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-rw-r--r--arch/x86/Kconfig1
-rw-r--r--arch/x86/mm/Makefile1
-rw-r--r--arch/x86/mm/gup.c258
-rw-r--r--include/asm-x86/uaccess.h1
-rw-r--r--mm/Kconfig3
5 files changed, 264 insertions, 0 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 6b2debfabddc..6bdde845818e 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -22,6 +22,7 @@ config X86
22 select HAVE_IDE 22 select HAVE_IDE
23 select HAVE_OPROFILE 23 select HAVE_OPROFILE
24 select HAVE_IOREMAP_PROT 24 select HAVE_IOREMAP_PROT
25 select HAVE_GET_USER_PAGES_FAST
25 select HAVE_KPROBES 26 select HAVE_KPROBES
26 select ARCH_WANT_OPTIONAL_GPIOLIB if !X86_RDC321X 27 select ARCH_WANT_OPTIONAL_GPIOLIB if !X86_RDC321X
27 select HAVE_KRETPROBES 28 select HAVE_KRETPROBES
diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
index 1fbb844c3d7a..2977ea37791f 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -1,6 +1,7 @@
1obj-y := init_$(BITS).o fault.o ioremap.o extable.o pageattr.o mmap.o \ 1obj-y := init_$(BITS).o fault.o ioremap.o extable.o pageattr.o mmap.o \
2 pat.o pgtable.o 2 pat.o pgtable.o
3 3
4obj-$(CONFIG_HAVE_GET_USER_PAGES_FAST) += gup.o
4obj-$(CONFIG_X86_32) += pgtable_32.o 5obj-$(CONFIG_X86_32) += pgtable_32.o
5 6
6obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o 7obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c
new file mode 100644
index 000000000000..6f733121f32e
--- /dev/null
+++ b/arch/x86/mm/gup.c
@@ -0,0 +1,258 @@
1/*
2 * Lockless get_user_pages_fast for x86
3 *
4 * Copyright (C) 2008 Nick Piggin
5 * Copyright (C) 2008 Novell Inc.
6 */
7#include <linux/sched.h>
8#include <linux/mm.h>
9#include <linux/vmstat.h>
10#include <linux/highmem.h>
11
12#include <asm/pgtable.h>
13
14static inline pte_t gup_get_pte(pte_t *ptep)
15{
16#ifndef CONFIG_X86_PAE
17 return *ptep;
18#else
19 /*
20 * With get_user_pages_fast, we walk down the pagetables without taking
21 * any locks. For this we would like to load the pointers atoimcally,
22 * but that is not possible (without expensive cmpxchg8b) on PAE. What
23 * we do have is the guarantee that a pte will only either go from not
24 * present to present, or present to not present or both -- it will not
25 * switch to a completely different present page without a TLB flush in
26 * between; something that we are blocking by holding interrupts off.
27 *
28 * Setting ptes from not present to present goes:
29 * ptep->pte_high = h;
30 * smp_wmb();
31 * ptep->pte_low = l;
32 *
33 * And present to not present goes:
34 * ptep->pte_low = 0;
35 * smp_wmb();
36 * ptep->pte_high = 0;
37 *
38 * We must ensure here that the load of pte_low sees l iff pte_high
39 * sees h. We load pte_high *after* loading pte_low, which ensures we
40 * don't see an older value of pte_high. *Then* we recheck pte_low,
41 * which ensures that we haven't picked up a changed pte high. We might
42 * have got rubbish values from pte_low and pte_high, but we are
43 * guaranteed that pte_low will not have the present bit set *unless*
44 * it is 'l'. And get_user_pages_fast only operates on present ptes, so
45 * we're safe.
46 *
47 * gup_get_pte should not be used or copied outside gup.c without being
48 * very careful -- it does not atomically load the pte or anything that
49 * is likely to be useful for you.
50 */
51 pte_t pte;
52
53retry:
54 pte.pte_low = ptep->pte_low;
55 smp_rmb();
56 pte.pte_high = ptep->pte_high;
57 smp_rmb();
58 if (unlikely(pte.pte_low != ptep->pte_low))
59 goto retry;
60
61 return pte;
62#endif
63}
64
65/*
66 * The performance critical leaf functions are made noinline otherwise gcc
67 * inlines everything into a single function which results in too much
68 * register pressure.
69 */
70static noinline int gup_pte_range(pmd_t pmd, unsigned long addr,
71 unsigned long end, int write, struct page **pages, int *nr)
72{
73 unsigned long mask;
74 pte_t *ptep;
75
76 mask = _PAGE_PRESENT|_PAGE_USER;
77 if (write)
78 mask |= _PAGE_RW;
79
80 ptep = pte_offset_map(&pmd, addr);
81 do {
82 pte_t pte = gup_get_pte(ptep);
83 struct page *page;
84
85 if ((pte_val(pte) & (mask | _PAGE_SPECIAL)) != mask) {
86 pte_unmap(ptep);
87 return 0;
88 }
89 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
90 page = pte_page(pte);
91 get_page(page);
92 pages[*nr] = page;
93 (*nr)++;
94
95 } while (ptep++, addr += PAGE_SIZE, addr != end);
96 pte_unmap(ptep - 1);
97
98 return 1;
99}
100
101static inline void get_head_page_multiple(struct page *page, int nr)
102{
103 VM_BUG_ON(page != compound_head(page));
104 VM_BUG_ON(page_count(page) == 0);
105 atomic_add(nr, &page->_count);
106}
107
108static noinline int gup_huge_pmd(pmd_t pmd, unsigned long addr,
109 unsigned long end, int write, struct page **pages, int *nr)
110{
111 unsigned long mask;
112 pte_t pte = *(pte_t *)&pmd;
113 struct page *head, *page;
114 int refs;
115
116 mask = _PAGE_PRESENT|_PAGE_USER;
117 if (write)
118 mask |= _PAGE_RW;
119 if ((pte_val(pte) & mask) != mask)
120 return 0;
121 /* hugepages are never "special" */
122 VM_BUG_ON(pte_val(pte) & _PAGE_SPECIAL);
123 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
124
125 refs = 0;
126 head = pte_page(pte);
127 page = head + ((addr & ~HPAGE_MASK) >> PAGE_SHIFT);
128 do {
129 VM_BUG_ON(compound_head(page) != head);
130 pages[*nr] = page;
131 (*nr)++;
132 page++;
133 refs++;
134 } while (addr += PAGE_SIZE, addr != end);
135 get_head_page_multiple(head, refs);
136
137 return 1;
138}
139
140static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
141 int write, struct page **pages, int *nr)
142{
143 unsigned long next;
144 pmd_t *pmdp;
145
146 pmdp = pmd_offset(&pud, addr);
147 do {
148 pmd_t pmd = *pmdp;
149
150 next = pmd_addr_end(addr, end);
151 if (pmd_none(pmd))
152 return 0;
153 if (unlikely(pmd_large(pmd))) {
154 if (!gup_huge_pmd(pmd, addr, next, write, pages, nr))
155 return 0;
156 } else {
157 if (!gup_pte_range(pmd, addr, next, write, pages, nr))
158 return 0;
159 }
160 } while (pmdp++, addr = next, addr != end);
161
162 return 1;
163}
164
165static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
166 int write, struct page **pages, int *nr)
167{
168 unsigned long next;
169 pud_t *pudp;
170
171 pudp = pud_offset(&pgd, addr);
172 do {
173 pud_t pud = *pudp;
174
175 next = pud_addr_end(addr, end);
176 if (pud_none(pud))
177 return 0;
178 if (!gup_pmd_range(pud, addr, next, write, pages, nr))
179 return 0;
180 } while (pudp++, addr = next, addr != end);
181
182 return 1;
183}
184
185int get_user_pages_fast(unsigned long start, int nr_pages, int write,
186 struct page **pages)
187{
188 struct mm_struct *mm = current->mm;
189 unsigned long end = start + (nr_pages << PAGE_SHIFT);
190 unsigned long addr = start;
191 unsigned long next;
192 pgd_t *pgdp;
193 int nr = 0;
194
195 if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
196 start, nr_pages*PAGE_SIZE)))
197 goto slow_irqon;
198
199 /*
200 * XXX: batch / limit 'nr', to avoid large irq off latency
201 * needs some instrumenting to determine the common sizes used by
202 * important workloads (eg. DB2), and whether limiting the batch size
203 * will decrease performance.
204 *
205 * It seems like we're in the clear for the moment. Direct-IO is
206 * the main guy that batches up lots of get_user_pages, and even
207 * they are limited to 64-at-a-time which is not so many.
208 */
209 /*
210 * This doesn't prevent pagetable teardown, but does prevent
211 * the pagetables and pages from being freed on x86.
212 *
213 * So long as we atomically load page table pointers versus teardown
214 * (which we do on x86, with the above PAE exception), we can follow the
215 * address down to the the page and take a ref on it.
216 */
217 local_irq_disable();
218 pgdp = pgd_offset(mm, addr);
219 do {
220 pgd_t pgd = *pgdp;
221
222 next = pgd_addr_end(addr, end);
223 if (pgd_none(pgd))
224 goto slow;
225 if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
226 goto slow;
227 } while (pgdp++, addr = next, addr != end);
228 local_irq_enable();
229
230 VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);
231 return nr;
232
233 {
234 int ret;
235
236slow:
237 local_irq_enable();
238slow_irqon:
239 /* Try to get the remaining pages with get_user_pages */
240 start += nr << PAGE_SHIFT;
241 pages += nr;
242
243 down_read(&mm->mmap_sem);
244 ret = get_user_pages(current, mm, start,
245 (end - start) >> PAGE_SHIFT, write, 0, pages, NULL);
246 up_read(&mm->mmap_sem);
247
248 /* Have to be a bit careful with return values */
249 if (nr > 0) {
250 if (ret < 0)
251 ret = nr;
252 else
253 ret += nr;
254 }
255
256 return ret;
257 }
258}
diff --git a/include/asm-x86/uaccess.h b/include/asm-x86/uaccess.h
index f6fa4d841bbc..5f702d1d5218 100644
--- a/include/asm-x86/uaccess.h
+++ b/include/asm-x86/uaccess.h
@@ -451,3 +451,4 @@ extern struct movsl_mask {
451#endif 451#endif
452 452
453#endif 453#endif
454
diff --git a/mm/Kconfig b/mm/Kconfig
index aa799007a11b..efee5d379df4 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -77,6 +77,9 @@ config FLAT_NODE_MEM_MAP
77 def_bool y 77 def_bool y
78 depends on !SPARSEMEM 78 depends on !SPARSEMEM
79 79
80config HAVE_GET_USER_PAGES_FAST
81 bool
82
80# 83#
81# Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's 84# Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's
82# to represent different areas of memory. This variable allows 85# to represent different areas of memory. This variable allows