Re: [PATCH v2 2/3] generic/574: corrupt btrfs merkle tree data

Boris Burkov
2021-04-09T01:11:28Z

On Thu, Apr 08, 2021 at 04:16:28PM -0700, Eric Biggers wrote:
> On Thu, Apr 08, 2021 at 11:49:37AM -0700, Boris Burkov wrote:
> > On Thu, Apr 08, 2021 at 11:41:42AM -0700, Eric Biggers wrote:
> > > On Thu, Apr 08, 2021 at 11:30:12AM -0700, Boris Burkov wrote:
> > > >
> > > > Note that there is a bit of a kludge here: since btrfs_corrupt_block
> > > > doesn't handle streaming corruption bytes from stdin (I could change
> > > > that, but it feels like overkill for this purpose), I just read the
> > > > first corruption byte and duplicate it for the desired length. That is
> > > > how the test is using the interface in practice, anyway.
> > >
> > > If that's the problem, couldn't you just write the data to a temporary file?
> >
> > Sorry, I was a bit too vague. It doesn't have a file or stdin interface,
> > as far as I know.
> >
> > btrfs-corrupt-block has your typical "kitchen sink of flags" interface and
> > doesn't currently read input from streams/files. I extended that
> > interface in the simplest way to support arbitrary corruption, which
> > didn't fit with the stream based corruption this test does.
> >
> > my options seem to be:
> > shoehorn the "byte, length" interface into this test or
> > shoehorn the "stream corruption input in" interface into
> > btrfs-corrupt-block.
> >
> > I have no problem with either, the former was just less work because I
> > already wrote it that way. If the junk I did here is a deal-breaker, I
> > don't mind modifying btrfs-corrupt-block.
> >
>
> If it's a lot of trouble to handle arbitrary data, then I think you should
> change _fsv_scratch_corrupt_merkle_tree() to actually take a (byte, length) pair
> instead of data on stdin. Otherwise, _fsv_scratch_corrupt_merkle_tree() would
> claim to do one thing but actually would do a different thing on one specific
> filesystem.
>
> - Eric

It's no trouble. I think reading in corruption bytes will be a better
interface for btrfs-corrupt-block so I'll go ahead and do it.