+ memcg-nmi-safe-slab-stats-updates.patch added to mm-new branch

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

The patch titled
     Subject: memcg: nmi-safe slab stats updates
has been added to the -mm mm-new branch.  Its filename is
     memcg-nmi-safe-slab-stats-updates.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/memcg-nmi-safe-slab-stats-updates.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.

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------------------------------------------------------
From: Shakeel Butt <shakeel.butt@linux.dev>
Subject: memcg: nmi-safe slab stats updates
Date: Sun, 18 May 2025 23:31:41 -0700

The objcg based kmem [un]charging can be called in nmi context and it may
need to update NR_SLAB_[UN]RECLAIMABLE_B stats.  So, let's correctly
handle the updates of these stats in the nmi context.

Link: https://lkml.kernel.org/r/20250519063142.111219-5-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memcontrol.c |   36 +++++++++++++++++++++++++++++++++---
 1 file changed, 33 insertions(+), 3 deletions(-)

--- a/mm/memcontrol.c~memcg-nmi-safe-slab-stats-updates
+++ a/mm/memcontrol.c
@@ -2517,17 +2517,47 @@ static void commit_charge(struct folio *
 	folio->memcg_data = (unsigned long)memcg;
 }
 
+#ifdef CONFIG_MEMCG_NMI_SAFETY_REQUIRES_ATOMIC
+static inline void account_slab_nmi_safe(struct mem_cgroup *memcg,
+					 struct pglist_data *pgdat,
+					 enum node_stat_item idx, int nr)
+{
+	struct lruvec *lruvec;
+
+	if (likely(!in_nmi())) {
+		lruvec = mem_cgroup_lruvec(memcg, pgdat);
+		mod_memcg_lruvec_state(lruvec, idx, nr);
+	} else {
+		struct mem_cgroup_per_node *pn = memcg->nodeinfo[pgdat->node_id];
+
+		/* TODO: add to cgroup update tree once it is nmi-safe. */
+		if (idx == NR_SLAB_RECLAIMABLE_B)
+			atomic_add(nr, &pn->slab_reclaimable);
+		else
+			atomic_add(nr, &pn->slab_unreclaimable);
+	}
+}
+#else
+static inline void account_slab_nmi_safe(struct mem_cgroup *memcg,
+					 struct pglist_data *pgdat,
+					 enum node_stat_item idx, int nr)
+{
+	struct lruvec *lruvec;
+
+	lruvec = mem_cgroup_lruvec(memcg, pgdat);
+	mod_memcg_lruvec_state(lruvec, idx, nr);
+}
+#endif
+
 static inline void mod_objcg_mlstate(struct obj_cgroup *objcg,
 				       struct pglist_data *pgdat,
 				       enum node_stat_item idx, int nr)
 {
 	struct mem_cgroup *memcg;
-	struct lruvec *lruvec;
 
 	rcu_read_lock();
 	memcg = obj_cgroup_memcg(objcg);
-	lruvec = mem_cgroup_lruvec(memcg, pgdat);
-	mod_memcg_lruvec_state(lruvec, idx, nr);
+	account_slab_nmi_safe(memcg, pgdat, idx, nr);
 	rcu_read_unlock();
 }
 
_

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

memcg-memcg_rstat_updated-re-entrant-safe-against-irqs.patch
memcg-move-preempt-disable-to-callers-of-memcg_rstat_updated.patch
memcg-make-mod_memcg_state-re-entrant-safe-against-irqs.patch
memcg-make-count_memcg_events-re-entrant-safe-against-irqs.patch
memcg-make-__mod_memcg_lruvec_state-re-entrant-safe-against-irqs.patch
memcg-no-stock-lock-for-cpu-hot-unplug.patch
memcg-objcg-stock-trylock-without-irq-disabling.patch
memcg-disable-kmem-charging-in-nmi-for-unsupported-arch.patch
memcg-nmi-safe-memcg-stats-for-specific-archs.patch
memcg-add-nmi-safe-update-for-memcg_kmem.patch
memcg-nmi-safe-slab-stats-updates.patch
memcg-make-memcg_rstat_updated-nmi-safe.patch