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

Matthew Wilcox
2024-09-18T13:35:08Z

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().

i wonder if xas_split_alloc() should call xas_reset() to prevent this
from ever being a problem again?