commit 
59ac9c078141b8fd0186c0b18660a1b2c24e724e upstream.
This patch fixes zero-length READ and WRITE handling in target/FILEIO,
which was broken a long time back by:
Since:
  commit 
d81cb44726f050d7cf1be4afd9cb45d153b52066
  Author: Paolo Bonzini <pbonzini@redhat.com>
  Date:   Mon Sep 17 16:36:11 2012 -0700
      target: go through normal processing for all zero-length commands
which moved zero-length READ and WRITE completion out of target-core,
to doing submission into backend driver code.
To address this, go ahead and invoke target_complete_cmd() for any
non negative return value in fd_do_rw().
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Andy Grover <agrover@redhat.com>
Cc: David Disseldorp <ddiss@suse.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
        if (ret < 0)
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
 
-       if (ret)
-               target_complete_cmd(cmd, SAM_STAT_GOOD);
+       target_complete_cmd(cmd, SAM_STAT_GOOD);
        return 0;
 }