powerpc/mm: Lockless get_user_pages_fast() for 64-bit (v3) (ce0ad7f0) · Commits · e / devices / android_kernel_teracube_mt6765

arch/powerpc/Kconfig

+3 −0

Original line number	Diff line number	Diff line
		@@ -42,6 +42,9 @@ config GENERIC_HARDIRQS
		bool
		default y

		config HAVE_GET_USER_PAGES_FAST
		def_bool PPC64

		config HAVE_SETUP_PER_CPU_AREA
		def_bool PPC64

arch/powerpc/mm/Makefile

+2 −1

Original line number	Diff line number	Diff line
		@@ -12,7 +12,8 @@ obj-y := fault.o mem.o \
		mmu_context_$(CONFIG_WORD_SIZE).o
		hash-$(CONFIG_PPC_NATIVE) := hash_native_64.o
		obj-$(CONFIG_PPC64) += hash_utils_64.o \
		slb_low.o slb.o stab.o mmap.o $(hash-y)
		slb_low.o slb.o stab.o \
		gup.o mmap.o $(hash-y)
		obj-$(CONFIG_PPC_STD_MMU_32) += ppc_mmu_32.o
		obj-$(CONFIG_PPC_STD_MMU) += hash_low_$(CONFIG_WORD_SIZE).o \
		tlb_$(CONFIG_WORD_SIZE).o

arch/powerpc/mm/gup.c

0 → 100644

+280 −0

Original line number	Diff line number	Diff line
		/*
		* Lockless get_user_pages_fast for powerpc
		*
		* Copyright (C) 2008 Nick Piggin
		* Copyright (C) 2008 Novell Inc.
		*/
		#undef DEBUG

		#include <linux/sched.h>
		#include <linux/mm.h>
		#include <linux/hugetlb.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;

		result = _PAGE_PRESENT\|_PAGE_USER;
		if (write)
		result \|= _PAGE_RW;
		mask = result \| _PAGE_SPECIAL;

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

		if ((pte_val(pte) & mask) != result)
		return 0;
		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
		page = pte_page(pte);
		if (!page_cache_get_speculative(page))
		return 0;
		if (unlikely(pte != *ptep)) {
		put_page(page);
		return 0;
		}
		pages[*nr] = page;
		(*nr)++;

		} while (ptep++, addr += PAGE_SIZE, addr != end);

		return 1;
		}

		#ifdef CONFIG_HUGETLB_PAGE
		static noinline int gup_huge_pte(pte_t ptep, struct hstate hstate,
		unsigned long *addr, unsigned long end,
		int write, struct page *pages, int nr)
		{
		unsigned long mask;
		unsigned long pte_end;
		struct page head, page;
		pte_t pte;
		int refs;

		pte_end = (*addr + huge_page_size(hstate)) & huge_page_mask(hstate);
		if (pte_end < end)
		end = pte_end;

		pte = *ptep;
		mask = _PAGE_PRESENT\|_PAGE_USER;
		if (write)
		mask \|= _PAGE_RW;
		if ((pte_val(pte) & mask) != mask)
		return 0;
		/* hugepages are never "special" */
		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));

		refs = 0;
		head = pte_page(pte);
		page = head + ((*addr & ~huge_page_mask(hstate)) >> PAGE_SHIFT);
		do {
		VM_BUG_ON(compound_head(page) != head);
		pages[*nr] = page;
		(*nr)++;
		page++;
		refs++;
		} while (addr += PAGE_SIZE, addr != end);

		if (!page_cache_add_speculative(head, refs)) {
		*nr -= refs;
		return 0;
		}
		if (unlikely(pte != *ptep)) {
		/* Could be optimized better */
		while (*nr) {
		put_page(page);
		(*nr)--;
		}
		}

		return 1;
		}
		#endif /* CONFIG_HUGETLB_PAGE */

		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 psize, nr = 0;
		unsigned int shift;

		pr_debug("%s(%lx,%x,%s)\n", __func__, start, nr_pages, write ? "write" : "read");

		start &= PAGE_MASK;
		addr = start;
		len = (unsigned long) nr_pages << PAGE_SHIFT;
		end = start + len;

		if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
		start, len)))
		goto slow_irqon;

		pr_debug(" aligned: %lx .. %lx\n", start, end);

		#ifdef CONFIG_HUGETLB_PAGE
		/* We bail out on slice boundary crossing when hugetlb is
		* enabled in order to not have to deal with two different
		* page table formats
		*/
		if (addr < SLICE_LOW_TOP) {
		if (end > SLICE_LOW_TOP)
		goto slow_irqon;

		if (unlikely(GET_LOW_SLICE_INDEX(addr) !=
		GET_LOW_SLICE_INDEX(end - 1)))
		goto slow_irqon;
		} else {
		if (unlikely(GET_HIGH_SLICE_INDEX(addr) !=
		GET_HIGH_SLICE_INDEX(end - 1)))
		goto slow_irqon;
		}
		#endif /* CONFIG_HUGETLB_PAGE */

		/*
		* 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 powerpc.
		*
		* 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();

		psize = get_slice_psize(mm, addr);
		shift = mmu_psize_defs[psize].shift;

		#ifdef CONFIG_HUGETLB_PAGE
		if (unlikely(mmu_huge_psizes[psize])) {
		pte_t *ptep;
		unsigned long a = addr;
		unsigned long sz = ((1UL) << shift);
		struct hstate *hstate = size_to_hstate(sz);

		BUG_ON(!hstate);
		/*
		* XXX: could be optimized to avoid hstate
		* lookup entirely (just use shift)
		*/

		do {
		VM_BUG_ON(shift != mmu_psize_defs[get_slice_psize(mm, a)].shift);
		ptep = huge_pte_offset(mm, a);
		pr_debug(" %016lx: huge ptep %p\n", a, ptep);
		if (!ptep \|\| !gup_huge_pte(ptep, hstate, &a, end, write, pages,
		&nr))
		goto slow;
		} while (a != end);
		} else
		#endif /* CONFIG_HUGETLB_PAGE */
		{
		pgdp = pgd_offset(mm, addr);
		do {
		pgd_t pgd = *pgdp;

		VM_BUG_ON(shift != mmu_psize_defs[get_slice_psize(mm, addr)].shift);
		pr_debug(" %016lx: normal pgd %p\n", addr, (void *)pgd);
		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();
		slow_irqon:
		pr_debug(" slow path ! nr = %d\n", nr);

		/* 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;
		}
		}

include/asm-powerpc/pgtable-ppc64.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -461,6 +461,8 @@ void pgtable_cache_init(void);
		return pt;
		}

		pte_t huge_pte_offset(struct mm_struct mm, unsigned long address);

		#endif /* __ASSEMBLY__ */

		#endif /* _ASM_POWERPC_PGTABLE_PPC64_H_ */

include/linux/pagemap.h

+23 −0

Original line number	Diff line number	Diff line
		@@ -143,6 +143,29 @@ static inline int page_cache_get_speculative(struct page *page)
		return 1;
		}

		/*
		* Same as above, but add instead of inc (could just be merged)
		*/
		static inline int page_cache_add_speculative(struct page *page, int count)
		{
		VM_BUG_ON(in_interrupt());

		#if !defined(CONFIG_SMP) && defined(CONFIG_CLASSIC_RCU)
		# ifdef CONFIG_PREEMPT
		VM_BUG_ON(!in_atomic());
		# endif
		VM_BUG_ON(page_count(page) == 0);
		atomic_add(count, &page->_count);

		#else
		if (unlikely(!atomic_add_unless(&page->_count, count, 0)))
		return 0;
		#endif
		VM_BUG_ON(PageCompound(page) && page != compound_head(page));

		return 1;
		}

		static inline int page_freeze_refs(struct page *page, int count)
		{
		return likely(atomic_cmpxchg(&page->_count, count, 0) == count);