linux-kernel - Re: cocci script to convert linux-kernel allocs with BITS_TO_LONGS to bitmap

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Date:   Sat, 10 Jul 2021 22:09:15 +0200 (CEST)
From:   Julia Lawall <julia.lawall@...ia.fr>
To:     Joe Perches <joe@...ches.com>
cc:     cocci <cocci@...teme.lip6.fr>, LKML <linux-kernel@...r.kernel.org>,
        kernel-janitors@...r.kernel.org
Subject: Re: cocci script to convert linux-kernel allocs with BITS_TO_LONGS
 to bitmap_alloc



On Sat, 10 Jul 2021, Joe Perches wrote:

> On Sat, 2021-07-10 at 21:50 +0200, Julia Lawall wrote:
> > On Fri, 9 Jul 2021, Joe Perches wrote:
> >
> > > Here is a cocci script to convert various types of bitmap allocations
> > > that use BITS_TO_LONGS to the more typical bitmap_alloc functions.
> > >
> > > Perhaps something like it could be added to scripts/coccinelle.
> > > The diff produced by the script is also below.
> > >
> > > $ cat bitmap_allocs.cocci
> > > // typical uses of bitmap allocations
> []
> > > @@
> > > expression val;
> > > expression e1;
> > > expression e2;
> > > @@
> > >
> > > -	val = kcalloc(BITS_TO_LONGS(e1), sizeof(*val), e2)
> > > +	val = bitmap_zalloc(e1, e2)
> >
> > Is there something that guarantees that val has a type that has a size that
> > is the same as a long?
>
> no, but afaict, all do.

It might be nicer for the val metavariable to be declared as
{long,unsigned long} val;, although that might lose some results if the
type is something else that has the same size.  I can check what is the
impact of adding that constraint.

julia