+ mm-mglru-avoid-reclaim-type-fall-back-when-isolation-makes-no-progress.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/mglru: avoid reclaim type fall back when isolation makes no progress
has been added to the -mm mm-new branch.  Its filename is
     mm-mglru-avoid-reclaim-type-fall-back-when-isolation-makes-no-progress.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mglru-avoid-reclaim-type-fall-back-when-isolation-makes-no-progress.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: "Barry Song (Xiaomi)" <baohua@kernel.org>
Subject: mm/mglru: avoid reclaim type fall back when isolation makes no progress
Date: Tue, 28 Apr 2026 02:06:57 +0800

While isolation makes no progress in scan_folios(), we quickly fall back
to the other type in isolate_folios().  This is incorrect, as the current
type may still have sufficient folios.  Falling back can undermine the
positive_ctrl_err() result from get_type_to_scan(), which is derived from
swappiness.

So just continue scanning this type for another round.

Worth noting if the cold generations are all reclaimed, scan will no
longer make any progress either, which may undermine the swappiness again.
This is not a new issue and hence better be fixed later [1].

Link: https://lore.kernel.org/linux-mm/CAGsJ_4zjdOYEtuO6gNjABm7NDxW0skzBFNRNee-k2D6VwsYEQA@mail.gmail.com/ [1]
Link: https://lore.kernel.org/20260428-mglru-reclaim-v7-6-02fabb92dc43@tencent.com
Signed-off-by: Barry Song (Xiaomi) <baohua@kernel.org>
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Kairui Song <kasong@tencent.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Chen Ridong <chenridong@huaweicloud.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: David Stevens <stevensd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Leno Hou <lenohou@gmail.com>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vernon Yang <vernon2gm@gmail.com>
Cc: Wei Xu <weixugc@google.com>
Cc: Yafang <laoar.shao@gmail.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/vmscan.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/mm/vmscan.c~mm-mglru-avoid-reclaim-type-fall-back-when-isolation-makes-no-progress
+++ a/mm/vmscan.c
@@ -4817,8 +4817,13 @@ static int isolate_folios(unsigned long
 			*isolate_scanned = scanned;
 			break;
 		}
-
-		type = !type;
+		/*
+		 * If scanned > 0 and isolated == 0, avoid falling back to the
+		 * other type, as this type remains sufficient. Falling back
+		 * too readily can disrupt the positive_ctrl_err() bias.
+		 */
+		if (!scanned)
+			type = !type;
 	}
 
 	return total_scanned;
_

Patches currently in -mm which might be from baohua@kernel.org are

mm-huge_memory-fix-outdated-comment-about-freeing-subpages-in-__folio_split.patch
mm-mglru-avoid-reclaim-type-fall-back-when-isolation-makes-no-progress.patch
mm-mglru-use-folio_mark_accessed-to-replace-folio_set_active-in-pf.patch