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tmem.h
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1 /*
2  * tmem.h
3  *
4  * Transcendent memory
5  *
6  * Copyright (c) 2009-2011, Dan Magenheimer, Oracle Corp.
7  */
8 
9 #ifndef _TMEM_H_
10 #define _TMEM_H_
11 
12 #include <linux/types.h>
13 #include <linux/highmem.h>
14 #include <linux/hash.h>
15 #include <linux/atomic.h>
16 
17 /*
18  * These are pre-defined by the Xen<->Linux ABI
19  */
20 #define TMEM_PUT_PAGE 4
21 #define TMEM_GET_PAGE 5
22 #define TMEM_FLUSH_PAGE 6
23 #define TMEM_FLUSH_OBJECT 7
24 #define TMEM_POOL_PERSIST 1
25 #define TMEM_POOL_SHARED 2
26 #define TMEM_POOL_PRECOMPRESSED 4
27 #define TMEM_POOL_PAGESIZE_SHIFT 4
28 #define TMEM_POOL_PAGESIZE_MASK 0xf
29 #define TMEM_POOL_RESERVED_BITS 0x00ffff00
30 
31 /*
32  * sentinels have proven very useful for debugging but can be removed
33  * or disabled before final merge.
34  */
35 #define SENTINELS
36 #ifdef SENTINELS
37 #define DECL_SENTINEL uint32_t sentinel;
38 #define SET_SENTINEL(_x, _y) (_x->sentinel = _y##_SENTINEL)
39 #define INVERT_SENTINEL(_x, _y) (_x->sentinel = ~_y##_SENTINEL)
40 #define ASSERT_SENTINEL(_x, _y) WARN_ON(_x->sentinel != _y##_SENTINEL)
41 #define ASSERT_INVERTED_SENTINEL(_x, _y) WARN_ON(_x->sentinel != ~_y##_SENTINEL)
42 #else
43 #define DECL_SENTINEL
44 #define SET_SENTINEL(_x, _y) do { } while (0)
45 #define INVERT_SENTINEL(_x, _y) do { } while (0)
46 #define ASSERT_SENTINEL(_x, _y) do { } while (0)
47 #define ASSERT_INVERTED_SENTINEL(_x, _y) do { } while (0)
48 #endif
49 
50 #define ASSERT_SPINLOCK(_l) lockdep_assert_held(_l)
51 
52 /*
53  * A pool is the highest-level data structure managed by tmem and
54  * usually corresponds to a large independent set of pages such as
55  * a filesystem. Each pool has an id, and certain attributes and counters.
56  * It also contains a set of hash buckets, each of which contains an rbtree
57  * of objects and a lock to manage concurrency within the pool.
58  */
59 
60 #define TMEM_HASH_BUCKET_BITS 8
61 #define TMEM_HASH_BUCKETS (1<<TMEM_HASH_BUCKET_BITS)
62 
63 struct tmem_hashbucket {
64  struct rb_root obj_rb_root;
65  spinlock_t lock;
66 };
67 
68 struct tmem_pool {
69  void *client; /* "up" for some clients, avoids table lookup */
70  struct list_head pool_list;
71  uint32_t pool_id;
72  bool persistent;
73  bool shared;
74  atomic_t obj_count;
75  atomic_t refcount;
76  struct tmem_hashbucket hashbucket[TMEM_HASH_BUCKETS];
77  DECL_SENTINEL
78 };
79 
80 #define is_persistent(_p) (_p->persistent)
81 #define is_ephemeral(_p) (!(_p->persistent))
82 
83 /*
84  * An object id ("oid") is large: 192-bits (to ensure, for example, files
85  * in a modern filesystem can be uniquely identified).
86  */
87 
88 struct tmem_oid {
89  uint64_t oid[3];
90 };
91 
92 static inline void tmem_oid_set_invalid(struct tmem_oid *oidp)
93 {
94  oidp->oid[0] = oidp->oid[1] = oidp->oid[2] = -1UL;
95 }
96 
97 static inline bool tmem_oid_valid(struct tmem_oid *oidp)
98 {
99  return oidp->oid[0] != -1UL || oidp->oid[1] != -1UL ||
100  oidp->oid[2] != -1UL;
101 }
102 
103 static inline int tmem_oid_compare(struct tmem_oid *left,
104  struct tmem_oid *right)
105 {
106  int ret;
107 
108  if (left->oid[2] == right->oid[2]) {
109  if (left->oid[1] == right->oid[1]) {
110  if (left->oid[0] == right->oid[0])
111  ret = 0;
112  else if (left->oid[0] < right->oid[0])
113  ret = -1;
114  else
115  return 1;
116  } else if (left->oid[1] < right->oid[1])
117  ret = -1;
118  else
119  ret = 1;
120  } else if (left->oid[2] < right->oid[2])
121  ret = -1;
122  else
123  ret = 1;
124  return ret;
125 }
126 
127 static inline unsigned tmem_oid_hash(struct tmem_oid *oidp)
128 {
129  return hash_long(oidp->oid[0] ^ oidp->oid[1] ^ oidp->oid[2],
130  TMEM_HASH_BUCKET_BITS);
131 }
132 
133 /*
134  * A tmem_obj contains an identifier (oid), pointers to the parent
135  * pool and the rb_tree to which it belongs, counters, and an ordered
136  * set of pampds, structured in a radix-tree-like tree. The intermediate
137  * nodes of the tree are called tmem_objnodes.
138  */
139 
140 struct tmem_objnode;
141 
142 struct tmem_obj {
143  struct tmem_oid oid;
144  struct tmem_pool *pool;
145  struct rb_node rb_tree_node;
146  struct tmem_objnode *objnode_tree_root;
147  unsigned int objnode_tree_height;
148  unsigned long objnode_count;
149  long pampd_count;
150  void *extra; /* for private use by pampd implementation */
151  DECL_SENTINEL
152 };
153 
154 #define OBJNODE_TREE_MAP_SHIFT 6
155 #define OBJNODE_TREE_MAP_SIZE (1UL << OBJNODE_TREE_MAP_SHIFT)
156 #define OBJNODE_TREE_MAP_MASK (OBJNODE_TREE_MAP_SIZE-1)
157 #define OBJNODE_TREE_INDEX_BITS (8 /* CHAR_BIT */ * sizeof(unsigned long))
158 #define OBJNODE_TREE_MAX_PATH \
159  (OBJNODE_TREE_INDEX_BITS/OBJNODE_TREE_MAP_SHIFT + 2)
160 
161 struct tmem_objnode {
162  struct tmem_obj *obj;
163  DECL_SENTINEL
164  void *slots[OBJNODE_TREE_MAP_SIZE];
165  unsigned int slots_in_use;
166 };
167 
168 /* pampd abstract datatype methods provided by the PAM implementation */
169 struct tmem_pamops {
170  void *(*create)(char *, size_t, bool, int,
171  struct tmem_pool *, struct tmem_oid *, uint32_t);
172  int (*get_data)(char *, size_t *, bool, void *, struct tmem_pool *,
173  struct tmem_oid *, uint32_t);
174  int (*get_data_and_free)(char *, size_t *, bool, void *,
175  struct tmem_pool *, struct tmem_oid *,
176  uint32_t);
177  void (*free)(void *, struct tmem_pool *, struct tmem_oid *, uint32_t);
178  void (*free_obj)(struct tmem_pool *, struct tmem_obj *);
179  bool (*is_remote)(void *);
180  void (*new_obj)(struct tmem_obj *);
181  int (*replace_in_obj)(void *, struct tmem_obj *);
182 };
183 extern void tmem_register_pamops(struct tmem_pamops *m);
184 
185 /* memory allocation methods provided by the host implementation */
186 struct tmem_hostops {
187  struct tmem_obj *(*obj_alloc)(struct tmem_pool *);
188  void (*obj_free)(struct tmem_obj *, struct tmem_pool *);
189  struct tmem_objnode *(*objnode_alloc)(struct tmem_pool *);
190  void (*objnode_free)(struct tmem_objnode *, struct tmem_pool *);
191 };
192 extern void tmem_register_hostops(struct tmem_hostops *m);
193 
194 /* core tmem accessor functions */
195 extern int tmem_put(struct tmem_pool *, struct tmem_oid *, uint32_t index,
196  char *, size_t, bool, bool);
197 extern int tmem_get(struct tmem_pool *, struct tmem_oid *, uint32_t index,
198  char *, size_t *, bool, int);
199 extern int tmem_replace(struct tmem_pool *, struct tmem_oid *, uint32_t index,
200  void *);
201 extern int tmem_flush_page(struct tmem_pool *, struct tmem_oid *,
202  uint32_t index);
203 extern int tmem_flush_object(struct tmem_pool *, struct tmem_oid *);
204 extern int tmem_destroy_pool(struct tmem_pool *);
205 extern void tmem_new_pool(struct tmem_pool *, uint32_t);
206 #endif /* _TMEM_H */
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