xen: Union the blkif_request request specific fields

Prepare for extending the block device ring to allow request
specific fields, by moving the request specific fields for
reads, writes and barrier requests to a union member.

Acked-by: Jens Axboe <jaxboe@fusionio.com>
Signed-off-by: Owen Smith <owen.smith@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 11 insertions, 5 deletions

diff --git a/include/xen/interface/io/blkif.h b/include/xen/interface/io/blkif.h
index c2d1fa4dc1e..e4f743cfa15 100644
--- a/include/xen/interface/io/blkif.h
+++ b/include/xen/interface/io/blkif.h
@@ -51,11 +51,7 @@ typedef uint64_t blkif_sector_t;
  */
 #define BLKIF_MAX_SEGMENTS_PER_REQUEST 11
 
-struct blkif_request {
-        uint8_t        operation;    /* BLKIF_OP_???                         */
-        uint8_t        nr_segments;  /* number of segments                   */
-        blkif_vdev_t   handle;       /* only for read/write requests         */
-        uint64_t       id;           /* private guest value, echoed in resp  */
+struct blkif_request_rw {
         blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
         struct blkif_request_segment {
                 grant_ref_t gref;        /* reference to I/O buffer frame        */
@@ -65,6 +61,16 @@ struct blkif_request {
         } seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 };
 
+struct blkif_request {
+        uint8_t        operation;    /* BLKIF_OP_???                         */
+        uint8_t        nr_segments;  /* number of segments                   */
+        blkif_vdev_t   handle;       /* only for read/write requests         */
+        uint64_t       id;           /* private guest value, echoed in resp  */
+        union {
+                struct blkif_request_rw rw;
+        } u;
+};
+
 struct blkif_response {
         uint64_t        id;              /* copied from request */
         uint8_t         operation;       /* copied from request */