Re: Known and unfixed active data loss bug in MM + XFS with large folios since Dec 2021 (any kernel from 6.1 upwards)

Dave Chinner
2024-09-19T01:43:18Z

On Wed, Sep 18, 2024 at 02:34:57PM +0100, Matthew Wilcox wrote:
> On Wed, Sep 18, 2024 at 11:28:52AM +0200, Chris Mason wrote:
> > I think the bug was in __filemap_add_folio()'s usage of xarray_split_alloc()
> > and the tree changing before taking the lock. It's just a guess, but that
> > was always my biggest suspect.
>
> Oh god, that's it.
>
> there should have been an xas_reset() after calling xas_split_alloc().
>
> and 6758c1128ceb calls xas_reset() after calling xas_split_alloc().

Should we be asking for 6758c1128ceb to be backported to all
stable kernels then?

-Dave.
--
Dave Chinner
david@fromorbit.com