[Re: [PATCH 3/8] lib: bitmap: fold nbits into region struct] On 26/01/2021 (Tue
23:16) Andy Shevchenko wrote:
> On Tue, Jan 26, 2021 at 12:11:36PM -0500, Paul Gortmaker wrote:
> > This will reduce parameter passing and enable using nbits as part
> > of future dynamic region parameter parsing.
>
> One nit below, nevertheless
> Reviewed-by: Andy Shevchenko <andriy.shevche...@linux.intel.com>
>
> > Cc: Yury Norov <yury.no...@gmail.com>
> > Cc: Rasmus Villemoes <li...@rasmusvillemoes.dk>
> > Cc: Andy Shevchenko <andriy.shevche...@linux.intel.com>
> > Suggested-by: Yury Norov <yury.no...@gmail.com>
> > Signed-off-by: Paul Gortmaker <paul.gortma...@windriver.com>
> > ---
> > lib/bitmap.c | 19 ++++++++++---------
> > 1 file changed, 10 insertions(+), 9 deletions(-)
> >
> > diff --git a/lib/bitmap.c b/lib/bitmap.c
> > index 75006c4036e9..162e2850c622 100644
> > --- a/lib/bitmap.c
> > +++ b/lib/bitmap.c
> > @@ -487,24 +487,24 @@ EXPORT_SYMBOL(bitmap_print_to_pagebuf);
> >
> > /*
> > * Region 9-38:4/10 describes the following bitmap structure:
> > - * 0 9 12 18 38
> > - * .........****......****......****......
> > - * ^ ^ ^ ^
> > - * start off group_len end
> > + * 0 9 12 18 38 N
> > + * .........****......****......****..................
> > + * ^ ^ ^ ^ ^
> > + * start off group_len end nbits
> > */
> > struct region {
> > unsigned int start;
> > unsigned int off;
> > unsigned int group_len;
> > unsigned int end;
> > + unsigned int nbits;
> > };
> >
> > -static int bitmap_set_region(const struct region *r,
> > - unsigned long *bitmap, int nbits)
> > +static int bitmap_set_region(const struct region *r, unsigned long *bitmap)
> > {
> > unsigned int start;
> >
> > - if (r->end >= nbits)
> > + if (r->end >= r->nbits)
> > return -ERANGE;
> >
> > for (start = r->start; start <= r->end; start += r->group_len)
> > @@ -640,7 +640,8 @@ int bitmap_parselist(const char *buf, unsigned long
> > *maskp, int nmaskbits)
> > struct region r;
> > long ret;
> >
> > - bitmap_zero(maskp, nmaskbits);
> > + r.nbits = nmaskbits;
>
> > + bitmap_zero(maskp, r.nbits);
>
> This sounds not right from style perspective.
> You have completely uninitialized r on stack, then you assign only one value
> for immediate use here and...
So, this change was added because Yury suggested that I "..store
nmaskbits in the struct region, and avoid passing nmaskbits as a
parameter."
To which I originally noted "I considered that and went with the param
so as to not open the door to someone possibly using an uninitialized
struct value later."
https://lore.kernel.org/lkml/20210122044357.gs16...@windriver.com/
Looking back, I had a similar thought as to yours, it seems...
I am also thinking more and more that nbits doesn't belong in the
region anyway - yes, a region gets validated against a specific nbits
eventually, but it doesn't need an nbits field to be a complete
specification. The region "0-3" is a complete specification for "the
1st four cores" and is as valid on a 4 core machine as it is on a 64 core
machine -- a validation we do when we deploy the region on that machine.
I will set this change aside and get the nbits value to getnum() another
way, and leave the region struct as it was -- without a nbits field.
This will also resolve having the macro handling of region that you were
not really liking.
Paul.
--
> > while (buf) {
> > buf = bitmap_find_region(buf);
> > @@ -655,7 +656,7 @@ int bitmap_parselist(const char *buf, unsigned long
> > *maskp, int nmaskbits)
> > if (ret)
> > return ret;
> >
> > - ret = bitmap_set_region(&r, maskp, nmaskbits);
> > + ret = bitmap_set_region(&r, maskp);
>
> ...hiding this fact here. Which I would expect that &r may be rewritten here.
>
> I would leave these unchanged and simple assign the value in
> bitmap_set_region().
>
> > if (ret)
> > return ret;
> > }
> > --
> > 2.17.1
> >
>
> --
> With Best Regards,
> Andy Shevchenko
>
>
