[RFC v2 13/21] mm: huge_mm: Make sure all split_huge_pmd calls are checked

[Usama Arif]

Mark __split_huge_pmd(), split_huge_pmd() and split_huge_pmd_address()
with __must_check so the compiler warns if any caller ignores the return
value. Not checking return value and operating on the basis that the pmd
is split could result in a kernel bug. The possibility of an order-0
allocation failing for page table allocation is very low, but it should
be handled correctly.

Signed-off-by: Usama Arif <usama.arif at linux.dev>
---
 include/linux/huge_mm.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 207bf7cd95c78..b4c2fd4252097 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -419,7 +419,7 @@ void deferred_split_folio(struct folio *folio, bool partially_mapped);
 void reparent_deferred_split_queue(struct mem_cgroup *memcg);
 #endif
 
-int __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
+int __must_check __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 		unsigned long address, bool freeze);
 
 /**
@@ -448,7 +448,7 @@ static inline bool pmd_is_huge(pmd_t pmd)
 	return false;
 }
 
-static inline int split_huge_pmd(struct vm_area_struct *vma,
+static inline int __must_check split_huge_pmd(struct vm_area_struct *vma,
 					     pmd_t *pmd, unsigned long address)
 {
 	if (pmd_is_huge(*pmd))
@@ -456,7 +456,7 @@ static inline int split_huge_pmd(struct vm_area_struct *vma,
 	return 0;
 }
 
-int split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
+int __must_check split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
 		bool freeze);
 
 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
-- 
2.47.3