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Subject: Re: [PATCH 2/2] fs/dcache: Make negative dentries easier to be
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To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>, Al Viro <viro@zeniv.linux.org.uk>,
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From: Waiman Long <longman@redhat.com>
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Date: Tue, 28 Aug 2018 21:18:18 -0400
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On 08/28/2018 07:10 PM, Linus Torvalds wrote:
> On Tue, Aug 28, 2018 at 3:29 PM Waiman Long <longman@redhat.com> wrote:
>> Yes, I can rewrite it. What is the problem with the abbreviated form?
> Either gcc rewrites it for you, or you end up _actually_ using a
> function pointer and calling through it.

Yes, function pointer will be really bad.
>
> The latter would be absolutely horribly bad for something like
> "list_add()", which should expand to just a couple of instructions.
>
> And the former would be ok, except for the "you wrote code the garbage
> way, and then depended on the compiler fixing it up". Which we
> generally try to avoid in the kernel.
>
> (Don't get me wrong - we definitely depend on the compiler doing a
> good job at CSE and dead code elimination etc, but generally we try to
> avoid the whole "compiler has to rewrite code to be good" model).
>
>                  Linus

I see your point here. I will rewrite to use the regular if-then-else.

Thanks,
Longman