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From: Nick Desaulniers <ndesaulniers@google.com>
Date: Tue, 14 Sep 2021 12:50:44 -0700
Message-ID: <CAKwvOdk9yqEMLTAxgZNmHgRSww0AnJ-x9qd7HK3v2Vepi1BdLw@mail.gmail.com>
Subject: Re: [PATCH 5.10] overflow.h: use new generic division helpers to
 avoid / operator
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Kees Cook <keescook@chromium.org>, Josef Bacik <josef@toxicpanda.com>, 
	Jens Axboe <axboe@kernel.dk>, Rasmus Villemoes <linux@rasmusvillemoes.dk>, 
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Sasha Levin <sashal@kernel.org>, llvm@lists.linux.dev, 
	stable <stable@vger.kernel.org>, Arnd Bergmann <arnd@kernel.org>, 
	Naresh Kamboju <naresh.kamboju@linaro.org>, Nathan Chancellor <nathan@kernel.org>, 
	Stephen Rothwell <sfr@canb.auug.org.au>, Pavel Machek <pavel@ucw.cz>
Content-Type: text/plain; charset="UTF-8"

On Tue, Sep 14, 2021 at 12:46 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Tue, Sep 14, 2021 at 12:10 PM Nick Desaulniers
> <ndesaulniers@google.com> wrote:
> >
> > Isn't the parameter `blksize` of `nbd_set_size` declared as `loff_t`?
>
> So?
>
> I'm not seeing your point.
>
> We've checked the range of it - in loff_t.
>
> So the *value* is already checked, and most definitely fits in 'unsigned long'.
>
> So __ffs() is perfectly fine. It will truncate that loff_t to a sane type.
>
> What is the problem you're trying to solve?

Just making sure __ffs() works as expected should blksize > LONG_MAX
on 32b targets.  I don't see the range check you're referring to.
loff_t is a long long, yeah?
-- 
Thanks,
~Nick Desaulniers