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    SubjectRe: [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@efficios.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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