mm/truncate: don't skip dirty page in folio_unmap_invalidate()

... otherwise this is a behavior change for the previous callers of
invalidate_complete_folio2(), e.g. the page invalidation routine.

Fixes: 4a9e231 ("mm/truncate: add folio_unmap_invalidate() helper")
Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Link: https://lore.kernel.org/r/20250218120209.88093-3-jefflexu@linux.alibaba.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: lostjeffle

mm/truncate.c

@@ -548,8 +548,6 @@ int folio_unmap_invalidate(struct address_space *mapping, struct folio *folio,
 
 	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
 
-	if (folio_test_dirty(folio))
-		return 0;
 	if (folio_mapped(folio))
 		unmap_mapping_folio(folio);
 	BUG_ON(folio_mapped(folio));