scsi_status)
  }
  EXPORT_SYMBOL(target_complete_cmd);
  
-void target_complete_cmd_with_length(struct se_cmd *cmd, u8 scsi_status, int length)
+void target_set_cmd_data_length(struct se_cmd *cmd, int length)
  {
-	if ((scsi_status == SAM_STAT_GOOD ||
-	     cmd->se_cmd_flags & SCF_TREAT_READ_AS_NORMAL) &&
-	    length < cmd->data_length) {
+	if (length < cmd->data_length) {
  		if (cmd->se_cmd_flags & SCF_UNDERFLOW_BIT) {
  			cmd->residual_count += cmd->data_length - length;
  		} else {

@@ -893,6 +891,15 @@ void target_complete_cmd_with_length(struct se_cmd *cmd, u8 scsi_status, int len
  
  		cmd->data_length = length;
  	}
+}
+EXPORT_SYMBOL(target_set_cmd_data_length);
+
+void target_complete_cmd_with_length(struct se_cmd *cmd, u8 scsi_status, int length)
+{
+	if (scsi_status == SAM_STAT_GOOD ||
+	    cmd->se_cmd_flags & SCF_TREAT_READ_AS_NORMAL) {
+		target_set_cmd_data_length(cmd, length);
+	}
  
  	target_complete_cmd(cmd, scsi_status);
  }

diff --git a/include/target/target_core_backend.h b/include/target/target_core_backend.h
index 6336780d83a7..ce2fba49c95d 100644
--- a/include/target/target_core_backend.h
+++ b/include/target/target_core_backend.h

@@ -72,6 +72,7 @@ int	transport_backend_register(const struct target_backend_ops *);
  void	target_backend_unregister(const struct target_backend_ops *);
  
  void	target_complete_cmd(struct se_cmd *, u8);
+void	target_set_cmd_data_length(struct se_cmd *, int);
  void	target_complete_cmd_with_length(struct se_cmd *, u8, int);
  
  void	transport_copy_sense_to_cmd(struct se_cmd *, unsigned char *);