[SCSI] libsas: fix taskfile corruption in sas_ata_qc_fill_rtf

fill_result_tf() grabs the taskfile flags from the originating qc which
sas_ata_qc_fill_rtf() promptly overwrites.  The presence of an
ata_taskfile in the sata_device makes it tempting to just copy the full
contents in sas_ata_qc_fill_rtf().  However, libata really only wants
the fis contents and expects the other portions of the taskfile to not
be touched by ->qc_fill_rtf.  To that end store a fis buffer in the
sata_device and use ata_tf_from_fis() like every other ->qc_fill_rtf()
implementation.

Cc: <stable@vger.kernel.org>
Reported-by: Praveen Murali <pmurali@logicube.com>
Tested-by: Praveen Murali <pmurali@logicube.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
diff --git a/include/scsi/libsas.h b/include/scsi/libsas.h
index f4f1c96..10ce74f 100644
--- a/include/scsi/libsas.h
+++ b/include/scsi/libsas.h
@@ -163,6 +163,8 @@
         ATAPI_COMMAND_SET = 1,
 };
 
+#define ATA_RESP_FIS_SIZE 24
+
 struct sata_device {
         enum   ata_command_set command_set;
         struct smp_resp        rps_resp; /* report_phy_sata_resp */
@@ -171,7 +173,7 @@
 
 	struct ata_port *ap;
 	struct ata_host ata_host;
-	struct ata_taskfile tf;
+	u8     fis[ATA_RESP_FIS_SIZE];
 };
 
 enum {
@@ -537,7 +539,7 @@
  */
 struct ata_task_resp {
 	u16  frame_len;
-	u8   ending_fis[24];	  /* dev to host or data-in */
+	u8   ending_fis[ATA_RESP_FIS_SIZE];	  /* dev to host or data-in */
 };
 
 #define SAS_STATUS_BUF_SIZE 96