From: "Kirill A. Shutemov" <redacted>

replace_page_cache_page() is only used by FUSE. It's unlikely that we
will support THP in FUSE page cache any soon.

Let's pospone implemetation of THP handling in replace_page_cache_page()
until any will use it. -EINVAL and WARN_ONCE() for now.

Signed-off-by: Kirill A. Shutemov <redacted>
---
 mm/filemap.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/filemap.c b/mm/filemap.c
index b75bdf5..28f4927 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c

@@ -418,6 +418,10 @@ int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
 {
 	int error;
 
+	if (WARN_ONCE(PageTransHuge(old) || PageTransHuge(new),
+		     "unexpected transhuge page\n"))
+		return -EINVAL;
+
 	VM_BUG_ON(!PageLocked(old));
 	VM_BUG_ON(!PageLocked(new));
 	VM_BUG_ON(new->mapping);

-- 
1.8.3.2

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