[PATCH] mm/huge_memory: drop beyond-EOF folios with the right number of refs.

[Zi Yan]

When an after-split folio is large and needs to be dropped due to EOF,
folio_put_refs(folio, folio_nr_pages(folio)) should be used to drop
all page cache refs. Otherwise, the folio will not be freed, causing
memory leak.

This leak would happen on a filesystem with blocksize > page_size and
a truncate is performed, where the blocksize makes folios split to
>0 order ones, causing truncated folios not being freed.

Fixes: c010d47f107f ("mm: thp: split huge page to any lower order pages")
Reported-by: Hugh Dickins <hughd@xxxxxxxxxx>
Closes: https://lore.kernel.org/all/fcbadb7f-dd3e-21df-f9a7-2853b53183c4@xxxxxxxxxx/
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
---
 mm/huge_memory.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 3d3ebdc002d5..373781b21e5c 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3304,7 +3304,7 @@ static void __split_huge_page(struct page *page, struct list_head *list,
 				folio_account_cleaned(tail,
 					inode_to_wb(folio->mapping->host));
 			__filemap_remove_folio(tail, NULL);
-			folio_put(tail);
+			folio_put_refs(tail, folio_nr_pages(tail));
 		} else if (!folio_test_anon(folio)) {
 			__xa_store(&folio->mapping->i_pages, tail->index,
 					tail, 0);
-- 
2.47.2