lib/find: introduce find_nth_and_andnot_bit

In the following patches the function is used to implement in-place bitmaps
traversing without storing intermediate result in temporary bitmaps.

Signed-off-by: Yury Norov <yury.norov@gmail.com>
Acked-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Peter Lafreniere <peter@n8pjl.ca>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/linux/find.h b/include/linux/find.h
index ccaf61a0f5fd5a6c89d7507fece5ea3afff56116..4647864a5ffdbb972fb1a1a21eb79178755b72d5 100644 (file)
--- a/include/linux/find.h
+++ b/include/linux/find.h
@@ -22,6 +22,9 @@ unsigned long __find_nth_and_bit(const unsigned long *addr1, const unsigned long
                                unsigned long size, unsigned long n);
 unsigned long __find_nth_andnot_bit(const unsigned long *addr1, const unsigned long *addr2,
                                        unsigned long size, unsigned long n);
+unsigned long __find_nth_and_andnot_bit(const unsigned long *addr1, const unsigned long *addr2,
+                                       const unsigned long *addr3, unsigned long size,
+                                       unsigned long n);
 extern unsigned long _find_first_and_bit(const unsigned long *addr1,
                                         const unsigned long *addr2, unsigned long size);
 extern unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size);
@@ -255,6 +258,36 @@ unsigned long find_nth_andnot_bit(const unsigned long *addr1, const unsigned lon
        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
+ * @addr1: The 1st address to start the search at
+ * @addr2: The 2nd address to start the search at
+ * @addr3: The 3rd 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_and_andnot_bit(const unsigned long *addr1,
+                                       const unsigned long *addr2,
+                                       const unsigned long *addr3,
+                                       unsigned long size, unsigned long n)
+{
+       if (n >= size)
+               return size;
+
+       if (small_const_nbits(size)) {
+               unsigned long val =  *addr1 & *addr2 & (~*addr3) & GENMASK(size - 1, 0);
+
+               return val ? fns(val, n) : size;
+       }
+
+       return __find_nth_and_andnot_bit(addr1, addr2, addr3, size, n);
+}
+
 #ifndef find_first_and_bit
 /**
  * find_first_and_bit - find the first set bit in both memory regions

diff --git a/lib/find_bit.c b/lib/find_bit.c
index 18bc0a7ac8eed9807962024df4cd421ac4272c7e..c10920e667889c1a2e86f5916b9998b21893ba77 100644 (file)
--- a/lib/find_bit.c
+++ b/lib/find_bit.c
@@ -155,6 +155,15 @@ unsigned long __find_nth_andnot_bit(const unsigned long *addr1, const unsigned l
 }
 EXPORT_SYMBOL(__find_nth_andnot_bit);
 
+unsigned long __find_nth_and_andnot_bit(const unsigned long *addr1,
+                                       const unsigned long *addr2,
+                                       const unsigned long *addr3,
+                                       unsigned long size, unsigned long n)
+{
+       return FIND_NTH_BIT(addr1[idx] & addr2[idx] & ~addr3[idx], size, n);
+}
+EXPORT_SYMBOL(__find_nth_and_andnot_bit);
+
 #ifndef find_next_and_bit
 unsigned long _find_next_and_bit(const unsigned long *addr1, const unsigned long *addr2,
                                        unsigned long nbits, unsigned long start)