aboutsummaryrefslogtreecommitdiff
path: root/include/linux/rmap.h
blob: 2462458708cd03530ab8040f6b525d0afcd62acf (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
#ifndef _LINUX_RMAP_H
#define _LINUX_RMAP_H
/*
 * Declarations for Reverse Mapping functions in mm/rmap.c
 */

#include <linux/list.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/rwsem.h>
#include <linux/memcontrol.h>

/*
 * The anon_vma heads a list of private "related" vmas, to scan if
 * an anonymous page pointing to this anon_vma needs to be unmapped:
 * the vmas on the list will be related by forking, or by splitting.
 *
 * Since vmas come and go as they are split and merged (particularly
 * in mprotect), the mapping field of an anonymous page cannot point
 * directly to a vma: instead it points to an anon_vma, on whose list
 * the related vmas can be easily linked or unlinked.
 *
 * After unlinking the last vma on the list, we must garbage collect
 * the anon_vma object itself: we're guaranteed no page can be
 * pointing to this anon_vma once its vma list is empty.
 */
struct anon_vma {
	struct anon_vma *root;		/* Root of this anon_vma tree */
	struct rw_semaphore rwsem;	/* W: modification, R: walking the list */
	/*
	 * The refcount is taken on an anon_vma when there is no
	 * guarantee that the vma of page tables will exist for
	 * the duration of the operation. A caller that takes
	 * the reference is responsible for clearing up the
	 * anon_vma if they are the last user on release
	 */
	atomic_t refcount;

	/*
	 * NOTE: the LSB of the rb_root.rb_node is set by
	 * mm_take_all_locks() _after_ taking the above lock. So the
	 * rb_root must only be read/written after taking the above lock
	 * to be sure to see a valid next pointer. The LSB bit itself
	 * is serialized by a system wide lock only visible to
	 * mm_take_all_locks() (mm_all_locks_mutex).
	 */
	struct rb_root rb_root;	/* Interval tree of private "related" vmas */
};

/*
 * The copy-on-write semantics of fork mean that an anon_vma
 * can become associated with multiple processes. Furthermore,
 * each child process will have its own anon_vma, where new
 * pages for that process are instantiated.
 *
 * This structure allows us to find the anon_vmas associated
 * with a VMA, or the VMAs associated with an anon_vma.
 * The "same_vma" list contains the anon_vma_chains linking
 * all the anon_vmas associated with this VMA.
 * The "rb" field indexes on an interval tree the anon_vma_chains
 * which link all the VMAs associated with this anon_vma.
 */
struct anon_vma_chain {
	struct vm_area_struct *vma;
	struct anon_vma *anon_vma;
	struct list_head same_vma;   /* locked by mmap_sem & page_table_lock */
	struct rb_node rb;			/* locked by anon_vma->rwsem */
	unsigned long rb_subtree_last;
#ifdef CONFIG_DEBUG_VM_RB
	unsigned long cached_vma_start, cached_vma_last;
#endif
};

enum ttu_flags {
	TTU_UNMAP = 0,			/* unmap mode */
	TTU_MIGRATION = 1,		/* migration mode */
	TTU_MUNLOCK = 2,		/* munlock mode */
	TTU_ACTION_MASK = 0xff,

	TTU_IGNORE_MLOCK = (1 << 8),	/* ignore mlock */
	TTU_IGNORE_ACCESS = (1 << 9),	/* don't age */
	TTU_IGNORE_HWPOISON = (1 << 10),/* corrupted page is recoverable */
};

#ifdef CONFIG_MMU
static inline void get_anon_vma(struct anon_vma *anon_vma)
{
	atomic_inc(&anon_vma->refcount);
}

void __put_anon_vma(struct anon_vma *anon_vma);

static inline void put_anon_vma(struct anon_vma *anon_vma)
{
	if (atomic_dec_and_test(&anon_vma->refcount))
		__put_anon_vma(anon_vma);
}

static inline struct anon_vma *page_anon_vma(struct page *page)
{
	if (((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) !=
					    PAGE_MAPPING_ANON)
		return NULL;
	return page_rmapping(page);
}

static inline void vma_lock_anon_vma(struct vm_area_struct *vma)
{
	struct anon_vma *anon_vma = vma->anon_vma;
	if (anon_vma)
		down_write(&anon_vma->root->rwsem);
}

static inline void vma_unlock_anon_vma(struct vm_area_struct *vma)
{
	struct anon_vma *anon_vma = vma->anon_vma;
	if (anon_vma)
		up_write(&anon_vma->root->rwsem);
}

static inline void anon_vma_lock_write(struct anon_vma *anon_vma)
{
	down_write(&anon_vma->root->rwsem);
}

static inline void anon_vma_unlock_write(struct anon_vma *anon_vma)
{
	up_write(&anon_vma->root->rwsem);
}

static inline void anon_vma_lock_read(struct anon_vma *anon_vma)
{
	down_read(&anon_vma->root->rwsem);
}

static inline void anon_vma_unlock_read(struct anon_vma *anon_vma)
{
	up_read(&anon_vma->root->rwsem);
}


/*
 * anon_vma helper functions.
 */
void anon_vma_init(void);	/* create anon_vma_cachep */
int  anon_vma_prepare(struct vm_area_struct *);
void unlink_anon_vmas(struct vm_area_struct *);
int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *);
int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *);

static inline void anon_vma_merge(struct vm_area_struct *vma,
				  struct vm_area_struct *next)
{
	VM_BUG_ON(vma->anon_vma != next->anon_vma);
	unlink_anon_vmas(next);
}

struct anon_vma *page_get_anon_vma(struct page *page);

/*
 * rmap interfaces called when adding or removing pte of page
 */
void page_move_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
void page_add_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
void do_page_add_anon_rmap(struct page *, struct vm_area_struct *,
			   unsigned long, int);
void page_add_new_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
void page_add_file_rmap(struct page *);
void page_remove_rmap(struct page *);

void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *,
			    unsigned long);
void hugepage_add_new_anon_rmap(struct page *, struct vm_area_struct *,
				unsigned long);

static inline void page_dup_rmap(struct page *page)
{
	atomic_inc(&page->_mapcount);
}

/*
 * Called from mm/vmscan.c to handle paging out
 */
int page_referenced(struct page *, int is_locked,
			struct mem_cgroup *memcg, unsigned long *vm_flags);
int page_referenced_one(struct page *, struct vm_area_struct *,
	unsigned long address, unsigned int *mapcount, unsigned long *vm_flags);

#define TTU_ACTION(x) ((x) & TTU_ACTION_MASK)

int try_to_unmap(struct page *, enum ttu_flags flags);
int try_to_unmap_one(struct page *, struct vm_area_struct *,
			unsigned long address, void *arg);

/*
 * Called from mm/filemap_xip.c to unmap empty zero page
 */
pte_t *__page_check_address(struct page *, struct mm_struct *,
				unsigned long, spinlock_t **, int);

static inline pte_t *page_check_address(struct page *page, struct mm_struct *mm,
					unsigned long address,
					spinlock_t **ptlp, int sync)
{
	pte_t *ptep;

	__cond_lock(*ptlp, ptep = __page_check_address(page, mm, address,
						       ptlp, sync));
	return ptep;
}

/*
 * Used by swapoff to help locate where page is expected in vma.
 */
unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);

/*
 * Cleans the PTEs of shared mappings.
 * (and since clean PTEs should also be readonly, write protects them too)
 *
 * returns the number of cleaned PTEs.
 */
int page_mkclean(struct page *);

/*
 * called in munlock()/munmap() path to check for other vmas holding
 * the page mlocked.
 */
int try_to_munlock(struct page *);

/*
 * Called by memory-failure.c to kill processes.
 */
struct anon_vma *page_lock_anon_vma_read(struct page *page);
void page_unlock_anon_vma_read(struct anon_vma *anon_vma);
int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);

/*
 * rmap_walk_control: To control rmap traversing for specific needs
 *
 * arg: passed to rmap_one() and invalid_vma()
 * rmap_one: executed on each vma where page is mapped
 * done: for checking traversing termination condition
 * file_nonlinear: for handling file nonlinear mapping
 * anon_lock: for getting anon_lock by optimized way rather than default
 * invalid_vma: for skipping uninterested vma
 */
struct rmap_walk_control {
	void *arg;
	int (*rmap_one)(struct page *page, struct vm_area_struct *vma,
					unsigned long addr, void *arg);
	int (*done)(struct page *page);
	int (*file_nonlinear)(struct page *, struct address_space *,
					struct vm_area_struct *vma);
	struct anon_vma *(*anon_lock)(struct page *page);
	bool (*invalid_vma)(struct vm_area_struct *vma, void *arg);
};

int rmap_walk(struct page *page, struct rmap_walk_control *rwc);

#else	/* !CONFIG_MMU */

#define anon_vma_init()		do {} while (0)
#define anon_vma_prepare(vma)	(0)
#define anon_vma_link(vma)	do {} while (0)

static inline int page_referenced(struct page *page, int is_locked,
				  struct mem_cgroup *memcg,
				  unsigned long *vm_flags)
{
	*vm_flags = 0;
	return 0;
}

#define try_to_unmap(page, refs) SWAP_FAIL

static inline int page_mkclean(struct page *page)
{
	return 0;
}


#endif	/* CONFIG_MMU */

/*
 * Return values of try_to_unmap
 */
#define SWAP_SUCCESS	0
#define SWAP_AGAIN	1
#define SWAP_FAIL	2
#define SWAP_MLOCK	3

#endif	/* _LINUX_RMAP_H */