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Message-ID: <20190428154057.GS9224@smile.fi.intel.com> Date: Sun, 28 Apr 2019 18:40:57 +0300 From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com> To: Yury Norov <yury.norov@...il.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, 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>, Yury Norov <ynorov@...vell.com>, linux-kernel@...r.kernel.org, Jens Axboe <axboe@...nel.dk>, Steffen Klassert <steffen.klassert@...unet.com> Subject: Re: [PATCH 0/4] lib: rework bitmap_parse On Sat, Apr 27, 2019 at 08:29:30PM -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. Shouldn't test ceases pass on existing code base? I would rather start series with enabling tests and then we will have a proof that before and after at least tests have not been broken. > > Tested on arm64 and BE mips. > > [1] https://lkml.org/lkml/2019/4/16/66 > > Yury Norov (6): > lib/string: add strnchrnul() > bitops: more BITS_TO_* macros > lib/bitmap: make bitmap_parse_user a wrapper on bitmap_parse > lib: rework bitmap_parse() > lib: add test for bitmap_parse() > cpumask: don't calculate length of the input string > > include/linux/bitmap.h | 8 +- > include/linux/bitops.h | 3 + > include/linux/cpumask.h | 4 +- > include/linux/string.h | 3 + > lib/bitmap.c | 197 +++++++++++++++++------------------ > lib/string.c | 20 ++++ > lib/test_bitmap.c | 102 +++++++++++++++++- > tools/include/linux/bitops.h | 9 +- > 8 files changed, 230 insertions(+), 116 deletions(-) > > -- > 2.17.1 > -- With Best Regards, Andy Shevchenko
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