+/**
+ * rhashtable_lookup_insert - lookup and insert object into hash table
+ * @ht: hash table
+ * @obj: pointer to hash head inside object
+ *
+ * Locks down the bucket chain in both the old and new table if a resize
+ * is in progress to ensure that writers can't remove from the old table
+ * and can't insert to the new table during the atomic operation of search
+ * and insertion. Searches for duplicates in both the old and new table if
+ * a resize is in progress.
+ *
+ * This lookup function may only be used for fixed key hash table (key_len
+ * parameter set). It will BUG() if used inappropriately.
+ *
+ * It is safe to call this function from atomic context.
+ *
+ * Will trigger an automatic deferred table resizing if the size grows
+ * beyond the watermark indicated by grow_decision() which can be passed
+ * to rhashtable_init().
+ */
+bool rhashtable_lookup_insert(struct rhashtable *ht, struct rhash_head *obj)
+{
+ struct rhashtable_compare_arg arg = {
+ .ht = ht,
+ .key = rht_obj(ht, obj) + ht->p.key_offset,
+ };
+
+ BUG_ON(!ht->p.key_len);
+
+ return rhashtable_lookup_compare_insert(ht, obj, &rhashtable_compare,
+ &arg);
+}
+EXPORT_SYMBOL_GPL(rhashtable_lookup_insert);
+
+/**
+ * rhashtable_lookup_compare_insert - search and insert object to hash table
+ * with compare function
+ * @ht: hash table
+ * @obj: pointer to hash head inside object
+ * @compare: compare function, must return true on match
+ * @arg: argument passed on to compare function
+ *
+ * Locks down the bucket chain in both the old and new table if a resize
+ * is in progress to ensure that writers can't remove from the old table
+ * and can't insert to the new table during the atomic operation of search
+ * and insertion. Searches for duplicates in both the old and new table if
+ * a resize is in progress.
+ *
+ * Lookups may occur in parallel with hashtable mutations and resizing.
+ *
+ * Will trigger an automatic deferred table resizing if the size grows
+ * beyond the watermark indicated by grow_decision() which can be passed
+ * to rhashtable_init().
+ */
+bool rhashtable_lookup_compare_insert(struct rhashtable *ht,
+ struct rhash_head *obj,
+ bool (*compare)(void *, void *),
+ void *arg)
+{
+ struct bucket_table *new_tbl, *old_tbl;
+ u32 new_hash;
+ bool success = true;
+
+ BUG_ON(!ht->p.key_len);
+
+ rcu_read_lock();
+ old_tbl = rht_dereference_rcu(ht->tbl, ht);
+ new_tbl = rht_dereference_rcu(ht->future_tbl, ht);
+ new_hash = obj_raw_hashfn(ht, rht_obj(ht, obj));
+
+ lock_buckets(new_tbl, old_tbl, new_hash);
+
+ if (rhashtable_lookup_compare(ht, rht_obj(ht, obj) + ht->p.key_offset,
+ compare, arg)) {
+ success = false;
+ goto exit;
+ }
+
+ __rhashtable_insert(ht, obj, new_tbl, new_hash);
+
+exit:
+ unlock_buckets(new_tbl, old_tbl, new_hash);
+ rcu_read_unlock();
+
+ return success;
+}
+EXPORT_SYMBOL_GPL(rhashtable_lookup_compare_insert);
+
+/**
+ * rhashtable_walk_init - Initialise an iterator
+ * @ht: Table to walk over
+ * @iter: Hash table Iterator
+ *
+ * This function prepares a hash table walk.
+ *
+ * Note that if you restart a walk after rhashtable_walk_stop you
+ * may see the same object twice. Also, you may miss objects if
+ * there are removals in between rhashtable_walk_stop and the next
+ * call to rhashtable_walk_start.
+ *
+ * For a completely stable walk you should construct your own data
+ * structure outside the hash table.
+ *
+ * This function may sleep so you must not call it from interrupt
+ * context or with spin locks held.
+ *
+ * You must call rhashtable_walk_exit if this function returns
+ * successfully.
+ */
+int rhashtable_walk_init(struct rhashtable *ht, struct rhashtable_iter *iter)
+{
+ iter->ht = ht;
+ iter->p = NULL;
+ iter->slot = 0;
+ iter->skip = 0;
+
+ iter->walker = kmalloc(sizeof(*iter->walker), GFP_KERNEL);
+ if (!iter->walker)
+ return -ENOMEM;
+
+ mutex_lock(&ht->mutex);
+ list_add(&iter->walker->list, &ht->walkers);
+ mutex_unlock(&ht->mutex);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(rhashtable_walk_init);
+
+/**
+ * rhashtable_walk_exit - Free an iterator
+ * @iter: Hash table Iterator
+ *
+ * This function frees resources allocated by rhashtable_walk_init.
+ */
+void rhashtable_walk_exit(struct rhashtable_iter *iter)
+{
+ mutex_lock(&iter->ht->mutex);
+ list_del(&iter->walker->list);
+ mutex_unlock(&iter->ht->mutex);
+ kfree(iter->walker);
+}
+EXPORT_SYMBOL_GPL(rhashtable_walk_exit);
+
+/**
+ * rhashtable_walk_start - Start a hash table walk
+ * @iter: Hash table iterator
+ *
+ * Start a hash table walk. Note that we take the RCU lock in all
+ * cases including when we return an error. So you must always call
+ * rhashtable_walk_stop to clean up.
+ *
+ * Returns zero if successful.
+ *
+ * Returns -EAGAIN if resize event occured. Note that the iterator
+ * will rewind back to the beginning and you may use it immediately
+ * by calling rhashtable_walk_next.
+ */
+int rhashtable_walk_start(struct rhashtable_iter *iter)
+{
+ rcu_read_lock();
+
+ if (iter->walker->resize) {
+ iter->slot = 0;
+ iter->skip = 0;
+ iter->walker->resize = false;
+ return -EAGAIN;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(rhashtable_walk_start);
+
+/**
+ * rhashtable_walk_next - Return the next object and advance the iterator
+ * @iter: Hash table iterator
+ *
+ * Note that you must call rhashtable_walk_stop when you are finished
+ * with the walk.
+ *
+ * Returns the next object or NULL when the end of the table is reached.
+ *
+ * Returns -EAGAIN if resize event occured. Note that the iterator
+ * will rewind back to the beginning and you may continue to use it.
+ */
+void *rhashtable_walk_next(struct rhashtable_iter *iter)
+{
+ const struct bucket_table *tbl;
+ struct rhashtable *ht = iter->ht;
+ struct rhash_head *p = iter->p;
+ void *obj = NULL;
+
+ tbl = rht_dereference_rcu(ht->tbl, ht);
+
+ if (p) {
+ p = rht_dereference_bucket_rcu(p->next, tbl, iter->slot);
+ goto next;
+ }
+
+ for (; iter->slot < tbl->size; iter->slot++) {
+ int skip = iter->skip;
+
+ rht_for_each_rcu(p, tbl, iter->slot) {
+ if (!skip)
+ break;
+ skip--;
+ }
+
+next:
+ if (!rht_is_a_nulls(p)) {
+ iter->skip++;
+ iter->p = p;
+ obj = rht_obj(ht, p);
+ goto out;
+ }
+
+ iter->skip = 0;
+ }
+
+ iter->p = NULL;
+
+out:
+ if (iter->walker->resize) {
+ iter->p = NULL;
+ iter->slot = 0;
+ iter->skip = 0;
+ iter->walker->resize = false;
+ return ERR_PTR(-EAGAIN);
+ }
+
+ return obj;
+}
+EXPORT_SYMBOL_GPL(rhashtable_walk_next);
+
+/**
+ * rhashtable_walk_stop - Finish a hash table walk
+ * @iter: Hash table iterator
+ *
+ * Finish a hash table walk.
+ */
+void rhashtable_walk_stop(struct rhashtable_iter *iter)
+{
+ rcu_read_unlock();
+ iter->p = NULL;
+}
+EXPORT_SYMBOL_GPL(rhashtable_walk_stop);
+