From: Arvind Sankar <nivedita@alum.mit.edu>
To: Matthew Wilcox <willy@infradead.org>
Cc: Arvind Sankar <nivedita@alum.mit.edu>,
Linus Torvalds <torvalds@linux-foundation.org>,
"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>
Subject: Re: [GIT PULL] percpu fix for v5.9-rc6
Date: Fri, 18 Sep 2020 23:37:04 -0400 [thread overview]
Message-ID: <20200919033704.GA3014163@rani.riverdale.lan> (raw)
In-Reply-To: <20200919024556.GJ32101@casper.infradead.org>
On Sat, Sep 19, 2020 at 03:45:56AM +0100, Matthew Wilcox wrote:
> On Fri, Sep 18, 2020 at 06:39:57PM -0400, Arvind Sankar wrote:
> > On Fri, Sep 18, 2020 at 02:18:20PM -0700, Linus Torvalds wrote:
> > > On Fri, Sep 18, 2020 at 2:00 PM Arvind Sankar <nivedita@alum.mit.edu> wrote:
> > > >
> > > > You could just assert that offsetof(typeof(s),flex) == sizeof(s), no?
> > >
> > > No, because the whole point is that I want that "sizeof(s)" to *WARN*.
> >
> > Ouch, offsetof() and sizeof() will give different results in the
> > presence of alignment padding.
> >
> > https://godbolt.org/z/rqnxTK
>
> We really should be using offsetof() then. It's harmless because we're
> currently overallocating, not underallocating. The test case I did was:
>
I wonder if there are cases where we know the total size, and are
working out the number of elements in the flexible array by doing
size - sizeof(s).
Would a macro to do the inverse of struct_size(), i.e. get the count
knowing the total size be useful?
next prev parent reply other threads:[~2020-09-19 3:37 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-17 20:45 Dennis Zhou
2020-09-18 1:05 ` Linus Torvalds
2020-09-18 16:23 ` Gustavo A. R. Silva
2020-09-18 17:23 ` Linus Torvalds
2020-09-18 19:34 ` Gustavo A. R. Silva
2020-09-18 19:37 ` Linus Torvalds
2020-09-18 20:02 ` Matthew Wilcox
2020-09-18 20:14 ` Linus Torvalds
2020-09-18 20:29 ` Arvind Sankar
2020-09-18 20:40 ` Linus Torvalds
2020-09-18 21:00 ` Arvind Sankar
2020-09-18 21:18 ` Linus Torvalds
2020-09-18 22:39 ` Arvind Sankar
2020-09-19 1:28 ` Linus Torvalds
2020-09-19 2:53 ` Arvind Sankar
2020-09-19 3:02 ` Matthew Wilcox
2020-09-19 3:04 ` Linus Torvalds
2020-09-19 2:45 ` Matthew Wilcox
2020-09-19 3:37 ` Arvind Sankar [this message]
2020-09-19 15:15 ` David Laight
2020-09-18 20:03 ` Gustavo A. R. Silva
2020-09-18 1:10 ` pr-tracker-bot
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