Fix potential data loss and corruption due to Incorrect BIO Chain Handling

[Andreas Gruenbacher]

On Sat, Nov 22, 2025 at 1:07 PM Ming Lei <ming.lei at redhat.com> wrote:
> > static void bio_chain_endio(struct bio *bio)
> > {
> >         bio_endio(__bio_chain_endio(bio));
> > }
>
> bio_chain_endio() never gets called really, which can be thought as `flag`,

That's probably where this stops being relevant for the problem
reported by Stephen Zhang.

> and it should have been defined as `WARN_ON_ONCE(1);` for not confusing people.

But shouldn't bio_chain_endio() still be fixed to do the right thing
if called directly, or alternatively, just BUG()? Warning and still
doing the wrong thing seems a bit bizarre.

I also see direct bi_end_io calls in erofs_fileio_ki_complete(),
erofs_fscache_bio_endio(), and erofs_fscache_submit_bio(), so those
are at least confusing.

Thanks,
Andreas