Re: [PATCH] btrfs-progs: utils: use better wrappered random generator

[Hugo Mills <hugo@carfax.org.uk>]

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On Wed, May 25, 2016 at 01:11:38PM +0200, David Sterba wrote:
> On Wed, May 25, 2016 at 08:33:45AM +0800, Qu Wenruo wrote:
> > 
> > 
> > David Sterba wrote on 2016/05/24 11:51 +0200:
> > > On Tue, May 24, 2016 at 08:31:01AM +0800, Qu Wenruo wrote:
> > >>> This could be made static (with thread local storage) so the state does
> > >>> not get regenerated all the time. Possibly it could be initialize from
> > >>> some true random source, not time or pid.
> > >>
> > >> I also considered true random source like /dev/random, but since it's
> > >> possible to wait for entropy pool, it would be quite slow and confusing
> > >> for users.
> > >
> > > How would it be confusing? We'll once seed the random generator from
> > > /dev/random, reading 3 * 16bit for the nrand generator context.
> > 
> > Reading from /dev/random may sleep, until the entropy pool is filled.
> 
> I know, but does this apply in our case? We're going to get just a few
> bytes to seed.  I want to avoid inventing own random number generation
> schemes, so we'll use a standard random number source or API.
> 
> /dev/random gives about 1-2MB/s of random data on several machines I've
> tried.

   Just use /dev/urandom?

   See, e.g. http://www.2uo.de/myths-about-urandom/

   Hugo.

-- 
Hugo Mills             | Putting U back in Honor, Valor, and Trth.
hugo@... carfax.org.uk |
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