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TOMOYO Linux Cross Reference
Linux/include/linux/rmap.h

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  1 /* SPDX-License-Identifier: GPL-2.0 */
  2 #ifndef _LINUX_RMAP_H
  3 #define _LINUX_RMAP_H
  4 /*
  5  * Declarations for Reverse Mapping functions in mm/rmap.c
  6  */
  7 
  8 #include <linux/list.h>
  9 #include <linux/slab.h>
 10 #include <linux/mm.h>
 11 #include <linux/rwsem.h>
 12 #include <linux/memcontrol.h>
 13 #include <linux/highmem.h>
 14 
 15 /*
 16  * The anon_vma heads a list of private "related" vmas, to scan if
 17  * an anonymous page pointing to this anon_vma needs to be unmapped:
 18  * the vmas on the list will be related by forking, or by splitting.
 19  *
 20  * Since vmas come and go as they are split and merged (particularly
 21  * in mprotect), the mapping field of an anonymous page cannot point
 22  * directly to a vma: instead it points to an anon_vma, on whose list
 23  * the related vmas can be easily linked or unlinked.
 24  *
 25  * After unlinking the last vma on the list, we must garbage collect
 26  * the anon_vma object itself: we're guaranteed no page can be
 27  * pointing to this anon_vma once its vma list is empty.
 28  */
 29 struct anon_vma {
 30         struct anon_vma *root;          /* Root of this anon_vma tree */
 31         struct rw_semaphore rwsem;      /* W: modification, R: walking the list */
 32         /*
 33          * The refcount is taken on an anon_vma when there is no
 34          * guarantee that the vma of page tables will exist for
 35          * the duration of the operation. A caller that takes
 36          * the reference is responsible for clearing up the
 37          * anon_vma if they are the last user on release
 38          */
 39         atomic_t refcount;
 40 
 41         /*
 42          * Count of child anon_vmas and VMAs which points to this anon_vma.
 43          *
 44          * This counter is used for making decision about reusing anon_vma
 45          * instead of forking new one. See comments in function anon_vma_clone.
 46          */
 47         unsigned degree;
 48 
 49         struct anon_vma *parent;        /* Parent of this anon_vma */
 50 
 51         /*
 52          * NOTE: the LSB of the rb_root.rb_node is set by
 53          * mm_take_all_locks() _after_ taking the above lock. So the
 54          * rb_root must only be read/written after taking the above lock
 55          * to be sure to see a valid next pointer. The LSB bit itself
 56          * is serialized by a system wide lock only visible to
 57          * mm_take_all_locks() (mm_all_locks_mutex).
 58          */
 59 
 60         /* Interval tree of private "related" vmas */
 61         struct rb_root_cached rb_root;
 62 };
 63 
 64 /*
 65  * The copy-on-write semantics of fork mean that an anon_vma
 66  * can become associated with multiple processes. Furthermore,
 67  * each child process will have its own anon_vma, where new
 68  * pages for that process are instantiated.
 69  *
 70  * This structure allows us to find the anon_vmas associated
 71  * with a VMA, or the VMAs associated with an anon_vma.
 72  * The "same_vma" list contains the anon_vma_chains linking
 73  * all the anon_vmas associated with this VMA.
 74  * The "rb" field indexes on an interval tree the anon_vma_chains
 75  * which link all the VMAs associated with this anon_vma.
 76  */
 77 struct anon_vma_chain {
 78         struct vm_area_struct *vma;
 79         struct anon_vma *anon_vma;
 80         struct list_head same_vma;   /* locked by mmap_sem & page_table_lock */
 81         struct rb_node rb;                      /* locked by anon_vma->rwsem */
 82         unsigned long rb_subtree_last;
 83 #ifdef CONFIG_DEBUG_VM_RB
 84         unsigned long cached_vma_start, cached_vma_last;
 85 #endif
 86 };
 87 
 88 enum ttu_flags {
 89         TTU_MIGRATION           = 0x1,  /* migration mode */
 90         TTU_MUNLOCK             = 0x2,  /* munlock mode */
 91 
 92         TTU_SPLIT_HUGE_PMD      = 0x4,  /* split huge PMD if any */
 93         TTU_IGNORE_MLOCK        = 0x8,  /* ignore mlock */
 94         TTU_IGNORE_ACCESS       = 0x10, /* don't age */
 95         TTU_IGNORE_HWPOISON     = 0x20, /* corrupted page is recoverable */
 96         TTU_BATCH_FLUSH         = 0x40, /* Batch TLB flushes where possible
 97                                          * and caller guarantees they will
 98                                          * do a final flush if necessary */
 99         TTU_RMAP_LOCKED         = 0x80, /* do not grab rmap lock:
100                                          * caller holds it */
101         TTU_SPLIT_FREEZE        = 0x100,                /* freeze pte under splitting thp */
102 };
103 
104 #ifdef CONFIG_MMU
105 static inline void get_anon_vma(struct anon_vma *anon_vma)
106 {
107         atomic_inc(&anon_vma->refcount);
108 }
109 
110 void __put_anon_vma(struct anon_vma *anon_vma);
111 
112 static inline void put_anon_vma(struct anon_vma *anon_vma)
113 {
114         if (atomic_dec_and_test(&anon_vma->refcount))
115                 __put_anon_vma(anon_vma);
116 }
117 
118 static inline void anon_vma_lock_write(struct anon_vma *anon_vma)
119 {
120         down_write(&anon_vma->root->rwsem);
121 }
122 
123 static inline void anon_vma_unlock_write(struct anon_vma *anon_vma)
124 {
125         up_write(&anon_vma->root->rwsem);
126 }
127 
128 static inline void anon_vma_lock_read(struct anon_vma *anon_vma)
129 {
130         down_read(&anon_vma->root->rwsem);
131 }
132 
133 static inline void anon_vma_unlock_read(struct anon_vma *anon_vma)
134 {
135         up_read(&anon_vma->root->rwsem);
136 }
137 
138 
139 /*
140  * anon_vma helper functions.
141  */
142 void anon_vma_init(void);       /* create anon_vma_cachep */
143 int  __anon_vma_prepare(struct vm_area_struct *);
144 void unlink_anon_vmas(struct vm_area_struct *);
145 int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *);
146 int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *);
147 
148 static inline int anon_vma_prepare(struct vm_area_struct *vma)
149 {
150         if (likely(vma->anon_vma))
151                 return 0;
152 
153         return __anon_vma_prepare(vma);
154 }
155 
156 static inline void anon_vma_merge(struct vm_area_struct *vma,
157                                   struct vm_area_struct *next)
158 {
159         VM_BUG_ON_VMA(vma->anon_vma != next->anon_vma, vma);
160         unlink_anon_vmas(next);
161 }
162 
163 struct anon_vma *page_get_anon_vma(struct page *page);
164 
165 /* bitflags for do_page_add_anon_rmap() */
166 #define RMAP_EXCLUSIVE 0x01
167 #define RMAP_COMPOUND 0x02
168 
169 /*
170  * rmap interfaces called when adding or removing pte of page
171  */
172 void page_move_anon_rmap(struct page *, struct vm_area_struct *);
173 void page_add_anon_rmap(struct page *, struct vm_area_struct *,
174                 unsigned long, bool);
175 void do_page_add_anon_rmap(struct page *, struct vm_area_struct *,
176                            unsigned long, int);
177 void page_add_new_anon_rmap(struct page *, struct vm_area_struct *,
178                 unsigned long, bool);
179 void page_add_file_rmap(struct page *, bool);
180 void page_remove_rmap(struct page *, bool);
181 
182 void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *,
183                             unsigned long);
184 void hugepage_add_new_anon_rmap(struct page *, struct vm_area_struct *,
185                                 unsigned long);
186 
187 static inline void page_dup_rmap(struct page *page, bool compound)
188 {
189         atomic_inc(compound ? compound_mapcount_ptr(page) : &page->_mapcount);
190 }
191 
192 /*
193  * Called from mm/vmscan.c to handle paging out
194  */
195 int page_referenced(struct page *, int is_locked,
196                         struct mem_cgroup *memcg, unsigned long *vm_flags);
197 
198 bool try_to_unmap(struct page *, enum ttu_flags flags);
199 
200 /* Avoid racy checks */
201 #define PVMW_SYNC               (1 << 0)
202 /* Look for migarion entries rather than present PTEs */
203 #define PVMW_MIGRATION          (1 << 1)
204 
205 struct page_vma_mapped_walk {
206         struct page *page;
207         struct vm_area_struct *vma;
208         unsigned long address;
209         pmd_t *pmd;
210         pte_t *pte;
211         spinlock_t *ptl;
212         unsigned int flags;
213 };
214 
215 static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
216 {
217         if (pvmw->pte)
218                 pte_unmap(pvmw->pte);
219         if (pvmw->ptl)
220                 spin_unlock(pvmw->ptl);
221 }
222 
223 bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw);
224 
225 /*
226  * Used by swapoff to help locate where page is expected in vma.
227  */
228 unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
229 
230 /*
231  * Cleans the PTEs of shared mappings.
232  * (and since clean PTEs should also be readonly, write protects them too)
233  *
234  * returns the number of cleaned PTEs.
235  */
236 int page_mkclean(struct page *);
237 
238 /*
239  * called in munlock()/munmap() path to check for other vmas holding
240  * the page mlocked.
241  */
242 void try_to_munlock(struct page *);
243 
244 void remove_migration_ptes(struct page *old, struct page *new, bool locked);
245 
246 /*
247  * Called by memory-failure.c to kill processes.
248  */
249 struct anon_vma *page_lock_anon_vma_read(struct page *page);
250 void page_unlock_anon_vma_read(struct anon_vma *anon_vma);
251 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
252 
253 /*
254  * rmap_walk_control: To control rmap traversing for specific needs
255  *
256  * arg: passed to rmap_one() and invalid_vma()
257  * rmap_one: executed on each vma where page is mapped
258  * done: for checking traversing termination condition
259  * anon_lock: for getting anon_lock by optimized way rather than default
260  * invalid_vma: for skipping uninterested vma
261  */
262 struct rmap_walk_control {
263         void *arg;
264         /*
265          * Return false if page table scanning in rmap_walk should be stopped.
266          * Otherwise, return true.
267          */
268         bool (*rmap_one)(struct page *page, struct vm_area_struct *vma,
269                                         unsigned long addr, void *arg);
270         int (*done)(struct page *page);
271         struct anon_vma *(*anon_lock)(struct page *page);
272         bool (*invalid_vma)(struct vm_area_struct *vma, void *arg);
273 };
274 
275 void rmap_walk(struct page *page, struct rmap_walk_control *rwc);
276 void rmap_walk_locked(struct page *page, struct rmap_walk_control *rwc);
277 
278 #else   /* !CONFIG_MMU */
279 
280 #define anon_vma_init()         do {} while (0)
281 #define anon_vma_prepare(vma)   (0)
282 #define anon_vma_link(vma)      do {} while (0)
283 
284 static inline int page_referenced(struct page *page, int is_locked,
285                                   struct mem_cgroup *memcg,
286                                   unsigned long *vm_flags)
287 {
288         *vm_flags = 0;
289         return 0;
290 }
291 
292 #define try_to_unmap(page, refs) false
293 
294 static inline int page_mkclean(struct page *page)
295 {
296         return 0;
297 }
298 
299 
300 #endif  /* CONFIG_MMU */
301 
302 #endif  /* _LINUX_RMAP_H */
303 

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