bitmap-for-6.17

Bits-related patched for 6.17:
  - find_random_bit() series (Yury);
  - GENMASK() consolidation (Vincent);
  - random cleanups (Shaopeng, Ben, Yury)
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Merge tag 'bitmap-for-6.17' of https://github.com/norov/linux

Pull bitmap updates from Yury Norov:

 - find_random_bit() series (Yury)

 - GENMASK() consolidation (Vincent)

 - random cleanups (Shaopeng, Ben, Yury)

* tag 'bitmap-for-6.17' of https://github.com/norov/linux:
  bitfield: Ensure the return values of helper functions are checked
  test_bits: add tests for __GENMASK() and __GENMASK_ULL()
  bits: unify the non-asm GENMASK*()
  bits: split the definition of the asm and non-asm GENMASK*()
  cpumask: Remove unnecessary cpumask_nth_andnot()
  watchdog: fix opencoded cpumask_next_wrap() in watchdog_next_cpu()
  clocksource: Improve randomness in clocksource_verify_choose_cpus()
  cpumask: introduce cpumask_random()
  bitmap: generalize node_random()

include/linux/bitfield.h

@@ -189,14 +189,14 @@ static __always_inline u64 field_mask(u64 field)
 }
 #define field_max(field)	((typeof(field))field_mask(field))
 #define ____MAKE_OP(type,base,to,from)					\
-static __always_inline __##type type##_encode_bits(base v, base field)	\
+static __always_inline __##type __must_check type##_encode_bits(base v, base field)	\
 {									\
 	if (__builtin_constant_p(v) && (v & ~field_mask(field)))	\
 		__field_overflow();					\
 	return to((v & field_mask(field)) * field_multiplier(field));	\
 }									\
-static __always_inline __##type type##_replace_bits(__##type old,	\
+static __always_inline __##type __must_check type##_replace_bits(__##type old,	\
-					base val, base field)		\
+							base val, base field)	\
 {									\
 	return (old & ~to(field)) | type##_encode_bits(val, field);	\
 }									\
@@ -205,7 +205,7 @@ static __always_inline void type##p_replace_bits(__##type *p,		\
 {									\
 	*p = (*p & ~to(field)) | type##_encode_bits(val, field);	\
 }									\
-static __always_inline base type##_get_bits(__##type v, base field)	\
+static __always_inline base __must_check type##_get_bits(__##type v, base field)	\
 {									\
 	return (from(v) & field)/field_multiplier(field);		\
 }

include/linux/bits.h

@@ -2,10 +2,8 @@
 #ifndef __LINUX_BITS_H
 #define __LINUX_BITS_H
 
-#include <linux/const.h>
 #include <vdso/bits.h>
 #include <uapi/linux/bits.h>
-#include <asm/bitsperlong.h>
 
 #define BIT_MASK(nr)		(UL(1) << ((nr) % BITS_PER_LONG))
 #define BIT_WORD(nr)		((nr) / BITS_PER_LONG)
@@ -50,10 +48,14 @@
 	     (type_max(t) << (l) &				\
 	      type_max(t) >> (BITS_PER_TYPE(t) - 1 - (h)))))
 
+#define GENMASK(h, l)		GENMASK_TYPE(unsigned long, h, l)
+#define GENMASK_ULL(h, l)	GENMASK_TYPE(unsigned long long, h, l)
+
 #define GENMASK_U8(h, l)	GENMASK_TYPE(u8, h, l)
 #define GENMASK_U16(h, l)	GENMASK_TYPE(u16, h, l)
 #define GENMASK_U32(h, l)	GENMASK_TYPE(u32, h, l)
 #define GENMASK_U64(h, l)	GENMASK_TYPE(u64, h, l)
+#define GENMASK_U128(h, l)	GENMASK_TYPE(u128, h, l)
 
 /*
  * Fixed-type variants of BIT(), with additional checks like GENMASK_TYPE(). The
@@ -79,28 +81,9 @@
  * BUILD_BUG_ON_ZERO is not available in h files included from asm files,
  * disable the input check if that is the case.
  */
-#define GENMASK_INPUT_CHECK(h, l) 0
+#define GENMASK(h, l)		__GENMASK(h, l)
+#define GENMASK_ULL(h, l)	__GENMASK_ULL(h, l)
 
 #endif /* !defined(__ASSEMBLY__) */
 
-#define GENMASK(h, l) \
-	(GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l))
-#define GENMASK_ULL(h, l) \
-	(GENMASK_INPUT_CHECK(h, l) + __GENMASK_ULL(h, l))
-
-#if !defined(__ASSEMBLY__)
-/*
- * Missing asm support
- *
- * __GENMASK_U128() depends on _BIT128() which would not work
- * in the asm code, as it shifts an 'unsigned __int128' data
- * type instead of direct representation of 128 bit constants
- * such as long and unsigned long. The fundamental problem is
- * that a 128 bit constant will get silently truncated by the
- * gcc compiler.
- */
-#define GENMASK_U128(h, l) \
-	(GENMASK_INPUT_CHECK(h, l) + __GENMASK_U128(h, l))
-#endif
-
 #endif	/* __LINUX_BITS_H */

include/linux/cpumask.h

@@ -354,6 +354,18 @@ unsigned int cpumask_next_wrap(int n, const struct cpumask *src)
 	return find_next_bit_wrap(cpumask_bits(src), small_cpumask_bits, n + 1);
 }
 
+/**
+ * cpumask_random - get random cpu in *src.
+ * @src: cpumask pointer
+ *
+ * Return: random set bit, or >= nr_cpu_ids if @src is empty.
+ */
+static __always_inline
+unsigned int cpumask_random(const struct cpumask *src)
+{
+	return find_random_bit(cpumask_bits(src), nr_cpu_ids);
+}
+
 /**
  * for_each_cpu - iterate over every cpu in a mask
  * @cpu: the (optionally unsigned) integer iterator
@@ -546,22 +558,6 @@ unsigned int cpumask_nth_and(unsigned int cpu, const struct cpumask *srcp1,
 				small_cpumask_bits, cpumask_check(cpu));
 }
 
-/**
- * cpumask_nth_andnot - get the Nth cpu set in 1st cpumask, and clear in 2nd.
- * @srcp1: the cpumask pointer
- * @srcp2: the cpumask pointer
- * @cpu: the Nth cpu to find, starting from 0
- *
- * Return: >= nr_cpu_ids if such cpu doesn't exist.
- */
-static __always_inline
-unsigned int cpumask_nth_andnot(unsigned int cpu, const struct cpumask *srcp1,
-							const struct cpumask *srcp2)
-{
-	return find_nth_andnot_bit(cpumask_bits(srcp1), cpumask_bits(srcp2),
-				small_cpumask_bits, cpumask_check(cpu));
-}
-
 /**
  * cpumask_nth_and_andnot - get the Nth cpu set in 1st and 2nd cpumask, and clear in 3rd.
  * @srcp1: the cpumask pointer

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
@@ -267,33 +269,6 @@ unsigned long find_nth_and_bit(const unsigned long *addr1, const unsigned long *
 	return __find_nth_and_bit(addr1, addr2, size, n);
 }
 
-/**
- * find_nth_andnot_bit - find N'th set bit in 2 memory regions,
- *			 flipping bits in 2nd region
- * @addr1: The 1st address to start the search at
- * @addr2: The 2nd address to start the search at
- * @size: The maximum number of bits to search
- * @n: The number of set bit, which position is needed, counting from 0
- *
- * Returns the bit number of the N'th set bit.
- * If no such, returns @size.
- */
-static __always_inline
-unsigned long find_nth_andnot_bit(const unsigned long *addr1, const unsigned long *addr2,
-				unsigned long size, unsigned long n)
-{
-	if (n >= size)
-		return size;
-
-	if (small_const_nbits(size)) {
-		unsigned long val =  *addr1 & (~*addr2) & GENMASK(size - 1, 0);
-
-		return val ? fns(val, n) : size;
-	}
-
-	return __find_nth_andnot_bit(addr1, addr2, size, n);
-}
-
 /**
  * find_nth_and_andnot_bit - find N'th set bit in 2 memory regions,
  *			     excluding those set in 3rd region

include/linux/nodemask.h

@@ -492,21 +492,9 @@ 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;
+	int node = find_random_bit(maskp->bits, MAX_NUMNODES);
 
-	w = nodes_weight(*maskp);
+	return node < MAX_NUMNODES ? node : NUMA_NO_NODE;
-	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;
 #else
 	return 0;
 #endif

kernel/time/clocksource.c

@@ -340,10 +340,7 @@ static void clocksource_verify_choose_cpus(void)
 	 * CPUs that are currently online.
 	 */
 	for (i = 1; i < n; i++) {
-		cpu = get_random_u32_below(nr_cpu_ids);
+		cpu = cpumask_random(cpu_online_mask);
-		cpu = cpumask_next(cpu - 1, cpu_online_mask);
-		if (cpu >= nr_cpu_ids)
-			cpu = cpumask_first(cpu_online_mask);
 		if (!WARN_ON_ONCE(cpu >= nr_cpu_ids))
 			cpumask_set_cpu(cpu, &cpus_chosen);
 	}

kernel/watchdog_buddy.c

@@ -12,10 +12,7 @@ static unsigned int watchdog_next_cpu(unsigned int cpu)
 {
 	unsigned int next_cpu;
 
-	next_cpu = cpumask_next(cpu, &watchdog_cpus);
+	next_cpu = cpumask_next_wrap(cpu, &watchdog_cpus);
-	if (next_cpu >= nr_cpu_ids)
-		next_cpu = cpumask_first(&watchdog_cpus);
-
 	if (next_cpu == cpu)
 		return nr_cpu_ids;
 

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
@@ -291,3 +292,26 @@ EXPORT_SYMBOL(_find_next_bit_le);
 #endif
 
 #endif /* __BIG_ENDIAN */
+
+/**
+ * find_random_bit - find a set bit at random position
+ * @addr: The address to base the search on
+ * @size: The bitmap size in bits
+ *
+ * Returns: a position of a random set bit; >= @size otherwise
+ */
+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:
+		/* Performance trick for single-bit bitmaps */
+		return find_first_bit(addr, size);
+	default:
+		return find_nth_bit(addr, size, get_random_u32_below(w));
+	}
+}
+EXPORT_SYMBOL(find_random_bit);

lib/tests/test_bits.c

@@ -26,6 +26,23 @@ static_assert(assert_type(u16, GENMASK_U16(15, 0)) == U16_MAX);
 static_assert(assert_type(u32, GENMASK_U32(31, 0)) == U32_MAX);
 static_assert(assert_type(u64, GENMASK_U64(63, 0)) == U64_MAX);
 
+/* FIXME: add a test case written in asm for GENMASK() and GENMASK_ULL() */
+
+static void __genmask_test(struct kunit *test)
+{
+	KUNIT_EXPECT_EQ(test, 1ul, __GENMASK(0, 0));
+	KUNIT_EXPECT_EQ(test, 3ul, __GENMASK(1, 0));
+	KUNIT_EXPECT_EQ(test, 6ul, __GENMASK(2, 1));
+	KUNIT_EXPECT_EQ(test, 0xFFFFFFFFul, __GENMASK(31, 0));
+}
+
+static void __genmask_ull_test(struct kunit *test)
+{
+	KUNIT_EXPECT_EQ(test, 1ull, __GENMASK_ULL(0, 0));
+	KUNIT_EXPECT_EQ(test, 3ull, __GENMASK_ULL(1, 0));
+	KUNIT_EXPECT_EQ(test, 0x000000ffffe00000ull, __GENMASK_ULL(39, 21));
+	KUNIT_EXPECT_EQ(test, 0xffffffffffffffffull, __GENMASK_ULL(63, 0));
+}
 
 static void genmask_test(struct kunit *test)
 {
@@ -123,6 +140,8 @@ static void genmask_input_check_test(struct kunit *test)
 
 
 static struct kunit_case bits_test_cases[] = {
+	KUNIT_CASE(__genmask_test),
+	KUNIT_CASE(__genmask_ull_test),
 	KUNIT_CASE(genmask_test),
 	KUNIT_CASE(genmask_ull_test),
 	KUNIT_CASE(genmask_u128_test),