Loading...
1/*
2 * Lockless get_user_pages_fast for MIPS
3 *
4 * Copyright (C) 2008 Nick Piggin
5 * Copyright (C) 2008 Novell Inc.
6 * Copyright (C) 2011 Ralf Baechle
7 */
8#include <linux/sched.h>
9#include <linux/mm.h>
10#include <linux/vmstat.h>
11#include <linux/highmem.h>
12#include <linux/swap.h>
13#include <linux/hugetlb.h>
14
15#include <asm/cpu-features.h>
16#include <asm/pgtable.h>
17
18static inline pte_t gup_get_pte(pte_t *ptep)
19{
20#if defined(CONFIG_PHYS_ADDR_T_64BIT) && defined(CONFIG_CPU_MIPS32)
21 pte_t pte;
22
23retry:
24 pte.pte_low = ptep->pte_low;
25 smp_rmb();
26 pte.pte_high = ptep->pte_high;
27 smp_rmb();
28 if (unlikely(pte.pte_low != ptep->pte_low))
29 goto retry;
30
31 return pte;
32#else
33 return READ_ONCE(*ptep);
34#endif
35}
36
37static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
38 int write, struct page **pages, int *nr)
39{
40 pte_t *ptep = pte_offset_map(&pmd, addr);
41 do {
42 pte_t pte = gup_get_pte(ptep);
43 struct page *page;
44
45 if (!pte_present(pte) ||
46 pte_special(pte) || (write && !pte_write(pte))) {
47 pte_unmap(ptep);
48 return 0;
49 }
50 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
51 page = pte_page(pte);
52 get_page(page);
53 SetPageReferenced(page);
54 pages[*nr] = page;
55 (*nr)++;
56
57 } while (ptep++, addr += PAGE_SIZE, addr != end);
58
59 pte_unmap(ptep - 1);
60 return 1;
61}
62
63static inline void get_head_page_multiple(struct page *page, int nr)
64{
65 VM_BUG_ON(page != compound_head(page));
66 VM_BUG_ON(page_count(page) == 0);
67 page_ref_add(page, nr);
68 SetPageReferenced(page);
69}
70
71static int gup_huge_pmd(pmd_t pmd, unsigned long addr, unsigned long end,
72 int write, struct page **pages, int *nr)
73{
74 pte_t pte = *(pte_t *)&pmd;
75 struct page *head, *page;
76 int refs;
77
78 if (write && !pte_write(pte))
79 return 0;
80 /* hugepages are never "special" */
81 VM_BUG_ON(pte_special(pte));
82 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
83
84 refs = 0;
85 head = pte_page(pte);
86 page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
87 do {
88 VM_BUG_ON(compound_head(page) != head);
89 pages[*nr] = page;
90 (*nr)++;
91 page++;
92 refs++;
93 } while (addr += PAGE_SIZE, addr != end);
94
95 get_head_page_multiple(head, refs);
96 return 1;
97}
98
99static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
100 int write, struct page **pages, int *nr)
101{
102 unsigned long next;
103 pmd_t *pmdp;
104
105 pmdp = pmd_offset(&pud, addr);
106 do {
107 pmd_t pmd = *pmdp;
108
109 next = pmd_addr_end(addr, end);
110 if (pmd_none(pmd))
111 return 0;
112 if (unlikely(pmd_huge(pmd))) {
113 if (!gup_huge_pmd(pmd, addr, next, write, pages,nr))
114 return 0;
115 } else {
116 if (!gup_pte_range(pmd, addr, next, write, pages,nr))
117 return 0;
118 }
119 } while (pmdp++, addr = next, addr != end);
120
121 return 1;
122}
123
124static int gup_huge_pud(pud_t pud, unsigned long addr, unsigned long end,
125 int write, struct page **pages, int *nr)
126{
127 pte_t pte = *(pte_t *)&pud;
128 struct page *head, *page;
129 int refs;
130
131 if (write && !pte_write(pte))
132 return 0;
133 /* hugepages are never "special" */
134 VM_BUG_ON(pte_special(pte));
135 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
136
137 refs = 0;
138 head = pte_page(pte);
139 page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
140 do {
141 VM_BUG_ON(compound_head(page) != head);
142 pages[*nr] = page;
143 (*nr)++;
144 page++;
145 refs++;
146 } while (addr += PAGE_SIZE, addr != end);
147
148 get_head_page_multiple(head, refs);
149 return 1;
150}
151
152static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
153 int write, struct page **pages, int *nr)
154{
155 unsigned long next;
156 pud_t *pudp;
157
158 pudp = pud_offset(&pgd, addr);
159 do {
160 pud_t pud = *pudp;
161
162 next = pud_addr_end(addr, end);
163 if (pud_none(pud))
164 return 0;
165 if (unlikely(pud_huge(pud))) {
166 if (!gup_huge_pud(pud, addr, next, write, pages,nr))
167 return 0;
168 } else {
169 if (!gup_pmd_range(pud, addr, next, write, pages,nr))
170 return 0;
171 }
172 } while (pudp++, addr = next, addr != end);
173
174 return 1;
175}
176
177/*
178 * Like get_user_pages_fast() except its IRQ-safe in that it won't fall
179 * back to the regular GUP.
180 */
181int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
182 struct page **pages)
183{
184 struct mm_struct *mm = current->mm;
185 unsigned long addr, len, end;
186 unsigned long next;
187 unsigned long flags;
188 pgd_t *pgdp;
189 int nr = 0;
190
191 start &= PAGE_MASK;
192 addr = start;
193 len = (unsigned long) nr_pages << PAGE_SHIFT;
194 end = start + len;
195 if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
196 (void __user *)start, len)))
197 return 0;
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
203 * size 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.
212 *
213 * So long as we atomically load page table pointers versus teardown,
214 * we can follow the address down to the page and take a ref on it.
215 */
216 local_irq_save(flags);
217 pgdp = pgd_offset(mm, addr);
218 do {
219 pgd_t pgd = *pgdp;
220
221 next = pgd_addr_end(addr, end);
222 if (pgd_none(pgd))
223 break;
224 if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
225 break;
226 } while (pgdp++, addr = next, addr != end);
227 local_irq_restore(flags);
228
229 return nr;
230}
231
232/**
233 * get_user_pages_fast() - pin user pages in memory
234 * @start: starting user address
235 * @nr_pages: number of pages from start to pin
236 * @write: whether pages will be written to
237 * @pages: array that receives pointers to the pages pinned.
238 * Should be at least nr_pages long.
239 *
240 * Attempt to pin user pages in memory without taking mm->mmap_sem.
241 * If not successful, it will fall back to taking the lock and
242 * calling get_user_pages().
243 *
244 * Returns number of pages pinned. This may be fewer than the number
245 * requested. If nr_pages is 0 or negative, returns 0. If no pages
246 * were pinned, returns -errno.
247 */
248int get_user_pages_fast(unsigned long start, int nr_pages, int write,
249 struct page **pages)
250{
251 struct mm_struct *mm = current->mm;
252 unsigned long addr, len, end;
253 unsigned long next;
254 pgd_t *pgdp;
255 int ret, nr = 0;
256
257 start &= PAGE_MASK;
258 addr = start;
259 len = (unsigned long) nr_pages << PAGE_SHIFT;
260
261 end = start + len;
262 if (end < start || cpu_has_dc_aliases)
263 goto slow_irqon;
264
265 /* XXX: batch / limit 'nr' */
266 local_irq_disable();
267 pgdp = pgd_offset(mm, addr);
268 do {
269 pgd_t pgd = *pgdp;
270
271 next = pgd_addr_end(addr, end);
272 if (pgd_none(pgd))
273 goto slow;
274 if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
275 goto slow;
276 } while (pgdp++, addr = next, addr != end);
277 local_irq_enable();
278
279 VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);
280 return nr;
281slow:
282 local_irq_enable();
283
284slow_irqon:
285 /* Try to get the remaining pages with get_user_pages */
286 start += nr << PAGE_SHIFT;
287 pages += nr;
288
289 ret = get_user_pages_unlocked(start, (end - start) >> PAGE_SHIFT,
290 pages, write ? FOLL_WRITE : 0);
291
292 /* Have to be a bit careful with return values */
293 if (nr > 0) {
294 if (ret < 0)
295 ret = nr;
296 else
297 ret += nr;
298 }
299 return ret;
300}
1/*
2 * Lockless get_user_pages_fast for MIPS
3 *
4 * Copyright (C) 2008 Nick Piggin
5 * Copyright (C) 2008 Novell Inc.
6 * Copyright (C) 2011 Ralf Baechle
7 */
8#include <linux/sched.h>
9#include <linux/mm.h>
10#include <linux/vmstat.h>
11#include <linux/highmem.h>
12#include <linux/swap.h>
13#include <linux/hugetlb.h>
14
15#include <asm/cpu-features.h>
16#include <asm/pgtable.h>
17
18static inline pte_t gup_get_pte(pte_t *ptep)
19{
20#if defined(CONFIG_64BIT_PHYS_ADDR) && defined(CONFIG_CPU_MIPS32)
21 pte_t pte;
22
23retry:
24 pte.pte_low = ptep->pte_low;
25 smp_rmb();
26 pte.pte_high = ptep->pte_high;
27 smp_rmb();
28 if (unlikely(pte.pte_low != ptep->pte_low))
29 goto retry;
30
31 return pte;
32#else
33 return ACCESS_ONCE(*ptep);
34#endif
35}
36
37static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
38 int write, struct page **pages, int *nr)
39{
40 pte_t *ptep = pte_offset_map(&pmd, addr);
41 do {
42 pte_t pte = gup_get_pte(ptep);
43 struct page *page;
44
45 if (!pte_present(pte) ||
46 pte_special(pte) || (write && !pte_write(pte))) {
47 pte_unmap(ptep);
48 return 0;
49 }
50 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
51 page = pte_page(pte);
52 get_page(page);
53 SetPageReferenced(page);
54 pages[*nr] = page;
55 (*nr)++;
56
57 } while (ptep++, addr += PAGE_SIZE, addr != end);
58
59 pte_unmap(ptep - 1);
60 return 1;
61}
62
63static inline void get_head_page_multiple(struct page *page, int nr)
64{
65 VM_BUG_ON(page != compound_head(page));
66 VM_BUG_ON(page_count(page) == 0);
67 atomic_add(nr, &page->_count);
68 SetPageReferenced(page);
69}
70
71static int gup_huge_pmd(pmd_t pmd, unsigned long addr, unsigned long end,
72 int write, struct page **pages, int *nr)
73{
74 pte_t pte = *(pte_t *)&pmd;
75 struct page *head, *page;
76 int refs;
77
78 if (write && !pte_write(pte))
79 return 0;
80 /* hugepages are never "special" */
81 VM_BUG_ON(pte_special(pte));
82 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
83
84 refs = 0;
85 head = pte_page(pte);
86 page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
87 do {
88 VM_BUG_ON(compound_head(page) != head);
89 pages[*nr] = page;
90 if (PageTail(page))
91 get_huge_page_tail(page);
92 (*nr)++;
93 page++;
94 refs++;
95 } while (addr += PAGE_SIZE, addr != end);
96
97 get_head_page_multiple(head, refs);
98 return 1;
99}
100
101static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
102 int write, struct page **pages, int *nr)
103{
104 unsigned long next;
105 pmd_t *pmdp;
106
107 pmdp = pmd_offset(&pud, addr);
108 do {
109 pmd_t pmd = *pmdp;
110
111 next = pmd_addr_end(addr, end);
112 /*
113 * The pmd_trans_splitting() check below explains why
114 * pmdp_splitting_flush has to flush the tlb, to stop
115 * this gup-fast code from running while we set the
116 * splitting bit in the pmd. Returning zero will take
117 * the slow path that will call wait_split_huge_page()
118 * if the pmd is still in splitting state. gup-fast
119 * can't because it has irq disabled and
120 * wait_split_huge_page() would never return as the
121 * tlb flush IPI wouldn't run.
122 */
123 if (pmd_none(pmd) || pmd_trans_splitting(pmd))
124 return 0;
125 if (unlikely(pmd_huge(pmd))) {
126 if (!gup_huge_pmd(pmd, addr, next, write, pages,nr))
127 return 0;
128 } else {
129 if (!gup_pte_range(pmd, addr, next, write, pages,nr))
130 return 0;
131 }
132 } while (pmdp++, addr = next, addr != end);
133
134 return 1;
135}
136
137static int gup_huge_pud(pud_t pud, unsigned long addr, unsigned long end,
138 int write, struct page **pages, int *nr)
139{
140 pte_t pte = *(pte_t *)&pud;
141 struct page *head, *page;
142 int refs;
143
144 if (write && !pte_write(pte))
145 return 0;
146 /* hugepages are never "special" */
147 VM_BUG_ON(pte_special(pte));
148 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
149
150 refs = 0;
151 head = pte_page(pte);
152 page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
153 do {
154 VM_BUG_ON(compound_head(page) != head);
155 pages[*nr] = page;
156 if (PageTail(page))
157 get_huge_page_tail(page);
158 (*nr)++;
159 page++;
160 refs++;
161 } while (addr += PAGE_SIZE, addr != end);
162
163 get_head_page_multiple(head, refs);
164 return 1;
165}
166
167static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
168 int write, struct page **pages, int *nr)
169{
170 unsigned long next;
171 pud_t *pudp;
172
173 pudp = pud_offset(&pgd, addr);
174 do {
175 pud_t pud = *pudp;
176
177 next = pud_addr_end(addr, end);
178 if (pud_none(pud))
179 return 0;
180 if (unlikely(pud_huge(pud))) {
181 if (!gup_huge_pud(pud, addr, next, write, pages,nr))
182 return 0;
183 } else {
184 if (!gup_pmd_range(pud, addr, next, write, pages,nr))
185 return 0;
186 }
187 } while (pudp++, addr = next, addr != end);
188
189 return 1;
190}
191
192/*
193 * Like get_user_pages_fast() except its IRQ-safe in that it won't fall
194 * back to the regular GUP.
195 */
196int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
197 struct page **pages)
198{
199 struct mm_struct *mm = current->mm;
200 unsigned long addr, len, end;
201 unsigned long next;
202 unsigned long flags;
203 pgd_t *pgdp;
204 int nr = 0;
205
206 start &= PAGE_MASK;
207 addr = start;
208 len = (unsigned long) nr_pages << PAGE_SHIFT;
209 end = start + len;
210 if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
211 (void __user *)start, len)))
212 return 0;
213
214 /*
215 * XXX: batch / limit 'nr', to avoid large irq off latency
216 * needs some instrumenting to determine the common sizes used by
217 * important workloads (eg. DB2), and whether limiting the batch
218 * size will decrease performance.
219 *
220 * It seems like we're in the clear for the moment. Direct-IO is
221 * the main guy that batches up lots of get_user_pages, and even
222 * they are limited to 64-at-a-time which is not so many.
223 */
224 /*
225 * This doesn't prevent pagetable teardown, but does prevent
226 * the pagetables and pages from being freed.
227 *
228 * So long as we atomically load page table pointers versus teardown,
229 * we can follow the address down to the page and take a ref on it.
230 */
231 local_irq_save(flags);
232 pgdp = pgd_offset(mm, addr);
233 do {
234 pgd_t pgd = *pgdp;
235
236 next = pgd_addr_end(addr, end);
237 if (pgd_none(pgd))
238 break;
239 if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
240 break;
241 } while (pgdp++, addr = next, addr != end);
242 local_irq_restore(flags);
243
244 return nr;
245}
246
247/**
248 * get_user_pages_fast() - pin user pages in memory
249 * @start: starting user address
250 * @nr_pages: number of pages from start to pin
251 * @write: whether pages will be written to
252 * @pages: array that receives pointers to the pages pinned.
253 * Should be at least nr_pages long.
254 *
255 * Attempt to pin user pages in memory without taking mm->mmap_sem.
256 * If not successful, it will fall back to taking the lock and
257 * calling get_user_pages().
258 *
259 * Returns number of pages pinned. This may be fewer than the number
260 * requested. If nr_pages is 0 or negative, returns 0. If no pages
261 * were pinned, returns -errno.
262 */
263int get_user_pages_fast(unsigned long start, int nr_pages, int write,
264 struct page **pages)
265{
266 struct mm_struct *mm = current->mm;
267 unsigned long addr, len, end;
268 unsigned long next;
269 pgd_t *pgdp;
270 int ret, nr = 0;
271
272 start &= PAGE_MASK;
273 addr = start;
274 len = (unsigned long) nr_pages << PAGE_SHIFT;
275
276 end = start + len;
277 if (end < start || cpu_has_dc_aliases)
278 goto slow_irqon;
279
280 /* XXX: batch / limit 'nr' */
281 local_irq_disable();
282 pgdp = pgd_offset(mm, addr);
283 do {
284 pgd_t pgd = *pgdp;
285
286 next = pgd_addr_end(addr, end);
287 if (pgd_none(pgd))
288 goto slow;
289 if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
290 goto slow;
291 } while (pgdp++, addr = next, addr != end);
292 local_irq_enable();
293
294 VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);
295 return nr;
296slow:
297 local_irq_enable();
298
299slow_irqon:
300 /* Try to get the remaining pages with get_user_pages */
301 start += nr << PAGE_SHIFT;
302 pages += nr;
303
304 down_read(&mm->mmap_sem);
305 ret = get_user_pages(current, mm, start,
306 (end - start) >> PAGE_SHIFT,
307 write, 0, pages, NULL);
308 up_read(&mm->mmap_sem);
309
310 /* Have to be a bit careful with return values */
311 if (nr > 0) {
312 if (ret < 0)
313 ret = nr;
314 else
315 ret += nr;
316 }
317 return ret;
318}