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Date:   Tue, 30 Apr 2019 18:06:29 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Amritha Nambiar <amritha.nambiar@...el.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Matthew Wilcox <willy@...radead.org>,
        "Tobin C . Harding" <tobin@...nel.org>,
        Will Deacon <will.deacon@....com>,
        Miklos Szeredi <mszeredi@...hat.com>,
        Vineet Gupta <vineet.gupta1@...opsys.com>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        linux-kernel@...r.kernel.org
Cc:     Yury Norov <ynorov@...vell.com>, Yury Norov <yury.norov@...il.com>,
        Jens Axboe <axboe@...nel.dk>,
        Steffen Klassert <steffen.klassert@...unet.com>
Subject: [PATCH 0/7] lib: rework bitmap_parse

On top of next-20190418.

Similarly to recently revisited bitmap_parselist() [1],
bitmap_parse() is ineffective and overcomplicated.  This
series reworks it, aligns its interface with bitmap_parselist()
and makes usage simpler.

The series also adds a test for the function and fixes usage of it
in cpumask_parse() according to new design - drops the calculating
of length of an input string.

The following users would also consider to drop the length argument,
if possible:
drivers/block/drbd/drbd_main.c:2608
kernel/padata.c:924
net/core/net-sysfs.c:726
net/core/net-sysfs.c:1309
net/core/net-sysfs.c:1391

bitmap_parse() takes the array of numbers to be put into the map in
the BE order which is reversed to the natural LE order for bitmaps.
For example, to construct bitmap containing a bit on the position 42,
we have to put a line '400,0'. Current implementation reads chunk
one by one from the beginning ('400' before '0') and makes bitmap
shift after each successful parse. It makes the complexity of the
whole process as O(n^2). We can do it in reverse direction ('0'
before '400') and avoid shifting, but it requires reverse parsing
helpers.

Tested on arm64 and BE mips.

v1: https://lkml.org/lkml/2019/4/27/597
v2:
 - strnchrnul() signature and description changed, ifdeffery and
   exporting removed;
 - test split for better demonstration of before/after changes;
 - minor naming and formatting issues fixed.

[1] https://lkml.org/lkml/2019/4/16/66

Yury Norov (7):
  lib/string: add strnchrnul()
  bitops: more BITS_TO_* macros
  lib: add test for bitmap_parse()
  lib: make bitmap_parse_user a wrapper on bitmap_parse
  lib: rework bitmap_parse()
  lib: new testcases for bitmap_parse{_user}
  cpumask: don't calculate length of the input string

 include/linux/bitmap.h       |   8 +-
 include/linux/bitops.h       |   5 +-
 include/linux/cpumask.h      |   4 +-
 include/linux/string.h       |   1 +
 lib/bitmap.c                 | 197 +++++++++++++++++------------------
 lib/string.c                 |  17 +++
 lib/test_bitmap.c            | 102 +++++++++++++++++-
 tools/include/linux/bitops.h |   9 +-
 8 files changed, 226 insertions(+), 117 deletions(-)

-- 
2.17.1

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