Subject: [RFC PATCH V1 29/33] powerpc/mm: Hash linux abstraction for THP

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Tue, 12 Jan 2016 12:46:04 +0530

Signed-off-by: Aneesh Kumar K.V <[email-masked]>
---
 arch/powerpc/include/asm/book3s/64/hash-64k.h |  42 ++++---
 arch/powerpc/include/asm/book3s/64/hash.h     |  14 +++
 arch/powerpc/include/asm/book3s/64/pgtable.h  | 154 +++++++++++++++++++++-----
 arch/powerpc/mm/pgtable-hash64.c              |  58 +++++-----
 4 files changed, 198 insertions(+), 70 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/hash-64k.h b/arch/powerpc/include/asm/book3s/64/hash-64k.h
index 8008c9a89416..e697fc528c0a 100644
--- a/arch/powerpc/include/asm/book3s/64/hash-64k.h
+++ b/arch/powerpc/include/asm/book3s/64/hash-64k.h
@@ -190,11 +190,19 @@ static inline int hugepd_ok(hugepd_t hpd)
 #endif /* CONFIG_HUGETLB_PAGE */
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-extern unsigned long pmd_hugepage_update(struct mm_struct *mm,
-					 unsigned long addr,
-					 pmd_t *pmdp,
-					 unsigned long clr,
-					 unsigned long set);
+
+extern pmd_t pfn_hlpmd(unsigned long pfn, pgprot_t pgprot);
+extern pmd_t mk_hlpmd(struct page *page, pgprot_t pgprot);
+extern pmd_t hlpmd_modify(pmd_t pmd, pgprot_t newprot);
+extern int hl_has_transparent_hugepage(void);
+extern void set_hlpmd_at(struct mm_struct *mm, unsigned long addr,
+			 pmd_t *pmdp, pmd_t pmd);
+
+extern unsigned long hlpmd_hugepage_update(struct mm_struct *mm,
+					   unsigned long addr,
+					   pmd_t *pmdp,
+					   unsigned long clr,
+					   unsigned long set);
 static inline char *get_hpte_slot_array(pmd_t *pmdp)
 {
 	/*
@@ -253,51 +261,55 @@ static inline void mark_hpte_slot_valid(unsigned char *hpte_slot_array,
  * that for explicit huge pages.
  *
  */
-static inline int pmd_trans_huge(pmd_t pmd)
+static inline int hlpmd_trans_huge(pmd_t pmd)
 {
 	return !!((pmd_val(pmd) & (H_PAGE_PTE | H_PAGE_THP_HUGE)) ==
 		  (H_PAGE_PTE | H_PAGE_THP_HUGE));
 }
 
-static inline int pmd_large(pmd_t pmd)
+static inline int hlpmd_large(pmd_t pmd)
 {
 	return !!(pmd_val(pmd) & H_PAGE_PTE);
 }
 
-static inline pmd_t pmd_mknotpresent(pmd_t pmd)
+static inline pmd_t hlpmd_mknotpresent(pmd_t pmd)
 {
 	return __pmd(pmd_val(pmd) & ~H_PAGE_PRESENT);
 }
 
-#define __HAVE_ARCH_PMD_SAME
-static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b)
+static inline pmd_t hlpmd_mkhuge(pmd_t pmd)
+{
+	return __pmd(pmd_val(pmd) | (H_PAGE_PTE | H_PAGE_THP_HUGE));
+}
+
+static inline int hlpmd_same(pmd_t pmd_a, pmd_t pmd_b)
 {
 	return (((pmd_val(pmd_a) ^ pmd_val(pmd_b)) & ~H_PAGE_HPTEFLAGS) == 0);
 }
 
-static inline int __pmdp_test_and_clear_young(struct mm_struct *mm,
+static inline int __hlpmdp_test_and_clear_young(struct mm_struct *mm,
 					      unsigned long addr, pmd_t *pmdp)
 {
 	unsigned long old;
 
 	if ((pmd_val(*pmdp) & (H_PAGE_ACCESSED | H_PAGE_HASHPTE)) == 0)
 		return 0;
-	old = pmd_hugepage_update(mm, addr, pmdp, H_PAGE_ACCESSED, 0);
+	old = hlpmd_hugepage_update(mm, addr, pmdp, H_PAGE_ACCESSED, 0);
 	return ((old & H_PAGE_ACCESSED) != 0);
 }
 
-#define __HAVE_ARCH_PMDP_SET_WRPROTECT
-static inline void pmdp_set_wrprotect(struct mm_struct *mm, unsigned long addr,
+static inline void hlpmdp_set_wrprotect(struct mm_struct *mm, unsigned long addr,
 				      pmd_t *pmdp)
 {
 
 	if ((pmd_val(*pmdp) & H_PAGE_RW) == 0)
 		return;
 
-	pmd_hugepage_update(mm, addr, pmdp, H_PAGE_RW, 0);
+	hlpmd_hugepage_update(mm, addr, pmdp, H_PAGE_RW, 0);
 }
 
 #endif /*  CONFIG_TRANSPARENT_HUGEPAGE */
+
 #endif	/* __ASSEMBLY__ */
 
 #endif /* _ASM_POWERPC_BOOK3S_64_HASH_64K_H */
diff --git a/arch/powerpc/include/asm/book3s/64/hash.h b/arch/powerpc/include/asm/book3s/64/hash.h
index 20bb9da200c6..f43b26c4d319 100644
--- a/arch/powerpc/include/asm/book3s/64/hash.h
+++ b/arch/powerpc/include/asm/book3s/64/hash.h
@@ -600,6 +600,20 @@ static inline void hpte_do_hugepage_flush(struct mm_struct *mm,
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
+extern int hlpmdp_set_access_flags(struct vm_area_struct *vma,
+                                   unsigned long address, pmd_t *pmdp,
+                                   pmd_t entry, int dirty);
+extern int hlpmdp_test_and_clear_young(struct vm_area_struct *vma,
+                                       unsigned long address, pmd_t *pmdp);
+extern pmd_t hlpmdp_huge_get_and_clear(struct mm_struct *mm,
+                                       unsigned long addr, pmd_t *pmdp);
+extern pmd_t hlpmdp_collapse_flush(struct vm_area_struct *vma,
+                                   unsigned long address, pmd_t *pmdp);
+extern void hlpgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
+                                         pgtable_t pgtable);
+extern pgtable_t hlpgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp);
+extern void hlpmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
+                              pmd_t *pmdp);
 extern int hlmap_kernel_page(unsigned long ea, unsigned long pa, int flags);
 extern void hlpgtable_cache_init(void);
 extern void __meminit hlvmemmap_create_mapping(unsigned long start,
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 213cc7b8dac2..5c5e03ed618f 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -509,15 +509,99 @@ static inline void update_mmu_cache(struct vm_area_struct *vma, unsigned long ad
 struct page *realmode_pfn_to_page(unsigned long pfn);
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
+/*
+ *
+ * For core kernel code by design pmd_trans_huge is never run on any hugetlbfs
+ * page. The hugetlbfs page table walking and mangling paths are totally
+ * separated form the core VM paths and they're differentiated by
+ *  VM_HUGETLB being set on vm_flags well before any pmd_trans_huge could run.
+ *
+ * pmd_trans_huge() is defined as false at build time if
+ * CONFIG_TRANSPARENT_HUGEPAGE=n to optimize away code blocks at build
+ * time in such case.
+ *
+ * For ppc64 we need to differntiate from explicit hugepages from THP, because
+ * for THP we also track the subpage details at the pmd level. We don't do
+ * that for explicit huge pages.
+ *
+ */
+static inline int pmd_trans_huge(pmd_t pmd)
+{
+	return hlpmd_trans_huge(pmd);
+}
+
 #define pfn_pmd pfn_pmd
-extern pmd_t pfn_pmd(unsigned long pfn, pgprot_t pgprot);
-extern pmd_t mk_pmd(struct page *page, pgprot_t pgprot);
-extern pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot);
-extern void set_pmd_at(struct mm_struct *mm, unsigned long addr,
-		       pmd_t *pmdp, pmd_t pmd);
-extern void update_mmu_cache_pmd(struct vm_area_struct *vma, unsigned long addr,
-				 pmd_t *pmd);
-extern int has_transparent_hugepage(void);
+static inline pmd_t pfn_pmd(unsigned long pfn, pgprot_t pgprot)
+{
+	return pfn_hlpmd(pfn, pgprot);
+}
+
+static inline pmd_t mk_pmd(struct page *page, pgprot_t pgprot)
+{
+	return mk_hlpmd(page, pgprot);
+}
+
+static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
+{
+	return hlpmd_modify(pmd, newprot);
+}
+/*
+ * This is called at the end of handling a user page fault, when the
+ * fault has been handled by updating a HUGE PMD entry in the linux page tables.
+ * We use it to preload an HPTE into the hash table corresponding to
+ * the updated linux HUGE PMD entry.
+ */
+static inline void update_mmu_cache_pmd(struct vm_area_struct *vma,
+					unsigned long addr, pmd_t *pmd)
+{
+	return;
+}
+
+static inline int has_transparent_hugepage(void)
+{
+	return hl_has_transparent_hugepage();
+}
+
+static inline void set_pmd_at(struct mm_struct *mm, unsigned long addr,
+			      pmd_t *pmdp, pmd_t pmd)
+{
+	return set_hlpmd_at(mm, addr, pmdp, pmd);
+}
+
+static inline int pmd_large(pmd_t pmd)
+{
+	return hlpmd_large(pmd);
+}
+
+static inline pmd_t pmd_mknotpresent(pmd_t pmd)
+{
+	return hlpmd_mknotpresent(pmd);
+}
+
+static inline pmd_t pmd_mkhuge(pmd_t pmd)
+{
+	return hlpmd_mkhuge(pmd);
+}
+
+#define __HAVE_ARCH_PMD_SAME
+static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b)
+{
+	return hlpmd_same(pmd_a, pmd_b);
+}
+
+static inline int __pmdp_test_and_clear_young(struct mm_struct *mm,
+					      unsigned long addr, pmd_t *pmdp)
+{
+	return __hlpmdp_test_and_clear_young(mm, addr, pmdp);
+}
+
+#define __HAVE_ARCH_PMDP_SET_WRPROTECT
+static inline void pmdp_set_wrprotect(struct mm_struct *mm, unsigned long addr,
+				      pmd_t *pmdp)
+{
+	return hlpmdp_set_wrprotect(mm, addr, pmdp);
+}
+
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */

@@ -562,37 +646,55 @@ static inline int pmd_protnone(pmd_t pmd)
 #define __HAVE_ARCH_PMD_WRITE
 #define pmd_write(pmd)		pte_write(pmd_pte(pmd))
 
-static inline pmd_t pmd_mkhuge(pmd_t pmd)
+#define __HAVE_ARCH_PMDP_SET_ACCESS_FLAGS
+static inline int pmdp_set_access_flags(struct vm_area_struct *vma,
+					unsigned long address, pmd_t *pmdp,
+					pmd_t entry, int dirty)
 {
-	return __pmd(pmd_val(pmd) | (H_PAGE_PTE | H_PAGE_THP_HUGE));
+	return hlpmdp_set_access_flags(vma, address, pmdp, entry, dirty);
 }
 
-#define __HAVE_ARCH_PMDP_SET_ACCESS_FLAGS
-extern int pmdp_set_access_flags(struct vm_area_struct *vma,
-				 unsigned long address, pmd_t *pmdp,
-				 pmd_t entry, int dirty);
-
 #define __HAVE_ARCH_PMDP_TEST_AND_CLEAR_YOUNG
-extern int pmdp_test_and_clear_young(struct vm_area_struct *vma,
-				     unsigned long address, pmd_t *pmdp);
+static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
+					    unsigned long address, pmd_t *pmdp)
+{
+	return hlpmdp_test_and_clear_young(vma, address, pmdp);
+}
+
 
 #define __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR
-extern pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
-				     unsigned long addr, pmd_t *pmdp);
+static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
+					    unsigned long addr, pmd_t *pmdp)
+{
+	return hlpmdp_huge_get_and_clear(mm, addr, pmdp);
+}
 
-extern pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
-				 unsigned long address, pmd_t *pmdp);
+static inline pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
+					unsigned long address, pmd_t *pmdp)
+{
+	return hlpmdp_collapse_flush(vma, address, pmdp);
+}
 #define pmdp_collapse_flush pmdp_collapse_flush
 
 #define __HAVE_ARCH_PGTABLE_DEPOSIT
-extern void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
-				       pgtable_t pgtable);
+static inline void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
+					      pgtable_t pgtable)
+{
+	return hlpgtable_trans_huge_deposit(mm, pmdp, pgtable);
+}
+
 #define __HAVE_ARCH_PGTABLE_WITHDRAW
-extern pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp);
+static inline pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp)
+{
+	return hlpgtable_trans_huge_withdraw(mm, pmdp);
+}
 
 #define __HAVE_ARCH_PMDP_INVALIDATE
-extern void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
-			    pmd_t *pmdp);
+static inline void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
+				   pmd_t *pmdp)
+{
+	return hlpmdp_invalidate(vma, address, pmdp);
+}
 
 #define pmd_move_must_withdraw pmd_move_must_withdraw
 struct spinlock;
diff --git a/arch/powerpc/mm/pgtable-hash64.c b/arch/powerpc/mm/pgtable-hash64.c
index 885764bdc022..c73dd27c339a 100644
--- a/arch/powerpc/mm/pgtable-hash64.c
+++ b/arch/powerpc/mm/pgtable-hash64.c
@@ -257,17 +257,17 @@ void set_hlpte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep,
  * handled those two for us, we additionally deal with missing execute
  * permission here on some processors
  */
-int pmdp_set_access_flags(struct vm_area_struct *vma, unsigned long address,
-			  pmd_t *pmdp, pmd_t entry, int dirty)
+int hlpmdp_set_access_flags(struct vm_area_struct *vma, unsigned long address,
+			    pmd_t *pmdp, pmd_t entry, int dirty)
 {
 	int changed;
 #ifdef CONFIG_DEBUG_VM
-	WARN_ON(!pmd_trans_huge(*pmdp));
+	WARN_ON(!hlpmd_trans_huge(*pmdp));
 	assert_spin_locked(&vma->vm_mm->page_table_lock);
 #endif
-	changed = !pmd_same(*(pmdp), entry);
+	changed = !hlpmd_same(*(pmdp), entry);
 	if (changed) {
-		__ptep_set_access_flags(pmdp_ptep(pmdp), pmd_pte(entry));
+		__hlptep_set_access_flags(pmdp_ptep(pmdp), pmd_pte(entry));
 		/*
 		 * Since we are not supporting SW TLB systems, we don't
 		 * have any thing similar to flush_tlb_page_nohash()
@@ -276,7 +276,7 @@ int pmdp_set_access_flags(struct vm_area_struct *vma, unsigned long address,
 	return changed;
 }
 
-unsigned long pmd_hugepage_update(struct mm_struct *mm, unsigned long addr,
+unsigned long hlpmd_hugepage_update(struct mm_struct *mm, unsigned long addr,
 				  pmd_t *pmdp, unsigned long clr,
 				  unsigned long set)
 {
@@ -284,7 +284,7 @@ unsigned long pmd_hugepage_update(struct mm_struct *mm, unsigned long addr,
 	unsigned long old, tmp;
 
 #ifdef CONFIG_DEBUG_VM
-	WARN_ON(!pmd_trans_huge(*pmdp));
+	WARN_ON(!hlpmd_trans_huge(*pmdp));
 	assert_spin_locked(&mm->page_table_lock);
 #endif
 
@@ -310,13 +310,13 @@ unsigned long pmd_hugepage_update(struct mm_struct *mm, unsigned long addr,
 	return old;
 }
 
-pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address,
+pmd_t hlpmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address,
 			  pmd_t *pmdp)
 {
 	pmd_t pmd;
 
 	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
-	VM_BUG_ON(pmd_trans_huge(*pmdp));
+	VM_BUG_ON(hlpmd_trans_huge(*pmdp));
 
 	pmd = *pmdp;
 	pmd_clear(pmdp);
@@ -357,17 +357,17 @@ pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address,
  * We should be more intelligent about this but for the moment we override
  * these functions and force a tlb flush unconditionally
  */
-int pmdp_test_and_clear_young(struct vm_area_struct *vma,
+int hlpmdp_test_and_clear_young(struct vm_area_struct *vma,
 			      unsigned long address, pmd_t *pmdp)
 {
-	return __pmdp_test_and_clear_young(vma->vm_mm, address, pmdp);
+	return __hlpmdp_test_and_clear_young(vma->vm_mm, address, pmdp);
 }
 
 /*
  * We want to put the pgtable in pmd and use pgtable for tracking
  * the base page size hptes
  */
-void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
+void hlpgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
 				pgtable_t pgtable)
 {
 	pgtable_t *pgtable_slot;
@@ -386,7 +386,7 @@ void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
 	smp_wmb();
 }
 
-pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp)
+pgtable_t hlpgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp)
 {
 	pgtable_t pgtable;
 	pgtable_t *pgtable_slot;
@@ -410,23 +410,23 @@ pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp)
  * set a new huge pmd. We should not be called for updating
  * an existing pmd entry. That should go via pmd_hugepage_update.
  */
-void set_pmd_at(struct mm_struct *mm, unsigned long addr,
+void set_hlpmd_at(struct mm_struct *mm, unsigned long addr,
 		pmd_t *pmdp, pmd_t pmd)
 {
 #ifdef CONFIG_DEBUG_VM
 	WARN_ON((pmd_val(*pmdp) & (H_PAGE_PRESENT | H_PAGE_USER)) ==
 		(H_PAGE_PRESENT | H_PAGE_USER));
 	assert_spin_locked(&mm->page_table_lock);
-	WARN_ON(!pmd_trans_huge(pmd));
+	WARN_ON(!hlpmd_trans_huge(pmd));
 #endif
 	trace_hugepage_set_pmd(addr, pmd_val(pmd));
-	return set_pte_at(mm, addr, pmdp_ptep(pmdp), pmd_pte(pmd));
+	return set_hlpte_at(mm, addr, pmdp_ptep(pmdp), pmd_pte(pmd));
 }
 
-void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
+void hlpmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
 		     pmd_t *pmdp)
 {
-	pmd_hugepage_update(vma->vm_mm, address, pmdp, H_PAGE_PRESENT, 0);
+	hlpmd_hugepage_update(vma->vm_mm, address, pmdp, H_PAGE_PRESENT, 0);
 }
 
 /*
@@ -468,31 +468,31 @@ void hpte_do_hugepage_flush(struct mm_struct *mm, unsigned long addr,
 	return flush_hash_hugepage(vsid, addr, pmdp, psize, ssize, flags);
 }
 
-static pmd_t pmd_set_protbits(pmd_t pmd, pgprot_t pgprot)
+static pmd_t hlpmd_set_protbits(pmd_t pmd, pgprot_t pgprot)
 {
 	return __pmd(pmd_val(pmd) | pgprot_val(pgprot));
 }
 
-pmd_t pfn_pmd(unsigned long pfn, pgprot_t pgprot)
+pmd_t pfn_hlpmd(unsigned long pfn, pgprot_t pgprot)
 {
 	unsigned long pmdv;
 
 	pmdv = pfn << H_PTE_RPN_SHIFT;
-	return pmd_set_protbits(__pmd(pmdv), pgprot);
+	return hlpmd_set_protbits(__pmd(pmdv), pgprot);
 }
 
-pmd_t mk_pmd(struct page *page, pgprot_t pgprot)
+pmd_t mk_hlpmd(struct page *page, pgprot_t pgprot)
 {
-	return pfn_pmd(page_to_pfn(page), pgprot);
+	return pfn_hlpmd(page_to_pfn(page), pgprot);
 }
 
-pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
+pmd_t hlpmd_modify(pmd_t pmd, pgprot_t newprot)
 {
 	unsigned long pmdv;
 
 	pmdv = pmd_val(pmd);
 	pmdv &= H_HPAGE_CHG_MASK;
-	return pmd_set_protbits(__pmd(pmdv), newprot);
+	return hlpmd_set_protbits(__pmd(pmdv), newprot);
 }
 
 /*
@@ -501,13 +501,13 @@ pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
  * We use it to preload an HPTE into the hash table corresponding to
  * the updated linux HUGE PMD entry.
  */
-void update_mmu_cache_pmd(struct vm_area_struct *vma, unsigned long addr,
+void hlupdate_mmu_cache_pmd(struct vm_area_struct *vma, unsigned long addr,
 			  pmd_t *pmd)
 {
 	return;
 }
 
-pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
+pmd_t hlpmdp_huge_get_and_clear(struct mm_struct *mm,
 			      unsigned long addr, pmd_t *pmdp)
 {
 	pmd_t old_pmd;
@@ -515,7 +515,7 @@ pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
 	unsigned long old;
 	pgtable_t *pgtable_slot;
 
-	old = pmd_hugepage_update(mm, addr, pmdp, ~0UL, 0);
+	old = hlpmd_hugepage_update(mm, addr, pmdp, ~0UL, 0);
 	old_pmd = __pmd(old);
 	/*
 	 * We have pmd == none and we are holding page_table_lock.
@@ -543,7 +543,7 @@ pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
 	return old_pmd;
 }
 
-int has_transparent_hugepage(void)
+int hl_has_transparent_hugepage(void)
 {
 
 	BUILD_BUG_ON_MSG((H_PMD_SHIFT - PAGE_SHIFT) >= MAX_ORDER,
-- 
2.5.0