linux-kernel - [PATCH V3 6/7] lib/group_cpus: allow to group cpus in case of !CONFIG

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Date:   Tue, 28 Sep 2021 08:55:57 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Thomas Gleixner <tglx@...utronix.de>, Jens Axboe <axboe@...nel.dk>
Cc:     linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        Christoph Hellwig <hch@....de>, Ming Lei <ming.lei@...hat.com>
Subject: [PATCH V3 6/7] lib/group_cpus: allow to group cpus in case of !CONFIG_SMP

Allows group_cpus_evenly() to be called in case of !CONFIG_SMP by simply
assigning all CPUs into the 1st group.

Signed-off-by: Ming Lei <ming.lei@...hat.com>
---
 lib/Makefile     |  2 +-
 lib/group_cpus.c | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/lib/Makefile b/lib/Makefile
index ff1cbe4958a1..3dbdc7f01215 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -338,7 +338,7 @@ obj-$(CONFIG_SBITMAP) += sbitmap.o
 
 obj-$(CONFIG_PARMAN) += parman.o
 
-obj-$(CONFIG_SMP) += group_cpus.o
+obj-y += group_cpus.o
 
 # GCC library routines
 obj-$(CONFIG_GENERIC_LIB_ASHLDI3) += ashldi3.o
diff --git a/lib/group_cpus.c b/lib/group_cpus.c
index f7165b38c9d0..b34f7d309f9c 100644
--- a/lib/group_cpus.c
+++ b/lib/group_cpus.c
@@ -327,6 +327,7 @@ static int __group_cpus_evenly(unsigned int startgrp, unsigned int numgrps,
 	return done;
 }
 
+#ifdef CONFIG_SMP
 /**
  * group_cpus_evenly - Group all CPUs evenly per NUMA/CPU locality
  * @numgrps: number of groups
@@ -411,4 +412,17 @@ struct cpumask *group_cpus_evenly(unsigned int numgrps)
 	}
 	return masks;
 }
+#else
+struct cpumask *group_cpus_evenly(unsigned int numgrps)
+{
+	struct cpumask *masks = kcalloc(numgrps, sizeof(*masks), GFP_KERNEL);
+
+	if (!masks)
+		return NULL;
+
+	/* assign all CPUs(cpu 0) to the 1st group only */
+	cpumask_copy(&masks[0], cpu_possible_mask);
+	return masks;
+}
+#endif
 EXPORT_SYMBOL_GPL(group_cpus_evenly);
-- 
2.31.1