1#ifndef _LINUX_RMAP_H
2#define _LINUX_RMAP_H
3/*
4 * Declarations for Reverse Mapping functions in mm/rmap.c
5 */
6
7#include <linux/list.h>
8#include <linux/slab.h>
9#include <linux/mm.h>
10#include <linux/rwsem.h>
11#include <linux/memcontrol.h>
12
13/*
14 * The anon_vma heads a list of private "related" vmas, to scan if
15 * an anonymous page pointing to this anon_vma needs to be unmapped:
16 * the vmas on the list will be related by forking, or by splitting.
17 *
18 * Since vmas come and go as they are split and merged (particularly
19 * in mprotect), the mapping field of an anonymous page cannot point
20 * directly to a vma: instead it points to an anon_vma, on whose list
21 * the related vmas can be easily linked or unlinked.
22 *
23 * After unlinking the last vma on the list, we must garbage collect
24 * the anon_vma object itself: we're guaranteed no page can be
25 * pointing to this anon_vma once its vma list is empty.
26 */
27struct anon_vma {
28	struct anon_vma *root;		/* Root of this anon_vma tree */
29	struct rw_semaphore rwsem;	/* W: modification, R: walking the list */
30	/*
31	 * The refcount is taken on an anon_vma when there is no
32	 * guarantee that the vma of page tables will exist for
33	 * the duration of the operation. A caller that takes
34	 * the reference is responsible for clearing up the
35	 * anon_vma if they are the last user on release
36	 */
37	atomic_t refcount;
38
39	/*
40	 * Count of child anon_vmas and VMAs which points to this anon_vma.
41	 *
42	 * This counter is used for making decision about reusing anon_vma
43	 * instead of forking new one. See comments in function anon_vma_clone.
44	 */
45	unsigned degree;
46
47	struct anon_vma *parent;	/* Parent of this anon_vma */
48
49	/*
50	 * NOTE: the LSB of the rb_root.rb_node is set by
51	 * mm_take_all_locks() _after_ taking the above lock. So the
52	 * rb_root must only be read/written after taking the above lock
53	 * to be sure to see a valid next pointer. The LSB bit itself
54	 * is serialized by a system wide lock only visible to
55	 * mm_take_all_locks() (mm_all_locks_mutex).
56	 */
57	struct rb_root rb_root;	/* Interval tree of private "related" vmas */
58};
59
60/*
61 * The copy-on-write semantics of fork mean that an anon_vma
62 * can become associated with multiple processes. Furthermore,
63 * each child process will have its own anon_vma, where new
64 * pages for that process are instantiated.
65 *
66 * This structure allows us to find the anon_vmas associated
67 * with a VMA, or the VMAs associated with an anon_vma.
68 * The "same_vma" list contains the anon_vma_chains linking
69 * all the anon_vmas associated with this VMA.
70 * The "rb" field indexes on an interval tree the anon_vma_chains
71 * which link all the VMAs associated with this anon_vma.
72 */
73struct anon_vma_chain {
74	struct vm_area_struct *vma;
75	struct anon_vma *anon_vma;
76	struct list_head same_vma;   /* locked by mmap_sem & page_table_lock */
77	struct rb_node rb;			/* locked by anon_vma->rwsem */
78	unsigned long rb_subtree_last;
79#ifdef CONFIG_DEBUG_VM_RB
80	unsigned long cached_vma_start, cached_vma_last;
81#endif
82};
83
84enum ttu_flags {
85	TTU_UNMAP = 1,			/* unmap mode */
86	TTU_MIGRATION = 2,		/* migration mode */
87	TTU_MUNLOCK = 4,		/* munlock mode */
88
89	TTU_IGNORE_MLOCK = (1 << 8),	/* ignore mlock */
90	TTU_IGNORE_ACCESS = (1 << 9),	/* don't age */
91	TTU_IGNORE_HWPOISON = (1 << 10),/* corrupted page is recoverable */
92};
93
94#ifdef CONFIG_MMU
95static inline void get_anon_vma(struct anon_vma *anon_vma)
96{
97	atomic_inc(&anon_vma->refcount);
98}
99
100void __put_anon_vma(struct anon_vma *anon_vma);
101
102static inline void put_anon_vma(struct anon_vma *anon_vma)
103{
104	if (atomic_dec_and_test(&anon_vma->refcount))
105		__put_anon_vma(anon_vma);
106}
107
108static inline void anon_vma_lock_write(struct anon_vma *anon_vma)
109{
110	down_write(&anon_vma->root->rwsem);
111}
112
113static inline void anon_vma_unlock_write(struct anon_vma *anon_vma)
114{
115	up_write(&anon_vma->root->rwsem);
116}
117
118static inline void anon_vma_lock_read(struct anon_vma *anon_vma)
119{
120	down_read(&anon_vma->root->rwsem);
121}
122
123static inline void anon_vma_unlock_read(struct anon_vma *anon_vma)
124{
125	up_read(&anon_vma->root->rwsem);
126}
127
128
129/*
130 * anon_vma helper functions.
131 */
132void anon_vma_init(void);	/* create anon_vma_cachep */
133int  anon_vma_prepare(struct vm_area_struct *);
134void unlink_anon_vmas(struct vm_area_struct *);
135int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *);
136int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *);
137
138static inline void anon_vma_merge(struct vm_area_struct *vma,
139				  struct vm_area_struct *next)
140{
141	VM_BUG_ON_VMA(vma->anon_vma != next->anon_vma, vma);
142	unlink_anon_vmas(next);
143}
144
145struct anon_vma *page_get_anon_vma(struct page *page);
146
147/*
148 * rmap interfaces called when adding or removing pte of page
149 */
150void page_move_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
151void page_add_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
152void do_page_add_anon_rmap(struct page *, struct vm_area_struct *,
153			   unsigned long, int);
154void page_add_new_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
155void page_add_file_rmap(struct page *);
156void page_remove_rmap(struct page *);
157
158void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *,
159			    unsigned long);
160void hugepage_add_new_anon_rmap(struct page *, struct vm_area_struct *,
161				unsigned long);
162
163static inline void page_dup_rmap(struct page *page)
164{
165	atomic_inc(&page->_mapcount);
166}
167
168/*
169 * Called from mm/vmscan.c to handle paging out
170 */
171int page_referenced(struct page *, int is_locked,
172			struct mem_cgroup *memcg, unsigned long *vm_flags);
173
174#define TTU_ACTION(x) ((x) & TTU_ACTION_MASK)
175
176int try_to_unmap(struct page *, enum ttu_flags flags);
177
178/*
179 * Used by uprobes to replace a userspace page safely
180 */
181pte_t *__page_check_address(struct page *, struct mm_struct *,
182				unsigned long, spinlock_t **, int);
183
184static inline pte_t *page_check_address(struct page *page, struct mm_struct *mm,
185					unsigned long address,
186					spinlock_t **ptlp, int sync)
187{
188	pte_t *ptep;
189
190	__cond_lock(*ptlp, ptep = __page_check_address(page, mm, address,
191						       ptlp, sync));
192	return ptep;
193}
194
195/*
196 * Used by swapoff to help locate where page is expected in vma.
197 */
198unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
199
200/*
201 * Cleans the PTEs of shared mappings.
202 * (and since clean PTEs should also be readonly, write protects them too)
203 *
204 * returns the number of cleaned PTEs.
205 */
206int page_mkclean(struct page *);
207
208/*
209 * called in munlock()/munmap() path to check for other vmas holding
210 * the page mlocked.
211 */
212int try_to_munlock(struct page *);
213
214/*
215 * Called by memory-failure.c to kill processes.
216 */
217struct anon_vma *page_lock_anon_vma_read(struct page *page);
218void page_unlock_anon_vma_read(struct anon_vma *anon_vma);
219int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
220
221/*
222 * rmap_walk_control: To control rmap traversing for specific needs
223 *
224 * arg: passed to rmap_one() and invalid_vma()
225 * rmap_one: executed on each vma where page is mapped
226 * done: for checking traversing termination condition
227 * anon_lock: for getting anon_lock by optimized way rather than default
228 * invalid_vma: for skipping uninterested vma
229 */
230struct rmap_walk_control {
231	void *arg;
232	int (*rmap_one)(struct page *page, struct vm_area_struct *vma,
233					unsigned long addr, void *arg);
234	int (*done)(struct page *page);
235	struct anon_vma *(*anon_lock)(struct page *page);
236	bool (*invalid_vma)(struct vm_area_struct *vma, void *arg);
237};
238
239int rmap_walk(struct page *page, struct rmap_walk_control *rwc);
240
241#else	/* !CONFIG_MMU */
242
243#define anon_vma_init()		do {} while (0)
244#define anon_vma_prepare(vma)	(0)
245#define anon_vma_link(vma)	do {} while (0)
246
247static inline int page_referenced(struct page *page, int is_locked,
248				  struct mem_cgroup *memcg,
249				  unsigned long *vm_flags)
250{
251	*vm_flags = 0;
252	return 0;
253}
254
255#define try_to_unmap(page, refs) SWAP_FAIL
256
257static inline int page_mkclean(struct page *page)
258{
259	return 0;
260}
261
262
263#endif	/* CONFIG_MMU */
264
265/*
266 * Return values of try_to_unmap
267 */
268#define SWAP_SUCCESS	0
269#define SWAP_AGAIN	1
270#define SWAP_FAIL	2
271#define SWAP_MLOCK	3
272
273#endif	/* _LINUX_RMAP_H */
274