bug#30875: Garbage collector may leave empty files

[ludo@gnu.org (Ludovic Courtès)]

Hello,

Marius Bakke <mbakke@fastmail.com> skribis:

> Recently I've seen a couple of instances like these:
>
> exporting path `/gnu/store/mi1rbw8fdsbi4bc4pndbb6smq39722vm-baobab-3.26.1.tar.xz'
> guix offload: error: build failed: hash of path `/gnu/store/mi1rbw8fdsbi4bc4pndbb6smq39722vm-baobab-3.26.1.tar.xz' has changed from `4223b4813b2253e68ea2b824d0d0e284ff75714ad0faf5a33d65a78df6b65915' to `77ac62e2629d8e45f624589c0c8bf99e24b3a722349bf1e79bc186008534e246'!
> cannot build derivation `/gnu/store/jbx6a4n1d55dpydr87d11m7xwapm3pcx-gnome-3.24.3.drv': 1 dependencies couldn't be built
>
> Without the build hook, it manifests as:
>
> starting phase `unpack'
> tar: This does not look like a tar archive
> xz: (stdin): File format not recognized
> tar: Child returned status 1
> tar: Error is not recoverable: exiting now
>
> There was another instance on help-guix recently with a user having
> empty .drv files in the store.
>
> There is a bug lurking here somewhere, but I'm not sure where to start
> looking.
>
> $ find /gnu/store/ -maxdepth 1 -size 0 | grep -v '\.lock$' | wc -l
> 24

Are we sure this is a Guix issue and not a disk or file system
corruption issue?  The relevant code in guix-daemon hasn’t changed in
ages.

What file system are you using?  Btrfs?  :-)

Thanks,
Ludo’.