linux-kernel - [PATCH 6/9] block/pktdvd: switch congestion waiting to ___wait_var

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Message-ID: <20240819053605.11706-7-neilb@suse.de>
Date: Mon, 19 Aug 2024 15:20:40 +1000
From: NeilBrown <neilb@...e.de>
To: Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: [PATCH 6/9] block/pktdvd: switch congestion waiting to ___wait_var_event()

Rather than having an open-coded wait event loop, use
__var_wait_event().
This fixes a bug as the existing loop doesn't call finish_wait().

Also add missing memory barrier before wake_up_var().

Signed-off-by: NeilBrown <neilb@...e.de>
---
 drivers/block/pktcdvd.c | 23 ++++++++++-------------
 1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
index 7cece5884b9c..273fbe05d80f 100644
--- a/drivers/block/pktcdvd.c
+++ b/drivers/block/pktcdvd.c
@@ -1210,6 +1210,7 @@ static int pkt_handle_queue(struct pktcdvd_device *pd)
 	if (pd->congested &&
 	    pd->bio_queue_size <= pd->write_congestion_off) {
 		pd->congested = false;
+		smp_mb();
 		wake_up_var(&pd->congested);
 	}
 	spin_unlock(&pd->lock);
@@ -2383,20 +2384,16 @@ static void pkt_make_request_write(struct bio *bio)
 	spin_lock(&pd->lock);
 	if (pd->write_congestion_on > 0
 	    && pd->bio_queue_size >= pd->write_congestion_on) {
-		struct wait_bit_queue_entry wqe;
 
-		init_wait_var_entry(&wqe, &pd->congested, 0);
-		for (;;) {
-			prepare_to_wait_event(__var_waitqueue(&pd->congested),
-					      &wqe.wq_entry,
-					      TASK_UNINTERRUPTIBLE);
-			if (pd->bio_queue_size <= pd->write_congestion_off)
-				break;
-			pd->congested = true;
-			spin_unlock(&pd->lock);
-			schedule();
-			spin_lock(&pd->lock);
-		}
+		___wait_var_event(&pd->congested,
+				  pd->bio_queue_size <= pd->write_congestion_off,
+				  TASK_UNINTERRUPTIBLE, 0, 0,
+				  ({ pd->congested = true;
+				    spin_unlock(&pd->lock);
+				    schedule();
+				    spin_lock(&pd->lock);
+				  })
+		);
 	}
 	spin_unlock(&pd->lock);
 
-- 
2.44.0