Re: [PATCH -next v2 2/2] blk-throttle: fix io hung due to configuration updates

[yukuai (C)]

在 2022/05/19 15:01, Geert Uytterhoeven 写道:
> Hi Yukuai,
>
> On Thu, May 19, 2022 at 5:25 AM yukuai (C) <yukuai3@xxxxxxxxxx> wrote:
> > 在 2022/05/19 10:11, yukuai (C) 写道:
> > > 在 2022/05/18 23:52, kernel test robot 写道:
> > > > Thank you for the patch! Yet something to improve:
> > > >
> > > > [auto build test ERROR on next-20220517]
> > > >
> > > > url:
> > > > https://github.com/intel-lab-lkp/linux/commits/Yu-Kuai/bugfix-for-blk-throttle/20220518-151713
> > > >
> > > > base:    47c1c54d1bcd0a69a56b49473bc20f17b70e5242
> > > > config: m68k-allyesconfig
> > > > (https://download.01.org/0day-ci/archive/20220518/202205182347.tMOOqyfL-lkp@xxxxxxxxx/config)
> > > >
> > > > compiler: m68k-linux-gcc (GCC) 11.3.0
> > > > reproduce (this is a W=1 build):
> > > >           wget
> > > > https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross
> > > > -O ~/bin/make.cross
> > > >           chmod +x ~/bin/make.cross
> > > >           #
> > > > https://github.com/intel-lab-lkp/linux/commit/f8345dbaf4ed491742aab29834aff66b4930c087
> > > >
> > > >           git remote add linux-review
> > > > https://github.com/intel-lab-lkp/linux
> > > >           git fetch --no-tags linux-review
> > > > Yu-Kuai/bugfix-for-blk-throttle/20220518-151713
> > > >           git checkout f8345dbaf4ed491742aab29834aff66b4930c087
> > > >           # save the config file
> > > >           mkdir build_dir && cp config build_dir/.config
> > > >           COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.3.0
> > > > make.cross W=1 O=build_dir ARCH=m68k SHELL=/bin/bash
> > > >
> > > > If you fix the issue, kindly add following tag as appropriate
> > > > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > > >
> > > > All errors (new ones prefixed by >>):
> > > >
> > > >      m68k-linux-ld: block/blk-throttle.o: in function `tg_conf_updated':
> > > > > > blk-throttle.c:(.text+0x25bc): undefined reference to `__udivdi3'
> > > > > > m68k-linux-ld: blk-throttle.c:(.text+0x2626): undefined reference to
> > > > > > `__udivdi3'
> > > Hi,
> > >
> > > I'm confused here, the only place that I can relate to this:
> > >
> > >       return dispatched * new_limit / old_limit;
> > >
> > > However, I don't understand yet why this is problematic...
> > > >      `.exit.text' referenced in section `.data' of
> > > > sound/soc/codecs/tlv320adc3xxx.o: defined in discarded section
> > > > `.exit.text' of sound/soc/codecs/tlv320adc3xxx.o
> >
> > + static u64 throtl_update_bytes_disp(u64 dispatched, u64 new_limit,
> > +                                    u64 old_limit)
> > + {
> > +        if (new_limit == old_limit)
> > +                return dispatched;
> > +
> > +        if (new_limit == U64_MAX)
> > +                return 0;
> > +
> > +        return dispatched * new_limit / old_limit;
> >
> > I understand it now. I'm doing (u64 / u64), I should use div64_u64
>
> Better, use mul_u64_u64_div_u64(), as "dispatched * new_limit"
> may overflow?
Hi,

It's right that it  can overflow, I'll handle such case in next version.
> > + }
> > +
> > + static u32 throtl_update_io_disp(u32 dispatched, u32 new_limit, u32 old_limit)
> > + {
> > +        if (new_limit == old_limit)
> > +                return dispatched;
> > +
> > +        if (new_limit == UINT_MAX)
> > +                return 0;
> > +
> > +        return dispatched * new_limit / old_limit;
>
> This is the same as above, but now operating on u32s instead of u64s.
> Likewise, can the multiplication overflow?
same as above.

Thanks,
Kuai
> > + }
>
> Gr{oetje,eeting}s,
>
>                          Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                  -- Linus Torvalds
> .