[PATCH] tmp

[David Hildenbrand (Arm)]

Signed-off-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>
---
 mm/gup.c | 66 ++++++++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 52 insertions(+), 14 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index 99902c15703b0..ec43071bd035a 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2259,6 +2259,56 @@ static struct folio *pofs_next_folio(struct folio *folio,
 	return pofs_get_folio(pofs, i);
 }

+enum lru_cache_drained {
+	LRU_CACHE_NOT_DRAINED,
+	LRU_CACHE_DRAINED,
+	LRU_CACHE_DRAINED_ALL,
+};
+
+static inline void folio_likely_lru_cached(const struct folio *folio)
+{
+	if (!folio_may_be_lru_cached(folio))
+		return false;
+	/*
+	 * Having the LRU flag clear either indicates LRU cache references
+	 * or LRU isolation.
+	 */
+	if (!folio_test_lru(folio))
+		return true;
+	/*
+	 * For mlocked folios, we don't have a real indication: we can only
+	 * take a guess based on the refcount.
+	 */
+	if (!folio_test_mlock(folio))
+		return false;
+	return folio_expected_ref_count(folio) == folio_ref_count(folio) = 1;
+}
+
+/**
+ * lru_cache_drain_for_folio() - progressively try draining the lru cache
+ * @folio: The folio.
+ * @drained: Status initialized to LRU_CACHE_NOT_DRAINED by the caller.
+ *
+ * TODO
+ */
+static void lru_cache_drain_for_folio(const struct folio *folio,
+		enum lru_cache_drained *drained)
+{
+	if (!folio_likely_lru_cached(folio))
+		return false;
+
+	/* Try local draining first, if not already done previously. */
+	if (*drained == LRU_CACHE_NOT_DRAINED) {
+		lru_add_drain();
+		*drained = LRU_CACHE_DRAINED;
+	}
+	/* Try draining all CPUs next if still not an LRU folio. */
+	if (folio_likely_lru_cached(folio) && *drained == LRU_CACHE_DRAINED) {
+		lru_add_drain_all();
+		*drained = LRU_CACHE_DRAINED_ALL;
+	}
+}
+
 /*
  * Returns the number of collected folios. Return value is always >= 0.
  */
@@ -2266,9 +2316,9 @@ static unsigned long collect_longterm_unpinnable_folios(
 		struct list_head *movable_folio_list,
 		struct pages_or_folios *pofs)
 {
+	enum lru_cache_drained drained = LRU_CACHE_NOT_DRAINED;
 	unsigned long collected = 0;
 	struct folio *folio;
-	int drained = 0;
 	long i = 0;

 	for (folio = pofs_get_folio(pofs, i); folio;
@@ -2287,19 +2337,7 @@ static unsigned long collect_longterm_unpinnable_folios(
 			continue;
 		}

-		if (drained == 0 && folio_may_be_lru_cached(folio) &&
-				folio_ref_count(folio) !=
-				folio_expected_ref_count(folio) + 1) {
-			lru_add_drain();
-			drained = 1;
-		}
-		if (drained == 1 && folio_may_be_lru_cached(folio) &&
-				folio_ref_count(folio) !=
-				folio_expected_ref_count(folio) + 1) {
-			lru_add_drain_all();
-			drained = 2;
-		}
-
+		lru_cache_drain_for_folio(folio, &drained);
 		if (!folio_isolate_lru(folio))
 			continue;

-- 
2.43.0


-- 
Cheers,

David