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rmap.h
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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/mutex.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  */
27 struct anon_vma {
28  struct anon_vma *root; /* Root of this anon_vma tree */
29  struct mutex mutex; /* Serialize access to vma 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  */
38 
39  /*
40  * NOTE: the LSB of the rb_root.rb_node is set by
41  * mm_take_all_locks() _after_ taking the above lock. So the
42  * rb_root must only be read/written after taking the above lock
43  * to be sure to see a valid next pointer. The LSB bit itself
44  * is serialized by a system wide lock only visible to
45  * mm_take_all_locks() (mm_all_locks_mutex).
46  */
47  struct rb_root rb_root; /* Interval tree of private "related" vmas */
48 };
49 
50 /*
51  * The copy-on-write semantics of fork mean that an anon_vma
52  * can become associated with multiple processes. Furthermore,
53  * each child process will have its own anon_vma, where new
54  * pages for that process are instantiated.
55  *
56  * This structure allows us to find the anon_vmas associated
57  * with a VMA, or the VMAs associated with an anon_vma.
58  * The "same_vma" list contains the anon_vma_chains linking
59  * all the anon_vmas associated with this VMA.
60  * The "rb" field indexes on an interval tree the anon_vma_chains
61  * which link all the VMAs associated with this anon_vma.
62  */
65  struct anon_vma *anon_vma;
66  struct list_head same_vma; /* locked by mmap_sem & page_table_lock */
67  struct rb_node rb; /* locked by anon_vma->mutex */
68  unsigned long rb_subtree_last;
69 #ifdef CONFIG_DEBUG_VM_RB
70  unsigned long cached_vma_start, cached_vma_last;
71 #endif
72 };
73 
74 enum ttu_flags {
75  TTU_UNMAP = 0, /* unmap mode */
76  TTU_MIGRATION = 1, /* migration mode */
77  TTU_MUNLOCK = 2, /* munlock mode */
79 
80  TTU_IGNORE_MLOCK = (1 << 8), /* ignore mlock */
81  TTU_IGNORE_ACCESS = (1 << 9), /* don't age */
82  TTU_IGNORE_HWPOISON = (1 << 10),/* corrupted page is recoverable */
83 };
84 
85 #ifdef CONFIG_MMU
86 static inline void get_anon_vma(struct anon_vma *anon_vma)
87 {
88  atomic_inc(&anon_vma->refcount);
89 }
90 
91 void __put_anon_vma(struct anon_vma *anon_vma);
92 
93 static inline void put_anon_vma(struct anon_vma *anon_vma)
94 {
95  if (atomic_dec_and_test(&anon_vma->refcount))
96  __put_anon_vma(anon_vma);
97 }
98 
99 static inline struct anon_vma *page_anon_vma(struct page *page)
100 {
101  if (((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) !=
102  PAGE_MAPPING_ANON)
103  return NULL;
104  return page_rmapping(page);
105 }
106 
107 static inline void vma_lock_anon_vma(struct vm_area_struct *vma)
108 {
109  struct anon_vma *anon_vma = vma->anon_vma;
110  if (anon_vma)
111  mutex_lock(&anon_vma->root->mutex);
112 }
113 
114 static inline void vma_unlock_anon_vma(struct vm_area_struct *vma)
115 {
116  struct anon_vma *anon_vma = vma->anon_vma;
117  if (anon_vma)
118  mutex_unlock(&anon_vma->root->mutex);
119 }
120 
121 static inline void anon_vma_lock(struct anon_vma *anon_vma)
122 {
123  mutex_lock(&anon_vma->root->mutex);
124 }
125 
126 static inline void anon_vma_unlock(struct anon_vma *anon_vma)
127 {
128  mutex_unlock(&anon_vma->root->mutex);
129 }
130 
131 /*
132  * anon_vma helper functions.
133  */
134 void anon_vma_init(void); /* create anon_vma_cachep */
135 int anon_vma_prepare(struct vm_area_struct *);
136 void unlink_anon_vmas(struct vm_area_struct *);
137 int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *);
138 int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *);
139 
140 static inline void anon_vma_merge(struct vm_area_struct *vma,
141  struct vm_area_struct *next)
142 {
143  VM_BUG_ON(vma->anon_vma != next->anon_vma);
144  unlink_anon_vmas(next);
145 }
146 
147 struct anon_vma *page_get_anon_vma(struct page *page);
148 
149 /*
150  * rmap interfaces called when adding or removing pte of page
151  */
152 void page_move_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
153 void page_add_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
154 void do_page_add_anon_rmap(struct page *, struct vm_area_struct *,
155  unsigned long, int);
156 void page_add_new_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
157 void page_add_file_rmap(struct page *);
158 void page_remove_rmap(struct page *);
159 
160 void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *,
161  unsigned long);
162 void hugepage_add_new_anon_rmap(struct page *, struct vm_area_struct *,
163  unsigned long);
164 
165 static inline void page_dup_rmap(struct page *page)
166 {
167  atomic_inc(&page->_mapcount);
168 }
169 
170 /*
171  * Called from mm/vmscan.c to handle paging out
172  */
173 int page_referenced(struct page *, int is_locked,
174  struct mem_cgroup *memcg, unsigned long *vm_flags);
175 int page_referenced_one(struct page *, struct vm_area_struct *,
176  unsigned long address, unsigned int *mapcount, unsigned long *vm_flags);
177 
178 #define TTU_ACTION(x) ((x) & TTU_ACTION_MASK)
179 
180 int try_to_unmap(struct page *, enum ttu_flags flags);
181 int try_to_unmap_one(struct page *, struct vm_area_struct *,
182  unsigned long address, enum ttu_flags flags);
183 
184 /*
185  * Called from mm/filemap_xip.c to unmap empty zero page
186  */
187 pte_t *__page_check_address(struct page *, struct mm_struct *,
188  unsigned long, spinlock_t **, int);
189 
190 static inline pte_t *page_check_address(struct page *page, struct mm_struct *mm,
191  unsigned long address,
192  spinlock_t **ptlp, int sync)
193 {
194  pte_t *ptep;
195 
196  __cond_lock(*ptlp, ptep = __page_check_address(page, mm, address,
197  ptlp, sync));
198  return ptep;
199 }
200 
201 /*
202  * Used by swapoff to help locate where page is expected in vma.
203  */
204 unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
205 
206 /*
207  * Cleans the PTEs of shared mappings.
208  * (and since clean PTEs should also be readonly, write protects them too)
209  *
210  * returns the number of cleaned PTEs.
211  */
212 int page_mkclean(struct page *);
213 
214 /*
215  * called in munlock()/munmap() path to check for other vmas holding
216  * the page mlocked.
217  */
218 int try_to_munlock(struct page *);
219 
220 /*
221  * Called by memory-failure.c to kill processes.
222  */
223 struct anon_vma *page_lock_anon_vma(struct page *page);
224 void page_unlock_anon_vma(struct anon_vma *anon_vma);
225 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
226 
227 /*
228  * Called by migrate.c to remove migration ptes, but might be used more later.
229  */
230 int rmap_walk(struct page *page, int (*rmap_one)(struct page *,
231  struct vm_area_struct *, unsigned long, void *), void *arg);
232 
233 #else /* !CONFIG_MMU */
234 
235 #define anon_vma_init() do {} while (0)
236 #define anon_vma_prepare(vma) (0)
237 #define anon_vma_link(vma) do {} while (0)
238 
239 static inline int page_referenced(struct page *page, int is_locked,
240  struct mem_cgroup *memcg,
241  unsigned long *vm_flags)
242 {
243  *vm_flags = 0;
244  return 0;
245 }
246 
247 #define try_to_unmap(page, refs) SWAP_FAIL
248 
249 static inline int page_mkclean(struct page *page)
250 {
251  return 0;
252 }
253 
254 
255 #endif /* CONFIG_MMU */
256 
257 /*
258  * Return values of try_to_unmap
259  */
260 #define SWAP_SUCCESS 0
261 #define SWAP_AGAIN 1
262 #define SWAP_FAIL 2
263 #define SWAP_MLOCK 3
264 
265 #endif /* _LINUX_RMAP_H */