/include/linux/rmap.h

  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 */
 27struct 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	 */
 37	atomic_t refcount;
 38
 39	/*
 40	 * NOTE: the LSB of the head.next is set by
 41	 * mm_take_all_locks() _after_ taking the above lock. So the
 42	 * head 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 list_head head;	/* Chain 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 "same_anon_vma" list contains the anon_vma_chains
 61 * which link all the VMAs associated with this anon_vma.
 62 */
 63struct anon_vma_chain {
 64	struct vm_area_struct *vma;
 65	struct anon_vma *anon_vma;
 66	struct list_head same_vma;   /* locked by mmap_sem & page_table_lock */
 67	struct list_head same_anon_vma;	/* locked by anon_vma->mutex */
 68};
 69
 70#ifdef CONFIG_MMU
 71static inline void get_anon_vma(struct anon_vma *anon_vma)
 72{
 73	atomic_inc(&anon_vma->refcount);
 74}
 75
 76void __put_anon_vma(struct anon_vma *anon_vma);
 77
 78static inline void put_anon_vma(struct anon_vma *anon_vma)
 79{
 80	if (atomic_dec_and_test(&anon_vma->refcount))
 81		__put_anon_vma(anon_vma);
 82}
 83
 84static inline struct anon_vma *page_anon_vma(struct page *page)
 85{
 86	if (((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) !=
 87					    PAGE_MAPPING_ANON)
 88		return NULL;
 89	return page_rmapping(page);
 90}
 91
 92static inline void vma_lock_anon_vma(struct vm_area_struct *vma)
 93{
 94	struct anon_vma *anon_vma = vma->anon_vma;
 95	if (anon_vma)
 96		mutex_lock(&anon_vma->root->mutex);
 97}
 98
 99static inline void vma_unlock_anon_vma(struct vm_area_struct *vma)
100{
101	struct anon_vma *anon_vma = vma->anon_vma;
102	if (anon_vma)
103		mutex_unlock(&anon_vma->root->mutex);
104}
105
106static inline void anon_vma_lock(struct anon_vma *anon_vma)
107{
108	mutex_lock(&anon_vma->root->mutex);
109}
110
111static inline void anon_vma_unlock(struct anon_vma *anon_vma)
112{
113	mutex_unlock(&anon_vma->root->mutex);
114}
115
116/*
117 * anon_vma helper functions.
118 */
119void anon_vma_init(void);	/* create anon_vma_cachep */
120int  anon_vma_prepare(struct vm_area_struct *);
121void unlink_anon_vmas(struct vm_area_struct *);
122int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *);
123void anon_vma_moveto_tail(struct vm_area_struct *);
124int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *);
125
126static inline void anon_vma_merge(struct vm_area_struct *vma,
127				  struct vm_area_struct *next)
128{
129	VM_BUG_ON(vma->anon_vma != next->anon_vma);
130	unlink_anon_vmas(next);
131}
132
133struct anon_vma *page_get_anon_vma(struct page *page);
134
135/*
136 * rmap interfaces called when adding or removing pte of page
137 */
138void page_move_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
139void page_add_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
140void do_page_add_anon_rmap(struct page *, struct vm_area_struct *,
141			   unsigned long, int);
142void page_add_new_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
143void page_add_file_rmap(struct page *);
144void page_remove_rmap(struct page *);
145
146void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *,
147			    unsigned long);
148void hugepage_add_new_anon_rmap(struct page *, struct vm_area_struct *,
149				unsigned long);
150
151static inline void page_dup_rmap(struct page *page)
152{
153	atomic_inc(&page->_mapcount);
154}
155
156/*
157 * Called from mm/vmscan.c to handle paging out
158 */
159int page_referenced(struct page *, int is_locked,
160			struct mem_cgroup *memcg, unsigned long *vm_flags);
161int page_referenced_one(struct page *, struct vm_area_struct *,
162	unsigned long address, unsigned int *mapcount, unsigned long *vm_flags);
163
164enum ttu_flags {
165	TTU_UNMAP = 0,			/* unmap mode */
166	TTU_MIGRATION = 1,		/* migration mode */
167	TTU_MUNLOCK = 2,		/* munlock mode */
168	TTU_ACTION_MASK = 0xff,
169
170	TTU_IGNORE_MLOCK = (1 << 8),	/* ignore mlock */
171	TTU_IGNORE_ACCESS = (1 << 9),	/* don't age */
172	TTU_IGNORE_HWPOISON = (1 << 10),/* corrupted page is recoverable */
173};
174#define TTU_ACTION(x) ((x) & TTU_ACTION_MASK)
175
176bool is_vma_temporary_stack(struct vm_area_struct *vma);
177
178int try_to_unmap(struct page *, enum ttu_flags flags);
179int try_to_unmap_one(struct page *, struct vm_area_struct *,
180			unsigned long address, enum ttu_flags flags);
181
182/*
183 * Called from mm/filemap_xip.c to unmap empty zero page
184 */
185pte_t *__page_check_address(struct page *, struct mm_struct *,
186				unsigned long, spinlock_t **, int);
187
188static inline pte_t *page_check_address(struct page *page, struct mm_struct *mm,
189					unsigned long address,
190					spinlock_t **ptlp, int sync)
191{
192	pte_t *ptep;
193
194	__cond_lock(*ptlp, ptep = __page_check_address(page, mm, address,
195						       ptlp, sync));
196	return ptep;
197}
198
199/*
200 * Used by swapoff to help locate where page is expected in vma.
201 */
202unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
203
204/*
205 * Cleans the PTEs of shared mappings.
206 * (and since clean PTEs should also be readonly, write protects them too)
207 *
208 * returns the number of cleaned PTEs.
209 */
210int page_mkclean(struct page *);
211
212/*
213 * called in munlock()/munmap() path to check for other vmas holding
214 * the page mlocked.
215 */
216int try_to_munlock(struct page *);
217
218/*
219 * Called by memory-failure.c to kill processes.
220 */
221struct anon_vma *page_lock_anon_vma(struct page *page);
222void page_unlock_anon_vma(struct anon_vma *anon_vma);
223int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
224
225/*
226 * Called by migrate.c to remove migration ptes, but might be used more later.
227 */
228int rmap_walk(struct page *page, int (*rmap_one)(struct page *,
229		struct vm_area_struct *, unsigned long, void *), void *arg);
230
231#else	/* !CONFIG_MMU */
232
233#define anon_vma_init()		do {} while (0)
234#define anon_vma_prepare(vma)	(0)
235#define anon_vma_link(vma)	do {} while (0)
236
237static inline int page_referenced(struct page *page, int is_locked,
238				  struct mem_cgroup *memcg,
239				  unsigned long *vm_flags)
240{
241	*vm_flags = 0;
242	return 0;
243}
244
245#define try_to_unmap(page, refs) SWAP_FAIL
246
247static inline int page_mkclean(struct page *page)
248{
249	return 0;
250}
251
252
253#endif	/* CONFIG_MMU */
254
255/*
256 * Return values of try_to_unmap
257 */
258#define SWAP_SUCCESS	0
259#define SWAP_AGAIN	1
260#define SWAP_FAIL	2
261#define SWAP_MLOCK	3
262
263#endif	/* _LINUX_RMAP_H */