bug#41607: Deleted store items are not actually deleted

[zimoun <zimon.toutoune@gmail.com>]

Hi Chris,

Thank you for the detailed explanations.

On Sun, 31 May 2020 at 06:57, Chris Marusich <cmmarusich@gmail.com> wrote:

> The trash directory is on the "top layer" because it gets created in the
> running container.  However, in practice many store items from lower
> layers are made dead when Stephen's script runs "guix pull" and deletes
> the old profiles.  If any of those store items were directories,
> guix-daemon will fail to GC them because of an XDEV error.  If this is
> confusing to you, I suggest you experiment with Docker a little bit, and
> look closely at the steps that Stephen's script is running.  I outlined
> this in the email I accidentally deleted, but I'm a little too tired to
> reproduce it all a second time.  I hope you'll understand.
>
> Should Guix do anything about this?  We could change guix-daemon to take
> correct action in the face of an XDEV error.  We could also improve the
> logging, since currently it silently swallows the XDEV error.

What is the correct action?  Because somehow these items cannot be
removed of the Docker chained images.
However, the logging could report the ``error", e.g., "guix gc" lists
all the items and their size and currently it says "[0MiB] deleting"
so instead it could say "[XDEV error] not valid" with some words about
that in the manual, section "Invking guix gc".  WDYT?



Cheers,
simon