Messages in this thread | | | Date | Wed, 27 Jan 2021 03:02:06 -0500 | From | Paul Gortmaker <> | Subject | Re: [PATCH 3/8] lib: bitmap: fold nbits into region struct |
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[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.shevchenko@linux.intel.com> > > > Cc: Yury Norov <yury.norov@gmail.com> > > Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> > > Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> > > Suggested-by: Yury Norov <yury.norov@gmail.com> > > Signed-off-by: Paul Gortmaker <paul.gortmaker@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.GS16838@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 > >
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