linux-kernel - [PATCH 1/3] bitmap: generalize node

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Message-ID: <20250604212125.25656-2-yury.norov@gmail.com>
Date: Wed,  4 Jun 2025 17:21:21 -0400
From: Yury Norov <yury.norov@...il.com>
To: linux-kernel@...r.kernel.org,
	Yury Norov <yury.norov@...il.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	John Stultz <jstultz@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Stephen Boyd <sboyd@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 1/3] bitmap: generalize node_random()

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

Generalize node_random and make it available to general bitmaps and
cpumasks users.

Signed-off-by: Yury Norov [NVIDIA] <yury.norov@...il.com>
---
 include/linux/find.h     |  2 ++
 include/linux/nodemask.h | 16 +---------------
 lib/find_bit.c           | 17 ++++++++++++++++-
 3 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/include/linux/find.h b/include/linux/find.h
index 5a2c267ea7f9..98c61838002c 100644
--- a/include/linux/find.h
+++ b/include/linux/find.h
@@ -44,6 +44,8 @@ unsigned long _find_next_bit_le(const unsigned long *addr, unsigned
 				long size, unsigned long offset);
 #endif
 
+unsigned long find_random_bit(const unsigned long *addr, unsigned long size);
+
 #ifndef find_next_bit
 /**
  * find_next_bit - find the next set bit in a memory region
diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h
index f08ae71585fa..1cedc7132b76 100644
--- a/include/linux/nodemask.h
+++ b/include/linux/nodemask.h
@@ -492,21 +492,7 @@ static __always_inline int num_node_state(enum node_states state)
 static __always_inline int node_random(const nodemask_t *maskp)
 {
 #if defined(CONFIG_NUMA) && (MAX_NUMNODES > 1)
-	int w, bit;
-
-	w = nodes_weight(*maskp);
-	switch (w) {
-	case 0:
-		bit = NUMA_NO_NODE;
-		break;
-	case 1:
-		bit = first_node(*maskp);
-		break;
-	default:
-		bit = find_nth_bit(maskp->bits, MAX_NUMNODES, get_random_u32_below(w));
-		break;
-	}
-	return bit;
+	return find_random_bit(maskp->bits, MAX_NUMNODES);
 #else
 	return 0;
 #endif
diff --git a/lib/find_bit.c b/lib/find_bit.c
index 06b6342aa3ae..2118ea23bed8 100644
--- a/lib/find_bit.c
+++ b/lib/find_bit.c
@@ -18,6 +18,7 @@
 #include <linux/math.h>
 #include <linux/minmax.h>
 #include <linux/swab.h>
+#include <linux/random.h>
 
 /*
  * Common helper for find_bit() function family
@@ -287,7 +288,21 @@ unsigned long _find_next_bit_le(const unsigned long *addr,
 	return FIND_NEXT_BIT(addr[idx], swab, size, offset);
 }
 EXPORT_SYMBOL(_find_next_bit_le);
-
 #endif
 
+unsigned long find_random_bit(const unsigned long *addr, unsigned long size)
+{
+	int w = bitmap_weight(addr, size);
+
+	switch (w) {
+	case 0:
+		return size;
+	case 1:
+		return find_first_bit(addr, size);
+	default:
+		return find_nth_bit(addr, size, get_random_u32_below(w));
+	}
+}
+EXPORT_SYMBOL(find_random_bit);
+
 #endif /* __BIG_ENDIAN */
-- 
2.43.0