xref: /openbmc/linux/mm/memory.c (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
1 /*
2  *  linux/mm/memory.c
3  *
4  *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
5  */
6 
7 /*
8  * demand-loading started 01.12.91 - seems it is high on the list of
9  * things wanted, and it should be easy to implement. - Linus
10  */
11 
12 /*
13  * Ok, demand-loading was easy, shared pages a little bit tricker. Shared
14  * pages started 02.12.91, seems to work. - Linus.
15  *
16  * Tested sharing by executing about 30 /bin/sh: under the old kernel it
17  * would have taken more than the 6M I have free, but it worked well as
18  * far as I could see.
19  *
20  * Also corrected some "invalidate()"s - I wasn't doing enough of them.
21  */
22 
23 /*
24  * Real VM (paging to/from disk) started 18.12.91. Much more work and
25  * thought has to go into this. Oh, well..
26  * 19.12.91  -  works, somewhat. Sometimes I get faults, don't know why.
27  *		Found it. Everything seems to work now.
28  * 20.12.91  -  Ok, making the swap-device changeable like the root.
29  */
30 
31 /*
32  * 05.04.94  -  Multi-page memory management added for v1.1.
33  * 		Idea by Alex Bligh (alex@cconcepts.co.uk)
34  *
35  * 16.07.99  -  Support of BIGMEM added by Gerhard Wichert, Siemens AG
36  *		(Gerhard.Wichert@pdb.siemens.de)
37  *
38  * Aug/Sep 2004 Changed to four level page tables (Andi Kleen)
39  */
40 
41 #include <linux/kernel_stat.h>
42 #include <linux/mm.h>
43 #include <linux/hugetlb.h>
44 #include <linux/mman.h>
45 #include <linux/swap.h>
46 #include <linux/highmem.h>
47 #include <linux/pagemap.h>
48 #include <linux/rmap.h>
49 #include <linux/module.h>
50 #include <linux/init.h>
51 
52 #include <asm/pgalloc.h>
53 #include <asm/uaccess.h>
54 #include <asm/tlb.h>
55 #include <asm/tlbflush.h>
56 #include <asm/pgtable.h>
57 
58 #include <linux/swapops.h>
59 #include <linux/elf.h>
60 
61 #ifndef CONFIG_NEED_MULTIPLE_NODES
62 /* use the per-pgdat data instead for discontigmem - mbligh */
63 unsigned long max_mapnr;
64 struct page *mem_map;
65 
66 EXPORT_SYMBOL(max_mapnr);
67 EXPORT_SYMBOL(mem_map);
68 #endif
69 
70 unsigned long num_physpages;
71 /*
72  * A number of key systems in x86 including ioremap() rely on the assumption
73  * that high_memory defines the upper bound on direct map memory, then end
74  * of ZONE_NORMAL.  Under CONFIG_DISCONTIG this means that max_low_pfn and
75  * highstart_pfn must be the same; there must be no gap between ZONE_NORMAL
76  * and ZONE_HIGHMEM.
77  */
78 void * high_memory;
79 unsigned long vmalloc_earlyreserve;
80 
81 EXPORT_SYMBOL(num_physpages);
82 EXPORT_SYMBOL(high_memory);
83 EXPORT_SYMBOL(vmalloc_earlyreserve);
84 
85 /*
86  * If a p?d_bad entry is found while walking page tables, report
87  * the error, before resetting entry to p?d_none.  Usually (but
88  * very seldom) called out from the p?d_none_or_clear_bad macros.
89  */
90 
91 void pgd_clear_bad(pgd_t *pgd)
92 {
93 	pgd_ERROR(*pgd);
94 	pgd_clear(pgd);
95 }
96 
97 void pud_clear_bad(pud_t *pud)
98 {
99 	pud_ERROR(*pud);
100 	pud_clear(pud);
101 }
102 
103 void pmd_clear_bad(pmd_t *pmd)
104 {
105 	pmd_ERROR(*pmd);
106 	pmd_clear(pmd);
107 }
108 
109 /*
110  * Note: this doesn't free the actual pages themselves. That
111  * has been handled earlier when unmapping all the memory regions.
112  */
113 static void free_pte_range(struct mmu_gather *tlb, pmd_t *pmd)
114 {
115 	struct page *page = pmd_page(*pmd);
116 	pmd_clear(pmd);
117 	pte_lock_deinit(page);
118 	pte_free_tlb(tlb, page);
119 	dec_page_state(nr_page_table_pages);
120 	tlb->mm->nr_ptes--;
121 }
122 
123 static inline void free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
124 				unsigned long addr, unsigned long end,
125 				unsigned long floor, unsigned long ceiling)
126 {
127 	pmd_t *pmd;
128 	unsigned long next;
129 	unsigned long start;
130 
131 	start = addr;
132 	pmd = pmd_offset(pud, addr);
133 	do {
134 		next = pmd_addr_end(addr, end);
135 		if (pmd_none_or_clear_bad(pmd))
136 			continue;
137 		free_pte_range(tlb, pmd);
138 	} while (pmd++, addr = next, addr != end);
139 
140 	start &= PUD_MASK;
141 	if (start < floor)
142 		return;
143 	if (ceiling) {
144 		ceiling &= PUD_MASK;
145 		if (!ceiling)
146 			return;
147 	}
148 	if (end - 1 > ceiling - 1)
149 		return;
150 
151 	pmd = pmd_offset(pud, start);
152 	pud_clear(pud);
153 	pmd_free_tlb(tlb, pmd);
154 }
155 
156 static inline void free_pud_range(struct mmu_gather *tlb, pgd_t *pgd,
157 				unsigned long addr, unsigned long end,
158 				unsigned long floor, unsigned long ceiling)
159 {
160 	pud_t *pud;
161 	unsigned long next;
162 	unsigned long start;
163 
164 	start = addr;
165 	pud = pud_offset(pgd, addr);
166 	do {
167 		next = pud_addr_end(addr, end);
168 		if (pud_none_or_clear_bad(pud))
169 			continue;
170 		free_pmd_range(tlb, pud, addr, next, floor, ceiling);
171 	} while (pud++, addr = next, addr != end);
172 
173 	start &= PGDIR_MASK;
174 	if (start < floor)
175 		return;
176 	if (ceiling) {
177 		ceiling &= PGDIR_MASK;
178 		if (!ceiling)
179 			return;
180 	}
181 	if (end - 1 > ceiling - 1)
182 		return;
183 
184 	pud = pud_offset(pgd, start);
185 	pgd_clear(pgd);
186 	pud_free_tlb(tlb, pud);
187 }
188 
189 /*
190  * This function frees user-level page tables of a process.
191  *
192  * Must be called with pagetable lock held.
193  */
194 void free_pgd_range(struct mmu_gather **tlb,
195 			unsigned long addr, unsigned long end,
196 			unsigned long floor, unsigned long ceiling)
197 {
198 	pgd_t *pgd;
199 	unsigned long next;
200 	unsigned long start;
201 
202 	/*
203 	 * The next few lines have given us lots of grief...
204 	 *
205 	 * Why are we testing PMD* at this top level?  Because often
206 	 * there will be no work to do at all, and we'd prefer not to
207 	 * go all the way down to the bottom just to discover that.
208 	 *
209 	 * Why all these "- 1"s?  Because 0 represents both the bottom
210 	 * of the address space and the top of it (using -1 for the
211 	 * top wouldn't help much: the masks would do the wrong thing).
212 	 * The rule is that addr 0 and floor 0 refer to the bottom of
213 	 * the address space, but end 0 and ceiling 0 refer to the top
214 	 * Comparisons need to use "end - 1" and "ceiling - 1" (though
215 	 * that end 0 case should be mythical).
216 	 *
217 	 * Wherever addr is brought up or ceiling brought down, we must
218 	 * be careful to reject "the opposite 0" before it confuses the
219 	 * subsequent tests.  But what about where end is brought down
220 	 * by PMD_SIZE below? no, end can't go down to 0 there.
221 	 *
222 	 * Whereas we round start (addr) and ceiling down, by different
223 	 * masks at different levels, in order to test whether a table
224 	 * now has no other vmas using it, so can be freed, we don't
225 	 * bother to round floor or end up - the tests don't need that.
226 	 */
227 
228 	addr &= PMD_MASK;
229 	if (addr < floor) {
230 		addr += PMD_SIZE;
231 		if (!addr)
232 			return;
233 	}
234 	if (ceiling) {
235 		ceiling &= PMD_MASK;
236 		if (!ceiling)
237 			return;
238 	}
239 	if (end - 1 > ceiling - 1)
240 		end -= PMD_SIZE;
241 	if (addr > end - 1)
242 		return;
243 
244 	start = addr;
245 	pgd = pgd_offset((*tlb)->mm, addr);
246 	do {
247 		next = pgd_addr_end(addr, end);
248 		if (pgd_none_or_clear_bad(pgd))
249 			continue;
250 		free_pud_range(*tlb, pgd, addr, next, floor, ceiling);
251 	} while (pgd++, addr = next, addr != end);
252 
253 	if (!(*tlb)->fullmm)
254 		flush_tlb_pgtables((*tlb)->mm, start, end);
255 }
256 
257 void free_pgtables(struct mmu_gather **tlb, struct vm_area_struct *vma,
258 		unsigned long floor, unsigned long ceiling)
259 {
260 	while (vma) {
261 		struct vm_area_struct *next = vma->vm_next;
262 		unsigned long addr = vma->vm_start;
263 
264 		/*
265 		 * Hide vma from rmap and vmtruncate before freeing pgtables
266 		 */
267 		anon_vma_unlink(vma);
268 		unlink_file_vma(vma);
269 
270 		if (is_hugepage_only_range(vma->vm_mm, addr, HPAGE_SIZE)) {
271 			hugetlb_free_pgd_range(tlb, addr, vma->vm_end,
272 				floor, next? next->vm_start: ceiling);
273 		} else {
274 			/*
275 			 * Optimization: gather nearby vmas into one call down
276 			 */
277 			while (next && next->vm_start <= vma->vm_end + PMD_SIZE
278 			  && !is_hugepage_only_range(vma->vm_mm, next->vm_start,
279 							HPAGE_SIZE)) {
280 				vma = next;
281 				next = vma->vm_next;
282 				anon_vma_unlink(vma);
283 				unlink_file_vma(vma);
284 			}
285 			free_pgd_range(tlb, addr, vma->vm_end,
286 				floor, next? next->vm_start: ceiling);
287 		}
288 		vma = next;
289 	}
290 }
291 
292 int __pte_alloc(struct mm_struct *mm, pmd_t *pmd, unsigned long address)
293 {
294 	struct page *new = pte_alloc_one(mm, address);
295 	if (!new)
296 		return -ENOMEM;
297 
298 	pte_lock_init(new);
299 	spin_lock(&mm->page_table_lock);
300 	if (pmd_present(*pmd)) {	/* Another has populated it */
301 		pte_lock_deinit(new);
302 		pte_free(new);
303 	} else {
304 		mm->nr_ptes++;
305 		inc_page_state(nr_page_table_pages);
306 		pmd_populate(mm, pmd, new);
307 	}
308 	spin_unlock(&mm->page_table_lock);
309 	return 0;
310 }
311 
312 int __pte_alloc_kernel(pmd_t *pmd, unsigned long address)
313 {
314 	pte_t *new = pte_alloc_one_kernel(&init_mm, address);
315 	if (!new)
316 		return -ENOMEM;
317 
318 	spin_lock(&init_mm.page_table_lock);
319 	if (pmd_present(*pmd))		/* Another has populated it */
320 		pte_free_kernel(new);
321 	else
322 		pmd_populate_kernel(&init_mm, pmd, new);
323 	spin_unlock(&init_mm.page_table_lock);
324 	return 0;
325 }
326 
327 static inline void add_mm_rss(struct mm_struct *mm, int file_rss, int anon_rss)
328 {
329 	if (file_rss)
330 		add_mm_counter(mm, file_rss, file_rss);
331 	if (anon_rss)
332 		add_mm_counter(mm, anon_rss, anon_rss);
333 }
334 
335 /*
336  * This function is called to print an error when a pte in a
337  * !VM_RESERVED region is found pointing to an invalid pfn (which
338  * is an error.
339  *
340  * The calling function must still handle the error.
341  */
342 void print_bad_pte(struct vm_area_struct *vma, pte_t pte, unsigned long vaddr)
343 {
344 	printk(KERN_ERR "Bad pte = %08llx, process = %s, "
345 			"vm_flags = %lx, vaddr = %lx\n",
346 		(long long)pte_val(pte),
347 		(vma->vm_mm == current->mm ? current->comm : "???"),
348 		vma->vm_flags, vaddr);
349 	dump_stack();
350 }
351 
352 /*
353  * copy one vm_area from one task to the other. Assumes the page tables
354  * already present in the new task to be cleared in the whole range
355  * covered by this vma.
356  */
357 
358 static inline void
359 copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
360 		pte_t *dst_pte, pte_t *src_pte, struct vm_area_struct *vma,
361 		unsigned long addr, int *rss)
362 {
363 	unsigned long vm_flags = vma->vm_flags;
364 	pte_t pte = *src_pte;
365 	struct page *page;
366 	unsigned long pfn;
367 
368 	/* pte contains position in swap or file, so copy. */
369 	if (unlikely(!pte_present(pte))) {
370 		if (!pte_file(pte)) {
371 			swap_duplicate(pte_to_swp_entry(pte));
372 			/* make sure dst_mm is on swapoff's mmlist. */
373 			if (unlikely(list_empty(&dst_mm->mmlist))) {
374 				spin_lock(&mmlist_lock);
375 				if (list_empty(&dst_mm->mmlist))
376 					list_add(&dst_mm->mmlist,
377 						 &src_mm->mmlist);
378 				spin_unlock(&mmlist_lock);
379 			}
380 		}
381 		goto out_set_pte;
382 	}
383 
384 	/* If the region is VM_RESERVED, the mapping is not
385 	 * mapped via rmap - duplicate the pte as is.
386 	 */
387 	if (vm_flags & VM_RESERVED)
388 		goto out_set_pte;
389 
390 	pfn = pte_pfn(pte);
391 	/* If the pte points outside of valid memory but
392 	 * the region is not VM_RESERVED, we have a problem.
393 	 */
394 	if (unlikely(!pfn_valid(pfn))) {
395 		print_bad_pte(vma, pte, addr);
396 		goto out_set_pte; /* try to do something sane */
397 	}
398 
399 	page = pfn_to_page(pfn);
400 
401 	/*
402 	 * If it's a COW mapping, write protect it both
403 	 * in the parent and the child
404 	 */
405 	if ((vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE) {
406 		ptep_set_wrprotect(src_mm, addr, src_pte);
407 		pte = *src_pte;
408 	}
409 
410 	/*
411 	 * If it's a shared mapping, mark it clean in
412 	 * the child
413 	 */
414 	if (vm_flags & VM_SHARED)
415 		pte = pte_mkclean(pte);
416 	pte = pte_mkold(pte);
417 	get_page(page);
418 	page_dup_rmap(page);
419 	rss[!!PageAnon(page)]++;
420 
421 out_set_pte:
422 	set_pte_at(dst_mm, addr, dst_pte, pte);
423 }
424 
425 static int copy_pte_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
426 		pmd_t *dst_pmd, pmd_t *src_pmd, struct vm_area_struct *vma,
427 		unsigned long addr, unsigned long end)
428 {
429 	pte_t *src_pte, *dst_pte;
430 	spinlock_t *src_ptl, *dst_ptl;
431 	int progress = 0;
432 	int rss[2];
433 
434 again:
435 	rss[1] = rss[0] = 0;
436 	dst_pte = pte_alloc_map_lock(dst_mm, dst_pmd, addr, &dst_ptl);
437 	if (!dst_pte)
438 		return -ENOMEM;
439 	src_pte = pte_offset_map_nested(src_pmd, addr);
440 	src_ptl = pte_lockptr(src_mm, src_pmd);
441 	spin_lock(src_ptl);
442 
443 	do {
444 		/*
445 		 * We are holding two locks at this point - either of them
446 		 * could generate latencies in another task on another CPU.
447 		 */
448 		if (progress >= 32) {
449 			progress = 0;
450 			if (need_resched() ||
451 			    need_lockbreak(src_ptl) ||
452 			    need_lockbreak(dst_ptl))
453 				break;
454 		}
455 		if (pte_none(*src_pte)) {
456 			progress++;
457 			continue;
458 		}
459 		copy_one_pte(dst_mm, src_mm, dst_pte, src_pte, vma, addr, rss);
460 		progress += 8;
461 	} while (dst_pte++, src_pte++, addr += PAGE_SIZE, addr != end);
462 
463 	spin_unlock(src_ptl);
464 	pte_unmap_nested(src_pte - 1);
465 	add_mm_rss(dst_mm, rss[0], rss[1]);
466 	pte_unmap_unlock(dst_pte - 1, dst_ptl);
467 	cond_resched();
468 	if (addr != end)
469 		goto again;
470 	return 0;
471 }
472 
473 static inline int copy_pmd_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
474 		pud_t *dst_pud, pud_t *src_pud, struct vm_area_struct *vma,
475 		unsigned long addr, unsigned long end)
476 {
477 	pmd_t *src_pmd, *dst_pmd;
478 	unsigned long next;
479 
480 	dst_pmd = pmd_alloc(dst_mm, dst_pud, addr);
481 	if (!dst_pmd)
482 		return -ENOMEM;
483 	src_pmd = pmd_offset(src_pud, addr);
484 	do {
485 		next = pmd_addr_end(addr, end);
486 		if (pmd_none_or_clear_bad(src_pmd))
487 			continue;
488 		if (copy_pte_range(dst_mm, src_mm, dst_pmd, src_pmd,
489 						vma, addr, next))
490 			return -ENOMEM;
491 	} while (dst_pmd++, src_pmd++, addr = next, addr != end);
492 	return 0;
493 }
494 
495 static inline int copy_pud_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
496 		pgd_t *dst_pgd, pgd_t *src_pgd, struct vm_area_struct *vma,
497 		unsigned long addr, unsigned long end)
498 {
499 	pud_t *src_pud, *dst_pud;
500 	unsigned long next;
501 
502 	dst_pud = pud_alloc(dst_mm, dst_pgd, addr);
503 	if (!dst_pud)
504 		return -ENOMEM;
505 	src_pud = pud_offset(src_pgd, addr);
506 	do {
507 		next = pud_addr_end(addr, end);
508 		if (pud_none_or_clear_bad(src_pud))
509 			continue;
510 		if (copy_pmd_range(dst_mm, src_mm, dst_pud, src_pud,
511 						vma, addr, next))
512 			return -ENOMEM;
513 	} while (dst_pud++, src_pud++, addr = next, addr != end);
514 	return 0;
515 }
516 
517 int copy_page_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
518 		struct vm_area_struct *vma)
519 {
520 	pgd_t *src_pgd, *dst_pgd;
521 	unsigned long next;
522 	unsigned long addr = vma->vm_start;
523 	unsigned long end = vma->vm_end;
524 
525 	/*
526 	 * Don't copy ptes where a page fault will fill them correctly.
527 	 * Fork becomes much lighter when there are big shared or private
528 	 * readonly mappings. The tradeoff is that copy_page_range is more
529 	 * efficient than faulting.
530 	 */
531 	if (!(vma->vm_flags & (VM_HUGETLB|VM_NONLINEAR|VM_RESERVED))) {
532 		if (!vma->anon_vma)
533 			return 0;
534 	}
535 
536 	if (is_vm_hugetlb_page(vma))
537 		return copy_hugetlb_page_range(dst_mm, src_mm, vma);
538 
539 	dst_pgd = pgd_offset(dst_mm, addr);
540 	src_pgd = pgd_offset(src_mm, addr);
541 	do {
542 		next = pgd_addr_end(addr, end);
543 		if (pgd_none_or_clear_bad(src_pgd))
544 			continue;
545 		if (copy_pud_range(dst_mm, src_mm, dst_pgd, src_pgd,
546 						vma, addr, next))
547 			return -ENOMEM;
548 	} while (dst_pgd++, src_pgd++, addr = next, addr != end);
549 	return 0;
550 }
551 
552 static void zap_pte_range(struct mmu_gather *tlb,
553 				struct vm_area_struct *vma, pmd_t *pmd,
554 				unsigned long addr, unsigned long end,
555 				struct zap_details *details)
556 {
557 	struct mm_struct *mm = tlb->mm;
558 	pte_t *pte;
559 	spinlock_t *ptl;
560 	int file_rss = 0;
561 	int anon_rss = 0;
562 
563 	pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
564 	do {
565 		pte_t ptent = *pte;
566 		if (pte_none(ptent))
567 			continue;
568 		if (pte_present(ptent)) {
569 			struct page *page = NULL;
570 			if (!(vma->vm_flags & VM_RESERVED)) {
571 				unsigned long pfn = pte_pfn(ptent);
572 				if (unlikely(!pfn_valid(pfn)))
573 					print_bad_pte(vma, ptent, addr);
574 				else
575 					page = pfn_to_page(pfn);
576 			}
577 			if (unlikely(details) && page) {
578 				/*
579 				 * unmap_shared_mapping_pages() wants to
580 				 * invalidate cache without truncating:
581 				 * unmap shared but keep private pages.
582 				 */
583 				if (details->check_mapping &&
584 				    details->check_mapping != page->mapping)
585 					continue;
586 				/*
587 				 * Each page->index must be checked when
588 				 * invalidating or truncating nonlinear.
589 				 */
590 				if (details->nonlinear_vma &&
591 				    (page->index < details->first_index ||
592 				     page->index > details->last_index))
593 					continue;
594 			}
595 			ptent = ptep_get_and_clear_full(mm, addr, pte,
596 							tlb->fullmm);
597 			tlb_remove_tlb_entry(tlb, pte, addr);
598 			if (unlikely(!page))
599 				continue;
600 			if (unlikely(details) && details->nonlinear_vma
601 			    && linear_page_index(details->nonlinear_vma,
602 						addr) != page->index)
603 				set_pte_at(mm, addr, pte,
604 					   pgoff_to_pte(page->index));
605 			if (PageAnon(page))
606 				anon_rss--;
607 			else {
608 				if (pte_dirty(ptent))
609 					set_page_dirty(page);
610 				if (pte_young(ptent))
611 					mark_page_accessed(page);
612 				file_rss--;
613 			}
614 			page_remove_rmap(page);
615 			tlb_remove_page(tlb, page);
616 			continue;
617 		}
618 		/*
619 		 * If details->check_mapping, we leave swap entries;
620 		 * if details->nonlinear_vma, we leave file entries.
621 		 */
622 		if (unlikely(details))
623 			continue;
624 		if (!pte_file(ptent))
625 			free_swap_and_cache(pte_to_swp_entry(ptent));
626 		pte_clear_full(mm, addr, pte, tlb->fullmm);
627 	} while (pte++, addr += PAGE_SIZE, addr != end);
628 
629 	add_mm_rss(mm, file_rss, anon_rss);
630 	pte_unmap_unlock(pte - 1, ptl);
631 }
632 
633 static inline void zap_pmd_range(struct mmu_gather *tlb,
634 				struct vm_area_struct *vma, pud_t *pud,
635 				unsigned long addr, unsigned long end,
636 				struct zap_details *details)
637 {
638 	pmd_t *pmd;
639 	unsigned long next;
640 
641 	pmd = pmd_offset(pud, addr);
642 	do {
643 		next = pmd_addr_end(addr, end);
644 		if (pmd_none_or_clear_bad(pmd))
645 			continue;
646 		zap_pte_range(tlb, vma, pmd, addr, next, details);
647 	} while (pmd++, addr = next, addr != end);
648 }
649 
650 static inline void zap_pud_range(struct mmu_gather *tlb,
651 				struct vm_area_struct *vma, pgd_t *pgd,
652 				unsigned long addr, unsigned long end,
653 				struct zap_details *details)
654 {
655 	pud_t *pud;
656 	unsigned long next;
657 
658 	pud = pud_offset(pgd, addr);
659 	do {
660 		next = pud_addr_end(addr, end);
661 		if (pud_none_or_clear_bad(pud))
662 			continue;
663 		zap_pmd_range(tlb, vma, pud, addr, next, details);
664 	} while (pud++, addr = next, addr != end);
665 }
666 
667 static void unmap_page_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
668 				unsigned long addr, unsigned long end,
669 				struct zap_details *details)
670 {
671 	pgd_t *pgd;
672 	unsigned long next;
673 
674 	if (details && !details->check_mapping && !details->nonlinear_vma)
675 		details = NULL;
676 
677 	BUG_ON(addr >= end);
678 	tlb_start_vma(tlb, vma);
679 	pgd = pgd_offset(vma->vm_mm, addr);
680 	do {
681 		next = pgd_addr_end(addr, end);
682 		if (pgd_none_or_clear_bad(pgd))
683 			continue;
684 		zap_pud_range(tlb, vma, pgd, addr, next, details);
685 	} while (pgd++, addr = next, addr != end);
686 	tlb_end_vma(tlb, vma);
687 }
688 
689 #ifdef CONFIG_PREEMPT
690 # define ZAP_BLOCK_SIZE	(8 * PAGE_SIZE)
691 #else
692 /* No preempt: go for improved straight-line efficiency */
693 # define ZAP_BLOCK_SIZE	(1024 * PAGE_SIZE)
694 #endif
695 
696 /**
697  * unmap_vmas - unmap a range of memory covered by a list of vma's
698  * @tlbp: address of the caller's struct mmu_gather
699  * @vma: the starting vma
700  * @start_addr: virtual address at which to start unmapping
701  * @end_addr: virtual address at which to end unmapping
702  * @nr_accounted: Place number of unmapped pages in vm-accountable vma's here
703  * @details: details of nonlinear truncation or shared cache invalidation
704  *
705  * Returns the end address of the unmapping (restart addr if interrupted).
706  *
707  * Unmap all pages in the vma list.
708  *
709  * We aim to not hold locks for too long (for scheduling latency reasons).
710  * So zap pages in ZAP_BLOCK_SIZE bytecounts.  This means we need to
711  * return the ending mmu_gather to the caller.
712  *
713  * Only addresses between `start' and `end' will be unmapped.
714  *
715  * The VMA list must be sorted in ascending virtual address order.
716  *
717  * unmap_vmas() assumes that the caller will flush the whole unmapped address
718  * range after unmap_vmas() returns.  So the only responsibility here is to
719  * ensure that any thus-far unmapped pages are flushed before unmap_vmas()
720  * drops the lock and schedules.
721  */
722 unsigned long unmap_vmas(struct mmu_gather **tlbp,
723 		struct vm_area_struct *vma, unsigned long start_addr,
724 		unsigned long end_addr, unsigned long *nr_accounted,
725 		struct zap_details *details)
726 {
727 	unsigned long zap_bytes = ZAP_BLOCK_SIZE;
728 	unsigned long tlb_start = 0;	/* For tlb_finish_mmu */
729 	int tlb_start_valid = 0;
730 	unsigned long start = start_addr;
731 	spinlock_t *i_mmap_lock = details? details->i_mmap_lock: NULL;
732 	int fullmm = (*tlbp)->fullmm;
733 
734 	for ( ; vma && vma->vm_start < end_addr; vma = vma->vm_next) {
735 		unsigned long end;
736 
737 		start = max(vma->vm_start, start_addr);
738 		if (start >= vma->vm_end)
739 			continue;
740 		end = min(vma->vm_end, end_addr);
741 		if (end <= vma->vm_start)
742 			continue;
743 
744 		if (vma->vm_flags & VM_ACCOUNT)
745 			*nr_accounted += (end - start) >> PAGE_SHIFT;
746 
747 		while (start != end) {
748 			unsigned long block;
749 
750 			if (!tlb_start_valid) {
751 				tlb_start = start;
752 				tlb_start_valid = 1;
753 			}
754 
755 			if (is_vm_hugetlb_page(vma)) {
756 				block = end - start;
757 				unmap_hugepage_range(vma, start, end);
758 			} else {
759 				block = min(zap_bytes, end - start);
760 				unmap_page_range(*tlbp, vma, start,
761 						start + block, details);
762 			}
763 
764 			start += block;
765 			zap_bytes -= block;
766 			if ((long)zap_bytes > 0)
767 				continue;
768 
769 			tlb_finish_mmu(*tlbp, tlb_start, start);
770 
771 			if (need_resched() ||
772 				(i_mmap_lock && need_lockbreak(i_mmap_lock))) {
773 				if (i_mmap_lock) {
774 					*tlbp = NULL;
775 					goto out;
776 				}
777 				cond_resched();
778 			}
779 
780 			*tlbp = tlb_gather_mmu(vma->vm_mm, fullmm);
781 			tlb_start_valid = 0;
782 			zap_bytes = ZAP_BLOCK_SIZE;
783 		}
784 	}
785 out:
786 	return start;	/* which is now the end (or restart) address */
787 }
788 
789 /**
790  * zap_page_range - remove user pages in a given range
791  * @vma: vm_area_struct holding the applicable pages
792  * @address: starting address of pages to zap
793  * @size: number of bytes to zap
794  * @details: details of nonlinear truncation or shared cache invalidation
795  */
796 unsigned long zap_page_range(struct vm_area_struct *vma, unsigned long address,
797 		unsigned long size, struct zap_details *details)
798 {
799 	struct mm_struct *mm = vma->vm_mm;
800 	struct mmu_gather *tlb;
801 	unsigned long end = address + size;
802 	unsigned long nr_accounted = 0;
803 
804 	lru_add_drain();
805 	tlb = tlb_gather_mmu(mm, 0);
806 	update_hiwater_rss(mm);
807 	end = unmap_vmas(&tlb, vma, address, end, &nr_accounted, details);
808 	if (tlb)
809 		tlb_finish_mmu(tlb, address, end);
810 	return end;
811 }
812 
813 /*
814  * Do a quick page-table lookup for a single page.
815  */
816 struct page *follow_page(struct mm_struct *mm, unsigned long address,
817 			unsigned int flags)
818 {
819 	pgd_t *pgd;
820 	pud_t *pud;
821 	pmd_t *pmd;
822 	pte_t *ptep, pte;
823 	spinlock_t *ptl;
824 	unsigned long pfn;
825 	struct page *page;
826 
827 	page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
828 	if (!IS_ERR(page)) {
829 		BUG_ON(flags & FOLL_GET);
830 		goto out;
831 	}
832 
833 	page = NULL;
834 	pgd = pgd_offset(mm, address);
835 	if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
836 		goto no_page_table;
837 
838 	pud = pud_offset(pgd, address);
839 	if (pud_none(*pud) || unlikely(pud_bad(*pud)))
840 		goto no_page_table;
841 
842 	pmd = pmd_offset(pud, address);
843 	if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
844 		goto no_page_table;
845 
846 	if (pmd_huge(*pmd)) {
847 		BUG_ON(flags & FOLL_GET);
848 		page = follow_huge_pmd(mm, address, pmd, flags & FOLL_WRITE);
849 		goto out;
850 	}
851 
852 	ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
853 	if (!ptep)
854 		goto out;
855 
856 	pte = *ptep;
857 	if (!pte_present(pte))
858 		goto unlock;
859 	if ((flags & FOLL_WRITE) && !pte_write(pte))
860 		goto unlock;
861 	pfn = pte_pfn(pte);
862 	if (!pfn_valid(pfn))
863 		goto unlock;
864 
865 	page = pfn_to_page(pfn);
866 	if (flags & FOLL_GET)
867 		get_page(page);
868 	if (flags & FOLL_TOUCH) {
869 		if ((flags & FOLL_WRITE) &&
870 		    !pte_dirty(pte) && !PageDirty(page))
871 			set_page_dirty(page);
872 		mark_page_accessed(page);
873 	}
874 unlock:
875 	pte_unmap_unlock(ptep, ptl);
876 out:
877 	return page;
878 
879 no_page_table:
880 	/*
881 	 * When core dumping an enormous anonymous area that nobody
882 	 * has touched so far, we don't want to allocate page tables.
883 	 */
884 	if (flags & FOLL_ANON) {
885 		page = ZERO_PAGE(address);
886 		if (flags & FOLL_GET)
887 			get_page(page);
888 		BUG_ON(flags & FOLL_WRITE);
889 	}
890 	return page;
891 }
892 
893 int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
894 		unsigned long start, int len, int write, int force,
895 		struct page **pages, struct vm_area_struct **vmas)
896 {
897 	int i;
898 	unsigned int vm_flags;
899 
900 	/*
901 	 * Require read or write permissions.
902 	 * If 'force' is set, we only require the "MAY" flags.
903 	 */
904 	vm_flags  = write ? (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
905 	vm_flags &= force ? (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
906 	i = 0;
907 
908 	do {
909 		struct vm_area_struct *vma;
910 		unsigned int foll_flags;
911 
912 		vma = find_extend_vma(mm, start);
913 		if (!vma && in_gate_area(tsk, start)) {
914 			unsigned long pg = start & PAGE_MASK;
915 			struct vm_area_struct *gate_vma = get_gate_vma(tsk);
916 			pgd_t *pgd;
917 			pud_t *pud;
918 			pmd_t *pmd;
919 			pte_t *pte;
920 			if (write) /* user gate pages are read-only */
921 				return i ? : -EFAULT;
922 			if (pg > TASK_SIZE)
923 				pgd = pgd_offset_k(pg);
924 			else
925 				pgd = pgd_offset_gate(mm, pg);
926 			BUG_ON(pgd_none(*pgd));
927 			pud = pud_offset(pgd, pg);
928 			BUG_ON(pud_none(*pud));
929 			pmd = pmd_offset(pud, pg);
930 			if (pmd_none(*pmd))
931 				return i ? : -EFAULT;
932 			pte = pte_offset_map(pmd, pg);
933 			if (pte_none(*pte)) {
934 				pte_unmap(pte);
935 				return i ? : -EFAULT;
936 			}
937 			if (pages) {
938 				pages[i] = pte_page(*pte);
939 				get_page(pages[i]);
940 			}
941 			pte_unmap(pte);
942 			if (vmas)
943 				vmas[i] = gate_vma;
944 			i++;
945 			start += PAGE_SIZE;
946 			len--;
947 			continue;
948 		}
949 
950 		if (!vma || (vma->vm_flags & (VM_IO | VM_RESERVED))
951 				|| !(vm_flags & vma->vm_flags))
952 			return i ? : -EFAULT;
953 
954 		if (is_vm_hugetlb_page(vma)) {
955 			i = follow_hugetlb_page(mm, vma, pages, vmas,
956 						&start, &len, i);
957 			continue;
958 		}
959 
960 		foll_flags = FOLL_TOUCH;
961 		if (pages)
962 			foll_flags |= FOLL_GET;
963 		if (!write && !(vma->vm_flags & VM_LOCKED) &&
964 		    (!vma->vm_ops || !vma->vm_ops->nopage))
965 			foll_flags |= FOLL_ANON;
966 
967 		do {
968 			struct page *page;
969 
970 			if (write)
971 				foll_flags |= FOLL_WRITE;
972 
973 			cond_resched();
974 			while (!(page = follow_page(mm, start, foll_flags))) {
975 				int ret;
976 				ret = __handle_mm_fault(mm, vma, start,
977 						foll_flags & FOLL_WRITE);
978 				/*
979 				 * The VM_FAULT_WRITE bit tells us that do_wp_page has
980 				 * broken COW when necessary, even if maybe_mkwrite
981 				 * decided not to set pte_write. We can thus safely do
982 				 * subsequent page lookups as if they were reads.
983 				 */
984 				if (ret & VM_FAULT_WRITE)
985 					foll_flags &= ~FOLL_WRITE;
986 
987 				switch (ret & ~VM_FAULT_WRITE) {
988 				case VM_FAULT_MINOR:
989 					tsk->min_flt++;
990 					break;
991 				case VM_FAULT_MAJOR:
992 					tsk->maj_flt++;
993 					break;
994 				case VM_FAULT_SIGBUS:
995 					return i ? i : -EFAULT;
996 				case VM_FAULT_OOM:
997 					return i ? i : -ENOMEM;
998 				default:
999 					BUG();
1000 				}
1001 			}
1002 			if (pages) {
1003 				pages[i] = page;
1004 				flush_dcache_page(page);
1005 			}
1006 			if (vmas)
1007 				vmas[i] = vma;
1008 			i++;
1009 			start += PAGE_SIZE;
1010 			len--;
1011 		} while (len && start < vma->vm_end);
1012 	} while (len);
1013 	return i;
1014 }
1015 EXPORT_SYMBOL(get_user_pages);
1016 
1017 static int zeromap_pte_range(struct mm_struct *mm, pmd_t *pmd,
1018 			unsigned long addr, unsigned long end, pgprot_t prot)
1019 {
1020 	pte_t *pte;
1021 	spinlock_t *ptl;
1022 
1023 	pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
1024 	if (!pte)
1025 		return -ENOMEM;
1026 	do {
1027 		struct page *page = ZERO_PAGE(addr);
1028 		pte_t zero_pte = pte_wrprotect(mk_pte(page, prot));
1029 		page_cache_get(page);
1030 		page_add_file_rmap(page);
1031 		inc_mm_counter(mm, file_rss);
1032 		BUG_ON(!pte_none(*pte));
1033 		set_pte_at(mm, addr, pte, zero_pte);
1034 	} while (pte++, addr += PAGE_SIZE, addr != end);
1035 	pte_unmap_unlock(pte - 1, ptl);
1036 	return 0;
1037 }
1038 
1039 static inline int zeromap_pmd_range(struct mm_struct *mm, pud_t *pud,
1040 			unsigned long addr, unsigned long end, pgprot_t prot)
1041 {
1042 	pmd_t *pmd;
1043 	unsigned long next;
1044 
1045 	pmd = pmd_alloc(mm, pud, addr);
1046 	if (!pmd)
1047 		return -ENOMEM;
1048 	do {
1049 		next = pmd_addr_end(addr, end);
1050 		if (zeromap_pte_range(mm, pmd, addr, next, prot))
1051 			return -ENOMEM;
1052 	} while (pmd++, addr = next, addr != end);
1053 	return 0;
1054 }
1055 
1056 static inline int zeromap_pud_range(struct mm_struct *mm, pgd_t *pgd,
1057 			unsigned long addr, unsigned long end, pgprot_t prot)
1058 {
1059 	pud_t *pud;
1060 	unsigned long next;
1061 
1062 	pud = pud_alloc(mm, pgd, addr);
1063 	if (!pud)
1064 		return -ENOMEM;
1065 	do {
1066 		next = pud_addr_end(addr, end);
1067 		if (zeromap_pmd_range(mm, pud, addr, next, prot))
1068 			return -ENOMEM;
1069 	} while (pud++, addr = next, addr != end);
1070 	return 0;
1071 }
1072 
1073 int zeromap_page_range(struct vm_area_struct *vma,
1074 			unsigned long addr, unsigned long size, pgprot_t prot)
1075 {
1076 	pgd_t *pgd;
1077 	unsigned long next;
1078 	unsigned long end = addr + size;
1079 	struct mm_struct *mm = vma->vm_mm;
1080 	int err;
1081 
1082 	BUG_ON(addr >= end);
1083 	pgd = pgd_offset(mm, addr);
1084 	flush_cache_range(vma, addr, end);
1085 	do {
1086 		next = pgd_addr_end(addr, end);
1087 		err = zeromap_pud_range(mm, pgd, addr, next, prot);
1088 		if (err)
1089 			break;
1090 	} while (pgd++, addr = next, addr != end);
1091 	return err;
1092 }
1093 
1094 /*
1095  * maps a range of physical memory into the requested pages. the old
1096  * mappings are removed. any references to nonexistent pages results
1097  * in null mappings (currently treated as "copy-on-access")
1098  */
1099 static int remap_pte_range(struct mm_struct *mm, pmd_t *pmd,
1100 			unsigned long addr, unsigned long end,
1101 			unsigned long pfn, pgprot_t prot)
1102 {
1103 	pte_t *pte;
1104 	spinlock_t *ptl;
1105 
1106 	pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
1107 	if (!pte)
1108 		return -ENOMEM;
1109 	do {
1110 		BUG_ON(!pte_none(*pte));
1111 		set_pte_at(mm, addr, pte, pfn_pte(pfn, prot));
1112 		pfn++;
1113 	} while (pte++, addr += PAGE_SIZE, addr != end);
1114 	pte_unmap_unlock(pte - 1, ptl);
1115 	return 0;
1116 }
1117 
1118 static inline int remap_pmd_range(struct mm_struct *mm, pud_t *pud,
1119 			unsigned long addr, unsigned long end,
1120 			unsigned long pfn, pgprot_t prot)
1121 {
1122 	pmd_t *pmd;
1123 	unsigned long next;
1124 
1125 	pfn -= addr >> PAGE_SHIFT;
1126 	pmd = pmd_alloc(mm, pud, addr);
1127 	if (!pmd)
1128 		return -ENOMEM;
1129 	do {
1130 		next = pmd_addr_end(addr, end);
1131 		if (remap_pte_range(mm, pmd, addr, next,
1132 				pfn + (addr >> PAGE_SHIFT), prot))
1133 			return -ENOMEM;
1134 	} while (pmd++, addr = next, addr != end);
1135 	return 0;
1136 }
1137 
1138 static inline int remap_pud_range(struct mm_struct *mm, pgd_t *pgd,
1139 			unsigned long addr, unsigned long end,
1140 			unsigned long pfn, pgprot_t prot)
1141 {
1142 	pud_t *pud;
1143 	unsigned long next;
1144 
1145 	pfn -= addr >> PAGE_SHIFT;
1146 	pud = pud_alloc(mm, pgd, addr);
1147 	if (!pud)
1148 		return -ENOMEM;
1149 	do {
1150 		next = pud_addr_end(addr, end);
1151 		if (remap_pmd_range(mm, pud, addr, next,
1152 				pfn + (addr >> PAGE_SHIFT), prot))
1153 			return -ENOMEM;
1154 	} while (pud++, addr = next, addr != end);
1155 	return 0;
1156 }
1157 
1158 /*  Note: this is only safe if the mm semaphore is held when called. */
1159 int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
1160 		    unsigned long pfn, unsigned long size, pgprot_t prot)
1161 {
1162 	pgd_t *pgd;
1163 	unsigned long next;
1164 	unsigned long end = addr + PAGE_ALIGN(size);
1165 	struct mm_struct *mm = vma->vm_mm;
1166 	int err;
1167 
1168 	/*
1169 	 * Physically remapped pages are special. Tell the
1170 	 * rest of the world about it:
1171 	 *   VM_IO tells people not to look at these pages
1172 	 *	(accesses can have side effects).
1173 	 *   VM_RESERVED tells the core MM not to "manage" these pages
1174          *	(e.g. refcount, mapcount, try to swap them out).
1175 	 */
1176 	vma->vm_flags |= VM_IO | VM_RESERVED;
1177 
1178 	BUG_ON(addr >= end);
1179 	pfn -= addr >> PAGE_SHIFT;
1180 	pgd = pgd_offset(mm, addr);
1181 	flush_cache_range(vma, addr, end);
1182 	do {
1183 		next = pgd_addr_end(addr, end);
1184 		err = remap_pud_range(mm, pgd, addr, next,
1185 				pfn + (addr >> PAGE_SHIFT), prot);
1186 		if (err)
1187 			break;
1188 	} while (pgd++, addr = next, addr != end);
1189 	return err;
1190 }
1191 EXPORT_SYMBOL(remap_pfn_range);
1192 
1193 /*
1194  * handle_pte_fault chooses page fault handler according to an entry
1195  * which was read non-atomically.  Before making any commitment, on
1196  * those architectures or configurations (e.g. i386 with PAE) which
1197  * might give a mix of unmatched parts, do_swap_page and do_file_page
1198  * must check under lock before unmapping the pte and proceeding
1199  * (but do_wp_page is only called after already making such a check;
1200  * and do_anonymous_page and do_no_page can safely check later on).
1201  */
1202 static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd,
1203 				pte_t *page_table, pte_t orig_pte)
1204 {
1205 	int same = 1;
1206 #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
1207 	if (sizeof(pte_t) > sizeof(unsigned long)) {
1208 		spinlock_t *ptl = pte_lockptr(mm, pmd);
1209 		spin_lock(ptl);
1210 		same = pte_same(*page_table, orig_pte);
1211 		spin_unlock(ptl);
1212 	}
1213 #endif
1214 	pte_unmap(page_table);
1215 	return same;
1216 }
1217 
1218 /*
1219  * Do pte_mkwrite, but only if the vma says VM_WRITE.  We do this when
1220  * servicing faults for write access.  In the normal case, do always want
1221  * pte_mkwrite.  But get_user_pages can cause write faults for mappings
1222  * that do not have writing enabled, when used by access_process_vm.
1223  */
1224 static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
1225 {
1226 	if (likely(vma->vm_flags & VM_WRITE))
1227 		pte = pte_mkwrite(pte);
1228 	return pte;
1229 }
1230 
1231 /*
1232  * This routine handles present pages, when users try to write
1233  * to a shared page. It is done by copying the page to a new address
1234  * and decrementing the shared-page counter for the old page.
1235  *
1236  * Note that this routine assumes that the protection checks have been
1237  * done by the caller (the low-level page fault routine in most cases).
1238  * Thus we can safely just mark it writable once we've done any necessary
1239  * COW.
1240  *
1241  * We also mark the page dirty at this point even though the page will
1242  * change only once the write actually happens. This avoids a few races,
1243  * and potentially makes it more efficient.
1244  *
1245  * We enter with non-exclusive mmap_sem (to exclude vma changes,
1246  * but allow concurrent faults), with pte both mapped and locked.
1247  * We return with mmap_sem still held, but pte unmapped and unlocked.
1248  */
1249 static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
1250 		unsigned long address, pte_t *page_table, pmd_t *pmd,
1251 		spinlock_t *ptl, pte_t orig_pte)
1252 {
1253 	struct page *old_page, *new_page;
1254 	unsigned long pfn = pte_pfn(orig_pte);
1255 	pte_t entry;
1256 	int ret = VM_FAULT_MINOR;
1257 
1258 	BUG_ON(vma->vm_flags & VM_RESERVED);
1259 
1260 	if (unlikely(!pfn_valid(pfn))) {
1261 		/*
1262 		 * Page table corrupted: show pte and kill process.
1263 		 */
1264 		print_bad_pte(vma, orig_pte, address);
1265 		ret = VM_FAULT_OOM;
1266 		goto unlock;
1267 	}
1268 	old_page = pfn_to_page(pfn);
1269 
1270 	if (PageAnon(old_page) && !TestSetPageLocked(old_page)) {
1271 		int reuse = can_share_swap_page(old_page);
1272 		unlock_page(old_page);
1273 		if (reuse) {
1274 			flush_cache_page(vma, address, pfn);
1275 			entry = pte_mkyoung(orig_pte);
1276 			entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1277 			ptep_set_access_flags(vma, address, page_table, entry, 1);
1278 			update_mmu_cache(vma, address, entry);
1279 			lazy_mmu_prot_update(entry);
1280 			ret |= VM_FAULT_WRITE;
1281 			goto unlock;
1282 		}
1283 	}
1284 
1285 	/*
1286 	 * Ok, we need to copy. Oh, well..
1287 	 */
1288 	page_cache_get(old_page);
1289 	pte_unmap_unlock(page_table, ptl);
1290 
1291 	if (unlikely(anon_vma_prepare(vma)))
1292 		goto oom;
1293 	if (old_page == ZERO_PAGE(address)) {
1294 		new_page = alloc_zeroed_user_highpage(vma, address);
1295 		if (!new_page)
1296 			goto oom;
1297 	} else {
1298 		new_page = alloc_page_vma(GFP_HIGHUSER, vma, address);
1299 		if (!new_page)
1300 			goto oom;
1301 		copy_user_highpage(new_page, old_page, address);
1302 	}
1303 
1304 	/*
1305 	 * Re-check the pte - we dropped the lock
1306 	 */
1307 	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
1308 	if (likely(pte_same(*page_table, orig_pte))) {
1309 		page_remove_rmap(old_page);
1310 		if (!PageAnon(old_page)) {
1311 			inc_mm_counter(mm, anon_rss);
1312 			dec_mm_counter(mm, file_rss);
1313 		}
1314 		flush_cache_page(vma, address, pfn);
1315 		entry = mk_pte(new_page, vma->vm_page_prot);
1316 		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1317 		ptep_establish(vma, address, page_table, entry);
1318 		update_mmu_cache(vma, address, entry);
1319 		lazy_mmu_prot_update(entry);
1320 		lru_cache_add_active(new_page);
1321 		page_add_anon_rmap(new_page, vma, address);
1322 
1323 		/* Free the old page.. */
1324 		new_page = old_page;
1325 		ret |= VM_FAULT_WRITE;
1326 	}
1327 	page_cache_release(new_page);
1328 	page_cache_release(old_page);
1329 unlock:
1330 	pte_unmap_unlock(page_table, ptl);
1331 	return ret;
1332 oom:
1333 	page_cache_release(old_page);
1334 	return VM_FAULT_OOM;
1335 }
1336 
1337 /*
1338  * Helper functions for unmap_mapping_range().
1339  *
1340  * __ Notes on dropping i_mmap_lock to reduce latency while unmapping __
1341  *
1342  * We have to restart searching the prio_tree whenever we drop the lock,
1343  * since the iterator is only valid while the lock is held, and anyway
1344  * a later vma might be split and reinserted earlier while lock dropped.
1345  *
1346  * The list of nonlinear vmas could be handled more efficiently, using
1347  * a placeholder, but handle it in the same way until a need is shown.
1348  * It is important to search the prio_tree before nonlinear list: a vma
1349  * may become nonlinear and be shifted from prio_tree to nonlinear list
1350  * while the lock is dropped; but never shifted from list to prio_tree.
1351  *
1352  * In order to make forward progress despite restarting the search,
1353  * vm_truncate_count is used to mark a vma as now dealt with, so we can
1354  * quickly skip it next time around.  Since the prio_tree search only
1355  * shows us those vmas affected by unmapping the range in question, we
1356  * can't efficiently keep all vmas in step with mapping->truncate_count:
1357  * so instead reset them all whenever it wraps back to 0 (then go to 1).
1358  * mapping->truncate_count and vma->vm_truncate_count are protected by
1359  * i_mmap_lock.
1360  *
1361  * In order to make forward progress despite repeatedly restarting some
1362  * large vma, note the restart_addr from unmap_vmas when it breaks out:
1363  * and restart from that address when we reach that vma again.  It might
1364  * have been split or merged, shrunk or extended, but never shifted: so
1365  * restart_addr remains valid so long as it remains in the vma's range.
1366  * unmap_mapping_range forces truncate_count to leap over page-aligned
1367  * values so we can save vma's restart_addr in its truncate_count field.
1368  */
1369 #define is_restart_addr(truncate_count) (!((truncate_count) & ~PAGE_MASK))
1370 
1371 static void reset_vma_truncate_counts(struct address_space *mapping)
1372 {
1373 	struct vm_area_struct *vma;
1374 	struct prio_tree_iter iter;
1375 
1376 	vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, 0, ULONG_MAX)
1377 		vma->vm_truncate_count = 0;
1378 	list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list)
1379 		vma->vm_truncate_count = 0;
1380 }
1381 
1382 static int unmap_mapping_range_vma(struct vm_area_struct *vma,
1383 		unsigned long start_addr, unsigned long end_addr,
1384 		struct zap_details *details)
1385 {
1386 	unsigned long restart_addr;
1387 	int need_break;
1388 
1389 again:
1390 	restart_addr = vma->vm_truncate_count;
1391 	if (is_restart_addr(restart_addr) && start_addr < restart_addr) {
1392 		start_addr = restart_addr;
1393 		if (start_addr >= end_addr) {
1394 			/* Top of vma has been split off since last time */
1395 			vma->vm_truncate_count = details->truncate_count;
1396 			return 0;
1397 		}
1398 	}
1399 
1400 	restart_addr = zap_page_range(vma, start_addr,
1401 					end_addr - start_addr, details);
1402 	need_break = need_resched() ||
1403 			need_lockbreak(details->i_mmap_lock);
1404 
1405 	if (restart_addr >= end_addr) {
1406 		/* We have now completed this vma: mark it so */
1407 		vma->vm_truncate_count = details->truncate_count;
1408 		if (!need_break)
1409 			return 0;
1410 	} else {
1411 		/* Note restart_addr in vma's truncate_count field */
1412 		vma->vm_truncate_count = restart_addr;
1413 		if (!need_break)
1414 			goto again;
1415 	}
1416 
1417 	spin_unlock(details->i_mmap_lock);
1418 	cond_resched();
1419 	spin_lock(details->i_mmap_lock);
1420 	return -EINTR;
1421 }
1422 
1423 static inline void unmap_mapping_range_tree(struct prio_tree_root *root,
1424 					    struct zap_details *details)
1425 {
1426 	struct vm_area_struct *vma;
1427 	struct prio_tree_iter iter;
1428 	pgoff_t vba, vea, zba, zea;
1429 
1430 restart:
1431 	vma_prio_tree_foreach(vma, &iter, root,
1432 			details->first_index, details->last_index) {
1433 		/* Skip quickly over those we have already dealt with */
1434 		if (vma->vm_truncate_count == details->truncate_count)
1435 			continue;
1436 
1437 		vba = vma->vm_pgoff;
1438 		vea = vba + ((vma->vm_end - vma->vm_start) >> PAGE_SHIFT) - 1;
1439 		/* Assume for now that PAGE_CACHE_SHIFT == PAGE_SHIFT */
1440 		zba = details->first_index;
1441 		if (zba < vba)
1442 			zba = vba;
1443 		zea = details->last_index;
1444 		if (zea > vea)
1445 			zea = vea;
1446 
1447 		if (unmap_mapping_range_vma(vma,
1448 			((zba - vba) << PAGE_SHIFT) + vma->vm_start,
1449 			((zea - vba + 1) << PAGE_SHIFT) + vma->vm_start,
1450 				details) < 0)
1451 			goto restart;
1452 	}
1453 }
1454 
1455 static inline void unmap_mapping_range_list(struct list_head *head,
1456 					    struct zap_details *details)
1457 {
1458 	struct vm_area_struct *vma;
1459 
1460 	/*
1461 	 * In nonlinear VMAs there is no correspondence between virtual address
1462 	 * offset and file offset.  So we must perform an exhaustive search
1463 	 * across *all* the pages in each nonlinear VMA, not just the pages
1464 	 * whose virtual address lies outside the file truncation point.
1465 	 */
1466 restart:
1467 	list_for_each_entry(vma, head, shared.vm_set.list) {
1468 		/* Skip quickly over those we have already dealt with */
1469 		if (vma->vm_truncate_count == details->truncate_count)
1470 			continue;
1471 		details->nonlinear_vma = vma;
1472 		if (unmap_mapping_range_vma(vma, vma->vm_start,
1473 					vma->vm_end, details) < 0)
1474 			goto restart;
1475 	}
1476 }
1477 
1478 /**
1479  * unmap_mapping_range - unmap the portion of all mmaps
1480  * in the specified address_space corresponding to the specified
1481  * page range in the underlying file.
1482  * @mapping: the address space containing mmaps to be unmapped.
1483  * @holebegin: byte in first page to unmap, relative to the start of
1484  * the underlying file.  This will be rounded down to a PAGE_SIZE
1485  * boundary.  Note that this is different from vmtruncate(), which
1486  * must keep the partial page.  In contrast, we must get rid of
1487  * partial pages.
1488  * @holelen: size of prospective hole in bytes.  This will be rounded
1489  * up to a PAGE_SIZE boundary.  A holelen of zero truncates to the
1490  * end of the file.
1491  * @even_cows: 1 when truncating a file, unmap even private COWed pages;
1492  * but 0 when invalidating pagecache, don't throw away private data.
1493  */
1494 void unmap_mapping_range(struct address_space *mapping,
1495 		loff_t const holebegin, loff_t const holelen, int even_cows)
1496 {
1497 	struct zap_details details;
1498 	pgoff_t hba = holebegin >> PAGE_SHIFT;
1499 	pgoff_t hlen = (holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
1500 
1501 	/* Check for overflow. */
1502 	if (sizeof(holelen) > sizeof(hlen)) {
1503 		long long holeend =
1504 			(holebegin + holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
1505 		if (holeend & ~(long long)ULONG_MAX)
1506 			hlen = ULONG_MAX - hba + 1;
1507 	}
1508 
1509 	details.check_mapping = even_cows? NULL: mapping;
1510 	details.nonlinear_vma = NULL;
1511 	details.first_index = hba;
1512 	details.last_index = hba + hlen - 1;
1513 	if (details.last_index < details.first_index)
1514 		details.last_index = ULONG_MAX;
1515 	details.i_mmap_lock = &mapping->i_mmap_lock;
1516 
1517 	spin_lock(&mapping->i_mmap_lock);
1518 
1519 	/* serialize i_size write against truncate_count write */
1520 	smp_wmb();
1521 	/* Protect against page faults, and endless unmapping loops */
1522 	mapping->truncate_count++;
1523 	/*
1524 	 * For archs where spin_lock has inclusive semantics like ia64
1525 	 * this smp_mb() will prevent to read pagetable contents
1526 	 * before the truncate_count increment is visible to
1527 	 * other cpus.
1528 	 */
1529 	smp_mb();
1530 	if (unlikely(is_restart_addr(mapping->truncate_count))) {
1531 		if (mapping->truncate_count == 0)
1532 			reset_vma_truncate_counts(mapping);
1533 		mapping->truncate_count++;
1534 	}
1535 	details.truncate_count = mapping->truncate_count;
1536 
1537 	if (unlikely(!prio_tree_empty(&mapping->i_mmap)))
1538 		unmap_mapping_range_tree(&mapping->i_mmap, &details);
1539 	if (unlikely(!list_empty(&mapping->i_mmap_nonlinear)))
1540 		unmap_mapping_range_list(&mapping->i_mmap_nonlinear, &details);
1541 	spin_unlock(&mapping->i_mmap_lock);
1542 }
1543 EXPORT_SYMBOL(unmap_mapping_range);
1544 
1545 /*
1546  * Handle all mappings that got truncated by a "truncate()"
1547  * system call.
1548  *
1549  * NOTE! We have to be ready to update the memory sharing
1550  * between the file and the memory map for a potential last
1551  * incomplete page.  Ugly, but necessary.
1552  */
1553 int vmtruncate(struct inode * inode, loff_t offset)
1554 {
1555 	struct address_space *mapping = inode->i_mapping;
1556 	unsigned long limit;
1557 
1558 	if (inode->i_size < offset)
1559 		goto do_expand;
1560 	/*
1561 	 * truncation of in-use swapfiles is disallowed - it would cause
1562 	 * subsequent swapout to scribble on the now-freed blocks.
1563 	 */
1564 	if (IS_SWAPFILE(inode))
1565 		goto out_busy;
1566 	i_size_write(inode, offset);
1567 	unmap_mapping_range(mapping, offset + PAGE_SIZE - 1, 0, 1);
1568 	truncate_inode_pages(mapping, offset);
1569 	goto out_truncate;
1570 
1571 do_expand:
1572 	limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
1573 	if (limit != RLIM_INFINITY && offset > limit)
1574 		goto out_sig;
1575 	if (offset > inode->i_sb->s_maxbytes)
1576 		goto out_big;
1577 	i_size_write(inode, offset);
1578 
1579 out_truncate:
1580 	if (inode->i_op && inode->i_op->truncate)
1581 		inode->i_op->truncate(inode);
1582 	return 0;
1583 out_sig:
1584 	send_sig(SIGXFSZ, current, 0);
1585 out_big:
1586 	return -EFBIG;
1587 out_busy:
1588 	return -ETXTBSY;
1589 }
1590 
1591 EXPORT_SYMBOL(vmtruncate);
1592 
1593 /*
1594  * Primitive swap readahead code. We simply read an aligned block of
1595  * (1 << page_cluster) entries in the swap area. This method is chosen
1596  * because it doesn't cost us any seek time.  We also make sure to queue
1597  * the 'original' request together with the readahead ones...
1598  *
1599  * This has been extended to use the NUMA policies from the mm triggering
1600  * the readahead.
1601  *
1602  * Caller must hold down_read on the vma->vm_mm if vma is not NULL.
1603  */
1604 void swapin_readahead(swp_entry_t entry, unsigned long addr,struct vm_area_struct *vma)
1605 {
1606 #ifdef CONFIG_NUMA
1607 	struct vm_area_struct *next_vma = vma ? vma->vm_next : NULL;
1608 #endif
1609 	int i, num;
1610 	struct page *new_page;
1611 	unsigned long offset;
1612 
1613 	/*
1614 	 * Get the number of handles we should do readahead io to.
1615 	 */
1616 	num = valid_swaphandles(entry, &offset);
1617 	for (i = 0; i < num; offset++, i++) {
1618 		/* Ok, do the async read-ahead now */
1619 		new_page = read_swap_cache_async(swp_entry(swp_type(entry),
1620 							   offset), vma, addr);
1621 		if (!new_page)
1622 			break;
1623 		page_cache_release(new_page);
1624 #ifdef CONFIG_NUMA
1625 		/*
1626 		 * Find the next applicable VMA for the NUMA policy.
1627 		 */
1628 		addr += PAGE_SIZE;
1629 		if (addr == 0)
1630 			vma = NULL;
1631 		if (vma) {
1632 			if (addr >= vma->vm_end) {
1633 				vma = next_vma;
1634 				next_vma = vma ? vma->vm_next : NULL;
1635 			}
1636 			if (vma && addr < vma->vm_start)
1637 				vma = NULL;
1638 		} else {
1639 			if (next_vma && addr >= next_vma->vm_start) {
1640 				vma = next_vma;
1641 				next_vma = vma->vm_next;
1642 			}
1643 		}
1644 #endif
1645 	}
1646 	lru_add_drain();	/* Push any new pages onto the LRU now */
1647 }
1648 
1649 /*
1650  * We enter with non-exclusive mmap_sem (to exclude vma changes,
1651  * but allow concurrent faults), and pte mapped but not yet locked.
1652  * We return with mmap_sem still held, but pte unmapped and unlocked.
1653  */
1654 static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
1655 		unsigned long address, pte_t *page_table, pmd_t *pmd,
1656 		int write_access, pte_t orig_pte)
1657 {
1658 	spinlock_t *ptl;
1659 	struct page *page;
1660 	swp_entry_t entry;
1661 	pte_t pte;
1662 	int ret = VM_FAULT_MINOR;
1663 
1664 	if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
1665 		goto out;
1666 
1667 	entry = pte_to_swp_entry(orig_pte);
1668 	page = lookup_swap_cache(entry);
1669 	if (!page) {
1670  		swapin_readahead(entry, address, vma);
1671  		page = read_swap_cache_async(entry, vma, address);
1672 		if (!page) {
1673 			/*
1674 			 * Back out if somebody else faulted in this pte
1675 			 * while we released the pte lock.
1676 			 */
1677 			page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
1678 			if (likely(pte_same(*page_table, orig_pte)))
1679 				ret = VM_FAULT_OOM;
1680 			goto unlock;
1681 		}
1682 
1683 		/* Had to read the page from swap area: Major fault */
1684 		ret = VM_FAULT_MAJOR;
1685 		inc_page_state(pgmajfault);
1686 		grab_swap_token();
1687 	}
1688 
1689 	mark_page_accessed(page);
1690 	lock_page(page);
1691 
1692 	/*
1693 	 * Back out if somebody else already faulted in this pte.
1694 	 */
1695 	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
1696 	if (unlikely(!pte_same(*page_table, orig_pte)))
1697 		goto out_nomap;
1698 
1699 	if (unlikely(!PageUptodate(page))) {
1700 		ret = VM_FAULT_SIGBUS;
1701 		goto out_nomap;
1702 	}
1703 
1704 	/* The page isn't present yet, go ahead with the fault. */
1705 
1706 	inc_mm_counter(mm, anon_rss);
1707 	pte = mk_pte(page, vma->vm_page_prot);
1708 	if (write_access && can_share_swap_page(page)) {
1709 		pte = maybe_mkwrite(pte_mkdirty(pte), vma);
1710 		write_access = 0;
1711 	}
1712 
1713 	flush_icache_page(vma, page);
1714 	set_pte_at(mm, address, page_table, pte);
1715 	page_add_anon_rmap(page, vma, address);
1716 
1717 	swap_free(entry);
1718 	if (vm_swap_full())
1719 		remove_exclusive_swap_page(page);
1720 	unlock_page(page);
1721 
1722 	if (write_access) {
1723 		if (do_wp_page(mm, vma, address,
1724 				page_table, pmd, ptl, pte) == VM_FAULT_OOM)
1725 			ret = VM_FAULT_OOM;
1726 		goto out;
1727 	}
1728 
1729 	/* No need to invalidate - it was non-present before */
1730 	update_mmu_cache(vma, address, pte);
1731 	lazy_mmu_prot_update(pte);
1732 unlock:
1733 	pte_unmap_unlock(page_table, ptl);
1734 out:
1735 	return ret;
1736 out_nomap:
1737 	pte_unmap_unlock(page_table, ptl);
1738 	unlock_page(page);
1739 	page_cache_release(page);
1740 	return ret;
1741 }
1742 
1743 /*
1744  * We enter with non-exclusive mmap_sem (to exclude vma changes,
1745  * but allow concurrent faults), and pte mapped but not yet locked.
1746  * We return with mmap_sem still held, but pte unmapped and unlocked.
1747  */
1748 static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
1749 		unsigned long address, pte_t *page_table, pmd_t *pmd,
1750 		int write_access)
1751 {
1752 	struct page *page;
1753 	spinlock_t *ptl;
1754 	pte_t entry;
1755 
1756 	if (write_access) {
1757 		/* Allocate our own private page. */
1758 		pte_unmap(page_table);
1759 
1760 		if (unlikely(anon_vma_prepare(vma)))
1761 			goto oom;
1762 		page = alloc_zeroed_user_highpage(vma, address);
1763 		if (!page)
1764 			goto oom;
1765 
1766 		entry = mk_pte(page, vma->vm_page_prot);
1767 		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1768 
1769 		page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
1770 		if (!pte_none(*page_table))
1771 			goto release;
1772 		inc_mm_counter(mm, anon_rss);
1773 		lru_cache_add_active(page);
1774 		SetPageReferenced(page);
1775 		page_add_anon_rmap(page, vma, address);
1776 	} else {
1777 		/* Map the ZERO_PAGE - vm_page_prot is readonly */
1778 		page = ZERO_PAGE(address);
1779 		page_cache_get(page);
1780 		entry = mk_pte(page, vma->vm_page_prot);
1781 
1782 		ptl = pte_lockptr(mm, pmd);
1783 		spin_lock(ptl);
1784 		if (!pte_none(*page_table))
1785 			goto release;
1786 		inc_mm_counter(mm, file_rss);
1787 		page_add_file_rmap(page);
1788 	}
1789 
1790 	set_pte_at(mm, address, page_table, entry);
1791 
1792 	/* No need to invalidate - it was non-present before */
1793 	update_mmu_cache(vma, address, entry);
1794 	lazy_mmu_prot_update(entry);
1795 unlock:
1796 	pte_unmap_unlock(page_table, ptl);
1797 	return VM_FAULT_MINOR;
1798 release:
1799 	page_cache_release(page);
1800 	goto unlock;
1801 oom:
1802 	return VM_FAULT_OOM;
1803 }
1804 
1805 /*
1806  * do_no_page() tries to create a new page mapping. It aggressively
1807  * tries to share with existing pages, but makes a separate copy if
1808  * the "write_access" parameter is true in order to avoid the next
1809  * page fault.
1810  *
1811  * As this is called only for pages that do not currently exist, we
1812  * do not need to flush old virtual caches or the TLB.
1813  *
1814  * We enter with non-exclusive mmap_sem (to exclude vma changes,
1815  * but allow concurrent faults), and pte mapped but not yet locked.
1816  * We return with mmap_sem still held, but pte unmapped and unlocked.
1817  */
1818 static int do_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
1819 		unsigned long address, pte_t *page_table, pmd_t *pmd,
1820 		int write_access)
1821 {
1822 	spinlock_t *ptl;
1823 	struct page *new_page;
1824 	struct address_space *mapping = NULL;
1825 	pte_t entry;
1826 	unsigned int sequence = 0;
1827 	int ret = VM_FAULT_MINOR;
1828 	int anon = 0;
1829 
1830 	pte_unmap(page_table);
1831 
1832 	if (vma->vm_file) {
1833 		mapping = vma->vm_file->f_mapping;
1834 		sequence = mapping->truncate_count;
1835 		smp_rmb(); /* serializes i_size against truncate_count */
1836 	}
1837 retry:
1838 	new_page = vma->vm_ops->nopage(vma, address & PAGE_MASK, &ret);
1839 	/*
1840 	 * No smp_rmb is needed here as long as there's a full
1841 	 * spin_lock/unlock sequence inside the ->nopage callback
1842 	 * (for the pagecache lookup) that acts as an implicit
1843 	 * smp_mb() and prevents the i_size read to happen
1844 	 * after the next truncate_count read.
1845 	 */
1846 
1847 	/* no page was available -- either SIGBUS or OOM */
1848 	if (new_page == NOPAGE_SIGBUS)
1849 		return VM_FAULT_SIGBUS;
1850 	if (new_page == NOPAGE_OOM)
1851 		return VM_FAULT_OOM;
1852 
1853 	/*
1854 	 * Should we do an early C-O-W break?
1855 	 */
1856 	if (write_access && !(vma->vm_flags & VM_SHARED)) {
1857 		struct page *page;
1858 
1859 		if (unlikely(anon_vma_prepare(vma)))
1860 			goto oom;
1861 		page = alloc_page_vma(GFP_HIGHUSER, vma, address);
1862 		if (!page)
1863 			goto oom;
1864 		copy_user_highpage(page, new_page, address);
1865 		page_cache_release(new_page);
1866 		new_page = page;
1867 		anon = 1;
1868 	}
1869 
1870 	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
1871 	/*
1872 	 * For a file-backed vma, someone could have truncated or otherwise
1873 	 * invalidated this page.  If unmap_mapping_range got called,
1874 	 * retry getting the page.
1875 	 */
1876 	if (mapping && unlikely(sequence != mapping->truncate_count)) {
1877 		pte_unmap_unlock(page_table, ptl);
1878 		page_cache_release(new_page);
1879 		cond_resched();
1880 		sequence = mapping->truncate_count;
1881 		smp_rmb();
1882 		goto retry;
1883 	}
1884 
1885 	/*
1886 	 * This silly early PAGE_DIRTY setting removes a race
1887 	 * due to the bad i386 page protection. But it's valid
1888 	 * for other architectures too.
1889 	 *
1890 	 * Note that if write_access is true, we either now have
1891 	 * an exclusive copy of the page, or this is a shared mapping,
1892 	 * so we can make it writable and dirty to avoid having to
1893 	 * handle that later.
1894 	 */
1895 	/* Only go through if we didn't race with anybody else... */
1896 	if (pte_none(*page_table)) {
1897 		flush_icache_page(vma, new_page);
1898 		entry = mk_pte(new_page, vma->vm_page_prot);
1899 		if (write_access)
1900 			entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1901 		set_pte_at(mm, address, page_table, entry);
1902 		if (anon) {
1903 			inc_mm_counter(mm, anon_rss);
1904 			lru_cache_add_active(new_page);
1905 			page_add_anon_rmap(new_page, vma, address);
1906 		} else if (!(vma->vm_flags & VM_RESERVED)) {
1907 			inc_mm_counter(mm, file_rss);
1908 			page_add_file_rmap(new_page);
1909 		}
1910 	} else {
1911 		/* One of our sibling threads was faster, back out. */
1912 		page_cache_release(new_page);
1913 		goto unlock;
1914 	}
1915 
1916 	/* no need to invalidate: a not-present page shouldn't be cached */
1917 	update_mmu_cache(vma, address, entry);
1918 	lazy_mmu_prot_update(entry);
1919 unlock:
1920 	pte_unmap_unlock(page_table, ptl);
1921 	return ret;
1922 oom:
1923 	page_cache_release(new_page);
1924 	return VM_FAULT_OOM;
1925 }
1926 
1927 /*
1928  * Fault of a previously existing named mapping. Repopulate the pte
1929  * from the encoded file_pte if possible. This enables swappable
1930  * nonlinear vmas.
1931  *
1932  * We enter with non-exclusive mmap_sem (to exclude vma changes,
1933  * but allow concurrent faults), and pte mapped but not yet locked.
1934  * We return with mmap_sem still held, but pte unmapped and unlocked.
1935  */
1936 static int do_file_page(struct mm_struct *mm, struct vm_area_struct *vma,
1937 		unsigned long address, pte_t *page_table, pmd_t *pmd,
1938 		int write_access, pte_t orig_pte)
1939 {
1940 	pgoff_t pgoff;
1941 	int err;
1942 
1943 	if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
1944 		return VM_FAULT_MINOR;
1945 
1946 	if (unlikely(!(vma->vm_flags & VM_NONLINEAR))) {
1947 		/*
1948 		 * Page table corrupted: show pte and kill process.
1949 		 */
1950 		print_bad_pte(vma, orig_pte, address);
1951 		return VM_FAULT_OOM;
1952 	}
1953 	/* We can then assume vm->vm_ops && vma->vm_ops->populate */
1954 
1955 	pgoff = pte_to_pgoff(orig_pte);
1956 	err = vma->vm_ops->populate(vma, address & PAGE_MASK, PAGE_SIZE,
1957 					vma->vm_page_prot, pgoff, 0);
1958 	if (err == -ENOMEM)
1959 		return VM_FAULT_OOM;
1960 	if (err)
1961 		return VM_FAULT_SIGBUS;
1962 	return VM_FAULT_MAJOR;
1963 }
1964 
1965 /*
1966  * These routines also need to handle stuff like marking pages dirty
1967  * and/or accessed for architectures that don't do it in hardware (most
1968  * RISC architectures).  The early dirtying is also good on the i386.
1969  *
1970  * There is also a hook called "update_mmu_cache()" that architectures
1971  * with external mmu caches can use to update those (ie the Sparc or
1972  * PowerPC hashed page tables that act as extended TLBs).
1973  *
1974  * We enter with non-exclusive mmap_sem (to exclude vma changes,
1975  * but allow concurrent faults), and pte mapped but not yet locked.
1976  * We return with mmap_sem still held, but pte unmapped and unlocked.
1977  */
1978 static inline int handle_pte_fault(struct mm_struct *mm,
1979 		struct vm_area_struct *vma, unsigned long address,
1980 		pte_t *pte, pmd_t *pmd, int write_access)
1981 {
1982 	pte_t entry;
1983 	pte_t old_entry;
1984 	spinlock_t *ptl;
1985 
1986 	old_entry = entry = *pte;
1987 	if (!pte_present(entry)) {
1988 		if (pte_none(entry)) {
1989 			if (!vma->vm_ops || !vma->vm_ops->nopage)
1990 				return do_anonymous_page(mm, vma, address,
1991 					pte, pmd, write_access);
1992 			return do_no_page(mm, vma, address,
1993 					pte, pmd, write_access);
1994 		}
1995 		if (pte_file(entry))
1996 			return do_file_page(mm, vma, address,
1997 					pte, pmd, write_access, entry);
1998 		return do_swap_page(mm, vma, address,
1999 					pte, pmd, write_access, entry);
2000 	}
2001 
2002 	ptl = pte_lockptr(mm, pmd);
2003 	spin_lock(ptl);
2004 	if (unlikely(!pte_same(*pte, entry)))
2005 		goto unlock;
2006 	if (write_access) {
2007 		if (!pte_write(entry))
2008 			return do_wp_page(mm, vma, address,
2009 					pte, pmd, ptl, entry);
2010 		entry = pte_mkdirty(entry);
2011 	}
2012 	entry = pte_mkyoung(entry);
2013 	if (!pte_same(old_entry, entry)) {
2014 		ptep_set_access_flags(vma, address, pte, entry, write_access);
2015 		update_mmu_cache(vma, address, entry);
2016 		lazy_mmu_prot_update(entry);
2017 	} else {
2018 		/*
2019 		 * This is needed only for protection faults but the arch code
2020 		 * is not yet telling us if this is a protection fault or not.
2021 		 * This still avoids useless tlb flushes for .text page faults
2022 		 * with threads.
2023 		 */
2024 		if (write_access)
2025 			flush_tlb_page(vma, address);
2026 	}
2027 unlock:
2028 	pte_unmap_unlock(pte, ptl);
2029 	return VM_FAULT_MINOR;
2030 }
2031 
2032 /*
2033  * By the time we get here, we already hold the mm semaphore
2034  */
2035 int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
2036 		unsigned long address, int write_access)
2037 {
2038 	pgd_t *pgd;
2039 	pud_t *pud;
2040 	pmd_t *pmd;
2041 	pte_t *pte;
2042 
2043 	__set_current_state(TASK_RUNNING);
2044 
2045 	inc_page_state(pgfault);
2046 
2047 	if (unlikely(is_vm_hugetlb_page(vma)))
2048 		return hugetlb_fault(mm, vma, address, write_access);
2049 
2050 	pgd = pgd_offset(mm, address);
2051 	pud = pud_alloc(mm, pgd, address);
2052 	if (!pud)
2053 		return VM_FAULT_OOM;
2054 	pmd = pmd_alloc(mm, pud, address);
2055 	if (!pmd)
2056 		return VM_FAULT_OOM;
2057 	pte = pte_alloc_map(mm, pmd, address);
2058 	if (!pte)
2059 		return VM_FAULT_OOM;
2060 
2061 	return handle_pte_fault(mm, vma, address, pte, pmd, write_access);
2062 }
2063 
2064 #ifndef __PAGETABLE_PUD_FOLDED
2065 /*
2066  * Allocate page upper directory.
2067  * We've already handled the fast-path in-line.
2068  */
2069 int __pud_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address)
2070 {
2071 	pud_t *new = pud_alloc_one(mm, address);
2072 	if (!new)
2073 		return -ENOMEM;
2074 
2075 	spin_lock(&mm->page_table_lock);
2076 	if (pgd_present(*pgd))		/* Another has populated it */
2077 		pud_free(new);
2078 	else
2079 		pgd_populate(mm, pgd, new);
2080 	spin_unlock(&mm->page_table_lock);
2081 	return 0;
2082 }
2083 #endif /* __PAGETABLE_PUD_FOLDED */
2084 
2085 #ifndef __PAGETABLE_PMD_FOLDED
2086 /*
2087  * Allocate page middle directory.
2088  * We've already handled the fast-path in-line.
2089  */
2090 int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address)
2091 {
2092 	pmd_t *new = pmd_alloc_one(mm, address);
2093 	if (!new)
2094 		return -ENOMEM;
2095 
2096 	spin_lock(&mm->page_table_lock);
2097 #ifndef __ARCH_HAS_4LEVEL_HACK
2098 	if (pud_present(*pud))		/* Another has populated it */
2099 		pmd_free(new);
2100 	else
2101 		pud_populate(mm, pud, new);
2102 #else
2103 	if (pgd_present(*pud))		/* Another has populated it */
2104 		pmd_free(new);
2105 	else
2106 		pgd_populate(mm, pud, new);
2107 #endif /* __ARCH_HAS_4LEVEL_HACK */
2108 	spin_unlock(&mm->page_table_lock);
2109 	return 0;
2110 }
2111 #endif /* __PAGETABLE_PMD_FOLDED */
2112 
2113 int make_pages_present(unsigned long addr, unsigned long end)
2114 {
2115 	int ret, len, write;
2116 	struct vm_area_struct * vma;
2117 
2118 	vma = find_vma(current->mm, addr);
2119 	if (!vma)
2120 		return -1;
2121 	write = (vma->vm_flags & VM_WRITE) != 0;
2122 	if (addr >= end)
2123 		BUG();
2124 	if (end > vma->vm_end)
2125 		BUG();
2126 	len = (end+PAGE_SIZE-1)/PAGE_SIZE-addr/PAGE_SIZE;
2127 	ret = get_user_pages(current, current->mm, addr,
2128 			len, write, 0, NULL, NULL);
2129 	if (ret < 0)
2130 		return ret;
2131 	return ret == len ? 0 : -1;
2132 }
2133 
2134 /*
2135  * Map a vmalloc()-space virtual address to the physical page.
2136  */
2137 struct page * vmalloc_to_page(void * vmalloc_addr)
2138 {
2139 	unsigned long addr = (unsigned long) vmalloc_addr;
2140 	struct page *page = NULL;
2141 	pgd_t *pgd = pgd_offset_k(addr);
2142 	pud_t *pud;
2143 	pmd_t *pmd;
2144 	pte_t *ptep, pte;
2145 
2146 	if (!pgd_none(*pgd)) {
2147 		pud = pud_offset(pgd, addr);
2148 		if (!pud_none(*pud)) {
2149 			pmd = pmd_offset(pud, addr);
2150 			if (!pmd_none(*pmd)) {
2151 				ptep = pte_offset_map(pmd, addr);
2152 				pte = *ptep;
2153 				if (pte_present(pte))
2154 					page = pte_page(pte);
2155 				pte_unmap(ptep);
2156 			}
2157 		}
2158 	}
2159 	return page;
2160 }
2161 
2162 EXPORT_SYMBOL(vmalloc_to_page);
2163 
2164 /*
2165  * Map a vmalloc()-space virtual address to the physical page frame number.
2166  */
2167 unsigned long vmalloc_to_pfn(void * vmalloc_addr)
2168 {
2169 	return page_to_pfn(vmalloc_to_page(vmalloc_addr));
2170 }
2171 
2172 EXPORT_SYMBOL(vmalloc_to_pfn);
2173 
2174 #if !defined(__HAVE_ARCH_GATE_AREA)
2175 
2176 #if defined(AT_SYSINFO_EHDR)
2177 static struct vm_area_struct gate_vma;
2178 
2179 static int __init gate_vma_init(void)
2180 {
2181 	gate_vma.vm_mm = NULL;
2182 	gate_vma.vm_start = FIXADDR_USER_START;
2183 	gate_vma.vm_end = FIXADDR_USER_END;
2184 	gate_vma.vm_page_prot = PAGE_READONLY;
2185 	gate_vma.vm_flags = VM_RESERVED;
2186 	return 0;
2187 }
2188 __initcall(gate_vma_init);
2189 #endif
2190 
2191 struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
2192 {
2193 #ifdef AT_SYSINFO_EHDR
2194 	return &gate_vma;
2195 #else
2196 	return NULL;
2197 #endif
2198 }
2199 
2200 int in_gate_area_no_task(unsigned long addr)
2201 {
2202 #ifdef AT_SYSINFO_EHDR
2203 	if ((addr >= FIXADDR_USER_START) && (addr < FIXADDR_USER_END))
2204 		return 1;
2205 #endif
2206 	return 0;
2207 }
2208 
2209 #endif	/* __HAVE_ARCH_GATE_AREA */
2210