From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DAD722F0C5C; Mon, 22 Sep 2025 19:43:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758570215; cv=none; b=UNgsu+Ku6sSO/nxwXUfKS+mvZ5q0W76glkiTylnSdIA1d+lDtDPrtzFcAv0HFlsrU32iHKKuCHhgkMNRZnGNEK2xgcT9svrTRQsCeZSIuEt0nRXuA20Nh7Wu2mHf8FlmxHSUK4R5pckKNNAhBSe/uYiIbyT8TNRlkgurpF3sUjs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758570215; c=relaxed/simple; bh=sFo2O+TdVdk5QN1nPGNL8qMzh2Gv498PvX9e8zvb8x4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ZMAsu7HofLUzLr7VB2g6x0Va5tl30fCYdp2gTSrbWR8q4lI9ipwKd0MzaJrh+xSnHbgO5wz1IO4sRrlp7afNcM875+o/HTh3hI2I9khEwsU2KVp2vcsh6SRCLrd/C/fBlnRp3NwcVn7mqzyDSy2K7WiMtSr3jhe8Stalf+Xn6lg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=B3i7T6qt; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="B3i7T6qt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4B996C4CEF0; Mon, 22 Sep 2025 19:43:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1758570215; bh=sFo2O+TdVdk5QN1nPGNL8qMzh2Gv498PvX9e8zvb8x4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=B3i7T6qt0C6bxuwQv2W45t5f/fVw1RpRCDObLCBCrksl4PVoBaDulcKuUfEeYWla7 DiytLmMPYJ7zoD3jQP+yet/sJoSX4TbxprAxjoYbPIWb/BzcFdKyDYkiP8X4l0QNUJ wiJB/kuUrXbXzeavzvlV9KjuswGlobwW5bVfhbQI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Hugh Dickins , David Hildenbrand , "Aneesh Kumar K.V" , Axel Rasmussen , Chris Li , Christoph Hellwig , Jason Gunthorpe , Johannes Weiner , John Hubbard , Keir Fraser , Konstantin Khlebnikov , Li Zhe , "Matthew Wilcox (Oracle)" , Peter Xu , Rik van Riel , Shivank Garg , Vlastimil Babka , Wei Xu , Will Deacon , yangge , Yuanchu Xie , Yu Zhao , Andrew Morton Subject: [PATCH 6.16 063/149] mm: folio_may_be_lru_cached() unless folio_test_large() Date: Mon, 22 Sep 2025 21:29:23 +0200 Message-ID: <20250922192414.472294077@linuxfoundation.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20250922192412.885919229@linuxfoundation.org> References: <20250922192412.885919229@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Hugh Dickins commit 2da6de30e60dd9bb14600eff1cc99df2fa2ddae3 upstream. mm/swap.c and mm/mlock.c agree to drain any per-CPU batch as soon as a large folio is added: so collect_longterm_unpinnable_folios() just wastes effort when calling lru_add_drain[_all]() on a large folio. But although there is good reason not to batch up PMD-sized folios, we might well benefit from batching a small number of low-order mTHPs (though unclear how that "small number" limitation will be implemented). So ask if folio_may_be_lru_cached() rather than !folio_test_large(), to insulate those particular checks from future change. Name preferred to "folio_is_batchable" because large folios can well be put on a batch: it's just the per-CPU LRU caches, drained much later, which need care. Marked for stable, to counter the increase in lru_add_drain_all()s from "mm/gup: check ref_count instead of lru before migration". Link: https://lkml.kernel.org/r/57d2eaf8-3607-f318-e0c5-be02dce61ad0@google.com Fixes: 9a4e9f3b2d73 ("mm: update get_user_pages_longterm to migrate pages allocated from CMA region") Signed-off-by: Hugh Dickins Suggested-by: David Hildenbrand Acked-by: David Hildenbrand Cc: "Aneesh Kumar K.V" Cc: Axel Rasmussen Cc: Chris Li Cc: Christoph Hellwig Cc: Jason Gunthorpe Cc: Johannes Weiner Cc: John Hubbard Cc: Keir Fraser Cc: Konstantin Khlebnikov Cc: Li Zhe Cc: Matthew Wilcox (Oracle) Cc: Peter Xu Cc: Rik van Riel Cc: Shivank Garg Cc: Vlastimil Babka Cc: Wei Xu Cc: Will Deacon Cc: yangge Cc: Yuanchu Xie Cc: Yu Zhao Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- include/linux/swap.h | 10 ++++++++++ mm/gup.c | 4 ++-- mm/mlock.c | 6 +++--- mm/swap.c | 2 +- 4 files changed, 16 insertions(+), 6 deletions(-) --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -384,6 +384,16 @@ void folio_add_lru_vma(struct folio *, s void mark_page_accessed(struct page *); void folio_mark_accessed(struct folio *); +static inline bool folio_may_be_lru_cached(struct folio *folio) +{ + /* + * Holding PMD-sized folios in per-CPU LRU cache unbalances accounting. + * Holding small numbers of low-order mTHP folios in per-CPU LRU cache + * will be sensible, but nobody has implemented and tested that yet. + */ + return !folio_test_large(folio); +} + extern atomic_t lru_disable_count; static inline bool lru_cache_disabled(void) --- a/mm/gup.c +++ b/mm/gup.c @@ -2353,13 +2353,13 @@ static unsigned long collect_longterm_un continue; } - if (drained == 0 && + if (drained == 0 && folio_may_be_lru_cached(folio) && folio_ref_count(folio) != folio_expected_ref_count(folio) + 1) { lru_add_drain(); drained = 1; } - if (drained == 1 && + if (drained == 1 && folio_may_be_lru_cached(folio) && folio_ref_count(folio) != folio_expected_ref_count(folio) + 1) { lru_add_drain_all(); --- a/mm/mlock.c +++ b/mm/mlock.c @@ -255,7 +255,7 @@ void mlock_folio(struct folio *folio) folio_get(folio); if (!folio_batch_add(fbatch, mlock_lru(folio)) || - folio_test_large(folio) || lru_cache_disabled()) + !folio_may_be_lru_cached(folio) || lru_cache_disabled()) mlock_folio_batch(fbatch); local_unlock(&mlock_fbatch.lock); } @@ -278,7 +278,7 @@ void mlock_new_folio(struct folio *folio folio_get(folio); if (!folio_batch_add(fbatch, mlock_new(folio)) || - folio_test_large(folio) || lru_cache_disabled()) + !folio_may_be_lru_cached(folio) || lru_cache_disabled()) mlock_folio_batch(fbatch); local_unlock(&mlock_fbatch.lock); } @@ -299,7 +299,7 @@ void munlock_folio(struct folio *folio) */ folio_get(folio); if (!folio_batch_add(fbatch, folio) || - folio_test_large(folio) || lru_cache_disabled()) + !folio_may_be_lru_cached(folio) || lru_cache_disabled()) mlock_folio_batch(fbatch); local_unlock(&mlock_fbatch.lock); } --- a/mm/swap.c +++ b/mm/swap.c @@ -192,7 +192,7 @@ static void __folio_batch_add_and_move(s local_lock(&cpu_fbatches.lock); if (!folio_batch_add(this_cpu_ptr(fbatch), folio) || - folio_test_large(folio) || lru_cache_disabled()) + !folio_may_be_lru_cached(folio) || lru_cache_disabled()) folio_batch_move_lru(this_cpu_ptr(fbatch), move_fn); if (disable_irq)