1 files changed, 225 insertions, 0 deletions

diff --git a/arch/s390/mm/gup.c b/arch/s390/mm/gup.c
new file mode 100644
index 000000000000..38e641cdd977
--- /dev/null
+++ b/arch/s390/mm/gup.c
@@ -0,0 +1,225 @@
+/*
+ *  Lockless get_user_pages_fast for s390
+ *
+ *  Copyright IBM Corp. 2010
+ *  Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
+ */
+#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 inline int gup_pte_range(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
+                unsigned long end, int write, struct page **pages, int *nr)
+{
+        unsigned long mask, result;
+        pte_t *ptep, pte;
+        struct page *page;
+
+        result = write ? 0 : _PAGE_RO;
+        mask = result | _PAGE_INVALID | _PAGE_SPECIAL;
+
+        ptep = ((pte_t *) pmd_deref(pmd)) + pte_index(addr);
+        do {
+                pte = *ptep;
+                barrier();
+                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 inline int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
+                unsigned long end, int write, struct page **pages, int *nr)
+{
+        unsigned long mask, result;
+        struct page *head, *page;
+        int refs;
+
+        result = write ? 0 : _SEGMENT_ENTRY_RO;
+        mask = result | _SEGMENT_ENTRY_INV;
+        if ((pmd_val(pmd) & mask) != result)
+                return 0;
+        VM_BUG_ON(!pfn_valid(pmd_val(pmd) >> PAGE_SHIFT));
+
+        refs = 0;
+        head = pmd_page(pmd);
+        page = head + ((addr & ~PMD_MASK) >> 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(pmd_val(pmd) != pmd_val(*pmdp))) {
+                *nr -= refs;
+                while (refs--)
+                        put_page(head);
+        }
+
+        return 1;
+}
+
+
+static inline int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr,
+                unsigned long end, int write, struct page **pages, int *nr)
+{
+        unsigned long next;
+        pmd_t *pmdp, pmd;
+
+        pmdp = (pmd_t *) pudp;
+#ifdef CONFIG_64BIT
+        if ((pud_val(pud) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R3)
+                pmdp = (pmd_t *) pud_deref(pud);
+        pmdp += pmd_index(addr);
+#endif
+        do {
+                pmd = *pmdp;
+                barrier();
+                next = pmd_addr_end(addr, end);
+                if (pmd_none(pmd))
+                        return 0;
+                if (unlikely(pmd_huge(pmd))) {
+                        if (!gup_huge_pmd(pmdp, pmd, addr, next,
+                                          write, pages, nr))
+                                return 0;
+                } else if (!gup_pte_range(pmdp, pmd, addr, next,
+                                          write, pages, nr))
+                        return 0;
+        } while (pmdp++, addr = next, addr != end);
+
+        return 1;
+}
+
+static inline int gup_pud_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr,
+                unsigned long end, int write, struct page **pages, int *nr)
+{
+        unsigned long next;
+        pud_t *pudp, pud;
+
+        pudp = (pud_t *) pgdp;
+#ifdef CONFIG_64BIT
+        if ((pgd_val(pgd) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R2)
+                pudp = (pud_t *) pgd_deref(pgd);
+        pudp += pud_index(addr);
+#endif
+        do {
+                pud = *pudp;
+                barrier();
+                next = pud_addr_end(addr, end);
+                if (pud_none(pud))
+                        return 0;
+                if (!gup_pmd_range(pudp, pud, addr, next, write, pages, nr))
+                        return 0;
+        } while (pudp++, addr = next, addr != end);
+
+        return 1;
+}
+
+/**
+ * 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, pgd;
+        int nr = 0;
+
+        start &= PAGE_MASK;
+        addr = start;
+        len = (unsigned long) nr_pages << PAGE_SHIFT;
+        end = start + len;
+        if (end < start)
+                goto slow_irqon;
+
+        /*
+         * local_irq_disable() doesn't prevent pagetable teardown, but does
+         * prevent the pagetables from being freed on s390.
+         *
+         * 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 = *pgdp;
+                barrier();
+                next = pgd_addr_end(addr, end);
+                if (pgd_none(pgd))
+                        goto slow;
+                if (!gup_pud_range(pgdp, 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:
+                /* 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;
+        }
+}