rhashtable: Add rhastable_walk_peek
This function is like rhashtable_walk_next except that it only returns
the current element in the inter and does not advance the iter.
This patch also creates __rhashtable_walk_find_next. It finds the next
element in the table when the entry cached in iter is NULL or at the end
of a slot. __rhashtable_walk_find_next is called from
rhashtable_walk_next and rhastable_walk_peek.
end_of_table is an added field to the iter structure. This indicates
that the end of table was reached (walker.tbl being NULL is not a
sufficient condition for end of table).
Signed-off-by: Tom Herbert <tom@quantonium.net>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 1935e86..6fc52d8 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -707,6 +707,7 @@
iter->p = NULL;
iter->slot = 0;
iter->skip = 0;
+ iter->end_of_table = 0;
spin_lock(&ht->lock);
iter->walker.tbl =
@@ -761,7 +762,7 @@
list_del(&iter->walker.list);
spin_unlock(&ht->lock);
- if (!iter->walker.tbl) {
+ if (!iter->walker.tbl && !iter->end_of_table) {
iter->walker.tbl = rht_dereference_rcu(ht->tbl, ht);
return -EAGAIN;
}
@@ -771,18 +772,16 @@
EXPORT_SYMBOL_GPL(rhashtable_walk_start_check);
/**
- * rhashtable_walk_next - Return the next object and advance the iterator
+ * __rhashtable_walk_find_next - Find the next element in a table (or the first
+ * one in case of a new walk).
+ *
* @iter: Hash table iterator
*
- * Note that you must call rhashtable_walk_stop when you are finished
- * with the walk.
+ * Returns the found object or NULL when the end of the table is reached.
*
- * 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.
+ * Returns -EAGAIN if resize event occurred.
*/
-void *rhashtable_walk_next(struct rhashtable_iter *iter)
+static void *__rhashtable_walk_find_next(struct rhashtable_iter *iter)
{
struct bucket_table *tbl = iter->walker.tbl;
struct rhlist_head *list = iter->list;
@@ -790,13 +789,8 @@
struct rhash_head *p = iter->p;
bool rhlist = ht->rhlist;
- if (p) {
- if (!rhlist || !(list = rcu_dereference(list->next))) {
- p = rcu_dereference(p->next);
- list = container_of(p, struct rhlist_head, rhead);
- }
- goto next;
- }
+ if (!tbl)
+ return NULL;
for (; iter->slot < tbl->size; iter->slot++) {
int skip = iter->skip;
@@ -840,13 +834,90 @@
iter->slot = 0;
iter->skip = 0;
return ERR_PTR(-EAGAIN);
+ } else {
+ iter->end_of_table = true;
}
return NULL;
}
+
+/**
+ * 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 occurred. 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)
+{
+ struct rhlist_head *list = iter->list;
+ struct rhashtable *ht = iter->ht;
+ struct rhash_head *p = iter->p;
+ bool rhlist = ht->rhlist;
+
+ if (p) {
+ if (!rhlist || !(list = rcu_dereference(list->next))) {
+ p = rcu_dereference(p->next);
+ list = container_of(p, struct rhlist_head, rhead);
+ }
+ if (!rht_is_a_nulls(p)) {
+ iter->skip++;
+ iter->p = p;
+ iter->list = list;
+ return rht_obj(ht, rhlist ? &list->rhead : p);
+ }
+
+ /* At the end of this slot, switch to next one and then find
+ * next entry from that point.
+ */
+ iter->skip = 0;
+ iter->slot++;
+ }
+
+ return __rhashtable_walk_find_next(iter);
+}
EXPORT_SYMBOL_GPL(rhashtable_walk_next);
/**
+ * rhashtable_walk_peek - Return the next object but don't advance the iterator
+ * @iter: Hash table iterator
+ *
+ * Returns the next object or NULL when the end of the table is reached.
+ *
+ * Returns -EAGAIN if resize event occurred. Note that the iterator
+ * will rewind back to the beginning and you may continue to use it.
+ */
+void *rhashtable_walk_peek(struct rhashtable_iter *iter)
+{
+ struct rhlist_head *list = iter->list;
+ struct rhashtable *ht = iter->ht;
+ struct rhash_head *p = iter->p;
+
+ if (p)
+ return rht_obj(ht, ht->rhlist ? &list->rhead : p);
+
+ /* No object found in current iter, find next one in the table. */
+
+ if (iter->skip) {
+ /* A nonzero skip value points to the next entry in the table
+ * beyond that last one that was found. Decrement skip so
+ * we find the current value. __rhashtable_walk_find_next
+ * will restore the original value of skip assuming that
+ * the table hasn't changed.
+ */
+ iter->skip--;
+ }
+
+ return __rhashtable_walk_find_next(iter);
+}
+EXPORT_SYMBOL_GPL(rhashtable_walk_peek);
+
+/**
* rhashtable_walk_stop - Finish a hash table walk
* @iter: Hash table iterator
*