linux-kernel - [PATCH 2/6] sbitmap: fix round-robin non-wrap find with hint

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Message-ID: <20230720094555.1397621-3-chengming.zhou@linux.dev>
Date:   Thu, 20 Jul 2023 17:45:51 +0800
From:   chengming.zhou@...ux.dev
To:     axboe@...nel.dk, osandov@...com, ming.lei@...hat.com,
        kbusch@...nel.org, krisman@...e.de
Cc:     linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        zhouchengming@...edance.com
Subject: [PATCH 2/6] sbitmap: fix round-robin non-wrap find with hint > 0

From: Chengming Zhou <zhouchengming@...edance.com>

If we have alloc_hint > 0 and don't wrap, we need to recheck
sb->map[index] with hint == 0 to exhaust the map.

Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>
---
 lib/sbitmap.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index 5ed6c2adf58e..ccb96d1f92ba 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -192,10 +192,18 @@ static int sbitmap_find_bit(struct sbitmap *sb,
 			    unsigned int alloc_hint,
 			    bool wrap)
 {
+	unsigned int map_nr = sb->map_nr;
 	unsigned int i;
 	int nr = -1;
 
-	for (i = 0; i < sb->map_nr; i++) {
+	/*
+	 * If we have alloc_hint > 0 and don't wrap, we need to
+	 * recheck sb->map[index] with hint == 0 to exhaust the map.
+	 */
+	if (alloc_hint && !wrap)
+		map_nr += 1;
+
+	for (i = 0; i < map_nr; i++) {
 		nr = sbitmap_find_bit_in_word(&sb->map[index],
 					      min_t(unsigned int,
 						    __map_depth(sb, index),
-- 
2.41.0