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1da177e4 LT |
1 | #ifndef _ASM_GENERIC_PGTABLE_H |
2 | #define _ASM_GENERIC_PGTABLE_H | |
3 | ||
673eae82 | 4 | #ifndef __ASSEMBLY__ |
9535239f | 5 | #ifdef CONFIG_MMU |
673eae82 | 6 | |
fbd71844 | 7 | #include <linux/mm_types.h> |
187f1882 | 8 | #include <linux/bug.h> |
fbd71844 | 9 | |
1da177e4 | 10 | #ifndef __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS |
e2cda322 AA |
11 | extern int ptep_set_access_flags(struct vm_area_struct *vma, |
12 | unsigned long address, pte_t *ptep, | |
13 | pte_t entry, int dirty); | |
14 | #endif | |
15 | ||
16 | #ifndef __HAVE_ARCH_PMDP_SET_ACCESS_FLAGS | |
17 | extern int pmdp_set_access_flags(struct vm_area_struct *vma, | |
18 | unsigned long address, pmd_t *pmdp, | |
19 | pmd_t entry, int dirty); | |
1da177e4 LT |
20 | #endif |
21 | ||
22 | #ifndef __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG | |
e2cda322 AA |
23 | static inline int ptep_test_and_clear_young(struct vm_area_struct *vma, |
24 | unsigned long address, | |
25 | pte_t *ptep) | |
26 | { | |
27 | pte_t pte = *ptep; | |
28 | int r = 1; | |
29 | if (!pte_young(pte)) | |
30 | r = 0; | |
31 | else | |
32 | set_pte_at(vma->vm_mm, address, ptep, pte_mkold(pte)); | |
33 | return r; | |
34 | } | |
35 | #endif | |
36 | ||
37 | #ifndef __HAVE_ARCH_PMDP_TEST_AND_CLEAR_YOUNG | |
38 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE | |
39 | static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma, | |
40 | unsigned long address, | |
41 | pmd_t *pmdp) | |
42 | { | |
43 | pmd_t pmd = *pmdp; | |
44 | int r = 1; | |
45 | if (!pmd_young(pmd)) | |
46 | r = 0; | |
47 | else | |
48 | set_pmd_at(vma->vm_mm, address, pmdp, pmd_mkold(pmd)); | |
49 | return r; | |
50 | } | |
51 | #else /* CONFIG_TRANSPARENT_HUGEPAGE */ | |
52 | static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma, | |
53 | unsigned long address, | |
54 | pmd_t *pmdp) | |
55 | { | |
56 | BUG(); | |
57 | return 0; | |
58 | } | |
59 | #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ | |
1da177e4 LT |
60 | #endif |
61 | ||
62 | #ifndef __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH | |
e2cda322 AA |
63 | int ptep_clear_flush_young(struct vm_area_struct *vma, |
64 | unsigned long address, pte_t *ptep); | |
65 | #endif | |
66 | ||
67 | #ifndef __HAVE_ARCH_PMDP_CLEAR_YOUNG_FLUSH | |
68 | int pmdp_clear_flush_young(struct vm_area_struct *vma, | |
69 | unsigned long address, pmd_t *pmdp); | |
1da177e4 LT |
70 | #endif |
71 | ||
1da177e4 | 72 | #ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR |
e2cda322 AA |
73 | static inline pte_t ptep_get_and_clear(struct mm_struct *mm, |
74 | unsigned long address, | |
75 | pte_t *ptep) | |
76 | { | |
77 | pte_t pte = *ptep; | |
78 | pte_clear(mm, address, ptep); | |
79 | return pte; | |
80 | } | |
81 | #endif | |
82 | ||
83 | #ifndef __HAVE_ARCH_PMDP_GET_AND_CLEAR | |
84 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE | |
85 | static inline pmd_t pmdp_get_and_clear(struct mm_struct *mm, | |
86 | unsigned long address, | |
87 | pmd_t *pmdp) | |
88 | { | |
89 | pmd_t pmd = *pmdp; | |
90 | pmd_clear(mm, address, pmdp); | |
91 | return pmd; | |
49b24d6b | 92 | } |
e2cda322 | 93 | #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ |
1da177e4 LT |
94 | #endif |
95 | ||
a600388d | 96 | #ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR_FULL |
e2cda322 AA |
97 | static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm, |
98 | unsigned long address, pte_t *ptep, | |
99 | int full) | |
100 | { | |
101 | pte_t pte; | |
102 | pte = ptep_get_and_clear(mm, address, ptep); | |
103 | return pte; | |
104 | } | |
a600388d ZA |
105 | #endif |
106 | ||
9888a1ca ZA |
107 | /* |
108 | * Some architectures may be able to avoid expensive synchronization | |
109 | * primitives when modifications are made to PTE's which are already | |
110 | * not present, or in the process of an address space destruction. | |
111 | */ | |
112 | #ifndef __HAVE_ARCH_PTE_CLEAR_NOT_PRESENT_FULL | |
e2cda322 AA |
113 | static inline void pte_clear_not_present_full(struct mm_struct *mm, |
114 | unsigned long address, | |
115 | pte_t *ptep, | |
116 | int full) | |
117 | { | |
118 | pte_clear(mm, address, ptep); | |
119 | } | |
a600388d ZA |
120 | #endif |
121 | ||
1da177e4 | 122 | #ifndef __HAVE_ARCH_PTEP_CLEAR_FLUSH |
e2cda322 AA |
123 | extern pte_t ptep_clear_flush(struct vm_area_struct *vma, |
124 | unsigned long address, | |
125 | pte_t *ptep); | |
126 | #endif | |
127 | ||
128 | #ifndef __HAVE_ARCH_PMDP_CLEAR_FLUSH | |
129 | extern pmd_t pmdp_clear_flush(struct vm_area_struct *vma, | |
130 | unsigned long address, | |
131 | pmd_t *pmdp); | |
1da177e4 LT |
132 | #endif |
133 | ||
134 | #ifndef __HAVE_ARCH_PTEP_SET_WRPROTECT | |
8c65b4a6 | 135 | struct mm_struct; |
1da177e4 LT |
136 | static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long address, pte_t *ptep) |
137 | { | |
138 | pte_t old_pte = *ptep; | |
139 | set_pte_at(mm, address, ptep, pte_wrprotect(old_pte)); | |
140 | } | |
141 | #endif | |
142 | ||
e2cda322 AA |
143 | #ifndef __HAVE_ARCH_PMDP_SET_WRPROTECT |
144 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE | |
145 | static inline void pmdp_set_wrprotect(struct mm_struct *mm, | |
146 | unsigned long address, pmd_t *pmdp) | |
147 | { | |
148 | pmd_t old_pmd = *pmdp; | |
149 | set_pmd_at(mm, address, pmdp, pmd_wrprotect(old_pmd)); | |
150 | } | |
151 | #else /* CONFIG_TRANSPARENT_HUGEPAGE */ | |
152 | static inline void pmdp_set_wrprotect(struct mm_struct *mm, | |
153 | unsigned long address, pmd_t *pmdp) | |
154 | { | |
155 | BUG(); | |
156 | } | |
157 | #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ | |
158 | #endif | |
159 | ||
160 | #ifndef __HAVE_ARCH_PMDP_SPLITTING_FLUSH | |
73636b1a CM |
161 | extern void pmdp_splitting_flush(struct vm_area_struct *vma, |
162 | unsigned long address, pmd_t *pmdp); | |
e2cda322 AA |
163 | #endif |
164 | ||
e3ebcf64 GS |
165 | #ifndef __HAVE_ARCH_PGTABLE_DEPOSIT |
166 | extern void pgtable_trans_huge_deposit(struct mm_struct *mm, pgtable_t pgtable); | |
167 | #endif | |
168 | ||
169 | #ifndef __HAVE_ARCH_PGTABLE_WITHDRAW | |
170 | extern pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm); | |
171 | #endif | |
172 | ||
46dcde73 GS |
173 | #ifndef __HAVE_ARCH_PMDP_INVALIDATE |
174 | extern void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address, | |
175 | pmd_t *pmdp); | |
176 | #endif | |
177 | ||
1da177e4 | 178 | #ifndef __HAVE_ARCH_PTE_SAME |
e2cda322 AA |
179 | static inline int pte_same(pte_t pte_a, pte_t pte_b) |
180 | { | |
181 | return pte_val(pte_a) == pte_val(pte_b); | |
182 | } | |
183 | #endif | |
184 | ||
185 | #ifndef __HAVE_ARCH_PMD_SAME | |
186 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE | |
187 | static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b) | |
188 | { | |
189 | return pmd_val(pmd_a) == pmd_val(pmd_b); | |
190 | } | |
191 | #else /* CONFIG_TRANSPARENT_HUGEPAGE */ | |
192 | static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b) | |
193 | { | |
194 | BUG(); | |
195 | return 0; | |
196 | } | |
197 | #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ | |
1da177e4 LT |
198 | #endif |
199 | ||
2d42552d MS |
200 | #ifndef __HAVE_ARCH_PAGE_TEST_AND_CLEAR_DIRTY |
201 | #define page_test_and_clear_dirty(pfn, mapped) (0) | |
6c210482 MS |
202 | #endif |
203 | ||
2d42552d | 204 | #ifndef __HAVE_ARCH_PAGE_TEST_AND_CLEAR_DIRTY |
b4955ce3 AK |
205 | #define pte_maybe_dirty(pte) pte_dirty(pte) |
206 | #else | |
207 | #define pte_maybe_dirty(pte) (1) | |
1da177e4 LT |
208 | #endif |
209 | ||
210 | #ifndef __HAVE_ARCH_PAGE_TEST_AND_CLEAR_YOUNG | |
2d42552d | 211 | #define page_test_and_clear_young(pfn) (0) |
1da177e4 LT |
212 | #endif |
213 | ||
214 | #ifndef __HAVE_ARCH_PGD_OFFSET_GATE | |
215 | #define pgd_offset_gate(mm, addr) pgd_offset(mm, addr) | |
216 | #endif | |
217 | ||
0b0968a3 | 218 | #ifndef __HAVE_ARCH_MOVE_PTE |
8b1f3124 | 219 | #define move_pte(pte, prot, old_addr, new_addr) (pte) |
8b1f3124 NP |
220 | #endif |
221 | ||
61c77326 SL |
222 | #ifndef flush_tlb_fix_spurious_fault |
223 | #define flush_tlb_fix_spurious_fault(vma, address) flush_tlb_page(vma, address) | |
224 | #endif | |
225 | ||
0634a632 PM |
226 | #ifndef pgprot_noncached |
227 | #define pgprot_noncached(prot) (prot) | |
228 | #endif | |
229 | ||
2520bd31 | 230 | #ifndef pgprot_writecombine |
231 | #define pgprot_writecombine pgprot_noncached | |
232 | #endif | |
233 | ||
1da177e4 | 234 | /* |
8f6c99c1 HD |
235 | * When walking page tables, get the address of the next boundary, |
236 | * or the end address of the range if that comes earlier. Although no | |
237 | * vma end wraps to 0, rounded up __boundary may wrap to 0 throughout. | |
1da177e4 LT |
238 | */ |
239 | ||
1da177e4 LT |
240 | #define pgd_addr_end(addr, end) \ |
241 | ({ unsigned long __boundary = ((addr) + PGDIR_SIZE) & PGDIR_MASK; \ | |
242 | (__boundary - 1 < (end) - 1)? __boundary: (end); \ | |
243 | }) | |
1da177e4 LT |
244 | |
245 | #ifndef pud_addr_end | |
246 | #define pud_addr_end(addr, end) \ | |
247 | ({ unsigned long __boundary = ((addr) + PUD_SIZE) & PUD_MASK; \ | |
248 | (__boundary - 1 < (end) - 1)? __boundary: (end); \ | |
249 | }) | |
250 | #endif | |
251 | ||
252 | #ifndef pmd_addr_end | |
253 | #define pmd_addr_end(addr, end) \ | |
254 | ({ unsigned long __boundary = ((addr) + PMD_SIZE) & PMD_MASK; \ | |
255 | (__boundary - 1 < (end) - 1)? __boundary: (end); \ | |
256 | }) | |
257 | #endif | |
258 | ||
1da177e4 LT |
259 | /* |
260 | * When walking page tables, we usually want to skip any p?d_none entries; | |
261 | * and any p?d_bad entries - reporting the error before resetting to none. | |
262 | * Do the tests inline, but report and clear the bad entry in mm/memory.c. | |
263 | */ | |
264 | void pgd_clear_bad(pgd_t *); | |
265 | void pud_clear_bad(pud_t *); | |
266 | void pmd_clear_bad(pmd_t *); | |
267 | ||
268 | static inline int pgd_none_or_clear_bad(pgd_t *pgd) | |
269 | { | |
270 | if (pgd_none(*pgd)) | |
271 | return 1; | |
272 | if (unlikely(pgd_bad(*pgd))) { | |
273 | pgd_clear_bad(pgd); | |
274 | return 1; | |
275 | } | |
276 | return 0; | |
277 | } | |
278 | ||
279 | static inline int pud_none_or_clear_bad(pud_t *pud) | |
280 | { | |
281 | if (pud_none(*pud)) | |
282 | return 1; | |
283 | if (unlikely(pud_bad(*pud))) { | |
284 | pud_clear_bad(pud); | |
285 | return 1; | |
286 | } | |
287 | return 0; | |
288 | } | |
289 | ||
290 | static inline int pmd_none_or_clear_bad(pmd_t *pmd) | |
291 | { | |
292 | if (pmd_none(*pmd)) | |
293 | return 1; | |
294 | if (unlikely(pmd_bad(*pmd))) { | |
295 | pmd_clear_bad(pmd); | |
296 | return 1; | |
297 | } | |
298 | return 0; | |
299 | } | |
9535239f | 300 | |
1ea0704e JF |
301 | static inline pte_t __ptep_modify_prot_start(struct mm_struct *mm, |
302 | unsigned long addr, | |
303 | pte_t *ptep) | |
304 | { | |
305 | /* | |
306 | * Get the current pte state, but zero it out to make it | |
307 | * non-present, preventing the hardware from asynchronously | |
308 | * updating it. | |
309 | */ | |
310 | return ptep_get_and_clear(mm, addr, ptep); | |
311 | } | |
312 | ||
313 | static inline void __ptep_modify_prot_commit(struct mm_struct *mm, | |
314 | unsigned long addr, | |
315 | pte_t *ptep, pte_t pte) | |
316 | { | |
317 | /* | |
318 | * The pte is non-present, so there's no hardware state to | |
319 | * preserve. | |
320 | */ | |
321 | set_pte_at(mm, addr, ptep, pte); | |
322 | } | |
323 | ||
324 | #ifndef __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION | |
325 | /* | |
326 | * Start a pte protection read-modify-write transaction, which | |
327 | * protects against asynchronous hardware modifications to the pte. | |
328 | * The intention is not to prevent the hardware from making pte | |
329 | * updates, but to prevent any updates it may make from being lost. | |
330 | * | |
331 | * This does not protect against other software modifications of the | |
332 | * pte; the appropriate pte lock must be held over the transation. | |
333 | * | |
334 | * Note that this interface is intended to be batchable, meaning that | |
335 | * ptep_modify_prot_commit may not actually update the pte, but merely | |
336 | * queue the update to be done at some later time. The update must be | |
337 | * actually committed before the pte lock is released, however. | |
338 | */ | |
339 | static inline pte_t ptep_modify_prot_start(struct mm_struct *mm, | |
340 | unsigned long addr, | |
341 | pte_t *ptep) | |
342 | { | |
343 | return __ptep_modify_prot_start(mm, addr, ptep); | |
344 | } | |
345 | ||
346 | /* | |
347 | * Commit an update to a pte, leaving any hardware-controlled bits in | |
348 | * the PTE unmodified. | |
349 | */ | |
350 | static inline void ptep_modify_prot_commit(struct mm_struct *mm, | |
351 | unsigned long addr, | |
352 | pte_t *ptep, pte_t pte) | |
353 | { | |
354 | __ptep_modify_prot_commit(mm, addr, ptep, pte); | |
355 | } | |
356 | #endif /* __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION */ | |
fe1a6875 | 357 | #endif /* CONFIG_MMU */ |
1ea0704e | 358 | |
9535239f GU |
359 | /* |
360 | * A facility to provide lazy MMU batching. This allows PTE updates and | |
361 | * page invalidations to be delayed until a call to leave lazy MMU mode | |
362 | * is issued. Some architectures may benefit from doing this, and it is | |
363 | * beneficial for both shadow and direct mode hypervisors, which may batch | |
364 | * the PTE updates which happen during this window. Note that using this | |
365 | * interface requires that read hazards be removed from the code. A read | |
366 | * hazard could result in the direct mode hypervisor case, since the actual | |
367 | * write to the page tables may not yet have taken place, so reads though | |
368 | * a raw PTE pointer after it has been modified are not guaranteed to be | |
369 | * up to date. This mode can only be entered and left under the protection of | |
370 | * the page table locks for all page tables which may be modified. In the UP | |
371 | * case, this is required so that preemption is disabled, and in the SMP case, | |
372 | * it must synchronize the delayed page table writes properly on other CPUs. | |
373 | */ | |
374 | #ifndef __HAVE_ARCH_ENTER_LAZY_MMU_MODE | |
375 | #define arch_enter_lazy_mmu_mode() do {} while (0) | |
376 | #define arch_leave_lazy_mmu_mode() do {} while (0) | |
377 | #define arch_flush_lazy_mmu_mode() do {} while (0) | |
378 | #endif | |
379 | ||
380 | /* | |
7fd7d83d JF |
381 | * A facility to provide batching of the reload of page tables and |
382 | * other process state with the actual context switch code for | |
383 | * paravirtualized guests. By convention, only one of the batched | |
384 | * update (lazy) modes (CPU, MMU) should be active at any given time, | |
385 | * entry should never be nested, and entry and exits should always be | |
386 | * paired. This is for sanity of maintaining and reasoning about the | |
387 | * kernel code. In this case, the exit (end of the context switch) is | |
388 | * in architecture-specific code, and so doesn't need a generic | |
389 | * definition. | |
9535239f | 390 | */ |
7fd7d83d | 391 | #ifndef __HAVE_ARCH_START_CONTEXT_SWITCH |
224101ed | 392 | #define arch_start_context_switch(prev) do {} while (0) |
9535239f GU |
393 | #endif |
394 | ||
34801ba9 | 395 | #ifndef __HAVE_PFNMAP_TRACKING |
396 | /* | |
5180da41 SS |
397 | * Interfaces that can be used by architecture code to keep track of |
398 | * memory type of pfn mappings specified by the remap_pfn_range, | |
399 | * vm_insert_pfn. | |
400 | */ | |
401 | ||
402 | /* | |
403 | * track_pfn_remap is called when a _new_ pfn mapping is being established | |
404 | * by remap_pfn_range() for physical range indicated by pfn and size. | |
34801ba9 | 405 | */ |
5180da41 | 406 | static inline int track_pfn_remap(struct vm_area_struct *vma, pgprot_t *prot, |
b3b9c293 KK |
407 | unsigned long pfn, unsigned long addr, |
408 | unsigned long size) | |
34801ba9 | 409 | { |
410 | return 0; | |
411 | } | |
412 | ||
413 | /* | |
5180da41 SS |
414 | * track_pfn_insert is called when a _new_ single pfn is established |
415 | * by vm_insert_pfn(). | |
416 | */ | |
417 | static inline int track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot, | |
418 | unsigned long pfn) | |
419 | { | |
420 | return 0; | |
421 | } | |
422 | ||
423 | /* | |
424 | * track_pfn_copy is called when vma that is covering the pfnmap gets | |
34801ba9 | 425 | * copied through copy_page_range(). |
426 | */ | |
5180da41 | 427 | static inline int track_pfn_copy(struct vm_area_struct *vma) |
34801ba9 | 428 | { |
429 | return 0; | |
430 | } | |
431 | ||
432 | /* | |
34801ba9 | 433 | * untrack_pfn_vma is called while unmapping a pfnmap for a region. |
434 | * untrack can be called for a specific region indicated by pfn and size or | |
5180da41 | 435 | * can be for the entire vma (in which case pfn, size are zero). |
34801ba9 | 436 | */ |
5180da41 SS |
437 | static inline void untrack_pfn(struct vm_area_struct *vma, |
438 | unsigned long pfn, unsigned long size) | |
34801ba9 | 439 | { |
440 | } | |
441 | #else | |
5180da41 | 442 | extern int track_pfn_remap(struct vm_area_struct *vma, pgprot_t *prot, |
b3b9c293 KK |
443 | unsigned long pfn, unsigned long addr, |
444 | unsigned long size); | |
5180da41 SS |
445 | extern int track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot, |
446 | unsigned long pfn); | |
447 | extern int track_pfn_copy(struct vm_area_struct *vma); | |
448 | extern void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn, | |
449 | unsigned long size); | |
34801ba9 | 450 | #endif |
451 | ||
1a5a9906 AA |
452 | #ifdef CONFIG_MMU |
453 | ||
5f6e8da7 AA |
454 | #ifndef CONFIG_TRANSPARENT_HUGEPAGE |
455 | static inline int pmd_trans_huge(pmd_t pmd) | |
456 | { | |
457 | return 0; | |
458 | } | |
459 | static inline int pmd_trans_splitting(pmd_t pmd) | |
460 | { | |
461 | return 0; | |
462 | } | |
e2cda322 AA |
463 | #ifndef __HAVE_ARCH_PMD_WRITE |
464 | static inline int pmd_write(pmd_t pmd) | |
465 | { | |
466 | BUG(); | |
467 | return 0; | |
468 | } | |
469 | #endif /* __HAVE_ARCH_PMD_WRITE */ | |
1a5a9906 AA |
470 | #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ |
471 | ||
26c19178 AA |
472 | #ifndef pmd_read_atomic |
473 | static inline pmd_t pmd_read_atomic(pmd_t *pmdp) | |
474 | { | |
475 | /* | |
476 | * Depend on compiler for an atomic pmd read. NOTE: this is | |
477 | * only going to work, if the pmdval_t isn't larger than | |
478 | * an unsigned long. | |
479 | */ | |
480 | return *pmdp; | |
481 | } | |
482 | #endif | |
483 | ||
1a5a9906 AA |
484 | /* |
485 | * This function is meant to be used by sites walking pagetables with | |
486 | * the mmap_sem hold in read mode to protect against MADV_DONTNEED and | |
487 | * transhuge page faults. MADV_DONTNEED can convert a transhuge pmd | |
488 | * into a null pmd and the transhuge page fault can convert a null pmd | |
489 | * into an hugepmd or into a regular pmd (if the hugepage allocation | |
490 | * fails). While holding the mmap_sem in read mode the pmd becomes | |
491 | * stable and stops changing under us only if it's not null and not a | |
492 | * transhuge pmd. When those races occurs and this function makes a | |
493 | * difference vs the standard pmd_none_or_clear_bad, the result is | |
494 | * undefined so behaving like if the pmd was none is safe (because it | |
495 | * can return none anyway). The compiler level barrier() is critically | |
496 | * important to compute the two checks atomically on the same pmdval. | |
26c19178 AA |
497 | * |
498 | * For 32bit kernels with a 64bit large pmd_t this automatically takes | |
499 | * care of reading the pmd atomically to avoid SMP race conditions | |
500 | * against pmd_populate() when the mmap_sem is hold for reading by the | |
501 | * caller (a special atomic read not done by "gcc" as in the generic | |
502 | * version above, is also needed when THP is disabled because the page | |
503 | * fault can populate the pmd from under us). | |
1a5a9906 AA |
504 | */ |
505 | static inline int pmd_none_or_trans_huge_or_clear_bad(pmd_t *pmd) | |
506 | { | |
26c19178 | 507 | pmd_t pmdval = pmd_read_atomic(pmd); |
1a5a9906 AA |
508 | /* |
509 | * The barrier will stabilize the pmdval in a register or on | |
510 | * the stack so that it will stop changing under the code. | |
e4eed03f AA |
511 | * |
512 | * When CONFIG_TRANSPARENT_HUGEPAGE=y on x86 32bit PAE, | |
513 | * pmd_read_atomic is allowed to return a not atomic pmdval | |
514 | * (for example pointing to an hugepage that has never been | |
515 | * mapped in the pmd). The below checks will only care about | |
516 | * the low part of the pmd with 32bit PAE x86 anyway, with the | |
517 | * exception of pmd_none(). So the important thing is that if | |
518 | * the low part of the pmd is found null, the high part will | |
519 | * be also null or the pmd_none() check below would be | |
520 | * confused. | |
1a5a9906 AA |
521 | */ |
522 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE | |
523 | barrier(); | |
524 | #endif | |
525 | if (pmd_none(pmdval)) | |
526 | return 1; | |
527 | if (unlikely(pmd_bad(pmdval))) { | |
528 | if (!pmd_trans_huge(pmdval)) | |
529 | pmd_clear_bad(pmd); | |
530 | return 1; | |
531 | } | |
532 | return 0; | |
533 | } | |
534 | ||
535 | /* | |
536 | * This is a noop if Transparent Hugepage Support is not built into | |
537 | * the kernel. Otherwise it is equivalent to | |
538 | * pmd_none_or_trans_huge_or_clear_bad(), and shall only be called in | |
539 | * places that already verified the pmd is not none and they want to | |
540 | * walk ptes while holding the mmap sem in read mode (write mode don't | |
541 | * need this). If THP is not enabled, the pmd can't go away under the | |
542 | * code even if MADV_DONTNEED runs, but if THP is enabled we need to | |
543 | * run a pmd_trans_unstable before walking the ptes after | |
544 | * split_huge_page_pmd returns (because it may have run when the pmd | |
545 | * become null, but then a page fault can map in a THP and not a | |
546 | * regular page). | |
547 | */ | |
548 | static inline int pmd_trans_unstable(pmd_t *pmd) | |
549 | { | |
550 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE | |
551 | return pmd_none_or_trans_huge_or_clear_bad(pmd); | |
552 | #else | |
553 | return 0; | |
5f6e8da7 | 554 | #endif |
1a5a9906 AA |
555 | } |
556 | ||
557 | #endif /* CONFIG_MMU */ | |
5f6e8da7 | 558 | |
1da177e4 LT |
559 | #endif /* !__ASSEMBLY__ */ |
560 | ||
561 | #endif /* _ASM_GENERIC_PGTABLE_H */ |