[PATCH 5/6] blk-mq: remove REQ_ATOM_COMPLETE usages from blk-mq

[Tejun Heo]

After the recent updates to use generation number and state based
synchronization, blk-mq no longer depends on REQ_ATOM_COMPLETE for
anything.

Remove all REQ_ATOM_COMPLETE usages.  This removes atomic bitops from
hot paths too.  The next patch will push further along this direction
and include simple performance test results.

Signed-off-by: Tejun Heo <t...@kernel.org>
---
 block/blk-mq.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 0267040..4ebac33 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -596,14 +596,12 @@ void blk_mq_complete_request(struct request *rq)
         */
        if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {
                rcu_read_lock();
-               if (blk_mq_rq_aborted_gstate(rq) != rq->gstate &&
-                   !blk_mark_rq_complete(rq))
+               if (blk_mq_rq_aborted_gstate(rq) != rq->gstate)
                        __blk_mq_complete_request(rq);
                rcu_read_unlock();
        } else {
                srcu_idx = srcu_read_lock(hctx->queue_rq_srcu);
-               if (blk_mq_rq_aborted_gstate(rq) != rq->gstate &&
-                   !blk_mark_rq_complete(rq))
+               if (blk_mq_rq_aborted_gstate(rq) != rq->gstate)
                        __blk_mq_complete_request(rq);
                srcu_read_unlock(hctx->queue_rq_srcu, srcu_idx);
        }
@@ -650,8 +648,6 @@ void blk_mq_start_request(struct request *rq)
        write_seqcount_end(&rq->gstate_seqc);
 
        set_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
-       if (test_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags))
-               clear_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags);
 
        if (q->dma_drain_size && blk_rq_bytes(rq)) {
                /*
@@ -862,8 +858,7 @@ static void blk_mq_terminate_expired(struct blk_mq_hw_ctx 
*hctx,
         * now guaranteed to see @rq->aborted_gstate and yield.  If
         * @rq->aborted_gstate still matches @rq->gstate, @rq is ours.
         */
-       if (READ_ONCE(rq->gstate) == rq->aborted_gstate &&
-           !blk_mark_rq_complete(rq))
+       if (READ_ONCE(rq->gstate) == rq->aborted_gstate)
                blk_mq_rq_timed_out(rq, reserved);
 }
 
-- 
2.9.5