DEBIAN-CVE-2026-31589

In the Linux kernel, the following vulnerability has been resolved:  mm: call ->freefolio() directly in foliounmapinvalidate()  We can only call filemapfreefolio() if we have a reference to (or hold a lock on) the mapping.  Otherwise, we've already removed the folio from the mapping so it no longer pins the mapping and the mapping can be removed, causing a use-after-free when accessing mapping->aops.  Follow the same pattern as _removemapping() and load the freefolio function pointer before dropping the lock on the mapping.  That lets us make filemapfree_folio() static as this was the only caller outside filemap.c.