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 zEmADXgG 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 26 Aug 2025, at 19:16, Max Kellermann wrote: > It is not legal to have NULL pointers in a folio_batch. > > However, the Ceph code does exactly this, and a refactoring patch gone > wrong has exposed this to folios_put_refs(), see > https://lore.kernel.org/ceph-devel/aK4v548CId5GIKG1@swift.blarg.de/ > > I believe this should Oops instead of crashing due to NULL pointer > reference (guarded by is_huge_zero_folio(), which may silently hide > the bug). > > Signed-off-by: Max Kellermann > --- > mm/swap.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/swap.c b/mm/swap.c > index 3632dd061beb..07ccda00e7ee 100644 > --- a/mm/swap.c > +++ b/mm/swap.c > @@ -952,6 +952,7 @@ void folios_put_refs(struct folio_batch *folios, unsigned int *refs) > for (i = 0, j = 0; i < folios->nr; i++) { > struct folio *folio = folios->folios[i]; > unsigned int nr_refs = refs ? refs[i] : 1; > + BUG_ON(folio == NULL); > > if (is_huge_zero_folio(folio)) > continue; We are moving away from BUG_ON. It is better to use WARN_ON_ONCE and skip NULL values: if (WARN_ON_ONCE(!folio)) continue; -- Best Regards, Yan, Zi