huge_memory: return -EINVAL in folio split functions when THP is disabled

split_huge_page_to_list_[to_order](), split_huge_page() and
try_folio_split() return 0 on success and error codes on failure.

When THP is disabled, these functions return 0 indicating success even
though an error code should be returned as it is not possible to split a
folio when THP is disabled.

Make all these functions return -EINVAL to indicate failure instead of 0.
As large folios depend on CONFIG_THP, issue warning as this function
should not be called without a large folio.

Link: https://lkml.kernel.org/r/20250905150012.93714-1-kernel@pankajraghav.com
Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202509051753.riCeG7LC-lkp@intel.com/
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Zi Yan <ziy@nvidia.com>
Acked-by: Kiryl Shutsemau <kas@kernel.org>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Barry Song <baohua@kernel.org>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 29ef70022da1f7dd2c46dcf809794fa83c5347cb..f327d62fc9852d3cf717e633ed9b39deecfa0f20 100644 (file)
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -588,22 +588,26 @@ static inline int
 split_huge_page_to_list_to_order(struct page *page, struct list_head *list,
                unsigned int new_order)
 {
-       return 0;
+       VM_WARN_ON_ONCE_PAGE(1, page);
+       return -EINVAL;
 }
 static inline int split_huge_page(struct page *page)
 {
-       return 0;
+       VM_WARN_ON_ONCE_PAGE(1, page);
+       return -EINVAL;
 }
 
 static inline int split_folio_to_list(struct folio *folio, struct list_head *list)
 {
-       return 0;
+       VM_WARN_ON_ONCE_FOLIO(1, folio);
+       return -EINVAL;
 }
 
 static inline int try_folio_split(struct folio *folio, struct page *page,
                struct list_head *list)
 {
-       return 0;
+       VM_WARN_ON_ONCE_FOLIO(1, folio);
+       return -EINVAL;
 }
 
 static inline void deferred_split_folio(struct folio *folio, bool partially_mapped) {}