linux-kernel - Re: [PATCH v12 1/3] lib/bitmap: add bitmap

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Date:   Mon, 4 Dec 2023 06:22:20 -0800
From:   Yury Norov <yury.norov@...il.com>
To:     Alexander Potapenko <glider@...gle.com>
Cc:     catalin.marinas@....com, will@...nel.org, pcc@...gle.com,
        andreyknvl@...il.com, andriy.shevchenko@...ux.intel.com,
        aleksander.lobakin@...el.com, linux@...musvillemoes.dk,
        alexandru.elisei@....com, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, eugenis@...gle.com,
        syednwaris@...il.com, william.gray@...aro.org,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v12 1/3] lib/bitmap: add bitmap_{read,write}()

On Mon, Dec 04, 2023 at 02:28:09PM +0100, Alexander Potapenko wrote:
> On Thu, Nov 9, 2023 at 4:11 PM Alexander Potapenko <glider@...gle.com> wrote:
> >
> > From: Syed Nayyar Waris <syednwaris@...il.com>
> >
> > The two new functions allow reading/writing values of length up to
> > BITS_PER_LONG bits at arbitrary position in the bitmap.
> >
> > The code was taken from "bitops: Introduce the for_each_set_clump macro"
> > by Syed Nayyar Waris with a number of changes and simplifications:
> >  - instead of using roundup(), which adds an unnecessary dependency
> >    on <linux/math.h>, we calculate space as BITS_PER_LONG-offset;
> >  - indentation is reduced by not using else-clauses (suggested by
> >    checkpatch for bitmap_get_value());
> >  - bitmap_get_value()/bitmap_set_value() are renamed to bitmap_read()
> >    and bitmap_write();
> >  - some redundant computations are omitted.
> >
> > Cc: Arnd Bergmann <arnd@...db.de>
> > Signed-off-by: Syed Nayyar Waris <syednwaris@...il.com>
> > Signed-off-by: William Breathitt Gray <william.gray@...aro.org>
> > Link: https://lore.kernel.org/lkml/fe12eedf3666f4af5138de0e70b67a07c7f40338.1592224129.git.syednwaris@gmail.com/
> > Suggested-by: Yury Norov <yury.norov@...il.com>
> > Co-developed-by: Alexander Potapenko <glider@...gle.com>
> > Signed-off-by: Alexander Potapenko <glider@...gle.com>
> > Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> 
> Yury, Andy, do you think anything else is needed for this series?
> If not, whom should we ask to take it?

I probably need to revisit it, but generally it looks OK.

But I can't take new API without having real users. Now that your MTE
series is delayed, and Alexander's 'ip_tunnel flags' is not moving as
well, there's non-zero chance to merge dead code.

If you want it to be merged, I'd advise you to walk through the kernel
sources and find good cases where bitmap_read() and bitmap_write() can
be used. Then append this series with such conversions, and I'll be
able to move it.

Thanks,
Yury