linux-kernel - [PATCH 1/4] cpumask: introduce for_each_cpu

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Message-Id: <20230315084938.2544737-2-david@fromorbit.com>
Date:   Wed, 15 Mar 2023 19:49:35 +1100
From:   Dave Chinner <david@...morbit.com>
To:     linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org
Cc:     linux-mm@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        yebin10@...wei.com
Subject: [PATCH 1/4] cpumask: introduce for_each_cpu_or

From: Dave Chinner <dchinner@...hat.com>

Equivalent of for_each_cpu_and, except it ORs the two masks together
so it iterates all the CPUs present in either mask.

Signed-off-by: Dave Chinner <dchinner@...hat.com>
---
 include/linux/cpumask.h | 17 +++++++++++++++++
 include/linux/find.h    | 37 +++++++++++++++++++++++++++++++++++++
 lib/find_bit.c          |  9 +++++++++
 3 files changed, 63 insertions(+)

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index d4901ca8883c..ca736b05ec7b 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -350,6 +350,23 @@ unsigned int __pure cpumask_next_wrap(int n, const struct cpumask *mask, int sta
 #define for_each_cpu_andnot(cpu, mask1, mask2)				\
 	for_each_andnot_bit(cpu, cpumask_bits(mask1), cpumask_bits(mask2), small_cpumask_bits)
 
+/**
+ * for_each_cpu_or - iterate over every cpu present in either mask
+ * @cpu: the (optionally unsigned) integer iterator
+ * @mask1: the first cpumask pointer
+ * @mask2: the second cpumask pointer
+ *
+ * This saves a temporary CPU mask in many places.  It is equivalent to:
+ *	struct cpumask tmp;
+ *	cpumask_or(&tmp, &mask1, &mask2);
+ *	for_each_cpu(cpu, &tmp)
+ *		...
+ *
+ * After the loop, cpu is >= nr_cpu_ids.
+ */
+#define for_each_cpu_or(cpu, mask1, mask2)				\
+	for_each_or_bit(cpu, cpumask_bits(mask1), cpumask_bits(mask2), small_cpumask_bits)
+
 /**
  * cpumask_any_but - return a "random" in a cpumask, but not this one.
  * @mask: the cpumask to search
diff --git a/include/linux/find.h b/include/linux/find.h
index 4647864a5ffd..5e4f39ef2e72 100644
--- a/include/linux/find.h
+++ b/include/linux/find.h
@@ -14,6 +14,8 @@ 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_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,
 					 unsigned long start);
 extern unsigned long _find_first_bit(const unsigned long *addr, unsigned long size);
@@ -127,6 +129,36 @@ unsigned long find_next_andnot_bit(const unsigned long *addr1,
 }
 #endif
 
+#ifndef find_next_or_bit
+/**
+ * find_next_or_bit - find the next set bit in either memory regions
+ * @addr1: The first address to base the search on
+ * @addr2: The second 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 set bit
+ * If no bits are set, returns @size.
+ */
+static inline
+unsigned long find_next_or_bit(const unsigned long *addr1,
+		const unsigned long *addr2, unsigned long size,
+		unsigned long offset)
+{
+	if (small_const_nbits(size)) {
+		unsigned long val;
+
+		if (unlikely(offset >= size))
+			return size;
+
+		val = (*addr1 | *addr2) & GENMASK(size - 1, offset);
+		return val ? __ffs(val) : size;
+	}
+
+	return _find_next_or_bit(addr1, addr2, size, offset);
+}
+#endif
+
 #ifndef find_next_zero_bit
 /**
  * find_next_zero_bit - find the next cleared bit in a memory region
@@ -536,6 +568,11 @@ 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_or_bit(bit, addr1, addr2, size) \
+	for ((bit) = 0;									\
+	     (bit) = find_next_or_bit((addr1), (addr2), (size), (bit)), (bit) < (size);\
+	     (bit)++)
+
 /* same as for_each_set_bit() but use bit as value to start with */
 #define for_each_set_bit_from(bit, addr, size) \
 	for (; (bit) = find_next_bit((addr), (size), (bit)), (bit) < (size); (bit)++)
diff --git a/lib/find_bit.c b/lib/find_bit.c
index c10920e66788..32f99e9a670e 100644
--- a/lib/find_bit.c
+++ b/lib/find_bit.c
@@ -182,6 +182,15 @@ unsigned long _find_next_andnot_bit(const unsigned long *addr1, const unsigned l
 EXPORT_SYMBOL(_find_next_andnot_bit);
 #endif
 
+#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)
+{
+	return FIND_NEXT_BIT(addr1[idx] | addr2[idx], /* nop */, nbits, start);
+}
+EXPORT_SYMBOL(_find_next_or_bit);
+#endif
+
 #ifndef find_next_zero_bit
 unsigned long _find_next_zero_bit(const unsigned long *addr, unsigned long nbits,
 					 unsigned long start)
-- 
2.39.2