[PATCH] rmap 12 pgtable remove rmap

From: Hugh Dickins <hugh@veritas.com>

Remove the support for pte_chain rmap from page table initialization, just
continue to maintain nr_page_table_pages (but only for user page tables -
it also counted vmalloc page tables before, little need, and I'm unsure if
per-cpu stats are safe early enough on all arches).  mm/memory.c is the
only core file affected.

But ppc and ppc64 have found the old rmap page table initialization useful
to support their ptep_test_and_clear_young: so transfer rmap's
initialization to them (even on kernel page tables?  well, okay).

arch/arm/mm/mm-armv.c

@@ -18,7 +18,6 @@
 
 #include <asm/pgalloc.h>
 #include <asm/page.h>
-#include <asm/rmap.h>
 #include <asm/io.h>
 #include <asm/setup.h>
 #include <asm/tlbflush.h>
@@ -231,7 +230,7 @@ void free_pgd_slow(pgd_t *pgd)
 
 	pte = pmd_page(*pmd);
 	pmd_clear(pmd);
-	pgtable_remove_rmap(pte);
+	dec_page_state(nr_page_table_pages);
 	pte_free(pte);
 	pmd_free(pmd);
 free:

arch/ppc/mm/pgtable.c

@@ -86,9 +86,14 @@ pte_t *pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)
 	extern int mem_init_done;
 	extern void *early_get_page(void);
 
-	if (mem_init_done)
+	if (mem_init_done) {
 		pte = (pte_t *)__get_free_page(GFP_KERNEL|__GFP_REPEAT);
-	else
+		if (pte) {
+			struct page *ptepage = virt_to_page(pte);
+			ptepage->mapping = (void *) mm;
+			ptepage->index = address & PMD_MASK;
+		}
+	} else
 		pte = (pte_t *)early_get_page();
 	if (pte)
 		clear_page(pte);
@@ -97,7 +102,7 @@ pte_t *pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)
 
 struct page *pte_alloc_one(struct mm_struct *mm, unsigned long address)
 {
-	struct page *pte;
+	struct page *ptepage;
 
 #ifdef CONFIG_HIGHPTE
 	int flags = GFP_KERNEL | __GFP_HIGHMEM | __GFP_REPEAT;
@@ -105,10 +110,13 @@ struct page *pte_alloc_one(struct mm_struct *mm, unsigned long address)
 	int flags = GFP_KERNEL | __GFP_REPEAT;
 #endif
 
-	pte = alloc_pages(flags, 0);
-	if (pte)
-		clear_highpage(pte);
-	return pte;
+	ptepage = alloc_pages(flags, 0);
+	if (ptepage) {
+		ptepage->mapping = (void *) mm;
+		ptepage->index = address & PMD_MASK;
+		clear_highpage(ptepage);
+	}
+	return ptepage;
 }
 
 void pte_free_kernel(pte_t *pte)
@@ -116,15 +124,17 @@ void pte_free_kernel(pte_t *pte)
 #ifdef CONFIG_SMP
 	hash_page_sync();
 #endif
+	virt_to_page(pte)->mapping = NULL;
 	free_page((unsigned long)pte);
 }
 
-void pte_free(struct page *pte)
+void pte_free(struct page *ptepage)
 {
 #ifdef CONFIG_SMP
 	hash_page_sync();
 #endif
-	__free_page(pte);
+	ptepage->mapping = NULL;
+	__free_page(ptepage);
 }
 
 #ifndef CONFIG_44x

arch/ppc64/mm/hugetlbpage.c

@@ -24,7 +24,6 @@
 #include <asm/machdep.h>
 #include <asm/cputable.h>
 #include <asm/tlb.h>
-#include <asm/rmap.h>
 
 #include <linux/sysctl.h>
 
@@ -214,7 +213,7 @@ static int prepare_low_seg_for_htlb(struct mm_struct *mm, unsigned long seg)
 		}
 		page = pmd_page(*pmd);
 		pmd_clear(pmd);
-		pgtable_remove_rmap(page);
+		dec_page_state(nr_page_table_pages);
 		pte_free_tlb(tlb, page);
 	}
 	tlb_finish_mmu(tlb, start, end);

arch/ppc64/mm/tlb.c

@@ -31,7 +31,6 @@
 #include <asm/tlb.h>
 #include <asm/hardirq.h>
 #include <linux/highmem.h>
-#include <asm/rmap.h>
 
 DEFINE_PER_CPU(struct ppc64_tlb_batch, ppc64_tlb_batch);
 
@@ -59,7 +58,8 @@ void hpte_update(pte_t *ptep, unsigned long pte, int wrprot)
 
 	ptepage = virt_to_page(ptep);
 	mm = (struct mm_struct *) ptepage->mapping;
-	addr = ptep_to_address(ptep);
+	addr = ptepage->index +
+		(((unsigned long)ptep & ~PAGE_MASK) * PTRS_PER_PTE);
 
 	if (REGION_ID(addr) == USER_REGION_ID)
 		context = mm->context.id;

include/asm-ppc64/pgalloc.h

@@ -48,28 +48,43 @@ pmd_free(pmd_t *pmd)
 	pmd_populate_kernel(mm, pmd, page_address(pte_page))
 
 static inline pte_t *
-pte_alloc_one_kernel(struct mm_struct *mm, unsigned long addr)
+pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)
 {
-	return kmem_cache_alloc(zero_cache, GFP_KERNEL|__GFP_REPEAT);
+	pte_t *pte;
+	pte = kmem_cache_alloc(zero_cache, GFP_KERNEL|__GFP_REPEAT);
+	if (pte) {
+		struct page *ptepage = virt_to_page(pte);
+		ptepage->mapping = (void *) mm;
+		ptepage->index = address & PMD_MASK;
+	}
+	return pte;
 }
 
 static inline struct page *
 pte_alloc_one(struct mm_struct *mm, unsigned long address)
 {
-	pte_t *pte = pte_alloc_one_kernel(mm, address);
-
-	if (pte)
-		return virt_to_page(pte);
-
+	pte_t *pte;
+	pte = kmem_cache_alloc(zero_cache, GFP_KERNEL|__GFP_REPEAT);
+	if (pte) {
+		struct page *ptepage = virt_to_page(pte);
+		ptepage->mapping = (void *) mm;
+		ptepage->index = address & PMD_MASK;
+		return ptepage;
+	}
 	return NULL;
 }
 		
 static inline void pte_free_kernel(pte_t *pte)
 {
+	virt_to_page(pte)->mapping = NULL;
 	kmem_cache_free(zero_cache, pte);
 }
 
-#define pte_free(pte_page)	pte_free_kernel(page_address(pte_page))
+static inline void pte_free(struct page *ptepage)
+{
+	ptepage->mapping = NULL;
+	kmem_cache_free(zero_cache, page_address(ptepage));
+}
 
 struct pte_freelist_batch
 {

mm/memory.c

@@ -48,7 +48,6 @@
 #include <linux/init.h>
 
 #include <asm/pgalloc.h>
-#include <asm/rmap.h>
 #include <asm/uaccess.h>
 #include <asm/tlb.h>
 #include <asm/tlbflush.h>
@@ -105,7 +104,7 @@ static inline void free_one_pmd(struct mmu_gather *tlb, pmd_t * dir)
 	}
 	page = pmd_page(*dir);
 	pmd_clear(dir);
-	pgtable_remove_rmap(page);
+	dec_page_state(nr_page_table_pages);
 	pte_free_tlb(tlb, page);
 }
 
@@ -164,7 +163,7 @@ pte_t fastcall * pte_alloc_map(struct mm_struct *mm, pmd_t *pmd, unsigned long a
 			pte_free(new);
 			goto out;
 		}
-		pgtable_add_rmap(new, mm, address);
+		inc_page_state(nr_page_table_pages);
 		pmd_populate(mm, pmd, new);
 	}
 out:
@@ -190,7 +189,6 @@ pte_t fastcall * pte_alloc_kernel(struct mm_struct *mm, pmd_t *pmd, unsigned lon
 			pte_free_kernel(new);
 			goto out;
 		}
-		pgtable_add_rmap(virt_to_page(new), mm, address);
 		pmd_populate_kernel(mm, pmd, new);
 	}
 out: