xref: /openbmc/linux/mm/memory.c (revision 9d56dd3b083a3bec56e9da35ce07baca81030b03)
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/ksm.h>
49 #include <linux/rmap.h>
50 #include <linux/module.h>
51 #include <linux/delayacct.h>
52 #include <linux/init.h>
53 #include <linux/writeback.h>
54 #include <linux/memcontrol.h>
55 #include <linux/mmu_notifier.h>
56 #include <linux/kallsyms.h>
57 #include <linux/swapops.h>
58 #include <linux/elf.h>
59 
60 #include <asm/io.h>
61 #include <asm/pgalloc.h>
62 #include <asm/uaccess.h>
63 #include <asm/tlb.h>
64 #include <asm/tlbflush.h>
65 #include <asm/pgtable.h>
66 
67 #include "internal.h"
68 
69 #ifndef CONFIG_NEED_MULTIPLE_NODES
70 /* use the per-pgdat data instead for discontigmem - mbligh */
71 unsigned long max_mapnr;
72 struct page *mem_map;
73 
74 EXPORT_SYMBOL(max_mapnr);
75 EXPORT_SYMBOL(mem_map);
76 #endif
77 
78 unsigned long num_physpages;
79 /*
80  * A number of key systems in x86 including ioremap() rely on the assumption
81  * that high_memory defines the upper bound on direct map memory, then end
82  * of ZONE_NORMAL.  Under CONFIG_DISCONTIG this means that max_low_pfn and
83  * highstart_pfn must be the same; there must be no gap between ZONE_NORMAL
84  * and ZONE_HIGHMEM.
85  */
86 void * high_memory;
87 
88 EXPORT_SYMBOL(num_physpages);
89 EXPORT_SYMBOL(high_memory);
90 
91 /*
92  * Randomize the address space (stacks, mmaps, brk, etc.).
93  *
94  * ( When CONFIG_COMPAT_BRK=y we exclude brk from randomization,
95  *   as ancient (libc5 based) binaries can segfault. )
96  */
97 int randomize_va_space __read_mostly =
98 #ifdef CONFIG_COMPAT_BRK
99 					1;
100 #else
101 					2;
102 #endif
103 
104 static int __init disable_randmaps(char *s)
105 {
106 	randomize_va_space = 0;
107 	return 1;
108 }
109 __setup("norandmaps", disable_randmaps);
110 
111 unsigned long zero_pfn __read_mostly;
112 unsigned long highest_memmap_pfn __read_mostly;
113 
114 /*
115  * CONFIG_MMU architectures set up ZERO_PAGE in their paging_init()
116  */
117 static int __init init_zero_pfn(void)
118 {
119 	zero_pfn = page_to_pfn(ZERO_PAGE(0));
120 	return 0;
121 }
122 core_initcall(init_zero_pfn);
123 
124 /*
125  * If a p?d_bad entry is found while walking page tables, report
126  * the error, before resetting entry to p?d_none.  Usually (but
127  * very seldom) called out from the p?d_none_or_clear_bad macros.
128  */
129 
130 void pgd_clear_bad(pgd_t *pgd)
131 {
132 	pgd_ERROR(*pgd);
133 	pgd_clear(pgd);
134 }
135 
136 void pud_clear_bad(pud_t *pud)
137 {
138 	pud_ERROR(*pud);
139 	pud_clear(pud);
140 }
141 
142 void pmd_clear_bad(pmd_t *pmd)
143 {
144 	pmd_ERROR(*pmd);
145 	pmd_clear(pmd);
146 }
147 
148 /*
149  * Note: this doesn't free the actual pages themselves. That
150  * has been handled earlier when unmapping all the memory regions.
151  */
152 static void free_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
153 			   unsigned long addr)
154 {
155 	pgtable_t token = pmd_pgtable(*pmd);
156 	pmd_clear(pmd);
157 	pte_free_tlb(tlb, token, addr);
158 	tlb->mm->nr_ptes--;
159 }
160 
161 static inline void free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
162 				unsigned long addr, unsigned long end,
163 				unsigned long floor, unsigned long ceiling)
164 {
165 	pmd_t *pmd;
166 	unsigned long next;
167 	unsigned long start;
168 
169 	start = addr;
170 	pmd = pmd_offset(pud, addr);
171 	do {
172 		next = pmd_addr_end(addr, end);
173 		if (pmd_none_or_clear_bad(pmd))
174 			continue;
175 		free_pte_range(tlb, pmd, addr);
176 	} while (pmd++, addr = next, addr != end);
177 
178 	start &= PUD_MASK;
179 	if (start < floor)
180 		return;
181 	if (ceiling) {
182 		ceiling &= PUD_MASK;
183 		if (!ceiling)
184 			return;
185 	}
186 	if (end - 1 > ceiling - 1)
187 		return;
188 
189 	pmd = pmd_offset(pud, start);
190 	pud_clear(pud);
191 	pmd_free_tlb(tlb, pmd, start);
192 }
193 
194 static inline void free_pud_range(struct mmu_gather *tlb, pgd_t *pgd,
195 				unsigned long addr, unsigned long end,
196 				unsigned long floor, unsigned long ceiling)
197 {
198 	pud_t *pud;
199 	unsigned long next;
200 	unsigned long start;
201 
202 	start = addr;
203 	pud = pud_offset(pgd, addr);
204 	do {
205 		next = pud_addr_end(addr, end);
206 		if (pud_none_or_clear_bad(pud))
207 			continue;
208 		free_pmd_range(tlb, pud, addr, next, floor, ceiling);
209 	} while (pud++, addr = next, addr != end);
210 
211 	start &= PGDIR_MASK;
212 	if (start < floor)
213 		return;
214 	if (ceiling) {
215 		ceiling &= PGDIR_MASK;
216 		if (!ceiling)
217 			return;
218 	}
219 	if (end - 1 > ceiling - 1)
220 		return;
221 
222 	pud = pud_offset(pgd, start);
223 	pgd_clear(pgd);
224 	pud_free_tlb(tlb, pud, start);
225 }
226 
227 /*
228  * This function frees user-level page tables of a process.
229  *
230  * Must be called with pagetable lock held.
231  */
232 void free_pgd_range(struct mmu_gather *tlb,
233 			unsigned long addr, unsigned long end,
234 			unsigned long floor, unsigned long ceiling)
235 {
236 	pgd_t *pgd;
237 	unsigned long next;
238 	unsigned long start;
239 
240 	/*
241 	 * The next few lines have given us lots of grief...
242 	 *
243 	 * Why are we testing PMD* at this top level?  Because often
244 	 * there will be no work to do at all, and we'd prefer not to
245 	 * go all the way down to the bottom just to discover that.
246 	 *
247 	 * Why all these "- 1"s?  Because 0 represents both the bottom
248 	 * of the address space and the top of it (using -1 for the
249 	 * top wouldn't help much: the masks would do the wrong thing).
250 	 * The rule is that addr 0 and floor 0 refer to the bottom of
251 	 * the address space, but end 0 and ceiling 0 refer to the top
252 	 * Comparisons need to use "end - 1" and "ceiling - 1" (though
253 	 * that end 0 case should be mythical).
254 	 *
255 	 * Wherever addr is brought up or ceiling brought down, we must
256 	 * be careful to reject "the opposite 0" before it confuses the
257 	 * subsequent tests.  But what about where end is brought down
258 	 * by PMD_SIZE below? no, end can't go down to 0 there.
259 	 *
260 	 * Whereas we round start (addr) and ceiling down, by different
261 	 * masks at different levels, in order to test whether a table
262 	 * now has no other vmas using it, so can be freed, we don't
263 	 * bother to round floor or end up - the tests don't need that.
264 	 */
265 
266 	addr &= PMD_MASK;
267 	if (addr < floor) {
268 		addr += PMD_SIZE;
269 		if (!addr)
270 			return;
271 	}
272 	if (ceiling) {
273 		ceiling &= PMD_MASK;
274 		if (!ceiling)
275 			return;
276 	}
277 	if (end - 1 > ceiling - 1)
278 		end -= PMD_SIZE;
279 	if (addr > end - 1)
280 		return;
281 
282 	start = addr;
283 	pgd = pgd_offset(tlb->mm, addr);
284 	do {
285 		next = pgd_addr_end(addr, end);
286 		if (pgd_none_or_clear_bad(pgd))
287 			continue;
288 		free_pud_range(tlb, pgd, addr, next, floor, ceiling);
289 	} while (pgd++, addr = next, addr != end);
290 }
291 
292 void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *vma,
293 		unsigned long floor, unsigned long ceiling)
294 {
295 	while (vma) {
296 		struct vm_area_struct *next = vma->vm_next;
297 		unsigned long addr = vma->vm_start;
298 
299 		/*
300 		 * Hide vma from rmap and truncate_pagecache before freeing
301 		 * pgtables
302 		 */
303 		anon_vma_unlink(vma);
304 		unlink_file_vma(vma);
305 
306 		if (is_vm_hugetlb_page(vma)) {
307 			hugetlb_free_pgd_range(tlb, addr, vma->vm_end,
308 				floor, next? next->vm_start: ceiling);
309 		} else {
310 			/*
311 			 * Optimization: gather nearby vmas into one call down
312 			 */
313 			while (next && next->vm_start <= vma->vm_end + PMD_SIZE
314 			       && !is_vm_hugetlb_page(next)) {
315 				vma = next;
316 				next = vma->vm_next;
317 				anon_vma_unlink(vma);
318 				unlink_file_vma(vma);
319 			}
320 			free_pgd_range(tlb, addr, vma->vm_end,
321 				floor, next? next->vm_start: ceiling);
322 		}
323 		vma = next;
324 	}
325 }
326 
327 int __pte_alloc(struct mm_struct *mm, pmd_t *pmd, unsigned long address)
328 {
329 	pgtable_t new = pte_alloc_one(mm, address);
330 	if (!new)
331 		return -ENOMEM;
332 
333 	/*
334 	 * Ensure all pte setup (eg. pte page lock and page clearing) are
335 	 * visible before the pte is made visible to other CPUs by being
336 	 * put into page tables.
337 	 *
338 	 * The other side of the story is the pointer chasing in the page
339 	 * table walking code (when walking the page table without locking;
340 	 * ie. most of the time). Fortunately, these data accesses consist
341 	 * of a chain of data-dependent loads, meaning most CPUs (alpha
342 	 * being the notable exception) will already guarantee loads are
343 	 * seen in-order. See the alpha page table accessors for the
344 	 * smp_read_barrier_depends() barriers in page table walking code.
345 	 */
346 	smp_wmb(); /* Could be smp_wmb__xxx(before|after)_spin_lock */
347 
348 	spin_lock(&mm->page_table_lock);
349 	if (!pmd_present(*pmd)) {	/* Has another populated it ? */
350 		mm->nr_ptes++;
351 		pmd_populate(mm, pmd, new);
352 		new = NULL;
353 	}
354 	spin_unlock(&mm->page_table_lock);
355 	if (new)
356 		pte_free(mm, new);
357 	return 0;
358 }
359 
360 int __pte_alloc_kernel(pmd_t *pmd, unsigned long address)
361 {
362 	pte_t *new = pte_alloc_one_kernel(&init_mm, address);
363 	if (!new)
364 		return -ENOMEM;
365 
366 	smp_wmb(); /* See comment in __pte_alloc */
367 
368 	spin_lock(&init_mm.page_table_lock);
369 	if (!pmd_present(*pmd)) {	/* Has another populated it ? */
370 		pmd_populate_kernel(&init_mm, pmd, new);
371 		new = NULL;
372 	}
373 	spin_unlock(&init_mm.page_table_lock);
374 	if (new)
375 		pte_free_kernel(&init_mm, new);
376 	return 0;
377 }
378 
379 static inline void add_mm_rss(struct mm_struct *mm, int file_rss, int anon_rss)
380 {
381 	if (file_rss)
382 		add_mm_counter(mm, file_rss, file_rss);
383 	if (anon_rss)
384 		add_mm_counter(mm, anon_rss, anon_rss);
385 }
386 
387 /*
388  * This function is called to print an error when a bad pte
389  * is found. For example, we might have a PFN-mapped pte in
390  * a region that doesn't allow it.
391  *
392  * The calling function must still handle the error.
393  */
394 static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
395 			  pte_t pte, struct page *page)
396 {
397 	pgd_t *pgd = pgd_offset(vma->vm_mm, addr);
398 	pud_t *pud = pud_offset(pgd, addr);
399 	pmd_t *pmd = pmd_offset(pud, addr);
400 	struct address_space *mapping;
401 	pgoff_t index;
402 	static unsigned long resume;
403 	static unsigned long nr_shown;
404 	static unsigned long nr_unshown;
405 
406 	/*
407 	 * Allow a burst of 60 reports, then keep quiet for that minute;
408 	 * or allow a steady drip of one report per second.
409 	 */
410 	if (nr_shown == 60) {
411 		if (time_before(jiffies, resume)) {
412 			nr_unshown++;
413 			return;
414 		}
415 		if (nr_unshown) {
416 			printk(KERN_ALERT
417 				"BUG: Bad page map: %lu messages suppressed\n",
418 				nr_unshown);
419 			nr_unshown = 0;
420 		}
421 		nr_shown = 0;
422 	}
423 	if (nr_shown++ == 0)
424 		resume = jiffies + 60 * HZ;
425 
426 	mapping = vma->vm_file ? vma->vm_file->f_mapping : NULL;
427 	index = linear_page_index(vma, addr);
428 
429 	printk(KERN_ALERT
430 		"BUG: Bad page map in process %s  pte:%08llx pmd:%08llx\n",
431 		current->comm,
432 		(long long)pte_val(pte), (long long)pmd_val(*pmd));
433 	if (page) {
434 		printk(KERN_ALERT
435 		"page:%p flags:%p count:%d mapcount:%d mapping:%p index:%lx\n",
436 		page, (void *)page->flags, page_count(page),
437 		page_mapcount(page), page->mapping, page->index);
438 	}
439 	printk(KERN_ALERT
440 		"addr:%p vm_flags:%08lx anon_vma:%p mapping:%p index:%lx\n",
441 		(void *)addr, vma->vm_flags, vma->anon_vma, mapping, index);
442 	/*
443 	 * Choose text because data symbols depend on CONFIG_KALLSYMS_ALL=y
444 	 */
445 	if (vma->vm_ops)
446 		print_symbol(KERN_ALERT "vma->vm_ops->fault: %s\n",
447 				(unsigned long)vma->vm_ops->fault);
448 	if (vma->vm_file && vma->vm_file->f_op)
449 		print_symbol(KERN_ALERT "vma->vm_file->f_op->mmap: %s\n",
450 				(unsigned long)vma->vm_file->f_op->mmap);
451 	dump_stack();
452 	add_taint(TAINT_BAD_PAGE);
453 }
454 
455 static inline int is_cow_mapping(unsigned int flags)
456 {
457 	return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
458 }
459 
460 #ifndef is_zero_pfn
461 static inline int is_zero_pfn(unsigned long pfn)
462 {
463 	return pfn == zero_pfn;
464 }
465 #endif
466 
467 #ifndef my_zero_pfn
468 static inline unsigned long my_zero_pfn(unsigned long addr)
469 {
470 	return zero_pfn;
471 }
472 #endif
473 
474 /*
475  * vm_normal_page -- This function gets the "struct page" associated with a pte.
476  *
477  * "Special" mappings do not wish to be associated with a "struct page" (either
478  * it doesn't exist, or it exists but they don't want to touch it). In this
479  * case, NULL is returned here. "Normal" mappings do have a struct page.
480  *
481  * There are 2 broad cases. Firstly, an architecture may define a pte_special()
482  * pte bit, in which case this function is trivial. Secondly, an architecture
483  * may not have a spare pte bit, which requires a more complicated scheme,
484  * described below.
485  *
486  * A raw VM_PFNMAP mapping (ie. one that is not COWed) is always considered a
487  * special mapping (even if there are underlying and valid "struct pages").
488  * COWed pages of a VM_PFNMAP are always normal.
489  *
490  * The way we recognize COWed pages within VM_PFNMAP mappings is through the
491  * rules set up by "remap_pfn_range()": the vma will have the VM_PFNMAP bit
492  * set, and the vm_pgoff will point to the first PFN mapped: thus every special
493  * mapping will always honor the rule
494  *
495  *	pfn_of_page == vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT)
496  *
497  * And for normal mappings this is false.
498  *
499  * This restricts such mappings to be a linear translation from virtual address
500  * to pfn. To get around this restriction, we allow arbitrary mappings so long
501  * as the vma is not a COW mapping; in that case, we know that all ptes are
502  * special (because none can have been COWed).
503  *
504  *
505  * In order to support COW of arbitrary special mappings, we have VM_MIXEDMAP.
506  *
507  * VM_MIXEDMAP mappings can likewise contain memory with or without "struct
508  * page" backing, however the difference is that _all_ pages with a struct
509  * page (that is, those where pfn_valid is true) are refcounted and considered
510  * normal pages by the VM. The disadvantage is that pages are refcounted
511  * (which can be slower and simply not an option for some PFNMAP users). The
512  * advantage is that we don't have to follow the strict linearity rule of
513  * PFNMAP mappings in order to support COWable mappings.
514  *
515  */
516 #ifdef __HAVE_ARCH_PTE_SPECIAL
517 # define HAVE_PTE_SPECIAL 1
518 #else
519 # define HAVE_PTE_SPECIAL 0
520 #endif
521 struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
522 				pte_t pte)
523 {
524 	unsigned long pfn = pte_pfn(pte);
525 
526 	if (HAVE_PTE_SPECIAL) {
527 		if (likely(!pte_special(pte)))
528 			goto check_pfn;
529 		if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
530 			return NULL;
531 		if (!is_zero_pfn(pfn))
532 			print_bad_pte(vma, addr, pte, NULL);
533 		return NULL;
534 	}
535 
536 	/* !HAVE_PTE_SPECIAL case follows: */
537 
538 	if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
539 		if (vma->vm_flags & VM_MIXEDMAP) {
540 			if (!pfn_valid(pfn))
541 				return NULL;
542 			goto out;
543 		} else {
544 			unsigned long off;
545 			off = (addr - vma->vm_start) >> PAGE_SHIFT;
546 			if (pfn == vma->vm_pgoff + off)
547 				return NULL;
548 			if (!is_cow_mapping(vma->vm_flags))
549 				return NULL;
550 		}
551 	}
552 
553 	if (is_zero_pfn(pfn))
554 		return NULL;
555 check_pfn:
556 	if (unlikely(pfn > highest_memmap_pfn)) {
557 		print_bad_pte(vma, addr, pte, NULL);
558 		return NULL;
559 	}
560 
561 	/*
562 	 * NOTE! We still have PageReserved() pages in the page tables.
563 	 * eg. VDSO mappings can cause them to exist.
564 	 */
565 out:
566 	return pfn_to_page(pfn);
567 }
568 
569 /*
570  * copy one vm_area from one task to the other. Assumes the page tables
571  * already present in the new task to be cleared in the whole range
572  * covered by this vma.
573  */
574 
575 static inline unsigned long
576 copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
577 		pte_t *dst_pte, pte_t *src_pte, struct vm_area_struct *vma,
578 		unsigned long addr, int *rss)
579 {
580 	unsigned long vm_flags = vma->vm_flags;
581 	pte_t pte = *src_pte;
582 	struct page *page;
583 
584 	/* pte contains position in swap or file, so copy. */
585 	if (unlikely(!pte_present(pte))) {
586 		if (!pte_file(pte)) {
587 			swp_entry_t entry = pte_to_swp_entry(pte);
588 
589 			if (swap_duplicate(entry) < 0)
590 				return entry.val;
591 
592 			/* make sure dst_mm is on swapoff's mmlist. */
593 			if (unlikely(list_empty(&dst_mm->mmlist))) {
594 				spin_lock(&mmlist_lock);
595 				if (list_empty(&dst_mm->mmlist))
596 					list_add(&dst_mm->mmlist,
597 						 &src_mm->mmlist);
598 				spin_unlock(&mmlist_lock);
599 			}
600 			if (is_write_migration_entry(entry) &&
601 					is_cow_mapping(vm_flags)) {
602 				/*
603 				 * COW mappings require pages in both parent
604 				 * and child to be set to read.
605 				 */
606 				make_migration_entry_read(&entry);
607 				pte = swp_entry_to_pte(entry);
608 				set_pte_at(src_mm, addr, src_pte, pte);
609 			}
610 		}
611 		goto out_set_pte;
612 	}
613 
614 	/*
615 	 * If it's a COW mapping, write protect it both
616 	 * in the parent and the child
617 	 */
618 	if (is_cow_mapping(vm_flags)) {
619 		ptep_set_wrprotect(src_mm, addr, src_pte);
620 		pte = pte_wrprotect(pte);
621 	}
622 
623 	/*
624 	 * If it's a shared mapping, mark it clean in
625 	 * the child
626 	 */
627 	if (vm_flags & VM_SHARED)
628 		pte = pte_mkclean(pte);
629 	pte = pte_mkold(pte);
630 
631 	page = vm_normal_page(vma, addr, pte);
632 	if (page) {
633 		get_page(page);
634 		page_dup_rmap(page);
635 		rss[PageAnon(page)]++;
636 	}
637 
638 out_set_pte:
639 	set_pte_at(dst_mm, addr, dst_pte, pte);
640 	return 0;
641 }
642 
643 static int copy_pte_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
644 		pmd_t *dst_pmd, pmd_t *src_pmd, struct vm_area_struct *vma,
645 		unsigned long addr, unsigned long end)
646 {
647 	pte_t *orig_src_pte, *orig_dst_pte;
648 	pte_t *src_pte, *dst_pte;
649 	spinlock_t *src_ptl, *dst_ptl;
650 	int progress = 0;
651 	int rss[2];
652 	swp_entry_t entry = (swp_entry_t){0};
653 
654 again:
655 	rss[1] = rss[0] = 0;
656 	dst_pte = pte_alloc_map_lock(dst_mm, dst_pmd, addr, &dst_ptl);
657 	if (!dst_pte)
658 		return -ENOMEM;
659 	src_pte = pte_offset_map_nested(src_pmd, addr);
660 	src_ptl = pte_lockptr(src_mm, src_pmd);
661 	spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
662 	orig_src_pte = src_pte;
663 	orig_dst_pte = dst_pte;
664 	arch_enter_lazy_mmu_mode();
665 
666 	do {
667 		/*
668 		 * We are holding two locks at this point - either of them
669 		 * could generate latencies in another task on another CPU.
670 		 */
671 		if (progress >= 32) {
672 			progress = 0;
673 			if (need_resched() ||
674 			    spin_needbreak(src_ptl) || spin_needbreak(dst_ptl))
675 				break;
676 		}
677 		if (pte_none(*src_pte)) {
678 			progress++;
679 			continue;
680 		}
681 		entry.val = copy_one_pte(dst_mm, src_mm, dst_pte, src_pte,
682 							vma, addr, rss);
683 		if (entry.val)
684 			break;
685 		progress += 8;
686 	} while (dst_pte++, src_pte++, addr += PAGE_SIZE, addr != end);
687 
688 	arch_leave_lazy_mmu_mode();
689 	spin_unlock(src_ptl);
690 	pte_unmap_nested(orig_src_pte);
691 	add_mm_rss(dst_mm, rss[0], rss[1]);
692 	pte_unmap_unlock(orig_dst_pte, dst_ptl);
693 	cond_resched();
694 
695 	if (entry.val) {
696 		if (add_swap_count_continuation(entry, GFP_KERNEL) < 0)
697 			return -ENOMEM;
698 		progress = 0;
699 	}
700 	if (addr != end)
701 		goto again;
702 	return 0;
703 }
704 
705 static inline int copy_pmd_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
706 		pud_t *dst_pud, pud_t *src_pud, struct vm_area_struct *vma,
707 		unsigned long addr, unsigned long end)
708 {
709 	pmd_t *src_pmd, *dst_pmd;
710 	unsigned long next;
711 
712 	dst_pmd = pmd_alloc(dst_mm, dst_pud, addr);
713 	if (!dst_pmd)
714 		return -ENOMEM;
715 	src_pmd = pmd_offset(src_pud, addr);
716 	do {
717 		next = pmd_addr_end(addr, end);
718 		if (pmd_none_or_clear_bad(src_pmd))
719 			continue;
720 		if (copy_pte_range(dst_mm, src_mm, dst_pmd, src_pmd,
721 						vma, addr, next))
722 			return -ENOMEM;
723 	} while (dst_pmd++, src_pmd++, addr = next, addr != end);
724 	return 0;
725 }
726 
727 static inline int copy_pud_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
728 		pgd_t *dst_pgd, pgd_t *src_pgd, struct vm_area_struct *vma,
729 		unsigned long addr, unsigned long end)
730 {
731 	pud_t *src_pud, *dst_pud;
732 	unsigned long next;
733 
734 	dst_pud = pud_alloc(dst_mm, dst_pgd, addr);
735 	if (!dst_pud)
736 		return -ENOMEM;
737 	src_pud = pud_offset(src_pgd, addr);
738 	do {
739 		next = pud_addr_end(addr, end);
740 		if (pud_none_or_clear_bad(src_pud))
741 			continue;
742 		if (copy_pmd_range(dst_mm, src_mm, dst_pud, src_pud,
743 						vma, addr, next))
744 			return -ENOMEM;
745 	} while (dst_pud++, src_pud++, addr = next, addr != end);
746 	return 0;
747 }
748 
749 int copy_page_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
750 		struct vm_area_struct *vma)
751 {
752 	pgd_t *src_pgd, *dst_pgd;
753 	unsigned long next;
754 	unsigned long addr = vma->vm_start;
755 	unsigned long end = vma->vm_end;
756 	int ret;
757 
758 	/*
759 	 * Don't copy ptes where a page fault will fill them correctly.
760 	 * Fork becomes much lighter when there are big shared or private
761 	 * readonly mappings. The tradeoff is that copy_page_range is more
762 	 * efficient than faulting.
763 	 */
764 	if (!(vma->vm_flags & (VM_HUGETLB|VM_NONLINEAR|VM_PFNMAP|VM_INSERTPAGE))) {
765 		if (!vma->anon_vma)
766 			return 0;
767 	}
768 
769 	if (is_vm_hugetlb_page(vma))
770 		return copy_hugetlb_page_range(dst_mm, src_mm, vma);
771 
772 	if (unlikely(is_pfn_mapping(vma))) {
773 		/*
774 		 * We do not free on error cases below as remove_vma
775 		 * gets called on error from higher level routine
776 		 */
777 		ret = track_pfn_vma_copy(vma);
778 		if (ret)
779 			return ret;
780 	}
781 
782 	/*
783 	 * We need to invalidate the secondary MMU mappings only when
784 	 * there could be a permission downgrade on the ptes of the
785 	 * parent mm. And a permission downgrade will only happen if
786 	 * is_cow_mapping() returns true.
787 	 */
788 	if (is_cow_mapping(vma->vm_flags))
789 		mmu_notifier_invalidate_range_start(src_mm, addr, end);
790 
791 	ret = 0;
792 	dst_pgd = pgd_offset(dst_mm, addr);
793 	src_pgd = pgd_offset(src_mm, addr);
794 	do {
795 		next = pgd_addr_end(addr, end);
796 		if (pgd_none_or_clear_bad(src_pgd))
797 			continue;
798 		if (unlikely(copy_pud_range(dst_mm, src_mm, dst_pgd, src_pgd,
799 					    vma, addr, next))) {
800 			ret = -ENOMEM;
801 			break;
802 		}
803 	} while (dst_pgd++, src_pgd++, addr = next, addr != end);
804 
805 	if (is_cow_mapping(vma->vm_flags))
806 		mmu_notifier_invalidate_range_end(src_mm,
807 						  vma->vm_start, end);
808 	return ret;
809 }
810 
811 static unsigned long zap_pte_range(struct mmu_gather *tlb,
812 				struct vm_area_struct *vma, pmd_t *pmd,
813 				unsigned long addr, unsigned long end,
814 				long *zap_work, struct zap_details *details)
815 {
816 	struct mm_struct *mm = tlb->mm;
817 	pte_t *pte;
818 	spinlock_t *ptl;
819 	int file_rss = 0;
820 	int anon_rss = 0;
821 
822 	pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
823 	arch_enter_lazy_mmu_mode();
824 	do {
825 		pte_t ptent = *pte;
826 		if (pte_none(ptent)) {
827 			(*zap_work)--;
828 			continue;
829 		}
830 
831 		(*zap_work) -= PAGE_SIZE;
832 
833 		if (pte_present(ptent)) {
834 			struct page *page;
835 
836 			page = vm_normal_page(vma, addr, ptent);
837 			if (unlikely(details) && page) {
838 				/*
839 				 * unmap_shared_mapping_pages() wants to
840 				 * invalidate cache without truncating:
841 				 * unmap shared but keep private pages.
842 				 */
843 				if (details->check_mapping &&
844 				    details->check_mapping != page->mapping)
845 					continue;
846 				/*
847 				 * Each page->index must be checked when
848 				 * invalidating or truncating nonlinear.
849 				 */
850 				if (details->nonlinear_vma &&
851 				    (page->index < details->first_index ||
852 				     page->index > details->last_index))
853 					continue;
854 			}
855 			ptent = ptep_get_and_clear_full(mm, addr, pte,
856 							tlb->fullmm);
857 			tlb_remove_tlb_entry(tlb, pte, addr);
858 			if (unlikely(!page))
859 				continue;
860 			if (unlikely(details) && details->nonlinear_vma
861 			    && linear_page_index(details->nonlinear_vma,
862 						addr) != page->index)
863 				set_pte_at(mm, addr, pte,
864 					   pgoff_to_pte(page->index));
865 			if (PageAnon(page))
866 				anon_rss--;
867 			else {
868 				if (pte_dirty(ptent))
869 					set_page_dirty(page);
870 				if (pte_young(ptent) &&
871 				    likely(!VM_SequentialReadHint(vma)))
872 					mark_page_accessed(page);
873 				file_rss--;
874 			}
875 			page_remove_rmap(page);
876 			if (unlikely(page_mapcount(page) < 0))
877 				print_bad_pte(vma, addr, ptent, page);
878 			tlb_remove_page(tlb, page);
879 			continue;
880 		}
881 		/*
882 		 * If details->check_mapping, we leave swap entries;
883 		 * if details->nonlinear_vma, we leave file entries.
884 		 */
885 		if (unlikely(details))
886 			continue;
887 		if (pte_file(ptent)) {
888 			if (unlikely(!(vma->vm_flags & VM_NONLINEAR)))
889 				print_bad_pte(vma, addr, ptent, NULL);
890 		} else if
891 		  (unlikely(!free_swap_and_cache(pte_to_swp_entry(ptent))))
892 			print_bad_pte(vma, addr, ptent, NULL);
893 		pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
894 	} while (pte++, addr += PAGE_SIZE, (addr != end && *zap_work > 0));
895 
896 	add_mm_rss(mm, file_rss, anon_rss);
897 	arch_leave_lazy_mmu_mode();
898 	pte_unmap_unlock(pte - 1, ptl);
899 
900 	return addr;
901 }
902 
903 static inline unsigned long zap_pmd_range(struct mmu_gather *tlb,
904 				struct vm_area_struct *vma, pud_t *pud,
905 				unsigned long addr, unsigned long end,
906 				long *zap_work, struct zap_details *details)
907 {
908 	pmd_t *pmd;
909 	unsigned long next;
910 
911 	pmd = pmd_offset(pud, addr);
912 	do {
913 		next = pmd_addr_end(addr, end);
914 		if (pmd_none_or_clear_bad(pmd)) {
915 			(*zap_work)--;
916 			continue;
917 		}
918 		next = zap_pte_range(tlb, vma, pmd, addr, next,
919 						zap_work, details);
920 	} while (pmd++, addr = next, (addr != end && *zap_work > 0));
921 
922 	return addr;
923 }
924 
925 static inline unsigned long zap_pud_range(struct mmu_gather *tlb,
926 				struct vm_area_struct *vma, pgd_t *pgd,
927 				unsigned long addr, unsigned long end,
928 				long *zap_work, struct zap_details *details)
929 {
930 	pud_t *pud;
931 	unsigned long next;
932 
933 	pud = pud_offset(pgd, addr);
934 	do {
935 		next = pud_addr_end(addr, end);
936 		if (pud_none_or_clear_bad(pud)) {
937 			(*zap_work)--;
938 			continue;
939 		}
940 		next = zap_pmd_range(tlb, vma, pud, addr, next,
941 						zap_work, details);
942 	} while (pud++, addr = next, (addr != end && *zap_work > 0));
943 
944 	return addr;
945 }
946 
947 static unsigned long unmap_page_range(struct mmu_gather *tlb,
948 				struct vm_area_struct *vma,
949 				unsigned long addr, unsigned long end,
950 				long *zap_work, struct zap_details *details)
951 {
952 	pgd_t *pgd;
953 	unsigned long next;
954 
955 	if (details && !details->check_mapping && !details->nonlinear_vma)
956 		details = NULL;
957 
958 	BUG_ON(addr >= end);
959 	mem_cgroup_uncharge_start();
960 	tlb_start_vma(tlb, vma);
961 	pgd = pgd_offset(vma->vm_mm, addr);
962 	do {
963 		next = pgd_addr_end(addr, end);
964 		if (pgd_none_or_clear_bad(pgd)) {
965 			(*zap_work)--;
966 			continue;
967 		}
968 		next = zap_pud_range(tlb, vma, pgd, addr, next,
969 						zap_work, details);
970 	} while (pgd++, addr = next, (addr != end && *zap_work > 0));
971 	tlb_end_vma(tlb, vma);
972 	mem_cgroup_uncharge_end();
973 
974 	return addr;
975 }
976 
977 #ifdef CONFIG_PREEMPT
978 # define ZAP_BLOCK_SIZE	(8 * PAGE_SIZE)
979 #else
980 /* No preempt: go for improved straight-line efficiency */
981 # define ZAP_BLOCK_SIZE	(1024 * PAGE_SIZE)
982 #endif
983 
984 /**
985  * unmap_vmas - unmap a range of memory covered by a list of vma's
986  * @tlbp: address of the caller's struct mmu_gather
987  * @vma: the starting vma
988  * @start_addr: virtual address at which to start unmapping
989  * @end_addr: virtual address at which to end unmapping
990  * @nr_accounted: Place number of unmapped pages in vm-accountable vma's here
991  * @details: details of nonlinear truncation or shared cache invalidation
992  *
993  * Returns the end address of the unmapping (restart addr if interrupted).
994  *
995  * Unmap all pages in the vma list.
996  *
997  * We aim to not hold locks for too long (for scheduling latency reasons).
998  * So zap pages in ZAP_BLOCK_SIZE bytecounts.  This means we need to
999  * return the ending mmu_gather to the caller.
1000  *
1001  * Only addresses between `start' and `end' will be unmapped.
1002  *
1003  * The VMA list must be sorted in ascending virtual address order.
1004  *
1005  * unmap_vmas() assumes that the caller will flush the whole unmapped address
1006  * range after unmap_vmas() returns.  So the only responsibility here is to
1007  * ensure that any thus-far unmapped pages are flushed before unmap_vmas()
1008  * drops the lock and schedules.
1009  */
1010 unsigned long unmap_vmas(struct mmu_gather **tlbp,
1011 		struct vm_area_struct *vma, unsigned long start_addr,
1012 		unsigned long end_addr, unsigned long *nr_accounted,
1013 		struct zap_details *details)
1014 {
1015 	long zap_work = ZAP_BLOCK_SIZE;
1016 	unsigned long tlb_start = 0;	/* For tlb_finish_mmu */
1017 	int tlb_start_valid = 0;
1018 	unsigned long start = start_addr;
1019 	spinlock_t *i_mmap_lock = details? details->i_mmap_lock: NULL;
1020 	int fullmm = (*tlbp)->fullmm;
1021 	struct mm_struct *mm = vma->vm_mm;
1022 
1023 	mmu_notifier_invalidate_range_start(mm, start_addr, end_addr);
1024 	for ( ; vma && vma->vm_start < end_addr; vma = vma->vm_next) {
1025 		unsigned long end;
1026 
1027 		start = max(vma->vm_start, start_addr);
1028 		if (start >= vma->vm_end)
1029 			continue;
1030 		end = min(vma->vm_end, end_addr);
1031 		if (end <= vma->vm_start)
1032 			continue;
1033 
1034 		if (vma->vm_flags & VM_ACCOUNT)
1035 			*nr_accounted += (end - start) >> PAGE_SHIFT;
1036 
1037 		if (unlikely(is_pfn_mapping(vma)))
1038 			untrack_pfn_vma(vma, 0, 0);
1039 
1040 		while (start != end) {
1041 			if (!tlb_start_valid) {
1042 				tlb_start = start;
1043 				tlb_start_valid = 1;
1044 			}
1045 
1046 			if (unlikely(is_vm_hugetlb_page(vma))) {
1047 				/*
1048 				 * It is undesirable to test vma->vm_file as it
1049 				 * should be non-null for valid hugetlb area.
1050 				 * However, vm_file will be NULL in the error
1051 				 * cleanup path of do_mmap_pgoff. When
1052 				 * hugetlbfs ->mmap method fails,
1053 				 * do_mmap_pgoff() nullifies vma->vm_file
1054 				 * before calling this function to clean up.
1055 				 * Since no pte has actually been setup, it is
1056 				 * safe to do nothing in this case.
1057 				 */
1058 				if (vma->vm_file) {
1059 					unmap_hugepage_range(vma, start, end, NULL);
1060 					zap_work -= (end - start) /
1061 					pages_per_huge_page(hstate_vma(vma));
1062 				}
1063 
1064 				start = end;
1065 			} else
1066 				start = unmap_page_range(*tlbp, vma,
1067 						start, end, &zap_work, details);
1068 
1069 			if (zap_work > 0) {
1070 				BUG_ON(start != end);
1071 				break;
1072 			}
1073 
1074 			tlb_finish_mmu(*tlbp, tlb_start, start);
1075 
1076 			if (need_resched() ||
1077 				(i_mmap_lock && spin_needbreak(i_mmap_lock))) {
1078 				if (i_mmap_lock) {
1079 					*tlbp = NULL;
1080 					goto out;
1081 				}
1082 				cond_resched();
1083 			}
1084 
1085 			*tlbp = tlb_gather_mmu(vma->vm_mm, fullmm);
1086 			tlb_start_valid = 0;
1087 			zap_work = ZAP_BLOCK_SIZE;
1088 		}
1089 	}
1090 out:
1091 	mmu_notifier_invalidate_range_end(mm, start_addr, end_addr);
1092 	return start;	/* which is now the end (or restart) address */
1093 }
1094 
1095 /**
1096  * zap_page_range - remove user pages in a given range
1097  * @vma: vm_area_struct holding the applicable pages
1098  * @address: starting address of pages to zap
1099  * @size: number of bytes to zap
1100  * @details: details of nonlinear truncation or shared cache invalidation
1101  */
1102 unsigned long zap_page_range(struct vm_area_struct *vma, unsigned long address,
1103 		unsigned long size, struct zap_details *details)
1104 {
1105 	struct mm_struct *mm = vma->vm_mm;
1106 	struct mmu_gather *tlb;
1107 	unsigned long end = address + size;
1108 	unsigned long nr_accounted = 0;
1109 
1110 	lru_add_drain();
1111 	tlb = tlb_gather_mmu(mm, 0);
1112 	update_hiwater_rss(mm);
1113 	end = unmap_vmas(&tlb, vma, address, end, &nr_accounted, details);
1114 	if (tlb)
1115 		tlb_finish_mmu(tlb, address, end);
1116 	return end;
1117 }
1118 
1119 /**
1120  * zap_vma_ptes - remove ptes mapping the vma
1121  * @vma: vm_area_struct holding ptes to be zapped
1122  * @address: starting address of pages to zap
1123  * @size: number of bytes to zap
1124  *
1125  * This function only unmaps ptes assigned to VM_PFNMAP vmas.
1126  *
1127  * The entire address range must be fully contained within the vma.
1128  *
1129  * Returns 0 if successful.
1130  */
1131 int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
1132 		unsigned long size)
1133 {
1134 	if (address < vma->vm_start || address + size > vma->vm_end ||
1135 	    		!(vma->vm_flags & VM_PFNMAP))
1136 		return -1;
1137 	zap_page_range(vma, address, size, NULL);
1138 	return 0;
1139 }
1140 EXPORT_SYMBOL_GPL(zap_vma_ptes);
1141 
1142 /*
1143  * Do a quick page-table lookup for a single page.
1144  */
1145 struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
1146 			unsigned int flags)
1147 {
1148 	pgd_t *pgd;
1149 	pud_t *pud;
1150 	pmd_t *pmd;
1151 	pte_t *ptep, pte;
1152 	spinlock_t *ptl;
1153 	struct page *page;
1154 	struct mm_struct *mm = vma->vm_mm;
1155 
1156 	page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
1157 	if (!IS_ERR(page)) {
1158 		BUG_ON(flags & FOLL_GET);
1159 		goto out;
1160 	}
1161 
1162 	page = NULL;
1163 	pgd = pgd_offset(mm, address);
1164 	if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
1165 		goto no_page_table;
1166 
1167 	pud = pud_offset(pgd, address);
1168 	if (pud_none(*pud))
1169 		goto no_page_table;
1170 	if (pud_huge(*pud)) {
1171 		BUG_ON(flags & FOLL_GET);
1172 		page = follow_huge_pud(mm, address, pud, flags & FOLL_WRITE);
1173 		goto out;
1174 	}
1175 	if (unlikely(pud_bad(*pud)))
1176 		goto no_page_table;
1177 
1178 	pmd = pmd_offset(pud, address);
1179 	if (pmd_none(*pmd))
1180 		goto no_page_table;
1181 	if (pmd_huge(*pmd)) {
1182 		BUG_ON(flags & FOLL_GET);
1183 		page = follow_huge_pmd(mm, address, pmd, flags & FOLL_WRITE);
1184 		goto out;
1185 	}
1186 	if (unlikely(pmd_bad(*pmd)))
1187 		goto no_page_table;
1188 
1189 	ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
1190 
1191 	pte = *ptep;
1192 	if (!pte_present(pte))
1193 		goto no_page;
1194 	if ((flags & FOLL_WRITE) && !pte_write(pte))
1195 		goto unlock;
1196 
1197 	page = vm_normal_page(vma, address, pte);
1198 	if (unlikely(!page)) {
1199 		if ((flags & FOLL_DUMP) ||
1200 		    !is_zero_pfn(pte_pfn(pte)))
1201 			goto bad_page;
1202 		page = pte_page(pte);
1203 	}
1204 
1205 	if (flags & FOLL_GET)
1206 		get_page(page);
1207 	if (flags & FOLL_TOUCH) {
1208 		if ((flags & FOLL_WRITE) &&
1209 		    !pte_dirty(pte) && !PageDirty(page))
1210 			set_page_dirty(page);
1211 		/*
1212 		 * pte_mkyoung() would be more correct here, but atomic care
1213 		 * is needed to avoid losing the dirty bit: it is easier to use
1214 		 * mark_page_accessed().
1215 		 */
1216 		mark_page_accessed(page);
1217 	}
1218 unlock:
1219 	pte_unmap_unlock(ptep, ptl);
1220 out:
1221 	return page;
1222 
1223 bad_page:
1224 	pte_unmap_unlock(ptep, ptl);
1225 	return ERR_PTR(-EFAULT);
1226 
1227 no_page:
1228 	pte_unmap_unlock(ptep, ptl);
1229 	if (!pte_none(pte))
1230 		return page;
1231 
1232 no_page_table:
1233 	/*
1234 	 * When core dumping an enormous anonymous area that nobody
1235 	 * has touched so far, we don't want to allocate unnecessary pages or
1236 	 * page tables.  Return error instead of NULL to skip handle_mm_fault,
1237 	 * then get_dump_page() will return NULL to leave a hole in the dump.
1238 	 * But we can only make this optimization where a hole would surely
1239 	 * be zero-filled if handle_mm_fault() actually did handle it.
1240 	 */
1241 	if ((flags & FOLL_DUMP) &&
1242 	    (!vma->vm_ops || !vma->vm_ops->fault))
1243 		return ERR_PTR(-EFAULT);
1244 	return page;
1245 }
1246 
1247 int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
1248 		     unsigned long start, int nr_pages, unsigned int gup_flags,
1249 		     struct page **pages, struct vm_area_struct **vmas)
1250 {
1251 	int i;
1252 	unsigned long vm_flags;
1253 
1254 	if (nr_pages <= 0)
1255 		return 0;
1256 
1257 	VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
1258 
1259 	/*
1260 	 * Require read or write permissions.
1261 	 * If FOLL_FORCE is set, we only require the "MAY" flags.
1262 	 */
1263 	vm_flags  = (gup_flags & FOLL_WRITE) ?
1264 			(VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
1265 	vm_flags &= (gup_flags & FOLL_FORCE) ?
1266 			(VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
1267 	i = 0;
1268 
1269 	do {
1270 		struct vm_area_struct *vma;
1271 
1272 		vma = find_extend_vma(mm, start);
1273 		if (!vma && in_gate_area(tsk, start)) {
1274 			unsigned long pg = start & PAGE_MASK;
1275 			struct vm_area_struct *gate_vma = get_gate_vma(tsk);
1276 			pgd_t *pgd;
1277 			pud_t *pud;
1278 			pmd_t *pmd;
1279 			pte_t *pte;
1280 
1281 			/* user gate pages are read-only */
1282 			if (gup_flags & FOLL_WRITE)
1283 				return i ? : -EFAULT;
1284 			if (pg > TASK_SIZE)
1285 				pgd = pgd_offset_k(pg);
1286 			else
1287 				pgd = pgd_offset_gate(mm, pg);
1288 			BUG_ON(pgd_none(*pgd));
1289 			pud = pud_offset(pgd, pg);
1290 			BUG_ON(pud_none(*pud));
1291 			pmd = pmd_offset(pud, pg);
1292 			if (pmd_none(*pmd))
1293 				return i ? : -EFAULT;
1294 			pte = pte_offset_map(pmd, pg);
1295 			if (pte_none(*pte)) {
1296 				pte_unmap(pte);
1297 				return i ? : -EFAULT;
1298 			}
1299 			if (pages) {
1300 				struct page *page = vm_normal_page(gate_vma, start, *pte);
1301 				pages[i] = page;
1302 				if (page)
1303 					get_page(page);
1304 			}
1305 			pte_unmap(pte);
1306 			if (vmas)
1307 				vmas[i] = gate_vma;
1308 			i++;
1309 			start += PAGE_SIZE;
1310 			nr_pages--;
1311 			continue;
1312 		}
1313 
1314 		if (!vma ||
1315 		    (vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
1316 		    !(vm_flags & vma->vm_flags))
1317 			return i ? : -EFAULT;
1318 
1319 		if (is_vm_hugetlb_page(vma)) {
1320 			i = follow_hugetlb_page(mm, vma, pages, vmas,
1321 					&start, &nr_pages, i, gup_flags);
1322 			continue;
1323 		}
1324 
1325 		do {
1326 			struct page *page;
1327 			unsigned int foll_flags = gup_flags;
1328 
1329 			/*
1330 			 * If we have a pending SIGKILL, don't keep faulting
1331 			 * pages and potentially allocating memory.
1332 			 */
1333 			if (unlikely(fatal_signal_pending(current)))
1334 				return i ? i : -ERESTARTSYS;
1335 
1336 			cond_resched();
1337 			while (!(page = follow_page(vma, start, foll_flags))) {
1338 				int ret;
1339 
1340 				ret = handle_mm_fault(mm, vma, start,
1341 					(foll_flags & FOLL_WRITE) ?
1342 					FAULT_FLAG_WRITE : 0);
1343 
1344 				if (ret & VM_FAULT_ERROR) {
1345 					if (ret & VM_FAULT_OOM)
1346 						return i ? i : -ENOMEM;
1347 					if (ret &
1348 					    (VM_FAULT_HWPOISON|VM_FAULT_SIGBUS))
1349 						return i ? i : -EFAULT;
1350 					BUG();
1351 				}
1352 				if (ret & VM_FAULT_MAJOR)
1353 					tsk->maj_flt++;
1354 				else
1355 					tsk->min_flt++;
1356 
1357 				/*
1358 				 * The VM_FAULT_WRITE bit tells us that
1359 				 * do_wp_page has broken COW when necessary,
1360 				 * even if maybe_mkwrite decided not to set
1361 				 * pte_write. We can thus safely do subsequent
1362 				 * page lookups as if they were reads. But only
1363 				 * do so when looping for pte_write is futile:
1364 				 * in some cases userspace may also be wanting
1365 				 * to write to the gotten user page, which a
1366 				 * read fault here might prevent (a readonly
1367 				 * page might get reCOWed by userspace write).
1368 				 */
1369 				if ((ret & VM_FAULT_WRITE) &&
1370 				    !(vma->vm_flags & VM_WRITE))
1371 					foll_flags &= ~FOLL_WRITE;
1372 
1373 				cond_resched();
1374 			}
1375 			if (IS_ERR(page))
1376 				return i ? i : PTR_ERR(page);
1377 			if (pages) {
1378 				pages[i] = page;
1379 
1380 				flush_anon_page(vma, page, start);
1381 				flush_dcache_page(page);
1382 			}
1383 			if (vmas)
1384 				vmas[i] = vma;
1385 			i++;
1386 			start += PAGE_SIZE;
1387 			nr_pages--;
1388 		} while (nr_pages && start < vma->vm_end);
1389 	} while (nr_pages);
1390 	return i;
1391 }
1392 
1393 /**
1394  * get_user_pages() - pin user pages in memory
1395  * @tsk:	task_struct of target task
1396  * @mm:		mm_struct of target mm
1397  * @start:	starting user address
1398  * @nr_pages:	number of pages from start to pin
1399  * @write:	whether pages will be written to by the caller
1400  * @force:	whether to force write access even if user mapping is
1401  *		readonly. This will result in the page being COWed even
1402  *		in MAP_SHARED mappings. You do not want this.
1403  * @pages:	array that receives pointers to the pages pinned.
1404  *		Should be at least nr_pages long. Or NULL, if caller
1405  *		only intends to ensure the pages are faulted in.
1406  * @vmas:	array of pointers to vmas corresponding to each page.
1407  *		Or NULL if the caller does not require them.
1408  *
1409  * Returns number of pages pinned. This may be fewer than the number
1410  * requested. If nr_pages is 0 or negative, returns 0. If no pages
1411  * were pinned, returns -errno. Each page returned must be released
1412  * with a put_page() call when it is finished with. vmas will only
1413  * remain valid while mmap_sem is held.
1414  *
1415  * Must be called with mmap_sem held for read or write.
1416  *
1417  * get_user_pages walks a process's page tables and takes a reference to
1418  * each struct page that each user address corresponds to at a given
1419  * instant. That is, it takes the page that would be accessed if a user
1420  * thread accesses the given user virtual address at that instant.
1421  *
1422  * This does not guarantee that the page exists in the user mappings when
1423  * get_user_pages returns, and there may even be a completely different
1424  * page there in some cases (eg. if mmapped pagecache has been invalidated
1425  * and subsequently re faulted). However it does guarantee that the page
1426  * won't be freed completely. And mostly callers simply care that the page
1427  * contains data that was valid *at some point in time*. Typically, an IO
1428  * or similar operation cannot guarantee anything stronger anyway because
1429  * locks can't be held over the syscall boundary.
1430  *
1431  * If write=0, the page must not be written to. If the page is written to,
1432  * set_page_dirty (or set_page_dirty_lock, as appropriate) must be called
1433  * after the page is finished with, and before put_page is called.
1434  *
1435  * get_user_pages is typically used for fewer-copy IO operations, to get a
1436  * handle on the memory by some means other than accesses via the user virtual
1437  * addresses. The pages may be submitted for DMA to devices or accessed via
1438  * their kernel linear mapping (via the kmap APIs). Care should be taken to
1439  * use the correct cache flushing APIs.
1440  *
1441  * See also get_user_pages_fast, for performance critical applications.
1442  */
1443 int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
1444 		unsigned long start, int nr_pages, int write, int force,
1445 		struct page **pages, struct vm_area_struct **vmas)
1446 {
1447 	int flags = FOLL_TOUCH;
1448 
1449 	if (pages)
1450 		flags |= FOLL_GET;
1451 	if (write)
1452 		flags |= FOLL_WRITE;
1453 	if (force)
1454 		flags |= FOLL_FORCE;
1455 
1456 	return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas);
1457 }
1458 EXPORT_SYMBOL(get_user_pages);
1459 
1460 /**
1461  * get_dump_page() - pin user page in memory while writing it to core dump
1462  * @addr: user address
1463  *
1464  * Returns struct page pointer of user page pinned for dump,
1465  * to be freed afterwards by page_cache_release() or put_page().
1466  *
1467  * Returns NULL on any kind of failure - a hole must then be inserted into
1468  * the corefile, to preserve alignment with its headers; and also returns
1469  * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
1470  * allowing a hole to be left in the corefile to save diskspace.
1471  *
1472  * Called without mmap_sem, but after all other threads have been killed.
1473  */
1474 #ifdef CONFIG_ELF_CORE
1475 struct page *get_dump_page(unsigned long addr)
1476 {
1477 	struct vm_area_struct *vma;
1478 	struct page *page;
1479 
1480 	if (__get_user_pages(current, current->mm, addr, 1,
1481 			FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma) < 1)
1482 		return NULL;
1483 	flush_cache_page(vma, addr, page_to_pfn(page));
1484 	return page;
1485 }
1486 #endif /* CONFIG_ELF_CORE */
1487 
1488 pte_t *get_locked_pte(struct mm_struct *mm, unsigned long addr,
1489 			spinlock_t **ptl)
1490 {
1491 	pgd_t * pgd = pgd_offset(mm, addr);
1492 	pud_t * pud = pud_alloc(mm, pgd, addr);
1493 	if (pud) {
1494 		pmd_t * pmd = pmd_alloc(mm, pud, addr);
1495 		if (pmd)
1496 			return pte_alloc_map_lock(mm, pmd, addr, ptl);
1497 	}
1498 	return NULL;
1499 }
1500 
1501 /*
1502  * This is the old fallback for page remapping.
1503  *
1504  * For historical reasons, it only allows reserved pages. Only
1505  * old drivers should use this, and they needed to mark their
1506  * pages reserved for the old functions anyway.
1507  */
1508 static int insert_page(struct vm_area_struct *vma, unsigned long addr,
1509 			struct page *page, pgprot_t prot)
1510 {
1511 	struct mm_struct *mm = vma->vm_mm;
1512 	int retval;
1513 	pte_t *pte;
1514 	spinlock_t *ptl;
1515 
1516 	retval = -EINVAL;
1517 	if (PageAnon(page))
1518 		goto out;
1519 	retval = -ENOMEM;
1520 	flush_dcache_page(page);
1521 	pte = get_locked_pte(mm, addr, &ptl);
1522 	if (!pte)
1523 		goto out;
1524 	retval = -EBUSY;
1525 	if (!pte_none(*pte))
1526 		goto out_unlock;
1527 
1528 	/* Ok, finally just insert the thing.. */
1529 	get_page(page);
1530 	inc_mm_counter(mm, file_rss);
1531 	page_add_file_rmap(page);
1532 	set_pte_at(mm, addr, pte, mk_pte(page, prot));
1533 
1534 	retval = 0;
1535 	pte_unmap_unlock(pte, ptl);
1536 	return retval;
1537 out_unlock:
1538 	pte_unmap_unlock(pte, ptl);
1539 out:
1540 	return retval;
1541 }
1542 
1543 /**
1544  * vm_insert_page - insert single page into user vma
1545  * @vma: user vma to map to
1546  * @addr: target user address of this page
1547  * @page: source kernel page
1548  *
1549  * This allows drivers to insert individual pages they've allocated
1550  * into a user vma.
1551  *
1552  * The page has to be a nice clean _individual_ kernel allocation.
1553  * If you allocate a compound page, you need to have marked it as
1554  * such (__GFP_COMP), or manually just split the page up yourself
1555  * (see split_page()).
1556  *
1557  * NOTE! Traditionally this was done with "remap_pfn_range()" which
1558  * took an arbitrary page protection parameter. This doesn't allow
1559  * that. Your vma protection will have to be set up correctly, which
1560  * means that if you want a shared writable mapping, you'd better
1561  * ask for a shared writable mapping!
1562  *
1563  * The page does not need to be reserved.
1564  */
1565 int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
1566 			struct page *page)
1567 {
1568 	if (addr < vma->vm_start || addr >= vma->vm_end)
1569 		return -EFAULT;
1570 	if (!page_count(page))
1571 		return -EINVAL;
1572 	vma->vm_flags |= VM_INSERTPAGE;
1573 	return insert_page(vma, addr, page, vma->vm_page_prot);
1574 }
1575 EXPORT_SYMBOL(vm_insert_page);
1576 
1577 static int insert_pfn(struct vm_area_struct *vma, unsigned long addr,
1578 			unsigned long pfn, pgprot_t prot)
1579 {
1580 	struct mm_struct *mm = vma->vm_mm;
1581 	int retval;
1582 	pte_t *pte, entry;
1583 	spinlock_t *ptl;
1584 
1585 	retval = -ENOMEM;
1586 	pte = get_locked_pte(mm, addr, &ptl);
1587 	if (!pte)
1588 		goto out;
1589 	retval = -EBUSY;
1590 	if (!pte_none(*pte))
1591 		goto out_unlock;
1592 
1593 	/* Ok, finally just insert the thing.. */
1594 	entry = pte_mkspecial(pfn_pte(pfn, prot));
1595 	set_pte_at(mm, addr, pte, entry);
1596 	update_mmu_cache(vma, addr, entry); /* XXX: why not for insert_page? */
1597 
1598 	retval = 0;
1599 out_unlock:
1600 	pte_unmap_unlock(pte, ptl);
1601 out:
1602 	return retval;
1603 }
1604 
1605 /**
1606  * vm_insert_pfn - insert single pfn into user vma
1607  * @vma: user vma to map to
1608  * @addr: target user address of this page
1609  * @pfn: source kernel pfn
1610  *
1611  * Similar to vm_inert_page, this allows drivers to insert individual pages
1612  * they've allocated into a user vma. Same comments apply.
1613  *
1614  * This function should only be called from a vm_ops->fault handler, and
1615  * in that case the handler should return NULL.
1616  *
1617  * vma cannot be a COW mapping.
1618  *
1619  * As this is called only for pages that do not currently exist, we
1620  * do not need to flush old virtual caches or the TLB.
1621  */
1622 int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
1623 			unsigned long pfn)
1624 {
1625 	int ret;
1626 	pgprot_t pgprot = vma->vm_page_prot;
1627 	/*
1628 	 * Technically, architectures with pte_special can avoid all these
1629 	 * restrictions (same for remap_pfn_range).  However we would like
1630 	 * consistency in testing and feature parity among all, so we should
1631 	 * try to keep these invariants in place for everybody.
1632 	 */
1633 	BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
1634 	BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
1635 						(VM_PFNMAP|VM_MIXEDMAP));
1636 	BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
1637 	BUG_ON((vma->vm_flags & VM_MIXEDMAP) && pfn_valid(pfn));
1638 
1639 	if (addr < vma->vm_start || addr >= vma->vm_end)
1640 		return -EFAULT;
1641 	if (track_pfn_vma_new(vma, &pgprot, pfn, PAGE_SIZE))
1642 		return -EINVAL;
1643 
1644 	ret = insert_pfn(vma, addr, pfn, pgprot);
1645 
1646 	if (ret)
1647 		untrack_pfn_vma(vma, pfn, PAGE_SIZE);
1648 
1649 	return ret;
1650 }
1651 EXPORT_SYMBOL(vm_insert_pfn);
1652 
1653 int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
1654 			unsigned long pfn)
1655 {
1656 	BUG_ON(!(vma->vm_flags & VM_MIXEDMAP));
1657 
1658 	if (addr < vma->vm_start || addr >= vma->vm_end)
1659 		return -EFAULT;
1660 
1661 	/*
1662 	 * If we don't have pte special, then we have to use the pfn_valid()
1663 	 * based VM_MIXEDMAP scheme (see vm_normal_page), and thus we *must*
1664 	 * refcount the page if pfn_valid is true (hence insert_page rather
1665 	 * than insert_pfn).  If a zero_pfn were inserted into a VM_MIXEDMAP
1666 	 * without pte special, it would there be refcounted as a normal page.
1667 	 */
1668 	if (!HAVE_PTE_SPECIAL && pfn_valid(pfn)) {
1669 		struct page *page;
1670 
1671 		page = pfn_to_page(pfn);
1672 		return insert_page(vma, addr, page, vma->vm_page_prot);
1673 	}
1674 	return insert_pfn(vma, addr, pfn, vma->vm_page_prot);
1675 }
1676 EXPORT_SYMBOL(vm_insert_mixed);
1677 
1678 /*
1679  * maps a range of physical memory into the requested pages. the old
1680  * mappings are removed. any references to nonexistent pages results
1681  * in null mappings (currently treated as "copy-on-access")
1682  */
1683 static int remap_pte_range(struct mm_struct *mm, pmd_t *pmd,
1684 			unsigned long addr, unsigned long end,
1685 			unsigned long pfn, pgprot_t prot)
1686 {
1687 	pte_t *pte;
1688 	spinlock_t *ptl;
1689 
1690 	pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
1691 	if (!pte)
1692 		return -ENOMEM;
1693 	arch_enter_lazy_mmu_mode();
1694 	do {
1695 		BUG_ON(!pte_none(*pte));
1696 		set_pte_at(mm, addr, pte, pte_mkspecial(pfn_pte(pfn, prot)));
1697 		pfn++;
1698 	} while (pte++, addr += PAGE_SIZE, addr != end);
1699 	arch_leave_lazy_mmu_mode();
1700 	pte_unmap_unlock(pte - 1, ptl);
1701 	return 0;
1702 }
1703 
1704 static inline int remap_pmd_range(struct mm_struct *mm, pud_t *pud,
1705 			unsigned long addr, unsigned long end,
1706 			unsigned long pfn, pgprot_t prot)
1707 {
1708 	pmd_t *pmd;
1709 	unsigned long next;
1710 
1711 	pfn -= addr >> PAGE_SHIFT;
1712 	pmd = pmd_alloc(mm, pud, addr);
1713 	if (!pmd)
1714 		return -ENOMEM;
1715 	do {
1716 		next = pmd_addr_end(addr, end);
1717 		if (remap_pte_range(mm, pmd, addr, next,
1718 				pfn + (addr >> PAGE_SHIFT), prot))
1719 			return -ENOMEM;
1720 	} while (pmd++, addr = next, addr != end);
1721 	return 0;
1722 }
1723 
1724 static inline int remap_pud_range(struct mm_struct *mm, pgd_t *pgd,
1725 			unsigned long addr, unsigned long end,
1726 			unsigned long pfn, pgprot_t prot)
1727 {
1728 	pud_t *pud;
1729 	unsigned long next;
1730 
1731 	pfn -= addr >> PAGE_SHIFT;
1732 	pud = pud_alloc(mm, pgd, addr);
1733 	if (!pud)
1734 		return -ENOMEM;
1735 	do {
1736 		next = pud_addr_end(addr, end);
1737 		if (remap_pmd_range(mm, pud, addr, next,
1738 				pfn + (addr >> PAGE_SHIFT), prot))
1739 			return -ENOMEM;
1740 	} while (pud++, addr = next, addr != end);
1741 	return 0;
1742 }
1743 
1744 /**
1745  * remap_pfn_range - remap kernel memory to userspace
1746  * @vma: user vma to map to
1747  * @addr: target user address to start at
1748  * @pfn: physical address of kernel memory
1749  * @size: size of map area
1750  * @prot: page protection flags for this mapping
1751  *
1752  *  Note: this is only safe if the mm semaphore is held when called.
1753  */
1754 int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
1755 		    unsigned long pfn, unsigned long size, pgprot_t prot)
1756 {
1757 	pgd_t *pgd;
1758 	unsigned long next;
1759 	unsigned long end = addr + PAGE_ALIGN(size);
1760 	struct mm_struct *mm = vma->vm_mm;
1761 	int err;
1762 
1763 	/*
1764 	 * Physically remapped pages are special. Tell the
1765 	 * rest of the world about it:
1766 	 *   VM_IO tells people not to look at these pages
1767 	 *	(accesses can have side effects).
1768 	 *   VM_RESERVED is specified all over the place, because
1769 	 *	in 2.4 it kept swapout's vma scan off this vma; but
1770 	 *	in 2.6 the LRU scan won't even find its pages, so this
1771 	 *	flag means no more than count its pages in reserved_vm,
1772 	 * 	and omit it from core dump, even when VM_IO turned off.
1773 	 *   VM_PFNMAP tells the core MM that the base pages are just
1774 	 *	raw PFN mappings, and do not have a "struct page" associated
1775 	 *	with them.
1776 	 *
1777 	 * There's a horrible special case to handle copy-on-write
1778 	 * behaviour that some programs depend on. We mark the "original"
1779 	 * un-COW'ed pages by matching them up with "vma->vm_pgoff".
1780 	 */
1781 	if (addr == vma->vm_start && end == vma->vm_end) {
1782 		vma->vm_pgoff = pfn;
1783 		vma->vm_flags |= VM_PFN_AT_MMAP;
1784 	} else if (is_cow_mapping(vma->vm_flags))
1785 		return -EINVAL;
1786 
1787 	vma->vm_flags |= VM_IO | VM_RESERVED | VM_PFNMAP;
1788 
1789 	err = track_pfn_vma_new(vma, &prot, pfn, PAGE_ALIGN(size));
1790 	if (err) {
1791 		/*
1792 		 * To indicate that track_pfn related cleanup is not
1793 		 * needed from higher level routine calling unmap_vmas
1794 		 */
1795 		vma->vm_flags &= ~(VM_IO | VM_RESERVED | VM_PFNMAP);
1796 		vma->vm_flags &= ~VM_PFN_AT_MMAP;
1797 		return -EINVAL;
1798 	}
1799 
1800 	BUG_ON(addr >= end);
1801 	pfn -= addr >> PAGE_SHIFT;
1802 	pgd = pgd_offset(mm, addr);
1803 	flush_cache_range(vma, addr, end);
1804 	do {
1805 		next = pgd_addr_end(addr, end);
1806 		err = remap_pud_range(mm, pgd, addr, next,
1807 				pfn + (addr >> PAGE_SHIFT), prot);
1808 		if (err)
1809 			break;
1810 	} while (pgd++, addr = next, addr != end);
1811 
1812 	if (err)
1813 		untrack_pfn_vma(vma, pfn, PAGE_ALIGN(size));
1814 
1815 	return err;
1816 }
1817 EXPORT_SYMBOL(remap_pfn_range);
1818 
1819 static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
1820 				     unsigned long addr, unsigned long end,
1821 				     pte_fn_t fn, void *data)
1822 {
1823 	pte_t *pte;
1824 	int err;
1825 	pgtable_t token;
1826 	spinlock_t *uninitialized_var(ptl);
1827 
1828 	pte = (mm == &init_mm) ?
1829 		pte_alloc_kernel(pmd, addr) :
1830 		pte_alloc_map_lock(mm, pmd, addr, &ptl);
1831 	if (!pte)
1832 		return -ENOMEM;
1833 
1834 	BUG_ON(pmd_huge(*pmd));
1835 
1836 	arch_enter_lazy_mmu_mode();
1837 
1838 	token = pmd_pgtable(*pmd);
1839 
1840 	do {
1841 		err = fn(pte++, token, addr, data);
1842 		if (err)
1843 			break;
1844 	} while (addr += PAGE_SIZE, addr != end);
1845 
1846 	arch_leave_lazy_mmu_mode();
1847 
1848 	if (mm != &init_mm)
1849 		pte_unmap_unlock(pte-1, ptl);
1850 	return err;
1851 }
1852 
1853 static int apply_to_pmd_range(struct mm_struct *mm, pud_t *pud,
1854 				     unsigned long addr, unsigned long end,
1855 				     pte_fn_t fn, void *data)
1856 {
1857 	pmd_t *pmd;
1858 	unsigned long next;
1859 	int err;
1860 
1861 	BUG_ON(pud_huge(*pud));
1862 
1863 	pmd = pmd_alloc(mm, pud, addr);
1864 	if (!pmd)
1865 		return -ENOMEM;
1866 	do {
1867 		next = pmd_addr_end(addr, end);
1868 		err = apply_to_pte_range(mm, pmd, addr, next, fn, data);
1869 		if (err)
1870 			break;
1871 	} while (pmd++, addr = next, addr != end);
1872 	return err;
1873 }
1874 
1875 static int apply_to_pud_range(struct mm_struct *mm, pgd_t *pgd,
1876 				     unsigned long addr, unsigned long end,
1877 				     pte_fn_t fn, void *data)
1878 {
1879 	pud_t *pud;
1880 	unsigned long next;
1881 	int err;
1882 
1883 	pud = pud_alloc(mm, pgd, addr);
1884 	if (!pud)
1885 		return -ENOMEM;
1886 	do {
1887 		next = pud_addr_end(addr, end);
1888 		err = apply_to_pmd_range(mm, pud, addr, next, fn, data);
1889 		if (err)
1890 			break;
1891 	} while (pud++, addr = next, addr != end);
1892 	return err;
1893 }
1894 
1895 /*
1896  * Scan a region of virtual memory, filling in page tables as necessary
1897  * and calling a provided function on each leaf page table.
1898  */
1899 int apply_to_page_range(struct mm_struct *mm, unsigned long addr,
1900 			unsigned long size, pte_fn_t fn, void *data)
1901 {
1902 	pgd_t *pgd;
1903 	unsigned long next;
1904 	unsigned long start = addr, end = addr + size;
1905 	int err;
1906 
1907 	BUG_ON(addr >= end);
1908 	mmu_notifier_invalidate_range_start(mm, start, end);
1909 	pgd = pgd_offset(mm, addr);
1910 	do {
1911 		next = pgd_addr_end(addr, end);
1912 		err = apply_to_pud_range(mm, pgd, addr, next, fn, data);
1913 		if (err)
1914 			break;
1915 	} while (pgd++, addr = next, addr != end);
1916 	mmu_notifier_invalidate_range_end(mm, start, end);
1917 	return err;
1918 }
1919 EXPORT_SYMBOL_GPL(apply_to_page_range);
1920 
1921 /*
1922  * handle_pte_fault chooses page fault handler according to an entry
1923  * which was read non-atomically.  Before making any commitment, on
1924  * those architectures or configurations (e.g. i386 with PAE) which
1925  * might give a mix of unmatched parts, do_swap_page and do_file_page
1926  * must check under lock before unmapping the pte and proceeding
1927  * (but do_wp_page is only called after already making such a check;
1928  * and do_anonymous_page and do_no_page can safely check later on).
1929  */
1930 static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd,
1931 				pte_t *page_table, pte_t orig_pte)
1932 {
1933 	int same = 1;
1934 #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
1935 	if (sizeof(pte_t) > sizeof(unsigned long)) {
1936 		spinlock_t *ptl = pte_lockptr(mm, pmd);
1937 		spin_lock(ptl);
1938 		same = pte_same(*page_table, orig_pte);
1939 		spin_unlock(ptl);
1940 	}
1941 #endif
1942 	pte_unmap(page_table);
1943 	return same;
1944 }
1945 
1946 /*
1947  * Do pte_mkwrite, but only if the vma says VM_WRITE.  We do this when
1948  * servicing faults for write access.  In the normal case, do always want
1949  * pte_mkwrite.  But get_user_pages can cause write faults for mappings
1950  * that do not have writing enabled, when used by access_process_vm.
1951  */
1952 static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
1953 {
1954 	if (likely(vma->vm_flags & VM_WRITE))
1955 		pte = pte_mkwrite(pte);
1956 	return pte;
1957 }
1958 
1959 static inline void cow_user_page(struct page *dst, struct page *src, unsigned long va, struct vm_area_struct *vma)
1960 {
1961 	/*
1962 	 * If the source page was a PFN mapping, we don't have
1963 	 * a "struct page" for it. We do a best-effort copy by
1964 	 * just copying from the original user address. If that
1965 	 * fails, we just zero-fill it. Live with it.
1966 	 */
1967 	if (unlikely(!src)) {
1968 		void *kaddr = kmap_atomic(dst, KM_USER0);
1969 		void __user *uaddr = (void __user *)(va & PAGE_MASK);
1970 
1971 		/*
1972 		 * This really shouldn't fail, because the page is there
1973 		 * in the page tables. But it might just be unreadable,
1974 		 * in which case we just give up and fill the result with
1975 		 * zeroes.
1976 		 */
1977 		if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE))
1978 			memset(kaddr, 0, PAGE_SIZE);
1979 		kunmap_atomic(kaddr, KM_USER0);
1980 		flush_dcache_page(dst);
1981 	} else
1982 		copy_user_highpage(dst, src, va, vma);
1983 }
1984 
1985 /*
1986  * This routine handles present pages, when users try to write
1987  * to a shared page. It is done by copying the page to a new address
1988  * and decrementing the shared-page counter for the old page.
1989  *
1990  * Note that this routine assumes that the protection checks have been
1991  * done by the caller (the low-level page fault routine in most cases).
1992  * Thus we can safely just mark it writable once we've done any necessary
1993  * COW.
1994  *
1995  * We also mark the page dirty at this point even though the page will
1996  * change only once the write actually happens. This avoids a few races,
1997  * and potentially makes it more efficient.
1998  *
1999  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2000  * but allow concurrent faults), with pte both mapped and locked.
2001  * We return with mmap_sem still held, but pte unmapped and unlocked.
2002  */
2003 static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
2004 		unsigned long address, pte_t *page_table, pmd_t *pmd,
2005 		spinlock_t *ptl, pte_t orig_pte)
2006 {
2007 	struct page *old_page, *new_page;
2008 	pte_t entry;
2009 	int reuse = 0, ret = 0;
2010 	int page_mkwrite = 0;
2011 	struct page *dirty_page = NULL;
2012 
2013 	old_page = vm_normal_page(vma, address, orig_pte);
2014 	if (!old_page) {
2015 		/*
2016 		 * VM_MIXEDMAP !pfn_valid() case
2017 		 *
2018 		 * We should not cow pages in a shared writeable mapping.
2019 		 * Just mark the pages writable as we can't do any dirty
2020 		 * accounting on raw pfn maps.
2021 		 */
2022 		if ((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
2023 				     (VM_WRITE|VM_SHARED))
2024 			goto reuse;
2025 		goto gotten;
2026 	}
2027 
2028 	/*
2029 	 * Take out anonymous pages first, anonymous shared vmas are
2030 	 * not dirty accountable.
2031 	 */
2032 	if (PageAnon(old_page) && !PageKsm(old_page)) {
2033 		if (!trylock_page(old_page)) {
2034 			page_cache_get(old_page);
2035 			pte_unmap_unlock(page_table, ptl);
2036 			lock_page(old_page);
2037 			page_table = pte_offset_map_lock(mm, pmd, address,
2038 							 &ptl);
2039 			if (!pte_same(*page_table, orig_pte)) {
2040 				unlock_page(old_page);
2041 				page_cache_release(old_page);
2042 				goto unlock;
2043 			}
2044 			page_cache_release(old_page);
2045 		}
2046 		reuse = reuse_swap_page(old_page);
2047 		unlock_page(old_page);
2048 	} else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
2049 					(VM_WRITE|VM_SHARED))) {
2050 		/*
2051 		 * Only catch write-faults on shared writable pages,
2052 		 * read-only shared pages can get COWed by
2053 		 * get_user_pages(.write=1, .force=1).
2054 		 */
2055 		if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
2056 			struct vm_fault vmf;
2057 			int tmp;
2058 
2059 			vmf.virtual_address = (void __user *)(address &
2060 								PAGE_MASK);
2061 			vmf.pgoff = old_page->index;
2062 			vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
2063 			vmf.page = old_page;
2064 
2065 			/*
2066 			 * Notify the address space that the page is about to
2067 			 * become writable so that it can prohibit this or wait
2068 			 * for the page to get into an appropriate state.
2069 			 *
2070 			 * We do this without the lock held, so that it can
2071 			 * sleep if it needs to.
2072 			 */
2073 			page_cache_get(old_page);
2074 			pte_unmap_unlock(page_table, ptl);
2075 
2076 			tmp = vma->vm_ops->page_mkwrite(vma, &vmf);
2077 			if (unlikely(tmp &
2078 					(VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
2079 				ret = tmp;
2080 				goto unwritable_page;
2081 			}
2082 			if (unlikely(!(tmp & VM_FAULT_LOCKED))) {
2083 				lock_page(old_page);
2084 				if (!old_page->mapping) {
2085 					ret = 0; /* retry the fault */
2086 					unlock_page(old_page);
2087 					goto unwritable_page;
2088 				}
2089 			} else
2090 				VM_BUG_ON(!PageLocked(old_page));
2091 
2092 			/*
2093 			 * Since we dropped the lock we need to revalidate
2094 			 * the PTE as someone else may have changed it.  If
2095 			 * they did, we just return, as we can count on the
2096 			 * MMU to tell us if they didn't also make it writable.
2097 			 */
2098 			page_table = pte_offset_map_lock(mm, pmd, address,
2099 							 &ptl);
2100 			if (!pte_same(*page_table, orig_pte)) {
2101 				unlock_page(old_page);
2102 				page_cache_release(old_page);
2103 				goto unlock;
2104 			}
2105 
2106 			page_mkwrite = 1;
2107 		}
2108 		dirty_page = old_page;
2109 		get_page(dirty_page);
2110 		reuse = 1;
2111 	}
2112 
2113 	if (reuse) {
2114 reuse:
2115 		flush_cache_page(vma, address, pte_pfn(orig_pte));
2116 		entry = pte_mkyoung(orig_pte);
2117 		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2118 		if (ptep_set_access_flags(vma, address, page_table, entry,1))
2119 			update_mmu_cache(vma, address, entry);
2120 		ret |= VM_FAULT_WRITE;
2121 		goto unlock;
2122 	}
2123 
2124 	/*
2125 	 * Ok, we need to copy. Oh, well..
2126 	 */
2127 	page_cache_get(old_page);
2128 gotten:
2129 	pte_unmap_unlock(page_table, ptl);
2130 
2131 	if (unlikely(anon_vma_prepare(vma)))
2132 		goto oom;
2133 
2134 	if (is_zero_pfn(pte_pfn(orig_pte))) {
2135 		new_page = alloc_zeroed_user_highpage_movable(vma, address);
2136 		if (!new_page)
2137 			goto oom;
2138 	} else {
2139 		new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
2140 		if (!new_page)
2141 			goto oom;
2142 		cow_user_page(new_page, old_page, address, vma);
2143 	}
2144 	__SetPageUptodate(new_page);
2145 
2146 	/*
2147 	 * Don't let another task, with possibly unlocked vma,
2148 	 * keep the mlocked page.
2149 	 */
2150 	if ((vma->vm_flags & VM_LOCKED) && old_page) {
2151 		lock_page(old_page);	/* for LRU manipulation */
2152 		clear_page_mlock(old_page);
2153 		unlock_page(old_page);
2154 	}
2155 
2156 	if (mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))
2157 		goto oom_free_new;
2158 
2159 	/*
2160 	 * Re-check the pte - we dropped the lock
2161 	 */
2162 	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2163 	if (likely(pte_same(*page_table, orig_pte))) {
2164 		if (old_page) {
2165 			if (!PageAnon(old_page)) {
2166 				dec_mm_counter(mm, file_rss);
2167 				inc_mm_counter(mm, anon_rss);
2168 			}
2169 		} else
2170 			inc_mm_counter(mm, anon_rss);
2171 		flush_cache_page(vma, address, pte_pfn(orig_pte));
2172 		entry = mk_pte(new_page, vma->vm_page_prot);
2173 		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2174 		/*
2175 		 * Clear the pte entry and flush it first, before updating the
2176 		 * pte with the new entry. This will avoid a race condition
2177 		 * seen in the presence of one thread doing SMC and another
2178 		 * thread doing COW.
2179 		 */
2180 		ptep_clear_flush(vma, address, page_table);
2181 		page_add_new_anon_rmap(new_page, vma, address);
2182 		/*
2183 		 * We call the notify macro here because, when using secondary
2184 		 * mmu page tables (such as kvm shadow page tables), we want the
2185 		 * new page to be mapped directly into the secondary page table.
2186 		 */
2187 		set_pte_at_notify(mm, address, page_table, entry);
2188 		update_mmu_cache(vma, address, entry);
2189 		if (old_page) {
2190 			/*
2191 			 * Only after switching the pte to the new page may
2192 			 * we remove the mapcount here. Otherwise another
2193 			 * process may come and find the rmap count decremented
2194 			 * before the pte is switched to the new page, and
2195 			 * "reuse" the old page writing into it while our pte
2196 			 * here still points into it and can be read by other
2197 			 * threads.
2198 			 *
2199 			 * The critical issue is to order this
2200 			 * page_remove_rmap with the ptp_clear_flush above.
2201 			 * Those stores are ordered by (if nothing else,)
2202 			 * the barrier present in the atomic_add_negative
2203 			 * in page_remove_rmap.
2204 			 *
2205 			 * Then the TLB flush in ptep_clear_flush ensures that
2206 			 * no process can access the old page before the
2207 			 * decremented mapcount is visible. And the old page
2208 			 * cannot be reused until after the decremented
2209 			 * mapcount is visible. So transitively, TLBs to
2210 			 * old page will be flushed before it can be reused.
2211 			 */
2212 			page_remove_rmap(old_page);
2213 		}
2214 
2215 		/* Free the old page.. */
2216 		new_page = old_page;
2217 		ret |= VM_FAULT_WRITE;
2218 	} else
2219 		mem_cgroup_uncharge_page(new_page);
2220 
2221 	if (new_page)
2222 		page_cache_release(new_page);
2223 	if (old_page)
2224 		page_cache_release(old_page);
2225 unlock:
2226 	pte_unmap_unlock(page_table, ptl);
2227 	if (dirty_page) {
2228 		/*
2229 		 * Yes, Virginia, this is actually required to prevent a race
2230 		 * with clear_page_dirty_for_io() from clearing the page dirty
2231 		 * bit after it clear all dirty ptes, but before a racing
2232 		 * do_wp_page installs a dirty pte.
2233 		 *
2234 		 * do_no_page is protected similarly.
2235 		 */
2236 		if (!page_mkwrite) {
2237 			wait_on_page_locked(dirty_page);
2238 			set_page_dirty_balance(dirty_page, page_mkwrite);
2239 		}
2240 		put_page(dirty_page);
2241 		if (page_mkwrite) {
2242 			struct address_space *mapping = dirty_page->mapping;
2243 
2244 			set_page_dirty(dirty_page);
2245 			unlock_page(dirty_page);
2246 			page_cache_release(dirty_page);
2247 			if (mapping)	{
2248 				/*
2249 				 * Some device drivers do not set page.mapping
2250 				 * but still dirty their pages
2251 				 */
2252 				balance_dirty_pages_ratelimited(mapping);
2253 			}
2254 		}
2255 
2256 		/* file_update_time outside page_lock */
2257 		if (vma->vm_file)
2258 			file_update_time(vma->vm_file);
2259 	}
2260 	return ret;
2261 oom_free_new:
2262 	page_cache_release(new_page);
2263 oom:
2264 	if (old_page) {
2265 		if (page_mkwrite) {
2266 			unlock_page(old_page);
2267 			page_cache_release(old_page);
2268 		}
2269 		page_cache_release(old_page);
2270 	}
2271 	return VM_FAULT_OOM;
2272 
2273 unwritable_page:
2274 	page_cache_release(old_page);
2275 	return ret;
2276 }
2277 
2278 /*
2279  * Helper functions for unmap_mapping_range().
2280  *
2281  * __ Notes on dropping i_mmap_lock to reduce latency while unmapping __
2282  *
2283  * We have to restart searching the prio_tree whenever we drop the lock,
2284  * since the iterator is only valid while the lock is held, and anyway
2285  * a later vma might be split and reinserted earlier while lock dropped.
2286  *
2287  * The list of nonlinear vmas could be handled more efficiently, using
2288  * a placeholder, but handle it in the same way until a need is shown.
2289  * It is important to search the prio_tree before nonlinear list: a vma
2290  * may become nonlinear and be shifted from prio_tree to nonlinear list
2291  * while the lock is dropped; but never shifted from list to prio_tree.
2292  *
2293  * In order to make forward progress despite restarting the search,
2294  * vm_truncate_count is used to mark a vma as now dealt with, so we can
2295  * quickly skip it next time around.  Since the prio_tree search only
2296  * shows us those vmas affected by unmapping the range in question, we
2297  * can't efficiently keep all vmas in step with mapping->truncate_count:
2298  * so instead reset them all whenever it wraps back to 0 (then go to 1).
2299  * mapping->truncate_count and vma->vm_truncate_count are protected by
2300  * i_mmap_lock.
2301  *
2302  * In order to make forward progress despite repeatedly restarting some
2303  * large vma, note the restart_addr from unmap_vmas when it breaks out:
2304  * and restart from that address when we reach that vma again.  It might
2305  * have been split or merged, shrunk or extended, but never shifted: so
2306  * restart_addr remains valid so long as it remains in the vma's range.
2307  * unmap_mapping_range forces truncate_count to leap over page-aligned
2308  * values so we can save vma's restart_addr in its truncate_count field.
2309  */
2310 #define is_restart_addr(truncate_count) (!((truncate_count) & ~PAGE_MASK))
2311 
2312 static void reset_vma_truncate_counts(struct address_space *mapping)
2313 {
2314 	struct vm_area_struct *vma;
2315 	struct prio_tree_iter iter;
2316 
2317 	vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, 0, ULONG_MAX)
2318 		vma->vm_truncate_count = 0;
2319 	list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list)
2320 		vma->vm_truncate_count = 0;
2321 }
2322 
2323 static int unmap_mapping_range_vma(struct vm_area_struct *vma,
2324 		unsigned long start_addr, unsigned long end_addr,
2325 		struct zap_details *details)
2326 {
2327 	unsigned long restart_addr;
2328 	int need_break;
2329 
2330 	/*
2331 	 * files that support invalidating or truncating portions of the
2332 	 * file from under mmaped areas must have their ->fault function
2333 	 * return a locked page (and set VM_FAULT_LOCKED in the return).
2334 	 * This provides synchronisation against concurrent unmapping here.
2335 	 */
2336 
2337 again:
2338 	restart_addr = vma->vm_truncate_count;
2339 	if (is_restart_addr(restart_addr) && start_addr < restart_addr) {
2340 		start_addr = restart_addr;
2341 		if (start_addr >= end_addr) {
2342 			/* Top of vma has been split off since last time */
2343 			vma->vm_truncate_count = details->truncate_count;
2344 			return 0;
2345 		}
2346 	}
2347 
2348 	restart_addr = zap_page_range(vma, start_addr,
2349 					end_addr - start_addr, details);
2350 	need_break = need_resched() || spin_needbreak(details->i_mmap_lock);
2351 
2352 	if (restart_addr >= end_addr) {
2353 		/* We have now completed this vma: mark it so */
2354 		vma->vm_truncate_count = details->truncate_count;
2355 		if (!need_break)
2356 			return 0;
2357 	} else {
2358 		/* Note restart_addr in vma's truncate_count field */
2359 		vma->vm_truncate_count = restart_addr;
2360 		if (!need_break)
2361 			goto again;
2362 	}
2363 
2364 	spin_unlock(details->i_mmap_lock);
2365 	cond_resched();
2366 	spin_lock(details->i_mmap_lock);
2367 	return -EINTR;
2368 }
2369 
2370 static inline void unmap_mapping_range_tree(struct prio_tree_root *root,
2371 					    struct zap_details *details)
2372 {
2373 	struct vm_area_struct *vma;
2374 	struct prio_tree_iter iter;
2375 	pgoff_t vba, vea, zba, zea;
2376 
2377 restart:
2378 	vma_prio_tree_foreach(vma, &iter, root,
2379 			details->first_index, details->last_index) {
2380 		/* Skip quickly over those we have already dealt with */
2381 		if (vma->vm_truncate_count == details->truncate_count)
2382 			continue;
2383 
2384 		vba = vma->vm_pgoff;
2385 		vea = vba + ((vma->vm_end - vma->vm_start) >> PAGE_SHIFT) - 1;
2386 		/* Assume for now that PAGE_CACHE_SHIFT == PAGE_SHIFT */
2387 		zba = details->first_index;
2388 		if (zba < vba)
2389 			zba = vba;
2390 		zea = details->last_index;
2391 		if (zea > vea)
2392 			zea = vea;
2393 
2394 		if (unmap_mapping_range_vma(vma,
2395 			((zba - vba) << PAGE_SHIFT) + vma->vm_start,
2396 			((zea - vba + 1) << PAGE_SHIFT) + vma->vm_start,
2397 				details) < 0)
2398 			goto restart;
2399 	}
2400 }
2401 
2402 static inline void unmap_mapping_range_list(struct list_head *head,
2403 					    struct zap_details *details)
2404 {
2405 	struct vm_area_struct *vma;
2406 
2407 	/*
2408 	 * In nonlinear VMAs there is no correspondence between virtual address
2409 	 * offset and file offset.  So we must perform an exhaustive search
2410 	 * across *all* the pages in each nonlinear VMA, not just the pages
2411 	 * whose virtual address lies outside the file truncation point.
2412 	 */
2413 restart:
2414 	list_for_each_entry(vma, head, shared.vm_set.list) {
2415 		/* Skip quickly over those we have already dealt with */
2416 		if (vma->vm_truncate_count == details->truncate_count)
2417 			continue;
2418 		details->nonlinear_vma = vma;
2419 		if (unmap_mapping_range_vma(vma, vma->vm_start,
2420 					vma->vm_end, details) < 0)
2421 			goto restart;
2422 	}
2423 }
2424 
2425 /**
2426  * unmap_mapping_range - unmap the portion of all mmaps in the specified address_space corresponding to the specified page range in the underlying file.
2427  * @mapping: the address space containing mmaps to be unmapped.
2428  * @holebegin: byte in first page to unmap, relative to the start of
2429  * the underlying file.  This will be rounded down to a PAGE_SIZE
2430  * boundary.  Note that this is different from truncate_pagecache(), which
2431  * must keep the partial page.  In contrast, we must get rid of
2432  * partial pages.
2433  * @holelen: size of prospective hole in bytes.  This will be rounded
2434  * up to a PAGE_SIZE boundary.  A holelen of zero truncates to the
2435  * end of the file.
2436  * @even_cows: 1 when truncating a file, unmap even private COWed pages;
2437  * but 0 when invalidating pagecache, don't throw away private data.
2438  */
2439 void unmap_mapping_range(struct address_space *mapping,
2440 		loff_t const holebegin, loff_t const holelen, int even_cows)
2441 {
2442 	struct zap_details details;
2443 	pgoff_t hba = holebegin >> PAGE_SHIFT;
2444 	pgoff_t hlen = (holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
2445 
2446 	/* Check for overflow. */
2447 	if (sizeof(holelen) > sizeof(hlen)) {
2448 		long long holeend =
2449 			(holebegin + holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
2450 		if (holeend & ~(long long)ULONG_MAX)
2451 			hlen = ULONG_MAX - hba + 1;
2452 	}
2453 
2454 	details.check_mapping = even_cows? NULL: mapping;
2455 	details.nonlinear_vma = NULL;
2456 	details.first_index = hba;
2457 	details.last_index = hba + hlen - 1;
2458 	if (details.last_index < details.first_index)
2459 		details.last_index = ULONG_MAX;
2460 	details.i_mmap_lock = &mapping->i_mmap_lock;
2461 
2462 	spin_lock(&mapping->i_mmap_lock);
2463 
2464 	/* Protect against endless unmapping loops */
2465 	mapping->truncate_count++;
2466 	if (unlikely(is_restart_addr(mapping->truncate_count))) {
2467 		if (mapping->truncate_count == 0)
2468 			reset_vma_truncate_counts(mapping);
2469 		mapping->truncate_count++;
2470 	}
2471 	details.truncate_count = mapping->truncate_count;
2472 
2473 	if (unlikely(!prio_tree_empty(&mapping->i_mmap)))
2474 		unmap_mapping_range_tree(&mapping->i_mmap, &details);
2475 	if (unlikely(!list_empty(&mapping->i_mmap_nonlinear)))
2476 		unmap_mapping_range_list(&mapping->i_mmap_nonlinear, &details);
2477 	spin_unlock(&mapping->i_mmap_lock);
2478 }
2479 EXPORT_SYMBOL(unmap_mapping_range);
2480 
2481 int vmtruncate_range(struct inode *inode, loff_t offset, loff_t end)
2482 {
2483 	struct address_space *mapping = inode->i_mapping;
2484 
2485 	/*
2486 	 * If the underlying filesystem is not going to provide
2487 	 * a way to truncate a range of blocks (punch a hole) -
2488 	 * we should return failure right now.
2489 	 */
2490 	if (!inode->i_op->truncate_range)
2491 		return -ENOSYS;
2492 
2493 	mutex_lock(&inode->i_mutex);
2494 	down_write(&inode->i_alloc_sem);
2495 	unmap_mapping_range(mapping, offset, (end - offset), 1);
2496 	truncate_inode_pages_range(mapping, offset, end);
2497 	unmap_mapping_range(mapping, offset, (end - offset), 1);
2498 	inode->i_op->truncate_range(inode, offset, end);
2499 	up_write(&inode->i_alloc_sem);
2500 	mutex_unlock(&inode->i_mutex);
2501 
2502 	return 0;
2503 }
2504 
2505 /*
2506  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2507  * but allow concurrent faults), and pte mapped but not yet locked.
2508  * We return with mmap_sem still held, but pte unmapped and unlocked.
2509  */
2510 static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
2511 		unsigned long address, pte_t *page_table, pmd_t *pmd,
2512 		unsigned int flags, pte_t orig_pte)
2513 {
2514 	spinlock_t *ptl;
2515 	struct page *page;
2516 	swp_entry_t entry;
2517 	pte_t pte;
2518 	struct mem_cgroup *ptr = NULL;
2519 	int ret = 0;
2520 
2521 	if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
2522 		goto out;
2523 
2524 	entry = pte_to_swp_entry(orig_pte);
2525 	if (unlikely(non_swap_entry(entry))) {
2526 		if (is_migration_entry(entry)) {
2527 			migration_entry_wait(mm, pmd, address);
2528 		} else if (is_hwpoison_entry(entry)) {
2529 			ret = VM_FAULT_HWPOISON;
2530 		} else {
2531 			print_bad_pte(vma, address, orig_pte, NULL);
2532 			ret = VM_FAULT_SIGBUS;
2533 		}
2534 		goto out;
2535 	}
2536 	delayacct_set_flag(DELAYACCT_PF_SWAPIN);
2537 	page = lookup_swap_cache(entry);
2538 	if (!page) {
2539 		grab_swap_token(mm); /* Contend for token _before_ read-in */
2540 		page = swapin_readahead(entry,
2541 					GFP_HIGHUSER_MOVABLE, vma, address);
2542 		if (!page) {
2543 			/*
2544 			 * Back out if somebody else faulted in this pte
2545 			 * while we released the pte lock.
2546 			 */
2547 			page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2548 			if (likely(pte_same(*page_table, orig_pte)))
2549 				ret = VM_FAULT_OOM;
2550 			delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
2551 			goto unlock;
2552 		}
2553 
2554 		/* Had to read the page from swap area: Major fault */
2555 		ret = VM_FAULT_MAJOR;
2556 		count_vm_event(PGMAJFAULT);
2557 	} else if (PageHWPoison(page)) {
2558 		/*
2559 		 * hwpoisoned dirty swapcache pages are kept for killing
2560 		 * owner processes (which may be unknown at hwpoison time)
2561 		 */
2562 		ret = VM_FAULT_HWPOISON;
2563 		delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
2564 		goto out_release;
2565 	}
2566 
2567 	lock_page(page);
2568 	delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
2569 
2570 	page = ksm_might_need_to_copy(page, vma, address);
2571 	if (!page) {
2572 		ret = VM_FAULT_OOM;
2573 		goto out;
2574 	}
2575 
2576 	if (mem_cgroup_try_charge_swapin(mm, page, GFP_KERNEL, &ptr)) {
2577 		ret = VM_FAULT_OOM;
2578 		goto out_page;
2579 	}
2580 
2581 	/*
2582 	 * Back out if somebody else already faulted in this pte.
2583 	 */
2584 	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2585 	if (unlikely(!pte_same(*page_table, orig_pte)))
2586 		goto out_nomap;
2587 
2588 	if (unlikely(!PageUptodate(page))) {
2589 		ret = VM_FAULT_SIGBUS;
2590 		goto out_nomap;
2591 	}
2592 
2593 	/*
2594 	 * The page isn't present yet, go ahead with the fault.
2595 	 *
2596 	 * Be careful about the sequence of operations here.
2597 	 * To get its accounting right, reuse_swap_page() must be called
2598 	 * while the page is counted on swap but not yet in mapcount i.e.
2599 	 * before page_add_anon_rmap() and swap_free(); try_to_free_swap()
2600 	 * must be called after the swap_free(), or it will never succeed.
2601 	 * Because delete_from_swap_page() may be called by reuse_swap_page(),
2602 	 * mem_cgroup_commit_charge_swapin() may not be able to find swp_entry
2603 	 * in page->private. In this case, a record in swap_cgroup  is silently
2604 	 * discarded at swap_free().
2605 	 */
2606 
2607 	inc_mm_counter(mm, anon_rss);
2608 	pte = mk_pte(page, vma->vm_page_prot);
2609 	if ((flags & FAULT_FLAG_WRITE) && reuse_swap_page(page)) {
2610 		pte = maybe_mkwrite(pte_mkdirty(pte), vma);
2611 		flags &= ~FAULT_FLAG_WRITE;
2612 	}
2613 	flush_icache_page(vma, page);
2614 	set_pte_at(mm, address, page_table, pte);
2615 	page_add_anon_rmap(page, vma, address);
2616 	/* It's better to call commit-charge after rmap is established */
2617 	mem_cgroup_commit_charge_swapin(page, ptr);
2618 
2619 	swap_free(entry);
2620 	if (vm_swap_full() || (vma->vm_flags & VM_LOCKED) || PageMlocked(page))
2621 		try_to_free_swap(page);
2622 	unlock_page(page);
2623 
2624 	if (flags & FAULT_FLAG_WRITE) {
2625 		ret |= do_wp_page(mm, vma, address, page_table, pmd, ptl, pte);
2626 		if (ret & VM_FAULT_ERROR)
2627 			ret &= VM_FAULT_ERROR;
2628 		goto out;
2629 	}
2630 
2631 	/* No need to invalidate - it was non-present before */
2632 	update_mmu_cache(vma, address, pte);
2633 unlock:
2634 	pte_unmap_unlock(page_table, ptl);
2635 out:
2636 	return ret;
2637 out_nomap:
2638 	mem_cgroup_cancel_charge_swapin(ptr);
2639 	pte_unmap_unlock(page_table, ptl);
2640 out_page:
2641 	unlock_page(page);
2642 out_release:
2643 	page_cache_release(page);
2644 	return ret;
2645 }
2646 
2647 /*
2648  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2649  * but allow concurrent faults), and pte mapped but not yet locked.
2650  * We return with mmap_sem still held, but pte unmapped and unlocked.
2651  */
2652 static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
2653 		unsigned long address, pte_t *page_table, pmd_t *pmd,
2654 		unsigned int flags)
2655 {
2656 	struct page *page;
2657 	spinlock_t *ptl;
2658 	pte_t entry;
2659 
2660 	if (!(flags & FAULT_FLAG_WRITE)) {
2661 		entry = pte_mkspecial(pfn_pte(my_zero_pfn(address),
2662 						vma->vm_page_prot));
2663 		ptl = pte_lockptr(mm, pmd);
2664 		spin_lock(ptl);
2665 		if (!pte_none(*page_table))
2666 			goto unlock;
2667 		goto setpte;
2668 	}
2669 
2670 	/* Allocate our own private page. */
2671 	pte_unmap(page_table);
2672 
2673 	if (unlikely(anon_vma_prepare(vma)))
2674 		goto oom;
2675 	page = alloc_zeroed_user_highpage_movable(vma, address);
2676 	if (!page)
2677 		goto oom;
2678 	__SetPageUptodate(page);
2679 
2680 	if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))
2681 		goto oom_free_page;
2682 
2683 	entry = mk_pte(page, vma->vm_page_prot);
2684 	if (vma->vm_flags & VM_WRITE)
2685 		entry = pte_mkwrite(pte_mkdirty(entry));
2686 
2687 	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2688 	if (!pte_none(*page_table))
2689 		goto release;
2690 
2691 	inc_mm_counter(mm, anon_rss);
2692 	page_add_new_anon_rmap(page, vma, address);
2693 setpte:
2694 	set_pte_at(mm, address, page_table, entry);
2695 
2696 	/* No need to invalidate - it was non-present before */
2697 	update_mmu_cache(vma, address, entry);
2698 unlock:
2699 	pte_unmap_unlock(page_table, ptl);
2700 	return 0;
2701 release:
2702 	mem_cgroup_uncharge_page(page);
2703 	page_cache_release(page);
2704 	goto unlock;
2705 oom_free_page:
2706 	page_cache_release(page);
2707 oom:
2708 	return VM_FAULT_OOM;
2709 }
2710 
2711 /*
2712  * __do_fault() tries to create a new page mapping. It aggressively
2713  * tries to share with existing pages, but makes a separate copy if
2714  * the FAULT_FLAG_WRITE is set in the flags parameter in order to avoid
2715  * the next page fault.
2716  *
2717  * As this is called only for pages that do not currently exist, we
2718  * do not need to flush old virtual caches or the TLB.
2719  *
2720  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2721  * but allow concurrent faults), and pte neither mapped nor locked.
2722  * We return with mmap_sem still held, but pte unmapped and unlocked.
2723  */
2724 static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
2725 		unsigned long address, pmd_t *pmd,
2726 		pgoff_t pgoff, unsigned int flags, pte_t orig_pte)
2727 {
2728 	pte_t *page_table;
2729 	spinlock_t *ptl;
2730 	struct page *page;
2731 	pte_t entry;
2732 	int anon = 0;
2733 	int charged = 0;
2734 	struct page *dirty_page = NULL;
2735 	struct vm_fault vmf;
2736 	int ret;
2737 	int page_mkwrite = 0;
2738 
2739 	vmf.virtual_address = (void __user *)(address & PAGE_MASK);
2740 	vmf.pgoff = pgoff;
2741 	vmf.flags = flags;
2742 	vmf.page = NULL;
2743 
2744 	ret = vma->vm_ops->fault(vma, &vmf);
2745 	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))
2746 		return ret;
2747 
2748 	if (unlikely(PageHWPoison(vmf.page))) {
2749 		if (ret & VM_FAULT_LOCKED)
2750 			unlock_page(vmf.page);
2751 		return VM_FAULT_HWPOISON;
2752 	}
2753 
2754 	/*
2755 	 * For consistency in subsequent calls, make the faulted page always
2756 	 * locked.
2757 	 */
2758 	if (unlikely(!(ret & VM_FAULT_LOCKED)))
2759 		lock_page(vmf.page);
2760 	else
2761 		VM_BUG_ON(!PageLocked(vmf.page));
2762 
2763 	/*
2764 	 * Should we do an early C-O-W break?
2765 	 */
2766 	page = vmf.page;
2767 	if (flags & FAULT_FLAG_WRITE) {
2768 		if (!(vma->vm_flags & VM_SHARED)) {
2769 			anon = 1;
2770 			if (unlikely(anon_vma_prepare(vma))) {
2771 				ret = VM_FAULT_OOM;
2772 				goto out;
2773 			}
2774 			page = alloc_page_vma(GFP_HIGHUSER_MOVABLE,
2775 						vma, address);
2776 			if (!page) {
2777 				ret = VM_FAULT_OOM;
2778 				goto out;
2779 			}
2780 			if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL)) {
2781 				ret = VM_FAULT_OOM;
2782 				page_cache_release(page);
2783 				goto out;
2784 			}
2785 			charged = 1;
2786 			/*
2787 			 * Don't let another task, with possibly unlocked vma,
2788 			 * keep the mlocked page.
2789 			 */
2790 			if (vma->vm_flags & VM_LOCKED)
2791 				clear_page_mlock(vmf.page);
2792 			copy_user_highpage(page, vmf.page, address, vma);
2793 			__SetPageUptodate(page);
2794 		} else {
2795 			/*
2796 			 * If the page will be shareable, see if the backing
2797 			 * address space wants to know that the page is about
2798 			 * to become writable
2799 			 */
2800 			if (vma->vm_ops->page_mkwrite) {
2801 				int tmp;
2802 
2803 				unlock_page(page);
2804 				vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
2805 				tmp = vma->vm_ops->page_mkwrite(vma, &vmf);
2806 				if (unlikely(tmp &
2807 					  (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
2808 					ret = tmp;
2809 					goto unwritable_page;
2810 				}
2811 				if (unlikely(!(tmp & VM_FAULT_LOCKED))) {
2812 					lock_page(page);
2813 					if (!page->mapping) {
2814 						ret = 0; /* retry the fault */
2815 						unlock_page(page);
2816 						goto unwritable_page;
2817 					}
2818 				} else
2819 					VM_BUG_ON(!PageLocked(page));
2820 				page_mkwrite = 1;
2821 			}
2822 		}
2823 
2824 	}
2825 
2826 	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2827 
2828 	/*
2829 	 * This silly early PAGE_DIRTY setting removes a race
2830 	 * due to the bad i386 page protection. But it's valid
2831 	 * for other architectures too.
2832 	 *
2833 	 * Note that if FAULT_FLAG_WRITE is set, we either now have
2834 	 * an exclusive copy of the page, or this is a shared mapping,
2835 	 * so we can make it writable and dirty to avoid having to
2836 	 * handle that later.
2837 	 */
2838 	/* Only go through if we didn't race with anybody else... */
2839 	if (likely(pte_same(*page_table, orig_pte))) {
2840 		flush_icache_page(vma, page);
2841 		entry = mk_pte(page, vma->vm_page_prot);
2842 		if (flags & FAULT_FLAG_WRITE)
2843 			entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2844 		if (anon) {
2845 			inc_mm_counter(mm, anon_rss);
2846 			page_add_new_anon_rmap(page, vma, address);
2847 		} else {
2848 			inc_mm_counter(mm, file_rss);
2849 			page_add_file_rmap(page);
2850 			if (flags & FAULT_FLAG_WRITE) {
2851 				dirty_page = page;
2852 				get_page(dirty_page);
2853 			}
2854 		}
2855 		set_pte_at(mm, address, page_table, entry);
2856 
2857 		/* no need to invalidate: a not-present page won't be cached */
2858 		update_mmu_cache(vma, address, entry);
2859 	} else {
2860 		if (charged)
2861 			mem_cgroup_uncharge_page(page);
2862 		if (anon)
2863 			page_cache_release(page);
2864 		else
2865 			anon = 1; /* no anon but release faulted_page */
2866 	}
2867 
2868 	pte_unmap_unlock(page_table, ptl);
2869 
2870 out:
2871 	if (dirty_page) {
2872 		struct address_space *mapping = page->mapping;
2873 
2874 		if (set_page_dirty(dirty_page))
2875 			page_mkwrite = 1;
2876 		unlock_page(dirty_page);
2877 		put_page(dirty_page);
2878 		if (page_mkwrite && mapping) {
2879 			/*
2880 			 * Some device drivers do not set page.mapping but still
2881 			 * dirty their pages
2882 			 */
2883 			balance_dirty_pages_ratelimited(mapping);
2884 		}
2885 
2886 		/* file_update_time outside page_lock */
2887 		if (vma->vm_file)
2888 			file_update_time(vma->vm_file);
2889 	} else {
2890 		unlock_page(vmf.page);
2891 		if (anon)
2892 			page_cache_release(vmf.page);
2893 	}
2894 
2895 	return ret;
2896 
2897 unwritable_page:
2898 	page_cache_release(page);
2899 	return ret;
2900 }
2901 
2902 static int do_linear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
2903 		unsigned long address, pte_t *page_table, pmd_t *pmd,
2904 		unsigned int flags, pte_t orig_pte)
2905 {
2906 	pgoff_t pgoff = (((address & PAGE_MASK)
2907 			- vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
2908 
2909 	pte_unmap(page_table);
2910 	return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
2911 }
2912 
2913 /*
2914  * Fault of a previously existing named mapping. Repopulate the pte
2915  * from the encoded file_pte if possible. This enables swappable
2916  * nonlinear vmas.
2917  *
2918  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2919  * but allow concurrent faults), and pte mapped but not yet locked.
2920  * We return with mmap_sem still held, but pte unmapped and unlocked.
2921  */
2922 static int do_nonlinear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
2923 		unsigned long address, pte_t *page_table, pmd_t *pmd,
2924 		unsigned int flags, pte_t orig_pte)
2925 {
2926 	pgoff_t pgoff;
2927 
2928 	flags |= FAULT_FLAG_NONLINEAR;
2929 
2930 	if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
2931 		return 0;
2932 
2933 	if (unlikely(!(vma->vm_flags & VM_NONLINEAR))) {
2934 		/*
2935 		 * Page table corrupted: show pte and kill process.
2936 		 */
2937 		print_bad_pte(vma, address, orig_pte, NULL);
2938 		return VM_FAULT_SIGBUS;
2939 	}
2940 
2941 	pgoff = pte_to_pgoff(orig_pte);
2942 	return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
2943 }
2944 
2945 /*
2946  * These routines also need to handle stuff like marking pages dirty
2947  * and/or accessed for architectures that don't do it in hardware (most
2948  * RISC architectures).  The early dirtying is also good on the i386.
2949  *
2950  * There is also a hook called "update_mmu_cache()" that architectures
2951  * with external mmu caches can use to update those (ie the Sparc or
2952  * PowerPC hashed page tables that act as extended TLBs).
2953  *
2954  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2955  * but allow concurrent faults), and pte mapped but not yet locked.
2956  * We return with mmap_sem still held, but pte unmapped and unlocked.
2957  */
2958 static inline int handle_pte_fault(struct mm_struct *mm,
2959 		struct vm_area_struct *vma, unsigned long address,
2960 		pte_t *pte, pmd_t *pmd, unsigned int flags)
2961 {
2962 	pte_t entry;
2963 	spinlock_t *ptl;
2964 
2965 	entry = *pte;
2966 	if (!pte_present(entry)) {
2967 		if (pte_none(entry)) {
2968 			if (vma->vm_ops) {
2969 				if (likely(vma->vm_ops->fault))
2970 					return do_linear_fault(mm, vma, address,
2971 						pte, pmd, flags, entry);
2972 			}
2973 			return do_anonymous_page(mm, vma, address,
2974 						 pte, pmd, flags);
2975 		}
2976 		if (pte_file(entry))
2977 			return do_nonlinear_fault(mm, vma, address,
2978 					pte, pmd, flags, entry);
2979 		return do_swap_page(mm, vma, address,
2980 					pte, pmd, flags, entry);
2981 	}
2982 
2983 	ptl = pte_lockptr(mm, pmd);
2984 	spin_lock(ptl);
2985 	if (unlikely(!pte_same(*pte, entry)))
2986 		goto unlock;
2987 	if (flags & FAULT_FLAG_WRITE) {
2988 		if (!pte_write(entry))
2989 			return do_wp_page(mm, vma, address,
2990 					pte, pmd, ptl, entry);
2991 		entry = pte_mkdirty(entry);
2992 	}
2993 	entry = pte_mkyoung(entry);
2994 	if (ptep_set_access_flags(vma, address, pte, entry, flags & FAULT_FLAG_WRITE)) {
2995 		update_mmu_cache(vma, address, entry);
2996 	} else {
2997 		/*
2998 		 * This is needed only for protection faults but the arch code
2999 		 * is not yet telling us if this is a protection fault or not.
3000 		 * This still avoids useless tlb flushes for .text page faults
3001 		 * with threads.
3002 		 */
3003 		if (flags & FAULT_FLAG_WRITE)
3004 			flush_tlb_page(vma, address);
3005 	}
3006 unlock:
3007 	pte_unmap_unlock(pte, ptl);
3008 	return 0;
3009 }
3010 
3011 /*
3012  * By the time we get here, we already hold the mm semaphore
3013  */
3014 int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3015 		unsigned long address, unsigned int flags)
3016 {
3017 	pgd_t *pgd;
3018 	pud_t *pud;
3019 	pmd_t *pmd;
3020 	pte_t *pte;
3021 
3022 	__set_current_state(TASK_RUNNING);
3023 
3024 	count_vm_event(PGFAULT);
3025 
3026 	if (unlikely(is_vm_hugetlb_page(vma)))
3027 		return hugetlb_fault(mm, vma, address, flags);
3028 
3029 	pgd = pgd_offset(mm, address);
3030 	pud = pud_alloc(mm, pgd, address);
3031 	if (!pud)
3032 		return VM_FAULT_OOM;
3033 	pmd = pmd_alloc(mm, pud, address);
3034 	if (!pmd)
3035 		return VM_FAULT_OOM;
3036 	pte = pte_alloc_map(mm, pmd, address);
3037 	if (!pte)
3038 		return VM_FAULT_OOM;
3039 
3040 	return handle_pte_fault(mm, vma, address, pte, pmd, flags);
3041 }
3042 
3043 #ifndef __PAGETABLE_PUD_FOLDED
3044 /*
3045  * Allocate page upper directory.
3046  * We've already handled the fast-path in-line.
3047  */
3048 int __pud_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address)
3049 {
3050 	pud_t *new = pud_alloc_one(mm, address);
3051 	if (!new)
3052 		return -ENOMEM;
3053 
3054 	smp_wmb(); /* See comment in __pte_alloc */
3055 
3056 	spin_lock(&mm->page_table_lock);
3057 	if (pgd_present(*pgd))		/* Another has populated it */
3058 		pud_free(mm, new);
3059 	else
3060 		pgd_populate(mm, pgd, new);
3061 	spin_unlock(&mm->page_table_lock);
3062 	return 0;
3063 }
3064 #endif /* __PAGETABLE_PUD_FOLDED */
3065 
3066 #ifndef __PAGETABLE_PMD_FOLDED
3067 /*
3068  * Allocate page middle directory.
3069  * We've already handled the fast-path in-line.
3070  */
3071 int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address)
3072 {
3073 	pmd_t *new = pmd_alloc_one(mm, address);
3074 	if (!new)
3075 		return -ENOMEM;
3076 
3077 	smp_wmb(); /* See comment in __pte_alloc */
3078 
3079 	spin_lock(&mm->page_table_lock);
3080 #ifndef __ARCH_HAS_4LEVEL_HACK
3081 	if (pud_present(*pud))		/* Another has populated it */
3082 		pmd_free(mm, new);
3083 	else
3084 		pud_populate(mm, pud, new);
3085 #else
3086 	if (pgd_present(*pud))		/* Another has populated it */
3087 		pmd_free(mm, new);
3088 	else
3089 		pgd_populate(mm, pud, new);
3090 #endif /* __ARCH_HAS_4LEVEL_HACK */
3091 	spin_unlock(&mm->page_table_lock);
3092 	return 0;
3093 }
3094 #endif /* __PAGETABLE_PMD_FOLDED */
3095 
3096 int make_pages_present(unsigned long addr, unsigned long end)
3097 {
3098 	int ret, len, write;
3099 	struct vm_area_struct * vma;
3100 
3101 	vma = find_vma(current->mm, addr);
3102 	if (!vma)
3103 		return -ENOMEM;
3104 	write = (vma->vm_flags & VM_WRITE) != 0;
3105 	BUG_ON(addr >= end);
3106 	BUG_ON(end > vma->vm_end);
3107 	len = DIV_ROUND_UP(end, PAGE_SIZE) - addr/PAGE_SIZE;
3108 	ret = get_user_pages(current, current->mm, addr,
3109 			len, write, 0, NULL, NULL);
3110 	if (ret < 0)
3111 		return ret;
3112 	return ret == len ? 0 : -EFAULT;
3113 }
3114 
3115 #if !defined(__HAVE_ARCH_GATE_AREA)
3116 
3117 #if defined(AT_SYSINFO_EHDR)
3118 static struct vm_area_struct gate_vma;
3119 
3120 static int __init gate_vma_init(void)
3121 {
3122 	gate_vma.vm_mm = NULL;
3123 	gate_vma.vm_start = FIXADDR_USER_START;
3124 	gate_vma.vm_end = FIXADDR_USER_END;
3125 	gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
3126 	gate_vma.vm_page_prot = __P101;
3127 	/*
3128 	 * Make sure the vDSO gets into every core dump.
3129 	 * Dumping its contents makes post-mortem fully interpretable later
3130 	 * without matching up the same kernel and hardware config to see
3131 	 * what PC values meant.
3132 	 */
3133 	gate_vma.vm_flags |= VM_ALWAYSDUMP;
3134 	return 0;
3135 }
3136 __initcall(gate_vma_init);
3137 #endif
3138 
3139 struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
3140 {
3141 #ifdef AT_SYSINFO_EHDR
3142 	return &gate_vma;
3143 #else
3144 	return NULL;
3145 #endif
3146 }
3147 
3148 int in_gate_area_no_task(unsigned long addr)
3149 {
3150 #ifdef AT_SYSINFO_EHDR
3151 	if ((addr >= FIXADDR_USER_START) && (addr < FIXADDR_USER_END))
3152 		return 1;
3153 #endif
3154 	return 0;
3155 }
3156 
3157 #endif	/* __HAVE_ARCH_GATE_AREA */
3158 
3159 static int follow_pte(struct mm_struct *mm, unsigned long address,
3160 		pte_t **ptepp, spinlock_t **ptlp)
3161 {
3162 	pgd_t *pgd;
3163 	pud_t *pud;
3164 	pmd_t *pmd;
3165 	pte_t *ptep;
3166 
3167 	pgd = pgd_offset(mm, address);
3168 	if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
3169 		goto out;
3170 
3171 	pud = pud_offset(pgd, address);
3172 	if (pud_none(*pud) || unlikely(pud_bad(*pud)))
3173 		goto out;
3174 
3175 	pmd = pmd_offset(pud, address);
3176 	if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
3177 		goto out;
3178 
3179 	/* We cannot handle huge page PFN maps. Luckily they don't exist. */
3180 	if (pmd_huge(*pmd))
3181 		goto out;
3182 
3183 	ptep = pte_offset_map_lock(mm, pmd, address, ptlp);
3184 	if (!ptep)
3185 		goto out;
3186 	if (!pte_present(*ptep))
3187 		goto unlock;
3188 	*ptepp = ptep;
3189 	return 0;
3190 unlock:
3191 	pte_unmap_unlock(ptep, *ptlp);
3192 out:
3193 	return -EINVAL;
3194 }
3195 
3196 /**
3197  * follow_pfn - look up PFN at a user virtual address
3198  * @vma: memory mapping
3199  * @address: user virtual address
3200  * @pfn: location to store found PFN
3201  *
3202  * Only IO mappings and raw PFN mappings are allowed.
3203  *
3204  * Returns zero and the pfn at @pfn on success, -ve otherwise.
3205  */
3206 int follow_pfn(struct vm_area_struct *vma, unsigned long address,
3207 	unsigned long *pfn)
3208 {
3209 	int ret = -EINVAL;
3210 	spinlock_t *ptl;
3211 	pte_t *ptep;
3212 
3213 	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
3214 		return ret;
3215 
3216 	ret = follow_pte(vma->vm_mm, address, &ptep, &ptl);
3217 	if (ret)
3218 		return ret;
3219 	*pfn = pte_pfn(*ptep);
3220 	pte_unmap_unlock(ptep, ptl);
3221 	return 0;
3222 }
3223 EXPORT_SYMBOL(follow_pfn);
3224 
3225 #ifdef CONFIG_HAVE_IOREMAP_PROT
3226 int follow_phys(struct vm_area_struct *vma,
3227 		unsigned long address, unsigned int flags,
3228 		unsigned long *prot, resource_size_t *phys)
3229 {
3230 	int ret = -EINVAL;
3231 	pte_t *ptep, pte;
3232 	spinlock_t *ptl;
3233 
3234 	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
3235 		goto out;
3236 
3237 	if (follow_pte(vma->vm_mm, address, &ptep, &ptl))
3238 		goto out;
3239 	pte = *ptep;
3240 
3241 	if ((flags & FOLL_WRITE) && !pte_write(pte))
3242 		goto unlock;
3243 
3244 	*prot = pgprot_val(pte_pgprot(pte));
3245 	*phys = (resource_size_t)pte_pfn(pte) << PAGE_SHIFT;
3246 
3247 	ret = 0;
3248 unlock:
3249 	pte_unmap_unlock(ptep, ptl);
3250 out:
3251 	return ret;
3252 }
3253 
3254 int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
3255 			void *buf, int len, int write)
3256 {
3257 	resource_size_t phys_addr;
3258 	unsigned long prot = 0;
3259 	void __iomem *maddr;
3260 	int offset = addr & (PAGE_SIZE-1);
3261 
3262 	if (follow_phys(vma, addr, write, &prot, &phys_addr))
3263 		return -EINVAL;
3264 
3265 	maddr = ioremap_prot(phys_addr, PAGE_SIZE, prot);
3266 	if (write)
3267 		memcpy_toio(maddr + offset, buf, len);
3268 	else
3269 		memcpy_fromio(buf, maddr + offset, len);
3270 	iounmap(maddr);
3271 
3272 	return len;
3273 }
3274 #endif
3275 
3276 /*
3277  * Access another process' address space.
3278  * Source/target buffer must be kernel space,
3279  * Do not walk the page table directly, use get_user_pages
3280  */
3281 int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
3282 {
3283 	struct mm_struct *mm;
3284 	struct vm_area_struct *vma;
3285 	void *old_buf = buf;
3286 
3287 	mm = get_task_mm(tsk);
3288 	if (!mm)
3289 		return 0;
3290 
3291 	down_read(&mm->mmap_sem);
3292 	/* ignore errors, just check how much was successfully transferred */
3293 	while (len) {
3294 		int bytes, ret, offset;
3295 		void *maddr;
3296 		struct page *page = NULL;
3297 
3298 		ret = get_user_pages(tsk, mm, addr, 1,
3299 				write, 1, &page, &vma);
3300 		if (ret <= 0) {
3301 			/*
3302 			 * Check if this is a VM_IO | VM_PFNMAP VMA, which
3303 			 * we can access using slightly different code.
3304 			 */
3305 #ifdef CONFIG_HAVE_IOREMAP_PROT
3306 			vma = find_vma(mm, addr);
3307 			if (!vma)
3308 				break;
3309 			if (vma->vm_ops && vma->vm_ops->access)
3310 				ret = vma->vm_ops->access(vma, addr, buf,
3311 							  len, write);
3312 			if (ret <= 0)
3313 #endif
3314 				break;
3315 			bytes = ret;
3316 		} else {
3317 			bytes = len;
3318 			offset = addr & (PAGE_SIZE-1);
3319 			if (bytes > PAGE_SIZE-offset)
3320 				bytes = PAGE_SIZE-offset;
3321 
3322 			maddr = kmap(page);
3323 			if (write) {
3324 				copy_to_user_page(vma, page, addr,
3325 						  maddr + offset, buf, bytes);
3326 				set_page_dirty_lock(page);
3327 			} else {
3328 				copy_from_user_page(vma, page, addr,
3329 						    buf, maddr + offset, bytes);
3330 			}
3331 			kunmap(page);
3332 			page_cache_release(page);
3333 		}
3334 		len -= bytes;
3335 		buf += bytes;
3336 		addr += bytes;
3337 	}
3338 	up_read(&mm->mmap_sem);
3339 	mmput(mm);
3340 
3341 	return buf - old_buf;
3342 }
3343 
3344 /*
3345  * Print the name of a VMA.
3346  */
3347 void print_vma_addr(char *prefix, unsigned long ip)
3348 {
3349 	struct mm_struct *mm = current->mm;
3350 	struct vm_area_struct *vma;
3351 
3352 	/*
3353 	 * Do not print if we are in atomic
3354 	 * contexts (in exception stacks, etc.):
3355 	 */
3356 	if (preempt_count())
3357 		return;
3358 
3359 	down_read(&mm->mmap_sem);
3360 	vma = find_vma(mm, ip);
3361 	if (vma && vma->vm_file) {
3362 		struct file *f = vma->vm_file;
3363 		char *buf = (char *)__get_free_page(GFP_KERNEL);
3364 		if (buf) {
3365 			char *p, *s;
3366 
3367 			p = d_path(&f->f_path, buf, PAGE_SIZE);
3368 			if (IS_ERR(p))
3369 				p = "?";
3370 			s = strrchr(p, '/');
3371 			if (s)
3372 				p = s+1;
3373 			printk("%s%s[%lx+%lx]", prefix, p,
3374 					vma->vm_start,
3375 					vma->vm_end - vma->vm_start);
3376 			free_page((unsigned long)buf);
3377 		}
3378 	}
3379 	up_read(&current->mm->mmap_sem);
3380 }
3381 
3382 #ifdef CONFIG_PROVE_LOCKING
3383 void might_fault(void)
3384 {
3385 	/*
3386 	 * Some code (nfs/sunrpc) uses socket ops on kernel memory while
3387 	 * holding the mmap_sem, this is safe because kernel memory doesn't
3388 	 * get paged out, therefore we'll never actually fault, and the
3389 	 * below annotations will generate false positives.
3390 	 */
3391 	if (segment_eq(get_fs(), KERNEL_DS))
3392 		return;
3393 
3394 	might_sleep();
3395 	/*
3396 	 * it would be nicer only to annotate paths which are not under
3397 	 * pagefault_disable, however that requires a larger audit and
3398 	 * providing helpers like get_user_atomic.
3399 	 */
3400 	if (!in_atomic() && current->mm)
3401 		might_lock_read(&current->mm->mmap_sem);
3402 }
3403 EXPORT_SYMBOL(might_fault);
3404 #endif
3405