1 files changed, 235 insertions, 0 deletions
diff --git a/arch/powerpc/mm/gup.c b/arch/powerpc/mm/gup.c
new file mode 100644
index 00000000000..d8746684f60
--- /dev/null
+++ b/arch/powerpc/mm/gup.c
@@ -0,0 +1,235 @@
+/*
+ * 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>
+
+#ifdef __HAVE_ARCH_PTE_SPECIAL
+
+/*
+ * 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 = ACCESS_ONCE(*ptep);
+		struct page *page;
+		/*
+		 * Similar to the PMD case, NUMA hinting must take slow path
+		 */
+		if (pte_numa(pte))
+			return 0;
+
+		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_val(pte) != pte_val(*ptep))) {
+			put_page(page);
+			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 = ACCESS_ONCE(*pmdp);
+
+		next = pmd_addr_end(addr, end);
+		/*
+		 * If we find a splitting transparent hugepage we
+		 * return zero. That will result in taking the slow
+		 * path which will call wait_split_huge_page()
+		 * if the pmd is still in splitting state
+		 */
+		if (pmd_none(pmd) || pmd_trans_splitting(pmd))
+			return 0;
+		if (pmd_huge(pmd) || pmd_large(pmd)) {
+			/*
+			 * NUMA hinting faults need to be handled in the GUP
+			 * slowpath for accounting purposes and so that they
+			 * can be serialised against THP migration.
+			 */
+			if (pmd_numa(pmd))
+				return 0;
+
+			if (!gup_hugepte((pte_t *)pmdp, PMD_SIZE, addr, next,
+					 write, pages, nr))
+				return 0;
+		} else if (is_hugepd(pmdp)) {
+			if (!gup_hugepd((hugepd_t *)pmdp, PMD_SHIFT,
+					addr, next, write, pages, nr))
+				return 0;
+		} else 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 = ACCESS_ONCE(*pudp);
+
+		next = pud_addr_end(addr, end);
+		if (pud_none(pud))
+			return 0;
+		if (pud_huge(pud)) {
+			if (!gup_hugepte((pte_t *)pudp, PUD_SIZE, addr, next,
+					 write, pages, nr))
+				return 0;
+		} else if (is_hugepd(pudp)) {
+			if (!gup_hugepd((hugepd_t *)pudp, PUD_SHIFT,
+					addr, next, write, pages, nr))
+				return 0;
+		} else 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;
+	unsigned long flags;
+	pgd_t *pgdp;
+	int nr = 0;
+
+	pr_devel("%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)))
+		return 0;
+
+	pr_devel("  aligned: %lx .. %lx\n", start, end);
+
+	/*
+	 * 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_save(flags);
+
+	pgdp = pgd_offset(mm, addr);
+	do {
+		pgd_t pgd = ACCESS_ONCE(*pgdp);
+
+		pr_devel("  %016lx: normal pgd %p\n", addr,
+			 (void *)pgd_val(pgd));
+		next = pgd_addr_end(addr, end);
+		if (pgd_none(pgd))
+			break;
+		if (pgd_huge(pgd)) {
+			if (!gup_hugepte((pte_t *)pgdp, PGDIR_SIZE, addr, next,
+					 write, pages, &nr))
+				break;
+		} else if (is_hugepd(pgdp)) {
+			if (!gup_hugepd((hugepd_t *)pgdp, PGDIR_SHIFT,
+					addr, next, write, pages, &nr))
+				break;
+		} else if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
+			break;
+	} while (pgdp++, addr = next, addr != end);
+
+	local_irq_restore(flags);
+
+	return nr;
+}
+
+int get_user_pages_fast(unsigned long start, int nr_pages, int write,
+			struct page **pages)
+{
+	struct mm_struct *mm = current->mm;
+	int nr, ret;
+
+	start &= PAGE_MASK;
+	nr = __get_user_pages_fast(start, nr_pages, write, pages);
+	ret = nr;
+
+	if (nr < nr_pages) {
+		pr_devel("  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,
+				     nr_pages - nr, 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;
+}
+
+#endif /* __HAVE_ARCH_PTE_SPECIAL */