Re: [PATCH] libata-eh: Use switch() instead of sparse array for protocol strings

Geert Uytterhoeven
2017-01-09T20:28:12Z

Hi Tejun,

On Mon, Jan 9, 2017 at 8:41 PM, Tejun Heo <tj@kernel.org> wrote:
> On Mon, Jan 09, 2017 at 07:25:31PM +0100, Geert Uytterhoeven wrote:
>> On Mon, Jan 9, 2017 at 6:31 PM, Tejun Heo <tj@kernel.org> wrote:
>> > On Mon, Jan 09, 2017 at 09:27:23AM -0800, Christoph Hellwig wrote:
>> >> On Mon, Jan 09, 2017 at 05:30:02PM +0100, Geert Uytterhoeven wrote:
>> >> > > ata_force_param_buf is __initdata and shouldn't really matter.
>> >> >
>> >> > It mainly matters because of e.g. bootloader limitations.
>> >>
>> >> Do we need a full 4k for the force parameters? What would a typical
>> >> command line for it look like?
>> >
>> > Maybe a couple hundreds bytes at max, but it's a bit weird to restrict
>> > this given that it is bss, not gigantic and __initdata. What kind of
>> > bootloader limitations are we talking about?
>>
>> Some boot loaders start overwriting themselves or the passed DTB if the
>> kernel becomes too big.
>> If I'm not mistaken, bss is still expanded early (verified, increasing bss
>> can trigger the above problem).
>
> So, to avoid that, we can just kmalloc and kfree the buffer, but it
> seems like a silly complication to work around bugs in some
> bootloaders. There are many places in kernel where we're liberal
> about __initdata which is great. I'm not sure complicating all those
> places for a broken bootloader is a good idea.

Sure. We cannot avoid that kernels (esp. multiplatform) keep on growing.

But when I see a new 4KiB-sized buffer, i'm always suspicious...
A few years ago, I caught someone miscalculating shifts, leading
to a static buffer that was 256 times larger than intended ;-)

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds