mm/huge_memory: fix folio split check for anon folios in swapcache

Both uniform and non uniform split check missed the check to prevent
splitting anon folios in swapcache to non-zero order.

Splitting anon folios in swapcache to non-zero order can cause data
corruption since swapcache only support PMD order and order-0 entries. 
This can happen when one use split_huge_pages under debugfs to split
anon folios in swapcache.

In-tree callers do not perform such an illegal operation.  Only debugfs
interface could trigger it.  I will put adding a test case on my TODO
list.

Fix the check.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: 58729c04cf10 ("mm/huge_memory: add buddy allocator like (non-uniform) folio_split()")
Signed-off-by: Zi Yan <[email protected]>
Reported-by: "David Hildenbrand (Red Hat)" <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]/
Acked-by: David Hildenbrand (Red Hat) <[email protected]>
Cc: Baolin Wang <[email protected]>
Cc: Barry Song <[email protected]>
Cc: Dev Jain <[email protected]>
Cc: Lance Yang <[email protected]>
Cc: Liam Howlett <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Nico Pache <[email protected]>
Cc: Ryan Roberts <[email protected]>
Cc: Wei Yang <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions