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 na0EjtUY 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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 11/20/25 14:59, Zi Yan wrote: > folio_split_supported() used in try_folio_split_to_order() requires > folio->mapping to be non NULL, but current try_folio_split_to_order() does > not check it. Add the check to prevent NULL pointer dereference. > > There is no issue in the current code, since try_folio_split_to_order() is > only used in truncate_inode_partial_folio(), where folio->mapping is not > NULL. > Just reading through the description does not clarify one thing What is the race between just truncated and trying to split them - is there a common lock that needs to be held? Is it the subsequent call in truncate_inode_partial_folio() that causes the race? IOW, if a folio is not anonymous and does not have a mapping, how is it being passed to this function? > Signed-off-by: Zi Yan > --- > include/linux/huge_mm.h | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h > index 1d439de1ca2c..0d55354e3a34 100644 > --- a/include/linux/huge_mm.h > +++ b/include/linux/huge_mm.h > @@ -407,6 +407,13 @@ static inline int split_huge_page_to_order(struct page *page, unsigned int new_o > static inline int try_folio_split_to_order(struct folio *folio, > struct page *page, unsigned int new_order) > { > + /* > + * Folios that just got truncated cannot get split. Signal to the > + * caller that there was a race. > + */ > + if (!folio_test_anon(folio) && !folio->mapping) > + return -EBUSY; > + > if (!folio_split_supported(folio, new_order, SPLIT_TYPE_NON_UNIFORM, /* warns= */ false)) > return split_huge_page_to_order(&folio->page, new_order); > return folio_split(folio, new_order, page, NULL);