<commit_before>/*
 * Lockless get_user_pages_fast for sparc, cribbed from powerpc
 *
 * Copyright (C) 2008 <NAME>
 * Copyright (C) 2008 Novell Inc.
 */

#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/vmstat.h>
#include <linux/pagemap.h>
#include <linux/rwsem.h>
#include <asm/pgtable.h>

/*
 * The performance critical leaf functions are made noinline otherwise gcc
 * inlines everything into a single function which results in too much
 * register pressure.
 */
static noinline int gup_pte_range(pmd_t pmd, unsigned long addr,
		unsigned long end, int write, struct page **pages, int *nr)
{
	unsigned long mask, result;
	pte_t *ptep;

	if (tlb_type == hypervisor) {
		result = _PAGE_PRESENT_4V|_PAGE_P_4V;
		if (write)
			result |= _PAGE_WRITE_4V;
	} else {
		result = _PAGE_PRESENT_4U|_PAGE_P_4U;
		if (write)
			result |= _PAGE_WRITE_4U;
	}
	mask = result | _PAGE_SPECIAL;

	ptep = pte_offset_kernel(&pmd, addr);
	do {
		struct page *page, *head;
		pte_t pte = *ptep;

		if ((pte_val(pte) & mask) != result)
			return 0;
		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));

		/* The hugepage case is simplified on sparc64 because
		 * we encode the sub-page pfn offsets into the
		 * hugepage PTEs.  We could optimize this in the future
		 * use page_cache_add_speculative() for the hugepage case.
		 */
		page = pte_page(pte);
		head = compound_head(page);
		if (!page_cache_get_speculative(head))
			return 0;
		if (unlikely(pte_val(pte) != pte_val(*ptep))) {
			put_page(head);
			return 0;
		}

		pages[*nr] = page;
		(*nr)++;
	} while (ptep++, addr += PAGE_SIZE, addr != end);

	return 1;
}

static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
		int write, struct page **pages, int *nr)
{
	unsigned long next;
	pmd_t *pmdp;

	pmdp = pmd_offset(&pud, addr);
	do {
		pmd_t pmd = *pmdp;

		next = pmd_addr_end(addr, end);
		if (pmd_none(pmd))
			return 0;
		if (!gup_pte_range(pmd, addr, next, write, pages, nr))
			return 0;
	} while (pmdp++, addr = next, addr != end);
<commit_msg>sparc: gup_pte_range() support THP based tail recounting<commit_after>/*
 * Lockless get_user_pages_fast for sparc, cribbed from powerpc
 *
 * Copyright (C) 2008 <NAME>
 * Copyright (C) 2008 Novell Inc.
 */

#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/vmstat.h>
#include <linux/pagemap.h>
#include <linux/rwsem.h>
#include <asm/pgtable.h>

static inline void get_huge_page_tail(struct page *page)
{
	/*
	 * __split_huge_page_refcount() cannot run
	 * from under us.
	 */
	VM_BUG_ON(page_mapcount(page) < 0);
	VM_BUG_ON(atomic_read(&page->_count) != 0);
	atomic_inc(&page->_mapcount);
}

/*
 * The performance critical leaf functions are made noinline otherwise gcc
 * inlines everything into a single function which results in too much
 * register pressure.
 */
static noinline int gup_pte_range(pmd_t pmd, unsigned long addr,
		unsigned long end, int write, struct page **pages, int *nr)
{
	unsigned long mask, result;
	pte_t *ptep;

	if (tlb_type == hypervisor) {
		result = _PAGE_PRESENT_4V|_PAGE_P_4V;
		if (write)
			result |= _PAGE_WRITE_4V;
	} else {
		result = _PAGE_PRESENT_4U|_PAGE_P_4U;
		if (write)
			result |= _PAGE_WRITE_4U;
	}
	mask = result | _PAGE_SPECIAL;

	ptep = pte_offset_kernel(&pmd, addr);
	do {
		struct page *page, *head;
		pte_t pte = *ptep;

		if ((pte_val(pte) & mask) != result)
			return 0;
		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));

		/* The hugepage case is simplified on sparc64 because
		 * we encode the sub-page pfn offsets into the
		 * hugepage PTEs.  We could optimize this in the future
		 * use page_cache_add_speculative() for the hugepage case.
		 */
		page = pte_page(pte);
		head = compound_head(page);
		if (!page_cache_get_speculative(head))
			return 0;
		if (unlikely(pte_val(pte) != pte_val(*ptep))) {
			put_page(head);
			return 0;
		}
		if (head != page)
			get_huge_page_tail(page);

		pages[*nr] = page;
		(*nr)++;
	} while (ptep++, addr += PAGE_SIZE, addr != end);

	return 1;
}

static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
		int write, struct page **pages, int *nr)
{
	unsigned long next;
	pmd_t *pmdp;

	pmdp = pmd_offset(&pud, addr);
	do {
		pmd_t pmd = *pmdp;

		next = pmd_addr_end(addr, end);
		if (pmd_none(pmd))
			return 0;
		if (!gup_pte_range(pmd, addr, next, write, pages, nr))
			return 0;
	} while (pmdp++, addr = next, addr != end);

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