On Wed, Nov 08, 2017 at 10:17:28AM -0700, Chris Murphy wrote:
> On Wed, Nov 8, 2017 at 5:13 AM, Austin S. Hemmelgarn
> <ahferroin7@gmail.com> wrote:
> 
> >> It definitely does fix ups during normal operations. During reads, if
> >> there's a UNC or there's corruption detected, Btrfs gets the good
> >> copy, and does a (I think it's an overwrite, not COW) fixup. Fixups
> >> don't just happen with scrubbing. Even raid56 supports these kinds of
> >> passive fixups back to disk.
> >
> > I could have sworn it didn't rewrite the data on-disk during normal usage.
> > I mean, I know for certain that it will return the correct data to userspace
> > if at all possible, but I was under the impression it will just log the
> > error during normal operation.
> 
> No, everything except raid56 has had it since a long time, I can't
> even think how far back, maybe even before 3.0. Whereas raid56 got it
> in 4.12.

   Yes, I'm pretty sure it's been like that ever since I've been using
btrfs (somewhere around the early neolithic).

   Hugo.

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