linux-kernel - [RFC PATCH bitmap-for-next 2/4] lib/cpumask: Fix cpumask_check() warning in cpumask_next

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Date:   Thu,  6 Oct 2022 13:21:10 +0100
From:   Valentin Schneider <vschneid@...hat.com>
To:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Jens Axboe <axboe@...nel.dk>, Yury Norov <yury.norov@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: [RFC PATCH bitmap-for-next 2/4] lib/cpumask: Fix cpumask_check() warning in cpumask_next_wrap*()

Invoking cpumask_next*() with n==nr_cpu_ids-1 triggers a warning as there
are (obviously) no more valid CPU ids after that. This is however undesired
for the cpumask_next_wrap*() family which needs to wrap around reaching
this condition.

Don't invoke cpumask_next*() when n==nr_cpu_ids, go for the wrapping (if
any) instead.

NOTE: this only fixes the NR_CPUS>1 variants.

Signed-off-by: Valentin Schneider <vschneid@...hat.com>
---
 lib/cpumask.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/cpumask.c b/lib/cpumask.c
index 6e576485c84f..f8174fa3d752 100644
--- a/lib/cpumask.c
+++ b/lib/cpumask.c
@@ -12,11 +12,11 @@
 	unsigned int next;						\
 									\
 again:									\
-	next = (FETCH_NEXT);						\
+	next = n == nr_cpu_ids - 1 ? nr_cpu_ids : (FETCH_NEXT);		\
 									\
 	if (wrap && n < start && next >= start) {			\
-		next = nr_cpumask_bits;					\
-	} else if (next >= nr_cpumask_bits) {				\
+		next = nr_cpu_ids;					\
+	} else if (next >= nr_cpu_ids) {				\
 		wrap = true;						\
 		n = -1;							\
 		goto again;						\
-- 
2.31.1