[SRU C][PATCH v2 3/6] blk-wbt: use wq_has_sleeper() for wq active check

[Mauricio Faria de Oliveira]

From: Jens Axboe <axboe at kernel.dk>

BugLink: https://bugs.launchpad.net/bugs/1810998

We need the memory barrier before checking the list head,
use the appropriate helper for this. The matching queue
side memory barrier is provided by set_current_state().

Tested-by: Anchal Agarwal <anchalag at amazon.com>
Signed-off-by: Jens Axboe <axboe at kernel.dk>
(backported from commit b78820937b4762b7d30b807d7156bec1d89e4dd3)
[mfo: backport:
 - hunk 3: s/rq_wait_inc_below(rqw/atomic_inc_below(&rqw->inflight/]
Signed-off-by: Mauricio Faria de Oliveira <mfo at canonical.com>
---
 block/blk-wbt.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index 84e5cefbb3bb..08472c1a7858 100644
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -139,7 +139,7 @@ static void rwb_wake_all(struct rq_wb *rwb)
 	for (i = 0; i < WBT_NUM_RWQ; i++) {
 		struct rq_wait *rqw = &rwb->rq_wait[i];
 
-		if (waitqueue_active(&rqw->wait))
+		if (wq_has_sleeper(&rqw->wait))
 			wake_up_all(&rqw->wait);
 	}
 }
@@ -182,7 +182,7 @@ void __wbt_done(struct rq_wb *rwb, enum wbt_flags wb_acct)
 	if (inflight && inflight >= limit)
 		return;
 
-	if (waitqueue_active(&rqw->wait)) {
+	if (wq_has_sleeper(&rqw->wait)) {
 		int diff = limit - inflight;
 
 		if (!inflight || diff >= rwb->wb_background / 2)
@@ -552,8 +552,8 @@ static void __wbt_wait(struct rq_wb *rwb, enum wbt_flags wb_acct,
 	struct rq_wait *rqw = get_rq_wait(rwb, wb_acct);
 	DECLARE_WAITQUEUE(wait, current);
 
-	if (!waitqueue_active(&rqw->wait)
-		&& atomic_inc_below(&rqw->inflight, get_limit(rwb, rw)))
+	if (!wq_has_sleeper(&rqw->wait) &&
+	    atomic_inc_below(&rqw->inflight, get_limit(rwb, rw)))
 		return;
 
 	add_wait_queue_exclusive(&rqw->wait, &wait);
-- 
2.17.1