diff options
author | Paul Mundt <lethal@linux-sh.org> | 2010-10-27 03:43:08 -0400 |
---|---|---|
committer | Paul Mundt <lethal@linux-sh.org> | 2010-10-27 03:43:08 -0400 |
commit | 667b279baa529a1b5bd120d4ce3df643a5749263 (patch) | |
tree | c94ca9cd31fd059f7cbe47c33feefec75d345cdb /arch/sh | |
parent | a16382ce1cbcc3ab12274e20f92c09c439629162 (diff) |
sh: lockless get_user_pages_fast()
Implement get_user_pages_fast without locking in the fastpath on sh.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Diffstat (limited to 'arch/sh')
-rw-r--r-- | arch/sh/mm/Makefile | 2 | ||||
-rw-r--r-- | arch/sh/mm/gup.c | 273 |
2 files changed, 274 insertions, 1 deletions
diff --git a/arch/sh/mm/Makefile b/arch/sh/mm/Makefile index ab89ea4f9414..150aa326afff 100644 --- a/arch/sh/mm/Makefile +++ b/arch/sh/mm/Makefile | |||
@@ -15,7 +15,7 @@ cacheops-$(CONFIG_CPU_SHX3) += cache-shx3.o | |||
15 | obj-y += $(cacheops-y) | 15 | obj-y += $(cacheops-y) |
16 | 16 | ||
17 | mmu-y := nommu.o extable_32.o | 17 | mmu-y := nommu.o extable_32.o |
18 | mmu-$(CONFIG_MMU) := extable_$(BITS).o fault_$(BITS).o \ | 18 | mmu-$(CONFIG_MMU) := extable_$(BITS).o fault_$(BITS).o gup.o \ |
19 | ioremap.o kmap.o pgtable.o tlbflush_$(BITS).o | 19 | ioremap.o kmap.o pgtable.o tlbflush_$(BITS).o |
20 | 20 | ||
21 | obj-y += $(mmu-y) | 21 | obj-y += $(mmu-y) |
diff --git a/arch/sh/mm/gup.c b/arch/sh/mm/gup.c new file mode 100644 index 000000000000..bf8daf9d9c9b --- /dev/null +++ b/arch/sh/mm/gup.c | |||
@@ -0,0 +1,273 @@ | |||
1 | /* | ||
2 | * Lockless get_user_pages_fast for SuperH | ||
3 | * | ||
4 | * Copyright (C) 2009 - 2010 Paul Mundt | ||
5 | * | ||
6 | * Cloned from the x86 and PowerPC versions, by: | ||
7 | * | ||
8 | * Copyright (C) 2008 Nick Piggin | ||
9 | * Copyright (C) 2008 Novell Inc. | ||
10 | */ | ||
11 | #include <linux/sched.h> | ||
12 | #include <linux/mm.h> | ||
13 | #include <linux/vmstat.h> | ||
14 | #include <linux/highmem.h> | ||
15 | #include <asm/pgtable.h> | ||
16 | |||
17 | static inline pte_t gup_get_pte(pte_t *ptep) | ||
18 | { | ||
19 | #ifndef CONFIG_X2TLB | ||
20 | return ACCESS_ONCE(*ptep); | ||
21 | #else | ||
22 | /* | ||
23 | * With get_user_pages_fast, we walk down the pagetables without | ||
24 | * taking any locks. For this we would like to load the pointers | ||
25 | * atomically, but that is not possible with 64-bit PTEs. What | ||
26 | * we do have is the guarantee that a pte will only either go | ||
27 | * from not present to present, or present to not present or both | ||
28 | * -- it will not switch to a completely different present page | ||
29 | * without a TLB flush in between; something that we are blocking | ||
30 | * by holding interrupts off. | ||
31 | * | ||
32 | * Setting ptes from not present to present goes: | ||
33 | * ptep->pte_high = h; | ||
34 | * smp_wmb(); | ||
35 | * ptep->pte_low = l; | ||
36 | * | ||
37 | * And present to not present goes: | ||
38 | * ptep->pte_low = 0; | ||
39 | * smp_wmb(); | ||
40 | * ptep->pte_high = 0; | ||
41 | * | ||
42 | * We must ensure here that the load of pte_low sees l iff pte_high | ||
43 | * sees h. We load pte_high *after* loading pte_low, which ensures we | ||
44 | * don't see an older value of pte_high. *Then* we recheck pte_low, | ||
45 | * which ensures that we haven't picked up a changed pte high. We might | ||
46 | * have got rubbish values from pte_low and pte_high, but we are | ||
47 | * guaranteed that pte_low will not have the present bit set *unless* | ||
48 | * it is 'l'. And get_user_pages_fast only operates on present ptes, so | ||
49 | * we're safe. | ||
50 | * | ||
51 | * gup_get_pte should not be used or copied outside gup.c without being | ||
52 | * very careful -- it does not atomically load the pte or anything that | ||
53 | * is likely to be useful for you. | ||
54 | */ | ||
55 | pte_t pte; | ||
56 | |||
57 | retry: | ||
58 | pte.pte_low = ptep->pte_low; | ||
59 | smp_rmb(); | ||
60 | pte.pte_high = ptep->pte_high; | ||
61 | smp_rmb(); | ||
62 | if (unlikely(pte.pte_low != ptep->pte_low)) | ||
63 | goto retry; | ||
64 | |||
65 | return pte; | ||
66 | #endif | ||
67 | } | ||
68 | |||
69 | /* | ||
70 | * The performance critical leaf functions are made noinline otherwise gcc | ||
71 | * inlines everything into a single function which results in too much | ||
72 | * register pressure. | ||
73 | */ | ||
74 | static noinline int gup_pte_range(pmd_t pmd, unsigned long addr, | ||
75 | unsigned long end, int write, struct page **pages, int *nr) | ||
76 | { | ||
77 | u64 mask, result; | ||
78 | pte_t *ptep; | ||
79 | |||
80 | #ifdef CONFIG_X2TLB | ||
81 | result = _PAGE_PRESENT | _PAGE_EXT(_PAGE_EXT_KERN_READ | _PAGE_EXT_USER_READ); | ||
82 | if (write) | ||
83 | result |= _PAGE_EXT(_PAGE_EXT_KERN_WRITE | _PAGE_EXT_USER_WRITE); | ||
84 | #elif defined(CONFIG_SUPERH64) | ||
85 | result = _PAGE_PRESENT | _PAGE_USER | _PAGE_READ; | ||
86 | if (write) | ||
87 | result |= _PAGE_WRITE; | ||
88 | #else | ||
89 | result = _PAGE_PRESENT | _PAGE_USER; | ||
90 | if (write) | ||
91 | result |= _PAGE_RW; | ||
92 | #endif | ||
93 | |||
94 | mask = result | _PAGE_SPECIAL; | ||
95 | |||
96 | ptep = pte_offset_map(&pmd, addr); | ||
97 | do { | ||
98 | pte_t pte = gup_get_pte(ptep); | ||
99 | struct page *page; | ||
100 | |||
101 | if ((pte_val(pte) & mask) != result) { | ||
102 | pte_unmap(ptep); | ||
103 | return 0; | ||
104 | } | ||
105 | VM_BUG_ON(!pfn_valid(pte_pfn(pte))); | ||
106 | page = pte_page(pte); | ||
107 | get_page(page); | ||
108 | pages[*nr] = page; | ||
109 | (*nr)++; | ||
110 | |||
111 | } while (ptep++, addr += PAGE_SIZE, addr != end); | ||
112 | pte_unmap(ptep - 1); | ||
113 | |||
114 | return 1; | ||
115 | } | ||
116 | |||
117 | static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end, | ||
118 | int write, struct page **pages, int *nr) | ||
119 | { | ||
120 | unsigned long next; | ||
121 | pmd_t *pmdp; | ||
122 | |||
123 | pmdp = pmd_offset(&pud, addr); | ||
124 | do { | ||
125 | pmd_t pmd = *pmdp; | ||
126 | |||
127 | next = pmd_addr_end(addr, end); | ||
128 | if (pmd_none(pmd)) | ||
129 | return 0; | ||
130 | if (!gup_pte_range(pmd, addr, next, write, pages, nr)) | ||
131 | return 0; | ||
132 | } while (pmdp++, addr = next, addr != end); | ||
133 | |||
134 | return 1; | ||
135 | } | ||
136 | |||
137 | static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end, | ||
138 | int write, struct page **pages, int *nr) | ||
139 | { | ||
140 | unsigned long next; | ||
141 | pud_t *pudp; | ||
142 | |||
143 | pudp = pud_offset(&pgd, addr); | ||
144 | do { | ||
145 | pud_t pud = *pudp; | ||
146 | |||
147 | next = pud_addr_end(addr, end); | ||
148 | if (pud_none(pud)) | ||
149 | return 0; | ||
150 | if (!gup_pmd_range(pud, addr, next, write, pages, nr)) | ||
151 | return 0; | ||
152 | } while (pudp++, addr = next, addr != end); | ||
153 | |||
154 | return 1; | ||
155 | } | ||
156 | |||
157 | /* | ||
158 | * Like get_user_pages_fast() except its IRQ-safe in that it won't fall | ||
159 | * back to the regular GUP. | ||
160 | */ | ||
161 | int __get_user_pages_fast(unsigned long start, int nr_pages, int write, | ||
162 | struct page **pages) | ||
163 | { | ||
164 | struct mm_struct *mm = current->mm; | ||
165 | unsigned long addr, len, end; | ||
166 | unsigned long next; | ||
167 | unsigned long flags; | ||
168 | pgd_t *pgdp; | ||
169 | int nr = 0; | ||
170 | |||
171 | start &= PAGE_MASK; | ||
172 | addr = start; | ||
173 | len = (unsigned long) nr_pages << PAGE_SHIFT; | ||
174 | end = start + len; | ||
175 | if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ, | ||
176 | (void __user *)start, len))) | ||
177 | return 0; | ||
178 | |||
179 | /* | ||
180 | * This doesn't prevent pagetable teardown, but does prevent | ||
181 | * the pagetables and pages from being freed. | ||
182 | */ | ||
183 | local_irq_save(flags); | ||
184 | pgdp = pgd_offset(mm, addr); | ||
185 | do { | ||
186 | pgd_t pgd = *pgdp; | ||
187 | |||
188 | next = pgd_addr_end(addr, end); | ||
189 | if (pgd_none(pgd)) | ||
190 | break; | ||
191 | if (!gup_pud_range(pgd, addr, next, write, pages, &nr)) | ||
192 | break; | ||
193 | } while (pgdp++, addr = next, addr != end); | ||
194 | local_irq_restore(flags); | ||
195 | |||
196 | return nr; | ||
197 | } | ||
198 | |||
199 | /** | ||
200 | * get_user_pages_fast() - pin user pages in memory | ||
201 | * @start: starting user address | ||
202 | * @nr_pages: number of pages from start to pin | ||
203 | * @write: whether pages will be written to | ||
204 | * @pages: array that receives pointers to the pages pinned. | ||
205 | * Should be at least nr_pages long. | ||
206 | * | ||
207 | * Attempt to pin user pages in memory without taking mm->mmap_sem. | ||
208 | * If not successful, it will fall back to taking the lock and | ||
209 | * calling get_user_pages(). | ||
210 | * | ||
211 | * Returns number of pages pinned. This may be fewer than the number | ||
212 | * requested. If nr_pages is 0 or negative, returns 0. If no pages | ||
213 | * were pinned, returns -errno. | ||
214 | */ | ||
215 | int get_user_pages_fast(unsigned long start, int nr_pages, int write, | ||
216 | struct page **pages) | ||
217 | { | ||
218 | struct mm_struct *mm = current->mm; | ||
219 | unsigned long addr, len, end; | ||
220 | unsigned long next; | ||
221 | pgd_t *pgdp; | ||
222 | int nr = 0; | ||
223 | |||
224 | start &= PAGE_MASK; | ||
225 | addr = start; | ||
226 | len = (unsigned long) nr_pages << PAGE_SHIFT; | ||
227 | |||
228 | end = start + len; | ||
229 | if (end < start) | ||
230 | goto slow_irqon; | ||
231 | |||
232 | local_irq_disable(); | ||
233 | pgdp = pgd_offset(mm, addr); | ||
234 | do { | ||
235 | pgd_t pgd = *pgdp; | ||
236 | |||
237 | next = pgd_addr_end(addr, end); | ||
238 | if (pgd_none(pgd)) | ||
239 | goto slow; | ||
240 | if (!gup_pud_range(pgd, addr, next, write, pages, &nr)) | ||
241 | goto slow; | ||
242 | } while (pgdp++, addr = next, addr != end); | ||
243 | local_irq_enable(); | ||
244 | |||
245 | VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT); | ||
246 | return nr; | ||
247 | |||
248 | { | ||
249 | int ret; | ||
250 | |||
251 | slow: | ||
252 | local_irq_enable(); | ||
253 | slow_irqon: | ||
254 | /* Try to get the remaining pages with get_user_pages */ | ||
255 | start += nr << PAGE_SHIFT; | ||
256 | pages += nr; | ||
257 | |||
258 | down_read(&mm->mmap_sem); | ||
259 | ret = get_user_pages(current, mm, start, | ||
260 | (end - start) >> PAGE_SHIFT, write, 0, pages, NULL); | ||
261 | up_read(&mm->mmap_sem); | ||
262 | |||
263 | /* Have to be a bit careful with return values */ | ||
264 | if (nr > 0) { | ||
265 | if (ret < 0) | ||
266 | ret = nr; | ||
267 | else | ||
268 | ret += nr; | ||
269 | } | ||
270 | |||
271 | return ret; | ||
272 | } | ||
273 | } | ||