linux-kernel - [PATCH 1/7] cpumask: add cpumask_clear

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Message-ID: <20250604193947.11834-2-yury.norov@gmail.com>
Date: Wed,  4 Jun 2025 15:39:37 -0400
From: Yury Norov <yury.norov@...il.com>
To: Dennis Dalessandro <dennis.dalessandro@...nelisnetworks.com>,
	Jason Gunthorpe <jgg@...pe.ca>,
	Leon Romanovsky <leon@...nel.org>,
	Yury Norov <yury.norov@...il.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	linux-rdma@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/7] cpumask: add cpumask_clear_cpus()

From: "Yury Norov [NVIDIA]" <yury.norov@...il.com>

When user wants to clear a range in cpumask, the only option the API
provides now is a for-loop, like:

	for_each_cpu_from(cpu, mask) {
		if (cpu >= ncpus)
			break;
		__cpumask_clear_cpu(cpu, mask);
	}

In the bitmap API we have bitmap_clear() for that, which is
significantly faster than a for-loop. Propagate it to cpumasks.

Signed-off-by: Yury Norov [NVIDIA] <yury.norov@...il.com>
---
 include/linux/cpumask.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 7ae80a7ca81e..ede95bbe8b80 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -609,6 +609,18 @@ void __cpumask_set_cpu(unsigned int cpu, struct cpumask *dstp)
 	__set_bit(cpumask_check(cpu), cpumask_bits(dstp));
 }
 
+/**
+ * cpumask_clear_cpus - clear cpus in a cpumask
+ * @dstp:  the cpumask pointer
+ * @cpu:   cpu number (< nr_cpu_ids)
+ * @ncpus: number of cpus to clear (< nr_cpu_ids)
+ */
+static __always_inline void cpumask_clear_cpus(struct cpumask *dstp,
+						unsigned int cpu, unsigned int ncpus)
+{
+	cpumask_check(cpu + ncpus - 1);
+	bitmap_clear(cpumask_bits(dstp), cpumask_check(cpu), ncpus);
+}
 
 /**
  * cpumask_clear_cpu - clear a cpu in a cpumask
-- 
2.43.0