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 | ||
91807063 AA |
19 | static inline void get_huge_page_tail(struct page *page) |
20 | { | |
21 | /* | |
22 | * __split_huge_page_refcount() cannot run | |
23 | * from under us. | |
24 | */ | |
25 | VM_BUG_ON(atomic_read(&page->_count) < 0); | |
26 | atomic_inc(&page->_count); | |
27 | } | |
28 | ||
ce0ad7f0 NP |
29 | /* |
30 | * The performance critical leaf functions are made noinline otherwise gcc | |
31 | * inlines everything into a single function which results in too much | |
32 | * register pressure. | |
33 | */ | |
34 | static noinline int gup_pte_range(pmd_t pmd, unsigned long addr, | |
35 | unsigned long end, int write, struct page **pages, int *nr) | |
36 | { | |
37 | unsigned long mask, result; | |
38 | pte_t *ptep; | |
39 | ||
40 | result = _PAGE_PRESENT|_PAGE_USER; | |
41 | if (write) | |
42 | result |= _PAGE_RW; | |
43 | mask = result | _PAGE_SPECIAL; | |
44 | ||
45 | ptep = pte_offset_kernel(&pmd, addr); | |
46 | do { | |
47 | pte_t pte = *ptep; | |
48 | struct page *page; | |
49 | ||
50 | if ((pte_val(pte) & mask) != result) | |
51 | return 0; | |
52 | VM_BUG_ON(!pfn_valid(pte_pfn(pte))); | |
53 | page = pte_page(pte); | |
54 | if (!page_cache_get_speculative(page)) | |
55 | return 0; | |
f5ea64dc | 56 | if (unlikely(pte_val(pte) != pte_val(*ptep))) { |
ce0ad7f0 NP |
57 | put_page(page); |
58 | return 0; | |
59 | } | |
91807063 AA |
60 | if (PageTail(page)) |
61 | get_huge_page_tail(page); | |
ce0ad7f0 NP |
62 | pages[*nr] = page; |
63 | (*nr)++; | |
64 | ||
65 | } while (ptep++, addr += PAGE_SIZE, addr != end); | |
66 | ||
67 | return 1; | |
68 | } | |
69 | ||
ce0ad7f0 NP |
70 | static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end, |
71 | int write, struct page **pages, int *nr) | |
72 | { | |
73 | unsigned long next; | |
74 | pmd_t *pmdp; | |
75 | ||
76 | pmdp = pmd_offset(&pud, addr); | |
77 | do { | |
78 | pmd_t pmd = *pmdp; | |
79 | ||
80 | next = pmd_addr_end(addr, end); | |
81 | if (pmd_none(pmd)) | |
82 | return 0; | |
a4fe3ce7 DG |
83 | if (is_hugepd(pmdp)) { |
84 | if (!gup_hugepd((hugepd_t *)pmdp, PMD_SHIFT, | |
85 | addr, next, write, pages, nr)) | |
86 | return 0; | |
87 | } else if (!gup_pte_range(pmd, addr, next, write, pages, nr)) | |
ce0ad7f0 NP |
88 | return 0; |
89 | } while (pmdp++, addr = next, addr != end); | |
90 | ||
91 | return 1; | |
92 | } | |
93 | ||
94 | static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end, | |
95 | int write, struct page **pages, int *nr) | |
96 | { | |
97 | unsigned long next; | |
98 | pud_t *pudp; | |
99 | ||
100 | pudp = pud_offset(&pgd, addr); | |
101 | do { | |
102 | pud_t pud = *pudp; | |
103 | ||
104 | next = pud_addr_end(addr, end); | |
105 | if (pud_none(pud)) | |
106 | return 0; | |
a4fe3ce7 DG |
107 | if (is_hugepd(pudp)) { |
108 | if (!gup_hugepd((hugepd_t *)pudp, PUD_SHIFT, | |
109 | addr, next, write, pages, nr)) | |
110 | return 0; | |
111 | } else if (!gup_pmd_range(pud, addr, next, write, pages, nr)) | |
ce0ad7f0 NP |
112 | return 0; |
113 | } while (pudp++, addr = next, addr != end); | |
114 | ||
115 | return 1; | |
116 | } | |
117 | ||
118 | int get_user_pages_fast(unsigned long start, int nr_pages, int write, | |
119 | struct page **pages) | |
120 | { | |
121 | struct mm_struct *mm = current->mm; | |
122 | unsigned long addr, len, end; | |
123 | unsigned long next; | |
124 | pgd_t *pgdp; | |
9e5efaa9 | 125 | int nr = 0; |
ce0ad7f0 | 126 | |
29e5fa59 | 127 | pr_devel("%s(%lx,%x,%s)\n", __func__, start, nr_pages, write ? "write" : "read"); |
ce0ad7f0 NP |
128 | |
129 | start &= PAGE_MASK; | |
130 | addr = start; | |
131 | len = (unsigned long) nr_pages << PAGE_SHIFT; | |
132 | end = start + len; | |
133 | ||
134 | if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ, | |
135 | start, len))) | |
136 | goto slow_irqon; | |
137 | ||
29e5fa59 | 138 | pr_devel(" aligned: %lx .. %lx\n", start, end); |
ce0ad7f0 | 139 | |
ce0ad7f0 NP |
140 | /* |
141 | * XXX: batch / limit 'nr', to avoid large irq off latency | |
142 | * needs some instrumenting to determine the common sizes used by | |
143 | * important workloads (eg. DB2), and whether limiting the batch size | |
144 | * will decrease performance. | |
145 | * | |
146 | * It seems like we're in the clear for the moment. Direct-IO is | |
147 | * the main guy that batches up lots of get_user_pages, and even | |
148 | * they are limited to 64-at-a-time which is not so many. | |
149 | */ | |
150 | /* | |
151 | * This doesn't prevent pagetable teardown, but does prevent | |
152 | * the pagetables from being freed on powerpc. | |
153 | * | |
154 | * So long as we atomically load page table pointers versus teardown, | |
155 | * we can follow the address down to the the page and take a ref on it. | |
156 | */ | |
157 | local_irq_disable(); | |
158 | ||
a4fe3ce7 DG |
159 | pgdp = pgd_offset(mm, addr); |
160 | do { | |
161 | pgd_t pgd = *pgdp; | |
162 | ||
163 | pr_devel(" %016lx: normal pgd %p\n", addr, | |
164 | (void *)pgd_val(pgd)); | |
165 | next = pgd_addr_end(addr, end); | |
166 | if (pgd_none(pgd)) | |
167 | goto slow; | |
168 | if (is_hugepd(pgdp)) { | |
169 | if (!gup_hugepd((hugepd_t *)pgdp, PGDIR_SHIFT, | |
170 | addr, next, write, pages, &nr)) | |
ce0ad7f0 | 171 | goto slow; |
a4fe3ce7 DG |
172 | } else if (!gup_pud_range(pgd, addr, next, write, pages, &nr)) |
173 | goto slow; | |
174 | } while (pgdp++, addr = next, addr != end); | |
175 | ||
ce0ad7f0 NP |
176 | local_irq_enable(); |
177 | ||
178 | VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT); | |
179 | return nr; | |
180 | ||
181 | { | |
182 | int ret; | |
183 | ||
184 | slow: | |
185 | local_irq_enable(); | |
186 | slow_irqon: | |
29e5fa59 | 187 | pr_devel(" slow path ! nr = %d\n", nr); |
ce0ad7f0 NP |
188 | |
189 | /* Try to get the remaining pages with get_user_pages */ | |
190 | start += nr << PAGE_SHIFT; | |
191 | pages += nr; | |
192 | ||
193 | down_read(&mm->mmap_sem); | |
194 | ret = get_user_pages(current, mm, start, | |
195 | (end - start) >> PAGE_SHIFT, write, 0, pages, NULL); | |
196 | up_read(&mm->mmap_sem); | |
197 | ||
198 | /* Have to be a bit careful with return values */ | |
199 | if (nr > 0) { | |
200 | if (ret < 0) | |
201 | ret = nr; | |
202 | else | |
203 | ret += nr; | |
204 | } | |
205 | ||
206 | return ret; | |
207 | } | |
208 | } | |
9e5efaa9 BH |
209 | |
210 | #endif /* __HAVE_ARCH_PTE_SPECIAL */ |