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 | */ | |
70b50f94 AA |
25 | VM_BUG_ON(page_mapcount(page) < 0); |
26 | VM_BUG_ON(atomic_read(&page->_count) != 0); | |
27 | atomic_inc(&page->_mapcount); | |
91807063 AA |
28 | } |
29 | ||
ce0ad7f0 NP |
30 | /* |
31 | * The performance critical leaf functions are made noinline otherwise gcc | |
32 | * inlines everything into a single function which results in too much | |
33 | * register pressure. | |
34 | */ | |
35 | static noinline int gup_pte_range(pmd_t pmd, unsigned long addr, | |
36 | unsigned long end, int write, struct page **pages, int *nr) | |
37 | { | |
38 | unsigned long mask, result; | |
39 | pte_t *ptep; | |
40 | ||
41 | result = _PAGE_PRESENT|_PAGE_USER; | |
42 | if (write) | |
43 | result |= _PAGE_RW; | |
44 | mask = result | _PAGE_SPECIAL; | |
45 | ||
46 | ptep = pte_offset_kernel(&pmd, addr); | |
47 | do { | |
48 | pte_t pte = *ptep; | |
49 | struct page *page; | |
50 | ||
51 | if ((pte_val(pte) & mask) != result) | |
52 | return 0; | |
53 | VM_BUG_ON(!pfn_valid(pte_pfn(pte))); | |
54 | page = pte_page(pte); | |
55 | if (!page_cache_get_speculative(page)) | |
56 | return 0; | |
f5ea64dc | 57 | if (unlikely(pte_val(pte) != pte_val(*ptep))) { |
ce0ad7f0 NP |
58 | put_page(page); |
59 | return 0; | |
60 | } | |
91807063 AA |
61 | if (PageTail(page)) |
62 | get_huge_page_tail(page); | |
ce0ad7f0 NP |
63 | pages[*nr] = page; |
64 | (*nr)++; | |
65 | ||
66 | } while (ptep++, addr += PAGE_SIZE, addr != end); | |
67 | ||
68 | return 1; | |
69 | } | |
70 | ||
ce0ad7f0 NP |
71 | static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end, |
72 | int write, struct page **pages, int *nr) | |
73 | { | |
74 | unsigned long next; | |
75 | pmd_t *pmdp; | |
76 | ||
77 | pmdp = pmd_offset(&pud, addr); | |
78 | do { | |
79 | pmd_t pmd = *pmdp; | |
80 | ||
81 | next = pmd_addr_end(addr, end); | |
82 | if (pmd_none(pmd)) | |
83 | return 0; | |
a4fe3ce7 DG |
84 | if (is_hugepd(pmdp)) { |
85 | if (!gup_hugepd((hugepd_t *)pmdp, PMD_SHIFT, | |
86 | addr, next, write, pages, nr)) | |
87 | return 0; | |
88 | } else if (!gup_pte_range(pmd, addr, next, write, pages, nr)) | |
ce0ad7f0 NP |
89 | return 0; |
90 | } while (pmdp++, addr = next, addr != end); | |
91 | ||
92 | return 1; | |
93 | } | |
94 | ||
95 | static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end, | |
96 | int write, struct page **pages, int *nr) | |
97 | { | |
98 | unsigned long next; | |
99 | pud_t *pudp; | |
100 | ||
101 | pudp = pud_offset(&pgd, addr); | |
102 | do { | |
103 | pud_t pud = *pudp; | |
104 | ||
105 | next = pud_addr_end(addr, end); | |
106 | if (pud_none(pud)) | |
107 | return 0; | |
a4fe3ce7 DG |
108 | if (is_hugepd(pudp)) { |
109 | if (!gup_hugepd((hugepd_t *)pudp, PUD_SHIFT, | |
110 | addr, next, write, pages, nr)) | |
111 | return 0; | |
112 | } else if (!gup_pmd_range(pud, addr, next, write, pages, nr)) | |
ce0ad7f0 NP |
113 | return 0; |
114 | } while (pudp++, addr = next, addr != end); | |
115 | ||
116 | return 1; | |
117 | } | |
118 | ||
119 | int get_user_pages_fast(unsigned long start, int nr_pages, int write, | |
120 | struct page **pages) | |
121 | { | |
122 | struct mm_struct *mm = current->mm; | |
123 | unsigned long addr, len, end; | |
124 | unsigned long next; | |
125 | pgd_t *pgdp; | |
9e5efaa9 | 126 | int nr = 0; |
ce0ad7f0 | 127 | |
29e5fa59 | 128 | pr_devel("%s(%lx,%x,%s)\n", __func__, start, nr_pages, write ? "write" : "read"); |
ce0ad7f0 NP |
129 | |
130 | start &= PAGE_MASK; | |
131 | addr = start; | |
132 | len = (unsigned long) nr_pages << PAGE_SHIFT; | |
133 | end = start + len; | |
134 | ||
135 | if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ, | |
136 | start, len))) | |
137 | goto slow_irqon; | |
138 | ||
29e5fa59 | 139 | pr_devel(" aligned: %lx .. %lx\n", start, end); |
ce0ad7f0 | 140 | |
ce0ad7f0 NP |
141 | /* |
142 | * XXX: batch / limit 'nr', to avoid large irq off latency | |
143 | * needs some instrumenting to determine the common sizes used by | |
144 | * important workloads (eg. DB2), and whether limiting the batch size | |
145 | * will decrease performance. | |
146 | * | |
147 | * It seems like we're in the clear for the moment. Direct-IO is | |
148 | * the main guy that batches up lots of get_user_pages, and even | |
149 | * they are limited to 64-at-a-time which is not so many. | |
150 | */ | |
151 | /* | |
152 | * This doesn't prevent pagetable teardown, but does prevent | |
153 | * the pagetables from being freed on powerpc. | |
154 | * | |
155 | * So long as we atomically load page table pointers versus teardown, | |
156 | * we can follow the address down to the the page and take a ref on it. | |
157 | */ | |
158 | local_irq_disable(); | |
159 | ||
a4fe3ce7 DG |
160 | pgdp = pgd_offset(mm, addr); |
161 | do { | |
162 | pgd_t pgd = *pgdp; | |
163 | ||
164 | pr_devel(" %016lx: normal pgd %p\n", addr, | |
165 | (void *)pgd_val(pgd)); | |
166 | next = pgd_addr_end(addr, end); | |
167 | if (pgd_none(pgd)) | |
168 | goto slow; | |
169 | if (is_hugepd(pgdp)) { | |
170 | if (!gup_hugepd((hugepd_t *)pgdp, PGDIR_SHIFT, | |
171 | addr, next, write, pages, &nr)) | |
ce0ad7f0 | 172 | goto slow; |
a4fe3ce7 DG |
173 | } else if (!gup_pud_range(pgd, addr, next, write, pages, &nr)) |
174 | goto slow; | |
175 | } while (pgdp++, addr = next, addr != end); | |
176 | ||
ce0ad7f0 NP |
177 | local_irq_enable(); |
178 | ||
179 | VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT); | |
180 | return nr; | |
181 | ||
182 | { | |
183 | int ret; | |
184 | ||
185 | slow: | |
186 | local_irq_enable(); | |
187 | slow_irqon: | |
29e5fa59 | 188 | pr_devel(" slow path ! nr = %d\n", nr); |
ce0ad7f0 NP |
189 | |
190 | /* Try to get the remaining pages with get_user_pages */ | |
191 | start += nr << PAGE_SHIFT; | |
192 | pages += nr; | |
193 | ||
194 | down_read(&mm->mmap_sem); | |
195 | ret = get_user_pages(current, mm, start, | |
196 | (end - start) >> PAGE_SHIFT, write, 0, pages, NULL); | |
197 | up_read(&mm->mmap_sem); | |
198 | ||
199 | /* Have to be a bit careful with return values */ | |
200 | if (nr > 0) { | |
201 | if (ret < 0) | |
202 | ret = nr; | |
203 | else | |
204 | ret += nr; | |
205 | } | |
206 | ||
207 | return ret; | |
208 | } | |
209 | } | |
9e5efaa9 BH |
210 | |
211 | #endif /* __HAVE_ARCH_PTE_SPECIAL */ |