Re: Reproducer for "compressed data + hole data corruption bug, 2018 edition" still works on 4.20.7

[Christoph Anton Mitterer <calestyo@scientia.net>]

On Fri, 2019-02-15 at 12:02 +0000, Filipe Manana wrote:
> Upgrade to a kernel with the patch (none yet) or build it from
> source?
> Not sure what kind of advice you are looking for.

Well more something of the kind that Zygo wrote in his mail, i.e some
explanation of the whole issue in order to find out whether one might
be affected or not.


> As I said in the previous reply, and in the patch's changelog [1],
> the
> corruption happens at read time.
> That means nothing stored on disk is corrupted. It's not the end of
> the world.

Well but there are many cases where data is read and then written
again... and while Zygo's mail already answers a lot, at least the
question of whether it could happen on btrfs send/receive is still
open.


My understanding was that btrfs is considered "stable" for the normal
use cases (so e.g. perhaps without special features like raid56).

Data corruption is always quite serious, even if it's just on reads and
people may have workloads where data is read (possibly with corruption)
and (permanently) written again... so the whole thing *could* be quite
serious and IMO justifies a more thorough explanation for end-users and
not just a small commit message for developers.


Also, while it was really great to see how fast this got fixed then in
the end... it's also a bit worrying that Zygo apparently reported it
already some time ago and it got somehow lost.



Cheers,
Chris.