xref: /openbmc/linux/mm/memory.c (revision 4800cd83)
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 #include <linux/gfp.h>
60 
61 #include <asm/io.h>
62 #include <asm/pgalloc.h>
63 #include <asm/uaccess.h>
64 #include <asm/tlb.h>
65 #include <asm/tlbflush.h>
66 #include <asm/pgtable.h>
67 
68 #include "internal.h"
69 
70 #ifndef CONFIG_NEED_MULTIPLE_NODES
71 /* use the per-pgdat data instead for discontigmem - mbligh */
72 unsigned long max_mapnr;
73 struct page *mem_map;
74 
75 EXPORT_SYMBOL(max_mapnr);
76 EXPORT_SYMBOL(mem_map);
77 #endif
78 
79 unsigned long num_physpages;
80 /*
81  * A number of key systems in x86 including ioremap() rely on the assumption
82  * that high_memory defines the upper bound on direct map memory, then end
83  * of ZONE_NORMAL.  Under CONFIG_DISCONTIG this means that max_low_pfn and
84  * highstart_pfn must be the same; there must be no gap between ZONE_NORMAL
85  * and ZONE_HIGHMEM.
86  */
87 void * high_memory;
88 
89 EXPORT_SYMBOL(num_physpages);
90 EXPORT_SYMBOL(high_memory);
91 
92 /*
93  * Randomize the address space (stacks, mmaps, brk, etc.).
94  *
95  * ( When CONFIG_COMPAT_BRK=y we exclude brk from randomization,
96  *   as ancient (libc5 based) binaries can segfault. )
97  */
98 int randomize_va_space __read_mostly =
99 #ifdef CONFIG_COMPAT_BRK
100 					1;
101 #else
102 					2;
103 #endif
104 
105 static int __init disable_randmaps(char *s)
106 {
107 	randomize_va_space = 0;
108 	return 1;
109 }
110 __setup("norandmaps", disable_randmaps);
111 
112 unsigned long zero_pfn __read_mostly;
113 unsigned long highest_memmap_pfn __read_mostly;
114 
115 /*
116  * CONFIG_MMU architectures set up ZERO_PAGE in their paging_init()
117  */
118 static int __init init_zero_pfn(void)
119 {
120 	zero_pfn = page_to_pfn(ZERO_PAGE(0));
121 	return 0;
122 }
123 core_initcall(init_zero_pfn);
124 
125 
126 #if defined(SPLIT_RSS_COUNTING)
127 
128 static void __sync_task_rss_stat(struct task_struct *task, struct mm_struct *mm)
129 {
130 	int i;
131 
132 	for (i = 0; i < NR_MM_COUNTERS; i++) {
133 		if (task->rss_stat.count[i]) {
134 			add_mm_counter(mm, i, task->rss_stat.count[i]);
135 			task->rss_stat.count[i] = 0;
136 		}
137 	}
138 	task->rss_stat.events = 0;
139 }
140 
141 static void add_mm_counter_fast(struct mm_struct *mm, int member, int val)
142 {
143 	struct task_struct *task = current;
144 
145 	if (likely(task->mm == mm))
146 		task->rss_stat.count[member] += val;
147 	else
148 		add_mm_counter(mm, member, val);
149 }
150 #define inc_mm_counter_fast(mm, member) add_mm_counter_fast(mm, member, 1)
151 #define dec_mm_counter_fast(mm, member) add_mm_counter_fast(mm, member, -1)
152 
153 /* sync counter once per 64 page faults */
154 #define TASK_RSS_EVENTS_THRESH	(64)
155 static void check_sync_rss_stat(struct task_struct *task)
156 {
157 	if (unlikely(task != current))
158 		return;
159 	if (unlikely(task->rss_stat.events++ > TASK_RSS_EVENTS_THRESH))
160 		__sync_task_rss_stat(task, task->mm);
161 }
162 
163 unsigned long get_mm_counter(struct mm_struct *mm, int member)
164 {
165 	long val = 0;
166 
167 	/*
168 	 * Don't use task->mm here...for avoiding to use task_get_mm()..
169 	 * The caller must guarantee task->mm is not invalid.
170 	 */
171 	val = atomic_long_read(&mm->rss_stat.count[member]);
172 	/*
173 	 * counter is updated in asynchronous manner and may go to minus.
174 	 * But it's never be expected number for users.
175 	 */
176 	if (val < 0)
177 		return 0;
178 	return (unsigned long)val;
179 }
180 
181 void sync_mm_rss(struct task_struct *task, struct mm_struct *mm)
182 {
183 	__sync_task_rss_stat(task, mm);
184 }
185 #else
186 
187 #define inc_mm_counter_fast(mm, member) inc_mm_counter(mm, member)
188 #define dec_mm_counter_fast(mm, member) dec_mm_counter(mm, member)
189 
190 static void check_sync_rss_stat(struct task_struct *task)
191 {
192 }
193 
194 #endif
195 
196 /*
197  * If a p?d_bad entry is found while walking page tables, report
198  * the error, before resetting entry to p?d_none.  Usually (but
199  * very seldom) called out from the p?d_none_or_clear_bad macros.
200  */
201 
202 void pgd_clear_bad(pgd_t *pgd)
203 {
204 	pgd_ERROR(*pgd);
205 	pgd_clear(pgd);
206 }
207 
208 void pud_clear_bad(pud_t *pud)
209 {
210 	pud_ERROR(*pud);
211 	pud_clear(pud);
212 }
213 
214 void pmd_clear_bad(pmd_t *pmd)
215 {
216 	pmd_ERROR(*pmd);
217 	pmd_clear(pmd);
218 }
219 
220 /*
221  * Note: this doesn't free the actual pages themselves. That
222  * has been handled earlier when unmapping all the memory regions.
223  */
224 static void free_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
225 			   unsigned long addr)
226 {
227 	pgtable_t token = pmd_pgtable(*pmd);
228 	pmd_clear(pmd);
229 	pte_free_tlb(tlb, token, addr);
230 	tlb->mm->nr_ptes--;
231 }
232 
233 static inline void free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
234 				unsigned long addr, unsigned long end,
235 				unsigned long floor, unsigned long ceiling)
236 {
237 	pmd_t *pmd;
238 	unsigned long next;
239 	unsigned long start;
240 
241 	start = addr;
242 	pmd = pmd_offset(pud, addr);
243 	do {
244 		next = pmd_addr_end(addr, end);
245 		if (pmd_none_or_clear_bad(pmd))
246 			continue;
247 		free_pte_range(tlb, pmd, addr);
248 	} while (pmd++, addr = next, addr != end);
249 
250 	start &= PUD_MASK;
251 	if (start < floor)
252 		return;
253 	if (ceiling) {
254 		ceiling &= PUD_MASK;
255 		if (!ceiling)
256 			return;
257 	}
258 	if (end - 1 > ceiling - 1)
259 		return;
260 
261 	pmd = pmd_offset(pud, start);
262 	pud_clear(pud);
263 	pmd_free_tlb(tlb, pmd, start);
264 }
265 
266 static inline void free_pud_range(struct mmu_gather *tlb, pgd_t *pgd,
267 				unsigned long addr, unsigned long end,
268 				unsigned long floor, unsigned long ceiling)
269 {
270 	pud_t *pud;
271 	unsigned long next;
272 	unsigned long start;
273 
274 	start = addr;
275 	pud = pud_offset(pgd, addr);
276 	do {
277 		next = pud_addr_end(addr, end);
278 		if (pud_none_or_clear_bad(pud))
279 			continue;
280 		free_pmd_range(tlb, pud, addr, next, floor, ceiling);
281 	} while (pud++, addr = next, addr != end);
282 
283 	start &= PGDIR_MASK;
284 	if (start < floor)
285 		return;
286 	if (ceiling) {
287 		ceiling &= PGDIR_MASK;
288 		if (!ceiling)
289 			return;
290 	}
291 	if (end - 1 > ceiling - 1)
292 		return;
293 
294 	pud = pud_offset(pgd, start);
295 	pgd_clear(pgd);
296 	pud_free_tlb(tlb, pud, start);
297 }
298 
299 /*
300  * This function frees user-level page tables of a process.
301  *
302  * Must be called with pagetable lock held.
303  */
304 void free_pgd_range(struct mmu_gather *tlb,
305 			unsigned long addr, unsigned long end,
306 			unsigned long floor, unsigned long ceiling)
307 {
308 	pgd_t *pgd;
309 	unsigned long next;
310 
311 	/*
312 	 * The next few lines have given us lots of grief...
313 	 *
314 	 * Why are we testing PMD* at this top level?  Because often
315 	 * there will be no work to do at all, and we'd prefer not to
316 	 * go all the way down to the bottom just to discover that.
317 	 *
318 	 * Why all these "- 1"s?  Because 0 represents both the bottom
319 	 * of the address space and the top of it (using -1 for the
320 	 * top wouldn't help much: the masks would do the wrong thing).
321 	 * The rule is that addr 0 and floor 0 refer to the bottom of
322 	 * the address space, but end 0 and ceiling 0 refer to the top
323 	 * Comparisons need to use "end - 1" and "ceiling - 1" (though
324 	 * that end 0 case should be mythical).
325 	 *
326 	 * Wherever addr is brought up or ceiling brought down, we must
327 	 * be careful to reject "the opposite 0" before it confuses the
328 	 * subsequent tests.  But what about where end is brought down
329 	 * by PMD_SIZE below? no, end can't go down to 0 there.
330 	 *
331 	 * Whereas we round start (addr) and ceiling down, by different
332 	 * masks at different levels, in order to test whether a table
333 	 * now has no other vmas using it, so can be freed, we don't
334 	 * bother to round floor or end up - the tests don't need that.
335 	 */
336 
337 	addr &= PMD_MASK;
338 	if (addr < floor) {
339 		addr += PMD_SIZE;
340 		if (!addr)
341 			return;
342 	}
343 	if (ceiling) {
344 		ceiling &= PMD_MASK;
345 		if (!ceiling)
346 			return;
347 	}
348 	if (end - 1 > ceiling - 1)
349 		end -= PMD_SIZE;
350 	if (addr > end - 1)
351 		return;
352 
353 	pgd = pgd_offset(tlb->mm, addr);
354 	do {
355 		next = pgd_addr_end(addr, end);
356 		if (pgd_none_or_clear_bad(pgd))
357 			continue;
358 		free_pud_range(tlb, pgd, addr, next, floor, ceiling);
359 	} while (pgd++, addr = next, addr != end);
360 }
361 
362 void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *vma,
363 		unsigned long floor, unsigned long ceiling)
364 {
365 	while (vma) {
366 		struct vm_area_struct *next = vma->vm_next;
367 		unsigned long addr = vma->vm_start;
368 
369 		/*
370 		 * Hide vma from rmap and truncate_pagecache before freeing
371 		 * pgtables
372 		 */
373 		unlink_anon_vmas(vma);
374 		unlink_file_vma(vma);
375 
376 		if (is_vm_hugetlb_page(vma)) {
377 			hugetlb_free_pgd_range(tlb, addr, vma->vm_end,
378 				floor, next? next->vm_start: ceiling);
379 		} else {
380 			/*
381 			 * Optimization: gather nearby vmas into one call down
382 			 */
383 			while (next && next->vm_start <= vma->vm_end + PMD_SIZE
384 			       && !is_vm_hugetlb_page(next)) {
385 				vma = next;
386 				next = vma->vm_next;
387 				unlink_anon_vmas(vma);
388 				unlink_file_vma(vma);
389 			}
390 			free_pgd_range(tlb, addr, vma->vm_end,
391 				floor, next? next->vm_start: ceiling);
392 		}
393 		vma = next;
394 	}
395 }
396 
397 int __pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma,
398 		pmd_t *pmd, unsigned long address)
399 {
400 	pgtable_t new = pte_alloc_one(mm, address);
401 	int wait_split_huge_page;
402 	if (!new)
403 		return -ENOMEM;
404 
405 	/*
406 	 * Ensure all pte setup (eg. pte page lock and page clearing) are
407 	 * visible before the pte is made visible to other CPUs by being
408 	 * put into page tables.
409 	 *
410 	 * The other side of the story is the pointer chasing in the page
411 	 * table walking code (when walking the page table without locking;
412 	 * ie. most of the time). Fortunately, these data accesses consist
413 	 * of a chain of data-dependent loads, meaning most CPUs (alpha
414 	 * being the notable exception) will already guarantee loads are
415 	 * seen in-order. See the alpha page table accessors for the
416 	 * smp_read_barrier_depends() barriers in page table walking code.
417 	 */
418 	smp_wmb(); /* Could be smp_wmb__xxx(before|after)_spin_lock */
419 
420 	spin_lock(&mm->page_table_lock);
421 	wait_split_huge_page = 0;
422 	if (likely(pmd_none(*pmd))) {	/* Has another populated it ? */
423 		mm->nr_ptes++;
424 		pmd_populate(mm, pmd, new);
425 		new = NULL;
426 	} else if (unlikely(pmd_trans_splitting(*pmd)))
427 		wait_split_huge_page = 1;
428 	spin_unlock(&mm->page_table_lock);
429 	if (new)
430 		pte_free(mm, new);
431 	if (wait_split_huge_page)
432 		wait_split_huge_page(vma->anon_vma, pmd);
433 	return 0;
434 }
435 
436 int __pte_alloc_kernel(pmd_t *pmd, unsigned long address)
437 {
438 	pte_t *new = pte_alloc_one_kernel(&init_mm, address);
439 	if (!new)
440 		return -ENOMEM;
441 
442 	smp_wmb(); /* See comment in __pte_alloc */
443 
444 	spin_lock(&init_mm.page_table_lock);
445 	if (likely(pmd_none(*pmd))) {	/* Has another populated it ? */
446 		pmd_populate_kernel(&init_mm, pmd, new);
447 		new = NULL;
448 	} else
449 		VM_BUG_ON(pmd_trans_splitting(*pmd));
450 	spin_unlock(&init_mm.page_table_lock);
451 	if (new)
452 		pte_free_kernel(&init_mm, new);
453 	return 0;
454 }
455 
456 static inline void init_rss_vec(int *rss)
457 {
458 	memset(rss, 0, sizeof(int) * NR_MM_COUNTERS);
459 }
460 
461 static inline void add_mm_rss_vec(struct mm_struct *mm, int *rss)
462 {
463 	int i;
464 
465 	if (current->mm == mm)
466 		sync_mm_rss(current, mm);
467 	for (i = 0; i < NR_MM_COUNTERS; i++)
468 		if (rss[i])
469 			add_mm_counter(mm, i, rss[i]);
470 }
471 
472 /*
473  * This function is called to print an error when a bad pte
474  * is found. For example, we might have a PFN-mapped pte in
475  * a region that doesn't allow it.
476  *
477  * The calling function must still handle the error.
478  */
479 static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
480 			  pte_t pte, struct page *page)
481 {
482 	pgd_t *pgd = pgd_offset(vma->vm_mm, addr);
483 	pud_t *pud = pud_offset(pgd, addr);
484 	pmd_t *pmd = pmd_offset(pud, addr);
485 	struct address_space *mapping;
486 	pgoff_t index;
487 	static unsigned long resume;
488 	static unsigned long nr_shown;
489 	static unsigned long nr_unshown;
490 
491 	/*
492 	 * Allow a burst of 60 reports, then keep quiet for that minute;
493 	 * or allow a steady drip of one report per second.
494 	 */
495 	if (nr_shown == 60) {
496 		if (time_before(jiffies, resume)) {
497 			nr_unshown++;
498 			return;
499 		}
500 		if (nr_unshown) {
501 			printk(KERN_ALERT
502 				"BUG: Bad page map: %lu messages suppressed\n",
503 				nr_unshown);
504 			nr_unshown = 0;
505 		}
506 		nr_shown = 0;
507 	}
508 	if (nr_shown++ == 0)
509 		resume = jiffies + 60 * HZ;
510 
511 	mapping = vma->vm_file ? vma->vm_file->f_mapping : NULL;
512 	index = linear_page_index(vma, addr);
513 
514 	printk(KERN_ALERT
515 		"BUG: Bad page map in process %s  pte:%08llx pmd:%08llx\n",
516 		current->comm,
517 		(long long)pte_val(pte), (long long)pmd_val(*pmd));
518 	if (page)
519 		dump_page(page);
520 	printk(KERN_ALERT
521 		"addr:%p vm_flags:%08lx anon_vma:%p mapping:%p index:%lx\n",
522 		(void *)addr, vma->vm_flags, vma->anon_vma, mapping, index);
523 	/*
524 	 * Choose text because data symbols depend on CONFIG_KALLSYMS_ALL=y
525 	 */
526 	if (vma->vm_ops)
527 		print_symbol(KERN_ALERT "vma->vm_ops->fault: %s\n",
528 				(unsigned long)vma->vm_ops->fault);
529 	if (vma->vm_file && vma->vm_file->f_op)
530 		print_symbol(KERN_ALERT "vma->vm_file->f_op->mmap: %s\n",
531 				(unsigned long)vma->vm_file->f_op->mmap);
532 	dump_stack();
533 	add_taint(TAINT_BAD_PAGE);
534 }
535 
536 static inline int is_cow_mapping(unsigned int flags)
537 {
538 	return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
539 }
540 
541 #ifndef is_zero_pfn
542 static inline int is_zero_pfn(unsigned long pfn)
543 {
544 	return pfn == zero_pfn;
545 }
546 #endif
547 
548 #ifndef my_zero_pfn
549 static inline unsigned long my_zero_pfn(unsigned long addr)
550 {
551 	return zero_pfn;
552 }
553 #endif
554 
555 /*
556  * vm_normal_page -- This function gets the "struct page" associated with a pte.
557  *
558  * "Special" mappings do not wish to be associated with a "struct page" (either
559  * it doesn't exist, or it exists but they don't want to touch it). In this
560  * case, NULL is returned here. "Normal" mappings do have a struct page.
561  *
562  * There are 2 broad cases. Firstly, an architecture may define a pte_special()
563  * pte bit, in which case this function is trivial. Secondly, an architecture
564  * may not have a spare pte bit, which requires a more complicated scheme,
565  * described below.
566  *
567  * A raw VM_PFNMAP mapping (ie. one that is not COWed) is always considered a
568  * special mapping (even if there are underlying and valid "struct pages").
569  * COWed pages of a VM_PFNMAP are always normal.
570  *
571  * The way we recognize COWed pages within VM_PFNMAP mappings is through the
572  * rules set up by "remap_pfn_range()": the vma will have the VM_PFNMAP bit
573  * set, and the vm_pgoff will point to the first PFN mapped: thus every special
574  * mapping will always honor the rule
575  *
576  *	pfn_of_page == vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT)
577  *
578  * And for normal mappings this is false.
579  *
580  * This restricts such mappings to be a linear translation from virtual address
581  * to pfn. To get around this restriction, we allow arbitrary mappings so long
582  * as the vma is not a COW mapping; in that case, we know that all ptes are
583  * special (because none can have been COWed).
584  *
585  *
586  * In order to support COW of arbitrary special mappings, we have VM_MIXEDMAP.
587  *
588  * VM_MIXEDMAP mappings can likewise contain memory with or without "struct
589  * page" backing, however the difference is that _all_ pages with a struct
590  * page (that is, those where pfn_valid is true) are refcounted and considered
591  * normal pages by the VM. The disadvantage is that pages are refcounted
592  * (which can be slower and simply not an option for some PFNMAP users). The
593  * advantage is that we don't have to follow the strict linearity rule of
594  * PFNMAP mappings in order to support COWable mappings.
595  *
596  */
597 #ifdef __HAVE_ARCH_PTE_SPECIAL
598 # define HAVE_PTE_SPECIAL 1
599 #else
600 # define HAVE_PTE_SPECIAL 0
601 #endif
602 struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
603 				pte_t pte)
604 {
605 	unsigned long pfn = pte_pfn(pte);
606 
607 	if (HAVE_PTE_SPECIAL) {
608 		if (likely(!pte_special(pte)))
609 			goto check_pfn;
610 		if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
611 			return NULL;
612 		if (!is_zero_pfn(pfn))
613 			print_bad_pte(vma, addr, pte, NULL);
614 		return NULL;
615 	}
616 
617 	/* !HAVE_PTE_SPECIAL case follows: */
618 
619 	if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
620 		if (vma->vm_flags & VM_MIXEDMAP) {
621 			if (!pfn_valid(pfn))
622 				return NULL;
623 			goto out;
624 		} else {
625 			unsigned long off;
626 			off = (addr - vma->vm_start) >> PAGE_SHIFT;
627 			if (pfn == vma->vm_pgoff + off)
628 				return NULL;
629 			if (!is_cow_mapping(vma->vm_flags))
630 				return NULL;
631 		}
632 	}
633 
634 	if (is_zero_pfn(pfn))
635 		return NULL;
636 check_pfn:
637 	if (unlikely(pfn > highest_memmap_pfn)) {
638 		print_bad_pte(vma, addr, pte, NULL);
639 		return NULL;
640 	}
641 
642 	/*
643 	 * NOTE! We still have PageReserved() pages in the page tables.
644 	 * eg. VDSO mappings can cause them to exist.
645 	 */
646 out:
647 	return pfn_to_page(pfn);
648 }
649 
650 /*
651  * copy one vm_area from one task to the other. Assumes the page tables
652  * already present in the new task to be cleared in the whole range
653  * covered by this vma.
654  */
655 
656 static inline unsigned long
657 copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
658 		pte_t *dst_pte, pte_t *src_pte, struct vm_area_struct *vma,
659 		unsigned long addr, int *rss)
660 {
661 	unsigned long vm_flags = vma->vm_flags;
662 	pte_t pte = *src_pte;
663 	struct page *page;
664 
665 	/* pte contains position in swap or file, so copy. */
666 	if (unlikely(!pte_present(pte))) {
667 		if (!pte_file(pte)) {
668 			swp_entry_t entry = pte_to_swp_entry(pte);
669 
670 			if (swap_duplicate(entry) < 0)
671 				return entry.val;
672 
673 			/* make sure dst_mm is on swapoff's mmlist. */
674 			if (unlikely(list_empty(&dst_mm->mmlist))) {
675 				spin_lock(&mmlist_lock);
676 				if (list_empty(&dst_mm->mmlist))
677 					list_add(&dst_mm->mmlist,
678 						 &src_mm->mmlist);
679 				spin_unlock(&mmlist_lock);
680 			}
681 			if (likely(!non_swap_entry(entry)))
682 				rss[MM_SWAPENTS]++;
683 			else if (is_write_migration_entry(entry) &&
684 					is_cow_mapping(vm_flags)) {
685 				/*
686 				 * COW mappings require pages in both parent
687 				 * and child to be set to read.
688 				 */
689 				make_migration_entry_read(&entry);
690 				pte = swp_entry_to_pte(entry);
691 				set_pte_at(src_mm, addr, src_pte, pte);
692 			}
693 		}
694 		goto out_set_pte;
695 	}
696 
697 	/*
698 	 * If it's a COW mapping, write protect it both
699 	 * in the parent and the child
700 	 */
701 	if (is_cow_mapping(vm_flags)) {
702 		ptep_set_wrprotect(src_mm, addr, src_pte);
703 		pte = pte_wrprotect(pte);
704 	}
705 
706 	/*
707 	 * If it's a shared mapping, mark it clean in
708 	 * the child
709 	 */
710 	if (vm_flags & VM_SHARED)
711 		pte = pte_mkclean(pte);
712 	pte = pte_mkold(pte);
713 
714 	page = vm_normal_page(vma, addr, pte);
715 	if (page) {
716 		get_page(page);
717 		page_dup_rmap(page);
718 		if (PageAnon(page))
719 			rss[MM_ANONPAGES]++;
720 		else
721 			rss[MM_FILEPAGES]++;
722 	}
723 
724 out_set_pte:
725 	set_pte_at(dst_mm, addr, dst_pte, pte);
726 	return 0;
727 }
728 
729 int copy_pte_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
730 		   pmd_t *dst_pmd, pmd_t *src_pmd, struct vm_area_struct *vma,
731 		   unsigned long addr, unsigned long end)
732 {
733 	pte_t *orig_src_pte, *orig_dst_pte;
734 	pte_t *src_pte, *dst_pte;
735 	spinlock_t *src_ptl, *dst_ptl;
736 	int progress = 0;
737 	int rss[NR_MM_COUNTERS];
738 	swp_entry_t entry = (swp_entry_t){0};
739 
740 again:
741 	init_rss_vec(rss);
742 
743 	dst_pte = pte_alloc_map_lock(dst_mm, dst_pmd, addr, &dst_ptl);
744 	if (!dst_pte)
745 		return -ENOMEM;
746 	src_pte = pte_offset_map(src_pmd, addr);
747 	src_ptl = pte_lockptr(src_mm, src_pmd);
748 	spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
749 	orig_src_pte = src_pte;
750 	orig_dst_pte = dst_pte;
751 	arch_enter_lazy_mmu_mode();
752 
753 	do {
754 		/*
755 		 * We are holding two locks at this point - either of them
756 		 * could generate latencies in another task on another CPU.
757 		 */
758 		if (progress >= 32) {
759 			progress = 0;
760 			if (need_resched() ||
761 			    spin_needbreak(src_ptl) || spin_needbreak(dst_ptl))
762 				break;
763 		}
764 		if (pte_none(*src_pte)) {
765 			progress++;
766 			continue;
767 		}
768 		entry.val = copy_one_pte(dst_mm, src_mm, dst_pte, src_pte,
769 							vma, addr, rss);
770 		if (entry.val)
771 			break;
772 		progress += 8;
773 	} while (dst_pte++, src_pte++, addr += PAGE_SIZE, addr != end);
774 
775 	arch_leave_lazy_mmu_mode();
776 	spin_unlock(src_ptl);
777 	pte_unmap(orig_src_pte);
778 	add_mm_rss_vec(dst_mm, rss);
779 	pte_unmap_unlock(orig_dst_pte, dst_ptl);
780 	cond_resched();
781 
782 	if (entry.val) {
783 		if (add_swap_count_continuation(entry, GFP_KERNEL) < 0)
784 			return -ENOMEM;
785 		progress = 0;
786 	}
787 	if (addr != end)
788 		goto again;
789 	return 0;
790 }
791 
792 static inline int copy_pmd_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
793 		pud_t *dst_pud, pud_t *src_pud, struct vm_area_struct *vma,
794 		unsigned long addr, unsigned long end)
795 {
796 	pmd_t *src_pmd, *dst_pmd;
797 	unsigned long next;
798 
799 	dst_pmd = pmd_alloc(dst_mm, dst_pud, addr);
800 	if (!dst_pmd)
801 		return -ENOMEM;
802 	src_pmd = pmd_offset(src_pud, addr);
803 	do {
804 		next = pmd_addr_end(addr, end);
805 		if (pmd_trans_huge(*src_pmd)) {
806 			int err;
807 			VM_BUG_ON(next-addr != HPAGE_PMD_SIZE);
808 			err = copy_huge_pmd(dst_mm, src_mm,
809 					    dst_pmd, src_pmd, addr, vma);
810 			if (err == -ENOMEM)
811 				return -ENOMEM;
812 			if (!err)
813 				continue;
814 			/* fall through */
815 		}
816 		if (pmd_none_or_clear_bad(src_pmd))
817 			continue;
818 		if (copy_pte_range(dst_mm, src_mm, dst_pmd, src_pmd,
819 						vma, addr, next))
820 			return -ENOMEM;
821 	} while (dst_pmd++, src_pmd++, addr = next, addr != end);
822 	return 0;
823 }
824 
825 static inline int copy_pud_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
826 		pgd_t *dst_pgd, pgd_t *src_pgd, struct vm_area_struct *vma,
827 		unsigned long addr, unsigned long end)
828 {
829 	pud_t *src_pud, *dst_pud;
830 	unsigned long next;
831 
832 	dst_pud = pud_alloc(dst_mm, dst_pgd, addr);
833 	if (!dst_pud)
834 		return -ENOMEM;
835 	src_pud = pud_offset(src_pgd, addr);
836 	do {
837 		next = pud_addr_end(addr, end);
838 		if (pud_none_or_clear_bad(src_pud))
839 			continue;
840 		if (copy_pmd_range(dst_mm, src_mm, dst_pud, src_pud,
841 						vma, addr, next))
842 			return -ENOMEM;
843 	} while (dst_pud++, src_pud++, addr = next, addr != end);
844 	return 0;
845 }
846 
847 int copy_page_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
848 		struct vm_area_struct *vma)
849 {
850 	pgd_t *src_pgd, *dst_pgd;
851 	unsigned long next;
852 	unsigned long addr = vma->vm_start;
853 	unsigned long end = vma->vm_end;
854 	int ret;
855 
856 	/*
857 	 * Don't copy ptes where a page fault will fill them correctly.
858 	 * Fork becomes much lighter when there are big shared or private
859 	 * readonly mappings. The tradeoff is that copy_page_range is more
860 	 * efficient than faulting.
861 	 */
862 	if (!(vma->vm_flags & (VM_HUGETLB|VM_NONLINEAR|VM_PFNMAP|VM_INSERTPAGE))) {
863 		if (!vma->anon_vma)
864 			return 0;
865 	}
866 
867 	if (is_vm_hugetlb_page(vma))
868 		return copy_hugetlb_page_range(dst_mm, src_mm, vma);
869 
870 	if (unlikely(is_pfn_mapping(vma))) {
871 		/*
872 		 * We do not free on error cases below as remove_vma
873 		 * gets called on error from higher level routine
874 		 */
875 		ret = track_pfn_vma_copy(vma);
876 		if (ret)
877 			return ret;
878 	}
879 
880 	/*
881 	 * We need to invalidate the secondary MMU mappings only when
882 	 * there could be a permission downgrade on the ptes of the
883 	 * parent mm. And a permission downgrade will only happen if
884 	 * is_cow_mapping() returns true.
885 	 */
886 	if (is_cow_mapping(vma->vm_flags))
887 		mmu_notifier_invalidate_range_start(src_mm, addr, end);
888 
889 	ret = 0;
890 	dst_pgd = pgd_offset(dst_mm, addr);
891 	src_pgd = pgd_offset(src_mm, addr);
892 	do {
893 		next = pgd_addr_end(addr, end);
894 		if (pgd_none_or_clear_bad(src_pgd))
895 			continue;
896 		if (unlikely(copy_pud_range(dst_mm, src_mm, dst_pgd, src_pgd,
897 					    vma, addr, next))) {
898 			ret = -ENOMEM;
899 			break;
900 		}
901 	} while (dst_pgd++, src_pgd++, addr = next, addr != end);
902 
903 	if (is_cow_mapping(vma->vm_flags))
904 		mmu_notifier_invalidate_range_end(src_mm,
905 						  vma->vm_start, end);
906 	return ret;
907 }
908 
909 static unsigned long zap_pte_range(struct mmu_gather *tlb,
910 				struct vm_area_struct *vma, pmd_t *pmd,
911 				unsigned long addr, unsigned long end,
912 				long *zap_work, struct zap_details *details)
913 {
914 	struct mm_struct *mm = tlb->mm;
915 	pte_t *pte;
916 	spinlock_t *ptl;
917 	int rss[NR_MM_COUNTERS];
918 
919 	init_rss_vec(rss);
920 
921 	pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
922 	arch_enter_lazy_mmu_mode();
923 	do {
924 		pte_t ptent = *pte;
925 		if (pte_none(ptent)) {
926 			(*zap_work)--;
927 			continue;
928 		}
929 
930 		(*zap_work) -= PAGE_SIZE;
931 
932 		if (pte_present(ptent)) {
933 			struct page *page;
934 
935 			page = vm_normal_page(vma, addr, ptent);
936 			if (unlikely(details) && page) {
937 				/*
938 				 * unmap_shared_mapping_pages() wants to
939 				 * invalidate cache without truncating:
940 				 * unmap shared but keep private pages.
941 				 */
942 				if (details->check_mapping &&
943 				    details->check_mapping != page->mapping)
944 					continue;
945 				/*
946 				 * Each page->index must be checked when
947 				 * invalidating or truncating nonlinear.
948 				 */
949 				if (details->nonlinear_vma &&
950 				    (page->index < details->first_index ||
951 				     page->index > details->last_index))
952 					continue;
953 			}
954 			ptent = ptep_get_and_clear_full(mm, addr, pte,
955 							tlb->fullmm);
956 			tlb_remove_tlb_entry(tlb, pte, addr);
957 			if (unlikely(!page))
958 				continue;
959 			if (unlikely(details) && details->nonlinear_vma
960 			    && linear_page_index(details->nonlinear_vma,
961 						addr) != page->index)
962 				set_pte_at(mm, addr, pte,
963 					   pgoff_to_pte(page->index));
964 			if (PageAnon(page))
965 				rss[MM_ANONPAGES]--;
966 			else {
967 				if (pte_dirty(ptent))
968 					set_page_dirty(page);
969 				if (pte_young(ptent) &&
970 				    likely(!VM_SequentialReadHint(vma)))
971 					mark_page_accessed(page);
972 				rss[MM_FILEPAGES]--;
973 			}
974 			page_remove_rmap(page);
975 			if (unlikely(page_mapcount(page) < 0))
976 				print_bad_pte(vma, addr, ptent, page);
977 			tlb_remove_page(tlb, page);
978 			continue;
979 		}
980 		/*
981 		 * If details->check_mapping, we leave swap entries;
982 		 * if details->nonlinear_vma, we leave file entries.
983 		 */
984 		if (unlikely(details))
985 			continue;
986 		if (pte_file(ptent)) {
987 			if (unlikely(!(vma->vm_flags & VM_NONLINEAR)))
988 				print_bad_pte(vma, addr, ptent, NULL);
989 		} else {
990 			swp_entry_t entry = pte_to_swp_entry(ptent);
991 
992 			if (!non_swap_entry(entry))
993 				rss[MM_SWAPENTS]--;
994 			if (unlikely(!free_swap_and_cache(entry)))
995 				print_bad_pte(vma, addr, ptent, NULL);
996 		}
997 		pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
998 	} while (pte++, addr += PAGE_SIZE, (addr != end && *zap_work > 0));
999 
1000 	add_mm_rss_vec(mm, rss);
1001 	arch_leave_lazy_mmu_mode();
1002 	pte_unmap_unlock(pte - 1, ptl);
1003 
1004 	return addr;
1005 }
1006 
1007 static inline unsigned long zap_pmd_range(struct mmu_gather *tlb,
1008 				struct vm_area_struct *vma, pud_t *pud,
1009 				unsigned long addr, unsigned long end,
1010 				long *zap_work, struct zap_details *details)
1011 {
1012 	pmd_t *pmd;
1013 	unsigned long next;
1014 
1015 	pmd = pmd_offset(pud, addr);
1016 	do {
1017 		next = pmd_addr_end(addr, end);
1018 		if (pmd_trans_huge(*pmd)) {
1019 			if (next-addr != HPAGE_PMD_SIZE) {
1020 				VM_BUG_ON(!rwsem_is_locked(&tlb->mm->mmap_sem));
1021 				split_huge_page_pmd(vma->vm_mm, pmd);
1022 			} else if (zap_huge_pmd(tlb, vma, pmd)) {
1023 				(*zap_work)--;
1024 				continue;
1025 			}
1026 			/* fall through */
1027 		}
1028 		if (pmd_none_or_clear_bad(pmd)) {
1029 			(*zap_work)--;
1030 			continue;
1031 		}
1032 		next = zap_pte_range(tlb, vma, pmd, addr, next,
1033 						zap_work, details);
1034 	} while (pmd++, addr = next, (addr != end && *zap_work > 0));
1035 
1036 	return addr;
1037 }
1038 
1039 static inline unsigned long zap_pud_range(struct mmu_gather *tlb,
1040 				struct vm_area_struct *vma, pgd_t *pgd,
1041 				unsigned long addr, unsigned long end,
1042 				long *zap_work, struct zap_details *details)
1043 {
1044 	pud_t *pud;
1045 	unsigned long next;
1046 
1047 	pud = pud_offset(pgd, addr);
1048 	do {
1049 		next = pud_addr_end(addr, end);
1050 		if (pud_none_or_clear_bad(pud)) {
1051 			(*zap_work)--;
1052 			continue;
1053 		}
1054 		next = zap_pmd_range(tlb, vma, pud, addr, next,
1055 						zap_work, details);
1056 	} while (pud++, addr = next, (addr != end && *zap_work > 0));
1057 
1058 	return addr;
1059 }
1060 
1061 static unsigned long unmap_page_range(struct mmu_gather *tlb,
1062 				struct vm_area_struct *vma,
1063 				unsigned long addr, unsigned long end,
1064 				long *zap_work, struct zap_details *details)
1065 {
1066 	pgd_t *pgd;
1067 	unsigned long next;
1068 
1069 	if (details && !details->check_mapping && !details->nonlinear_vma)
1070 		details = NULL;
1071 
1072 	BUG_ON(addr >= end);
1073 	mem_cgroup_uncharge_start();
1074 	tlb_start_vma(tlb, vma);
1075 	pgd = pgd_offset(vma->vm_mm, addr);
1076 	do {
1077 		next = pgd_addr_end(addr, end);
1078 		if (pgd_none_or_clear_bad(pgd)) {
1079 			(*zap_work)--;
1080 			continue;
1081 		}
1082 		next = zap_pud_range(tlb, vma, pgd, addr, next,
1083 						zap_work, details);
1084 	} while (pgd++, addr = next, (addr != end && *zap_work > 0));
1085 	tlb_end_vma(tlb, vma);
1086 	mem_cgroup_uncharge_end();
1087 
1088 	return addr;
1089 }
1090 
1091 #ifdef CONFIG_PREEMPT
1092 # define ZAP_BLOCK_SIZE	(8 * PAGE_SIZE)
1093 #else
1094 /* No preempt: go for improved straight-line efficiency */
1095 # define ZAP_BLOCK_SIZE	(1024 * PAGE_SIZE)
1096 #endif
1097 
1098 /**
1099  * unmap_vmas - unmap a range of memory covered by a list of vma's
1100  * @tlbp: address of the caller's struct mmu_gather
1101  * @vma: the starting vma
1102  * @start_addr: virtual address at which to start unmapping
1103  * @end_addr: virtual address at which to end unmapping
1104  * @nr_accounted: Place number of unmapped pages in vm-accountable vma's here
1105  * @details: details of nonlinear truncation or shared cache invalidation
1106  *
1107  * Returns the end address of the unmapping (restart addr if interrupted).
1108  *
1109  * Unmap all pages in the vma list.
1110  *
1111  * We aim to not hold locks for too long (for scheduling latency reasons).
1112  * So zap pages in ZAP_BLOCK_SIZE bytecounts.  This means we need to
1113  * return the ending mmu_gather to the caller.
1114  *
1115  * Only addresses between `start' and `end' will be unmapped.
1116  *
1117  * The VMA list must be sorted in ascending virtual address order.
1118  *
1119  * unmap_vmas() assumes that the caller will flush the whole unmapped address
1120  * range after unmap_vmas() returns.  So the only responsibility here is to
1121  * ensure that any thus-far unmapped pages are flushed before unmap_vmas()
1122  * drops the lock and schedules.
1123  */
1124 unsigned long unmap_vmas(struct mmu_gather **tlbp,
1125 		struct vm_area_struct *vma, unsigned long start_addr,
1126 		unsigned long end_addr, unsigned long *nr_accounted,
1127 		struct zap_details *details)
1128 {
1129 	long zap_work = ZAP_BLOCK_SIZE;
1130 	unsigned long tlb_start = 0;	/* For tlb_finish_mmu */
1131 	int tlb_start_valid = 0;
1132 	unsigned long start = start_addr;
1133 	spinlock_t *i_mmap_lock = details? details->i_mmap_lock: NULL;
1134 	int fullmm = (*tlbp)->fullmm;
1135 	struct mm_struct *mm = vma->vm_mm;
1136 
1137 	mmu_notifier_invalidate_range_start(mm, start_addr, end_addr);
1138 	for ( ; vma && vma->vm_start < end_addr; vma = vma->vm_next) {
1139 		unsigned long end;
1140 
1141 		start = max(vma->vm_start, start_addr);
1142 		if (start >= vma->vm_end)
1143 			continue;
1144 		end = min(vma->vm_end, end_addr);
1145 		if (end <= vma->vm_start)
1146 			continue;
1147 
1148 		if (vma->vm_flags & VM_ACCOUNT)
1149 			*nr_accounted += (end - start) >> PAGE_SHIFT;
1150 
1151 		if (unlikely(is_pfn_mapping(vma)))
1152 			untrack_pfn_vma(vma, 0, 0);
1153 
1154 		while (start != end) {
1155 			if (!tlb_start_valid) {
1156 				tlb_start = start;
1157 				tlb_start_valid = 1;
1158 			}
1159 
1160 			if (unlikely(is_vm_hugetlb_page(vma))) {
1161 				/*
1162 				 * It is undesirable to test vma->vm_file as it
1163 				 * should be non-null for valid hugetlb area.
1164 				 * However, vm_file will be NULL in the error
1165 				 * cleanup path of do_mmap_pgoff. When
1166 				 * hugetlbfs ->mmap method fails,
1167 				 * do_mmap_pgoff() nullifies vma->vm_file
1168 				 * before calling this function to clean up.
1169 				 * Since no pte has actually been setup, it is
1170 				 * safe to do nothing in this case.
1171 				 */
1172 				if (vma->vm_file) {
1173 					unmap_hugepage_range(vma, start, end, NULL);
1174 					zap_work -= (end - start) /
1175 					pages_per_huge_page(hstate_vma(vma));
1176 				}
1177 
1178 				start = end;
1179 			} else
1180 				start = unmap_page_range(*tlbp, vma,
1181 						start, end, &zap_work, details);
1182 
1183 			if (zap_work > 0) {
1184 				BUG_ON(start != end);
1185 				break;
1186 			}
1187 
1188 			tlb_finish_mmu(*tlbp, tlb_start, start);
1189 
1190 			if (need_resched() ||
1191 				(i_mmap_lock && spin_needbreak(i_mmap_lock))) {
1192 				if (i_mmap_lock) {
1193 					*tlbp = NULL;
1194 					goto out;
1195 				}
1196 				cond_resched();
1197 			}
1198 
1199 			*tlbp = tlb_gather_mmu(vma->vm_mm, fullmm);
1200 			tlb_start_valid = 0;
1201 			zap_work = ZAP_BLOCK_SIZE;
1202 		}
1203 	}
1204 out:
1205 	mmu_notifier_invalidate_range_end(mm, start_addr, end_addr);
1206 	return start;	/* which is now the end (or restart) address */
1207 }
1208 
1209 /**
1210  * zap_page_range - remove user pages in a given range
1211  * @vma: vm_area_struct holding the applicable pages
1212  * @address: starting address of pages to zap
1213  * @size: number of bytes to zap
1214  * @details: details of nonlinear truncation or shared cache invalidation
1215  */
1216 unsigned long zap_page_range(struct vm_area_struct *vma, unsigned long address,
1217 		unsigned long size, struct zap_details *details)
1218 {
1219 	struct mm_struct *mm = vma->vm_mm;
1220 	struct mmu_gather *tlb;
1221 	unsigned long end = address + size;
1222 	unsigned long nr_accounted = 0;
1223 
1224 	lru_add_drain();
1225 	tlb = tlb_gather_mmu(mm, 0);
1226 	update_hiwater_rss(mm);
1227 	end = unmap_vmas(&tlb, vma, address, end, &nr_accounted, details);
1228 	if (tlb)
1229 		tlb_finish_mmu(tlb, address, end);
1230 	return end;
1231 }
1232 
1233 /**
1234  * zap_vma_ptes - remove ptes mapping the vma
1235  * @vma: vm_area_struct holding ptes to be zapped
1236  * @address: starting address of pages to zap
1237  * @size: number of bytes to zap
1238  *
1239  * This function only unmaps ptes assigned to VM_PFNMAP vmas.
1240  *
1241  * The entire address range must be fully contained within the vma.
1242  *
1243  * Returns 0 if successful.
1244  */
1245 int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
1246 		unsigned long size)
1247 {
1248 	if (address < vma->vm_start || address + size > vma->vm_end ||
1249 	    		!(vma->vm_flags & VM_PFNMAP))
1250 		return -1;
1251 	zap_page_range(vma, address, size, NULL);
1252 	return 0;
1253 }
1254 EXPORT_SYMBOL_GPL(zap_vma_ptes);
1255 
1256 /**
1257  * follow_page - look up a page descriptor from a user-virtual address
1258  * @vma: vm_area_struct mapping @address
1259  * @address: virtual address to look up
1260  * @flags: flags modifying lookup behaviour
1261  *
1262  * @flags can have FOLL_ flags set, defined in <linux/mm.h>
1263  *
1264  * Returns the mapped (struct page *), %NULL if no mapping exists, or
1265  * an error pointer if there is a mapping to something not represented
1266  * by a page descriptor (see also vm_normal_page()).
1267  */
1268 struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
1269 			unsigned int flags)
1270 {
1271 	pgd_t *pgd;
1272 	pud_t *pud;
1273 	pmd_t *pmd;
1274 	pte_t *ptep, pte;
1275 	spinlock_t *ptl;
1276 	struct page *page;
1277 	struct mm_struct *mm = vma->vm_mm;
1278 
1279 	page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
1280 	if (!IS_ERR(page)) {
1281 		BUG_ON(flags & FOLL_GET);
1282 		goto out;
1283 	}
1284 
1285 	page = NULL;
1286 	pgd = pgd_offset(mm, address);
1287 	if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
1288 		goto no_page_table;
1289 
1290 	pud = pud_offset(pgd, address);
1291 	if (pud_none(*pud))
1292 		goto no_page_table;
1293 	if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
1294 		BUG_ON(flags & FOLL_GET);
1295 		page = follow_huge_pud(mm, address, pud, flags & FOLL_WRITE);
1296 		goto out;
1297 	}
1298 	if (unlikely(pud_bad(*pud)))
1299 		goto no_page_table;
1300 
1301 	pmd = pmd_offset(pud, address);
1302 	if (pmd_none(*pmd))
1303 		goto no_page_table;
1304 	if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
1305 		BUG_ON(flags & FOLL_GET);
1306 		page = follow_huge_pmd(mm, address, pmd, flags & FOLL_WRITE);
1307 		goto out;
1308 	}
1309 	if (pmd_trans_huge(*pmd)) {
1310 		if (flags & FOLL_SPLIT) {
1311 			split_huge_page_pmd(mm, pmd);
1312 			goto split_fallthrough;
1313 		}
1314 		spin_lock(&mm->page_table_lock);
1315 		if (likely(pmd_trans_huge(*pmd))) {
1316 			if (unlikely(pmd_trans_splitting(*pmd))) {
1317 				spin_unlock(&mm->page_table_lock);
1318 				wait_split_huge_page(vma->anon_vma, pmd);
1319 			} else {
1320 				page = follow_trans_huge_pmd(mm, address,
1321 							     pmd, flags);
1322 				spin_unlock(&mm->page_table_lock);
1323 				goto out;
1324 			}
1325 		} else
1326 			spin_unlock(&mm->page_table_lock);
1327 		/* fall through */
1328 	}
1329 split_fallthrough:
1330 	if (unlikely(pmd_bad(*pmd)))
1331 		goto no_page_table;
1332 
1333 	ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
1334 
1335 	pte = *ptep;
1336 	if (!pte_present(pte))
1337 		goto no_page;
1338 	if ((flags & FOLL_WRITE) && !pte_write(pte))
1339 		goto unlock;
1340 
1341 	page = vm_normal_page(vma, address, pte);
1342 	if (unlikely(!page)) {
1343 		if ((flags & FOLL_DUMP) ||
1344 		    !is_zero_pfn(pte_pfn(pte)))
1345 			goto bad_page;
1346 		page = pte_page(pte);
1347 	}
1348 
1349 	if (flags & FOLL_GET)
1350 		get_page(page);
1351 	if (flags & FOLL_TOUCH) {
1352 		if ((flags & FOLL_WRITE) &&
1353 		    !pte_dirty(pte) && !PageDirty(page))
1354 			set_page_dirty(page);
1355 		/*
1356 		 * pte_mkyoung() would be more correct here, but atomic care
1357 		 * is needed to avoid losing the dirty bit: it is easier to use
1358 		 * mark_page_accessed().
1359 		 */
1360 		mark_page_accessed(page);
1361 	}
1362 	if (flags & FOLL_MLOCK) {
1363 		/*
1364 		 * The preliminary mapping check is mainly to avoid the
1365 		 * pointless overhead of lock_page on the ZERO_PAGE
1366 		 * which might bounce very badly if there is contention.
1367 		 *
1368 		 * If the page is already locked, we don't need to
1369 		 * handle it now - vmscan will handle it later if and
1370 		 * when it attempts to reclaim the page.
1371 		 */
1372 		if (page->mapping && trylock_page(page)) {
1373 			lru_add_drain();  /* push cached pages to LRU */
1374 			/*
1375 			 * Because we lock page here and migration is
1376 			 * blocked by the pte's page reference, we need
1377 			 * only check for file-cache page truncation.
1378 			 */
1379 			if (page->mapping)
1380 				mlock_vma_page(page);
1381 			unlock_page(page);
1382 		}
1383 	}
1384 unlock:
1385 	pte_unmap_unlock(ptep, ptl);
1386 out:
1387 	return page;
1388 
1389 bad_page:
1390 	pte_unmap_unlock(ptep, ptl);
1391 	return ERR_PTR(-EFAULT);
1392 
1393 no_page:
1394 	pte_unmap_unlock(ptep, ptl);
1395 	if (!pte_none(pte))
1396 		return page;
1397 
1398 no_page_table:
1399 	/*
1400 	 * When core dumping an enormous anonymous area that nobody
1401 	 * has touched so far, we don't want to allocate unnecessary pages or
1402 	 * page tables.  Return error instead of NULL to skip handle_mm_fault,
1403 	 * then get_dump_page() will return NULL to leave a hole in the dump.
1404 	 * But we can only make this optimization where a hole would surely
1405 	 * be zero-filled if handle_mm_fault() actually did handle it.
1406 	 */
1407 	if ((flags & FOLL_DUMP) &&
1408 	    (!vma->vm_ops || !vma->vm_ops->fault))
1409 		return ERR_PTR(-EFAULT);
1410 	return page;
1411 }
1412 
1413 int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
1414 		     unsigned long start, int nr_pages, unsigned int gup_flags,
1415 		     struct page **pages, struct vm_area_struct **vmas,
1416 		     int *nonblocking)
1417 {
1418 	int i;
1419 	unsigned long vm_flags;
1420 
1421 	if (nr_pages <= 0)
1422 		return 0;
1423 
1424 	VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
1425 
1426 	/*
1427 	 * Require read or write permissions.
1428 	 * If FOLL_FORCE is set, we only require the "MAY" flags.
1429 	 */
1430 	vm_flags  = (gup_flags & FOLL_WRITE) ?
1431 			(VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
1432 	vm_flags &= (gup_flags & FOLL_FORCE) ?
1433 			(VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
1434 	i = 0;
1435 
1436 	do {
1437 		struct vm_area_struct *vma;
1438 
1439 		vma = find_extend_vma(mm, start);
1440 		if (!vma && in_gate_area(tsk, start)) {
1441 			unsigned long pg = start & PAGE_MASK;
1442 			struct vm_area_struct *gate_vma = get_gate_vma(tsk);
1443 			pgd_t *pgd;
1444 			pud_t *pud;
1445 			pmd_t *pmd;
1446 			pte_t *pte;
1447 
1448 			/* user gate pages are read-only */
1449 			if (gup_flags & FOLL_WRITE)
1450 				return i ? : -EFAULT;
1451 			if (pg > TASK_SIZE)
1452 				pgd = pgd_offset_k(pg);
1453 			else
1454 				pgd = pgd_offset_gate(mm, pg);
1455 			BUG_ON(pgd_none(*pgd));
1456 			pud = pud_offset(pgd, pg);
1457 			BUG_ON(pud_none(*pud));
1458 			pmd = pmd_offset(pud, pg);
1459 			if (pmd_none(*pmd))
1460 				return i ? : -EFAULT;
1461 			VM_BUG_ON(pmd_trans_huge(*pmd));
1462 			pte = pte_offset_map(pmd, pg);
1463 			if (pte_none(*pte)) {
1464 				pte_unmap(pte);
1465 				return i ? : -EFAULT;
1466 			}
1467 			if (pages) {
1468 				struct page *page;
1469 
1470 				page = vm_normal_page(gate_vma, start, *pte);
1471 				if (!page) {
1472 					if (!(gup_flags & FOLL_DUMP) &&
1473 					     is_zero_pfn(pte_pfn(*pte)))
1474 						page = pte_page(*pte);
1475 					else {
1476 						pte_unmap(pte);
1477 						return i ? : -EFAULT;
1478 					}
1479 				}
1480 				pages[i] = page;
1481 				get_page(page);
1482 			}
1483 			pte_unmap(pte);
1484 			if (vmas)
1485 				vmas[i] = gate_vma;
1486 			i++;
1487 			start += PAGE_SIZE;
1488 			nr_pages--;
1489 			continue;
1490 		}
1491 
1492 		if (!vma ||
1493 		    (vma->vm_flags & (VM_IO | VM_PFNMAP)) ||
1494 		    !(vm_flags & vma->vm_flags))
1495 			return i ? : -EFAULT;
1496 
1497 		if (is_vm_hugetlb_page(vma)) {
1498 			i = follow_hugetlb_page(mm, vma, pages, vmas,
1499 					&start, &nr_pages, i, gup_flags);
1500 			continue;
1501 		}
1502 
1503 		do {
1504 			struct page *page;
1505 			unsigned int foll_flags = gup_flags;
1506 
1507 			/*
1508 			 * If we have a pending SIGKILL, don't keep faulting
1509 			 * pages and potentially allocating memory.
1510 			 */
1511 			if (unlikely(fatal_signal_pending(current)))
1512 				return i ? i : -ERESTARTSYS;
1513 
1514 			cond_resched();
1515 			while (!(page = follow_page(vma, start, foll_flags))) {
1516 				int ret;
1517 				unsigned int fault_flags = 0;
1518 
1519 				if (foll_flags & FOLL_WRITE)
1520 					fault_flags |= FAULT_FLAG_WRITE;
1521 				if (nonblocking)
1522 					fault_flags |= FAULT_FLAG_ALLOW_RETRY;
1523 
1524 				ret = handle_mm_fault(mm, vma, start,
1525 							fault_flags);
1526 
1527 				if (ret & VM_FAULT_ERROR) {
1528 					if (ret & VM_FAULT_OOM)
1529 						return i ? i : -ENOMEM;
1530 					if (ret &
1531 					    (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE|
1532 					     VM_FAULT_SIGBUS))
1533 						return i ? i : -EFAULT;
1534 					BUG();
1535 				}
1536 				if (ret & VM_FAULT_MAJOR)
1537 					tsk->maj_flt++;
1538 				else
1539 					tsk->min_flt++;
1540 
1541 				if (ret & VM_FAULT_RETRY) {
1542 					*nonblocking = 0;
1543 					return i;
1544 				}
1545 
1546 				/*
1547 				 * The VM_FAULT_WRITE bit tells us that
1548 				 * do_wp_page has broken COW when necessary,
1549 				 * even if maybe_mkwrite decided not to set
1550 				 * pte_write. We can thus safely do subsequent
1551 				 * page lookups as if they were reads. But only
1552 				 * do so when looping for pte_write is futile:
1553 				 * in some cases userspace may also be wanting
1554 				 * to write to the gotten user page, which a
1555 				 * read fault here might prevent (a readonly
1556 				 * page might get reCOWed by userspace write).
1557 				 */
1558 				if ((ret & VM_FAULT_WRITE) &&
1559 				    !(vma->vm_flags & VM_WRITE))
1560 					foll_flags &= ~FOLL_WRITE;
1561 
1562 				cond_resched();
1563 			}
1564 			if (IS_ERR(page))
1565 				return i ? i : PTR_ERR(page);
1566 			if (pages) {
1567 				pages[i] = page;
1568 
1569 				flush_anon_page(vma, page, start);
1570 				flush_dcache_page(page);
1571 			}
1572 			if (vmas)
1573 				vmas[i] = vma;
1574 			i++;
1575 			start += PAGE_SIZE;
1576 			nr_pages--;
1577 		} while (nr_pages && start < vma->vm_end);
1578 	} while (nr_pages);
1579 	return i;
1580 }
1581 
1582 /**
1583  * get_user_pages() - pin user pages in memory
1584  * @tsk:	task_struct of target task
1585  * @mm:		mm_struct of target mm
1586  * @start:	starting user address
1587  * @nr_pages:	number of pages from start to pin
1588  * @write:	whether pages will be written to by the caller
1589  * @force:	whether to force write access even if user mapping is
1590  *		readonly. This will result in the page being COWed even
1591  *		in MAP_SHARED mappings. You do not want this.
1592  * @pages:	array that receives pointers to the pages pinned.
1593  *		Should be at least nr_pages long. Or NULL, if caller
1594  *		only intends to ensure the pages are faulted in.
1595  * @vmas:	array of pointers to vmas corresponding to each page.
1596  *		Or NULL if the caller does not require them.
1597  *
1598  * Returns number of pages pinned. This may be fewer than the number
1599  * requested. If nr_pages is 0 or negative, returns 0. If no pages
1600  * were pinned, returns -errno. Each page returned must be released
1601  * with a put_page() call when it is finished with. vmas will only
1602  * remain valid while mmap_sem is held.
1603  *
1604  * Must be called with mmap_sem held for read or write.
1605  *
1606  * get_user_pages walks a process's page tables and takes a reference to
1607  * each struct page that each user address corresponds to at a given
1608  * instant. That is, it takes the page that would be accessed if a user
1609  * thread accesses the given user virtual address at that instant.
1610  *
1611  * This does not guarantee that the page exists in the user mappings when
1612  * get_user_pages returns, and there may even be a completely different
1613  * page there in some cases (eg. if mmapped pagecache has been invalidated
1614  * and subsequently re faulted). However it does guarantee that the page
1615  * won't be freed completely. And mostly callers simply care that the page
1616  * contains data that was valid *at some point in time*. Typically, an IO
1617  * or similar operation cannot guarantee anything stronger anyway because
1618  * locks can't be held over the syscall boundary.
1619  *
1620  * If write=0, the page must not be written to. If the page is written to,
1621  * set_page_dirty (or set_page_dirty_lock, as appropriate) must be called
1622  * after the page is finished with, and before put_page is called.
1623  *
1624  * get_user_pages is typically used for fewer-copy IO operations, to get a
1625  * handle on the memory by some means other than accesses via the user virtual
1626  * addresses. The pages may be submitted for DMA to devices or accessed via
1627  * their kernel linear mapping (via the kmap APIs). Care should be taken to
1628  * use the correct cache flushing APIs.
1629  *
1630  * See also get_user_pages_fast, for performance critical applications.
1631  */
1632 int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
1633 		unsigned long start, int nr_pages, int write, int force,
1634 		struct page **pages, struct vm_area_struct **vmas)
1635 {
1636 	int flags = FOLL_TOUCH;
1637 
1638 	if (pages)
1639 		flags |= FOLL_GET;
1640 	if (write)
1641 		flags |= FOLL_WRITE;
1642 	if (force)
1643 		flags |= FOLL_FORCE;
1644 
1645 	return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas,
1646 				NULL);
1647 }
1648 EXPORT_SYMBOL(get_user_pages);
1649 
1650 /**
1651  * get_dump_page() - pin user page in memory while writing it to core dump
1652  * @addr: user address
1653  *
1654  * Returns struct page pointer of user page pinned for dump,
1655  * to be freed afterwards by page_cache_release() or put_page().
1656  *
1657  * Returns NULL on any kind of failure - a hole must then be inserted into
1658  * the corefile, to preserve alignment with its headers; and also returns
1659  * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
1660  * allowing a hole to be left in the corefile to save diskspace.
1661  *
1662  * Called without mmap_sem, but after all other threads have been killed.
1663  */
1664 #ifdef CONFIG_ELF_CORE
1665 struct page *get_dump_page(unsigned long addr)
1666 {
1667 	struct vm_area_struct *vma;
1668 	struct page *page;
1669 
1670 	if (__get_user_pages(current, current->mm, addr, 1,
1671 			     FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma,
1672 			     NULL) < 1)
1673 		return NULL;
1674 	flush_cache_page(vma, addr, page_to_pfn(page));
1675 	return page;
1676 }
1677 #endif /* CONFIG_ELF_CORE */
1678 
1679 pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr,
1680 			spinlock_t **ptl)
1681 {
1682 	pgd_t * pgd = pgd_offset(mm, addr);
1683 	pud_t * pud = pud_alloc(mm, pgd, addr);
1684 	if (pud) {
1685 		pmd_t * pmd = pmd_alloc(mm, pud, addr);
1686 		if (pmd) {
1687 			VM_BUG_ON(pmd_trans_huge(*pmd));
1688 			return pte_alloc_map_lock(mm, pmd, addr, ptl);
1689 		}
1690 	}
1691 	return NULL;
1692 }
1693 
1694 /*
1695  * This is the old fallback for page remapping.
1696  *
1697  * For historical reasons, it only allows reserved pages. Only
1698  * old drivers should use this, and they needed to mark their
1699  * pages reserved for the old functions anyway.
1700  */
1701 static int insert_page(struct vm_area_struct *vma, unsigned long addr,
1702 			struct page *page, pgprot_t prot)
1703 {
1704 	struct mm_struct *mm = vma->vm_mm;
1705 	int retval;
1706 	pte_t *pte;
1707 	spinlock_t *ptl;
1708 
1709 	retval = -EINVAL;
1710 	if (PageAnon(page))
1711 		goto out;
1712 	retval = -ENOMEM;
1713 	flush_dcache_page(page);
1714 	pte = get_locked_pte(mm, addr, &ptl);
1715 	if (!pte)
1716 		goto out;
1717 	retval = -EBUSY;
1718 	if (!pte_none(*pte))
1719 		goto out_unlock;
1720 
1721 	/* Ok, finally just insert the thing.. */
1722 	get_page(page);
1723 	inc_mm_counter_fast(mm, MM_FILEPAGES);
1724 	page_add_file_rmap(page);
1725 	set_pte_at(mm, addr, pte, mk_pte(page, prot));
1726 
1727 	retval = 0;
1728 	pte_unmap_unlock(pte, ptl);
1729 	return retval;
1730 out_unlock:
1731 	pte_unmap_unlock(pte, ptl);
1732 out:
1733 	return retval;
1734 }
1735 
1736 /**
1737  * vm_insert_page - insert single page into user vma
1738  * @vma: user vma to map to
1739  * @addr: target user address of this page
1740  * @page: source kernel page
1741  *
1742  * This allows drivers to insert individual pages they've allocated
1743  * into a user vma.
1744  *
1745  * The page has to be a nice clean _individual_ kernel allocation.
1746  * If you allocate a compound page, you need to have marked it as
1747  * such (__GFP_COMP), or manually just split the page up yourself
1748  * (see split_page()).
1749  *
1750  * NOTE! Traditionally this was done with "remap_pfn_range()" which
1751  * took an arbitrary page protection parameter. This doesn't allow
1752  * that. Your vma protection will have to be set up correctly, which
1753  * means that if you want a shared writable mapping, you'd better
1754  * ask for a shared writable mapping!
1755  *
1756  * The page does not need to be reserved.
1757  */
1758 int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
1759 			struct page *page)
1760 {
1761 	if (addr < vma->vm_start || addr >= vma->vm_end)
1762 		return -EFAULT;
1763 	if (!page_count(page))
1764 		return -EINVAL;
1765 	vma->vm_flags |= VM_INSERTPAGE;
1766 	return insert_page(vma, addr, page, vma->vm_page_prot);
1767 }
1768 EXPORT_SYMBOL(vm_insert_page);
1769 
1770 static int insert_pfn(struct vm_area_struct *vma, unsigned long addr,
1771 			unsigned long pfn, pgprot_t prot)
1772 {
1773 	struct mm_struct *mm = vma->vm_mm;
1774 	int retval;
1775 	pte_t *pte, entry;
1776 	spinlock_t *ptl;
1777 
1778 	retval = -ENOMEM;
1779 	pte = get_locked_pte(mm, addr, &ptl);
1780 	if (!pte)
1781 		goto out;
1782 	retval = -EBUSY;
1783 	if (!pte_none(*pte))
1784 		goto out_unlock;
1785 
1786 	/* Ok, finally just insert the thing.. */
1787 	entry = pte_mkspecial(pfn_pte(pfn, prot));
1788 	set_pte_at(mm, addr, pte, entry);
1789 	update_mmu_cache(vma, addr, pte); /* XXX: why not for insert_page? */
1790 
1791 	retval = 0;
1792 out_unlock:
1793 	pte_unmap_unlock(pte, ptl);
1794 out:
1795 	return retval;
1796 }
1797 
1798 /**
1799  * vm_insert_pfn - insert single pfn into user vma
1800  * @vma: user vma to map to
1801  * @addr: target user address of this page
1802  * @pfn: source kernel pfn
1803  *
1804  * Similar to vm_inert_page, this allows drivers to insert individual pages
1805  * they've allocated into a user vma. Same comments apply.
1806  *
1807  * This function should only be called from a vm_ops->fault handler, and
1808  * in that case the handler should return NULL.
1809  *
1810  * vma cannot be a COW mapping.
1811  *
1812  * As this is called only for pages that do not currently exist, we
1813  * do not need to flush old virtual caches or the TLB.
1814  */
1815 int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
1816 			unsigned long pfn)
1817 {
1818 	int ret;
1819 	pgprot_t pgprot = vma->vm_page_prot;
1820 	/*
1821 	 * Technically, architectures with pte_special can avoid all these
1822 	 * restrictions (same for remap_pfn_range).  However we would like
1823 	 * consistency in testing and feature parity among all, so we should
1824 	 * try to keep these invariants in place for everybody.
1825 	 */
1826 	BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
1827 	BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
1828 						(VM_PFNMAP|VM_MIXEDMAP));
1829 	BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
1830 	BUG_ON((vma->vm_flags & VM_MIXEDMAP) && pfn_valid(pfn));
1831 
1832 	if (addr < vma->vm_start || addr >= vma->vm_end)
1833 		return -EFAULT;
1834 	if (track_pfn_vma_new(vma, &pgprot, pfn, PAGE_SIZE))
1835 		return -EINVAL;
1836 
1837 	ret = insert_pfn(vma, addr, pfn, pgprot);
1838 
1839 	if (ret)
1840 		untrack_pfn_vma(vma, pfn, PAGE_SIZE);
1841 
1842 	return ret;
1843 }
1844 EXPORT_SYMBOL(vm_insert_pfn);
1845 
1846 int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
1847 			unsigned long pfn)
1848 {
1849 	BUG_ON(!(vma->vm_flags & VM_MIXEDMAP));
1850 
1851 	if (addr < vma->vm_start || addr >= vma->vm_end)
1852 		return -EFAULT;
1853 
1854 	/*
1855 	 * If we don't have pte special, then we have to use the pfn_valid()
1856 	 * based VM_MIXEDMAP scheme (see vm_normal_page), and thus we *must*
1857 	 * refcount the page if pfn_valid is true (hence insert_page rather
1858 	 * than insert_pfn).  If a zero_pfn were inserted into a VM_MIXEDMAP
1859 	 * without pte special, it would there be refcounted as a normal page.
1860 	 */
1861 	if (!HAVE_PTE_SPECIAL && pfn_valid(pfn)) {
1862 		struct page *page;
1863 
1864 		page = pfn_to_page(pfn);
1865 		return insert_page(vma, addr, page, vma->vm_page_prot);
1866 	}
1867 	return insert_pfn(vma, addr, pfn, vma->vm_page_prot);
1868 }
1869 EXPORT_SYMBOL(vm_insert_mixed);
1870 
1871 /*
1872  * maps a range of physical memory into the requested pages. the old
1873  * mappings are removed. any references to nonexistent pages results
1874  * in null mappings (currently treated as "copy-on-access")
1875  */
1876 static int remap_pte_range(struct mm_struct *mm, pmd_t *pmd,
1877 			unsigned long addr, unsigned long end,
1878 			unsigned long pfn, pgprot_t prot)
1879 {
1880 	pte_t *pte;
1881 	spinlock_t *ptl;
1882 
1883 	pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
1884 	if (!pte)
1885 		return -ENOMEM;
1886 	arch_enter_lazy_mmu_mode();
1887 	do {
1888 		BUG_ON(!pte_none(*pte));
1889 		set_pte_at(mm, addr, pte, pte_mkspecial(pfn_pte(pfn, prot)));
1890 		pfn++;
1891 	} while (pte++, addr += PAGE_SIZE, addr != end);
1892 	arch_leave_lazy_mmu_mode();
1893 	pte_unmap_unlock(pte - 1, ptl);
1894 	return 0;
1895 }
1896 
1897 static inline int remap_pmd_range(struct mm_struct *mm, pud_t *pud,
1898 			unsigned long addr, unsigned long end,
1899 			unsigned long pfn, pgprot_t prot)
1900 {
1901 	pmd_t *pmd;
1902 	unsigned long next;
1903 
1904 	pfn -= addr >> PAGE_SHIFT;
1905 	pmd = pmd_alloc(mm, pud, addr);
1906 	if (!pmd)
1907 		return -ENOMEM;
1908 	VM_BUG_ON(pmd_trans_huge(*pmd));
1909 	do {
1910 		next = pmd_addr_end(addr, end);
1911 		if (remap_pte_range(mm, pmd, addr, next,
1912 				pfn + (addr >> PAGE_SHIFT), prot))
1913 			return -ENOMEM;
1914 	} while (pmd++, addr = next, addr != end);
1915 	return 0;
1916 }
1917 
1918 static inline int remap_pud_range(struct mm_struct *mm, pgd_t *pgd,
1919 			unsigned long addr, unsigned long end,
1920 			unsigned long pfn, pgprot_t prot)
1921 {
1922 	pud_t *pud;
1923 	unsigned long next;
1924 
1925 	pfn -= addr >> PAGE_SHIFT;
1926 	pud = pud_alloc(mm, pgd, addr);
1927 	if (!pud)
1928 		return -ENOMEM;
1929 	do {
1930 		next = pud_addr_end(addr, end);
1931 		if (remap_pmd_range(mm, pud, addr, next,
1932 				pfn + (addr >> PAGE_SHIFT), prot))
1933 			return -ENOMEM;
1934 	} while (pud++, addr = next, addr != end);
1935 	return 0;
1936 }
1937 
1938 /**
1939  * remap_pfn_range - remap kernel memory to userspace
1940  * @vma: user vma to map to
1941  * @addr: target user address to start at
1942  * @pfn: physical address of kernel memory
1943  * @size: size of map area
1944  * @prot: page protection flags for this mapping
1945  *
1946  *  Note: this is only safe if the mm semaphore is held when called.
1947  */
1948 int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
1949 		    unsigned long pfn, unsigned long size, pgprot_t prot)
1950 {
1951 	pgd_t *pgd;
1952 	unsigned long next;
1953 	unsigned long end = addr + PAGE_ALIGN(size);
1954 	struct mm_struct *mm = vma->vm_mm;
1955 	int err;
1956 
1957 	/*
1958 	 * Physically remapped pages are special. Tell the
1959 	 * rest of the world about it:
1960 	 *   VM_IO tells people not to look at these pages
1961 	 *	(accesses can have side effects).
1962 	 *   VM_RESERVED is specified all over the place, because
1963 	 *	in 2.4 it kept swapout's vma scan off this vma; but
1964 	 *	in 2.6 the LRU scan won't even find its pages, so this
1965 	 *	flag means no more than count its pages in reserved_vm,
1966 	 * 	and omit it from core dump, even when VM_IO turned off.
1967 	 *   VM_PFNMAP tells the core MM that the base pages are just
1968 	 *	raw PFN mappings, and do not have a "struct page" associated
1969 	 *	with them.
1970 	 *
1971 	 * There's a horrible special case to handle copy-on-write
1972 	 * behaviour that some programs depend on. We mark the "original"
1973 	 * un-COW'ed pages by matching them up with "vma->vm_pgoff".
1974 	 */
1975 	if (addr == vma->vm_start && end == vma->vm_end) {
1976 		vma->vm_pgoff = pfn;
1977 		vma->vm_flags |= VM_PFN_AT_MMAP;
1978 	} else if (is_cow_mapping(vma->vm_flags))
1979 		return -EINVAL;
1980 
1981 	vma->vm_flags |= VM_IO | VM_RESERVED | VM_PFNMAP;
1982 
1983 	err = track_pfn_vma_new(vma, &prot, pfn, PAGE_ALIGN(size));
1984 	if (err) {
1985 		/*
1986 		 * To indicate that track_pfn related cleanup is not
1987 		 * needed from higher level routine calling unmap_vmas
1988 		 */
1989 		vma->vm_flags &= ~(VM_IO | VM_RESERVED | VM_PFNMAP);
1990 		vma->vm_flags &= ~VM_PFN_AT_MMAP;
1991 		return -EINVAL;
1992 	}
1993 
1994 	BUG_ON(addr >= end);
1995 	pfn -= addr >> PAGE_SHIFT;
1996 	pgd = pgd_offset(mm, addr);
1997 	flush_cache_range(vma, addr, end);
1998 	do {
1999 		next = pgd_addr_end(addr, end);
2000 		err = remap_pud_range(mm, pgd, addr, next,
2001 				pfn + (addr >> PAGE_SHIFT), prot);
2002 		if (err)
2003 			break;
2004 	} while (pgd++, addr = next, addr != end);
2005 
2006 	if (err)
2007 		untrack_pfn_vma(vma, pfn, PAGE_ALIGN(size));
2008 
2009 	return err;
2010 }
2011 EXPORT_SYMBOL(remap_pfn_range);
2012 
2013 static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
2014 				     unsigned long addr, unsigned long end,
2015 				     pte_fn_t fn, void *data)
2016 {
2017 	pte_t *pte;
2018 	int err;
2019 	pgtable_t token;
2020 	spinlock_t *uninitialized_var(ptl);
2021 
2022 	pte = (mm == &init_mm) ?
2023 		pte_alloc_kernel(pmd, addr) :
2024 		pte_alloc_map_lock(mm, pmd, addr, &ptl);
2025 	if (!pte)
2026 		return -ENOMEM;
2027 
2028 	BUG_ON(pmd_huge(*pmd));
2029 
2030 	arch_enter_lazy_mmu_mode();
2031 
2032 	token = pmd_pgtable(*pmd);
2033 
2034 	do {
2035 		err = fn(pte++, token, addr, data);
2036 		if (err)
2037 			break;
2038 	} while (addr += PAGE_SIZE, addr != end);
2039 
2040 	arch_leave_lazy_mmu_mode();
2041 
2042 	if (mm != &init_mm)
2043 		pte_unmap_unlock(pte-1, ptl);
2044 	return err;
2045 }
2046 
2047 static int apply_to_pmd_range(struct mm_struct *mm, pud_t *pud,
2048 				     unsigned long addr, unsigned long end,
2049 				     pte_fn_t fn, void *data)
2050 {
2051 	pmd_t *pmd;
2052 	unsigned long next;
2053 	int err;
2054 
2055 	BUG_ON(pud_huge(*pud));
2056 
2057 	pmd = pmd_alloc(mm, pud, addr);
2058 	if (!pmd)
2059 		return -ENOMEM;
2060 	do {
2061 		next = pmd_addr_end(addr, end);
2062 		err = apply_to_pte_range(mm, pmd, addr, next, fn, data);
2063 		if (err)
2064 			break;
2065 	} while (pmd++, addr = next, addr != end);
2066 	return err;
2067 }
2068 
2069 static int apply_to_pud_range(struct mm_struct *mm, pgd_t *pgd,
2070 				     unsigned long addr, unsigned long end,
2071 				     pte_fn_t fn, void *data)
2072 {
2073 	pud_t *pud;
2074 	unsigned long next;
2075 	int err;
2076 
2077 	pud = pud_alloc(mm, pgd, addr);
2078 	if (!pud)
2079 		return -ENOMEM;
2080 	do {
2081 		next = pud_addr_end(addr, end);
2082 		err = apply_to_pmd_range(mm, pud, addr, next, fn, data);
2083 		if (err)
2084 			break;
2085 	} while (pud++, addr = next, addr != end);
2086 	return err;
2087 }
2088 
2089 /*
2090  * Scan a region of virtual memory, filling in page tables as necessary
2091  * and calling a provided function on each leaf page table.
2092  */
2093 int apply_to_page_range(struct mm_struct *mm, unsigned long addr,
2094 			unsigned long size, pte_fn_t fn, void *data)
2095 {
2096 	pgd_t *pgd;
2097 	unsigned long next;
2098 	unsigned long end = addr + size;
2099 	int err;
2100 
2101 	BUG_ON(addr >= end);
2102 	pgd = pgd_offset(mm, addr);
2103 	do {
2104 		next = pgd_addr_end(addr, end);
2105 		err = apply_to_pud_range(mm, pgd, addr, next, fn, data);
2106 		if (err)
2107 			break;
2108 	} while (pgd++, addr = next, addr != end);
2109 
2110 	return err;
2111 }
2112 EXPORT_SYMBOL_GPL(apply_to_page_range);
2113 
2114 /*
2115  * handle_pte_fault chooses page fault handler according to an entry
2116  * which was read non-atomically.  Before making any commitment, on
2117  * those architectures or configurations (e.g. i386 with PAE) which
2118  * might give a mix of unmatched parts, do_swap_page and do_file_page
2119  * must check under lock before unmapping the pte and proceeding
2120  * (but do_wp_page is only called after already making such a check;
2121  * and do_anonymous_page and do_no_page can safely check later on).
2122  */
2123 static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd,
2124 				pte_t *page_table, pte_t orig_pte)
2125 {
2126 	int same = 1;
2127 #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
2128 	if (sizeof(pte_t) > sizeof(unsigned long)) {
2129 		spinlock_t *ptl = pte_lockptr(mm, pmd);
2130 		spin_lock(ptl);
2131 		same = pte_same(*page_table, orig_pte);
2132 		spin_unlock(ptl);
2133 	}
2134 #endif
2135 	pte_unmap(page_table);
2136 	return same;
2137 }
2138 
2139 static inline void cow_user_page(struct page *dst, struct page *src, unsigned long va, struct vm_area_struct *vma)
2140 {
2141 	/*
2142 	 * If the source page was a PFN mapping, we don't have
2143 	 * a "struct page" for it. We do a best-effort copy by
2144 	 * just copying from the original user address. If that
2145 	 * fails, we just zero-fill it. Live with it.
2146 	 */
2147 	if (unlikely(!src)) {
2148 		void *kaddr = kmap_atomic(dst, KM_USER0);
2149 		void __user *uaddr = (void __user *)(va & PAGE_MASK);
2150 
2151 		/*
2152 		 * This really shouldn't fail, because the page is there
2153 		 * in the page tables. But it might just be unreadable,
2154 		 * in which case we just give up and fill the result with
2155 		 * zeroes.
2156 		 */
2157 		if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE))
2158 			clear_page(kaddr);
2159 		kunmap_atomic(kaddr, KM_USER0);
2160 		flush_dcache_page(dst);
2161 	} else
2162 		copy_user_highpage(dst, src, va, vma);
2163 }
2164 
2165 /*
2166  * This routine handles present pages, when users try to write
2167  * to a shared page. It is done by copying the page to a new address
2168  * and decrementing the shared-page counter for the old page.
2169  *
2170  * Note that this routine assumes that the protection checks have been
2171  * done by the caller (the low-level page fault routine in most cases).
2172  * Thus we can safely just mark it writable once we've done any necessary
2173  * COW.
2174  *
2175  * We also mark the page dirty at this point even though the page will
2176  * change only once the write actually happens. This avoids a few races,
2177  * and potentially makes it more efficient.
2178  *
2179  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2180  * but allow concurrent faults), with pte both mapped and locked.
2181  * We return with mmap_sem still held, but pte unmapped and unlocked.
2182  */
2183 static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
2184 		unsigned long address, pte_t *page_table, pmd_t *pmd,
2185 		spinlock_t *ptl, pte_t orig_pte)
2186 	__releases(ptl)
2187 {
2188 	struct page *old_page, *new_page;
2189 	pte_t entry;
2190 	int ret = 0;
2191 	int page_mkwrite = 0;
2192 	struct page *dirty_page = NULL;
2193 
2194 	old_page = vm_normal_page(vma, address, orig_pte);
2195 	if (!old_page) {
2196 		/*
2197 		 * VM_MIXEDMAP !pfn_valid() case
2198 		 *
2199 		 * We should not cow pages in a shared writeable mapping.
2200 		 * Just mark the pages writable as we can't do any dirty
2201 		 * accounting on raw pfn maps.
2202 		 */
2203 		if ((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
2204 				     (VM_WRITE|VM_SHARED))
2205 			goto reuse;
2206 		goto gotten;
2207 	}
2208 
2209 	/*
2210 	 * Take out anonymous pages first, anonymous shared vmas are
2211 	 * not dirty accountable.
2212 	 */
2213 	if (PageAnon(old_page) && !PageKsm(old_page)) {
2214 		if (!trylock_page(old_page)) {
2215 			page_cache_get(old_page);
2216 			pte_unmap_unlock(page_table, ptl);
2217 			lock_page(old_page);
2218 			page_table = pte_offset_map_lock(mm, pmd, address,
2219 							 &ptl);
2220 			if (!pte_same(*page_table, orig_pte)) {
2221 				unlock_page(old_page);
2222 				goto unlock;
2223 			}
2224 			page_cache_release(old_page);
2225 		}
2226 		if (reuse_swap_page(old_page)) {
2227 			/*
2228 			 * The page is all ours.  Move it to our anon_vma so
2229 			 * the rmap code will not search our parent or siblings.
2230 			 * Protected against the rmap code by the page lock.
2231 			 */
2232 			page_move_anon_rmap(old_page, vma, address);
2233 			unlock_page(old_page);
2234 			goto reuse;
2235 		}
2236 		unlock_page(old_page);
2237 	} else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
2238 					(VM_WRITE|VM_SHARED))) {
2239 		/*
2240 		 * Only catch write-faults on shared writable pages,
2241 		 * read-only shared pages can get COWed by
2242 		 * get_user_pages(.write=1, .force=1).
2243 		 */
2244 		if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
2245 			struct vm_fault vmf;
2246 			int tmp;
2247 
2248 			vmf.virtual_address = (void __user *)(address &
2249 								PAGE_MASK);
2250 			vmf.pgoff = old_page->index;
2251 			vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
2252 			vmf.page = old_page;
2253 
2254 			/*
2255 			 * Notify the address space that the page is about to
2256 			 * become writable so that it can prohibit this or wait
2257 			 * for the page to get into an appropriate state.
2258 			 *
2259 			 * We do this without the lock held, so that it can
2260 			 * sleep if it needs to.
2261 			 */
2262 			page_cache_get(old_page);
2263 			pte_unmap_unlock(page_table, ptl);
2264 
2265 			tmp = vma->vm_ops->page_mkwrite(vma, &vmf);
2266 			if (unlikely(tmp &
2267 					(VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
2268 				ret = tmp;
2269 				goto unwritable_page;
2270 			}
2271 			if (unlikely(!(tmp & VM_FAULT_LOCKED))) {
2272 				lock_page(old_page);
2273 				if (!old_page->mapping) {
2274 					ret = 0; /* retry the fault */
2275 					unlock_page(old_page);
2276 					goto unwritable_page;
2277 				}
2278 			} else
2279 				VM_BUG_ON(!PageLocked(old_page));
2280 
2281 			/*
2282 			 * Since we dropped the lock we need to revalidate
2283 			 * the PTE as someone else may have changed it.  If
2284 			 * they did, we just return, as we can count on the
2285 			 * MMU to tell us if they didn't also make it writable.
2286 			 */
2287 			page_table = pte_offset_map_lock(mm, pmd, address,
2288 							 &ptl);
2289 			if (!pte_same(*page_table, orig_pte)) {
2290 				unlock_page(old_page);
2291 				goto unlock;
2292 			}
2293 
2294 			page_mkwrite = 1;
2295 		}
2296 		dirty_page = old_page;
2297 		get_page(dirty_page);
2298 
2299 reuse:
2300 		flush_cache_page(vma, address, pte_pfn(orig_pte));
2301 		entry = pte_mkyoung(orig_pte);
2302 		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2303 		if (ptep_set_access_flags(vma, address, page_table, entry,1))
2304 			update_mmu_cache(vma, address, page_table);
2305 		pte_unmap_unlock(page_table, ptl);
2306 		ret |= VM_FAULT_WRITE;
2307 
2308 		if (!dirty_page)
2309 			return ret;
2310 
2311 		/*
2312 		 * Yes, Virginia, this is actually required to prevent a race
2313 		 * with clear_page_dirty_for_io() from clearing the page dirty
2314 		 * bit after it clear all dirty ptes, but before a racing
2315 		 * do_wp_page installs a dirty pte.
2316 		 *
2317 		 * do_no_page is protected similarly.
2318 		 */
2319 		if (!page_mkwrite) {
2320 			wait_on_page_locked(dirty_page);
2321 			set_page_dirty_balance(dirty_page, page_mkwrite);
2322 		}
2323 		put_page(dirty_page);
2324 		if (page_mkwrite) {
2325 			struct address_space *mapping = dirty_page->mapping;
2326 
2327 			set_page_dirty(dirty_page);
2328 			unlock_page(dirty_page);
2329 			page_cache_release(dirty_page);
2330 			if (mapping)	{
2331 				/*
2332 				 * Some device drivers do not set page.mapping
2333 				 * but still dirty their pages
2334 				 */
2335 				balance_dirty_pages_ratelimited(mapping);
2336 			}
2337 		}
2338 
2339 		/* file_update_time outside page_lock */
2340 		if (vma->vm_file)
2341 			file_update_time(vma->vm_file);
2342 
2343 		return ret;
2344 	}
2345 
2346 	/*
2347 	 * Ok, we need to copy. Oh, well..
2348 	 */
2349 	page_cache_get(old_page);
2350 gotten:
2351 	pte_unmap_unlock(page_table, ptl);
2352 
2353 	if (unlikely(anon_vma_prepare(vma)))
2354 		goto oom;
2355 
2356 	if (is_zero_pfn(pte_pfn(orig_pte))) {
2357 		new_page = alloc_zeroed_user_highpage_movable(vma, address);
2358 		if (!new_page)
2359 			goto oom;
2360 	} else {
2361 		new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
2362 		if (!new_page)
2363 			goto oom;
2364 		cow_user_page(new_page, old_page, address, vma);
2365 	}
2366 	__SetPageUptodate(new_page);
2367 
2368 	if (mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))
2369 		goto oom_free_new;
2370 
2371 	/*
2372 	 * Re-check the pte - we dropped the lock
2373 	 */
2374 	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2375 	if (likely(pte_same(*page_table, orig_pte))) {
2376 		if (old_page) {
2377 			if (!PageAnon(old_page)) {
2378 				dec_mm_counter_fast(mm, MM_FILEPAGES);
2379 				inc_mm_counter_fast(mm, MM_ANONPAGES);
2380 			}
2381 		} else
2382 			inc_mm_counter_fast(mm, MM_ANONPAGES);
2383 		flush_cache_page(vma, address, pte_pfn(orig_pte));
2384 		entry = mk_pte(new_page, vma->vm_page_prot);
2385 		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
2386 		/*
2387 		 * Clear the pte entry and flush it first, before updating the
2388 		 * pte with the new entry. This will avoid a race condition
2389 		 * seen in the presence of one thread doing SMC and another
2390 		 * thread doing COW.
2391 		 */
2392 		ptep_clear_flush(vma, address, page_table);
2393 		page_add_new_anon_rmap(new_page, vma, address);
2394 		/*
2395 		 * We call the notify macro here because, when using secondary
2396 		 * mmu page tables (such as kvm shadow page tables), we want the
2397 		 * new page to be mapped directly into the secondary page table.
2398 		 */
2399 		set_pte_at_notify(mm, address, page_table, entry);
2400 		update_mmu_cache(vma, address, page_table);
2401 		if (old_page) {
2402 			/*
2403 			 * Only after switching the pte to the new page may
2404 			 * we remove the mapcount here. Otherwise another
2405 			 * process may come and find the rmap count decremented
2406 			 * before the pte is switched to the new page, and
2407 			 * "reuse" the old page writing into it while our pte
2408 			 * here still points into it and can be read by other
2409 			 * threads.
2410 			 *
2411 			 * The critical issue is to order this
2412 			 * page_remove_rmap with the ptp_clear_flush above.
2413 			 * Those stores are ordered by (if nothing else,)
2414 			 * the barrier present in the atomic_add_negative
2415 			 * in page_remove_rmap.
2416 			 *
2417 			 * Then the TLB flush in ptep_clear_flush ensures that
2418 			 * no process can access the old page before the
2419 			 * decremented mapcount is visible. And the old page
2420 			 * cannot be reused until after the decremented
2421 			 * mapcount is visible. So transitively, TLBs to
2422 			 * old page will be flushed before it can be reused.
2423 			 */
2424 			page_remove_rmap(old_page);
2425 		}
2426 
2427 		/* Free the old page.. */
2428 		new_page = old_page;
2429 		ret |= VM_FAULT_WRITE;
2430 	} else
2431 		mem_cgroup_uncharge_page(new_page);
2432 
2433 	if (new_page)
2434 		page_cache_release(new_page);
2435 unlock:
2436 	pte_unmap_unlock(page_table, ptl);
2437 	if (old_page) {
2438 		/*
2439 		 * Don't let another task, with possibly unlocked vma,
2440 		 * keep the mlocked page.
2441 		 */
2442 		if ((ret & VM_FAULT_WRITE) && (vma->vm_flags & VM_LOCKED)) {
2443 			lock_page(old_page);	/* LRU manipulation */
2444 			munlock_vma_page(old_page);
2445 			unlock_page(old_page);
2446 		}
2447 		page_cache_release(old_page);
2448 	}
2449 	return ret;
2450 oom_free_new:
2451 	page_cache_release(new_page);
2452 oom:
2453 	if (old_page) {
2454 		if (page_mkwrite) {
2455 			unlock_page(old_page);
2456 			page_cache_release(old_page);
2457 		}
2458 		page_cache_release(old_page);
2459 	}
2460 	return VM_FAULT_OOM;
2461 
2462 unwritable_page:
2463 	page_cache_release(old_page);
2464 	return ret;
2465 }
2466 
2467 /*
2468  * Helper functions for unmap_mapping_range().
2469  *
2470  * __ Notes on dropping i_mmap_lock to reduce latency while unmapping __
2471  *
2472  * We have to restart searching the prio_tree whenever we drop the lock,
2473  * since the iterator is only valid while the lock is held, and anyway
2474  * a later vma might be split and reinserted earlier while lock dropped.
2475  *
2476  * The list of nonlinear vmas could be handled more efficiently, using
2477  * a placeholder, but handle it in the same way until a need is shown.
2478  * It is important to search the prio_tree before nonlinear list: a vma
2479  * may become nonlinear and be shifted from prio_tree to nonlinear list
2480  * while the lock is dropped; but never shifted from list to prio_tree.
2481  *
2482  * In order to make forward progress despite restarting the search,
2483  * vm_truncate_count is used to mark a vma as now dealt with, so we can
2484  * quickly skip it next time around.  Since the prio_tree search only
2485  * shows us those vmas affected by unmapping the range in question, we
2486  * can't efficiently keep all vmas in step with mapping->truncate_count:
2487  * so instead reset them all whenever it wraps back to 0 (then go to 1).
2488  * mapping->truncate_count and vma->vm_truncate_count are protected by
2489  * i_mmap_lock.
2490  *
2491  * In order to make forward progress despite repeatedly restarting some
2492  * large vma, note the restart_addr from unmap_vmas when it breaks out:
2493  * and restart from that address when we reach that vma again.  It might
2494  * have been split or merged, shrunk or extended, but never shifted: so
2495  * restart_addr remains valid so long as it remains in the vma's range.
2496  * unmap_mapping_range forces truncate_count to leap over page-aligned
2497  * values so we can save vma's restart_addr in its truncate_count field.
2498  */
2499 #define is_restart_addr(truncate_count) (!((truncate_count) & ~PAGE_MASK))
2500 
2501 static void reset_vma_truncate_counts(struct address_space *mapping)
2502 {
2503 	struct vm_area_struct *vma;
2504 	struct prio_tree_iter iter;
2505 
2506 	vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, 0, ULONG_MAX)
2507 		vma->vm_truncate_count = 0;
2508 	list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list)
2509 		vma->vm_truncate_count = 0;
2510 }
2511 
2512 static int unmap_mapping_range_vma(struct vm_area_struct *vma,
2513 		unsigned long start_addr, unsigned long end_addr,
2514 		struct zap_details *details)
2515 {
2516 	unsigned long restart_addr;
2517 	int need_break;
2518 
2519 	/*
2520 	 * files that support invalidating or truncating portions of the
2521 	 * file from under mmaped areas must have their ->fault function
2522 	 * return a locked page (and set VM_FAULT_LOCKED in the return).
2523 	 * This provides synchronisation against concurrent unmapping here.
2524 	 */
2525 
2526 again:
2527 	restart_addr = vma->vm_truncate_count;
2528 	if (is_restart_addr(restart_addr) && start_addr < restart_addr) {
2529 		start_addr = restart_addr;
2530 		if (start_addr >= end_addr) {
2531 			/* Top of vma has been split off since last time */
2532 			vma->vm_truncate_count = details->truncate_count;
2533 			return 0;
2534 		}
2535 	}
2536 
2537 	restart_addr = zap_page_range(vma, start_addr,
2538 					end_addr - start_addr, details);
2539 	need_break = need_resched() || spin_needbreak(details->i_mmap_lock);
2540 
2541 	if (restart_addr >= end_addr) {
2542 		/* We have now completed this vma: mark it so */
2543 		vma->vm_truncate_count = details->truncate_count;
2544 		if (!need_break)
2545 			return 0;
2546 	} else {
2547 		/* Note restart_addr in vma's truncate_count field */
2548 		vma->vm_truncate_count = restart_addr;
2549 		if (!need_break)
2550 			goto again;
2551 	}
2552 
2553 	spin_unlock(details->i_mmap_lock);
2554 	cond_resched();
2555 	spin_lock(details->i_mmap_lock);
2556 	return -EINTR;
2557 }
2558 
2559 static inline void unmap_mapping_range_tree(struct prio_tree_root *root,
2560 					    struct zap_details *details)
2561 {
2562 	struct vm_area_struct *vma;
2563 	struct prio_tree_iter iter;
2564 	pgoff_t vba, vea, zba, zea;
2565 
2566 restart:
2567 	vma_prio_tree_foreach(vma, &iter, root,
2568 			details->first_index, details->last_index) {
2569 		/* Skip quickly over those we have already dealt with */
2570 		if (vma->vm_truncate_count == details->truncate_count)
2571 			continue;
2572 
2573 		vba = vma->vm_pgoff;
2574 		vea = vba + ((vma->vm_end - vma->vm_start) >> PAGE_SHIFT) - 1;
2575 		/* Assume for now that PAGE_CACHE_SHIFT == PAGE_SHIFT */
2576 		zba = details->first_index;
2577 		if (zba < vba)
2578 			zba = vba;
2579 		zea = details->last_index;
2580 		if (zea > vea)
2581 			zea = vea;
2582 
2583 		if (unmap_mapping_range_vma(vma,
2584 			((zba - vba) << PAGE_SHIFT) + vma->vm_start,
2585 			((zea - vba + 1) << PAGE_SHIFT) + vma->vm_start,
2586 				details) < 0)
2587 			goto restart;
2588 	}
2589 }
2590 
2591 static inline void unmap_mapping_range_list(struct list_head *head,
2592 					    struct zap_details *details)
2593 {
2594 	struct vm_area_struct *vma;
2595 
2596 	/*
2597 	 * In nonlinear VMAs there is no correspondence between virtual address
2598 	 * offset and file offset.  So we must perform an exhaustive search
2599 	 * across *all* the pages in each nonlinear VMA, not just the pages
2600 	 * whose virtual address lies outside the file truncation point.
2601 	 */
2602 restart:
2603 	list_for_each_entry(vma, head, shared.vm_set.list) {
2604 		/* Skip quickly over those we have already dealt with */
2605 		if (vma->vm_truncate_count == details->truncate_count)
2606 			continue;
2607 		details->nonlinear_vma = vma;
2608 		if (unmap_mapping_range_vma(vma, vma->vm_start,
2609 					vma->vm_end, details) < 0)
2610 			goto restart;
2611 	}
2612 }
2613 
2614 /**
2615  * unmap_mapping_range - unmap the portion of all mmaps in the specified address_space corresponding to the specified page range in the underlying file.
2616  * @mapping: the address space containing mmaps to be unmapped.
2617  * @holebegin: byte in first page to unmap, relative to the start of
2618  * the underlying file.  This will be rounded down to a PAGE_SIZE
2619  * boundary.  Note that this is different from truncate_pagecache(), which
2620  * must keep the partial page.  In contrast, we must get rid of
2621  * partial pages.
2622  * @holelen: size of prospective hole in bytes.  This will be rounded
2623  * up to a PAGE_SIZE boundary.  A holelen of zero truncates to the
2624  * end of the file.
2625  * @even_cows: 1 when truncating a file, unmap even private COWed pages;
2626  * but 0 when invalidating pagecache, don't throw away private data.
2627  */
2628 void unmap_mapping_range(struct address_space *mapping,
2629 		loff_t const holebegin, loff_t const holelen, int even_cows)
2630 {
2631 	struct zap_details details;
2632 	pgoff_t hba = holebegin >> PAGE_SHIFT;
2633 	pgoff_t hlen = (holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
2634 
2635 	/* Check for overflow. */
2636 	if (sizeof(holelen) > sizeof(hlen)) {
2637 		long long holeend =
2638 			(holebegin + holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
2639 		if (holeend & ~(long long)ULONG_MAX)
2640 			hlen = ULONG_MAX - hba + 1;
2641 	}
2642 
2643 	details.check_mapping = even_cows? NULL: mapping;
2644 	details.nonlinear_vma = NULL;
2645 	details.first_index = hba;
2646 	details.last_index = hba + hlen - 1;
2647 	if (details.last_index < details.first_index)
2648 		details.last_index = ULONG_MAX;
2649 	details.i_mmap_lock = &mapping->i_mmap_lock;
2650 
2651 	mutex_lock(&mapping->unmap_mutex);
2652 	spin_lock(&mapping->i_mmap_lock);
2653 
2654 	/* Protect against endless unmapping loops */
2655 	mapping->truncate_count++;
2656 	if (unlikely(is_restart_addr(mapping->truncate_count))) {
2657 		if (mapping->truncate_count == 0)
2658 			reset_vma_truncate_counts(mapping);
2659 		mapping->truncate_count++;
2660 	}
2661 	details.truncate_count = mapping->truncate_count;
2662 
2663 	if (unlikely(!prio_tree_empty(&mapping->i_mmap)))
2664 		unmap_mapping_range_tree(&mapping->i_mmap, &details);
2665 	if (unlikely(!list_empty(&mapping->i_mmap_nonlinear)))
2666 		unmap_mapping_range_list(&mapping->i_mmap_nonlinear, &details);
2667 	spin_unlock(&mapping->i_mmap_lock);
2668 	mutex_unlock(&mapping->unmap_mutex);
2669 }
2670 EXPORT_SYMBOL(unmap_mapping_range);
2671 
2672 int vmtruncate_range(struct inode *inode, loff_t offset, loff_t end)
2673 {
2674 	struct address_space *mapping = inode->i_mapping;
2675 
2676 	/*
2677 	 * If the underlying filesystem is not going to provide
2678 	 * a way to truncate a range of blocks (punch a hole) -
2679 	 * we should return failure right now.
2680 	 */
2681 	if (!inode->i_op->truncate_range)
2682 		return -ENOSYS;
2683 
2684 	mutex_lock(&inode->i_mutex);
2685 	down_write(&inode->i_alloc_sem);
2686 	unmap_mapping_range(mapping, offset, (end - offset), 1);
2687 	truncate_inode_pages_range(mapping, offset, end);
2688 	unmap_mapping_range(mapping, offset, (end - offset), 1);
2689 	inode->i_op->truncate_range(inode, offset, end);
2690 	up_write(&inode->i_alloc_sem);
2691 	mutex_unlock(&inode->i_mutex);
2692 
2693 	return 0;
2694 }
2695 
2696 /*
2697  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2698  * but allow concurrent faults), and pte mapped but not yet locked.
2699  * We return with mmap_sem still held, but pte unmapped and unlocked.
2700  */
2701 static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
2702 		unsigned long address, pte_t *page_table, pmd_t *pmd,
2703 		unsigned int flags, pte_t orig_pte)
2704 {
2705 	spinlock_t *ptl;
2706 	struct page *page, *swapcache = NULL;
2707 	swp_entry_t entry;
2708 	pte_t pte;
2709 	int locked;
2710 	struct mem_cgroup *ptr = NULL;
2711 	int exclusive = 0;
2712 	int ret = 0;
2713 
2714 	if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
2715 		goto out;
2716 
2717 	entry = pte_to_swp_entry(orig_pte);
2718 	if (unlikely(non_swap_entry(entry))) {
2719 		if (is_migration_entry(entry)) {
2720 			migration_entry_wait(mm, pmd, address);
2721 		} else if (is_hwpoison_entry(entry)) {
2722 			ret = VM_FAULT_HWPOISON;
2723 		} else {
2724 			print_bad_pte(vma, address, orig_pte, NULL);
2725 			ret = VM_FAULT_SIGBUS;
2726 		}
2727 		goto out;
2728 	}
2729 	delayacct_set_flag(DELAYACCT_PF_SWAPIN);
2730 	page = lookup_swap_cache(entry);
2731 	if (!page) {
2732 		grab_swap_token(mm); /* Contend for token _before_ read-in */
2733 		page = swapin_readahead(entry,
2734 					GFP_HIGHUSER_MOVABLE, vma, address);
2735 		if (!page) {
2736 			/*
2737 			 * Back out if somebody else faulted in this pte
2738 			 * while we released the pte lock.
2739 			 */
2740 			page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2741 			if (likely(pte_same(*page_table, orig_pte)))
2742 				ret = VM_FAULT_OOM;
2743 			delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
2744 			goto unlock;
2745 		}
2746 
2747 		/* Had to read the page from swap area: Major fault */
2748 		ret = VM_FAULT_MAJOR;
2749 		count_vm_event(PGMAJFAULT);
2750 	} else if (PageHWPoison(page)) {
2751 		/*
2752 		 * hwpoisoned dirty swapcache pages are kept for killing
2753 		 * owner processes (which may be unknown at hwpoison time)
2754 		 */
2755 		ret = VM_FAULT_HWPOISON;
2756 		delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
2757 		goto out_release;
2758 	}
2759 
2760 	locked = lock_page_or_retry(page, mm, flags);
2761 	delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
2762 	if (!locked) {
2763 		ret |= VM_FAULT_RETRY;
2764 		goto out_release;
2765 	}
2766 
2767 	/*
2768 	 * Make sure try_to_free_swap or reuse_swap_page or swapoff did not
2769 	 * release the swapcache from under us.  The page pin, and pte_same
2770 	 * test below, are not enough to exclude that.  Even if it is still
2771 	 * swapcache, we need to check that the page's swap has not changed.
2772 	 */
2773 	if (unlikely(!PageSwapCache(page) || page_private(page) != entry.val))
2774 		goto out_page;
2775 
2776 	if (ksm_might_need_to_copy(page, vma, address)) {
2777 		swapcache = page;
2778 		page = ksm_does_need_to_copy(page, vma, address);
2779 
2780 		if (unlikely(!page)) {
2781 			ret = VM_FAULT_OOM;
2782 			page = swapcache;
2783 			swapcache = NULL;
2784 			goto out_page;
2785 		}
2786 	}
2787 
2788 	if (mem_cgroup_try_charge_swapin(mm, page, GFP_KERNEL, &ptr)) {
2789 		ret = VM_FAULT_OOM;
2790 		goto out_page;
2791 	}
2792 
2793 	/*
2794 	 * Back out if somebody else already faulted in this pte.
2795 	 */
2796 	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2797 	if (unlikely(!pte_same(*page_table, orig_pte)))
2798 		goto out_nomap;
2799 
2800 	if (unlikely(!PageUptodate(page))) {
2801 		ret = VM_FAULT_SIGBUS;
2802 		goto out_nomap;
2803 	}
2804 
2805 	/*
2806 	 * The page isn't present yet, go ahead with the fault.
2807 	 *
2808 	 * Be careful about the sequence of operations here.
2809 	 * To get its accounting right, reuse_swap_page() must be called
2810 	 * while the page is counted on swap but not yet in mapcount i.e.
2811 	 * before page_add_anon_rmap() and swap_free(); try_to_free_swap()
2812 	 * must be called after the swap_free(), or it will never succeed.
2813 	 * Because delete_from_swap_page() may be called by reuse_swap_page(),
2814 	 * mem_cgroup_commit_charge_swapin() may not be able to find swp_entry
2815 	 * in page->private. In this case, a record in swap_cgroup  is silently
2816 	 * discarded at swap_free().
2817 	 */
2818 
2819 	inc_mm_counter_fast(mm, MM_ANONPAGES);
2820 	dec_mm_counter_fast(mm, MM_SWAPENTS);
2821 	pte = mk_pte(page, vma->vm_page_prot);
2822 	if ((flags & FAULT_FLAG_WRITE) && reuse_swap_page(page)) {
2823 		pte = maybe_mkwrite(pte_mkdirty(pte), vma);
2824 		flags &= ~FAULT_FLAG_WRITE;
2825 		ret |= VM_FAULT_WRITE;
2826 		exclusive = 1;
2827 	}
2828 	flush_icache_page(vma, page);
2829 	set_pte_at(mm, address, page_table, pte);
2830 	do_page_add_anon_rmap(page, vma, address, exclusive);
2831 	/* It's better to call commit-charge after rmap is established */
2832 	mem_cgroup_commit_charge_swapin(page, ptr);
2833 
2834 	swap_free(entry);
2835 	if (vm_swap_full() || (vma->vm_flags & VM_LOCKED) || PageMlocked(page))
2836 		try_to_free_swap(page);
2837 	unlock_page(page);
2838 	if (swapcache) {
2839 		/*
2840 		 * Hold the lock to avoid the swap entry to be reused
2841 		 * until we take the PT lock for the pte_same() check
2842 		 * (to avoid false positives from pte_same). For
2843 		 * further safety release the lock after the swap_free
2844 		 * so that the swap count won't change under a
2845 		 * parallel locked swapcache.
2846 		 */
2847 		unlock_page(swapcache);
2848 		page_cache_release(swapcache);
2849 	}
2850 
2851 	if (flags & FAULT_FLAG_WRITE) {
2852 		ret |= do_wp_page(mm, vma, address, page_table, pmd, ptl, pte);
2853 		if (ret & VM_FAULT_ERROR)
2854 			ret &= VM_FAULT_ERROR;
2855 		goto out;
2856 	}
2857 
2858 	/* No need to invalidate - it was non-present before */
2859 	update_mmu_cache(vma, address, page_table);
2860 unlock:
2861 	pte_unmap_unlock(page_table, ptl);
2862 out:
2863 	return ret;
2864 out_nomap:
2865 	mem_cgroup_cancel_charge_swapin(ptr);
2866 	pte_unmap_unlock(page_table, ptl);
2867 out_page:
2868 	unlock_page(page);
2869 out_release:
2870 	page_cache_release(page);
2871 	if (swapcache) {
2872 		unlock_page(swapcache);
2873 		page_cache_release(swapcache);
2874 	}
2875 	return ret;
2876 }
2877 
2878 /*
2879  * This is like a special single-page "expand_{down|up}wards()",
2880  * except we must first make sure that 'address{-|+}PAGE_SIZE'
2881  * doesn't hit another vma.
2882  */
2883 static inline int check_stack_guard_page(struct vm_area_struct *vma, unsigned long address)
2884 {
2885 	address &= PAGE_MASK;
2886 	if ((vma->vm_flags & VM_GROWSDOWN) && address == vma->vm_start) {
2887 		struct vm_area_struct *prev = vma->vm_prev;
2888 
2889 		/*
2890 		 * Is there a mapping abutting this one below?
2891 		 *
2892 		 * That's only ok if it's the same stack mapping
2893 		 * that has gotten split..
2894 		 */
2895 		if (prev && prev->vm_end == address)
2896 			return prev->vm_flags & VM_GROWSDOWN ? 0 : -ENOMEM;
2897 
2898 		expand_stack(vma, address - PAGE_SIZE);
2899 	}
2900 	if ((vma->vm_flags & VM_GROWSUP) && address + PAGE_SIZE == vma->vm_end) {
2901 		struct vm_area_struct *next = vma->vm_next;
2902 
2903 		/* As VM_GROWSDOWN but s/below/above/ */
2904 		if (next && next->vm_start == address + PAGE_SIZE)
2905 			return next->vm_flags & VM_GROWSUP ? 0 : -ENOMEM;
2906 
2907 		expand_upwards(vma, address + PAGE_SIZE);
2908 	}
2909 	return 0;
2910 }
2911 
2912 /*
2913  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2914  * but allow concurrent faults), and pte mapped but not yet locked.
2915  * We return with mmap_sem still held, but pte unmapped and unlocked.
2916  */
2917 static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
2918 		unsigned long address, pte_t *page_table, pmd_t *pmd,
2919 		unsigned int flags)
2920 {
2921 	struct page *page;
2922 	spinlock_t *ptl;
2923 	pte_t entry;
2924 
2925 	pte_unmap(page_table);
2926 
2927 	/* Check if we need to add a guard page to the stack */
2928 	if (check_stack_guard_page(vma, address) < 0)
2929 		return VM_FAULT_SIGBUS;
2930 
2931 	/* Use the zero-page for reads */
2932 	if (!(flags & FAULT_FLAG_WRITE)) {
2933 		entry = pte_mkspecial(pfn_pte(my_zero_pfn(address),
2934 						vma->vm_page_prot));
2935 		page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2936 		if (!pte_none(*page_table))
2937 			goto unlock;
2938 		goto setpte;
2939 	}
2940 
2941 	/* Allocate our own private page. */
2942 	if (unlikely(anon_vma_prepare(vma)))
2943 		goto oom;
2944 	page = alloc_zeroed_user_highpage_movable(vma, address);
2945 	if (!page)
2946 		goto oom;
2947 	__SetPageUptodate(page);
2948 
2949 	if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))
2950 		goto oom_free_page;
2951 
2952 	entry = mk_pte(page, vma->vm_page_prot);
2953 	if (vma->vm_flags & VM_WRITE)
2954 		entry = pte_mkwrite(pte_mkdirty(entry));
2955 
2956 	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
2957 	if (!pte_none(*page_table))
2958 		goto release;
2959 
2960 	inc_mm_counter_fast(mm, MM_ANONPAGES);
2961 	page_add_new_anon_rmap(page, vma, address);
2962 setpte:
2963 	set_pte_at(mm, address, page_table, entry);
2964 
2965 	/* No need to invalidate - it was non-present before */
2966 	update_mmu_cache(vma, address, page_table);
2967 unlock:
2968 	pte_unmap_unlock(page_table, ptl);
2969 	return 0;
2970 release:
2971 	mem_cgroup_uncharge_page(page);
2972 	page_cache_release(page);
2973 	goto unlock;
2974 oom_free_page:
2975 	page_cache_release(page);
2976 oom:
2977 	return VM_FAULT_OOM;
2978 }
2979 
2980 /*
2981  * __do_fault() tries to create a new page mapping. It aggressively
2982  * tries to share with existing pages, but makes a separate copy if
2983  * the FAULT_FLAG_WRITE is set in the flags parameter in order to avoid
2984  * the next page fault.
2985  *
2986  * As this is called only for pages that do not currently exist, we
2987  * do not need to flush old virtual caches or the TLB.
2988  *
2989  * We enter with non-exclusive mmap_sem (to exclude vma changes,
2990  * but allow concurrent faults), and pte neither mapped nor locked.
2991  * We return with mmap_sem still held, but pte unmapped and unlocked.
2992  */
2993 static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
2994 		unsigned long address, pmd_t *pmd,
2995 		pgoff_t pgoff, unsigned int flags, pte_t orig_pte)
2996 {
2997 	pte_t *page_table;
2998 	spinlock_t *ptl;
2999 	struct page *page;
3000 	pte_t entry;
3001 	int anon = 0;
3002 	int charged = 0;
3003 	struct page *dirty_page = NULL;
3004 	struct vm_fault vmf;
3005 	int ret;
3006 	int page_mkwrite = 0;
3007 
3008 	vmf.virtual_address = (void __user *)(address & PAGE_MASK);
3009 	vmf.pgoff = pgoff;
3010 	vmf.flags = flags;
3011 	vmf.page = NULL;
3012 
3013 	ret = vma->vm_ops->fault(vma, &vmf);
3014 	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE |
3015 			    VM_FAULT_RETRY)))
3016 		return ret;
3017 
3018 	if (unlikely(PageHWPoison(vmf.page))) {
3019 		if (ret & VM_FAULT_LOCKED)
3020 			unlock_page(vmf.page);
3021 		return VM_FAULT_HWPOISON;
3022 	}
3023 
3024 	/*
3025 	 * For consistency in subsequent calls, make the faulted page always
3026 	 * locked.
3027 	 */
3028 	if (unlikely(!(ret & VM_FAULT_LOCKED)))
3029 		lock_page(vmf.page);
3030 	else
3031 		VM_BUG_ON(!PageLocked(vmf.page));
3032 
3033 	/*
3034 	 * Should we do an early C-O-W break?
3035 	 */
3036 	page = vmf.page;
3037 	if (flags & FAULT_FLAG_WRITE) {
3038 		if (!(vma->vm_flags & VM_SHARED)) {
3039 			anon = 1;
3040 			if (unlikely(anon_vma_prepare(vma))) {
3041 				ret = VM_FAULT_OOM;
3042 				goto out;
3043 			}
3044 			page = alloc_page_vma(GFP_HIGHUSER_MOVABLE,
3045 						vma, address);
3046 			if (!page) {
3047 				ret = VM_FAULT_OOM;
3048 				goto out;
3049 			}
3050 			if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL)) {
3051 				ret = VM_FAULT_OOM;
3052 				page_cache_release(page);
3053 				goto out;
3054 			}
3055 			charged = 1;
3056 			copy_user_highpage(page, vmf.page, address, vma);
3057 			__SetPageUptodate(page);
3058 		} else {
3059 			/*
3060 			 * If the page will be shareable, see if the backing
3061 			 * address space wants to know that the page is about
3062 			 * to become writable
3063 			 */
3064 			if (vma->vm_ops->page_mkwrite) {
3065 				int tmp;
3066 
3067 				unlock_page(page);
3068 				vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
3069 				tmp = vma->vm_ops->page_mkwrite(vma, &vmf);
3070 				if (unlikely(tmp &
3071 					  (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
3072 					ret = tmp;
3073 					goto unwritable_page;
3074 				}
3075 				if (unlikely(!(tmp & VM_FAULT_LOCKED))) {
3076 					lock_page(page);
3077 					if (!page->mapping) {
3078 						ret = 0; /* retry the fault */
3079 						unlock_page(page);
3080 						goto unwritable_page;
3081 					}
3082 				} else
3083 					VM_BUG_ON(!PageLocked(page));
3084 				page_mkwrite = 1;
3085 			}
3086 		}
3087 
3088 	}
3089 
3090 	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
3091 
3092 	/*
3093 	 * This silly early PAGE_DIRTY setting removes a race
3094 	 * due to the bad i386 page protection. But it's valid
3095 	 * for other architectures too.
3096 	 *
3097 	 * Note that if FAULT_FLAG_WRITE is set, we either now have
3098 	 * an exclusive copy of the page, or this is a shared mapping,
3099 	 * so we can make it writable and dirty to avoid having to
3100 	 * handle that later.
3101 	 */
3102 	/* Only go through if we didn't race with anybody else... */
3103 	if (likely(pte_same(*page_table, orig_pte))) {
3104 		flush_icache_page(vma, page);
3105 		entry = mk_pte(page, vma->vm_page_prot);
3106 		if (flags & FAULT_FLAG_WRITE)
3107 			entry = maybe_mkwrite(pte_mkdirty(entry), vma);
3108 		if (anon) {
3109 			inc_mm_counter_fast(mm, MM_ANONPAGES);
3110 			page_add_new_anon_rmap(page, vma, address);
3111 		} else {
3112 			inc_mm_counter_fast(mm, MM_FILEPAGES);
3113 			page_add_file_rmap(page);
3114 			if (flags & FAULT_FLAG_WRITE) {
3115 				dirty_page = page;
3116 				get_page(dirty_page);
3117 			}
3118 		}
3119 		set_pte_at(mm, address, page_table, entry);
3120 
3121 		/* no need to invalidate: a not-present page won't be cached */
3122 		update_mmu_cache(vma, address, page_table);
3123 	} else {
3124 		if (charged)
3125 			mem_cgroup_uncharge_page(page);
3126 		if (anon)
3127 			page_cache_release(page);
3128 		else
3129 			anon = 1; /* no anon but release faulted_page */
3130 	}
3131 
3132 	pte_unmap_unlock(page_table, ptl);
3133 
3134 out:
3135 	if (dirty_page) {
3136 		struct address_space *mapping = page->mapping;
3137 
3138 		if (set_page_dirty(dirty_page))
3139 			page_mkwrite = 1;
3140 		unlock_page(dirty_page);
3141 		put_page(dirty_page);
3142 		if (page_mkwrite && mapping) {
3143 			/*
3144 			 * Some device drivers do not set page.mapping but still
3145 			 * dirty their pages
3146 			 */
3147 			balance_dirty_pages_ratelimited(mapping);
3148 		}
3149 
3150 		/* file_update_time outside page_lock */
3151 		if (vma->vm_file)
3152 			file_update_time(vma->vm_file);
3153 	} else {
3154 		unlock_page(vmf.page);
3155 		if (anon)
3156 			page_cache_release(vmf.page);
3157 	}
3158 
3159 	return ret;
3160 
3161 unwritable_page:
3162 	page_cache_release(page);
3163 	return ret;
3164 }
3165 
3166 static int do_linear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3167 		unsigned long address, pte_t *page_table, pmd_t *pmd,
3168 		unsigned int flags, pte_t orig_pte)
3169 {
3170 	pgoff_t pgoff = (((address & PAGE_MASK)
3171 			- vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
3172 
3173 	pte_unmap(page_table);
3174 	return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
3175 }
3176 
3177 /*
3178  * Fault of a previously existing named mapping. Repopulate the pte
3179  * from the encoded file_pte if possible. This enables swappable
3180  * nonlinear vmas.
3181  *
3182  * We enter with non-exclusive mmap_sem (to exclude vma changes,
3183  * but allow concurrent faults), and pte mapped but not yet locked.
3184  * We return with mmap_sem still held, but pte unmapped and unlocked.
3185  */
3186 static int do_nonlinear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3187 		unsigned long address, pte_t *page_table, pmd_t *pmd,
3188 		unsigned int flags, pte_t orig_pte)
3189 {
3190 	pgoff_t pgoff;
3191 
3192 	flags |= FAULT_FLAG_NONLINEAR;
3193 
3194 	if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
3195 		return 0;
3196 
3197 	if (unlikely(!(vma->vm_flags & VM_NONLINEAR))) {
3198 		/*
3199 		 * Page table corrupted: show pte and kill process.
3200 		 */
3201 		print_bad_pte(vma, address, orig_pte, NULL);
3202 		return VM_FAULT_SIGBUS;
3203 	}
3204 
3205 	pgoff = pte_to_pgoff(orig_pte);
3206 	return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
3207 }
3208 
3209 /*
3210  * These routines also need to handle stuff like marking pages dirty
3211  * and/or accessed for architectures that don't do it in hardware (most
3212  * RISC architectures).  The early dirtying is also good on the i386.
3213  *
3214  * There is also a hook called "update_mmu_cache()" that architectures
3215  * with external mmu caches can use to update those (ie the Sparc or
3216  * PowerPC hashed page tables that act as extended TLBs).
3217  *
3218  * We enter with non-exclusive mmap_sem (to exclude vma changes,
3219  * but allow concurrent faults), and pte mapped but not yet locked.
3220  * We return with mmap_sem still held, but pte unmapped and unlocked.
3221  */
3222 int handle_pte_fault(struct mm_struct *mm,
3223 		     struct vm_area_struct *vma, unsigned long address,
3224 		     pte_t *pte, pmd_t *pmd, unsigned int flags)
3225 {
3226 	pte_t entry;
3227 	spinlock_t *ptl;
3228 
3229 	entry = *pte;
3230 	if (!pte_present(entry)) {
3231 		if (pte_none(entry)) {
3232 			if (vma->vm_ops) {
3233 				if (likely(vma->vm_ops->fault))
3234 					return do_linear_fault(mm, vma, address,
3235 						pte, pmd, flags, entry);
3236 			}
3237 			return do_anonymous_page(mm, vma, address,
3238 						 pte, pmd, flags);
3239 		}
3240 		if (pte_file(entry))
3241 			return do_nonlinear_fault(mm, vma, address,
3242 					pte, pmd, flags, entry);
3243 		return do_swap_page(mm, vma, address,
3244 					pte, pmd, flags, entry);
3245 	}
3246 
3247 	ptl = pte_lockptr(mm, pmd);
3248 	spin_lock(ptl);
3249 	if (unlikely(!pte_same(*pte, entry)))
3250 		goto unlock;
3251 	if (flags & FAULT_FLAG_WRITE) {
3252 		if (!pte_write(entry))
3253 			return do_wp_page(mm, vma, address,
3254 					pte, pmd, ptl, entry);
3255 		entry = pte_mkdirty(entry);
3256 	}
3257 	entry = pte_mkyoung(entry);
3258 	if (ptep_set_access_flags(vma, address, pte, entry, flags & FAULT_FLAG_WRITE)) {
3259 		update_mmu_cache(vma, address, pte);
3260 	} else {
3261 		/*
3262 		 * This is needed only for protection faults but the arch code
3263 		 * is not yet telling us if this is a protection fault or not.
3264 		 * This still avoids useless tlb flushes for .text page faults
3265 		 * with threads.
3266 		 */
3267 		if (flags & FAULT_FLAG_WRITE)
3268 			flush_tlb_fix_spurious_fault(vma, address);
3269 	}
3270 unlock:
3271 	pte_unmap_unlock(pte, ptl);
3272 	return 0;
3273 }
3274 
3275 /*
3276  * By the time we get here, we already hold the mm semaphore
3277  */
3278 int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
3279 		unsigned long address, unsigned int flags)
3280 {
3281 	pgd_t *pgd;
3282 	pud_t *pud;
3283 	pmd_t *pmd;
3284 	pte_t *pte;
3285 
3286 	__set_current_state(TASK_RUNNING);
3287 
3288 	count_vm_event(PGFAULT);
3289 
3290 	/* do counter updates before entering really critical section. */
3291 	check_sync_rss_stat(current);
3292 
3293 	if (unlikely(is_vm_hugetlb_page(vma)))
3294 		return hugetlb_fault(mm, vma, address, flags);
3295 
3296 	pgd = pgd_offset(mm, address);
3297 	pud = pud_alloc(mm, pgd, address);
3298 	if (!pud)
3299 		return VM_FAULT_OOM;
3300 	pmd = pmd_alloc(mm, pud, address);
3301 	if (!pmd)
3302 		return VM_FAULT_OOM;
3303 	if (pmd_none(*pmd) && transparent_hugepage_enabled(vma)) {
3304 		if (!vma->vm_ops)
3305 			return do_huge_pmd_anonymous_page(mm, vma, address,
3306 							  pmd, flags);
3307 	} else {
3308 		pmd_t orig_pmd = *pmd;
3309 		barrier();
3310 		if (pmd_trans_huge(orig_pmd)) {
3311 			if (flags & FAULT_FLAG_WRITE &&
3312 			    !pmd_write(orig_pmd) &&
3313 			    !pmd_trans_splitting(orig_pmd))
3314 				return do_huge_pmd_wp_page(mm, vma, address,
3315 							   pmd, orig_pmd);
3316 			return 0;
3317 		}
3318 	}
3319 
3320 	/*
3321 	 * Use __pte_alloc instead of pte_alloc_map, because we can't
3322 	 * run pte_offset_map on the pmd, if an huge pmd could
3323 	 * materialize from under us from a different thread.
3324 	 */
3325 	if (unlikely(__pte_alloc(mm, vma, pmd, address)))
3326 		return VM_FAULT_OOM;
3327 	/* if an huge pmd materialized from under us just retry later */
3328 	if (unlikely(pmd_trans_huge(*pmd)))
3329 		return 0;
3330 	/*
3331 	 * A regular pmd is established and it can't morph into a huge pmd
3332 	 * from under us anymore at this point because we hold the mmap_sem
3333 	 * read mode and khugepaged takes it in write mode. So now it's
3334 	 * safe to run pte_offset_map().
3335 	 */
3336 	pte = pte_offset_map(pmd, address);
3337 
3338 	return handle_pte_fault(mm, vma, address, pte, pmd, flags);
3339 }
3340 
3341 #ifndef __PAGETABLE_PUD_FOLDED
3342 /*
3343  * Allocate page upper directory.
3344  * We've already handled the fast-path in-line.
3345  */
3346 int __pud_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address)
3347 {
3348 	pud_t *new = pud_alloc_one(mm, address);
3349 	if (!new)
3350 		return -ENOMEM;
3351 
3352 	smp_wmb(); /* See comment in __pte_alloc */
3353 
3354 	spin_lock(&mm->page_table_lock);
3355 	if (pgd_present(*pgd))		/* Another has populated it */
3356 		pud_free(mm, new);
3357 	else
3358 		pgd_populate(mm, pgd, new);
3359 	spin_unlock(&mm->page_table_lock);
3360 	return 0;
3361 }
3362 #endif /* __PAGETABLE_PUD_FOLDED */
3363 
3364 #ifndef __PAGETABLE_PMD_FOLDED
3365 /*
3366  * Allocate page middle directory.
3367  * We've already handled the fast-path in-line.
3368  */
3369 int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address)
3370 {
3371 	pmd_t *new = pmd_alloc_one(mm, address);
3372 	if (!new)
3373 		return -ENOMEM;
3374 
3375 	smp_wmb(); /* See comment in __pte_alloc */
3376 
3377 	spin_lock(&mm->page_table_lock);
3378 #ifndef __ARCH_HAS_4LEVEL_HACK
3379 	if (pud_present(*pud))		/* Another has populated it */
3380 		pmd_free(mm, new);
3381 	else
3382 		pud_populate(mm, pud, new);
3383 #else
3384 	if (pgd_present(*pud))		/* Another has populated it */
3385 		pmd_free(mm, new);
3386 	else
3387 		pgd_populate(mm, pud, new);
3388 #endif /* __ARCH_HAS_4LEVEL_HACK */
3389 	spin_unlock(&mm->page_table_lock);
3390 	return 0;
3391 }
3392 #endif /* __PAGETABLE_PMD_FOLDED */
3393 
3394 int make_pages_present(unsigned long addr, unsigned long end)
3395 {
3396 	int ret, len, write;
3397 	struct vm_area_struct * vma;
3398 
3399 	vma = find_vma(current->mm, addr);
3400 	if (!vma)
3401 		return -ENOMEM;
3402 	/*
3403 	 * We want to touch writable mappings with a write fault in order
3404 	 * to break COW, except for shared mappings because these don't COW
3405 	 * and we would not want to dirty them for nothing.
3406 	 */
3407 	write = (vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE;
3408 	BUG_ON(addr >= end);
3409 	BUG_ON(end > vma->vm_end);
3410 	len = DIV_ROUND_UP(end, PAGE_SIZE) - addr/PAGE_SIZE;
3411 	ret = get_user_pages(current, current->mm, addr,
3412 			len, write, 0, NULL, NULL);
3413 	if (ret < 0)
3414 		return ret;
3415 	return ret == len ? 0 : -EFAULT;
3416 }
3417 
3418 #if !defined(__HAVE_ARCH_GATE_AREA)
3419 
3420 #if defined(AT_SYSINFO_EHDR)
3421 static struct vm_area_struct gate_vma;
3422 
3423 static int __init gate_vma_init(void)
3424 {
3425 	gate_vma.vm_mm = NULL;
3426 	gate_vma.vm_start = FIXADDR_USER_START;
3427 	gate_vma.vm_end = FIXADDR_USER_END;
3428 	gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
3429 	gate_vma.vm_page_prot = __P101;
3430 	/*
3431 	 * Make sure the vDSO gets into every core dump.
3432 	 * Dumping its contents makes post-mortem fully interpretable later
3433 	 * without matching up the same kernel and hardware config to see
3434 	 * what PC values meant.
3435 	 */
3436 	gate_vma.vm_flags |= VM_ALWAYSDUMP;
3437 	return 0;
3438 }
3439 __initcall(gate_vma_init);
3440 #endif
3441 
3442 struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
3443 {
3444 #ifdef AT_SYSINFO_EHDR
3445 	return &gate_vma;
3446 #else
3447 	return NULL;
3448 #endif
3449 }
3450 
3451 int in_gate_area_no_task(unsigned long addr)
3452 {
3453 #ifdef AT_SYSINFO_EHDR
3454 	if ((addr >= FIXADDR_USER_START) && (addr < FIXADDR_USER_END))
3455 		return 1;
3456 #endif
3457 	return 0;
3458 }
3459 
3460 #endif	/* __HAVE_ARCH_GATE_AREA */
3461 
3462 static int __follow_pte(struct mm_struct *mm, unsigned long address,
3463 		pte_t **ptepp, spinlock_t **ptlp)
3464 {
3465 	pgd_t *pgd;
3466 	pud_t *pud;
3467 	pmd_t *pmd;
3468 	pte_t *ptep;
3469 
3470 	pgd = pgd_offset(mm, address);
3471 	if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
3472 		goto out;
3473 
3474 	pud = pud_offset(pgd, address);
3475 	if (pud_none(*pud) || unlikely(pud_bad(*pud)))
3476 		goto out;
3477 
3478 	pmd = pmd_offset(pud, address);
3479 	VM_BUG_ON(pmd_trans_huge(*pmd));
3480 	if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
3481 		goto out;
3482 
3483 	/* We cannot handle huge page PFN maps. Luckily they don't exist. */
3484 	if (pmd_huge(*pmd))
3485 		goto out;
3486 
3487 	ptep = pte_offset_map_lock(mm, pmd, address, ptlp);
3488 	if (!ptep)
3489 		goto out;
3490 	if (!pte_present(*ptep))
3491 		goto unlock;
3492 	*ptepp = ptep;
3493 	return 0;
3494 unlock:
3495 	pte_unmap_unlock(ptep, *ptlp);
3496 out:
3497 	return -EINVAL;
3498 }
3499 
3500 static inline int follow_pte(struct mm_struct *mm, unsigned long address,
3501 			     pte_t **ptepp, spinlock_t **ptlp)
3502 {
3503 	int res;
3504 
3505 	/* (void) is needed to make gcc happy */
3506 	(void) __cond_lock(*ptlp,
3507 			   !(res = __follow_pte(mm, address, ptepp, ptlp)));
3508 	return res;
3509 }
3510 
3511 /**
3512  * follow_pfn - look up PFN at a user virtual address
3513  * @vma: memory mapping
3514  * @address: user virtual address
3515  * @pfn: location to store found PFN
3516  *
3517  * Only IO mappings and raw PFN mappings are allowed.
3518  *
3519  * Returns zero and the pfn at @pfn on success, -ve otherwise.
3520  */
3521 int follow_pfn(struct vm_area_struct *vma, unsigned long address,
3522 	unsigned long *pfn)
3523 {
3524 	int ret = -EINVAL;
3525 	spinlock_t *ptl;
3526 	pte_t *ptep;
3527 
3528 	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
3529 		return ret;
3530 
3531 	ret = follow_pte(vma->vm_mm, address, &ptep, &ptl);
3532 	if (ret)
3533 		return ret;
3534 	*pfn = pte_pfn(*ptep);
3535 	pte_unmap_unlock(ptep, ptl);
3536 	return 0;
3537 }
3538 EXPORT_SYMBOL(follow_pfn);
3539 
3540 #ifdef CONFIG_HAVE_IOREMAP_PROT
3541 int follow_phys(struct vm_area_struct *vma,
3542 		unsigned long address, unsigned int flags,
3543 		unsigned long *prot, resource_size_t *phys)
3544 {
3545 	int ret = -EINVAL;
3546 	pte_t *ptep, pte;
3547 	spinlock_t *ptl;
3548 
3549 	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
3550 		goto out;
3551 
3552 	if (follow_pte(vma->vm_mm, address, &ptep, &ptl))
3553 		goto out;
3554 	pte = *ptep;
3555 
3556 	if ((flags & FOLL_WRITE) && !pte_write(pte))
3557 		goto unlock;
3558 
3559 	*prot = pgprot_val(pte_pgprot(pte));
3560 	*phys = (resource_size_t)pte_pfn(pte) << PAGE_SHIFT;
3561 
3562 	ret = 0;
3563 unlock:
3564 	pte_unmap_unlock(ptep, ptl);
3565 out:
3566 	return ret;
3567 }
3568 
3569 int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
3570 			void *buf, int len, int write)
3571 {
3572 	resource_size_t phys_addr;
3573 	unsigned long prot = 0;
3574 	void __iomem *maddr;
3575 	int offset = addr & (PAGE_SIZE-1);
3576 
3577 	if (follow_phys(vma, addr, write, &prot, &phys_addr))
3578 		return -EINVAL;
3579 
3580 	maddr = ioremap_prot(phys_addr, PAGE_SIZE, prot);
3581 	if (write)
3582 		memcpy_toio(maddr + offset, buf, len);
3583 	else
3584 		memcpy_fromio(buf, maddr + offset, len);
3585 	iounmap(maddr);
3586 
3587 	return len;
3588 }
3589 #endif
3590 
3591 /*
3592  * Access another process' address space.
3593  * Source/target buffer must be kernel space,
3594  * Do not walk the page table directly, use get_user_pages
3595  */
3596 int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
3597 {
3598 	struct mm_struct *mm;
3599 	struct vm_area_struct *vma;
3600 	void *old_buf = buf;
3601 
3602 	mm = get_task_mm(tsk);
3603 	if (!mm)
3604 		return 0;
3605 
3606 	down_read(&mm->mmap_sem);
3607 	/* ignore errors, just check how much was successfully transferred */
3608 	while (len) {
3609 		int bytes, ret, offset;
3610 		void *maddr;
3611 		struct page *page = NULL;
3612 
3613 		ret = get_user_pages(tsk, mm, addr, 1,
3614 				write, 1, &page, &vma);
3615 		if (ret <= 0) {
3616 			/*
3617 			 * Check if this is a VM_IO | VM_PFNMAP VMA, which
3618 			 * we can access using slightly different code.
3619 			 */
3620 #ifdef CONFIG_HAVE_IOREMAP_PROT
3621 			vma = find_vma(mm, addr);
3622 			if (!vma)
3623 				break;
3624 			if (vma->vm_ops && vma->vm_ops->access)
3625 				ret = vma->vm_ops->access(vma, addr, buf,
3626 							  len, write);
3627 			if (ret <= 0)
3628 #endif
3629 				break;
3630 			bytes = ret;
3631 		} else {
3632 			bytes = len;
3633 			offset = addr & (PAGE_SIZE-1);
3634 			if (bytes > PAGE_SIZE-offset)
3635 				bytes = PAGE_SIZE-offset;
3636 
3637 			maddr = kmap(page);
3638 			if (write) {
3639 				copy_to_user_page(vma, page, addr,
3640 						  maddr + offset, buf, bytes);
3641 				set_page_dirty_lock(page);
3642 			} else {
3643 				copy_from_user_page(vma, page, addr,
3644 						    buf, maddr + offset, bytes);
3645 			}
3646 			kunmap(page);
3647 			page_cache_release(page);
3648 		}
3649 		len -= bytes;
3650 		buf += bytes;
3651 		addr += bytes;
3652 	}
3653 	up_read(&mm->mmap_sem);
3654 	mmput(mm);
3655 
3656 	return buf - old_buf;
3657 }
3658 
3659 /*
3660  * Print the name of a VMA.
3661  */
3662 void print_vma_addr(char *prefix, unsigned long ip)
3663 {
3664 	struct mm_struct *mm = current->mm;
3665 	struct vm_area_struct *vma;
3666 
3667 	/*
3668 	 * Do not print if we are in atomic
3669 	 * contexts (in exception stacks, etc.):
3670 	 */
3671 	if (preempt_count())
3672 		return;
3673 
3674 	down_read(&mm->mmap_sem);
3675 	vma = find_vma(mm, ip);
3676 	if (vma && vma->vm_file) {
3677 		struct file *f = vma->vm_file;
3678 		char *buf = (char *)__get_free_page(GFP_KERNEL);
3679 		if (buf) {
3680 			char *p, *s;
3681 
3682 			p = d_path(&f->f_path, buf, PAGE_SIZE);
3683 			if (IS_ERR(p))
3684 				p = "?";
3685 			s = strrchr(p, '/');
3686 			if (s)
3687 				p = s+1;
3688 			printk("%s%s[%lx+%lx]", prefix, p,
3689 					vma->vm_start,
3690 					vma->vm_end - vma->vm_start);
3691 			free_page((unsigned long)buf);
3692 		}
3693 	}
3694 	up_read(&current->mm->mmap_sem);
3695 }
3696 
3697 #ifdef CONFIG_PROVE_LOCKING
3698 void might_fault(void)
3699 {
3700 	/*
3701 	 * Some code (nfs/sunrpc) uses socket ops on kernel memory while
3702 	 * holding the mmap_sem, this is safe because kernel memory doesn't
3703 	 * get paged out, therefore we'll never actually fault, and the
3704 	 * below annotations will generate false positives.
3705 	 */
3706 	if (segment_eq(get_fs(), KERNEL_DS))
3707 		return;
3708 
3709 	might_sleep();
3710 	/*
3711 	 * it would be nicer only to annotate paths which are not under
3712 	 * pagefault_disable, however that requires a larger audit and
3713 	 * providing helpers like get_user_atomic.
3714 	 */
3715 	if (!in_atomic() && current->mm)
3716 		might_lock_read(&current->mm->mmap_sem);
3717 }
3718 EXPORT_SYMBOL(might_fault);
3719 #endif
3720 
3721 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HUGETLBFS)
3722 static void clear_gigantic_page(struct page *page,
3723 				unsigned long addr,
3724 				unsigned int pages_per_huge_page)
3725 {
3726 	int i;
3727 	struct page *p = page;
3728 
3729 	might_sleep();
3730 	for (i = 0; i < pages_per_huge_page;
3731 	     i++, p = mem_map_next(p, page, i)) {
3732 		cond_resched();
3733 		clear_user_highpage(p, addr + i * PAGE_SIZE);
3734 	}
3735 }
3736 void clear_huge_page(struct page *page,
3737 		     unsigned long addr, unsigned int pages_per_huge_page)
3738 {
3739 	int i;
3740 
3741 	if (unlikely(pages_per_huge_page > MAX_ORDER_NR_PAGES)) {
3742 		clear_gigantic_page(page, addr, pages_per_huge_page);
3743 		return;
3744 	}
3745 
3746 	might_sleep();
3747 	for (i = 0; i < pages_per_huge_page; i++) {
3748 		cond_resched();
3749 		clear_user_highpage(page + i, addr + i * PAGE_SIZE);
3750 	}
3751 }
3752 
3753 static void copy_user_gigantic_page(struct page *dst, struct page *src,
3754 				    unsigned long addr,
3755 				    struct vm_area_struct *vma,
3756 				    unsigned int pages_per_huge_page)
3757 {
3758 	int i;
3759 	struct page *dst_base = dst;
3760 	struct page *src_base = src;
3761 
3762 	for (i = 0; i < pages_per_huge_page; ) {
3763 		cond_resched();
3764 		copy_user_highpage(dst, src, addr + i*PAGE_SIZE, vma);
3765 
3766 		i++;
3767 		dst = mem_map_next(dst, dst_base, i);
3768 		src = mem_map_next(src, src_base, i);
3769 	}
3770 }
3771 
3772 void copy_user_huge_page(struct page *dst, struct page *src,
3773 			 unsigned long addr, struct vm_area_struct *vma,
3774 			 unsigned int pages_per_huge_page)
3775 {
3776 	int i;
3777 
3778 	if (unlikely(pages_per_huge_page > MAX_ORDER_NR_PAGES)) {
3779 		copy_user_gigantic_page(dst, src, addr, vma,
3780 					pages_per_huge_page);
3781 		return;
3782 	}
3783 
3784 	might_sleep();
3785 	for (i = 0; i < pages_per_huge_page; i++) {
3786 		cond_resched();
3787 		copy_user_highpage(dst + i, src + i, addr + i*PAGE_SIZE, vma);
3788 	}
3789 }
3790 #endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */
3791