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Date: Thu, 25 Aug 2022 14:05:16 -0700
From: Yury Norov <yury.norov@...il.com>
To: Valentin Schneider <vschneid@...hat.com>
Cc: netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
linux-kernel@...r.kernel.org, Saeed Mahameed <saeedm@...dia.com>,
Leon Romanovsky <leon@...nel.org>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Rasmus Villemoes <linux@...musvillemoes.dk>,
Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Vincent Guittot <vincent.guittot@...aro.org>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Steven Rostedt <rostedt@...dmis.org>,
Mel Gorman <mgorman@...e.de>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Heiko Carstens <hca@...ux.ibm.com>,
Tony Luck <tony.luck@...el.com>,
Jonathan Cameron <Jonathan.Cameron@...wei.com>,
Gal Pressman <gal@...dia.com>,
Tariq Toukan <tariqt@...dia.com>,
Jesse Brandeburg <jesse.brandeburg@...el.com>
Subject: Re: [PATCH v3 3/9] bitops: Introduce find_next_andnot_bit()
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@...hat.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
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