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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Fri, 18 Sep 2020 13:14:54 -0700
Message-ID: <CAHk-=wiNjJGhAMBwYixwkADpNharvcuOG-AMCdii1q_Xo_Ky_A@mail.gmail.com>
Subject: Re: [GIT PULL] percpu fix for v5.9-rc6
To:     Matthew Wilcox <willy@infradead.org>
Cc:     "Gustavo A. R. Silva" <gustavoars@kernel.org>,
        Dennis Zhou <dennis@kernel.org>, Tejun Heo <tj@kernel.org>,
        Christoph Lameter <cl@linux.com>,
        Linux-MM <linux-mm@kvack.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Kees Cook <keescook@chromium.org>
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On Fri, Sep 18, 2020 at 1:02 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> I suppose it's not really necessary, we could do offsetof here, right?

Yup, that would make a lot more sense.

But right now, the sizeof() obviously silently works.

As do a number of other fairly nonsensical things, like assigning a struct etc.

And yes, I realize we may well do that too. But I think that's a
dangerous pattern too, ie doing

   *a = *b;

silently works, and copies everything but the final array.

And yes - none of this is _worse_ than using zero-sized arrays, but
the point is that it isn't better either.

            Linus