Revert "mm: replace p??_write with pte_access_permitted in fault + gup paths"
[muen/linux.git] / arch / sparc / mm / gup.c
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Lockless get_user_pages_fast for sparc, cribbed from powerpc
4  *
5  * Copyright (C) 2008 Nick Piggin
6  * Copyright (C) 2008 Novell Inc.
7  */
8
9 #include <linux/sched.h>
10 #include <linux/mm.h>
11 #include <linux/vmstat.h>
12 #include <linux/pagemap.h>
13 #include <linux/rwsem.h>
14 #include <asm/pgtable.h>
15
16 /*
17  * The performance critical leaf functions are made noinline otherwise gcc
18  * inlines everything into a single function which results in too much
19  * register pressure.
20  */
21 static noinline int gup_pte_range(pmd_t pmd, unsigned long addr,
22                 unsigned long end, int write, struct page **pages, int *nr)
23 {
24         unsigned long mask, result;
25         pte_t *ptep;
26
27         if (tlb_type == hypervisor) {
28                 result = _PAGE_PRESENT_4V|_PAGE_P_4V;
29                 if (write)
30                         result |= _PAGE_WRITE_4V;
31         } else {
32                 result = _PAGE_PRESENT_4U|_PAGE_P_4U;
33                 if (write)
34                         result |= _PAGE_WRITE_4U;
35         }
36         mask = result | _PAGE_SPECIAL;
37
38         ptep = pte_offset_kernel(&pmd, addr);
39         do {
40                 struct page *page, *head;
41                 pte_t pte = *ptep;
42
43                 if ((pte_val(pte) & mask) != result)
44                         return 0;
45                 VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
46
47                 /* The hugepage case is simplified on sparc64 because
48                  * we encode the sub-page pfn offsets into the
49                  * hugepage PTEs.  We could optimize this in the future
50                  * use page_cache_add_speculative() for the hugepage case.
51                  */
52                 page = pte_page(pte);
53                 head = compound_head(page);
54                 if (!page_cache_get_speculative(head))
55                         return 0;
56                 if (unlikely(pte_val(pte) != pte_val(*ptep))) {
57                         put_page(head);
58                         return 0;
59                 }
60
61                 pages[*nr] = page;
62                 (*nr)++;
63         } while (ptep++, addr += PAGE_SIZE, addr != end);
64
65         return 1;
66 }
67
68 static int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
69                         unsigned long end, int write, struct page **pages,
70                         int *nr)
71 {
72         struct page *head, *page;
73         int refs;
74
75         if (!(pmd_val(pmd) & _PAGE_VALID))
76                 return 0;
77
78         if (write && !pmd_write(pmd))
79                 return 0;
80
81         refs = 0;
82         page = pmd_page(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
83         head = compound_head(page);
84         do {
85                 VM_BUG_ON(compound_head(page) != head);
86                 pages[*nr] = page;
87                 (*nr)++;
88                 page++;
89                 refs++;
90         } while (addr += PAGE_SIZE, addr != end);
91
92         if (!page_cache_add_speculative(head, refs)) {
93                 *nr -= refs;
94                 return 0;
95         }
96
97         if (unlikely(pmd_val(pmd) != pmd_val(*pmdp))) {
98                 *nr -= refs;
99                 while (refs--)
100                         put_page(head);
101                 return 0;
102         }
103
104         return 1;
105 }
106
107 static int gup_huge_pud(pud_t *pudp, pud_t pud, unsigned long addr,
108                         unsigned long end, int write, struct page **pages,
109                         int *nr)
110 {
111         struct page *head, *page;
112         int refs;
113
114         if (!(pud_val(pud) & _PAGE_VALID))
115                 return 0;
116
117         if (write && !pud_write(pud))
118                 return 0;
119
120         refs = 0;
121         page = pud_page(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
122         head = compound_head(page);
123         do {
124                 VM_BUG_ON(compound_head(page) != head);
125                 pages[*nr] = page;
126                 (*nr)++;
127                 page++;
128                 refs++;
129         } while (addr += PAGE_SIZE, addr != end);
130
131         if (!page_cache_add_speculative(head, refs)) {
132                 *nr -= refs;
133                 return 0;
134         }
135
136         if (unlikely(pud_val(pud) != pud_val(*pudp))) {
137                 *nr -= refs;
138                 while (refs--)
139                         put_page(head);
140                 return 0;
141         }
142
143         return 1;
144 }
145
146 static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
147                 int write, struct page **pages, int *nr)
148 {
149         unsigned long next;
150         pmd_t *pmdp;
151
152         pmdp = pmd_offset(&pud, addr);
153         do {
154                 pmd_t pmd = *pmdp;
155
156                 next = pmd_addr_end(addr, end);
157                 if (pmd_none(pmd))
158                         return 0;
159                 if (unlikely(pmd_large(pmd))) {
160                         if (!gup_huge_pmd(pmdp, pmd, addr, next,
161                                           write, pages, nr))
162                                 return 0;
163                 } else if (!gup_pte_range(pmd, addr, next, write,
164                                           pages, nr))
165                         return 0;
166         } while (pmdp++, addr = next, addr != end);
167
168         return 1;
169 }
170
171 static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
172                 int write, struct page **pages, int *nr)
173 {
174         unsigned long next;
175         pud_t *pudp;
176
177         pudp = pud_offset(&pgd, addr);
178         do {
179                 pud_t pud = *pudp;
180
181                 next = pud_addr_end(addr, end);
182                 if (pud_none(pud))
183                         return 0;
184                 if (unlikely(pud_large(pud))) {
185                         if (!gup_huge_pud(pudp, pud, addr, next,
186                                           write, pages, nr))
187                                 return 0;
188                 } else if (!gup_pmd_range(pud, addr, next, write, pages, nr))
189                         return 0;
190         } while (pudp++, addr = next, addr != end);
191
192         return 1;
193 }
194
195 int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
196                           struct page **pages)
197 {
198         struct mm_struct *mm = current->mm;
199         unsigned long addr, len, end;
200         unsigned long next, flags;
201         pgd_t *pgdp;
202         int nr = 0;
203
204         start &= PAGE_MASK;
205         addr = start;
206         len = (unsigned long) nr_pages << PAGE_SHIFT;
207         end = start + len;
208
209         local_irq_save(flags);
210         pgdp = pgd_offset(mm, addr);
211         do {
212                 pgd_t pgd = *pgdp;
213
214                 next = pgd_addr_end(addr, end);
215                 if (pgd_none(pgd))
216                         break;
217                 if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
218                         break;
219         } while (pgdp++, addr = next, addr != end);
220         local_irq_restore(flags);
221
222         return nr;
223 }
224
225 int get_user_pages_fast(unsigned long start, int nr_pages, int write,
226                         struct page **pages)
227 {
228         struct mm_struct *mm = current->mm;
229         unsigned long addr, len, end;
230         unsigned long next;
231         pgd_t *pgdp;
232         int nr = 0;
233
234         start &= PAGE_MASK;
235         addr = start;
236         len = (unsigned long) nr_pages << PAGE_SHIFT;
237         end = start + len;
238
239         /*
240          * XXX: batch / limit 'nr', to avoid large irq off latency
241          * needs some instrumenting to determine the common sizes used by
242          * important workloads (eg. DB2), and whether limiting the batch size
243          * will decrease performance.
244          *
245          * It seems like we're in the clear for the moment. Direct-IO is
246          * the main guy that batches up lots of get_user_pages, and even
247          * they are limited to 64-at-a-time which is not so many.
248          */
249         /*
250          * This doesn't prevent pagetable teardown, but does prevent
251          * the pagetables from being freed on sparc.
252          *
253          * So long as we atomically load page table pointers versus teardown,
254          * we can follow the address down to the the page and take a ref on it.
255          */
256         local_irq_disable();
257
258         pgdp = pgd_offset(mm, addr);
259         do {
260                 pgd_t pgd = *pgdp;
261
262                 next = pgd_addr_end(addr, end);
263                 if (pgd_none(pgd))
264                         goto slow;
265                 if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
266                         goto slow;
267         } while (pgdp++, addr = next, addr != end);
268
269         local_irq_enable();
270
271         VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);
272         return nr;
273
274         {
275                 int ret;
276
277 slow:
278                 local_irq_enable();
279
280                 /* Try to get the remaining pages with get_user_pages */
281                 start += nr << PAGE_SHIFT;
282                 pages += nr;
283
284                 ret = get_user_pages_unlocked(start,
285                         (end - start) >> PAGE_SHIFT, pages,
286                         write ? FOLL_WRITE : 0);
287
288                 /* Have to be a bit careful with return values */
289                 if (nr > 0) {
290                         if (ret < 0)
291                                 ret = nr;
292                         else
293                                 ret += nr;
294                 }
295
296                 return ret;
297         }
298 }