2 * Lockless get_user_pages_fast for sparc, cribbed from powerpc
4 * Copyright (C) 2008 Nick Piggin
5 * Copyright (C) 2008 Novell Inc.
8 #include <linux/sched.h>
10 #include <linux/vmstat.h>
11 #include <linux/pagemap.h>
12 #include <linux/rwsem.h>
13 #include <asm/pgtable.h>
16 * The performance critical leaf functions are made noinline otherwise gcc
17 * inlines everything into a single function which results in too much
20 static noinline int gup_pte_range(pmd_t pmd, unsigned long addr,
21 unsigned long end, int write, struct page **pages, int *nr)
23 unsigned long mask, result;
26 if (tlb_type == hypervisor) {
27 result = _PAGE_PRESENT_4V|_PAGE_P_4V;
29 result |= _PAGE_WRITE_4V;
31 result = _PAGE_PRESENT_4U|_PAGE_P_4U;
33 result |= _PAGE_WRITE_4U;
35 mask = result | _PAGE_SPECIAL;
37 ptep = pte_offset_kernel(&pmd, addr);
39 struct page *page, *head;
42 if ((pte_val(pte) & mask) != result)
44 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
46 /* The hugepage case is simplified on sparc64 because
47 * we encode the sub-page pfn offsets into the
48 * hugepage PTEs. We could optimize this in the future
49 * use page_cache_add_speculative() for the hugepage case.
52 head = compound_head(page);
53 if (!page_cache_get_speculative(head))
55 if (unlikely(pte_val(pte) != pte_val(*ptep))) {
62 } while (ptep++, addr += PAGE_SIZE, addr != end);
67 static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
68 int write, struct page **pages, int *nr)
73 pmdp = pmd_offset(&pud, addr);
77 next = pmd_addr_end(addr, end);
80 if (!gup_pte_range(pmd, addr, next, write, pages, nr))
82 } while (pmdp++, addr = next, addr != end);
87 static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
88 int write, struct page **pages, int *nr)
93 pudp = pud_offset(&pgd, addr);
97 next = pud_addr_end(addr, end);
100 if (!gup_pmd_range(pud, addr, next, write, pages, nr))
102 } while (pudp++, addr = next, addr != end);
107 int get_user_pages_fast(unsigned long start, int nr_pages, int write,
110 struct mm_struct *mm = current->mm;
111 unsigned long addr, len, end;
118 len = (unsigned long) nr_pages << PAGE_SHIFT;
122 * XXX: batch / limit 'nr', to avoid large irq off latency
123 * needs some instrumenting to determine the common sizes used by
124 * important workloads (eg. DB2), and whether limiting the batch size
125 * will decrease performance.
127 * It seems like we're in the clear for the moment. Direct-IO is
128 * the main guy that batches up lots of get_user_pages, and even
129 * they are limited to 64-at-a-time which is not so many.
132 * This doesn't prevent pagetable teardown, but does prevent
133 * the pagetables from being freed on sparc.
135 * So long as we atomically load page table pointers versus teardown,
136 * we can follow the address down to the the page and take a ref on it.
140 pgdp = pgd_offset(mm, addr);
144 next = pgd_addr_end(addr, end);
147 if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
149 } while (pgdp++, addr = next, addr != end);
153 VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);
162 /* Try to get the remaining pages with get_user_pages */
163 start += nr << PAGE_SHIFT;
166 down_read(&mm->mmap_sem);
167 ret = get_user_pages(current, mm, start,
168 (end - start) >> PAGE_SHIFT, write, 0, pages, NULL);
169 up_read(&mm->mmap_sem);
171 /* Have to be a bit careful with return values */