[PATCH mm-unstable v3 1/6] mm/mglru: clean up workingset

[Yu Zhao]

Move VM_BUG_ON_FOLIO() to cover both the default and MGLRU paths. Also
use a pair of rcu_read_lock() and rcu_read_unlock() within each path,
to improve readability.

This change should not have any side effects.

Signed-off-by: Yu Zhao <yuzhao@xxxxxxxxxx>
Tested-by: Kalesh Singh <kaleshsingh@xxxxxxxxxx>
---
 mm/workingset.c | 25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/mm/workingset.c b/mm/workingset.c
index a4705e196545..ad181d1b8cf1 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -428,17 +428,17 @@ bool workingset_test_recent(void *shadow, bool file, bool *workingset,
 	struct pglist_data *pgdat;
 	unsigned long eviction;
 
-	rcu_read_lock();
-
 	if (lru_gen_enabled()) {
-		bool recent = lru_gen_test_recent(shadow, file,
-				&eviction_lruvec, &eviction, workingset);
+		bool recent;
 
+		rcu_read_lock();
+		recent = lru_gen_test_recent(shadow, file, &eviction_lruvec,
+					     &eviction, workingset);
 		rcu_read_unlock();
 		return recent;
 	}
 
-
+	rcu_read_lock();
 	unpack_shadow(shadow, &memcgid, &pgdat, &eviction, workingset);
 	eviction <<= bucket_order;
 
@@ -459,14 +459,12 @@ bool workingset_test_recent(void *shadow, bool file, bool *workingset,
 	 * configurations instead.
 	 */
 	eviction_memcg = mem_cgroup_from_id(memcgid);
-	if (!mem_cgroup_disabled() &&
-	    (!eviction_memcg || !mem_cgroup_tryget(eviction_memcg))) {
-		rcu_read_unlock();
+	if (!mem_cgroup_tryget(eviction_memcg))
+		eviction_memcg = NULL;
+	rcu_read_unlock();
+
+	if (!mem_cgroup_disabled() && !eviction_memcg)
 		return false;
-	}
-
-	rcu_read_unlock();
-
 	/*
 	 * Flush stats (and potentially sleep) outside the RCU read section.
 	 *
@@ -544,6 +542,8 @@ void workingset_refault(struct folio *folio, void *shadow)
 	bool workingset;
 	long nr;
 
+	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
+
 	if (lru_gen_enabled()) {
 		lru_gen_refault(folio, shadow);
 		return;
@@ -558,7 +558,6 @@ void workingset_refault(struct folio *folio, void *shadow)
 	 * is actually experiencing the refault event. Make sure the folio is
 	 * locked to guarantee folio_memcg() stability throughout.
 	 */
-	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
 	nr = folio_nr_pages(folio);
 	memcg = folio_memcg(folio);
 	pgdat = folio_pgdat(folio);
-- 
2.47.0.338.g60cca15819-goog