linux-kernel - Re: [PATCH 4/5] m68k,mm: Extend table allocator for multiple sizes

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Message-ID: <20200129124352.GP14879@hirez.programming.kicks-ass.net>
Date:   Wed, 29 Jan 2020 13:43:52 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Will Deacon <will@...nel.org>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-m68k@...ts.linux-m68k.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/5] m68k,mm: Extend table allocator for multiple sizes

On Wed, Jan 29, 2020 at 12:17:53PM +0000, Will Deacon wrote:
> On Wed, Jan 29, 2020 at 11:39:45AM +0100, Peter Zijlstra wrote:

> > +extern void *get_pointer_table(int type);
> 
> Could be prettier/obfuscated with an enum type?

Definitely, but then we get to bike-shed on names :-)

enum m68k_table_type {
	TABLE_BIG = 0,
	TABLE_SMALL,
};

Is not exactly _that_ much better, and while TABLE_PTE works,
TABLE_PGD_PMD is a bit crap.

> > --- a/arch/m68k/mm/memory.c
> > +++ b/arch/m68k/mm/memory.c

> > -pmd_t *get_pointer_table (void)
> > +void *get_pointer_table (int type)
> >  {
> > -	ptable_desc *dp = ptable_list.next;
> > -	unsigned char mask = PD_MARKBITS (dp);
> > -	unsigned char tmp;
> > -	unsigned int off;
> > +	ptable_desc *dp = ptable_list[type].next;
> > +	unsigned int mask, tmp, off;
> 
> nit, but if you do:
> 
> 	unsigned int mask = list_empty(&ptable_list[type]) ? 0 : PD_MARKBITS(dp);
> 
> then you can leave the existing mask logic as-is.

Indeed!