From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 6ABB7376468; Tue, 25 Aug 2026 01:55:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787622944; cv=none; b=e1XHp/MNdeQHLqNafcZWYmazQoJTlpxJniAPlTG28oyCkF0x+2uBn95LQI+ksjy1Ob3Ew8yL/5Z0kIOQCfDFbD7izwHEJ0oJuVMqSplOpuFkqoHrcto8N9haF+PEF4/eSzOWjDJO2xeVYd0QGzx1Flos1e/R+cXsKz+ZkjsQsb0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787622944; c=relaxed/simple; bh=5DJozmw8IGgHrSGNtI2l5hgc/CQkM2dTevTpes7xAu0=; h=Date:To:From:Subject:Message-Id; b=OUstVI5OiXK8lmevW/F341zIfSINIn4GSjL00FBjlyrlLJEHkqf0IYbZ9Gpa+cnXrWeCzdE36auu9fSY3DBkkX9QtZ/IMn4EZSQZs14lQOSOVvTFOgVq6WPpE1D7VBaBHi19SYOYfdIypx8yPG7dgywGIbFhlFy5xUr6ocpggY0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=MjL2Fn4X; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="MjL2Fn4X" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 45C231F000E9; Tue, 25 Aug 2026 01:55:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1787622943; bh=J3DPObgIkgPswYENdgjVVLYjHlz0FG92HHr1vdKy/rU=; h=Date:To:From:Subject; b=MjL2Fn4XoACTZbWXKzQ9d2DPE0M5gjV1pw6jM6r3djnc54Jl3uuMImaa++g/p+2J7 XDbGPRR1ZW970RsJ08VTerXIU33kXZtHEjZ5Ms02C2atRNuK90ILvicf+FUro3qwBK xJeonrcp1u52oBhcZWe15GiBEspFbks3dSi90N4g= Date: Mon, 24 Aug 2026 18:55:42 -0700 To: mm-commits@vger.kernel.org,yuzhao@google.com,yuanchu@google.com,weixugc@google.com,suleiman@google.com,steven@liquorix.net,stable@vger.kernel.org,shakeel.butt@linux.dev,oleksandr@natalenko.name,mhocko@kernel.org,ljs@kernel.org,heftig@archlinux.org,hannes@cmpxchg.org,david@kernel.org,bgeffon@google.com,baolin.wang@linux.alibaba.com,baohua@kernel.org,axelrasmussen@google.com,kasong@tencent.com,akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-stable] mm-mglru-fix-and-remove-redundant-unevictable-folio-handling.patch removed from -mm tree Message-Id: <20260825015543.45C231F000E9@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: mm/mglru: fix and remove redundant unevictable folio handling has been removed from the -mm tree. Its filename was mm-mglru-fix-and-remove-redundant-unevictable-folio-handling.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Kairui Song Subject: mm/mglru: fix and remove redundant unevictable folio handling Date: Wed, 12 Aug 2026 20:22:39 +0800 sort_folio() has a shortcut for moving folios that are no longer evictable but are still sitting on a generation list. However, this shortcut is buggy. It does not follow the PG_lru usage convention, and it has a more serious issue. Unevictable folios are not threaded on lists[LRU_UNEVICTABLE], so that folio->lru can be reused to hold folio->mlock_count (see the comment in lruvec_init()). Hence lruvec_add_folio() skips the list_add() for them, and every other place that turns a folio unevictable initialises mlock_count explicitly: lru_add() sets it to 0, __mlock_folio() and __mlock_new_folio() set it to !!folio_test_mlocked(folio). sort_folio() sets nothing, and the lru_gen_del_folio() right above it may have already poisoned folio->lru via list_del(), so mlock_count ends up aliasing LIST_POISON2, which reads as 0x122, i.e. 290. The result is user visible. On munlock, __munlock_folio() decrements that bogus count, finds it still non-zero and bails out before clearing PG_mlocked, so the folio remains unevictable and the Mlocked accounting stays inflated until the folio is freed. The shortcut also touches the LRU flags in the wrong order. It calls lru_gen_del_folio() while PG_lru is still set, so a concurrent folio_test_clear_lru() (e.g. compaction, folio_isolate_lru()) can succeed on a folio that has already been taken off the generation list, which may lead to unexpected behavior. So fix it by isolating them as common folios and letting the generic shrink path cull them. This matches the classical LRU behavior, and there should be no visible effect on the generic eviction or isolation behavior. There is no performance concern either, such a folio goes through this once, and then it is off the generation lists for good. Link: https://lore.kernel.org/20260812-mglru-mlock-fix-v2-1-a3fec5853c08@tencent.com Fixes: ac35a4902374 ("mm: multi-gen LRU: minimal implementation") Signed-off-by: Kairui Song Reviewed-by: Barry Song Reviewed-by: Baolin Wang Cc: Axel Rasmussen Cc: Brian Geffon Cc: David Hildenbrand Cc: Jan Alexander Steffens (heftig) Cc: Johannes Weiner Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Oleksandr Natalenko Cc: Shakeel Butt Cc: Steven Barrett Cc: Suleiman Souhlal Cc: Wei Xu Cc: Yuanchu Xie Cc: Yu Zhao Cc: Signed-off-by: Andrew Morton --- mm/vmscan.c | 19 +++++-------------- 1 file changed, 5 insertions(+), 14 deletions(-) --- a/mm/vmscan.c~mm-mglru-fix-and-remove-redundant-unevictable-folio-handling +++ a/mm/vmscan.c @@ -4649,7 +4649,6 @@ void lru_gen_reparent_memcg(struct mem_c static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_control *sc, int tier_idx) { - bool success; int gen = folio_lru_gen(folio); int type = folio_is_file_lru(folio); int zone = folio_zonenum(folio); @@ -4661,15 +4660,9 @@ static bool sort_folio(struct lruvec *lr VM_WARN_ON_ONCE_FOLIO(gen >= MAX_NR_GENS, folio); - /* unevictable */ - if (!folio_evictable(folio)) { - success = lru_gen_del_folio(lruvec, folio, true); - VM_WARN_ON_ONCE_FOLIO(!success, folio); - folio_set_unevictable(folio); - lruvec_add_folio(lruvec, folio); - __count_vm_events(UNEVICTABLE_PGCULLED, delta); - return true; - } + /* unevictable: let it through and the generic path will cull it */ + if (!folio_evictable(folio)) + return false; /* promoted */ if (gen != lru_gen_from_seq(lrugen->min_seq[type])) { @@ -4922,11 +4915,9 @@ retry: list_for_each_entry_safe_reverse(folio, next, &list, lru) { DEFINE_MIN_SEQ(lruvec); - if (!folio_evictable(folio)) { - list_del(&folio->lru); - folio_putback_lru(folio); + /* move_folios_to_lru() culls unevictable folios via folio_putback_lru() */ + if (!folio_evictable(folio)) continue; - } /* retry folios that may have missed folio_rotate_reclaimable() */ if (!skip_retry && !folio_test_active(folio) && !folio_mapped(folio) && _ Patches currently in -mm which might be from kasong@tencent.com are