block: add REQ_FLUSH_SEQ

rq == &q->flush_rq was used to determine whether a rq is part of a
flush sequence, which worked because all requests in a flush sequence
were sequenced using the single dedicated request.  This is about to
change, so introduce REQ_FLUSH_SEQ flag to distinguish flush sequence
requests.

This patch doesn't cause any behavior change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

3 files changed, 4 insertions, 3 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 4ce953f1b390..fc7d8ad76f44 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -136,7 +136,7 @@ static void req_bio_endio(struct request *rq, struct bio *bio,
 {
         struct request_queue *q = rq->q;
 
-        if (&q->flush_rq != rq) {
+        if (!(rq->cmd_flags & REQ_FLUSH_SEQ)) {
                 if (error)
                         clear_bit(BIO_UPTODATE, &bio->bi_flags);
                 else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
@@ -1789,7 +1789,7 @@ static void blk_account_io_done(struct request *req)
          * normal IO on queueing nor completion.  Accounting the
          * containing request is enough.
          */
-        if (blk_do_io_stat(req) && req != &req->q->flush_rq) {
+        if (blk_do_io_stat(req) && !(req->cmd_flags & REQ_FLUSH_SEQ)) {
                 unsigned long duration = jiffies - req->start_time;
                 const int rw = rq_data_dir(req);
                 struct hd_struct *part;
diff --git a/block/blk-flush.c b/block/blk-flush.c
index 54b123d6563e..8592869bcbe7 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -130,6 +130,7 @@ static struct request *queue_next_fseq(struct request_queue *q)
                 BUG();
         }
 
+        rq->cmd_flags |= REQ_FLUSH_SEQ;
         elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
         return rq;
 }
diff --git a/block/blk.h b/block/blk.h
index 2db8f32838e7..9d2ee8f4d9af 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -61,7 +61,7 @@ static inline struct request *__elv_next_request(struct request_queue *q)
                 while (!list_empty(&q->queue_head)) {
                         rq = list_entry_rq(q->queue_head.next);
                         if (!(rq->cmd_flags & (REQ_FLUSH | REQ_FUA)) ||
-                            rq == &q->flush_rq)
+                            (rq->cmd_flags & REQ_FLUSH_SEQ))
                                 return rq;
                         rq = blk_do_flush(q, rq);
                         if (rq)