m68k: mm: Extend table allocator for multiple sizes

In addition to the PGD/PMD table size (128*4) add a PTE table size
(64*4) to the table allocator. This completely removes the pte-table
overhead compared to the old code, even for dense tables.

Notes:

 - the allocator gained a list_empty() check to deal with there not
   being any pages at all.

 - the free mask is extended to cover more than the 8 bits required
   for the (512 byte) PGD/PMD tables.

 - NR_PAGETABLE accounting is restored.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Greg Ungerer <gerg@linux-m68k.org>
Tested-by: Michael Schmitz <schmitzmic@gmail.com>
Tested-by: Greg Ungerer <gerg@linux-m68k.org>
Link: https://lore.kernel.org/r/20200131125403.882175409@infradead.org
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

2 files changed, 51 insertions, 30 deletions

diff --git a/arch/m68k/mm/init.c b/arch/m68k/mm/init.c
index a9b6d26cff8a..3e3a74a5b215 100644
--- a/arch/m68k/mm/init.c
+++ b/arch/m68k/mm/init.c
@@ -40,10 +40,6 @@
 void *empty_zero_page;
 EXPORT_SYMBOL(empty_zero_page);
 
-#if !defined(CONFIG_SUN3) && !defined(CONFIG_COLDFIRE)
-extern void init_pointer_table(unsigned long ptable);
-#endif
-
 #ifdef CONFIG_MMU
 
 pg_data_t pg_data_map[MAX_NUMNODES];
@@ -127,12 +123,16 @@ static inline void init_pointer_tables(void)
 	int i;
 
 	/* insert pointer tables allocated so far into the tablelist */
-	init_pointer_table((unsigned long)kernel_pg_dir);
+	init_pointer_table(kernel_pg_dir, TABLE_PGD);
 	for (i = 0; i < PTRS_PER_PGD; i++) {
-		pud_t *pud = (pud_t *)(&kernel_pg_dir[i]);
+		pud_t *pud = (pud_t *)&kernel_pg_dir[i];
+		pmd_t *pmd_dir;
+
+		if (!pud_present(*pud))
+			continue;
 
-		if (pud_present(*pud))
-			init_pointer_table(pgd_page_vaddr(kernel_pg_dir[i]));
+		pmd_dir = (pmd_t *)pgd_page_vaddr(kernel_pg_dir[i]);
+		init_pointer_table(pmd_dir, TABLE_PMD);
 	}
 #endif
 }
diff --git a/arch/m68k/mm/motorola.c b/arch/m68k/mm/motorola.c
index 600f9c1d96f8..fc16190ec2d6 100644
--- a/arch/m68k/mm/motorola.c
+++ b/arch/m68k/mm/motorola.c
@@ -72,24 +72,35 @@ void mmu_page_dtor(void *page)
    arch/sparc/mm/srmmu.c ... */
 
 typedef struct list_head ptable_desc;
-static LIST_HEAD(ptable_list);
+
+static struct list_head ptable_list[2] = {
+	LIST_HEAD_INIT(ptable_list[0]),
+	LIST_HEAD_INIT(ptable_list[1]),
+};
 
 #define PD_PTABLE(page) ((ptable_desc *)&(virt_to_page(page)->lru))
 #define PD_PAGE(ptable) (list_entry(ptable, struct page, lru))
-#define PD_MARKBITS(dp) (*(unsigned char *)&PD_PAGE(dp)->index)
+#define PD_MARKBITS(dp) (*(unsigned int *)&PD_PAGE(dp)->index)
+
+static const int ptable_shift[2] = {
+	7+2, /* PGD, PMD */
+	6+2, /* PTE */
+};
 
-#define PTABLE_SIZE (PTRS_PER_PMD * sizeof(pmd_t))
+#define ptable_size(type) (1U << ptable_shift[type])
+#define ptable_mask(type) ((1U << (PAGE_SIZE / ptable_size(type))) - 1)
 
-void __init init_pointer_table(unsigned long ptable)
+void __init init_pointer_table(void *table, int type)
 {
 	ptable_desc *dp;
+	unsigned long ptable = (unsigned long)table;
 	unsigned long page = ptable & PAGE_MASK;
-	unsigned char mask = 1 << ((ptable - page)/PTABLE_SIZE);
+	unsigned int mask = 1U << ((ptable - page)/ptable_size(type));
 
 	dp = PD_PTABLE(page);
 	if (!(PD_MARKBITS(dp) & mask)) {
-		PD_MARKBITS(dp) = 0xff;
-		list_add(dp, &ptable_list);
+		PD_MARKBITS(dp) = ptable_mask(type);
+		list_add(dp, &ptable_list[type]);
 	}
 
 	PD_MARKBITS(dp) &= ~mask;
@@ -102,12 +113,11 @@ void __init init_pointer_table(unsigned long ptable)
 	return;
 }
 
-pmd_t *get_pointer_table (void)
+void *get_pointer_table(int type)
 {
-	ptable_desc *dp = ptable_list.next;
-	unsigned char mask = PD_MARKBITS (dp);
-	unsigned char tmp;
-	unsigned int off;
+	ptable_desc *dp = ptable_list[type].next;
+	unsigned int mask = list_empty(&ptable_list[type]) ? 0 : PD_MARKBITS(dp);
+	unsigned int tmp, off;
 
 	/*
 	 * For a pointer table for a user process address space, a
@@ -122,30 +132,39 @@ pmd_t *get_pointer_table (void)
 		if (!(page = (void *)get_zeroed_page(GFP_KERNEL)))
 			return NULL;
 
+		if (type == TABLE_PTE) {
+			/*
+			 * m68k doesn't have SPLIT_PTE_PTLOCKS for not having
+			 * SMP.
+			 */
+			pgtable_pte_page_ctor(virt_to_page(page));
+		}
+
 		mmu_page_ctor(page);
 
 		new = PD_PTABLE(page);
-		PD_MARKBITS(new) = 0xfe;
+		PD_MARKBITS(new) = ptable_mask(type) - 1;
 		list_add_tail(new, dp);
 
 		return (pmd_t *)page;
 	}
 
-	for (tmp = 1, off = 0; (mask & tmp) == 0; tmp <<= 1, off += PTABLE_SIZE)
+	for (tmp = 1, off = 0; (mask & tmp) == 0; tmp <<= 1, off += ptable_size(type))
 		;
 	PD_MARKBITS(dp) = mask & ~tmp;
 	if (!PD_MARKBITS(dp)) {
 		/* move to end of list */
-		list_move_tail(dp, &ptable_list);
+		list_move_tail(dp, &ptable_list[type]);
 	}
-	return (pmd_t *) (page_address(PD_PAGE(dp)) + off);
+	return page_address(PD_PAGE(dp)) + off;
 }
 
-int free_pointer_table (pmd_t *ptable)
+int free_pointer_table(void *table, int type)
 {
 	ptable_desc *dp;
-	unsigned long page = (unsigned long)ptable & PAGE_MASK;
-	unsigned char mask = 1 << (((unsigned long)ptable - page)/PTABLE_SIZE);
+	unsigned long ptable = (unsigned long)table;
+	unsigned long page = ptable & PAGE_MASK;
+	unsigned int mask = 1U << ((ptable - page)/ptable_size(type));
 
 	dp = PD_PTABLE(page);
 	if (PD_MARKBITS (dp) & mask)
@@ -153,18 +172,20 @@ int free_pointer_table (pmd_t *ptable)
 
 	PD_MARKBITS (dp) |= mask;
 
-	if (PD_MARKBITS(dp) == 0xff) {
+	if (PD_MARKBITS(dp) == ptable_mask(type)) {
 		/* all tables in page are free, free page */
 		list_del(dp);
 		mmu_page_dtor((void *)page);
+		if (type == TABLE_PTE)
+			pgtable_pte_page_dtor(virt_to_page(page));
 		free_page (page);
 		return 1;
-	} else if (ptable_list.next != dp) {
+	} else if (ptable_list[type].next != dp) {
 		/*
 		 * move this descriptor to the front of the list, since
 		 * it has one or more free tables.
 		 */
-		list_move(dp, &ptable_list);
+		list_move(dp, &ptable_list[type]);
 	}
 	return 0;
 }