[RFC PATCH 5/7] memcg: make __mod_memcg_lruvec_state re-entrant safe against irqs

[Shakeel Butt <shakeel.butt@linux.dev>]

Let's make __mod_memcg_lruvec_state re-entrant safe and name it
mod_memcg_lruvec_state(). The only thing needed is to convert the usage
of __this_cpu_add() to this_cpu_add(). There are two callers of
mod_memcg_lruvec_state() and one of them i.e. __mod_objcg_mlstate() will
be re-entrant safe as well, so, rename it mod_objcg_mlstate(). The last
caller __mod_lruvec_state() still calls __mod_node_page_state() which is
not re-entrant safe yet, so keep it as is.

Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
---
 mm/memcontrol.c | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 9e7dc90cc460..adf2f1922118 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -731,7 +731,7 @@ unsigned long memcg_page_state_local(struct mem_cgroup *memcg, int idx)
 }
 #endif
 
-static void __mod_memcg_lruvec_state(struct lruvec *lruvec,
+static void mod_memcg_lruvec_state(struct lruvec *lruvec,
 				     enum node_stat_item idx,
 				     int val)
 {
@@ -743,16 +743,20 @@ static void __mod_memcg_lruvec_state(struct lruvec *lruvec,
 	if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, idx))
 		return;
 
+	if (WARN_ONCE(in_nmi(), "%s: called in nmi context for stat item %d\n",
+		      __func__, idx))
+		return;
+
 	pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec);
 	memcg = pn->memcg;
 
 	cpu = get_cpu();
 
 	/* Update memcg */
-	__this_cpu_add(memcg->vmstats_percpu->state[i], val);
+	this_cpu_add(memcg->vmstats_percpu->state[i], val);
 
 	/* Update lruvec */
-	__this_cpu_add(pn->lruvec_stats_percpu->state[i], val);
+	this_cpu_add(pn->lruvec_stats_percpu->state[i], val);
 
 	val = memcg_state_val_in_pages(idx, val);
 	memcg_rstat_updated(memcg, val, cpu);
@@ -779,7 +783,7 @@ void __mod_lruvec_state(struct lruvec *lruvec, enum node_stat_item idx,
 
 	/* Update memcg and lruvec */
 	if (!mem_cgroup_disabled())
-		__mod_memcg_lruvec_state(lruvec, idx, val);
+		mod_memcg_lruvec_state(lruvec, idx, val);
 }
 
 void __lruvec_stat_mod_folio(struct folio *folio, enum node_stat_item idx,
@@ -2559,7 +2563,7 @@ static void commit_charge(struct folio *folio, struct mem_cgroup *memcg)
 	folio->memcg_data = (unsigned long)memcg;
 }
 
-static inline void __mod_objcg_mlstate(struct obj_cgroup *objcg,
+static inline void mod_objcg_mlstate(struct obj_cgroup *objcg,
 				       struct pglist_data *pgdat,
 				       enum node_stat_item idx, int nr)
 {
@@ -2570,7 +2574,7 @@ static inline void __mod_objcg_mlstate(struct obj_cgroup *objcg,
 	memcg = obj_cgroup_memcg(objcg);
 	if (likely(!in_nmi())) {
 		lruvec = mem_cgroup_lruvec(memcg, pgdat);
-		__mod_memcg_lruvec_state(lruvec, idx, nr);
+		mod_memcg_lruvec_state(lruvec, idx, nr);
 	} else {
 		struct mem_cgroup_per_node *pn = memcg->nodeinfo[pgdat->node_id];
 
@@ -2901,12 +2905,12 @@ static void __account_obj_stock(struct obj_cgroup *objcg,
 		struct pglist_data *oldpg = stock->cached_pgdat;
 
 		if (stock->nr_slab_reclaimable_b) {
-			__mod_objcg_mlstate(objcg, oldpg, NR_SLAB_RECLAIMABLE_B,
+			mod_objcg_mlstate(objcg, oldpg, NR_SLAB_RECLAIMABLE_B,
 					  stock->nr_slab_reclaimable_b);
 			stock->nr_slab_reclaimable_b = 0;
 		}
 		if (stock->nr_slab_unreclaimable_b) {
-			__mod_objcg_mlstate(objcg, oldpg, NR_SLAB_UNRECLAIMABLE_B,
+			mod_objcg_mlstate(objcg, oldpg, NR_SLAB_UNRECLAIMABLE_B,
 					  stock->nr_slab_unreclaimable_b);
 			stock->nr_slab_unreclaimable_b = 0;
 		}
@@ -2932,7 +2936,7 @@ static void __account_obj_stock(struct obj_cgroup *objcg,
 		}
 	}
 	if (nr)
-		__mod_objcg_mlstate(objcg, pgdat, idx, nr);
+		mod_objcg_mlstate(objcg, pgdat, idx, nr);
 }
 
 static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes,
@@ -3004,13 +3008,13 @@ static void drain_obj_stock(struct obj_stock_pcp *stock)
 	 */
 	if (stock->nr_slab_reclaimable_b || stock->nr_slab_unreclaimable_b) {
 		if (stock->nr_slab_reclaimable_b) {
-			__mod_objcg_mlstate(old, stock->cached_pgdat,
+			mod_objcg_mlstate(old, stock->cached_pgdat,
 					  NR_SLAB_RECLAIMABLE_B,
 					  stock->nr_slab_reclaimable_b);
 			stock->nr_slab_reclaimable_b = 0;
 		}
 		if (stock->nr_slab_unreclaimable_b) {
-			__mod_objcg_mlstate(old, stock->cached_pgdat,
+			mod_objcg_mlstate(old, stock->cached_pgdat,
 					  NR_SLAB_UNRECLAIMABLE_B,
 					  stock->nr_slab_unreclaimable_b);
 			stock->nr_slab_unreclaimable_b = 0;
@@ -3050,7 +3054,7 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes,
 
 	if (unlikely(in_nmi())) {
 		if (pgdat)
-			__mod_objcg_mlstate(objcg, pgdat, idx, nr_bytes);
+			mod_objcg_mlstate(objcg, pgdat, idx, nr_bytes);
 		nr_pages = nr_bytes >> PAGE_SHIFT;
 		nr_bytes = nr_bytes & (PAGE_SIZE - 1);
 		atomic_add(nr_bytes, &objcg->nr_charged_bytes);
-- 
2.47.1