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authorDavid S. Miller <davem@davemloft.net>2011-07-25 20:12:22 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2011-07-25 23:57:10 -0400
commitdf077ac4687500e02a273a628057ff5ab17dc19f (patch)
tree3a28c3e9f2f0f529caa5da4770111dc78db071ba
parent683d2fa672da5e3b4fe96f13c43eba32b068d64b (diff)
sparc64: implement get_user_pages_fast()
Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--arch/sparc/mm/Makefile2
-rw-r--r--arch/sparc/mm/gup.c181
2 files changed, 182 insertions, 1 deletions
diff --git a/arch/sparc/mm/Makefile b/arch/sparc/mm/Makefile
index 79836a7dd00c..e3cda21b5ee9 100644
--- a/arch/sparc/mm/Makefile
+++ b/arch/sparc/mm/Makefile
@@ -4,7 +4,7 @@
4asflags-y := -ansi 4asflags-y := -ansi
5ccflags-y := -Werror 5ccflags-y := -Werror
6 6
7obj-$(CONFIG_SPARC64) += ultra.o tlb.o tsb.o 7obj-$(CONFIG_SPARC64) += ultra.o tlb.o tsb.o gup.o
8obj-y += fault_$(BITS).o 8obj-y += fault_$(BITS).o
9obj-y += init_$(BITS).o 9obj-y += init_$(BITS).o
10obj-$(CONFIG_SPARC32) += loadmmu.o 10obj-$(CONFIG_SPARC32) += loadmmu.o
diff --git a/arch/sparc/mm/gup.c b/arch/sparc/mm/gup.c
new file mode 100644
index 000000000000..a986b5d05712
--- /dev/null
+++ b/arch/sparc/mm/gup.c
@@ -0,0 +1,181 @@
1/*
2 * Lockless get_user_pages_fast for sparc, cribbed from powerpc
3 *
4 * Copyright (C) 2008 Nick Piggin
5 * Copyright (C) 2008 Novell Inc.
6 */
7
8#include <linux/sched.h>
9#include <linux/mm.h>
10#include <linux/vmstat.h>
11#include <linux/pagemap.h>
12#include <linux/rwsem.h>
13#include <asm/pgtable.h>
14
15/*
16 * The performance critical leaf functions are made noinline otherwise gcc
17 * inlines everything into a single function which results in too much
18 * register pressure.
19 */
20static noinline int gup_pte_range(pmd_t pmd, unsigned long addr,
21 unsigned long end, int write, struct page **pages, int *nr)
22{
23 unsigned long mask, result;
24 pte_t *ptep;
25
26 if (tlb_type == hypervisor) {
27 result = _PAGE_PRESENT_4V|_PAGE_P_4V;
28 if (write)
29 result |= _PAGE_WRITE_4V;
30 } else {
31 result = _PAGE_PRESENT_4U|_PAGE_P_4U;
32 if (write)
33 result |= _PAGE_WRITE_4U;
34 }
35 mask = result | _PAGE_SPECIAL;
36
37 ptep = pte_offset_kernel(&pmd, addr);
38 do {
39 struct page *page, *head;
40 pte_t pte = *ptep;
41
42 if ((pte_val(pte) & mask) != result)
43 return 0;
44 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
45
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.
50 */
51 page = pte_page(pte);
52 head = compound_head(page);
53 if (!page_cache_get_speculative(head))
54 return 0;
55 if (unlikely(pte_val(pte) != pte_val(*ptep))) {
56 put_page(head);
57 return 0;
58 }
59
60 pages[*nr] = page;
61 (*nr)++;
62 } while (ptep++, addr += PAGE_SIZE, addr != end);
63
64 return 1;
65}
66
67static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
68 int write, struct page **pages, int *nr)
69{
70 unsigned long next;
71 pmd_t *pmdp;
72
73 pmdp = pmd_offset(&pud, addr);
74 do {
75 pmd_t pmd = *pmdp;
76
77 next = pmd_addr_end(addr, end);
78 if (pmd_none(pmd))
79 return 0;
80 if (!gup_pte_range(pmd, addr, next, write, pages, nr))
81 return 0;
82 } while (pmdp++, addr = next, addr != end);
83
84 return 1;
85}
86
87static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
88 int write, struct page **pages, int *nr)
89{
90 unsigned long next;
91 pud_t *pudp;
92
93 pudp = pud_offset(&pgd, addr);
94 do {
95 pud_t pud = *pudp;
96
97 next = pud_addr_end(addr, end);
98 if (pud_none(pud))
99 return 0;
100 if (!gup_pmd_range(pud, addr, next, write, pages, nr))
101 return 0;
102 } while (pudp++, addr = next, addr != end);
103
104 return 1;
105}
106
107int get_user_pages_fast(unsigned long start, int nr_pages, int write,
108 struct page **pages)
109{
110 struct mm_struct *mm = current->mm;
111 unsigned long addr, len, end;
112 unsigned long next;
113 pgd_t *pgdp;
114 int nr = 0;
115
116 start &= PAGE_MASK;
117 addr = start;
118 len = (unsigned long) nr_pages << PAGE_SHIFT;
119 end = start + len;
120
121 /*
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.
126 *
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.
130 */
131 /*
132 * This doesn't prevent pagetable teardown, but does prevent
133 * the pagetables from being freed on sparc.
134 *
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.
137 */
138 local_irq_disable();
139
140 pgdp = pgd_offset(mm, addr);
141 do {
142 pgd_t pgd = *pgdp;
143
144 next = pgd_addr_end(addr, end);
145 if (pgd_none(pgd))
146 goto slow;
147 if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
148 goto slow;
149 } while (pgdp++, addr = next, addr != end);
150
151 local_irq_enable();
152
153 VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);
154 return nr;
155
156 {
157 int ret;
158
159slow:
160 local_irq_enable();
161
162 /* Try to get the remaining pages with get_user_pages */
163 start += nr << PAGE_SHIFT;
164 pages += nr;
165
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);
170
171 /* Have to be a bit careful with return values */
172 if (nr > 0) {
173 if (ret < 0)
174 ret = nr;
175 else
176 ret += nr;
177 }
178
179 return ret;
180 }
181}