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Howlett" , Nico Pache , Ryan Roberts , jane.chu@oracle.com, Dev Jain , Barry Song , "Matthew Wilcox (Oracle)" , linux-fsdevel@vger.kernel.org, david@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linmiaohe@huawei.com, syzbot+e6367ea2fdab6ed46056@syzkaller.appspotmail.com Subject: Re: [PATCH 1/2] mm/huge_memory: do not change split_huge_page*() target order silently. 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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 10 Oct 2025, at 22:25, Lance Yang wrote: > On 2025/10/11 01:39, Zi Yan wrote: >> Page cache folios from a file system that support large block size (LB= S) >> can have minimal folio order greater than 0, thus a high order folio m= ight >> not be able to be split down to order-0. Commit e220917fa507 ("mm: spl= it a >> folio in minimum folio order chunks") bumps the target order of >> split_huge_page*() to the minimum allowed order when splitting a LBS f= olio. >> This causes confusion for some split_huge_page*() callers like memory >> failure handling code, since they expect after-split folios all have >> order-0 when split succeeds but in really get min_order_for_split() or= der >> folios. >> >> Fix it by failing a split if the folio cannot be split to the target o= rder. >> >> Fixes: e220917fa507 ("mm: split a folio in minimum folio order chunks"= ) >> [The test poisons LBS folios, which cannot be split to order-0 folios,= and >> also tries to poison all memory. The non split LBS folios take more me= mory >> than the test anticipated, leading to OOM. The patch fixed the kernel >> warning and the test needs some change to avoid OOM.] >> Reported-by: syzbot+e6367ea2fdab6ed46056@syzkaller.appspotmail.com >> Closes: https://lore.kernel.org/all/68d2c943.a70a0220.1b52b.02b3.GAE@g= oogle.com/ >> Signed-off-by: Zi Yan >> --- >> include/linux/huge_mm.h | 28 +++++----------------------- >> mm/huge_memory.c | 9 +-------- >> mm/truncate.c | 6 ++++-- >> 3 files changed, 10 insertions(+), 33 deletions(-) >> >> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h >> index 8eec7a2a977b..9950cda1526a 100644 >> --- a/include/linux/huge_mm.h >> +++ b/include/linux/huge_mm.h >> @@ -394,34 +394,16 @@ static inline int split_huge_page_to_list_to_ord= er(struct page *page, struct lis >> * Return: 0: split is successful, otherwise split failed. >> */ >> static inline int try_folio_split(struct folio *folio, struct page *= page, >> - struct list_head *list) >> + struct list_head *list, unsigned int order) > > Seems like we need to add the order parameter to the stub for try_folio= _split() as well? > > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > > ... > > #else /* CONFIG_TRANSPARENT_HUGEPAGE */ > > static inline int try_folio_split(struct folio *folio, struct page *pag= e, > struct list_head *list) > { > VM_WARN_ON_ONCE_FOLIO(1, folio); > return -EINVAL; > } > > #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ Thanks. It is also reported by lkp robot. Will fix it. -- Best Regards, Yan, Zi