[PATCH v2 1/8] lib/find: add find_next_and_andnot_bit()

Yury Norov
2023-04-20T05:19:57Z

Similarly to find_nth_and_andnot_bit(), find_next_and_andnot_bit() is
a convenient helper that allows traversing bitmaps without storing
intermediate results in a temporary bitmap.

In the following patches the function is used to implement NUMA-aware
CPUs enumeration.

Signed-off-by: Yury Norov <yury.norov@gmail.com>
---
include/linux/find.h | 43 +++++++++++++++++++++++++++++++++++++++++++
lib/find_bit.c | 12 ++++++++++++
2 files changed, 55 insertions(+)

diff --git a/include/linux/find.h b/include/linux/find.h
index 5e4f39ef2e72..90b68d76c073 100644
--- a/include/linux/find.h
+++ b/include/linux/find.h
@@ -16,6 +16,9 @@ unsigned long _find_next_andnot_bit(const unsigned long *addr1, const unsigned l
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_and_andnot_bit(const unsigned long *addr1, const unsigned long *addr2,
+ const unsigned long *addr3, 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);
@@ -159,6 +162,40 @@ unsigned long find_next_or_bit(const unsigned long *addr1,
}
#endif

+#ifndef find_next_and_andnot_bit
+/**
+ * find_next_and_andnot_bit - find the next bit set 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
+ *
+ * Return: the bit number for the next set bit
+ * If no bits are set, 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);
+}
+#endif
+
#ifndef find_next_zero_bit
/**
* find_next_zero_bit - find the next cleared bit in a memory region
@@ -568,6 +605,12 @@ 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(bit, addr1, addr2, addr3, size) \
+ for ((bit) = 0; \
+ (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 32f99e9a670e..4403e00890b1 100644
--- a/lib/find_bit.c
+++ b/lib/find_bit.c
@@ -182,6 +182,18 @@ unsigned long _find_next_andnot_bit(const unsigned long *addr1, const unsigned l
EXPORT_SYMBOL(_find_next_andnot_bit);
#endif

+#ifndef find_next_and_andnot_bit
+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);
+#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)
--
2.34.1