Commit | Line | Data |
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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 | ||
1da177e4 | 173 | #ifndef __HAVE_ARCH_PTE_SAME |
e2cda322 AA |
174 | static inline int pte_same(pte_t pte_a, pte_t pte_b) |
175 | { | |
176 | return pte_val(pte_a) == pte_val(pte_b); | |
177 | } | |
178 | #endif | |
179 | ||
180 | #ifndef __HAVE_ARCH_PMD_SAME | |
181 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE | |
182 | static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b) | |
183 | { | |
184 | return pmd_val(pmd_a) == pmd_val(pmd_b); | |
185 | } | |
186 | #else /* CONFIG_TRANSPARENT_HUGEPAGE */ | |
187 | static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b) | |
188 | { | |
189 | BUG(); | |
190 | return 0; | |
191 | } | |
192 | #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ | |
1da177e4 LT |
193 | #endif |
194 | ||
2d42552d MS |
195 | #ifndef __HAVE_ARCH_PAGE_TEST_AND_CLEAR_DIRTY |
196 | #define page_test_and_clear_dirty(pfn, mapped) (0) | |
6c210482 MS |
197 | #endif |
198 | ||
2d42552d | 199 | #ifndef __HAVE_ARCH_PAGE_TEST_AND_CLEAR_DIRTY |
b4955ce3 AK |
200 | #define pte_maybe_dirty(pte) pte_dirty(pte) |
201 | #else | |
202 | #define pte_maybe_dirty(pte) (1) | |
1da177e4 LT |
203 | #endif |
204 | ||
205 | #ifndef __HAVE_ARCH_PAGE_TEST_AND_CLEAR_YOUNG | |
2d42552d | 206 | #define page_test_and_clear_young(pfn) (0) |
1da177e4 LT |
207 | #endif |
208 | ||
209 | #ifndef __HAVE_ARCH_PGD_OFFSET_GATE | |
210 | #define pgd_offset_gate(mm, addr) pgd_offset(mm, addr) | |
211 | #endif | |
212 | ||
0b0968a3 | 213 | #ifndef __HAVE_ARCH_MOVE_PTE |
8b1f3124 | 214 | #define move_pte(pte, prot, old_addr, new_addr) (pte) |
8b1f3124 NP |
215 | #endif |
216 | ||
61c77326 SL |
217 | #ifndef flush_tlb_fix_spurious_fault |
218 | #define flush_tlb_fix_spurious_fault(vma, address) flush_tlb_page(vma, address) | |
219 | #endif | |
220 | ||
0634a632 PM |
221 | #ifndef pgprot_noncached |
222 | #define pgprot_noncached(prot) (prot) | |
223 | #endif | |
224 | ||
2520bd31 | 225 | #ifndef pgprot_writecombine |
226 | #define pgprot_writecombine pgprot_noncached | |
227 | #endif | |
228 | ||
1da177e4 | 229 | /* |
8f6c99c1 HD |
230 | * When walking page tables, get the address of the next boundary, |
231 | * or the end address of the range if that comes earlier. Although no | |
232 | * vma end wraps to 0, rounded up __boundary may wrap to 0 throughout. | |
1da177e4 LT |
233 | */ |
234 | ||
1da177e4 LT |
235 | #define pgd_addr_end(addr, end) \ |
236 | ({ unsigned long __boundary = ((addr) + PGDIR_SIZE) & PGDIR_MASK; \ | |
237 | (__boundary - 1 < (end) - 1)? __boundary: (end); \ | |
238 | }) | |
1da177e4 LT |
239 | |
240 | #ifndef pud_addr_end | |
241 | #define pud_addr_end(addr, end) \ | |
242 | ({ unsigned long __boundary = ((addr) + PUD_SIZE) & PUD_MASK; \ | |
243 | (__boundary - 1 < (end) - 1)? __boundary: (end); \ | |
244 | }) | |
245 | #endif | |
246 | ||
247 | #ifndef pmd_addr_end | |
248 | #define pmd_addr_end(addr, end) \ | |
249 | ({ unsigned long __boundary = ((addr) + PMD_SIZE) & PMD_MASK; \ | |
250 | (__boundary - 1 < (end) - 1)? __boundary: (end); \ | |
251 | }) | |
252 | #endif | |
253 | ||
1da177e4 LT |
254 | /* |
255 | * When walking page tables, we usually want to skip any p?d_none entries; | |
256 | * and any p?d_bad entries - reporting the error before resetting to none. | |
257 | * Do the tests inline, but report and clear the bad entry in mm/memory.c. | |
258 | */ | |
259 | void pgd_clear_bad(pgd_t *); | |
260 | void pud_clear_bad(pud_t *); | |
261 | void pmd_clear_bad(pmd_t *); | |
262 | ||
263 | static inline int pgd_none_or_clear_bad(pgd_t *pgd) | |
264 | { | |
265 | if (pgd_none(*pgd)) | |
266 | return 1; | |
267 | if (unlikely(pgd_bad(*pgd))) { | |
268 | pgd_clear_bad(pgd); | |
269 | return 1; | |
270 | } | |
271 | return 0; | |
272 | } | |
273 | ||
274 | static inline int pud_none_or_clear_bad(pud_t *pud) | |
275 | { | |
276 | if (pud_none(*pud)) | |
277 | return 1; | |
278 | if (unlikely(pud_bad(*pud))) { | |
279 | pud_clear_bad(pud); | |
280 | return 1; | |
281 | } | |
282 | return 0; | |
283 | } | |
284 | ||
285 | static inline int pmd_none_or_clear_bad(pmd_t *pmd) | |
286 | { | |
287 | if (pmd_none(*pmd)) | |
288 | return 1; | |
289 | if (unlikely(pmd_bad(*pmd))) { | |
290 | pmd_clear_bad(pmd); | |
291 | return 1; | |
292 | } | |
293 | return 0; | |
294 | } | |
9535239f | 295 | |
1ea0704e JF |
296 | static inline pte_t __ptep_modify_prot_start(struct mm_struct *mm, |
297 | unsigned long addr, | |
298 | pte_t *ptep) | |
299 | { | |
300 | /* | |
301 | * Get the current pte state, but zero it out to make it | |
302 | * non-present, preventing the hardware from asynchronously | |
303 | * updating it. | |
304 | */ | |
305 | return ptep_get_and_clear(mm, addr, ptep); | |
306 | } | |
307 | ||
308 | static inline void __ptep_modify_prot_commit(struct mm_struct *mm, | |
309 | unsigned long addr, | |
310 | pte_t *ptep, pte_t pte) | |
311 | { | |
312 | /* | |
313 | * The pte is non-present, so there's no hardware state to | |
314 | * preserve. | |
315 | */ | |
316 | set_pte_at(mm, addr, ptep, pte); | |
317 | } | |
318 | ||
319 | #ifndef __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION | |
320 | /* | |
321 | * Start a pte protection read-modify-write transaction, which | |
322 | * protects against asynchronous hardware modifications to the pte. | |
323 | * The intention is not to prevent the hardware from making pte | |
324 | * updates, but to prevent any updates it may make from being lost. | |
325 | * | |
326 | * This does not protect against other software modifications of the | |
327 | * pte; the appropriate pte lock must be held over the transation. | |
328 | * | |
329 | * Note that this interface is intended to be batchable, meaning that | |
330 | * ptep_modify_prot_commit may not actually update the pte, but merely | |
331 | * queue the update to be done at some later time. The update must be | |
332 | * actually committed before the pte lock is released, however. | |
333 | */ | |
334 | static inline pte_t ptep_modify_prot_start(struct mm_struct *mm, | |
335 | unsigned long addr, | |
336 | pte_t *ptep) | |
337 | { | |
338 | return __ptep_modify_prot_start(mm, addr, ptep); | |
339 | } | |
340 | ||
341 | /* | |
342 | * Commit an update to a pte, leaving any hardware-controlled bits in | |
343 | * the PTE unmodified. | |
344 | */ | |
345 | static inline void ptep_modify_prot_commit(struct mm_struct *mm, | |
346 | unsigned long addr, | |
347 | pte_t *ptep, pte_t pte) | |
348 | { | |
349 | __ptep_modify_prot_commit(mm, addr, ptep, pte); | |
350 | } | |
351 | #endif /* __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION */ | |
fe1a6875 | 352 | #endif /* CONFIG_MMU */ |
1ea0704e | 353 | |
9535239f GU |
354 | /* |
355 | * A facility to provide lazy MMU batching. This allows PTE updates and | |
356 | * page invalidations to be delayed until a call to leave lazy MMU mode | |
357 | * is issued. Some architectures may benefit from doing this, and it is | |
358 | * beneficial for both shadow and direct mode hypervisors, which may batch | |
359 | * the PTE updates which happen during this window. Note that using this | |
360 | * interface requires that read hazards be removed from the code. A read | |
361 | * hazard could result in the direct mode hypervisor case, since the actual | |
362 | * write to the page tables may not yet have taken place, so reads though | |
363 | * a raw PTE pointer after it has been modified are not guaranteed to be | |
364 | * up to date. This mode can only be entered and left under the protection of | |
365 | * the page table locks for all page tables which may be modified. In the UP | |
366 | * case, this is required so that preemption is disabled, and in the SMP case, | |
367 | * it must synchronize the delayed page table writes properly on other CPUs. | |
368 | */ | |
369 | #ifndef __HAVE_ARCH_ENTER_LAZY_MMU_MODE | |
370 | #define arch_enter_lazy_mmu_mode() do {} while (0) | |
371 | #define arch_leave_lazy_mmu_mode() do {} while (0) | |
372 | #define arch_flush_lazy_mmu_mode() do {} while (0) | |
373 | #endif | |
374 | ||
375 | /* | |
7fd7d83d JF |
376 | * A facility to provide batching of the reload of page tables and |
377 | * other process state with the actual context switch code for | |
378 | * paravirtualized guests. By convention, only one of the batched | |
379 | * update (lazy) modes (CPU, MMU) should be active at any given time, | |
380 | * entry should never be nested, and entry and exits should always be | |
381 | * paired. This is for sanity of maintaining and reasoning about the | |
382 | * kernel code. In this case, the exit (end of the context switch) is | |
383 | * in architecture-specific code, and so doesn't need a generic | |
384 | * definition. | |
9535239f | 385 | */ |
7fd7d83d | 386 | #ifndef __HAVE_ARCH_START_CONTEXT_SWITCH |
224101ed | 387 | #define arch_start_context_switch(prev) do {} while (0) |
9535239f GU |
388 | #endif |
389 | ||
34801ba9 | 390 | #ifndef __HAVE_PFNMAP_TRACKING |
391 | /* | |
5180da41 SS |
392 | * Interfaces that can be used by architecture code to keep track of |
393 | * memory type of pfn mappings specified by the remap_pfn_range, | |
394 | * vm_insert_pfn. | |
395 | */ | |
396 | ||
397 | /* | |
398 | * track_pfn_remap is called when a _new_ pfn mapping is being established | |
399 | * by remap_pfn_range() for physical range indicated by pfn and size. | |
34801ba9 | 400 | */ |
5180da41 | 401 | static inline int track_pfn_remap(struct vm_area_struct *vma, pgprot_t *prot, |
b3b9c293 KK |
402 | unsigned long pfn, unsigned long addr, |
403 | unsigned long size) | |
34801ba9 | 404 | { |
405 | return 0; | |
406 | } | |
407 | ||
408 | /* | |
5180da41 SS |
409 | * track_pfn_insert is called when a _new_ single pfn is established |
410 | * by vm_insert_pfn(). | |
411 | */ | |
412 | static inline int track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot, | |
413 | unsigned long pfn) | |
414 | { | |
415 | return 0; | |
416 | } | |
417 | ||
418 | /* | |
419 | * track_pfn_copy is called when vma that is covering the pfnmap gets | |
34801ba9 | 420 | * copied through copy_page_range(). |
421 | */ | |
5180da41 | 422 | static inline int track_pfn_copy(struct vm_area_struct *vma) |
34801ba9 | 423 | { |
424 | return 0; | |
425 | } | |
426 | ||
427 | /* | |
34801ba9 | 428 | * untrack_pfn_vma is called while unmapping a pfnmap for a region. |
429 | * untrack can be called for a specific region indicated by pfn and size or | |
5180da41 | 430 | * can be for the entire vma (in which case pfn, size are zero). |
34801ba9 | 431 | */ |
5180da41 SS |
432 | static inline void untrack_pfn(struct vm_area_struct *vma, |
433 | unsigned long pfn, unsigned long size) | |
34801ba9 | 434 | { |
435 | } | |
436 | #else | |
5180da41 | 437 | extern int track_pfn_remap(struct vm_area_struct *vma, pgprot_t *prot, |
b3b9c293 KK |
438 | unsigned long pfn, unsigned long addr, |
439 | unsigned long size); | |
5180da41 SS |
440 | extern int track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot, |
441 | unsigned long pfn); | |
442 | extern int track_pfn_copy(struct vm_area_struct *vma); | |
443 | extern void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn, | |
444 | unsigned long size); | |
34801ba9 | 445 | #endif |
446 | ||
1a5a9906 AA |
447 | #ifdef CONFIG_MMU |
448 | ||
5f6e8da7 AA |
449 | #ifndef CONFIG_TRANSPARENT_HUGEPAGE |
450 | static inline int pmd_trans_huge(pmd_t pmd) | |
451 | { | |
452 | return 0; | |
453 | } | |
454 | static inline int pmd_trans_splitting(pmd_t pmd) | |
455 | { | |
456 | return 0; | |
457 | } | |
e2cda322 AA |
458 | #ifndef __HAVE_ARCH_PMD_WRITE |
459 | static inline int pmd_write(pmd_t pmd) | |
460 | { | |
461 | BUG(); | |
462 | return 0; | |
463 | } | |
464 | #endif /* __HAVE_ARCH_PMD_WRITE */ | |
1a5a9906 AA |
465 | #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ |
466 | ||
26c19178 AA |
467 | #ifndef pmd_read_atomic |
468 | static inline pmd_t pmd_read_atomic(pmd_t *pmdp) | |
469 | { | |
470 | /* | |
471 | * Depend on compiler for an atomic pmd read. NOTE: this is | |
472 | * only going to work, if the pmdval_t isn't larger than | |
473 | * an unsigned long. | |
474 | */ | |
475 | return *pmdp; | |
476 | } | |
477 | #endif | |
478 | ||
1a5a9906 AA |
479 | /* |
480 | * This function is meant to be used by sites walking pagetables with | |
481 | * the mmap_sem hold in read mode to protect against MADV_DONTNEED and | |
482 | * transhuge page faults. MADV_DONTNEED can convert a transhuge pmd | |
483 | * into a null pmd and the transhuge page fault can convert a null pmd | |
484 | * into an hugepmd or into a regular pmd (if the hugepage allocation | |
485 | * fails). While holding the mmap_sem in read mode the pmd becomes | |
486 | * stable and stops changing under us only if it's not null and not a | |
487 | * transhuge pmd. When those races occurs and this function makes a | |
488 | * difference vs the standard pmd_none_or_clear_bad, the result is | |
489 | * undefined so behaving like if the pmd was none is safe (because it | |
490 | * can return none anyway). The compiler level barrier() is critically | |
491 | * important to compute the two checks atomically on the same pmdval. | |
26c19178 AA |
492 | * |
493 | * For 32bit kernels with a 64bit large pmd_t this automatically takes | |
494 | * care of reading the pmd atomically to avoid SMP race conditions | |
495 | * against pmd_populate() when the mmap_sem is hold for reading by the | |
496 | * caller (a special atomic read not done by "gcc" as in the generic | |
497 | * version above, is also needed when THP is disabled because the page | |
498 | * fault can populate the pmd from under us). | |
1a5a9906 AA |
499 | */ |
500 | static inline int pmd_none_or_trans_huge_or_clear_bad(pmd_t *pmd) | |
501 | { | |
26c19178 | 502 | pmd_t pmdval = pmd_read_atomic(pmd); |
1a5a9906 AA |
503 | /* |
504 | * The barrier will stabilize the pmdval in a register or on | |
505 | * the stack so that it will stop changing under the code. | |
e4eed03f AA |
506 | * |
507 | * When CONFIG_TRANSPARENT_HUGEPAGE=y on x86 32bit PAE, | |
508 | * pmd_read_atomic is allowed to return a not atomic pmdval | |
509 | * (for example pointing to an hugepage that has never been | |
510 | * mapped in the pmd). The below checks will only care about | |
511 | * the low part of the pmd with 32bit PAE x86 anyway, with the | |
512 | * exception of pmd_none(). So the important thing is that if | |
513 | * the low part of the pmd is found null, the high part will | |
514 | * be also null or the pmd_none() check below would be | |
515 | * confused. | |
1a5a9906 AA |
516 | */ |
517 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE | |
518 | barrier(); | |
519 | #endif | |
520 | if (pmd_none(pmdval)) | |
521 | return 1; | |
522 | if (unlikely(pmd_bad(pmdval))) { | |
523 | if (!pmd_trans_huge(pmdval)) | |
524 | pmd_clear_bad(pmd); | |
525 | return 1; | |
526 | } | |
527 | return 0; | |
528 | } | |
529 | ||
530 | /* | |
531 | * This is a noop if Transparent Hugepage Support is not built into | |
532 | * the kernel. Otherwise it is equivalent to | |
533 | * pmd_none_or_trans_huge_or_clear_bad(), and shall only be called in | |
534 | * places that already verified the pmd is not none and they want to | |
535 | * walk ptes while holding the mmap sem in read mode (write mode don't | |
536 | * need this). If THP is not enabled, the pmd can't go away under the | |
537 | * code even if MADV_DONTNEED runs, but if THP is enabled we need to | |
538 | * run a pmd_trans_unstable before walking the ptes after | |
539 | * split_huge_page_pmd returns (because it may have run when the pmd | |
540 | * become null, but then a page fault can map in a THP and not a | |
541 | * regular page). | |
542 | */ | |
543 | static inline int pmd_trans_unstable(pmd_t *pmd) | |
544 | { | |
545 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE | |
546 | return pmd_none_or_trans_huge_or_clear_bad(pmd); | |
547 | #else | |
548 | return 0; | |
5f6e8da7 | 549 | #endif |
1a5a9906 AA |
550 | } |
551 | ||
552 | #endif /* CONFIG_MMU */ | |
5f6e8da7 | 553 | |
1da177e4 LT |
554 | #endif /* !__ASSEMBLY__ */ |
555 | ||
556 | #endif /* _ASM_GENERIC_PGTABLE_H */ |