linux-kernel - [PATCH 07/12] mm: Make large folios depend on THP

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Date:   Sun, 16 Jan 2022 12:18:17 +0000
From:   "Matthew Wilcox (Oracle)" <willy@...radead.org>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>
Subject: [PATCH 07/12] mm: Make large folios depend on THP

Some parts of the VM still depend on THP to handle large folios
correctly.  Until those are fixed, prevent creating large folios
if THP are disabled.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
---
 include/linux/pagemap.h | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 877dabed0316..3e348e0a9e4e 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -192,9 +192,14 @@ static inline void mapping_set_large_folios(struct address_space *mapping)
 	__set_bit(AS_LARGE_FOLIO_SUPPORT, &mapping->flags);
 }
 
+/*
+ * Large folio support currently depends on THP.  These dependencies are
+ * being worked on but are not yet fixed.
+ */
 static inline bool mapping_large_folio_support(struct address_space *mapping)
 {
-	return test_bit(AS_LARGE_FOLIO_SUPPORT, &mapping->flags);
+	return IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
+		test_bit(AS_LARGE_FOLIO_SUPPORT, &mapping->flags);
 }
 
 static inline int filemap_nr_thps(struct address_space *mapping)
-- 
2.34.1