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Peter Anvin" , Rasmus Villemoes , x86@kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 2/4] find: add find_first_andnot_bit() Date: Sun, 27 Apr 2025 14:52:29 -0400 Message-ID: <20250427185242.221974-3-yury.norov@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250427185242.221974-1-yury.norov@gmail.com> References: <20250427185242.221974-1-yury.norov@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: "Yury Norov [NVIDIA]" The function helps to implement cpumask_andnot() APIs. Tested-by: James Morse Reviewed-by: James Morse Signed-off-by: Yury Norov [NVIDIA] --- 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..5a2c267ea7f9 100644 --- a/include/linux/find.h +++ b/include/linux/find.h @@ -29,6 +29,8 @@ unsigned long __find_nth_and_andnot_bit(const unsigned lo= ng *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 uns= igned long *addr2, + unsigned long size); unsigned long _find_first_and_and_bit(const unsigned long *addr1, const un= signed long *addr2, const unsigned long *addr3, unsigned long size); extern unsigned long _find_first_zero_bit(const unsigned long *addr, unsig= ned long size); @@ -347,6 +349,29 @@ unsigned long find_first_and_bit(const unsigned long *= addr1, } #endif =20 +/** + * 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 first set bit + * If no bits are set, returns >=3D @size. + */ +static __always_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 =3D *addr1 & (~*addr2) & GENMASK(size - 1, 0); + + return val ? __ffs(val) : size; + } + + return _find_first_andnot_bit(addr1, addr2, size); +} + /** * find_first_and_and_bit - find the first set bit in 3 memory regions * @addr1: The first address to base the search on diff --git a/lib/find_bit.c b/lib/find_bit.c index 0836bb3d76c5..06b6342aa3ae 100644 --- a/lib/find_bit.c +++ b/lib/find_bit.c @@ -116,6 +116,17 @@ unsigned long _find_first_and_bit(const unsigned long = *addr1, EXPORT_SYMBOL(_find_first_and_bit); #endif =20 +/* + * Find the first bit set in 1st memory region and unset in 2nd. + */ +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); + /* * Find the first set bit in three memory regions. */ --=20 2.43.0