+ memcg-use-high_work-for-remote-charges.patch added to mm-new branch

+ memcg-use-high_work-for-remote-charges.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: memcg: use high_work for remote charges
has been added to the -mm mm-new branch.  Its filename is
     memcg-use-high_work-for-remote-charges.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/memcg-use-high_work-for-remote-charges.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: Shakeel Butt <shakeel.butt@linux.dev>
Subject: memcg: use high_work for remote charges
Date: Fri, 30 Oct 2026 13:54:15 -0700

Some charges go to a cgroup outside the current mm's cgroup and its
ancestors. The high handler uses current->mm, so it cannot handle these
overages. Filesystem notifications and remote page faults can take
this path.

Use mm_match_cgroup() before checking the high limits. If it does not
match, use high_work instead of recording task overage or doing
synchronous reclaim and throttling. Charges to the current mm's cgroup
or one of its ancestors keep their current handling. Tasks without an
mm also use the worker.

Like kernel threads, remote chargers skip memory.swap.high throttling
and its high-event reporting, and a fast allocator can outrun the worker.
The memory.max and memory.swap.max checks stay the same.

Link: https://lore.kernel.org/20261030205418.341214-5-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Suggested-by: Tejun Heo <tj@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Harry Yoo <harry@kernel.org>
---

 mm/memcontrol.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/mm/memcontrol.c~memcg-use-high_work-for-remote-charges
+++ a/mm/memcontrol.c
@@ -2714,7 +2714,8 @@ static void memcg_enforce_high(struct me
 			       gfp_t gfp_mask)
 {
 	bool allow_spinning = gfpflags_allow_spinning(gfp_mask);
-	bool use_worker = !in_task() || (current->flags & PF_KTHREAD);
+	bool use_worker = !in_task() || (current->flags & PF_KTHREAD) ||
+		!current->mm || !mm_match_cgroup(current->mm, memcg);
 
 	/*
 	 * If the hierarchy is above the normal consumption range, schedule
@@ -2737,6 +2738,7 @@ static void memcg_enforce_high(struct me
 		 * Don't make an unrelated interrupted task handle this charge.
 		 * Kernel threads may be working for other tasks, so let a worker
 		 * reclaim instead.
+		 * Remote charges need reclaim from their charged hierarchy.
 		 */
 		if (use_worker) {
 			if (mem_high) {
@@ -2765,7 +2767,7 @@ static void memcg_enforce_high(struct me
 		}
 	} while ((memcg = parent_mem_cgroup(memcg)));
 
-	/* Interrupts and kernel threads stop here. */
+	/* Interrupts, kernel threads, and remote chargers stop here. */
 	if (use_worker)
 		return;
 
_

Patches currently in -mm which might be from shakeel.butt@linux.dev are

memcg-move-memoryhigh-enforcement-out-of-try_charge_memcg.patch
memcg-force-charges-from-reclaim-before-trying-the-limits.patch
memcg-use-high_work-for-kernel-threads.patch
memcg-use-high_work-for-remote-charges.patch
memcg-simplify-high-limit-handling-after-a-charge.patch