arch/s390/mm/pgtable.c - pub/scm/linux/kernel/git/stable/linux-stable - Git at Google

 /*
  *    Copyright IBM Corp. 2007,2009
  *    Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
  */

 #include <linux/sched.h>
 #include <linux/kernel.h>
 #include <linux/errno.h>
 #include <linux/gfp.h>
 #include <linux/mm.h>
 #include <linux/swap.h>
 #include <linux/smp.h>
 #include <linux/highmem.h>
 #include <linux/pagemap.h>
 #include <linux/spinlock.h>
 #include <linux/module.h>
 #include <linux/quicklist.h>
 #include <linux/rcupdate.h>

 #include <asm/system.h>
 #include <asm/pgtable.h>
 #include <asm/pgalloc.h>
 #include <asm/tlb.h>
 #include <asm/tlbflush.h>
 #include <asm/mmu_context.h>

 #ifndef CONFIG_64BIT
 #define ALLOC_ORDER	1
 #define FRAG_MASK	0x0f
 #else
 #define ALLOC_ORDER	2
 #define FRAG_MASK	0x03
 #endif

 unsigned long VMALLOC_START = VMALLOC_END - VMALLOC_SIZE;
 EXPORT_SYMBOL(VMALLOC_START);

 static int __init parse_vmalloc(char *arg)
 {
 	if (!arg)
 		return -EINVAL;
 	VMALLOC_START = (VMALLOC_END - memparse(arg, &arg)) & PAGE_MASK;
 	return 0;
 }
 early_param("vmalloc", parse_vmalloc);

 unsigned long *crst_table_alloc(struct mm_struct *mm)
 {
 	struct page *page = alloc_pages(GFP_KERNEL, ALLOC_ORDER);

 	if (!page)
 		return NULL;
 	return (unsigned long *) page_to_phys(page);
 }

 void crst_table_free(struct mm_struct *mm, unsigned long *table)
 {
 	free_pages((unsigned long) table, ALLOC_ORDER);
 }

 #ifdef CONFIG_64BIT
 int crst_table_upgrade(struct mm_struct *mm, unsigned long limit)
 {
 	unsigned long *table, *pgd;
 	unsigned long entry;

 	BUG_ON(limit > (1UL << 53));
 repeat:
 	table = crst_table_alloc(mm);
 	if (!table)
 		return -ENOMEM;
 	spin_lock_bh(&mm->page_table_lock);
 	if (mm->context.asce_limit < limit) {
 		pgd = (unsigned long *) mm->pgd;
 		if (mm->context.asce_limit <= (1UL << 31)) {
 			entry = _REGION3_ENTRY_EMPTY;
 			mm->context.asce_limit = 1UL << 42;
 			mm->context.asce_bits = _ASCE_TABLE_LENGTH |
 						_ASCE_USER_BITS |
 						_ASCE_TYPE_REGION3;
 		} else {
 			entry = _REGION2_ENTRY_EMPTY;
 			mm->context.asce_limit = 1UL << 53;
 			mm->context.asce_bits = _ASCE_TABLE_LENGTH |
 						_ASCE_USER_BITS |
 						_ASCE_TYPE_REGION2;
 		}
 		crst_table_init(table, entry);
 		pgd_populate(mm, (pgd_t *) table, (pud_t *) pgd);
 		mm->pgd = (pgd_t *) table;
 		mm->task_size = mm->context.asce_limit;
 		table = NULL;
 	}
 	spin_unlock_bh(&mm->page_table_lock);
 	if (table)
 		crst_table_free(mm, table);
 	if (mm->context.asce_limit < limit)
 		goto repeat;
 	update_mm(mm, current);
 	return 0;
 }

 void crst_table_downgrade(struct mm_struct *mm, unsigned long limit)
 {
 	pgd_t *pgd;

 	if (mm->context.asce_limit <= limit)
 		return;
 	__tlb_flush_mm(mm);
 	while (mm->context.asce_limit > limit) {
 		pgd = mm->pgd;
 		switch (pgd_val(*pgd) & _REGION_ENTRY_TYPE_MASK) {
 		case _REGION_ENTRY_TYPE_R2:
 			mm->context.asce_limit = 1UL << 42;
 			mm->context.asce_bits = _ASCE_TABLE_LENGTH |
 						_ASCE_USER_BITS |
 						_ASCE_TYPE_REGION3;
 			break;
 		case _REGION_ENTRY_TYPE_R3:
 			mm->context.asce_limit = 1UL << 31;
 			mm->context.asce_bits = _ASCE_TABLE_LENGTH |
 						_ASCE_USER_BITS |
 						_ASCE_TYPE_SEGMENT;
 			break;
 		default:
 			BUG();
 		}
 		mm->pgd = (pgd_t *) (pgd_val(*pgd) & _REGION_ENTRY_ORIGIN);
 		mm->task_size = mm->context.asce_limit;
 		crst_table_free(mm, (unsigned long *) pgd);
 	}
 	update_mm(mm, current);
 }
 #endif

 static inline unsigned int atomic_xor_bits(atomic_t *v, unsigned int bits)
 {
 	unsigned int old, new;

 	do {
 		old = atomic_read(v);
 		new = old ^ bits;
 	} while (atomic_cmpxchg(v, old, new) != old);
 	return new;
 }

 /*
  * page table entry allocation/free routines.
  */
 #ifdef CONFIG_PGSTE
 static inline unsigned long *page_table_alloc_pgste(struct mm_struct *mm)
 {
 	struct page *page;
 	unsigned long *table;

 	page = alloc_page(GFP_KERNEL|__GFP_REPEAT);
 	if (!page)
 		return NULL;
 	pgtable_page_ctor(page);
 	atomic_set(&page->_mapcount, 3);
 	table = (unsigned long *) page_to_phys(page);
 	clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE/2);
 	clear_table(table + PTRS_PER_PTE, 0, PAGE_SIZE/2);
 	return table;
 }

 static inline void page_table_free_pgste(unsigned long *table)
 {
 	struct page *page;

 	page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 	pgtable_page_ctor(page);
 	atomic_set(&page->_mapcount, -1);
 	__free_page(page);
 }
 #endif

 unsigned long *page_table_alloc(struct mm_struct *mm)
 {
 	struct page *page;
 	unsigned long *table;
 	unsigned int mask, bit;

 #ifdef CONFIG_PGSTE
 	if (mm_has_pgste(mm))
 		return page_table_alloc_pgste(mm);
 #endif
 	/* Allocate fragments of a 4K page as 1K/2K page table */
 	spin_lock_bh(&mm->context.list_lock);
 	mask = FRAG_MASK;
 	if (!list_empty(&mm->context.pgtable_list)) {
 		page = list_first_entry(&mm->context.pgtable_list,
 					struct page, lru);
 		table = (unsigned long *) page_to_phys(page);
 		mask = atomic_read(&page->_mapcount);
 		mask = mask | (mask >> 4);
 	}
 	if ((mask & FRAG_MASK) == FRAG_MASK) {
 		spin_unlock_bh(&mm->context.list_lock);
 		page = alloc_page(GFP_KERNEL|__GFP_REPEAT);
 		if (!page)
 			return NULL;
 		pgtable_page_ctor(page);
 		atomic_set(&page->_mapcount, 1);
 		table = (unsigned long *) page_to_phys(page);
 		clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE);
 		spin_lock_bh(&mm->context.list_lock);
 		list_add(&page->lru, &mm->context.pgtable_list);
 	} else {
 		for (bit = 1; mask & bit; bit <<= 1)
 			table += PTRS_PER_PTE;
 		mask = atomic_xor_bits(&page->_mapcount, bit);
 		if ((mask & FRAG_MASK) == FRAG_MASK)
 			list_del(&page->lru);
 	}
 	spin_unlock_bh(&mm->context.list_lock);
 	return table;
 }

 void page_table_free(struct mm_struct *mm, unsigned long *table)
 {
 	struct page *page;
 	unsigned int bit, mask;

 #ifdef CONFIG_PGSTE
 	if (mm_has_pgste(mm))
 		return page_table_free_pgste(table);
 #endif
 	/* Free 1K/2K page table fragment of a 4K page */
 	page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 	bit = 1 << ((__pa(table) & ~PAGE_MASK)/(PTRS_PER_PTE*sizeof(pte_t)));
 	spin_lock_bh(&mm->context.list_lock);
 	if ((atomic_read(&page->_mapcount) & FRAG_MASK) != FRAG_MASK)
 		list_del(&page->lru);
 	mask = atomic_xor_bits(&page->_mapcount, bit);
 	if (mask & FRAG_MASK)
 		list_add(&page->lru, &mm->context.pgtable_list);
 	spin_unlock_bh(&mm->context.list_lock);
 	if (mask == 0) {
 		pgtable_page_dtor(page);
 		atomic_set(&page->_mapcount, -1);
 		__free_page(page);
 	}
 }

 static void __page_table_free_rcu(void *table, unsigned bit)
 {
 	struct page *page;

 #ifdef CONFIG_PGSTE
 	if (bit == FRAG_MASK)
 		return page_table_free_pgste(table);
 #endif
 	/* Free 1K/2K page table fragment of a 4K page */
 	page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 	if (atomic_xor_bits(&page->_mapcount, bit) == 0) {
 		pgtable_page_dtor(page);
 		atomic_set(&page->_mapcount, -1);
 		__free_page(page);
 	}
 }

 void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table)
 {
 	struct mm_struct *mm;
 	struct page *page;
 	unsigned int bit, mask;

 	mm = tlb->mm;
 #ifdef CONFIG_PGSTE
 	if (mm_has_pgste(mm)) {
 		table = (unsigned long *) (__pa(table) | FRAG_MASK);
 		tlb_remove_table(tlb, table);
 		return;
 	}
 #endif
 	bit = 1 << ((__pa(table) & ~PAGE_MASK) / (PTRS_PER_PTE*sizeof(pte_t)));
 	page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 	spin_lock_bh(&mm->context.list_lock);
 	if ((atomic_read(&page->_mapcount) & FRAG_MASK) != FRAG_MASK)
 		list_del(&page->lru);
 	mask = atomic_xor_bits(&page->_mapcount, bit | (bit << 4));
 	if (mask & FRAG_MASK)
 		list_add_tail(&page->lru, &mm->context.pgtable_list);
 	spin_unlock_bh(&mm->context.list_lock);
 	table = (unsigned long *) (__pa(table) | (bit << 4));
 	tlb_remove_table(tlb, table);
 }

 void __tlb_remove_table(void *_table)
 {
 	const unsigned long mask = (FRAG_MASK << 4) | FRAG_MASK;
 	void *table = (void *)((unsigned long) _table & ~mask);
 	unsigned type = (unsigned long) _table & mask;

 	if (type)
 		__page_table_free_rcu(table, type);
 	else
 		free_pages((unsigned long) table, ALLOC_ORDER);
 }

 static void tlb_remove_table_smp_sync(void *arg)
 {
 	/* Simply deliver the interrupt */
 }

 static void tlb_remove_table_one(void *table)
 {
 	/*
 	 * This isn't an RCU grace period and hence the page-tables cannot be
 	 * assumed to be actually RCU-freed.
 	 *
 	 * It is however sufficient for software page-table walkers that rely
 	 * on IRQ disabling. See the comment near struct mmu_table_batch.
 	 */
 	smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
 	__tlb_remove_table(table);
 }

 static void tlb_remove_table_rcu(struct rcu_head *head)
 {
 	struct mmu_table_batch *batch;
 	int i;

 	batch = container_of(head, struct mmu_table_batch, rcu);

 	for (i = 0; i < batch->nr; i++)
 		__tlb_remove_table(batch->tables[i]);

 	free_page((unsigned long)batch);
 }

 void tlb_table_flush(struct mmu_gather *tlb)
 {
 	struct mmu_table_batch **batch = &tlb->batch;

 	if (*batch) {
 		__tlb_flush_mm(tlb->mm);
 		call_rcu_sched(&(*batch)->rcu, tlb_remove_table_rcu);
 		*batch = NULL;
 	}
 }

 void tlb_remove_table(struct mmu_gather *tlb, void *table)
 {
 	struct mmu_table_batch **batch = &tlb->batch;

 	if (*batch == NULL) {
 		*batch = (struct mmu_table_batch *)
 			__get_free_page(GFP_NOWAIT | __GFP_NOWARN);
 		if (*batch == NULL) {
 			__tlb_flush_mm(tlb->mm);
 			tlb_remove_table_one(table);
 			return;
 		}
 		(*batch)->nr = 0;
 	}
 	(*batch)->tables[(*batch)->nr++] = table;
 	if ((*batch)->nr == MAX_TABLE_BATCH)
 		tlb_table_flush(tlb);
 }

 /*
  * switch on pgstes for its userspace process (for kvm)
  */
 int s390_enable_sie(void)
 {
 	struct task_struct *tsk = current;
 	struct mm_struct *mm, *old_mm;

 	/* Do we have switched amode? If no, we cannot do sie */
 	if (user_mode == HOME_SPACE_MODE)
 		return -EINVAL;

 	/* Do we have pgstes? if yes, we are done */
 	if (mm_has_pgste(tsk->mm))
 		return 0;

 	/* lets check if we are allowed to replace the mm */
 	task_lock(tsk);
 	if (!tsk->mm || atomic_read(&tsk->mm->mm_users) > 1 ||
 #ifdef CONFIG_AIO
 	    !hlist_empty(&tsk->mm->ioctx_list) ||
 #endif
 	    tsk->mm != tsk->active_mm) {
 		task_unlock(tsk);
 		return -EINVAL;
 	}
 	task_unlock(tsk);

 	/* we copy the mm and let dup_mm create the page tables with_pgstes */
 	tsk->mm->context.alloc_pgste = 1;
 	mm = dup_mm(tsk);
 	tsk->mm->context.alloc_pgste = 0;
 	if (!mm)
 		return -ENOMEM;

 	/* Now lets check again if something happened */
 	task_lock(tsk);
 	if (!tsk->mm || atomic_read(&tsk->mm->mm_users) > 1 ||
 #ifdef CONFIG_AIO
 	    !hlist_empty(&tsk->mm->ioctx_list) ||
 #endif
 	    tsk->mm != tsk->active_mm) {
 		mmput(mm);
 		task_unlock(tsk);
 		return -EINVAL;
 	}

 	/* ok, we are alone. No ptrace, no threads, etc. */
 	old_mm = tsk->mm;
 	tsk->mm = tsk->active_mm = mm;
 	preempt_disable();
 	update_mm(mm, tsk);
 	atomic_inc(&mm->context.attach_count);
 	atomic_dec(&old_mm->context.attach_count);
 	cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
 	preempt_enable();
 	task_unlock(tsk);
 	mmput(old_mm);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(s390_enable_sie);

 #if defined(CONFIG_DEBUG_PAGEALLOC) && defined(CONFIG_HIBERNATION)
 bool kernel_page_present(struct page *page)
 {
 	unsigned long addr;
 	int cc;

 	addr = page_to_phys(page);
 	asm volatile(
 		"	lra	%1,0(%1)\n"
 		"	ipm	%0\n"
 		"	srl	%0,28"
 		: "=d" (cc), "+a" (addr) : : "cc");
 	return cc == 0;
 }
 #endif /* CONFIG_HIBERNATION && CONFIG_DEBUG_PAGEALLOC */
	/*
	* Copyright IBM Corp. 2007,2009
	* Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
	*/

	#include <linux/sched.h>
	#include <linux/kernel.h>
	#include <linux/errno.h>
	#include <linux/gfp.h>
	#include <linux/mm.h>
	#include <linux/swap.h>
	#include <linux/smp.h>
	#include <linux/highmem.h>
	#include <linux/pagemap.h>
	#include <linux/spinlock.h>
	#include <linux/module.h>
	#include <linux/quicklist.h>
	#include <linux/rcupdate.h>

	#include <asm/system.h>
	#include <asm/pgtable.h>
	#include <asm/pgalloc.h>
	#include <asm/tlb.h>
	#include <asm/tlbflush.h>
	#include <asm/mmu_context.h>

	#ifndef CONFIG_64BIT
	#define ALLOC_ORDER 1
	#define FRAG_MASK 0x0f
	#else
	#define ALLOC_ORDER 2
	#define FRAG_MASK 0x03
	#endif

	unsigned long VMALLOC_START = VMALLOC_END - VMALLOC_SIZE;
	EXPORT_SYMBOL(VMALLOC_START);

	static int __init parse_vmalloc(char *arg)
	{
	if (!arg)
	return -EINVAL;
	VMALLOC_START = (VMALLOC_END - memparse(arg, &arg)) & PAGE_MASK;
	return 0;
	}
	early_param("vmalloc", parse_vmalloc);

	unsigned long crst_table_alloc(struct mm_struct mm)
	{
	struct page *page = alloc_pages(GFP_KERNEL, ALLOC_ORDER);

	if (!page)
	return NULL;
	return (unsigned long *) page_to_phys(page);
	}

	void crst_table_free(struct mm_struct mm, unsigned long table)
	{
	free_pages((unsigned long) table, ALLOC_ORDER);
	}

	#ifdef CONFIG_64BIT
	int crst_table_upgrade(struct mm_struct *mm, unsigned long limit)
	{
	unsigned long table, pgd;
	unsigned long entry;

	BUG_ON(limit > (1UL << 53));
	repeat:
	table = crst_table_alloc(mm);
	if (!table)
	return -ENOMEM;
	spin_lock_bh(&mm->page_table_lock);
	if (mm->context.asce_limit < limit) {
	pgd = (unsigned long *) mm->pgd;
	if (mm->context.asce_limit <= (1UL << 31)) {
	entry = _REGION3_ENTRY_EMPTY;
	mm->context.asce_limit = 1UL << 42;
	mm->context.asce_bits = _ASCE_TABLE_LENGTH \|
	_ASCE_USER_BITS \|
	_ASCE_TYPE_REGION3;
	} else {
	entry = _REGION2_ENTRY_EMPTY;
	mm->context.asce_limit = 1UL << 53;
	mm->context.asce_bits = _ASCE_TABLE_LENGTH \|
	_ASCE_USER_BITS \|
	_ASCE_TYPE_REGION2;
	}
	crst_table_init(table, entry);
	pgd_populate(mm, (pgd_t ) table, (pud_t ) pgd);
	mm->pgd = (pgd_t *) table;
	mm->task_size = mm->context.asce_limit;
	table = NULL;
	}
	spin_unlock_bh(&mm->page_table_lock);
	if (table)
	crst_table_free(mm, table);
	if (mm->context.asce_limit < limit)
	goto repeat;
	update_mm(mm, current);
	return 0;
	}

	void crst_table_downgrade(struct mm_struct *mm, unsigned long limit)
	{
	pgd_t *pgd;

	if (mm->context.asce_limit <= limit)
	return;
	__tlb_flush_mm(mm);
	while (mm->context.asce_limit > limit) {
	pgd = mm->pgd;
	switch (pgd_val(*pgd) & _REGION_ENTRY_TYPE_MASK) {
	case _REGION_ENTRY_TYPE_R2:
	mm->context.asce_limit = 1UL << 42;
	mm->context.asce_bits = _ASCE_TABLE_LENGTH \|
	_ASCE_USER_BITS \|
	_ASCE_TYPE_REGION3;
	break;
	case _REGION_ENTRY_TYPE_R3:
	mm->context.asce_limit = 1UL << 31;
	mm->context.asce_bits = _ASCE_TABLE_LENGTH \|
	_ASCE_USER_BITS \|
	_ASCE_TYPE_SEGMENT;
	break;
	default:
	BUG();
	}
	mm->pgd = (pgd_t ) (pgd_val(pgd) & _REGION_ENTRY_ORIGIN);
	mm->task_size = mm->context.asce_limit;
	crst_table_free(mm, (unsigned long *) pgd);
	}
	update_mm(mm, current);
	}
	#endif

	static inline unsigned int atomic_xor_bits(atomic_t *v, unsigned int bits)
	{
	unsigned int old, new;

	do {
	old = atomic_read(v);
	new = old ^ bits;
	} while (atomic_cmpxchg(v, old, new) != old);
	return new;
	}

	/*
	* page table entry allocation/free routines.
	*/
	#ifdef CONFIG_PGSTE
	static inline unsigned long page_table_alloc_pgste(struct mm_struct mm)
	{
	struct page *page;
	unsigned long *table;

	page = alloc_page(GFP_KERNEL\|__GFP_REPEAT);
	if (!page)
	return NULL;
	pgtable_page_ctor(page);
	atomic_set(&page->_mapcount, 3);
	table = (unsigned long *) page_to_phys(page);
	clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE/2);
	clear_table(table + PTRS_PER_PTE, 0, PAGE_SIZE/2);
	return table;
	}

	static inline void page_table_free_pgste(unsigned long *table)
	{
	struct page *page;

	page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
	pgtable_page_ctor(page);
	atomic_set(&page->_mapcount, -1);
	__free_page(page);
	}
	#endif

	unsigned long page_table_alloc(struct mm_struct mm)
	{
	struct page *page;
	unsigned long *table;
	unsigned int mask, bit;

	#ifdef CONFIG_PGSTE
	if (mm_has_pgste(mm))
	return page_table_alloc_pgste(mm);
	#endif
	/* Allocate fragments of a 4K page as 1K/2K page table */
	spin_lock_bh(&mm->context.list_lock);
	mask = FRAG_MASK;
	if (!list_empty(&mm->context.pgtable_list)) {
	page = list_first_entry(&mm->context.pgtable_list,
	struct page, lru);
	table = (unsigned long *) page_to_phys(page);
	mask = atomic_read(&page->_mapcount);
	mask = mask \| (mask >> 4);
	}
	if ((mask & FRAG_MASK) == FRAG_MASK) {
	spin_unlock_bh(&mm->context.list_lock);
	page = alloc_page(GFP_KERNEL\|__GFP_REPEAT);
	if (!page)
	return NULL;
	pgtable_page_ctor(page);
	atomic_set(&page->_mapcount, 1);
	table = (unsigned long *) page_to_phys(page);
	clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE);
	spin_lock_bh(&mm->context.list_lock);
	list_add(&page->lru, &mm->context.pgtable_list);
	} else {
	for (bit = 1; mask & bit; bit <<= 1)
	table += PTRS_PER_PTE;
	mask = atomic_xor_bits(&page->_mapcount, bit);
	if ((mask & FRAG_MASK) == FRAG_MASK)
	list_del(&page->lru);
	}
	spin_unlock_bh(&mm->context.list_lock);
	return table;
	}

	void page_table_free(struct mm_struct mm, unsigned long table)
	{
	struct page *page;
	unsigned int bit, mask;

	#ifdef CONFIG_PGSTE
	if (mm_has_pgste(mm))
	return page_table_free_pgste(table);
	#endif
	/* Free 1K/2K page table fragment of a 4K page */
	page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
	bit = 1 << ((__pa(table) & ~PAGE_MASK)/(PTRS_PER_PTE*sizeof(pte_t)));
	spin_lock_bh(&mm->context.list_lock);
	if ((atomic_read(&page->_mapcount) & FRAG_MASK) != FRAG_MASK)
	list_del(&page->lru);
	mask = atomic_xor_bits(&page->_mapcount, bit);
	if (mask & FRAG_MASK)
	list_add(&page->lru, &mm->context.pgtable_list);
	spin_unlock_bh(&mm->context.list_lock);
	if (mask == 0) {
	pgtable_page_dtor(page);
	atomic_set(&page->_mapcount, -1);
	__free_page(page);
	}
	}

	static void __page_table_free_rcu(void *table, unsigned bit)
	{
	struct page *page;

	#ifdef CONFIG_PGSTE
	if (bit == FRAG_MASK)
	return page_table_free_pgste(table);
	#endif
	/* Free 1K/2K page table fragment of a 4K page */
	page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
	if (atomic_xor_bits(&page->_mapcount, bit) == 0) {
	pgtable_page_dtor(page);
	atomic_set(&page->_mapcount, -1);
	__free_page(page);
	}
	}

	void page_table_free_rcu(struct mmu_gather tlb, unsigned long table)
	{
	struct mm_struct *mm;
	struct page *page;
	unsigned int bit, mask;

	mm = tlb->mm;
	#ifdef CONFIG_PGSTE
	if (mm_has_pgste(mm)) {
	table = (unsigned long *) (__pa(table) \| FRAG_MASK);
	tlb_remove_table(tlb, table);
	return;
	}
	#endif
	bit = 1 << ((__pa(table) & ~PAGE_MASK) / (PTRS_PER_PTE*sizeof(pte_t)));
	page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
	spin_lock_bh(&mm->context.list_lock);
	if ((atomic_read(&page->_mapcount) & FRAG_MASK) != FRAG_MASK)
	list_del(&page->lru);
	mask = atomic_xor_bits(&page->_mapcount, bit \| (bit << 4));
	if (mask & FRAG_MASK)
	list_add_tail(&page->lru, &mm->context.pgtable_list);
	spin_unlock_bh(&mm->context.list_lock);
	table = (unsigned long *) (__pa(table) \| (bit << 4));
	tlb_remove_table(tlb, table);
	}

	void __tlb_remove_table(void *_table)
	{
	const unsigned long mask = (FRAG_MASK << 4) \| FRAG_MASK;
	void table = (void )((unsigned long) _table & ~mask);
	unsigned type = (unsigned long) _table & mask;

	if (type)
	__page_table_free_rcu(table, type);
	else
	free_pages((unsigned long) table, ALLOC_ORDER);
	}

	static void tlb_remove_table_smp_sync(void *arg)
	{
	/* Simply deliver the interrupt */
	}

	static void tlb_remove_table_one(void *table)
	{
	/*
	* This isn't an RCU grace period and hence the page-tables cannot be
	* assumed to be actually RCU-freed.
	*
	* It is however sufficient for software page-table walkers that rely
	* on IRQ disabling. See the comment near struct mmu_table_batch.
	*/
	smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
	__tlb_remove_table(table);
	}

	static void tlb_remove_table_rcu(struct rcu_head *head)
	{
	struct mmu_table_batch *batch;
	int i;

	batch = container_of(head, struct mmu_table_batch, rcu);

	for (i = 0; i < batch->nr; i++)
	__tlb_remove_table(batch->tables[i]);

	free_page((unsigned long)batch);
	}

	void tlb_table_flush(struct mmu_gather *tlb)
	{
	struct mmu_table_batch **batch = &tlb->batch;

	if (*batch) {
	__tlb_flush_mm(tlb->mm);
	call_rcu_sched(&(*batch)->rcu, tlb_remove_table_rcu);
	*batch = NULL;
	}
	}

	void tlb_remove_table(struct mmu_gather tlb, void table)
	{
	struct mmu_table_batch **batch = &tlb->batch;

	if (*batch == NULL) {
	batch = (struct mmu_table_batch )
	__get_free_page(GFP_NOWAIT \| __GFP_NOWARN);
	if (*batch == NULL) {
	__tlb_flush_mm(tlb->mm);
	tlb_remove_table_one(table);
	return;
	}
	(*batch)->nr = 0;
	}
	(batch)->tables[(batch)->nr++] = table;
	if ((*batch)->nr == MAX_TABLE_BATCH)
	tlb_table_flush(tlb);
	}

	/*
	* switch on pgstes for its userspace process (for kvm)
	*/
	int s390_enable_sie(void)
	{
	struct task_struct *tsk = current;
	struct mm_struct mm, old_mm;

	/* Do we have switched amode? If no, we cannot do sie */
	if (user_mode == HOME_SPACE_MODE)
	return -EINVAL;

	/* Do we have pgstes? if yes, we are done */
	if (mm_has_pgste(tsk->mm))
	return 0;

	/* lets check if we are allowed to replace the mm */
	task_lock(tsk);
	if (!tsk->mm \|\| atomic_read(&tsk->mm->mm_users) > 1 \|\|
	#ifdef CONFIG_AIO
	!hlist_empty(&tsk->mm->ioctx_list) \|\|
	#endif
	tsk->mm != tsk->active_mm) {
	task_unlock(tsk);
	return -EINVAL;
	}
	task_unlock(tsk);

	/* we copy the mm and let dup_mm create the page tables with_pgstes */
	tsk->mm->context.alloc_pgste = 1;
	mm = dup_mm(tsk);
	tsk->mm->context.alloc_pgste = 0;
	if (!mm)
	return -ENOMEM;

	/* Now lets check again if something happened */
	task_lock(tsk);
	if (!tsk->mm \|\| atomic_read(&tsk->mm->mm_users) > 1 \|\|
	#ifdef CONFIG_AIO
	!hlist_empty(&tsk->mm->ioctx_list) \|\|
	#endif
	tsk->mm != tsk->active_mm) {
	mmput(mm);
	task_unlock(tsk);
	return -EINVAL;
	}

	/* ok, we are alone. No ptrace, no threads, etc. */
	old_mm = tsk->mm;
	tsk->mm = tsk->active_mm = mm;
	preempt_disable();
	update_mm(mm, tsk);
	atomic_inc(&mm->context.attach_count);
	atomic_dec(&old_mm->context.attach_count);
	cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
	preempt_enable();
	task_unlock(tsk);
	mmput(old_mm);
	return 0;
	}
	EXPORT_SYMBOL_GPL(s390_enable_sie);

	#if defined(CONFIG_DEBUG_PAGEALLOC) && defined(CONFIG_HIBERNATION)
	bool kernel_page_present(struct page *page)
	{
	unsigned long addr;
	int cc;

	addr = page_to_phys(page);
	asm volatile(
	" lra %1,0(%1)\n"
	" ipm %0\n"
	" srl %0,28"
	: "=d" (cc), "+a" (addr) : : "cc");
	return cc == 0;
	}
	#endif /* CONFIG_HIBERNATION && CONFIG_DEBUG_PAGEALLOC */