Messages in this thread | | | From | Andrea Merello <> | Date | Wed, 28 Jul 2021 08:39:15 +0200 | Subject | Re: [PATCH v1 1/1] bitmap.h: add const modifier to bitmap_next_[set/clear]_region() argument |
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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 > >
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