Re: [Libguestfs] [PATCH nbdkit 5/5] New filter: evil
On Tue, May 16, 2023 at 05:24:58PM +0100, Richard W.M. Jones wrote:
> > +
> > +# If we read subsets they should match the contents of the buffer.
> > +buf1 = h.pread(1000, 1000)
> > +assert(buf1 == buf[1000:2000])
> > +
> > +buf1 = h.pread(10000, 999)
> > +assert(buf1 == buf[999:10999])
>
> Should we also assert that there is at least one stuck bit in those
> two ranges, and/or pick a different or larger range to improve the
> chances of that being the case?
So I think you mean pick a range where we know there is a stuck bit
before doing the read + assert. I will see. With a 1:800,000 chance,
it's not likely the ranges as written would have stuck bits so we're
comparing zeroes ...
Engineering tradeoffs - we can run a test with a pinned seed to
deterministically know where the stuck bits will be, but it has to be
separate from tests where we want the pseudo-random behavior to differ
between runs but still demonstrate that our approximations are getting
around the ratio of set bits that we expected.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org