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 - hash table
20 * @n_buckets: number of buckets (a power of 2 between %TBL_L1_SIZE and
22 * @buckets: pointer to @n_buckets/%TBL_L1_SIZE pointers to %TBL_L1_SIZE pointers
24 * @rcu: RCU callback structure
25 * @obj_destructor: Called on each element when the table is destroyed.
27 * The @buckets array is logically an array of pointers to buckets. It is
28 * broken into two levels to avoid the need to kmalloc() any object larger than
29 * a single page or to use vmalloc(). @buckets is always nonnull, as is each
30 * @buckets[i], but each @buckets[i][j] is nonnull only if the specified hash
31 * bucket is nonempty (for 0 <= i < @n_buckets/%TBL_L1_SIZE, 0 <= j <
36 unsigned int n_buckets;
37 struct tbl_bucket ***buckets;
39 void (*obj_destructor)(struct tbl_node *);
43 * struct tbl_bucket - single bucket within a hash table
44 * @rcu: RCU callback structure
45 * @n_objs: number of objects in @objs[] array
46 * @objs: array of @n_objs pointers to table nodes contained inside objects
48 * The expected number of objects per bucket is 1, but this allows for an
49 * arbitrary number of collisions.
54 struct tbl_node *objs[];
57 static inline int bucket_size(int n_objs)
59 return sizeof(struct tbl_bucket) + sizeof(struct tbl_node *) * n_objs;
62 static struct tbl_bucket *bucket_alloc(int n_objs)
64 return kmalloc(bucket_size(n_objs), GFP_KERNEL);
67 static void free_buckets(struct tbl_bucket ***l1, unsigned int n_buckets,
68 void (*free_obj)(struct tbl_node *))
72 for (i = 0; i < n_buckets >> TBL_L1_BITS; i++) {
73 struct tbl_bucket **l2 = l1[i];
76 for (j = 0; j < TBL_L1_SIZE; j++) {
77 struct tbl_bucket *bucket = l2[j];
83 for (k = 0; k < bucket->n_objs; k++)
84 free_obj(bucket->objs[k]);
88 free_page((unsigned long)l2);
93 static struct tbl_bucket ***alloc_buckets(unsigned int n_buckets)
95 struct tbl_bucket ***l1;
98 l1 = kmalloc((n_buckets >> TBL_L1_BITS) * sizeof(struct tbl_bucket **),
102 for (i = 0; i < n_buckets >> TBL_L1_BITS; i++) {
103 l1[i] = (struct tbl_bucket **)get_zeroed_page(GFP_KERNEL);
105 free_buckets(l1, i << TBL_L1_BITS, 0);
113 * tbl_create - create and return a new hash table
114 * @n_buckets: number of buckets in the new table
116 * Creates and returns a new hash table, or %NULL if memory cannot be
117 * allocated. @n_buckets must be a power of 2 in the range %TBL_L1_SIZE to
120 struct tbl *tbl_create(unsigned int n_buckets)
125 n_buckets = TBL_L1_SIZE;
127 table = kzalloc(sizeof *table, GFP_KERNEL);
131 table->n_buckets = n_buckets;
132 table->buckets = alloc_buckets(n_buckets);
145 * tbl_destroy - destroy hash table and optionally the objects it contains
146 * @table: table to destroy
147 * @destructor: function to be called on objects at destruction time
149 * If a destructor is null, then the buckets in @table are destroyed
150 * but not the objects within those buckets. This behavior is useful when a
151 * table is being replaced by a larger or smaller one without destroying the
154 * If a destructor is not null, then it is called on the objects in @table
155 * before destroying the buckets.
157 void tbl_destroy(struct tbl *table, void (*destructor)(struct tbl_node *))
162 free_buckets(table->buckets, table->n_buckets, destructor);
166 static void destroy_table_rcu(struct rcu_head *rcu)
168 struct tbl *table = container_of(rcu, struct tbl, rcu);
169 tbl_destroy(table, table->obj_destructor);
173 * tbl_deferred_destroy - destroy table after a RCU grace period
174 * @table: table to destroy
175 * @destructor: function to be called on objects at destruction time
177 * Calls tbl_destroy() on @table after an RCU grace period. If @destructor is
178 * not null it is called on every element before the table is destroyed. */
179 void tbl_deferred_destroy(struct tbl *table, void (*destructor)(struct tbl_node *))
184 table->obj_destructor = destructor;
185 call_rcu(&table->rcu, destroy_table_rcu);
188 static struct tbl_bucket **find_bucket(struct tbl *table, u32 hash)
190 unsigned int l1 = (hash & (table->n_buckets - 1)) >> TBL_L1_SHIFT;
191 unsigned int l2 = hash & ((1 << TBL_L2_BITS) - 1);
192 return &table->buckets[l1][l2];
195 static int search_bucket(const struct tbl_bucket *bucket, void *target, u32 hash,
196 int (*cmp)(const struct tbl_node *, void *))
200 for (i = 0; i < bucket->n_objs; i++) {
201 struct tbl_node *obj = rcu_dereference(bucket->objs[i]);
202 if (obj->hash == hash && likely(cmp(obj, target)))
210 * tbl_lookup - searches hash table for a matching object
211 * @table: hash table to search
212 * @target: identifier for the object that is being searched for, will be
213 * provided as an argument to @cmp when making comparisions
214 * @hash: hash of @target
215 * @cmp: comparision function to match objects with the given hash, returns
216 * nonzero if the objects match, zero otherwise
218 * Searches @table for an object identified by @target. Returns the tbl_node
219 * contained in the object if successful, otherwise %NULL.
221 struct tbl_node *tbl_lookup(struct tbl *table, void *target, u32 hash,
222 int (*cmp)(const struct tbl_node *, void *))
224 struct tbl_bucket **bucketp = find_bucket(table, hash);
225 struct tbl_bucket *bucket = rcu_dereference(*bucketp);
231 index = search_bucket(bucket, target, hash, cmp);
235 return bucket->objs[index];
239 * tbl_foreach - iterate through hash table
240 * @table: table to iterate
241 * @callback: function to call for each entry
242 * @aux: Extra data to pass to @callback
244 * Iterates through all of the objects in @table in hash order, passing each of
245 * them in turn to @callback. If @callback returns nonzero, this terminates
246 * the iteration and tbl_foreach() returns the same value. Returns 0 if
247 * @callback never returns nonzero.
249 * This function does not try to intelligently handle the case where @callback
250 * adds or removes flows in @table.
252 int tbl_foreach(struct tbl *table,
253 int (*callback)(struct tbl_node *, void *aux), void *aux)
255 unsigned int i, j, k;
256 for (i = 0; i < table->n_buckets >> TBL_L1_BITS; i++) {
257 struct tbl_bucket **l2 = table->buckets[i];
258 for (j = 0; j < TBL_L1_SIZE; j++) {
259 struct tbl_bucket *bucket = rcu_dereference(l2[j]);
263 for (k = 0; k < bucket->n_objs; k++) {
264 int error = (*callback)(bucket->objs[k], aux);
273 static int insert_table_flow(struct tbl_node *node, void *new_table_)
275 struct tbl *new_table = new_table_;
276 return tbl_insert(new_table, node, node->hash);
280 * tbl_expand - create a hash table with more buckets
281 * @table: table to expand
283 * Creates a new table containing the same objects as @table but with twice
284 * as many buckets. Returns 0 if successful, otherwise a negative error. The
285 * caller should free @table upon success (probably using
286 * tbl_deferred_destroy()).
288 struct tbl *tbl_expand(struct tbl *table)
291 int n_buckets = table->n_buckets * 2;
292 struct tbl *new_table;
294 if (n_buckets >= TBL_MAX_BUCKETS) {
300 new_table = tbl_create(n_buckets);
304 if (tbl_foreach(table, insert_table_flow, new_table))
305 goto error_free_new_table;
309 error_free_new_table:
310 tbl_destroy(new_table, NULL);
316 * tbl_n_buckets - returns the number of buckets
317 * @table: table to examine
319 * Returns the number of buckets currently allocated in @table, useful when
320 * deciding whether to expand.
322 int tbl_n_buckets(struct tbl *table)
324 return table->n_buckets;
327 static void free_bucket_rcu(struct rcu_head *rcu)
329 struct tbl_bucket *bucket = container_of(rcu, struct tbl_bucket, rcu);
334 * tbl_insert - insert object into table
335 * @table: table in which to insert object
336 * @target: tbl_node contained in object to insert
337 * @hash: hash of object to insert
339 * The caller must ensure that no object considered to be identical to @target
340 * already exists in @table. Returns 0 or a negative error (currently just
343 int tbl_insert(struct tbl *table, struct tbl_node *target, u32 hash)
345 struct tbl_bucket **oldp = find_bucket(table, hash);
346 struct tbl_bucket *old = *rcu_dereference(oldp);
347 unsigned int n = old ? old->n_objs : 0;
348 struct tbl_bucket *new = bucket_alloc(n + 1);
357 memcpy(new->objs, old->objs, n * sizeof(struct tbl_node *));
358 new->objs[n] = target;
360 rcu_assign_pointer(*oldp, new);
362 call_rcu(&old->rcu, free_bucket_rcu);
370 * tbl_remove - remove object from table
371 * @table: table from which to remove object
372 * @target: tbl_node inside of object to remove
374 * The caller must ensure that @target itself is in @table. (It is not
375 * good enough for @table to contain a different object considered identical
378 * Returns 0 or a negative error (currently just -ENOMEM). Yes, it *is*
379 * possible for object deletion to fail due to lack of memory.
381 int tbl_remove(struct tbl *table, struct tbl_node *target)
383 struct tbl_bucket **oldp = find_bucket(table, target->hash);
384 struct tbl_bucket *old = *rcu_dereference(oldp);
385 unsigned int n = old->n_objs;
386 struct tbl_bucket *new;
391 new = bucket_alloc(n - 1);
396 for (i = 0; i < n; i++) {
397 struct tbl_node *obj = old->objs[i];
399 new->objs[new->n_objs++] = obj;
401 WARN_ON_ONCE(new->n_objs != n - 1);
406 rcu_assign_pointer(*oldp, new);
407 call_rcu(&old->rcu, free_bucket_rcu);
415 * tbl_count - retrieves the number of stored objects
416 * @table: table to count
418 * Returns the number of objects that have been inserted into the hash table.
420 unsigned int tbl_count(struct tbl *table)