Re: [PATCH v3 3/9] bitops: Introduce find_next_andnot_bit()

[Yury Norov <yury.norov@gmail.com>]

On Thu, Aug 25, 2022 at 07:12:04PM +0100, Valentin Schneider wrote:
> In preparation of introducing for_each_cpu_andnot(), add a variant of
> find_next_bit() that negate the bits in @addr2 when ANDing them with the
> bits in @addr1.
> 
> Note that the _find_next_bit() @invert argument now gets split into two:
> @invert1 for words in @addr1, @invert2 for words in @addr2. The only
> current users of _find_next_bit() with @invert set are:
>   o find_next_zero_bit()
>   o find_next_zero_bit_le()
> and neither of these pass an @addr2, so the conversion is straightforward.
> 
> Signed-off-by: Valentin Schneider <vschneid@redhat.com>

Have you seen this series?
https://lore.kernel.org/lkml/YwaXvphVpy5A7fSs@yury-laptop/t/

It will significantly simplify your work for adding the
find_next_andnot_bit(). If you wait a week or so, you'll most likely
find it in -next.

Thanks,
Yury

> ---
>  include/linux/find.h | 44 ++++++++++++++++++++++++++++++++++++++------
>  lib/find_bit.c       | 23 ++++++++++++-----------
>  2 files changed, 50 insertions(+), 17 deletions(-)
> 
> diff --git a/include/linux/find.h b/include/linux/find.h
> index 424ef67d4a42..a195cf0a8bab 100644
> --- a/include/linux/find.h
> +++ b/include/linux/find.h
> @@ -10,7 +10,8 @@
>  
>  extern unsigned long _find_next_bit(const unsigned long *addr1,
>  		const unsigned long *addr2, unsigned long nbits,
> -		unsigned long start, unsigned long invert, unsigned long le);
> +		unsigned long start, unsigned long invert1, unsigned long invert2,
> +		unsigned long le);
>  extern unsigned long _find_first_bit(const unsigned long *addr, unsigned long size);
>  extern unsigned long _find_first_and_bit(const unsigned long *addr1,
>  					 const unsigned long *addr2, unsigned long size);
> @@ -41,7 +42,7 @@ unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
>  		return val ? __ffs(val) : size;
>  	}
>  
> -	return _find_next_bit(addr, NULL, size, offset, 0UL, 0);
> +	return _find_next_bit(addr, NULL, size, offset, 0UL, 0UL, 0);
>  }
>  #endif
>  
> @@ -71,7 +72,38 @@ unsigned long find_next_and_bit(const unsigned long *addr1,
>  		return val ? __ffs(val) : size;
>  	}
>  
> -	return _find_next_bit(addr1, addr2, size, offset, 0UL, 0);
> +	return _find_next_bit(addr1, addr2, size, offset, 0UL, 0UL, 0);
> +}
> +#endif
> +
> +#ifndef find_next_andnot_bit
> +/**
> + * find_next_andnot_bit - find the next bit in *addr1 excluding all the bits
> + *                        in *addr2
> + * @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_andnot_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_bit(addr1, addr2, size, offset, 0UL, ~0UL, 0);
>  }
>  #endif
>  
> @@ -99,7 +131,7 @@ unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
>  		return val == ~0UL ? size : ffz(val);
>  	}
>  
> -	return _find_next_bit(addr, NULL, size, offset, ~0UL, 0);
> +	return _find_next_bit(addr, NULL, size, offset, ~0UL, 0UL, 0);
>  }
>  #endif
>  
> @@ -247,7 +279,7 @@ unsigned long find_next_zero_bit_le(const void *addr, unsigned
>  		return val == ~0UL ? size : ffz(val);
>  	}
>  
> -	return _find_next_bit(addr, NULL, size, offset, ~0UL, 1);
> +	return _find_next_bit(addr, NULL, size, offset, ~0UL, 0UL, 1);
>  }
>  #endif
>  
> @@ -266,7 +298,7 @@ unsigned long find_next_bit_le(const void *addr, unsigned
>  		return val ? __ffs(val) : size;
>  	}
>  
> -	return _find_next_bit(addr, NULL, size, offset, 0UL, 1);
> +	return _find_next_bit(addr, NULL, size, offset, 0UL, 0UL, 1);
>  }
>  #endif
>  
> diff --git a/lib/find_bit.c b/lib/find_bit.c
> index 1b8e4b2a9cba..c46b66d7d2b4 100644
> --- a/lib/find_bit.c
> +++ b/lib/find_bit.c
> @@ -21,27 +21,29 @@
>  
>  #if !defined(find_next_bit) || !defined(find_next_zero_bit) ||			\
>  	!defined(find_next_bit_le) || !defined(find_next_zero_bit_le) ||	\
> -	!defined(find_next_and_bit)
> +	!defined(find_next_and_bit) || !defined(find_next_andnot_bit)
>  /*
>   * This is a common helper function for find_next_bit, find_next_zero_bit, and
>   * find_next_and_bit. The differences are:
> - *  - The "invert" argument, which is XORed with each fetched word before
> - *    searching it for one bits.
>   *  - The optional "addr2", which is anded with "addr1" if present.
> + *  - The "invert" arguments, which are XORed with each fetched word (invert1
> + *    for words in addr1, invert2 for those in addr2) before searching it for
> + *    one bits.
>   */
>  unsigned long _find_next_bit(const unsigned long *addr1,
> -		const unsigned long *addr2, unsigned long nbits,
> -		unsigned long start, unsigned long invert, unsigned long le)
> +			     const unsigned long *addr2,
> +			     unsigned long nbits, unsigned long start,
> +			     unsigned long invert1, unsigned long invert2,
> +			     unsigned long le)
>  {
>  	unsigned long tmp, mask;
>  
>  	if (unlikely(start >= nbits))
>  		return nbits;
>  
> -	tmp = addr1[start / BITS_PER_LONG];
> +	tmp = addr1[start / BITS_PER_LONG] ^ invert1;
>  	if (addr2)
> -		tmp &= addr2[start / BITS_PER_LONG];
> -	tmp ^= invert;
> +		tmp &= addr2[start / BITS_PER_LONG] ^ invert2;
>  
>  	/* Handle 1st word. */
>  	mask = BITMAP_FIRST_WORD_MASK(start);
> @@ -57,10 +59,9 @@ unsigned long _find_next_bit(const unsigned long *addr1,
>  		if (start >= nbits)
>  			return nbits;
>  
> -		tmp = addr1[start / BITS_PER_LONG];
> +		tmp = addr1[start / BITS_PER_LONG] ^ invert1;
>  		if (addr2)
> -			tmp &= addr2[start / BITS_PER_LONG];
> -		tmp ^= invert;
> +			tmp &= addr2[start / BITS_PER_LONG] ^ invert2;
>  	}
>  
>  	if (le)
> -- 
> 2.31.1