diff --git a/mm/shmem.c b/mm/shmem.c
index af49d6bf6382..11c3e6b1aa76 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1464,6 +1464,15 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, uoff_t lend,
 				VM_BUG_ON_FOLIO(folio_test_writeback(folio),
 						folio);
 
+				/*
+				 * A shared mapping can have dirty PTEs while
+				 * the folio is still clean. Mark the folio
+				 * dirty so a failed split cannot discard data
+				 * outside the range.
+				 */
+				if (!unfalloc && folio_test_large(folio))
+					folio_mark_dirty(folio);
+
 				if (!folio_test_large(folio)) {
 					truncate_inode_folio(mapping, folio);
 				} else if (truncate_inode_partial_folio(folio,