LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Andrea Merello <andrea.merello@gmail.com>
To: Yury Norov <yury.norov@gmail.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Bartosz Golaszewski <bgolaszewski@baylibre.com>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	Andrea Merello <andrea.merello@iit.it>
Subject: Re: [PATCH v1 1/1] bitmap.h: add const modifier to bitmap_next_[set/clear]_region() argument
Date: Wed, 28 Jul 2021 08:39:15 +0200	[thread overview]
Message-ID: <CAN8YU5PD9i=qztMLyuFsMQFf80pz04dLOSQ0NJ9=uHb1bTh52w@mail.gmail.com> (raw)
In-Reply-To: <YQAlmBEGIaChYgeW@yury-ThinkPad>

Il giorno mar 27 lug 2021 alle ore 17:26 Yury Norov
<yury.norov@gmail.com> ha scritto:
>
> On Tue, Jul 27, 2021 at 02:48:42PM +0300, Andy Shevchenko wrote:
> > On Tue, Jul 27, 2021 at 11:44:41AM +0200, Andrea Merello wrote:
> > > Those two functions don't modify the bitmap, so their bitmap argument
> > > should be const. This patch add this.
>
> Thanks Andrea.
>
> Acked-by: Yury Norov <yury.norov@gmail.com>
>
> > Constification is always a good thing. No objections from me,
> > although Yuri is doing something with them in one of his patch series.
>
> I try to remove those two because in practice they bring more mess
> than good. All real use-cases for bitmap_next_{set,clear}_region
> relate to iterating the whole bitmap, ie nobody just wants to find a
> next region. Untill recently there was only a single user of the API,
> so I easily reworked the code to use find_first_bit/find_next bit and
> by chance return faster.

Ah, that's interesting to know: I'm working on a new driver that used
find_next_zero_bit() and find_next_bit() [0]; Andy told me that my
algorithm could be rewritten exploiting some bitmap_* helpers, so I
rewrote my code using bitmap_for_each_set_region(), which in turn uses
bitmap_next_set_region().

Should I revert to my previous implementation that uses
find_next_zero_bit() and find_next_bit() ?

[0] https://lore.kernel.org/linux-iio/20210715141742.15072-3-andrea.merello@gmail.com/

> https://github.com/norov/linux/commit/1c870b5c3fcd2eea9b351a1e0af8d1e93be78e1e
>
> Recently in next-20210716, there appeared another user in fs/btrfs/extent_io.c:
> find_next_dirty_byte(). The fun is that in that case the length of bitmap
> is 16 bit, so it's probably simpler to return the bitmap by value,
> instead of calling prologue code up to 8 times. Anyways, I'll contact
> authors of the find_next_dirty_byte() and ask if it's possible to rework
> their code.
>
> > Yuri, do you have a public repo / branch that people can base their changes to
> > bitmap stuff against of?
>
> I collected not yet upstreamed bitmap patches here:
>
> https://github.com/norov/linux/commits/bitmap-20210716

Looks like also bitmap_for_each_set_region() went away indeed ?

> Please let me know if you believe we need a more official branch for
> bitmaps. I'd encourage people to review what we already have and
> upstream it.
>
> Thanks,
> Yury
>
> > Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> >
> > > Signed-off-by: Andrea Merello <andrea.merello@iit.it>
> > > ---
> > >  include/linux/bitmap.h | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
> > > index a36cfcec4e77..ea4a8f1a2545 100644
> > > --- a/include/linux/bitmap.h
> > > +++ b/include/linux/bitmap.h
> > > @@ -458,7 +458,7 @@ static inline void bitmap_replace(unsigned long *dst,
> > >             __bitmap_replace(dst, old, new, mask, nbits);
> > >  }
> > >
> > > -static inline void bitmap_next_clear_region(unsigned long *bitmap,
> > > +static inline void bitmap_next_clear_region(const unsigned long *bitmap,
> > >                                         unsigned int *rs, unsigned int *re,
> > >                                         unsigned int end)
> > >  {
> > > @@ -466,7 +466,7 @@ static inline void bitmap_next_clear_region(unsigned long *bitmap,
> > >     *re = find_next_bit(bitmap, end, *rs + 1);
> > >  }
> > >
> > > -static inline void bitmap_next_set_region(unsigned long *bitmap,
> > > +static inline void bitmap_next_set_region(const unsigned long *bitmap,
> > >                                       unsigned int *rs, unsigned int *re,
> > >                                       unsigned int end)
> > >  {
> > > --
> > > 2.17.1
> > >
> >
> > --
> > With Best Regards,
> > Andy Shevchenko
> >

  reply	other threads:[~2021-07-28  6:39 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-27  9:44 Andrea Merello
2021-07-27 11:48 ` Andy Shevchenko
2021-07-27 15:26   ` Yury Norov
2021-07-28  6:39     ` Andrea Merello [this message]
2021-07-28  9:18       ` Andy Shevchenko
2021-07-28 13:46       ` Yury Norov

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CAN8YU5PD9i=qztMLyuFsMQFf80pz04dLOSQ0NJ9=uHb1bTh52w@mail.gmail.com' \
    --to=andrea.merello@gmail.com \
    --cc=andrea.merello@iit.it \
    --cc=andriy.shevchenko@linux.intel.com \
    --cc=bgolaszewski@baylibre.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux@rasmusvillemoes.dk \
    --cc=yury.norov@gmail.com \
    --subject='Re: [PATCH v1 1/1] bitmap.h: add const modifier to bitmap_next_[set/clear]_region() argument' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).