linux-kernel - Re: [PATCH 2/4] find: add find_first_andnot

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Message-ID: <062e5e61-e2c3-418e-987b-33fd9009d03f@intel.com>
Date: Wed, 23 Apr 2025 14:28:26 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Yury Norov <yury.norov@...il.com>, Tony Luck <tony.luck@...el.com>,
	"Thomas Gleixner" <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
	"Borislav Petkov" <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>, Rasmus Villemoes
	<linux@...musvillemoes.dk>, <x86@...nel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/4] find: add find_first_andnot_bit()

Hi Yury,

On 4/7/25 8:38 AM, Yury Norov wrote:
> From: Yury Norov [NVIDIA] <yury.norov@...il.com>
> 
> The function helps to implement cpumask_andnot() APIs.
> 
> Signed-off-by: Yury Norov [NVIDIA] <yury.norov@...il.com>
> ---
>  include/linux/find.h | 25 +++++++++++++++++++++++++
>  lib/find_bit.c       | 11 +++++++++++
>  2 files changed, 36 insertions(+)
> 
> diff --git a/include/linux/find.h b/include/linux/find.h
> index 68685714bc18..d1578cfb667c 100644
> --- a/include/linux/find.h
> +++ b/include/linux/find.h
> @@ -29,6 +29,8 @@ unsigned long __find_nth_and_andnot_bit(const unsigned long *addr1, const unsign
>  					unsigned long n);
>  extern unsigned long _find_first_and_bit(const unsigned long *addr1,
>  					 const unsigned long *addr2, unsigned long size);
> +unsigned long _find_first_andnot_bit(const unsigned long *addr1, const unsigned long *addr2,
> +				 unsigned long size);
>  unsigned long _find_first_and_and_bit(const unsigned long *addr1, const unsigned long *addr2,
>  				      const unsigned long *addr3, unsigned long size);
>  extern unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size);
> @@ -347,6 +349,29 @@ unsigned long find_first_and_bit(const unsigned long *addr1,
>  }
>  #endif
>  
> +/**
> + * find_first_andnot_bit - find the first bit set in 1st memory region and unset in 2nd
> + * @addr1: The first address to base the search on
> + * @addr2: The second address to base the search on
> + * @size: The bitmap size in bits
> + *
> + * Returns the bit number for the matched bit
> + * If no bits are set, returns >= @size.

Should this be "If no bits are set, returns @size." to match similar document
snippets as well as what the code does?

I am not familiar with the customs of this area but I did notice that
this patch triggers some checkpatch.pl warnings about alignment not
matching open parenthesis ... but looking at the existing content of this
file this custom does not seem to apply here.

Reinette