From 77bcc673f6f8ce1f21b1b22f04062dcd19ebd034 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@google.com>
Date: Mon, 13 Mar 2023 16:39:30 +0000
Subject: [PATCH] Revert "sbitmap: Try each queue to wake up at least one
 waiter"

This reverts commit ff9571a4dee91f0ca50bba996f470eb382a4fc3a.

It breaks the ABI right now, but will be brought back at the next ABI
break as it will be needed for Android systems.

Bug: 161946584
Change-Id: I484106fa249e20cf12d748f005c3481947efd735
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
---
 lib/sbitmap.c | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index c515072eca29..443accfe685d 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -555,12 +555,12 @@ void sbitmap_queue_min_shallow_depth(struct sbitmap_queue *sbq,
 }
 EXPORT_SYMBOL_GPL(sbitmap_queue_min_shallow_depth);
 
-static void __sbitmap_queue_wake_up(struct sbitmap_queue *sbq, int nr)
+static struct sbq_wait_state *sbq_wake_ptr(struct sbitmap_queue *sbq)
 {
 	int i, wake_index;
 
 	if (!atomic_read(&sbq->ws_active))
-		return;
+		return NULL;
 
 	wake_index = atomic_read(&sbq->wake_index);
 	for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
@@ -574,22 +574,20 @@ static void __sbitmap_queue_wake_up(struct sbitmap_queue *sbq, int nr)
 		 */
 		wake_index = sbq_index_inc(wake_index);
 
-		/*
-		 * It is sufficient to wake up at least one waiter to
-		 * guarantee forward progress.
-		 */
-		if (waitqueue_active(&ws->wait) &&
-		    wake_up_nr(&ws->wait, nr))
-			break;
+		if (waitqueue_active(&ws->wait)) {
+			if (wake_index != atomic_read(&sbq->wake_index))
+				atomic_set(&sbq->wake_index, wake_index);
+			return ws;
+		}
 	}
 
-	if (wake_index != atomic_read(&sbq->wake_index))
-		atomic_set(&sbq->wake_index, wake_index);
+	return NULL;
 }
 
 void sbitmap_queue_wake_up(struct sbitmap_queue *sbq, int nr)
 {
 	unsigned int wake_batch = READ_ONCE(sbq->wake_batch);
+	struct sbq_wait_state *ws = NULL;
 	unsigned int wakeups;
 
 	if (!atomic_read(&sbq->ws_active))
@@ -601,10 +599,16 @@ void sbitmap_queue_wake_up(struct sbitmap_queue *sbq, int nr)
 	do {
 		if (atomic_read(&sbq->completion_cnt) - wakeups < wake_batch)
 			return;
+
+		if (!ws) {
+			ws = sbq_wake_ptr(sbq);
+			if (!ws)
+				return;
+		}
 	} while (!atomic_try_cmpxchg(&sbq->wakeup_cnt,
 				     &wakeups, wakeups + wake_batch));
 
-	__sbitmap_queue_wake_up(sbq, wake_batch);
+	wake_up_nr(&ws->wait, wake_batch);
 }
 EXPORT_SYMBOL_GPL(sbitmap_queue_wake_up);