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_lock & 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_SPLIT_HUGE_PMD	= 0x4,	/* split huge PMD if any */
90 	TTU_IGNORE_MLOCK	= 0x8,	/* ignore mlock */
91 	TTU_SYNC		= 0x10,	/* avoid racy checks with PVMW_SYNC */
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
get_anon_vma(struct anon_vma * anon_vma)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 
put_anon_vma(struct anon_vma * anon_vma)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 
anon_vma_lock_write(struct anon_vma * anon_vma)114 static inline void anon_vma_lock_write(struct anon_vma *anon_vma)
115 {
116 	down_write(&anon_vma->root->rwsem);
117 }
118 
anon_vma_unlock_write(struct anon_vma * anon_vma)119 static inline void anon_vma_unlock_write(struct anon_vma *anon_vma)
120 {
121 	up_write(&anon_vma->root->rwsem);
122 }
123 
anon_vma_lock_read(struct anon_vma * anon_vma)124 static inline void anon_vma_lock_read(struct anon_vma *anon_vma)
125 {
126 	down_read(&anon_vma->root->rwsem);
127 }
128 
anon_vma_unlock_read(struct anon_vma * anon_vma)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 
anon_vma_prepare(struct vm_area_struct * vma)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 
anon_vma_merge(struct vm_area_struct * vma,struct vm_area_struct * next)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 
page_dup_rmap(struct page * page,bool compound)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 void try_to_migrate(struct page *page, enum ttu_flags flags);
195 void try_to_unmap(struct page *, enum ttu_flags flags);
196 
197 int make_device_exclusive_range(struct mm_struct *mm, unsigned long start,
198 				unsigned long end, struct page **pages,
199 				void *arg);
200 
201 /* Avoid racy checks */
202 #define PVMW_SYNC		(1 << 0)
203 /* Look for migarion entries rather than present PTEs */
204 #define PVMW_MIGRATION		(1 << 1)
205 
206 struct page_vma_mapped_walk {
207 	struct page *page;
208 	struct vm_area_struct *vma;
209 	unsigned long address;
210 	pmd_t *pmd;
211 	pte_t *pte;
212 	spinlock_t *ptl;
213 	unsigned int flags;
214 };
215 
page_vma_mapped_walk_done(struct page_vma_mapped_walk * pvmw)216 static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
217 {
218 	/* HugeTLB pte is set to the relevant page table entry without pte_mapped. */
219 	if (pvmw->pte && !PageHuge(pvmw->page))
220 		pte_unmap(pvmw->pte);
221 	if (pvmw->ptl)
222 		spin_unlock(pvmw->ptl);
223 }
224 
225 bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw);
226 
227 /*
228  * Used by swapoff to help locate where page is expected in vma.
229  */
230 unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
231 
232 /*
233  * Cleans the PTEs of shared mappings.
234  * (and since clean PTEs should also be readonly, write protects them too)
235  *
236  * returns the number of cleaned PTEs.
237  */
238 int folio_mkclean(struct folio *);
239 
240 /*
241  * called in munlock()/munmap() path to check for other vmas holding
242  * the page mlocked.
243  */
244 void page_mlock(struct page *page);
245 
246 void remove_migration_ptes(struct page *old, struct page *new, bool locked);
247 
248 /*
249  * Called by memory-failure.c to kill processes.
250  */
251 struct anon_vma *page_lock_anon_vma_read(struct page *page);
252 void page_unlock_anon_vma_read(struct anon_vma *anon_vma);
253 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
254 
255 /*
256  * rmap_walk_control: To control rmap traversing for specific needs
257  *
258  * arg: passed to rmap_one() and invalid_vma()
259  * rmap_one: executed on each vma where page is mapped
260  * done: for checking traversing termination condition
261  * anon_lock: for getting anon_lock by optimized way rather than default
262  * invalid_vma: for skipping uninterested vma
263  */
264 struct rmap_walk_control {
265 	void *arg;
266 	/*
267 	 * Return false if page table scanning in rmap_walk should be stopped.
268 	 * Otherwise, return true.
269 	 */
270 	bool (*rmap_one)(struct page *page, struct vm_area_struct *vma,
271 					unsigned long addr, void *arg);
272 	int (*done)(struct page *page);
273 	struct anon_vma *(*anon_lock)(struct page *page);
274 	bool (*invalid_vma)(struct vm_area_struct *vma, void *arg);
275 };
276 
277 void rmap_walk(struct page *page, struct rmap_walk_control *rwc);
278 void rmap_walk_locked(struct page *page, struct rmap_walk_control *rwc);
279 
280 #else	/* !CONFIG_MMU */
281 
282 #define anon_vma_init()		do {} while (0)
283 #define anon_vma_prepare(vma)	(0)
284 #define anon_vma_link(vma)	do {} while (0)
285 
page_referenced(struct page * page,int is_locked,struct mem_cgroup * memcg,unsigned long * vm_flags)286 static inline int page_referenced(struct page *page, int is_locked,
287 				  struct mem_cgroup *memcg,
288 				  unsigned long *vm_flags)
289 {
290 	*vm_flags = 0;
291 	return 0;
292 }
293 
try_to_unmap(struct page * page,enum ttu_flags flags)294 static inline void try_to_unmap(struct page *page, enum ttu_flags flags)
295 {
296 }
297 
folio_mkclean(struct folio * folio)298 static inline int folio_mkclean(struct folio *folio)
299 {
300 	return 0;
301 }
302 #endif	/* CONFIG_MMU */
303 
page_mkclean(struct page * page)304 static inline int page_mkclean(struct page *page)
305 {
306 	return folio_mkclean(page_folio(page));
307 }
308 #endif	/* _LINUX_RMAP_H */
309