add a struct request pointer to the request structure

This adds a struct request pointer to the request structure for the
second data phase (bidi for now). A request queue supporting bidi
requests sets QUEUE_FLAG_BIDI. This prevents sending bidi requests to
a non-bidi queue.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

2 files changed, 6 insertions, 0 deletions

diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index ef42bb2b12b6..11e4235d0b0c 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -256,6 +256,7 @@ static void rq_init(request_queue_t *q, struct request *rq)
         rq->end_io = NULL;
         rq->end_io_data = NULL;
         rq->completion_data = NULL;
+        rq->next_rq = NULL;
 }
 
 /**
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 24b474e05a44..b32564a1e105 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -317,6 +317,9 @@ struct request {
          */
         rq_end_io_fn *end_io;
         void *end_io_data;
+
+        /* for bidi */
+        struct request *next_rq;
 };
 
 /*
@@ -486,6 +489,7 @@ struct request_queue
 #define QUEUE_FLAG_REENTER      6       /* Re-entrancy avoidance */
 #define QUEUE_FLAG_PLUGGED      7       /* queue is plugged */
 #define QUEUE_FLAG_ELVSWITCH    8       /* don't use elevator, just do FIFO */
+#define QUEUE_FLAG_BIDI         9       /* queue supports bidi requests */
 
 enum {
         /*
@@ -550,6 +554,7 @@ enum {
 #define blk_sorted_rq(rq)       ((rq)->cmd_flags & REQ_SORTED)
 #define blk_barrier_rq(rq)      ((rq)->cmd_flags & REQ_HARDBARRIER)
 #define blk_fua_rq(rq)          ((rq)->cmd_flags & REQ_FUA)
+#define blk_bidi_rq(rq)         ((rq)->next_rq != NULL)
 
 #define list_entry_rq(ptr)      list_entry((ptr), struct request, queuelist)