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Message-ID: <20250910210850.404834-2-yury.norov@gmail.com>
Date: Wed, 10 Sep 2025 17:08:46 -0400
From: Yury Norov <yury.norov@...il.com>
To: Thomas Gleixner <tglx@...utronix.de>,
Yury Norov <yury.norov@...il.com>,
Rasmus Villemoes <linux@...musvillemoes.dk>,
linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] bitmap: cpumask: introduce and_andnot search helper and iterator
From: "Yury Norov (NVIDIA)" <yury.norov@...il.com>
Like other similar iterators, it helps to get rid of temporary
on-stack bitmaps and associate housekeeping code.
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@...il.com>
---
include/linux/cpumask.h | 22 ++++++++++++++++++++++
include/linux/find.h | 38 ++++++++++++++++++++++++++++++++++++++
lib/find_bit.c | 9 +++++++++
3 files changed, 69 insertions(+)
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index ff8f41ab7ce6..8f8cb29d56d9 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -406,6 +406,28 @@ unsigned int cpumask_random(const struct cpumask *src)
#define for_each_cpu_and(cpu, mask1, mask2) \
for_each_and_bit(cpu, cpumask_bits(mask1), cpumask_bits(mask2), small_cpumask_bits)
+/**
+ * for_each_cpu_and_andnot_from - iterate over every cpu in all masks
+ * @cpu: the (optionally unsigned) integer iterator
+ * @mask1: the first cpumask pointer
+ * @mask2: the second cpumask pointer
+ * @mask3: the third cpumask pointer
+ *
+ * This saves a temporary CPU mask in many places. It is equivalent to:
+ * struct cpumask tmp;
+ * cpumask_and(&tmp, &mask1, &mask2);
+ * cpumask_andnot(&tmp, &tmp, &mask3);
+ * for_each_cpu_from(cpu, &tmp)
+ * ...
+ *
+ * After the loop, cpu is >= nr_cpu_ids.
+ */
+#define for_each_cpu_and_andnot_from(cpu, mask1, mask2, mask3) \
+ for_each_and_andnot_bit_from(cpu, cpumask_bits(mask1), \
+ cpumask_bits(mask2), \
+ cpumask_bits(mask3), \
+ small_cpumask_bits)
+
/**
* for_each_cpu_andnot - iterate over every cpu present in one mask, excluding
* those present in another.
diff --git a/include/linux/find.h b/include/linux/find.h
index 9d720ad92bc1..d43c811aef5c 100644
--- a/include/linux/find.h
+++ b/include/linux/find.h
@@ -14,6 +14,9 @@ unsigned long _find_next_and_bit(const unsigned long *addr1, const unsigned long
unsigned long nbits, unsigned long start);
unsigned long _find_next_andnot_bit(const unsigned long *addr1, const unsigned long *addr2,
unsigned long nbits, unsigned long start);
+unsigned long _find_next_and_andnot_bit(const unsigned long *addr1, const unsigned long *addr2,
+ const unsigned long *addr3, unsigned long size,
+ unsigned long n);
unsigned long _find_next_or_bit(const unsigned long *addr1, const unsigned long *addr2,
unsigned long nbits, unsigned long start);
unsigned long _find_next_zero_bit(const unsigned long *addr, unsigned long nbits,
@@ -135,6 +138,36 @@ unsigned long find_next_andnot_bit(const unsigned long *addr1,
}
#endif
+/**
+ * find_next_and_andnot_bit - find the next set bit in *addr1 and *addr2
+ * excluding all the bits in *addr3
+ * @addr1: The first address to base the search on
+ * @addr2: The second address to base the search on
+ * @addr3: The third address to base the search on
+ * @size: The bitmap size in bits
+ * @offset: The bitnumber to start searching at
+ *
+ * Returns the bit number for the next such bit
+ * If no bits found, returns >= @size.
+ */
+static __always_inline
+unsigned long find_next_and_andnot_bit(const unsigned long *addr1,
+ const unsigned long *addr2, const unsigned long *addr3,
+ unsigned long size, unsigned long offset)
+{
+ if (small_const_nbits(size)) {
+ unsigned long val;
+
+ if (unlikely(offset >= size))
+ return size;
+
+ val = *addr1 & *addr2 & ~*addr3 & GENMASK(size - 1, offset);
+ return val ? __ffs(val) : size;
+ }
+
+ return _find_next_and_andnot_bit(addr1, addr2, addr3, size, offset);
+}
+
#ifndef find_next_or_bit
/**
* find_next_or_bit - find the next set bit in either memory regions
@@ -595,6 +628,11 @@ unsigned long find_next_bit_le(const void *addr, unsigned
(bit) = find_next_andnot_bit((addr1), (addr2), (size), (bit)), (bit) < (size);\
(bit)++)
+#define for_each_and_andnot_bit_from(bit, addr1, addr2, addr3, size) \
+ for (; (bit) = find_next_and_andnot_bit((addr1), (addr2), (addr3), \
+ (size), (bit)), (bit) < (size); \
+ (bit)++)
+
#define for_each_or_bit(bit, addr1, addr2, size) \
for ((bit) = 0; \
(bit) = find_next_or_bit((addr1), (addr2), (size), (bit)), (bit) < (size);\
diff --git a/lib/find_bit.c b/lib/find_bit.c
index d4b5a29e3e72..aec79207c566 100644
--- a/lib/find_bit.c
+++ b/lib/find_bit.c
@@ -206,6 +206,15 @@ unsigned long _find_next_andnot_bit(const unsigned long *addr1, const unsigned l
EXPORT_SYMBOL(_find_next_andnot_bit);
#endif
+unsigned long _find_next_and_andnot_bit(const unsigned long *addr1,
+ const unsigned long *addr2,
+ const unsigned long *addr3,
+ unsigned long nbits, unsigned long start)
+{
+ return FIND_NEXT_BIT(addr1[idx] & addr2[idx] & ~addr3[idx], /* nop */, nbits, start);
+}
+EXPORT_SYMBOL(_find_next_and_andnot_bit);
+
#ifndef find_next_or_bit
unsigned long _find_next_or_bit(const unsigned long *addr1, const unsigned long *addr2,
unsigned long nbits, unsigned long start)
--
2.43.0
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