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>
This commit is contained in:
Tom Herbert 2017-12-04 10:31:42 -08:00 committed by David S. Miller
parent 97a6ec4ac0
commit 2db54b475a
2 changed files with 89 additions and 16 deletions

View File

@ -207,6 +207,7 @@ struct rhashtable_iter {
struct rhashtable_walker walker;
unsigned int slot;
unsigned int skip;
bool end_of_table;
};
static inline unsigned long rht_marker(const struct rhashtable *ht, u32 hash)
@ -386,6 +387,7 @@ static inline void rhashtable_walk_start(struct rhashtable_iter *iter)
}
void *rhashtable_walk_next(struct rhashtable_iter *iter);
void *rhashtable_walk_peek(struct rhashtable_iter *iter);
void rhashtable_walk_stop(struct rhashtable_iter *iter) __releases(RCU);
void rhashtable_free_and_destroy(struct rhashtable *ht,

View File

@ -707,6 +707,7 @@ void rhashtable_walk_enter(struct rhashtable *ht, struct rhashtable_iter *iter)
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 @@ int rhashtable_walk_start_check(struct rhashtable_iter *iter)
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 @@ int rhashtable_walk_start_check(struct rhashtable_iter *iter)
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 @@ void *rhashtable_walk_next(struct rhashtable_iter *iter)
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;
@ -840,12 +834,89 @@ next:
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