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

Tejun Heo
2017-01-09T19:41:12Z

Hello, Geert.

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.

Thanks.

--
tejun