linux-kernel - [PATCH 5/6] blk-mq: remove REQ_ATOM

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Message-Id: <20171209192525.982030-6-tj@kernel.org>
Date:   Sat,  9 Dec 2017 11:25:24 -0800
From:   Tejun Heo <tj@...nel.org>
To:     axboe@...nel.dk
Cc:     linux-kernel@...r.kernel.org, oleg@...hat.com,
        peterz@...radead.org, kernel-team@...com, osandov@...com,
        Tejun Heo <tj@...nel.org>
Subject: [PATCH 5/6] blk-mq: remove REQ_ATOM_COMPLETE usages from blk-mq

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 <tj@...nel.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