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80217147 MS |
1 | /* |
2 | * Lockless get_user_pages_fast for s390 | |
3 | * | |
4 | * Copyright IBM Corp. 2010 | |
5 | * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com> | |
6 | */ | |
7 | #include <linux/sched.h> | |
8 | #include <linux/mm.h> | |
9 | #include <linux/hugetlb.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 | */ | |
20 | static inline int gup_pte_range(pmd_t *pmdp, pmd_t pmd, unsigned long addr, | |
21 | unsigned long end, int write, struct page **pages, int *nr) | |
22 | { | |
fc897c95 | 23 | struct page *head, *page; |
25591b07 | 24 | unsigned long mask; |
80217147 | 25 | pte_t *ptep, pte; |
80217147 | 26 | |
e5098611 | 27 | mask = (write ? _PAGE_PROTECT : 0) | _PAGE_INVALID | _PAGE_SPECIAL; |
80217147 MS |
28 | |
29 | ptep = ((pte_t *) pmd_deref(pmd)) + pte_index(addr); | |
30 | do { | |
31 | pte = *ptep; | |
32 | barrier(); | |
ecf46abd GS |
33 | /* Similar to the PMD case, NUMA hinting must take slow path */ |
34 | if (pte_protnone(pte)) | |
35 | return 0; | |
25591b07 | 36 | if ((pte_val(pte) & mask) != 0) |
80217147 MS |
37 | return 0; |
38 | VM_BUG_ON(!pfn_valid(pte_pfn(pte))); | |
39 | page = pte_page(pte); | |
fc897c95 GS |
40 | head = compound_head(page); |
41 | if (!page_cache_get_speculative(head)) | |
80217147 MS |
42 | return 0; |
43 | if (unlikely(pte_val(pte) != pte_val(*ptep))) { | |
fc897c95 | 44 | put_page(head); |
80217147 MS |
45 | return 0; |
46 | } | |
fc897c95 | 47 | VM_BUG_ON_PAGE(compound_head(page) != head, page); |
80217147 MS |
48 | pages[*nr] = page; |
49 | (*nr)++; | |
50 | ||
51 | } while (ptep++, addr += PAGE_SIZE, addr != end); | |
52 | ||
53 | return 1; | |
54 | } | |
55 | ||
56 | static inline int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr, | |
57 | unsigned long end, int write, struct page **pages, int *nr) | |
58 | { | |
59 | unsigned long mask, result; | |
ddc58f27 | 60 | struct page *head, *page; |
80217147 MS |
61 | int refs; |
62 | ||
e5098611 MS |
63 | result = write ? 0 : _SEGMENT_ENTRY_PROTECT; |
64 | mask = result | _SEGMENT_ENTRY_INVALID; | |
80217147 MS |
65 | if ((pmd_val(pmd) & mask) != result) |
66 | return 0; | |
67 | VM_BUG_ON(!pfn_valid(pmd_val(pmd) >> PAGE_SHIFT)); | |
68 | ||
69 | refs = 0; | |
70 | head = pmd_page(pmd); | |
71 | page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT); | |
72 | do { | |
73 | VM_BUG_ON(compound_head(page) != head); | |
74 | pages[*nr] = page; | |
75 | (*nr)++; | |
76 | page++; | |
77 | refs++; | |
78 | } while (addr += PAGE_SIZE, addr != end); | |
79 | ||
80 | if (!page_cache_add_speculative(head, refs)) { | |
81 | *nr -= refs; | |
82 | return 0; | |
83 | } | |
84 | ||
85 | if (unlikely(pmd_val(pmd) != pmd_val(*pmdp))) { | |
86 | *nr -= refs; | |
87 | while (refs--) | |
88 | put_page(head); | |
0693bc9c AA |
89 | return 0; |
90 | } | |
91 | ||
80217147 MS |
92 | return 1; |
93 | } | |
94 | ||
95 | ||
96 | static inline int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr, | |
97 | unsigned long end, int write, struct page **pages, int *nr) | |
98 | { | |
99 | unsigned long next; | |
100 | pmd_t *pmdp, pmd; | |
101 | ||
102 | pmdp = (pmd_t *) pudp; | |
80217147 MS |
103 | if ((pud_val(pud) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R3) |
104 | pmdp = (pmd_t *) pud_deref(pud); | |
105 | pmdp += pmd_index(addr); | |
80217147 MS |
106 | do { |
107 | pmd = *pmdp; | |
108 | barrier(); | |
109 | next = pmd_addr_end(addr, end); | |
fecffad2 | 110 | if (pmd_none(pmd)) |
80217147 | 111 | return 0; |
156152f8 | 112 | if (unlikely(pmd_large(pmd))) { |
ecf46abd GS |
113 | /* |
114 | * NUMA hinting faults need to be handled in the GUP | |
115 | * slowpath for accounting purposes and so that they | |
116 | * can be serialised against THP migration. | |
117 | */ | |
118 | if (pmd_protnone(pmd)) | |
119 | return 0; | |
80217147 MS |
120 | if (!gup_huge_pmd(pmdp, pmd, addr, next, |
121 | write, pages, nr)) | |
122 | return 0; | |
123 | } else if (!gup_pte_range(pmdp, pmd, addr, next, | |
124 | write, pages, nr)) | |
125 | return 0; | |
126 | } while (pmdp++, addr = next, addr != end); | |
127 | ||
128 | return 1; | |
129 | } | |
130 | ||
131 | static inline int gup_pud_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr, | |
132 | unsigned long end, int write, struct page **pages, int *nr) | |
133 | { | |
134 | unsigned long next; | |
135 | pud_t *pudp, pud; | |
136 | ||
137 | pudp = (pud_t *) pgdp; | |
80217147 MS |
138 | if ((pgd_val(pgd) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R2) |
139 | pudp = (pud_t *) pgd_deref(pgd); | |
140 | pudp += pud_index(addr); | |
80217147 MS |
141 | do { |
142 | pud = *pudp; | |
143 | barrier(); | |
144 | next = pud_addr_end(addr, end); | |
145 | if (pud_none(pud)) | |
146 | return 0; | |
147 | if (!gup_pmd_range(pudp, pud, addr, next, write, pages, nr)) | |
148 | return 0; | |
149 | } while (pudp++, addr = next, addr != end); | |
150 | ||
151 | return 1; | |
152 | } | |
153 | ||
34cda992 GS |
154 | /* |
155 | * Like get_user_pages_fast() except its IRQ-safe in that it won't fall | |
156 | * back to the regular GUP. | |
157 | */ | |
158 | int __get_user_pages_fast(unsigned long start, int nr_pages, int write, | |
159 | struct page **pages) | |
160 | { | |
161 | struct mm_struct *mm = current->mm; | |
162 | unsigned long addr, len, end; | |
163 | unsigned long next, flags; | |
164 | pgd_t *pgdp, pgd; | |
165 | int nr = 0; | |
166 | ||
167 | start &= PAGE_MASK; | |
168 | addr = start; | |
169 | len = (unsigned long) nr_pages << PAGE_SHIFT; | |
170 | end = start + len; | |
eb0bf929 | 171 | if ((end <= start) || (end > TASK_SIZE)) |
34cda992 | 172 | return 0; |
01997bbc HC |
173 | /* |
174 | * local_irq_save() doesn't prevent pagetable teardown, but does | |
175 | * prevent the pagetables from being freed on s390. | |
176 | * | |
177 | * So long as we atomically load page table pointers versus teardown, | |
178 | * we can follow the address down to the the page and take a ref on it. | |
179 | */ | |
34cda992 GS |
180 | local_irq_save(flags); |
181 | pgdp = pgd_offset(mm, addr); | |
182 | do { | |
183 | pgd = *pgdp; | |
184 | barrier(); | |
185 | next = pgd_addr_end(addr, end); | |
186 | if (pgd_none(pgd)) | |
187 | break; | |
188 | if (!gup_pud_range(pgdp, pgd, addr, next, write, pages, &nr)) | |
189 | break; | |
190 | } while (pgdp++, addr = next, addr != end); | |
191 | local_irq_restore(flags); | |
192 | ||
193 | return nr; | |
194 | } | |
195 | ||
80217147 MS |
196 | /** |
197 | * get_user_pages_fast() - pin user pages in memory | |
198 | * @start: starting user address | |
199 | * @nr_pages: number of pages from start to pin | |
200 | * @write: whether pages will be written to | |
201 | * @pages: array that receives pointers to the pages pinned. | |
202 | * Should be at least nr_pages long. | |
203 | * | |
204 | * Attempt to pin user pages in memory without taking mm->mmap_sem. | |
205 | * If not successful, it will fall back to taking the lock and | |
206 | * calling get_user_pages(). | |
207 | * | |
208 | * Returns number of pages pinned. This may be fewer than the number | |
209 | * requested. If nr_pages is 0 or negative, returns 0. If no pages | |
210 | * were pinned, returns -errno. | |
211 | */ | |
212 | int get_user_pages_fast(unsigned long start, int nr_pages, int write, | |
213 | struct page **pages) | |
214 | { | |
01997bbc | 215 | int nr, ret; |
80217147 | 216 | |
40612351 | 217 | might_sleep(); |
80217147 | 218 | start &= PAGE_MASK; |
01997bbc HC |
219 | nr = __get_user_pages_fast(start, nr_pages, write, pages); |
220 | if (nr == nr_pages) | |
221 | return nr; | |
222 | ||
223 | /* Try to get the remaining pages with get_user_pages */ | |
224 | start += nr << PAGE_SHIFT; | |
225 | pages += nr; | |
d4edcf0d | 226 | ret = get_user_pages_unlocked(start, nr_pages - nr, write, 0, pages); |
01997bbc HC |
227 | /* Have to be a bit careful with return values */ |
228 | if (nr > 0) | |
229 | ret = (ret < 0) ? nr : ret + nr; | |
230 | return ret; | |
80217147 | 231 | } |