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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , "Matthew Wilcox (Oracle)" , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org 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 11 Oct 2025, at 20:41, Wei Yang wrote: > On Fri, Oct 10, 2025 at 01:39:05PM -0400, 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. >> */ > > It is better to update the document of try_folio_split() Sure. Will do. -- Best Regards, Yan, Zi