From: Andy Shevchenko <andriy.shevchenko@linux•intel.com>
To: "Jason A. Donenfeld" <Jason@zx2c4•com>
Cc: Jason Gunthorpe <jgg@ziepe•ca>,
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Subject: Re: [PATCH v1 3/5] treewide: use get_random_u32() when possible
Date: Thu, 6 Oct 2022 16:20:31 +0300 [thread overview]
Message-ID: <Yz7WHyD+teLOh2ho@smile.fi.intel.com> (raw)
In-Reply-To: <CAHmME9r_vNRFFjUvqx8QkBddg_kQU=FMgpk9TqOVZdvX6zXHNg@mail.gmail.com>
On Thu, Oct 06, 2022 at 07:05:48AM -0600, Jason A. Donenfeld wrote:
> On Thu, Oct 6, 2022 at 6:47 AM Jason Gunthorpe <jgg@ziepe•ca> wrote:
> > On Wed, Oct 05, 2022 at 11:48:42PM +0200, Jason A. Donenfeld wrote:
...
> > > - u32 isn = (prandom_u32() & ~7UL) - 1;
> > > + u32 isn = (get_random_u32() & ~7UL) - 1;
> >
> > Maybe this wants to be written as
> >
> > (prandom_max(U32_MAX >> 7) << 7) | 7
> > ?
>
> Holy smokes. Yea I guess maybe? It doesn't exactly gain anything or
> make the code clearer though, and is a little bit more magical than
> I'd like on a first pass.
Shouldn't the two first 7s to be 3s?
...
> > > - psn = prandom_u32() & 0xffffff;
> > > + psn = get_random_u32() & 0xffffff;
> >
> > prandom_max(0xffffff + 1)
>
> That'd work, but again it's not more clear. Authors here are going for
> a 24-bit number, and masking seems like a clear way to express that.
We have some 24-bit APIs (and 48-bit) already in kernel, why not to have
get_random_u24() ?
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2022-10-06 13:20 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-05 21:48 [PATCH v1 0/5] treewide cleanup of random integer usage Jason A. Donenfeld
2022-10-05 21:48 ` [PATCH v1 1/5] treewide: use prandom_u32_max() when possible Jason A. Donenfeld
2022-10-05 21:48 ` [PATCH v1 2/5] treewide: use get_random_{u8,u16}() " Jason A. Donenfeld
2022-10-06 13:37 ` Toke Høiland-Jørgensen
2022-10-05 21:48 ` [PATCH v1 3/5] treewide: use get_random_u32() " Jason A. Donenfeld
[not found] ` <20221006084331.4bdktc2zlvbaszym@quack3>
[not found] ` <Yz7LCyIAHC6l5mG9@zx2c4.com>
2022-10-06 13:01 ` [f2fs-dev] " Andy Shevchenko
2022-10-06 13:07 ` Jason A. Donenfeld
[not found] ` <Yz7OdfKZeGkpZSKb@ziepe.ca>
[not found] ` <CAHmME9r_vNRFFjUvqx8QkBddg_kQU=FMgpk9TqOVZdvX6zXHNg@mail.gmail.com>
2022-10-06 13:15 ` Jason Gunthorpe
2022-10-06 13:20 ` Andy Shevchenko [this message]
2022-10-06 13:38 ` Toke Høiland-Jørgensen
2022-10-12 19:16 ` Joe Perches
2022-10-12 21:29 ` David Laight
2022-10-13 1:37 ` Joe Perches
2022-10-05 21:48 ` [PATCH v1 4/5] treewide: use get_random_bytes " Jason A. Donenfeld
2022-10-05 21:48 ` [PATCH v1 5/5] prandom: remove unused functions Jason A. Donenfeld
2022-10-06 6:15 ` [PATCH v1 0/5] treewide cleanup of random integer usage Kees Cook
2022-10-06 12:58 ` Jason A. Donenfeld
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