Looking at this in more detail, I wonder if we can turn that to
if (!folio_test_clear_lru(folio))
return;
folio_get(folio);
In all cases? The caller must hold a reference, so this should be fine.
Seems the caller madvise_free_pte_range(...), calling
folio_mark_lazyfree(...), doesn't hold a reference on folio.
If that would be the case and the folio could get freed concurrently,
the folio_get(folio) would be completely broken.
In madvise_free_pte_range() we hold the PTL, so the folio cannot get
freed concurrently.
folio_get() is only allowed when we are sure the folio cannot get freed
concurrently, because we know there is a reference that cannot go away.
--
Cheers,
David / dhildenb
