linux-kernel - [PATCH v2 0/5] lib/find: add find_nth

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Message-Id: <20220711044711.466822-1-yury.norov@gmail.com>
Date:   Sun, 10 Jul 2022 21:47:06 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     linux-kernel@...r.kernel.org,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Arnd Bergmann <arnd@...db.de>, David Gow <davidgow@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Isabella Basso <isabbasso@...eup.net>,
        Kees Cook <keescook@...omium.org>,
        Keith Busch <kbusch@...nel.org>,
        Kumar Kartikeya Dwivedi <memxor@...il.com>,
        Marco Elver <elver@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Steven Rostedt <rostedt@...dmis.org>,
        Toke Høiland-Jørgensen <toke@...hat.com>
Cc:     Yury Norov <yury.norov@...il.com>
Subject: [PATCH v2 0/5] lib/find: add find_nth_bit()

Kernel lacks for a function that searches for Nth bit in a bitmap.
Usually people do it like this:
        for_each_set_bit(bit, mask, size)
                if (--n == 0)
                        return bit;

Which is not so elegant, and very slow.

This series adds fast routines for this task, and applies them where
appropriate.

While here, move thin wrappers around find_bit() in nodemask.c to a
corresponding header, and because nodemask.c is empty after that,
remove it.

v1: https://lore.kernel.org/lkml/20220706182300.70862-4-yury.norov@gmail.com/T/
v2: - count Nth bit from 0 (was 1);
    - use 'invert' trick in _find_nth_bit(), as in _find_next_bit();
    - cleanup comments;
    - fns() is kept inline - looking at __ffs() generic implementation,
      I decided to keep it untouched.

Yury Norov (5):
  lib: add find_nth(,and,andnot)_bit()
  lib/bitmap: add tests for find_nth_bit()
  lib/bitmap: remove bitmap_ord_to_pos
  cpumask: add cpumask_nth_{,and,andnot}
  lib/nodemask: inline next_node_in() and node_random()

 MAINTAINERS              |  1 -
 include/linux/bitmap.h   |  1 -
 include/linux/bitops.h   | 19 +++++++++
 include/linux/cpumask.h  | 44 +++++++++++++++++++++
 include/linux/find.h     | 83 ++++++++++++++++++++++++++++++++++++++++
 include/linux/nodemask.h | 27 ++++++++++---
 lib/Makefile             |  2 +-
 lib/bitmap.c             | 36 ++---------------
 lib/cpumask.c            | 26 ++++++-------
 lib/find_bit.c           | 20 ++++++++++
 lib/find_bit_benchmark.c | 17 ++++++++
 lib/nodemask.c           | 31 ---------------
 lib/test_bitmap.c        | 36 ++++++++++++++++-
 13 files changed, 254 insertions(+), 89 deletions(-)
 delete mode 100644 lib/nodemask.c

-- 
2.34.1