Merge branch 'next/generic' into mips-for-linux-next

1 files changed, 315 insertions, 0 deletions

diff --git a/arch/mips/mm/gup.c b/arch/mips/mm/gup.c
new file mode 100644
index 000000000000..33aadbcf170b
--- /dev/null
+++ b/arch/mips/mm/gup.c
@@ -0,0 +1,315 @@
+/*
+ * Lockless get_user_pages_fast for MIPS
+ *
+ * Copyright (C) 2008 Nick Piggin
+ * Copyright (C) 2008 Novell Inc.
+ * Copyright (C) 2011 Ralf Baechle
+ */
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <linux/vmstat.h>
+#include <linux/highmem.h>
+#include <linux/swap.h>
+#include <linux/hugetlb.h>
+
+#include <asm/pgtable.h>
+
+static inline pte_t gup_get_pte(pte_t *ptep)
+{
+#if defined(CONFIG_64BIT_PHYS_ADDR) && defined(CONFIG_CPU_MIPS32)
+        pte_t pte;
+
+retry:
+        pte.pte_low = ptep->pte_low;
+        smp_rmb();
+        pte.pte_high = ptep->pte_high;
+        smp_rmb();
+        if (unlikely(pte.pte_low != ptep->pte_low))
+                goto retry;
+
+        return pte;
+#else
+        return ACCESS_ONCE(*ptep);
+#endif
+}
+
+static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
+                        int write, struct page **pages, int *nr)
+{
+        pte_t *ptep = pte_offset_map(&pmd, addr);
+        do {
+                pte_t pte = gup_get_pte(ptep);
+                struct page *page;
+
+                if (!pte_present(pte) ||
+                    pte_special(pte) || (write && !pte_write(pte))) {
+                        pte_unmap(ptep);
+                        return 0;
+                }
+                VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
+                page = pte_page(pte);
+                get_page(page);
+                SetPageReferenced(page);
+                pages[*nr] = page;
+                (*nr)++;
+
+        } while (ptep++, addr += PAGE_SIZE, addr != end);
+
+        pte_unmap(ptep - 1);
+        return 1;
+}
+
+static inline void get_head_page_multiple(struct page *page, int nr)
+{
+        VM_BUG_ON(page != compound_head(page));
+        VM_BUG_ON(page_count(page) == 0);
+        atomic_add(nr, &page->_count);
+        SetPageReferenced(page);
+}
+
+static int gup_huge_pmd(pmd_t pmd, unsigned long addr, unsigned long end,
+                        int write, struct page **pages, int *nr)
+{
+        pte_t pte = *(pte_t *)&pmd;
+        struct page *head, *page;
+        int refs;
+
+        if (write && !pte_write(pte))
+                return 0;
+        /* hugepages are never "special" */
+        VM_BUG_ON(pte_special(pte));
+        VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
+
+        refs = 0;
+        head = pte_page(pte);
+        page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
+        do {
+                VM_BUG_ON(compound_head(page) != head);
+                pages[*nr] = page;
+                if (PageTail(page))
+                        get_huge_page_tail(page);
+                (*nr)++;
+                page++;
+                refs++;
+        } while (addr += PAGE_SIZE, addr != end);
+
+        get_head_page_multiple(head, refs);
+        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);
+                /*
+                 * The pmd_trans_splitting() check below explains why
+                 * pmdp_splitting_flush has to flush the tlb, to stop
+                 * this gup-fast code from running while we set the
+                 * splitting bit in the pmd. Returning zero will take
+                 * the slow path that will call wait_split_huge_page()
+                 * if the pmd is still in splitting state. gup-fast
+                 * can't because it has irq disabled and
+                 * wait_split_huge_page() would never return as the
+                 * tlb flush IPI wouldn't run.
+                 */
+                if (pmd_none(pmd) || pmd_trans_splitting(pmd))
+                        return 0;
+                if (unlikely(pmd_huge(pmd))) {
+                        if (!gup_huge_pmd(pmd, 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_huge_pud(pud_t pud, unsigned long addr, unsigned long end,
+                        int write, struct page **pages, int *nr)
+{
+        pte_t pte = *(pte_t *)&pud;
+        struct page *head, *page;
+        int refs;
+
+        if (write && !pte_write(pte))
+                return 0;
+        /* hugepages are never "special" */
+        VM_BUG_ON(pte_special(pte));
+        VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
+
+        refs = 0;
+        head = pte_page(pte);
+        page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
+        do {
+                VM_BUG_ON(compound_head(page) != head);
+                pages[*nr] = page;
+                (*nr)++;
+                page++;
+                refs++;
+        } while (addr += PAGE_SIZE, addr != end);
+
+        get_head_page_multiple(head, refs);
+        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 (unlikely(pud_huge(pud))) {
+                        if (!gup_huge_pud(pud, 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;
+}
+
+/*
+ * Like get_user_pages_fast() except its IRQ-safe in that it won't fall
+ * back to the regular GUP.
+ */
+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;
+
+        start &= PAGE_MASK;
+        addr = start;
+        len = (unsigned long) nr_pages << PAGE_SHIFT;
+        end = start + len;
+        if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
+                                        (void __user *)start, len)))
+                return 0;
+
+        /*
+         * 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 and pages from being freed.
+         *
+         * So long as we atomically load page table pointers versus teardown,
+         * we can follow the address down to the page and take a ref on it.
+         */
+        local_irq_save(flags);
+        pgdp = pgd_offset(mm, addr);
+        do {
+                pgd_t pgd = *pgdp;
+
+                next = pgd_addr_end(addr, end);
+                if (pgd_none(pgd))
+                        break;
+                if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
+                        break;
+        } while (pgdp++, addr = next, addr != end);
+        local_irq_restore(flags);
+
+        return nr;
+}
+
+/**
+ * get_user_pages_fast() - pin user pages in memory
+ * @start:      starting user address
+ * @nr_pages:   number of pages from start to pin
+ * @write:      whether pages will be written to
+ * @pages:      array that receives pointers to the pages pinned.
+ *              Should be at least nr_pages long.
+ *
+ * Attempt to pin user pages in memory without taking mm->mmap_sem.
+ * If not successful, it will fall back to taking the lock and
+ * calling get_user_pages().
+ *
+ * Returns number of pages pinned. This may be fewer than the number
+ * requested. If nr_pages is 0 or negative, returns 0. If no pages
+ * were pinned, returns -errno.
+ */
+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 ret, nr = 0;
+
+        start &= PAGE_MASK;
+        addr = start;
+        len = (unsigned long) nr_pages << PAGE_SHIFT;
+
+        end = start + len;
+        if (end < start)
+                goto slow_irqon;
+
+        /* XXX: batch / limit 'nr' */
+        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;
+slow:
+        local_irq_enable();
+
+slow_irqon:
+        /* 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;
+}