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Commit 2db54b47 authored by Tom Herbert's avatar Tom Herbert Committed by David S. Miller
Browse files

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: default avatarTom Herbert <tom@quantonium.net>
Acked-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 97a6ec4a

include/linux/rhashtable.h

+2 −0
Original line number Diff line number Diff line
@@ -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,

lib/rhashtable.c

+87 −16
Original line number Diff line number Diff line
@@ -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

 * @iter:	Hash table iterator

 * __rhashtable_walk_find_next - Find the next element in a table (or the first

 * one in case of a new walk).

 *

 * Note that you must call rhashtable_walk_stop when you are finished

 * with the walk.

 * @iter:	Hash table iterator

 *

 * Returns the next object or NULL when the end of the table is reached.

 * Returns the found 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 @@ void *rhashtable_walk_next(struct rhashtable_iter *iter) 
		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