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 530DA34BA52 for ; Sun, 21 Sep 2025 12:17:49 +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=1758457069; cv=none; b=QAmXf8tzC7yfo8Zk2X5mPo4HtiMG1n8CakOeR3qCKpnpr6NXsILNKgrz0yrfUwYEx5UjdKuVKVyodGmTt1m/NNz1aLCdKOiinxtrP+O5HmJ9v/Q542uz6nU5eGNzFaq3KFCAxFqaVZzjMBE3Mfh5fCMddRl1Eu8btiPj8kZNAM4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758457069; c=relaxed/simple; bh=LFO+OFkAMv/eCVOI/KCc/aY2Zl3xgv6u/LNyvHDC/PM=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=gdR4S7ajXiB7xtrKTSo9HgQhItdMRDunWqEsRksnb76DyL+gfM47JsbBO0PZuaaTUJmOXkRN2p7JDpuEQ5bikdFB3WBzeCGSE29EWY/jZKPwttLeZjPyZ9uYYc+sIdcEGxtItEGPkHfzTD6kbd2Aw1Cbr6IEkUwiw8OfCrn23Uo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=b+Fu3KHK; 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="b+Fu3KHK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DDABBC4CEE7; Sun, 21 Sep 2025 12:17:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1758457069; bh=LFO+OFkAMv/eCVOI/KCc/aY2Zl3xgv6u/LNyvHDC/PM=; h=Subject:To:Cc:From:Date:From; b=b+Fu3KHKsp5BamC4qpesOhoPld4ZNzoRUOA+nLT9f1vPiO6gTPXCaerMhT+rKHd/Q C98wh2ZvLkj0NkTfDnT78UQ9diNg99tayGszXHncmnccOGk3+QvPzPwJSXmuz+iia+ yQa+sJUY1cGAxYJmxHwCH6g3J/9/4eFJt0JhKZ8Q= Subject: FAILED: patch "[PATCH] mm: folio_may_be_lru_cached() unless folio_test_large()" failed to apply to 6.6-stable tree To: hughd@google.com,akpm@linux-foundation.org,aneesh.kumar@kernel.org,axelrasmussen@google.com,chrisl@kernel.org,david@redhat.com,hannes@cmpxchg.org,hch@infradead.org,jgg@ziepe.ca,jhubbard@nvidia.com,keirf@google.com,koct9i@gmail.com,lizhe.67@bytedance.com,peterx@redhat.com,riel@surriel.com,shivankg@amd.com,stable@vger.kernel.org,vbabka@suse.cz,weixugc@google.com,will@kernel.org,willy@infradead.org,yangge1116@126.com,yuanchu@google.com,yuzhao@google.com Cc: From: Date: Sun, 21 Sep 2025 14:17:43 +0200 Message-ID: <2025092143-defrost-backboned-d1ea@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x 2da6de30e60dd9bb14600eff1cc99df2fa2ddae3 # git commit -s git send-email --to '' --in-reply-to '2025092143-defrost-backboned-d1ea@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 2da6de30e60dd9bb14600eff1cc99df2fa2ddae3 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Mon, 8 Sep 2025 15:23:15 -0700 Subject: [PATCH] mm: folio_may_be_lru_cached() unless folio_test_large() 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 diff --git a/include/linux/swap.h b/include/linux/swap.h index 2fe6ed2cc3fd..7012a0f758d8 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -385,6 +385,16 @@ void folio_add_lru_vma(struct folio *, struct vm_area_struct *); 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) diff --git a/mm/gup.c b/mm/gup.c index b47066a54f52..0bc4d140fc07 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -2307,13 +2307,13 @@ static unsigned long collect_longterm_unpinnable_folios( 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(); diff --git a/mm/mlock.c b/mm/mlock.c index a1d93ad33c6d..bb0776f5ef7c 100644 --- 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); } diff --git a/mm/swap.c b/mm/swap.c index 6ae2d5680574..b74ebe865dd9 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -192,7 +192,7 @@ static void __folio_batch_add_and_move(struct folio_batch __percpu *fbatch, 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)