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    SubjectRe: [PATCH 0/7] lib: rework bitmap_parse
    On Tue, Apr 30, 2019 at 06:06:29PM -0700, Yury Norov wrote:
    > 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.

    Any comments?

    > 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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