sparc64: implement get_user_pages_fast()

asflags-y := -ansi

asflags-y := -ansi

ccflags-y := -Werror

ccflags-y := -Werror

obj-$(CONFIG_SPARC64)   += ultra.o tlb.o tsb.o

obj-$(CONFIG_SPARC64)   += ultra.o tlb.o tsb.o gup.o

obj-y                   += fault_$(BITS).o

obj-y                   += fault_$(BITS).o

obj-y                   += init_$(BITS).o

obj-y                   += init_$(BITS).o

obj-$(CONFIG_SPARC32)   += loadmmu.o

obj-$(CONFIG_SPARC32)   += loadmmu.o

/*

 * Lockless get_user_pages_fast for sparc, cribbed from powerpc

 *

 * Copyright (C) 2008 Nick Piggin

 * 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);

	return 1;

}

static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,

		int write, struct page **pages, int *nr)

{

	unsigned long next;

	pud_t *pudp;

	pudp = pud_offset(&pgd, addr);

	do {

		pud_t pud = *pudp;

		next = pud_addr_end(addr, end);

		if (pud_none(pud))

			return 0;

		if (!gup_pmd_range(pud, addr, next, write, pages, nr))

			return 0;

	} while (pudp++, addr = next, addr != end);

	return 1;

}

int get_user_pages_fast(unsigned long start, int nr_pages, int write,

			struct page **pages)

{

	struct mm_struct *mm = current->mm;

	unsigned long addr, len, end;

	unsigned long next;

	pgd_t *pgdp;

	int nr = 0;

	start &= PAGE_MASK;

	addr = start;

	len = (unsigned long) nr_pages << PAGE_SHIFT;

	end = start + len;

	/*

	 * XXX: batch / limit 'nr', to avoid large irq off latency

	 * needs some instrumenting to determine the common sizes used by

	 * important workloads (eg. DB2), and whether limiting the batch size

	 * will decrease performance.

	 *

	 * It seems like we're in the clear for the moment. Direct-IO is

	 * the main guy that batches up lots of get_user_pages, and even

	 * they are limited to 64-at-a-time which is not so many.

	 */

	/*

	 * This doesn't prevent pagetable teardown, but does prevent

	 * the pagetables from being freed on sparc.

	 *

	 * So long as we atomically load page table pointers versus teardown,

	 * we can follow the address down to the the page and take a ref on it.

	 */

	local_irq_disable();

	pgdp = pgd_offset(mm, addr);

	do {

		pgd_t pgd = *pgdp;

		next = pgd_addr_end(addr, end);

		if (pgd_none(pgd))

			goto slow;

		if (!gup_pud_range(pgd, addr, next, write, pages, &nr))

			goto slow;

	} while (pgdp++, addr = next, addr != end);

	local_irq_enable();

	VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);

	return nr;

	{

		int ret;

slow:

		local_irq_enable();

		/* Try to get the remaining pages with get_user_pages */

		start += nr << PAGE_SHIFT;

		pages += nr;

		down_read(&mm->mmap_sem);

		ret = get_user_pages(current, mm, start,

			(end - start) >> PAGE_SHIFT, write, 0, pages, NULL);

		up_read(&mm->mmap_sem);

		/* Have to be a bit careful with return values */

		if (nr > 0) {

			if (ret < 0)

				ret = nr;

			else

				ret += nr;

		}

		return ret;

	}

}