]>
Commit | Line | Data |
---|---|---|
ce0ad7f0 NP |
1 | /* |
2 | * Lockless get_user_pages_fast for powerpc | |
3 | * | |
4 | * Copyright (C) 2008 Nick Piggin | |
5 | * Copyright (C) 2008 Novell Inc. | |
6 | */ | |
7 | #undef DEBUG | |
8 | ||
9 | #include <linux/sched.h> | |
10 | #include <linux/mm.h> | |
11 | #include <linux/hugetlb.h> | |
12 | #include <linux/vmstat.h> | |
13 | #include <linux/pagemap.h> | |
14 | #include <linux/rwsem.h> | |
15 | #include <asm/pgtable.h> | |
16 | ||
9e5efaa9 BH |
17 | #ifdef __HAVE_ARCH_PTE_SPECIAL |
18 | ||
ce0ad7f0 NP |
19 | /* |
20 | * The performance critical leaf functions are made noinline otherwise gcc | |
21 | * inlines everything into a single function which results in too much | |
22 | * register pressure. | |
23 | */ | |
24 | static noinline int gup_pte_range(pmd_t pmd, unsigned long addr, | |
25 | unsigned long end, int write, struct page **pages, int *nr) | |
26 | { | |
27 | unsigned long mask, result; | |
28 | pte_t *ptep; | |
29 | ||
30 | result = _PAGE_PRESENT|_PAGE_USER; | |
31 | if (write) | |
32 | result |= _PAGE_RW; | |
33 | mask = result | _PAGE_SPECIAL; | |
34 | ||
35 | ptep = pte_offset_kernel(&pmd, addr); | |
36 | do { | |
37 | pte_t pte = *ptep; | |
38 | struct page *page; | |
39 | ||
40 | if ((pte_val(pte) & mask) != result) | |
41 | return 0; | |
42 | VM_BUG_ON(!pfn_valid(pte_pfn(pte))); | |
43 | page = pte_page(pte); | |
44 | if (!page_cache_get_speculative(page)) | |
45 | return 0; | |
f5ea64dc | 46 | if (unlikely(pte_val(pte) != pte_val(*ptep))) { |
ce0ad7f0 NP |
47 | put_page(page); |
48 | return 0; | |
49 | } | |
50 | pages[*nr] = page; | |
51 | (*nr)++; | |
52 | ||
53 | } while (ptep++, addr += PAGE_SIZE, addr != end); | |
54 | ||
55 | return 1; | |
56 | } | |
57 | ||
ce0ad7f0 NP |
58 | static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end, |
59 | int write, struct page **pages, int *nr) | |
60 | { | |
61 | unsigned long next; | |
62 | pmd_t *pmdp; | |
63 | ||
64 | pmdp = pmd_offset(&pud, addr); | |
65 | do { | |
66 | pmd_t pmd = *pmdp; | |
67 | ||
68 | next = pmd_addr_end(addr, end); | |
69 | if (pmd_none(pmd)) | |
70 | return 0; | |
a4fe3ce7 DG |
71 | if (is_hugepd(pmdp)) { |
72 | if (!gup_hugepd((hugepd_t *)pmdp, PMD_SHIFT, | |
73 | addr, next, write, pages, nr)) | |
74 | return 0; | |
75 | } else if (!gup_pte_range(pmd, addr, next, write, pages, nr)) | |
ce0ad7f0 NP |
76 | return 0; |
77 | } while (pmdp++, addr = next, addr != end); | |
78 | ||
79 | return 1; | |
80 | } | |
81 | ||
82 | static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end, | |
83 | int write, struct page **pages, int *nr) | |
84 | { | |
85 | unsigned long next; | |
86 | pud_t *pudp; | |
87 | ||
88 | pudp = pud_offset(&pgd, addr); | |
89 | do { | |
90 | pud_t pud = *pudp; | |
91 | ||
92 | next = pud_addr_end(addr, end); | |
93 | if (pud_none(pud)) | |
94 | return 0; | |
a4fe3ce7 DG |
95 | if (is_hugepd(pudp)) { |
96 | if (!gup_hugepd((hugepd_t *)pudp, PUD_SHIFT, | |
97 | addr, next, write, pages, nr)) | |
98 | return 0; | |
99 | } else if (!gup_pmd_range(pud, addr, next, write, pages, nr)) | |
ce0ad7f0 NP |
100 | return 0; |
101 | } while (pudp++, addr = next, addr != end); | |
102 | ||
103 | return 1; | |
104 | } | |
105 | ||
106 | int get_user_pages_fast(unsigned long start, int nr_pages, int write, | |
107 | struct page **pages) | |
108 | { | |
109 | struct mm_struct *mm = current->mm; | |
110 | unsigned long addr, len, end; | |
111 | unsigned long next; | |
112 | pgd_t *pgdp; | |
9e5efaa9 | 113 | int nr = 0; |
ce0ad7f0 | 114 | |
29e5fa59 | 115 | pr_devel("%s(%lx,%x,%s)\n", __func__, start, nr_pages, write ? "write" : "read"); |
ce0ad7f0 NP |
116 | |
117 | start &= PAGE_MASK; | |
118 | addr = start; | |
119 | len = (unsigned long) nr_pages << PAGE_SHIFT; | |
120 | end = start + len; | |
121 | ||
122 | if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ, | |
123 | start, len))) | |
124 | goto slow_irqon; | |
125 | ||
29e5fa59 | 126 | pr_devel(" aligned: %lx .. %lx\n", start, end); |
ce0ad7f0 | 127 | |
ce0ad7f0 NP |
128 | /* |
129 | * XXX: batch / limit 'nr', to avoid large irq off latency | |
130 | * needs some instrumenting to determine the common sizes used by | |
131 | * important workloads (eg. DB2), and whether limiting the batch size | |
132 | * will decrease performance. | |
133 | * | |
134 | * It seems like we're in the clear for the moment. Direct-IO is | |
135 | * the main guy that batches up lots of get_user_pages, and even | |
136 | * they are limited to 64-at-a-time which is not so many. | |
137 | */ | |
138 | /* | |
139 | * This doesn't prevent pagetable teardown, but does prevent | |
140 | * the pagetables from being freed on powerpc. | |
141 | * | |
142 | * So long as we atomically load page table pointers versus teardown, | |
143 | * we can follow the address down to the the page and take a ref on it. | |
144 | */ | |
145 | local_irq_disable(); | |
146 | ||
a4fe3ce7 DG |
147 | pgdp = pgd_offset(mm, addr); |
148 | do { | |
149 | pgd_t pgd = *pgdp; | |
150 | ||
151 | pr_devel(" %016lx: normal pgd %p\n", addr, | |
152 | (void *)pgd_val(pgd)); | |
153 | next = pgd_addr_end(addr, end); | |
154 | if (pgd_none(pgd)) | |
155 | goto slow; | |
156 | if (is_hugepd(pgdp)) { | |
157 | if (!gup_hugepd((hugepd_t *)pgdp, PGDIR_SHIFT, | |
158 | addr, next, write, pages, &nr)) | |
ce0ad7f0 | 159 | goto slow; |
a4fe3ce7 DG |
160 | } else if (!gup_pud_range(pgd, addr, next, write, pages, &nr)) |
161 | goto slow; | |
162 | } while (pgdp++, addr = next, addr != end); | |
163 | ||
ce0ad7f0 NP |
164 | local_irq_enable(); |
165 | ||
166 | VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT); | |
167 | return nr; | |
168 | ||
169 | { | |
170 | int ret; | |
171 | ||
172 | slow: | |
173 | local_irq_enable(); | |
174 | slow_irqon: | |
29e5fa59 | 175 | pr_devel(" slow path ! nr = %d\n", nr); |
ce0ad7f0 NP |
176 | |
177 | /* Try to get the remaining pages with get_user_pages */ | |
178 | start += nr << PAGE_SHIFT; | |
179 | pages += nr; | |
180 | ||
181 | down_read(&mm->mmap_sem); | |
182 | ret = get_user_pages(current, mm, start, | |
183 | (end - start) >> PAGE_SHIFT, write, 0, pages, NULL); | |
184 | up_read(&mm->mmap_sem); | |
185 | ||
186 | /* Have to be a bit careful with return values */ | |
187 | if (nr > 0) { | |
188 | if (ret < 0) | |
189 | ret = nr; | |
190 | else | |
191 | ret += nr; | |
192 | } | |
193 | ||
194 | return ret; | |
195 | } | |
196 | } | |
9e5efaa9 BH |
197 | |
198 | #endif /* __HAVE_ARCH_PTE_SPECIAL */ |