[PATCH 09/13] mm: drop uncached pages when writeback completes

[Jens Axboe]

If the folio is marked as uncached, drop pages when writeback completes.
Intended to be used with RWF_UNCACHED, to avoid needing sync writes for
uncached IO.

Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
 mm/filemap.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/mm/filemap.c b/mm/filemap.c
index 6f65025782bb..1e455ca872b5 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1634,6 +1634,18 @@ void folio_end_writeback(struct folio *folio)
 	if (__folio_end_writeback(folio))
 		folio_wake_bit(folio, PG_writeback);
 	acct_reclaim_writeback(folio);
+
+	/*
+	 * If folio is marked as uncached, then pages should be dropped when
+	 * writeback completes. Do that now.
+	 */
+	if (folio_test_uncached(folio)) {
+		folio_lock(folio);
+		if (invalidate_complete_folio2(folio->mapping, folio, 0))
+			folio_clear_uncached(folio);
+		folio_unlock(folio);
+
+	}
 	folio_put(folio);
 }
 EXPORT_SYMBOL(folio_end_writeback);
-- 
2.45.2