2 * Copyright (c) 2009, 2010, 2011 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 __rcu ***l1,
44 unsigned int n_buckets,
45 void (*free_obj)(struct tbl_node *))
49 for (i = 0; i < n_buckets >> TBL_L1_SHIFT; i++) {
50 struct tbl_bucket __rcu **l2 = l1[i];
53 for (j = 0; j < TBL_L2_SIZE; j++) {
54 struct tbl_bucket *bucket = (struct tbl_bucket __force *)l2[j];
60 for (k = 0; k < bucket->n_objs; k++)
61 free_obj(bucket->objs[k]);
65 free_page((unsigned long)l2);
70 static struct tbl_bucket __rcu ***alloc_buckets(unsigned int n_buckets)
72 struct tbl_bucket __rcu ***l1;
75 l1 = kmalloc((n_buckets >> TBL_L1_SHIFT) * sizeof(struct tbl_bucket **),
79 for (i = 0; i < n_buckets >> TBL_L1_SHIFT; i++) {
80 l1[i] = (struct tbl_bucket __rcu **)get_zeroed_page(GFP_KERNEL);
82 free_buckets(l1, i << TBL_L1_SHIFT, NULL);
90 * tbl_create - create and return a new hash table
91 * @n_buckets: number of buckets in the new table
93 * Creates and returns a new hash table, or %NULL if memory cannot be
94 * allocated. @n_buckets must be a power of 2 in the range %TBL_MIN_BUCKETS to
97 struct tbl *tbl_create(unsigned int n_buckets)
101 table = kzalloc(sizeof(*table), GFP_KERNEL);
105 table->n_buckets = n_buckets;
106 table->buckets = alloc_buckets(n_buckets);
119 * tbl_destroy - destroy hash table and optionally the objects it contains
120 * @table: table to destroy
121 * @destructor: function to be called on objects at destruction time
123 * If a destructor is null, then the buckets in @table are destroyed
124 * but not the objects within those buckets. This behavior is useful when a
125 * table is being replaced by a larger or smaller one without destroying the
128 * If a destructor is not null, then it is called on the objects in @table
129 * before destroying the buckets.
131 void tbl_destroy(struct tbl *table, void (*destructor)(struct tbl_node *))
136 free_buckets(table->buckets, table->n_buckets, destructor);
140 static void destroy_table_rcu(struct rcu_head *rcu)
142 struct tbl *table = container_of(rcu, struct tbl, rcu);
143 tbl_destroy(table, table->obj_destructor);
147 * tbl_deferred_destroy - destroy table after a RCU grace period
148 * @table: table to destroy
149 * @destructor: function to be called on objects at destruction time
151 * Calls tbl_destroy() on @table after an RCU grace period. If @destructor is
152 * not null it is called on every element before the table is destroyed. */
153 void tbl_deferred_destroy(struct tbl *table, void (*destructor)(struct tbl_node *))
158 table->obj_destructor = destructor;
159 call_rcu(&table->rcu, destroy_table_rcu);
162 static struct tbl_bucket __rcu **find_bucket(struct tbl *table, u32 hash)
164 unsigned int l1 = (hash & (table->n_buckets - 1)) >> TBL_L1_SHIFT;
165 unsigned int l2 = hash & ((1 << TBL_L2_BITS) - 1);
166 return &table->buckets[l1][l2];
169 static int search_bucket(const struct tbl_bucket *bucket, void *target, u32 hash,
170 int (*cmp)(const struct tbl_node *, void *))
174 for (i = 0; i < bucket->n_objs; i++) {
175 struct tbl_node *obj = bucket->objs[i];
176 if (obj->hash == hash && likely(cmp(obj, target)))
184 * tbl_lookup - searches hash table for a matching object
185 * @table: hash table to search
186 * @target: identifier for the object that is being searched for, will be
187 * provided as an argument to @cmp when making comparisions
188 * @hash: hash of @target
189 * @cmp: comparision function to match objects with the given hash, returns
190 * nonzero if the objects match, zero otherwise
192 * Searches @table for an object identified by @target. Returns the tbl_node
193 * contained in the object if successful, otherwise %NULL.
195 struct tbl_node *tbl_lookup(struct tbl *table, void *target, u32 hash,
196 int (*cmp)(const struct tbl_node *, void *))
198 struct tbl_bucket __rcu **bucketp = find_bucket(table, hash);
199 struct tbl_bucket *bucket = rcu_dereference(*bucketp);
205 index = search_bucket(bucket, target, hash, cmp);
209 return bucket->objs[index];
213 * tbl_foreach - iterate through hash table
214 * @table: table to iterate
215 * @callback: function to call for each entry
216 * @aux: Extra data to pass to @callback
218 * Iterates through all of the objects in @table in hash order, passing each of
219 * them in turn to @callback. If @callback returns nonzero, this terminates
220 * the iteration and tbl_foreach() returns the same value. Returns 0 if
221 * @callback never returns nonzero.
223 * This function does not try to intelligently handle the case where @callback
224 * adds or removes flows in @table.
226 int tbl_foreach(struct tbl *table,
227 int (*callback)(struct tbl_node *, void *aux), void *aux)
229 unsigned int n_l1 = table->n_buckets >> TBL_L1_SHIFT;
232 for (l1_idx = 0; l1_idx < n_l1; l1_idx++) {
233 struct tbl_bucket __rcu **l2 = table->buckets[l1_idx];
236 for (l2_idx = 0; l2_idx < TBL_L2_SIZE; l2_idx++) {
237 struct tbl_bucket *bucket;
240 bucket = rcu_dereference(l2[l2_idx]);
244 for (i = 0; i < bucket->n_objs; i++) {
245 int error = (*callback)(bucket->objs[i], aux);
255 * tbl_next - find next node in hash table
256 * @table: table to iterate
257 * @bucketp: On entry, hash value of bucket to start from. On exit, updated
258 * to bucket to start from on next call.
259 * @objp: On entry, index to start from within first bucket. On exit, updated
260 * to index to start from on next call.
262 * Returns the next node in @table in hash order, or %NULL when no nodes remain
265 * On entry, uses the values that @bucketp and @objp reference to determine
266 * where to begin iteration. Use 0 for both values to begin a new iteration.
267 * On exit, stores the values to pass on the next iteration into @bucketp and
270 struct tbl_node *tbl_next(struct tbl *table, u32 *bucketp, u32 *objp)
272 unsigned int n_l1 = table->n_buckets >> TBL_L1_SHIFT;
273 u32 s_l1_idx = *bucketp >> TBL_L1_SHIFT;
274 u32 s_l2_idx = *bucketp & (TBL_L2_SIZE - 1);
278 for (l1_idx = s_l1_idx; l1_idx < n_l1; l1_idx++) {
279 struct tbl_bucket __rcu **l2 = table->buckets[l1_idx];
282 for (l2_idx = s_l2_idx; l2_idx < TBL_L2_SIZE; l2_idx++) {
283 struct tbl_bucket *bucket;
285 bucket = rcu_dereference(l2[l2_idx]);
286 if (bucket && s_obj < bucket->n_objs) {
287 *bucketp = (l1_idx << TBL_L1_SHIFT) + l2_idx;
289 return bucket->objs[s_obj];
301 static int insert_table_flow(struct tbl_node *node, void *new_table_)
303 struct tbl *new_table = new_table_;
304 return tbl_insert(new_table, node, node->hash);
308 * tbl_expand - create a hash table with more buckets
309 * @table: table to expand
311 * Creates a new table containing the same objects as @table but with twice
312 * as many buckets. Returns 0 if successful, otherwise a negative error. The
313 * caller should free @table upon success (probably using
314 * tbl_deferred_destroy()).
316 struct tbl *tbl_expand(struct tbl *table)
319 int n_buckets = table->n_buckets * 2;
320 struct tbl *new_table;
322 if (n_buckets >= TBL_MAX_BUCKETS) {
328 new_table = tbl_create(TBL_MIN_BUCKETS);
332 if (tbl_foreach(table, insert_table_flow, new_table))
333 goto error_free_new_table;
337 error_free_new_table:
338 tbl_destroy(new_table, NULL);
344 * tbl_n_buckets - returns the number of buckets
345 * @table: table to examine
347 * Returns the number of buckets currently allocated in @table, useful when
348 * deciding whether to expand.
350 int tbl_n_buckets(struct tbl *table)
352 return table->n_buckets;
355 static void free_bucket_rcu(struct rcu_head *rcu)
357 struct tbl_bucket *bucket = container_of(rcu, struct tbl_bucket, rcu);
362 * tbl_insert - insert object into table
363 * @table: table in which to insert object
364 * @target: tbl_node contained in object to insert
365 * @hash: hash of object to insert
367 * The caller must ensure that no object considered to be identical to @target
368 * already exists in @table. Returns 0 or a negative error (currently just
371 int tbl_insert(struct tbl *table, struct tbl_node *target, u32 hash)
373 struct tbl_bucket __rcu **oldp = find_bucket(table, hash);
374 struct tbl_bucket *old = rcu_dereference(*oldp);
375 unsigned int n = old ? old->n_objs : 0;
376 struct tbl_bucket *new = bucket_alloc(n + 1);
385 memcpy(new->objs, old->objs, n * sizeof(struct tbl_node *));
386 new->objs[n] = target;
388 rcu_assign_pointer(*oldp, new);
390 call_rcu(&old->rcu, free_bucket_rcu);
398 * tbl_remove - remove object from table
399 * @table: table from which to remove object
400 * @target: tbl_node inside of object to remove
402 * The caller must ensure that @target itself is in @table. (It is not
403 * good enough for @table to contain a different object considered identical
406 * Returns 0 or a negative error (currently just -ENOMEM). Yes, it *is*
407 * possible for object deletion to fail due to lack of memory.
409 int tbl_remove(struct tbl *table, struct tbl_node *target)
411 struct tbl_bucket __rcu **oldp = find_bucket(table, target->hash);
412 struct tbl_bucket *old = rcu_dereference(*oldp);
413 unsigned int n = old->n_objs;
414 struct tbl_bucket *new;
419 new = bucket_alloc(n - 1);
424 for (i = 0; i < n; i++) {
425 struct tbl_node *obj = old->objs[i];
427 new->objs[new->n_objs++] = obj;
429 WARN_ON_ONCE(new->n_objs != n - 1);
434 rcu_assign_pointer(*oldp, new);
435 call_rcu(&old->rcu, free_bucket_rcu);
443 * tbl_count - retrieves the number of stored objects
444 * @table: table to count
446 * Returns the number of objects that have been inserted into the hash table.
448 unsigned int tbl_count(struct tbl *table)