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TOMOYO Linux Cross Reference
Linux/include/linux/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/rwsem.h>
 11 #include <linux/memcontrol.h>
 12 #include <linux/highmem.h>
 13 
 14 /*
 15  * The anon_vma heads a list of private "related" vmas, to scan if
 16  * an anonymous page pointing to this anon_vma needs to be unmapped:
 17  * the vmas on the list will be related by forking, or by splitting.
 18  *
 19  * Since vmas come and go as they are split and merged (particularly
 20  * in mprotect), the mapping field of an anonymous page cannot point
 21  * directly to a vma: instead it points to an anon_vma, on whose list
 22  * the related vmas can be easily linked or unlinked.
 23  *
 24  * After unlinking the last vma on the list, we must garbage collect
 25  * the anon_vma object itself: we're guaranteed no page can be
 26  * pointing to this anon_vma once its vma list is empty.
 27  */
 28 struct anon_vma {
 29         struct anon_vma *root;          /* Root of this anon_vma tree */
 30         struct rw_semaphore rwsem;      /* W: modification, R: walking the list */
 31         /*
 32          * The refcount is taken on an anon_vma when there is no
 33          * guarantee that the vma of page tables will exist for
 34          * the duration of the operation. A caller that takes
 35          * the reference is responsible for clearing up the
 36          * anon_vma if they are the last user on release
 37          */
 38         atomic_t refcount;
 39 
 40         /*
 41          * Count of child anon_vmas and VMAs which points to this anon_vma.
 42          *
 43          * This counter is used for making decision about reusing anon_vma
 44          * instead of forking new one. See comments in function anon_vma_clone.
 45          */
 46         unsigned degree;
 47 
 48         struct anon_vma *parent;        /* Parent of this anon_vma */
 49 
 50         /*
 51          * NOTE: the LSB of the rb_root.rb_node is set by
 52          * mm_take_all_locks() _after_ taking the above lock. So the
 53          * rb_root must only be read/written after taking the above lock
 54          * to be sure to see a valid next pointer. The LSB bit itself
 55          * is serialized by a system wide lock only visible to
 56          * mm_take_all_locks() (mm_all_locks_mutex).
 57          */
 58         struct rb_root rb_root; /* Interval tree of private "related" vmas */
 59 };
 60 
 61 /*
 62  * The copy-on-write semantics of fork mean that an anon_vma
 63  * can become associated with multiple processes. Furthermore,
 64  * each child process will have its own anon_vma, where new
 65  * pages for that process are instantiated.
 66  *
 67  * This structure allows us to find the anon_vmas associated
 68  * with a VMA, or the VMAs associated with an anon_vma.
 69  * The "same_vma" list contains the anon_vma_chains linking
 70  * all the anon_vmas associated with this VMA.
 71  * The "rb" field indexes on an interval tree the anon_vma_chains
 72  * which link all the VMAs associated with this anon_vma.
 73  */
 74 struct anon_vma_chain {
 75         struct vm_area_struct *vma;
 76         struct anon_vma *anon_vma;
 77         struct list_head same_vma;   /* locked by mmap_sem & page_table_lock */
 78         struct rb_node rb;                      /* locked by anon_vma->rwsem */
 79         unsigned long rb_subtree_last;
 80 #ifdef CONFIG_DEBUG_VM_RB
 81         unsigned long cached_vma_start, cached_vma_last;
 82 #endif
 83 };
 84 
 85 enum ttu_flags {
 86         TTU_MIGRATION           = 0x1,  /* migration mode */
 87         TTU_MUNLOCK             = 0x2,  /* munlock mode */
 88 
 89         TTU_SPLIT_HUGE_PMD      = 0x4,  /* split huge PMD if any */
 90         TTU_IGNORE_MLOCK        = 0x8,  /* ignore mlock */
 91         TTU_IGNORE_ACCESS       = 0x10, /* don't age */
 92         TTU_IGNORE_HWPOISON     = 0x20, /* corrupted page is recoverable */
 93         TTU_BATCH_FLUSH         = 0x40, /* Batch TLB flushes where possible
 94                                          * and caller guarantees they will
 95                                          * do a final flush if necessary */
 96         TTU_RMAP_LOCKED         = 0x80  /* do not grab rmap lock:
 97                                          * caller holds it */
 98 };
 99 
100 #ifdef CONFIG_MMU
101 static inline void get_anon_vma(struct anon_vma *anon_vma)
102 {
103         atomic_inc(&anon_vma->refcount);
104 }
105 
106 void __put_anon_vma(struct anon_vma *anon_vma);
107 
108 static inline void put_anon_vma(struct anon_vma *anon_vma)
109 {
110         if (atomic_dec_and_test(&anon_vma->refcount))
111                 __put_anon_vma(anon_vma);
112 }
113 
114 static inline void anon_vma_lock_write(struct anon_vma *anon_vma)
115 {
116         down_write(&anon_vma->root->rwsem);
117 }
118 
119 static inline void anon_vma_unlock_write(struct anon_vma *anon_vma)
120 {
121         up_write(&anon_vma->root->rwsem);
122 }
123 
124 static inline void anon_vma_lock_read(struct anon_vma *anon_vma)
125 {
126         down_read(&anon_vma->root->rwsem);
127 }
128 
129 static inline void anon_vma_unlock_read(struct anon_vma *anon_vma)
130 {
131         up_read(&anon_vma->root->rwsem);
132 }
133 
134 
135 /*
136  * anon_vma helper functions.
137  */
138 void anon_vma_init(void);       /* create anon_vma_cachep */
139 int  __anon_vma_prepare(struct vm_area_struct *);
140 void unlink_anon_vmas(struct vm_area_struct *);
141 int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *);
142 int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *);
143 
144 static inline int anon_vma_prepare(struct vm_area_struct *vma)
145 {
146         if (likely(vma->anon_vma))
147                 return 0;
148 
149         return __anon_vma_prepare(vma);
150 }
151 
152 static inline void anon_vma_merge(struct vm_area_struct *vma,
153                                   struct vm_area_struct *next)
154 {
155         VM_BUG_ON_VMA(vma->anon_vma != next->anon_vma, vma);
156         unlink_anon_vmas(next);
157 }
158 
159 struct anon_vma *page_get_anon_vma(struct page *page);
160 
161 /* bitflags for do_page_add_anon_rmap() */
162 #define RMAP_EXCLUSIVE 0x01
163 #define RMAP_COMPOUND 0x02
164 
165 /*
166  * rmap interfaces called when adding or removing pte of page
167  */
168 void page_move_anon_rmap(struct page *, struct vm_area_struct *);
169 void page_add_anon_rmap(struct page *, struct vm_area_struct *,
170                 unsigned long, bool);
171 void do_page_add_anon_rmap(struct page *, struct vm_area_struct *,
172                            unsigned long, int);
173 void page_add_new_anon_rmap(struct page *, struct vm_area_struct *,
174                 unsigned long, bool);
175 void page_add_file_rmap(struct page *, bool);
176 void page_remove_rmap(struct page *, bool);
177 
178 void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *,
179                             unsigned long);
180 void hugepage_add_new_anon_rmap(struct page *, struct vm_area_struct *,
181                                 unsigned long);
182 
183 static inline void page_dup_rmap(struct page *page, bool compound)
184 {
185         atomic_inc(compound ? compound_mapcount_ptr(page) : &page->_mapcount);
186 }
187 
188 /*
189  * Called from mm/vmscan.c to handle paging out
190  */
191 int page_referenced(struct page *, int is_locked,
192                         struct mem_cgroup *memcg, unsigned long *vm_flags);
193 
194 bool try_to_unmap(struct page *, enum ttu_flags flags);
195 
196 /* Avoid racy checks */
197 #define PVMW_SYNC               (1 << 0)
198 /* Look for migarion entries rather than present PTEs */
199 #define PVMW_MIGRATION          (1 << 1)
200 
201 struct page_vma_mapped_walk {
202         struct page *page;
203         struct vm_area_struct *vma;
204         unsigned long address;
205         pmd_t *pmd;
206         pte_t *pte;
207         spinlock_t *ptl;
208         unsigned int flags;
209 };
210 
211 static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
212 {
213         if (pvmw->pte)
214                 pte_unmap(pvmw->pte);
215         if (pvmw->ptl)
216                 spin_unlock(pvmw->ptl);
217 }
218 
219 bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw);
220 
221 /*
222  * Used by swapoff to help locate where page is expected in vma.
223  */
224 unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
225 
226 /*
227  * Cleans the PTEs of shared mappings.
228  * (and since clean PTEs should also be readonly, write protects them too)
229  *
230  * returns the number of cleaned PTEs.
231  */
232 int page_mkclean(struct page *);
233 
234 /*
235  * called in munlock()/munmap() path to check for other vmas holding
236  * the page mlocked.
237  */
238 void try_to_munlock(struct page *);
239 
240 void remove_migration_ptes(struct page *old, struct page *new, bool locked);
241 
242 /*
243  * Called by memory-failure.c to kill processes.
244  */
245 struct anon_vma *page_lock_anon_vma_read(struct page *page);
246 void page_unlock_anon_vma_read(struct anon_vma *anon_vma);
247 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
248 
249 /*
250  * rmap_walk_control: To control rmap traversing for specific needs
251  *
252  * arg: passed to rmap_one() and invalid_vma()
253  * rmap_one: executed on each vma where page is mapped
254  * done: for checking traversing termination condition
255  * anon_lock: for getting anon_lock by optimized way rather than default
256  * invalid_vma: for skipping uninterested vma
257  */
258 struct rmap_walk_control {
259         void *arg;
260         /*
261          * Return false if page table scanning in rmap_walk should be stopped.
262          * Otherwise, return true.
263          */
264         bool (*rmap_one)(struct page *page, struct vm_area_struct *vma,
265                                         unsigned long addr, void *arg);
266         int (*done)(struct page *page);
267         struct anon_vma *(*anon_lock)(struct page *page);
268         bool (*invalid_vma)(struct vm_area_struct *vma, void *arg);
269 };
270 
271 void rmap_walk(struct page *page, struct rmap_walk_control *rwc);
272 void rmap_walk_locked(struct page *page, struct rmap_walk_control *rwc);
273 
274 #else   /* !CONFIG_MMU */
275 
276 #define anon_vma_init()         do {} while (0)
277 #define anon_vma_prepare(vma)   (0)
278 #define anon_vma_link(vma)      do {} while (0)
279 
280 static inline int page_referenced(struct page *page, int is_locked,
281                                   struct mem_cgroup *memcg,
282                                   unsigned long *vm_flags)
283 {
284         *vm_flags = 0;
285         return 0;
286 }
287 
288 #define try_to_unmap(page, refs) false
289 
290 static inline int page_mkclean(struct page *page)
291 {
292         return 0;
293 }
294 
295 
296 #endif  /* CONFIG_MMU */
297 
298 #endif  /* _LINUX_RMAP_H */
299 

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