target: Don't return an error status for 0-length READ and WRITE

IO commands with a TRANSFER LENGTH of 0 are not an error; for example,
for READ (10) and WRITE (10), SBC-3 says:

    A TRANSFER LENGTH field set to zero specifies that no logical blocks
    shall be read. This condition shall not be considered an error.

In case we have nothing to do, just complete the command with good status.

Signed-off-by: Roland Dreier <roland@purestorage.com>
Cc: stable@kernel.org
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 0bdb6badbf99689adb4ac8f0f4f849f6c0d1606d..1b760a0b110974970ff9df92e64651a50b76ac9a 100644 (file)
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -3770,8 +3770,15 @@ int transport_generic_new_cmd(struct se_cmd *cmd)
                task_cdbs = transport_allocate_control_task(cmd);
        }
 
-       if (task_cdbs <= 0)
+       if (task_cdbs < 0)
                goto out_fail;
+       else if (!task_cdbs && (cmd->se_cmd_flags & SCF_SCSI_DATA_SG_IO_CDB)) {
+               cmd->t_state = TRANSPORT_COMPLETE;
+               atomic_set(&cmd->t_transport_active, 1);
+               INIT_WORK(&cmd->work, target_complete_ok_work);
+               queue_work(target_completion_wq, &cmd->work);
+               return 0;
+       }
 
        if (set_counts) {
                atomic_inc(&cmd->t_fe_count);