Re: [PATCH] linux/bitmap.h: fix BITMAP_LAST_WORD_MASK

[Wei Wang]

On 07/26/2018 04:48 PM, Andy Shevchenko wrote:
> On Thu, Jul 26, 2018 at 11:07 AM, Wei Wang <wei.w.wang@xxxxxxxxx> wrote:
> > The existing BITMAP_LAST_WORD_MASK macro returns 0xffffffff if nbits is
> > 0. This patch changes the macro to return 0 when there is no bit needs to
> > be masked.
> Can you provide a practical example of what's going wrong before this
> patch applied?

The reason of making this patch is that I saw some other software which 
ports this function and has possibilities to fall into bugs with usages 
which pass 0 to the macro. So I wonder if it would be necessary to make 
such changes in case we would get a similar bug. Or adding something to 
explain that "0" is not applicable to this macro as a reminder to people 
who would use it.

Best,
Wei