*/
static inline bool mapping_large_folio_support(struct address_space *mapping)
{
+ /* AS_LARGE_FOLIO_SUPPORT is only reasonable for pagecache folios */
+ VM_WARN_ONCE((unsigned long)mapping & PAGE_MAPPING_ANON,
+ "Anonymous mapping always supports large folio");
+
return IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
test_bit(AS_LARGE_FOLIO_SUPPORT, &mapping->flags);
}
if (new_order >= folio_order(folio))
return -EINVAL;
- /* Cannot split anonymous THP to order-1 */
- if (new_order == 1 && folio_test_anon(folio)) {
- VM_WARN_ONCE(1, "Cannot split to order-1 folio");
- return -EINVAL;
- }
-
- if (new_order) {
- /* Only swapping a whole PMD-mapped folio is supported */
- if (folio_test_swapcache(folio))
+ if (folio_test_anon(folio)) {
+ /* order-1 is not supported for anonymous THP. */
+ if (new_order == 1) {
+ VM_WARN_ONCE(1, "Cannot split to order-1 folio");
return -EINVAL;
+ }
+ } else if (new_order) {
/* Split shmem folio to non-zero order not supported */
if (shmem_mapping(folio->mapping)) {
VM_WARN_ONCE(1,
"Cannot split shmem folio to non-0 order");
return -EINVAL;
}
- /* No split if the file system does not support large folio */
- if (!mapping_large_folio_support(folio->mapping)) {
+ /*
+ * No split if the file system does not support large folio.
+ * Note that we might still have THPs in such mappings due to
+ * CONFIG_READ_ONLY_THP_FOR_FS. But in that case, the mapping
+ * does not actually support large folios properly.
+ */
+ if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) &&
+ !mapping_large_folio_support(folio->mapping)) {
VM_WARN_ONCE(1,
"Cannot split file folio to non-0 order");
return -EINVAL;
}
}
+ /* Only swapping a whole PMD-mapped folio is supported */
+ if (folio_test_swapcache(folio) && new_order)
+ return -EINVAL;
is_hzp = is_huge_zero_folio(folio);
if (is_hzp) {