Re: [RFC PATCH] fs/buffer: Handle non folio buffer case for drop_buffer()

Matthew Wilcox
2025-04-25T20:01:11Z

On Sat, Apr 26, 2025 at 12:52:42AM +0800, I Hsin Cheng wrote:
> > Can you print more about the folio where this happened? In particular it
> > would be interesting what's in folio->flags, folio->mapping->flags and
> > folio->mapping->aops (resolved to a symbol). Because either the mapping has
> > AS_RELEASE_ALWAYS set but then we should have ->releasepage handler, or
> > have PG_Private bit set without buffers attached to a page but then again
> > either ->releasepage should be set or there's some bug in fs/buffer.c which
> > can set PG_Private without attaching buffers (I don't see where that could
> > be).
> >
>
> Hmm so I suppose when there're buffers attached, the PG_Private bit
> should always be set in folio->flags or folio->mapping->flags or
> folio->mapping->aops ?

See folio_attach_private(). I am trying to get rid of PG_private, but
we're not quite there yet. The other information may help track down
what is going on.