2 * Copyright (c) 2009, 2010 Nicira Networks.
3 * Distributed under the terms of the GNU GPL version 2.
5 * Significant portions of this file may be copied from parts of the Linux
6 * kernel, by Linus Torvalds and others.
13 #include <linux/gfp.h>
14 #include <linux/slab.h>
16 #include <asm/pgtable.h>
19 * struct tbl_bucket - single bucket within a hash table
20 * @rcu: RCU callback structure
21 * @n_objs: number of objects in @objs[] array
22 * @objs: array of @n_objs pointers to table nodes contained inside objects
24 * The expected number of objects per bucket is 1, but this allows for an
25 * arbitrary number of collisions.
30 struct tbl_node *objs[];
33 static inline int bucket_size(int n_objs)
35 return sizeof(struct tbl_bucket) + sizeof(struct tbl_node *) * n_objs;
38 static struct tbl_bucket *bucket_alloc(int n_objs)
40 return kmalloc(bucket_size(n_objs), GFP_KERNEL);
43 static void free_buckets(struct tbl_bucket ***l1, unsigned int n_buckets,
44 void (*free_obj)(struct tbl_node *))
48 for (i = 0; i < n_buckets >> TBL_L1_BITS; i++) {
49 struct tbl_bucket **l2 = l1[i];
52 for (j = 0; j < TBL_L1_SIZE; j++) {
53 struct tbl_bucket *bucket = l2[j];
59 for (k = 0; k < bucket->n_objs; k++)
60 free_obj(bucket->objs[k]);
64 free_page((unsigned long)l2);
69 static struct tbl_bucket ***alloc_buckets(unsigned int n_buckets)
71 struct tbl_bucket ***l1;
74 l1 = kmalloc((n_buckets >> TBL_L1_BITS) * sizeof(struct tbl_bucket **),
78 for (i = 0; i < n_buckets >> TBL_L1_BITS; i++) {
79 l1[i] = (struct tbl_bucket **)get_zeroed_page(GFP_KERNEL);
81 free_buckets(l1, i << TBL_L1_BITS, NULL);
89 * tbl_create - create and return a new hash table
90 * @n_buckets: number of buckets in the new table
92 * Creates and returns a new hash table, or %NULL if memory cannot be
93 * allocated. @n_buckets must be a power of 2 in the range %TBL_MIN_BUCKETS to
96 struct tbl *tbl_create(unsigned int n_buckets)
100 table = kzalloc(sizeof *table, GFP_KERNEL);
104 table->n_buckets = n_buckets;
105 table->buckets = alloc_buckets(n_buckets);
118 * tbl_destroy - destroy hash table and optionally the objects it contains
119 * @table: table to destroy
120 * @destructor: function to be called on objects at destruction time
122 * If a destructor is null, then the buckets in @table are destroyed
123 * but not the objects within those buckets. This behavior is useful when a
124 * table is being replaced by a larger or smaller one without destroying the
127 * If a destructor is not null, then it is called on the objects in @table
128 * before destroying the buckets.
130 void tbl_destroy(struct tbl *table, void (*destructor)(struct tbl_node *))
135 free_buckets(table->buckets, table->n_buckets, destructor);
139 static void destroy_table_rcu(struct rcu_head *rcu)
141 struct tbl *table = container_of(rcu, struct tbl, rcu);
142 tbl_destroy(table, table->obj_destructor);
146 * tbl_deferred_destroy - destroy table after a RCU grace period
147 * @table: table to destroy
148 * @destructor: function to be called on objects at destruction time
150 * Calls tbl_destroy() on @table after an RCU grace period. If @destructor is
151 * not null it is called on every element before the table is destroyed. */
152 void tbl_deferred_destroy(struct tbl *table, void (*destructor)(struct tbl_node *))
157 table->obj_destructor = destructor;
158 call_rcu(&table->rcu, destroy_table_rcu);
161 static struct tbl_bucket __rcu **find_bucket(struct tbl *table, u32 hash)
163 unsigned int l1 = (hash & (table->n_buckets - 1)) >> TBL_L1_SHIFT;
164 unsigned int l2 = hash & ((1 << TBL_L2_BITS) - 1);
165 return &table->buckets[l1][l2];
168 static int search_bucket(const struct tbl_bucket *bucket, void *target, u32 hash,
169 int (*cmp)(const struct tbl_node *, void *))
173 for (i = 0; i < bucket->n_objs; i++) {
174 struct tbl_node *obj = bucket->objs[i];
175 if (obj->hash == hash && likely(cmp(obj, target)))
183 * tbl_lookup - searches hash table for a matching object
184 * @table: hash table to search
185 * @target: identifier for the object that is being searched for, will be
186 * provided as an argument to @cmp when making comparisions
187 * @hash: hash of @target
188 * @cmp: comparision function to match objects with the given hash, returns
189 * nonzero if the objects match, zero otherwise
191 * Searches @table for an object identified by @target. Returns the tbl_node
192 * contained in the object if successful, otherwise %NULL.
194 struct tbl_node *tbl_lookup(struct tbl *table, void *target, u32 hash,
195 int (*cmp)(const struct tbl_node *, void *))
197 struct tbl_bucket __rcu **bucketp = find_bucket(table, hash);
198 struct tbl_bucket *bucket = rcu_dereference(*bucketp);
204 index = search_bucket(bucket, target, hash, cmp);
208 return bucket->objs[index];
212 * tbl_foreach - iterate through hash table
213 * @table: table to iterate
214 * @callback: function to call for each entry
215 * @aux: Extra data to pass to @callback
217 * Iterates through all of the objects in @table in hash order, passing each of
218 * them in turn to @callback. If @callback returns nonzero, this terminates
219 * the iteration and tbl_foreach() returns the same value. Returns 0 if
220 * @callback never returns nonzero.
222 * This function does not try to intelligently handle the case where @callback
223 * adds or removes flows in @table.
225 int tbl_foreach(struct tbl *table,
226 int (*callback)(struct tbl_node *, void *aux), void *aux)
228 unsigned int i, j, k;
229 for (i = 0; i < table->n_buckets >> TBL_L1_BITS; i++) {
230 struct tbl_bucket __rcu **l2 = table->buckets[i];
231 for (j = 0; j < TBL_L1_SIZE; j++) {
232 struct tbl_bucket *bucket = rcu_dereference(l2[j]);
236 for (k = 0; k < bucket->n_objs; k++) {
237 int error = (*callback)(bucket->objs[k], aux);
246 static int insert_table_flow(struct tbl_node *node, void *new_table_)
248 struct tbl *new_table = new_table_;
249 return tbl_insert(new_table, node, node->hash);
253 * tbl_expand - create a hash table with more buckets
254 * @table: table to expand
256 * Creates a new table containing the same objects as @table but with twice
257 * as many buckets. Returns 0 if successful, otherwise a negative error. The
258 * caller should free @table upon success (probably using
259 * tbl_deferred_destroy()).
261 struct tbl *tbl_expand(struct tbl *table)
264 int n_buckets = table->n_buckets * 2;
265 struct tbl *new_table;
267 if (n_buckets >= TBL_MAX_BUCKETS) {
273 new_table = tbl_create(TBL_MIN_BUCKETS);
277 if (tbl_foreach(table, insert_table_flow, new_table))
278 goto error_free_new_table;
282 error_free_new_table:
283 tbl_destroy(new_table, NULL);
289 * tbl_n_buckets - returns the number of buckets
290 * @table: table to examine
292 * Returns the number of buckets currently allocated in @table, useful when
293 * deciding whether to expand.
295 int tbl_n_buckets(struct tbl *table)
297 return table->n_buckets;
300 static void free_bucket_rcu(struct rcu_head *rcu)
302 struct tbl_bucket *bucket = container_of(rcu, struct tbl_bucket, rcu);
307 * tbl_insert - insert object into table
308 * @table: table in which to insert object
309 * @target: tbl_node contained in object to insert
310 * @hash: hash of object to insert
312 * The caller must ensure that no object considered to be identical to @target
313 * already exists in @table. Returns 0 or a negative error (currently just
316 int tbl_insert(struct tbl *table, struct tbl_node *target, u32 hash)
318 struct tbl_bucket __rcu **oldp = find_bucket(table, hash);
319 struct tbl_bucket *old = rcu_dereference(*oldp);
320 unsigned int n = old ? old->n_objs : 0;
321 struct tbl_bucket *new = bucket_alloc(n + 1);
330 memcpy(new->objs, old->objs, n * sizeof(struct tbl_node *));
331 new->objs[n] = target;
333 rcu_assign_pointer(*oldp, new);
335 call_rcu(&old->rcu, free_bucket_rcu);
343 * tbl_remove - remove object from table
344 * @table: table from which to remove object
345 * @target: tbl_node inside of object to remove
347 * The caller must ensure that @target itself is in @table. (It is not
348 * good enough for @table to contain a different object considered identical
351 * Returns 0 or a negative error (currently just -ENOMEM). Yes, it *is*
352 * possible for object deletion to fail due to lack of memory.
354 int tbl_remove(struct tbl *table, struct tbl_node *target)
356 struct tbl_bucket __rcu **oldp = find_bucket(table, target->hash);
357 struct tbl_bucket *old = rcu_dereference(*oldp);
358 unsigned int n = old->n_objs;
359 struct tbl_bucket *new;
364 new = bucket_alloc(n - 1);
369 for (i = 0; i < n; i++) {
370 struct tbl_node *obj = old->objs[i];
372 new->objs[new->n_objs++] = obj;
374 WARN_ON_ONCE(new->n_objs != n - 1);
379 rcu_assign_pointer(*oldp, new);
380 call_rcu(&old->rcu, free_bucket_rcu);
388 * tbl_count - retrieves the number of stored objects
389 * @table: table to count
391 * Returns the number of objects that have been inserted into the hash table.
393 unsigned int tbl_count(struct tbl *table)