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Date: Tue, 24 Mar 2015 14:18:20 +0100
From: Thomas Graf <tgraf@...g.ch>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org, herbert@...dor.apana.org.au
Subject: [PATCH 5/5 net-next] rhashtable: Add rhashtable_free_and_destroy()
rhashtable_destroy() variant which stops rehashes, iterates over
the table and calls a callback to release resources.
Avoids need for nft_hash to embed rhashtable internals and allows to
get rid of the being_destroyed flag. It also saves a 2nd mutex
lock upon destruction.
Also fixes an RCU lockdep splash on nft set destruction due to
calling rht_for_each_entry_safe() without holding bucket locks.
Open code this loop as we need know that no mutations may occur in
parallel.
Signed-off-by: Thomas Graf <tgraf@...g.ch>
---
include/linux/rhashtable.h | 5 +++--
lib/rhashtable.c | 49 ++++++++++++++++++++++++++++++++++++----------
net/netfilter/nft_hash.c | 25 +++++++----------------
3 files changed, 49 insertions(+), 30 deletions(-)
diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h
index d0ca452..1995db3 100644
--- a/include/linux/rhashtable.h
+++ b/include/linux/rhashtable.h
@@ -134,12 +134,10 @@ struct rhashtable_params {
* @run_work: Deferred worker to expand/shrink asynchronously
* @mutex: Mutex to protect current/future table swapping
* @lock: Spin lock to protect walker list
- * @being_destroyed: True if table is set up for destruction
*/
struct rhashtable {
struct bucket_table __rcu *tbl;
atomic_t nelems;
- bool being_destroyed;
unsigned int key_len;
unsigned int elasticity;
struct rhashtable_params p;
@@ -332,6 +330,9 @@ int rhashtable_walk_start(struct rhashtable_iter *iter) __acquires(RCU);
void *rhashtable_walk_next(struct rhashtable_iter *iter);
void rhashtable_walk_stop(struct rhashtable_iter *iter) __releases(RCU);
+void rhashtable_free_and_destroy(struct rhashtable *ht,
+ void (*free_fn)(void *ptr, void *arg),
+ void *arg);
void rhashtable_destroy(struct rhashtable *ht);
#define rht_dereference(p, ht) \
diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 93374d7..bb3a792 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -359,8 +359,6 @@ static void rht_deferred_worker(struct work_struct *work)
ht = container_of(work, struct rhashtable, run_work);
mutex_lock(&ht->mutex);
- if (ht->being_destroyed)
- goto unlock;
tbl = rht_dereference(ht->tbl, ht);
tbl = rhashtable_last_table(ht, tbl);
@@ -372,7 +370,6 @@ static void rht_deferred_worker(struct work_struct *work)
err = rhashtable_rehash_table(ht);
-unlock:
mutex_unlock(&ht->mutex);
if (err)
@@ -771,21 +768,53 @@ int rhashtable_init(struct rhashtable *ht,
EXPORT_SYMBOL_GPL(rhashtable_init);
/**
- * rhashtable_destroy - destroy hash table
+ * rhashtable_free_and_destroy - free elements and destroy hash table
* @ht: the hash table to destroy
+ * @free_fn: callback to release resources of element
+ * @arg: pointer passed to free_fn
*
- * Frees the bucket array. This function is not rcu safe, therefore the caller
- * has to make sure that no resizing may happen by unpublishing the hashtable
- * and waiting for the quiescent cycle before releasing the bucket array.
+ * Stops an eventual async resize. If defined, invokes free_fn for each
+ * element to releasal resources. Please note that RCU protected
+ * readers may still be accessing the elements. Releasing of resources
+ * must occur in a compatible manner. Then frees the bucket array.
+ *
+ * This function will eventually sleep to wait for an async resize
+ * to complete. The caller is responsible that no further write operations
+ * occurs in parallel.
*/
-void rhashtable_destroy(struct rhashtable *ht)
+void rhashtable_free_and_destroy(struct rhashtable *ht,
+ void (*free_fn)(void *ptr, void *arg),
+ void *arg)
{
- ht->being_destroyed = true;
+ const struct bucket_table *tbl;
+ unsigned int i;
cancel_work_sync(&ht->run_work);
mutex_lock(&ht->mutex);
- bucket_table_free(rht_dereference(ht->tbl, ht));
+ tbl = rht_dereference(ht->tbl, ht);
+ if (free_fn) {
+ for (i = 0; i < tbl->size; i++) {
+ struct rhash_head *pos, *next;
+
+ for (pos = rht_dereference(tbl->buckets[i], ht),
+ next = !rht_is_a_nulls(pos) ?
+ rht_dereference(pos->next, ht) : NULL;
+ !rht_is_a_nulls(pos);
+ pos = next,
+ next = !rht_is_a_nulls(pos) ?
+ rht_dereference(pos->next, ht) : NULL)
+ free_fn(rht_obj(ht, pos), arg);
+ }
+ }
+
+ bucket_table_free(tbl);
mutex_unlock(&ht->mutex);
}
+EXPORT_SYMBOL_GPL(rhashtable_free_and_destroy);
+
+void rhashtable_destroy(struct rhashtable *ht)
+{
+ return rhashtable_free_and_destroy(ht, NULL, NULL);
+}
EXPORT_SYMBOL_GPL(rhashtable_destroy);
diff --git a/net/netfilter/nft_hash.c b/net/netfilter/nft_hash.c
index 2986f1d..ad29965 100644
--- a/net/netfilter/nft_hash.c
+++ b/net/netfilter/nft_hash.c
@@ -187,26 +187,15 @@ static int nft_hash_init(const struct nft_set *set,
return rhashtable_init(priv, ¶ms);
}
-static void nft_hash_destroy(const struct nft_set *set)
+static void nft_free_element(void *ptr, void *arg)
{
- struct rhashtable *priv = nft_set_priv(set);
- const struct bucket_table *tbl;
- struct nft_hash_elem *he;
- struct rhash_head *pos, *next;
- unsigned int i;
-
- /* Stop an eventual async resizing */
- priv->being_destroyed = true;
- mutex_lock(&priv->mutex);
-
- tbl = rht_dereference(priv->tbl, priv);
- for (i = 0; i < tbl->size; i++) {
- rht_for_each_entry_safe(he, pos, next, tbl, i, node)
- nft_hash_elem_destroy(set, he);
- }
- mutex_unlock(&priv->mutex);
+ nft_hash_elem_destroy((const struct nft_set *)arg, ptr);
+}
- rhashtable_destroy(priv);
+static void nft_hash_destroy(const struct nft_set *set)
+{
+ rhashtable_free_and_destroy(nft_set_priv(set), nft_free_element,
+ (void *)set);
}
static bool nft_hash_estimate(const struct nft_set_desc *desc, u32 features,
--
1.9.3
--
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