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Message-ID: <ZVzjfpEfT2mz6B59@yury-ThinkPad>
Date: Tue, 21 Nov 2023 09:06:06 -0800
From: Yury Norov <yury.norov@...il.com>
To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Peter Zijlstra <peterz@...radead.org>,
linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
"Paul E . McKenney" <paulmck@...nel.org>,
Boqun Feng <boqun.feng@...il.com>,
"H . Peter Anvin" <hpa@...or.com>, Paul Turner <pjt@...gle.com>,
linux-api@...r.kernel.org, Christian Brauner <brauner@...nel.org>,
Florian Weimer <fw@...eb.enyo.de>, David.Laight@...lab.com,
carlos@...hat.com, Peter Oskolkov <posk@...k.io>,
Alexander Mikhalitsyn <alexander@...alicyn.com>,
Chris Kennelly <ckennelly@...gle.com>
Subject: Re: [PATCH 22/30] lib: Implement
find_{first,next,nth}_notandnot_bit, find_first_andnot_bit
On Tue, Nov 22, 2022 at 03:39:24PM -0500, Mathieu Desnoyers wrote:
> Allow finding the first, next, or nth bit within two input bitmasks
> which is zero in both masks.
>
> Allow fiding the first bit within two input bitmasks which is set in
> first mask and cleared in the second mask. find_next_andnot_bit and
> find_nth_andnot_bit already exist, so find the first bit appears to be
> missing.
>
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> ---
> include/linux/find.h | 123 +++++++++++++++++++++++++++++++++++++++++--
> lib/find_bit.c | 42 +++++++++++++++
> 2 files changed, 161 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/find.h b/include/linux/find.h
> index ccaf61a0f5fd..43c3db92a096 100644
> --- a/include/linux/find.h
> +++ b/include/linux/find.h
> @@ -14,6 +14,8 @@ unsigned long _find_next_and_bit(const unsigned long *addr1, const unsigned long
> unsigned long nbits, unsigned long start);
> unsigned long _find_next_andnot_bit(const unsigned long *addr1, const unsigned long *addr2,
> unsigned long nbits, unsigned long start);
> +unsigned long _find_next_notandnot_bit(const unsigned long *addr1, const unsigned long *addr2,
> + 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);
> @@ -22,8 +24,14 @@ 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_notandnot_bit(const unsigned long *addr1, const unsigned long *addr2,
> + 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_andnot_bit(const unsigned long *addr1,
> + const unsigned long *addr2, unsigned long size);
> +extern unsigned long _find_first_notandnot_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);
> extern unsigned long _find_last_bit(const unsigned long *addr, unsigned long size);
>
> @@ -95,15 +103,14 @@ unsigned long find_next_and_bit(const unsigned long *addr1,
>
> #ifndef find_next_andnot_bit
> /**
> - * find_next_andnot_bit - find the next set bit in *addr1 excluding all the bits
> - * in *addr2
> + * find_next_andnot_bit - find the next bit set in *addr1, cleared 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.
> + * Returns the bit number for the next bit set in *addr1, cleared in *addr2
> + * If no such bits are found, returns @size.
> */
> static inline
> unsigned long find_next_andnot_bit(const unsigned long *addr1,
> @@ -124,6 +131,37 @@ unsigned long find_next_andnot_bit(const unsigned long *addr1,
> }
> #endif
>
> +#ifndef find_next_notandnot_bit
You don't need ifdefs for new functions. If arch people will add their
implementations, they will protect generic version themself.
> +/**
> + * find_next_notandnot_bit - find the next bit cleared in both *addr1 and *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 bit cleared in both *addr1 and *addr2
> + * If no such bits are found, returns @size.
> + */
> +static inline
> +unsigned long find_next_notandnot_bit(const unsigned long *addr1,
> + const unsigned long *addr2, unsigned long size,
> + unsigned long offset)
This should be find_next_zero_or_bit(). That way you'll avoid
negation for both maps and be consistent with existing API.
> +{
> + 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_notandnot_bit(addr1, addr2, size, offset);
> +}
> +#endif
> +
> +
> #ifndef find_next_zero_bit
> /**
> * find_next_zero_bit - find the next cleared bit in a memory region
> @@ -255,6 +293,32 @@ unsigned long find_nth_andnot_bit(const unsigned long *addr1, const unsigned lon
> return __find_nth_andnot_bit(addr1, addr2, size, n);
> }
>
> +/**
> + * find_nth_notandnot_bit - find N'th cleared bit in 2 memory regions.
> + * @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 cleared bit.
> + * If no such, returns @size.
> + */
> +static inline
> +unsigned long find_nth_notandnot_bit(const unsigned long *addr1, const unsigned long *addr2,
> + unsigned long size, unsigned long n)
Same here. find_nth_zero_or_bit()
Thanks,
Yury
> +{
> + 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_notandnot_bit(addr1, addr2, size, n);
> +}
> +
> #ifndef find_first_and_bit
> /**
> * find_first_and_bit - find the first set bit in both memory regions
> @@ -280,6 +344,57 @@ unsigned long find_first_and_bit(const unsigned long *addr1,
> }
> #endif
>
> +#ifndef find_first_andnot_bit
> +/**
> + * find_first_andnot_bit - find first set bit in 2 memory regions,
> + * flipping bits in 2nd region
> + * @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 next set bit
> + * If no bits are set, returns @size.
> + */
> +static inline
> +unsigned long find_first_andnot_bit(const unsigned long *addr1,
> + const unsigned long *addr2,
> + unsigned long size)
> +{
> + if (small_const_nbits(size)) {
> + unsigned long val = *addr1 & (~*addr2) & GENMASK(size - 1, 0);
> +
> + return val ? __ffs(val) : size;
> + }
> +
> + return _find_first_andnot_bit(addr1, addr2, size);
> +}
> +#endif
> +
> +#ifndef find_first_notandnot_bit
> +/**
> + * find_first_notandnot_bit - find first cleared bit in 2 memory regions
> + * @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 next cleared bit
> + * If no bits are set, returns @size.
> + */
> +static inline
> +unsigned long find_first_notandnot_bit(const unsigned long *addr1,
> + const unsigned long *addr2,
> + unsigned long size)
> +{
> + if (small_const_nbits(size)) {
> + unsigned long val = (~*addr1) & (~*addr2) & GENMASK(size - 1, 0);
> +
> + return val ? __ffs(val) : size;
> + }
> +
> + return _find_first_notandnot_bit(addr1, addr2, size);
> +}
> +#endif
> +
> #ifndef find_first_zero_bit
> /**
> * find_first_zero_bit - find the first cleared bit in a memory region
> diff --git a/lib/find_bit.c b/lib/find_bit.c
> index 18bc0a7ac8ee..a1f592f2437e 100644
> --- a/lib/find_bit.c
> +++ b/lib/find_bit.c
> @@ -116,6 +116,32 @@ unsigned long _find_first_and_bit(const unsigned long *addr1,
> EXPORT_SYMBOL(_find_first_and_bit);
> #endif
>
> +#ifndef find_first_andnot_bit
> +/*
> + * Find the first set bit in two memory regions, flipping bits in 2nd region.
> + */
> +unsigned long _find_first_andnot_bit(const unsigned long *addr1,
> + const unsigned long *addr2,
> + unsigned long size)
> +{
> + return FIND_FIRST_BIT(addr1[idx] & ~addr2[idx], /* nop */, size);
> +}
> +EXPORT_SYMBOL(_find_first_andnot_bit);
> +#endif
> +
> +#ifndef find_first_notandnot_bit
> +/*
> + * Find the first cleared bit in two memory regions.
> + */
> +unsigned long _find_first_notandnot_bit(const unsigned long *addr1,
> + const unsigned long *addr2,
> + unsigned long size)
> +{
> + return FIND_FIRST_BIT(~addr1[idx] & ~addr2[idx], /* nop */, size);
> +}
> +EXPORT_SYMBOL(_find_first_notandnot_bit);
> +#endif
> +
> #ifndef find_first_zero_bit
> /*
> * Find the first cleared bit in a memory region.
> @@ -155,6 +181,13 @@ unsigned long __find_nth_andnot_bit(const unsigned long *addr1, const unsigned l
> }
> EXPORT_SYMBOL(__find_nth_andnot_bit);
>
> +unsigned long __find_nth_notandnot_bit(const unsigned long *addr1, const unsigned long *addr2,
> + unsigned long size, unsigned long n)
> +{
> + return FIND_NTH_BIT(~addr1[idx] & ~addr2[idx], size, n);
> +}
> +EXPORT_SYMBOL(__find_nth_notandnot_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)
> @@ -173,6 +206,15 @@ unsigned long _find_next_andnot_bit(const unsigned long *addr1, const unsigned l
> EXPORT_SYMBOL(_find_next_andnot_bit);
> #endif
>
> +#ifndef find_next_notandnot_bit
> +unsigned long _find_next_notandnot_bit(const unsigned long *addr1, const unsigned long *addr2,
> + unsigned long nbits, unsigned long start)
> +{
> + return FIND_NEXT_BIT(~addr1[idx] & ~addr2[idx], /* nop */, nbits, start);
> +}
> +EXPORT_SYMBOL(_find_next_notandnot_bit);
> +#endif
> +
> #ifndef find_next_zero_bit
> unsigned long _find_next_zero_bit(const unsigned long *addr, unsigned long nbits,
> unsigned long start)
> --
> 2.25.1
>
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