[PATCH v4 01/13] powerpc/mm: Add DEBUG_VM WARN for pmd_clear

[Aneesh Kumar K.V]

With the hash page table, the kernel should not use pmd_clear for clearing
huge pte entries. Add a DEBUG_VM WARN to catch the wrong usage.

Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
---
 arch/powerpc/include/asm/book3s/64/pgtable.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h 
b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 6de56c3b33c4..079211968987 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -868,6 +868,13 @@ static inline bool pte_ci(pte_t pte)
 
 static inline void pmd_clear(pmd_t *pmdp)
 {
+       if (IS_ENABLED(CONFIG_DEBUG_VM) && !radix_enabled()) {
+               /*
+                * Don't use this if we can possibly have a hash page table
+                * entry mapping this.
+                */
+               WARN_ON((pmd_val(*pmdp) & (H_PAGE_HASHPTE | _PAGE_PTE)) == 
(H_PAGE_HASHPTE | _PAGE_PTE));
+       }
        *pmdp = __pmd(0);
 }
 
@@ -916,6 +923,13 @@ static inline int pmd_bad(pmd_t pmd)
 
 static inline void pud_clear(pud_t *pudp)
 {
+       if (IS_ENABLED(CONFIG_DEBUG_VM) && !radix_enabled()) {
+               /*
+                * Don't use this if we can possibly have a hash page table
+                * entry mapping this.
+                */
+               WARN_ON((pud_val(*pudp) & (H_PAGE_HASHPTE | _PAGE_PTE)) == 
(H_PAGE_HASHPTE | _PAGE_PTE));
+       }
        *pudp = __pud(0);
 }
 
-- 
2.26.2