[merged mm-hotfixes-stable] mm-vmscan-abort-proactive-reclaim-early-when-freezing-for-suspend.patch removed from -mm tree

The quilt patch titled
     Subject: mm: vmscan: abort proactive reclaim early when freezing for suspend
has been removed from the -mm tree.  Its filename was
     mm-vmscan-abort-proactive-reclaim-early-when-freezing-for-suspend.patch

This patch was dropped because it was merged into the mm-hotfixes-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Richard Chang <[email protected]>
Subject: mm: vmscan: abort proactive reclaim early when freezing for suspend
Date: Mon, 20 Jul 2026 04:41:03 +0000

Proactive reclaim (triggered via memory.reclaim or node sysfs) checks for
pending signals in its outer loop in user_proactive_reclaim().  However,
the inner reclaim loops—specifically scanning cgroups in shrink_many()
and evicting/aging folios in try_to_shrink_lruvec()—can run for a long
time before returning to the outer loop, especially on systems with many
cgroups or large memory sizes.

During system suspend, the PM freezer attempts to freeze all tasks by
sending fake signals (setting TIF_SIGPENDING).  Because the inner loops do
not check for pending signals, the proactive reclaim task can remain stuck
in kernel space for seconds, failing to enter the refrigerator in a timely
manner.  This leads to suspend failures due to freeze timeouts, a behavior
observed on Android devices.

This latency issue is specific to proactive reclaim because of its large,
user-defined reclaim targets (could be gigabytes).  Since commit
287d5fedb377 ("mm: memcg: use larger batches for proactive reclaim"),
proactive reclaim uses larger decaying batch sizes (starting at 1/4 of the
remaining target) to maintain throughput.  This keeps the task in the
inner reclaim loop for extended periods.  In contrast, reactive reclaim
(global/memcg) uses small targets (SWAP_CLUSTER_MAX, typically 32 pages),
allowing it to return to the outer loop and check signals frequently.

To fix this, add a signal_pending() check to should_abort_scan() for
proactive reclaim paths.  Since should_abort_scan() is called within the
inner scanning and eviction loops, this allows proactive reclaim to abort
early and return to the outer loop in user_proactive_reclaim().

Additionally, return -ERESTARTSYS instead of -EINTR in
user_proactive_reclaim().  When interrupted by system suspend, returning
-ERESTARTSYS allows the task to enter the refrigerator and automatically
restart the syscall upon resume, making the freezer transparent to
userspace.  For real signals, the signal layer will either restart the
syscall (if SA_RESTART is set) or return -EINTR to userspace.

This fix specifically targets Multi-Gen LRU (MGLRU).  Classic LRU's scan
targets per iteration are strictly bounded by get_scan_count(), which
ensures it returns to the outer loop more frequently.

The check in should_abort_scan() is limited to proactive reclaim
(sc->proactive) to avoid inadvertently affecting reactive reclaim paths,
and is wrapped in unlikely() as it is a slow path.

Link: https://lore.kernel.org/[email protected]
Fixes: 287d5fedb377 ("mm: memcg: use larger batches for proactive reclaim")
Fixes: 94968384dde1 ("memcg: introduce per-memcg reclaim interface")
Suggested-by: Michal Hocko <[email protected]>
Suggested-by: Oleg Nesterov <[email protected]>
Signed-off-by: Richard Chang <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Axel Rasmussen <[email protected]>
Cc: Barry Song <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Kairui Song <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Martin Liu <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Shakeel Butt <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: T.J. Mercier <[email protected]>
Cc: Wei Xu <[email protected]>
Cc: Yuanchu Xie <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---

 mm/vmscan.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

--- a/mm/vmscan.c~mm-vmscan-abort-proactive-reclaim-early-when-freezing-for-suspend
+++ a/mm/vmscan.c
@@ -4926,6 +4926,9 @@ static bool should_abort_scan(struct lru
 	int i;
 	enum zone_watermarks mark;
 
+	if (unlikely(sc->proactive && signal_pending(current)))
+		return true;
+
 	if (sc->nr_reclaimed >= max(sc->nr_to_reclaim, compact_gap(sc->order)))
 		return true;
 
@@ -7906,8 +7909,15 @@ int user_proactive_reclaim(char *buf,
 		unsigned long batch_size = (nr_to_reclaim - nr_reclaimed) / 4;
 		unsigned long reclaimed;
 
+		/*
+		 * Return -ERESTARTSYS to allow the freezer to interrupt the
+		 * task. The syscall will be transparently restarted upon
+		 * resume. For real signals, it either restarts the syscall
+		 * (if SA_RESTART is set) or is converted to -EINTR by the
+		 * signal layer.
+		 */
 		if (signal_pending(current))
-			return -EINTR;
+			return -ERESTARTSYS;
 
 		/*
 		 * This is the final attempt, drain percpu lru caches in the
_

Patches currently in -mm which might be from [email protected] are

mm-zsmalloc-fix-release-order-of-locks-in-zs_page_migrate.patch