4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Ben Hutchings <ben.hutchings@xxxxxxxxxxxxxxx>
Extracted from commit ca26893f05e8 "rhashtable: Add rhlist interface".
Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben.hutchings@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/linux/rhashtable.h | 69 +++++++++++++++++++++++++++++++++------------
1 file changed, 52 insertions(+), 17 deletions(-)
--- a/include/linux/rhashtable.h
+++ b/include/linux/rhashtable.h
@@ -515,18 +515,8 @@ static inline int rhashtable_compare(str
return memcmp(ptr + ht->p.key_offset, arg->key, ht->p.key_len);
}
-/**
- * rhashtable_lookup_fast - search hash table, inlined version
- * @ht: hash table
- * @key: the pointer to the key
- * @params: hash table parameters
- *
- * Computes the hash value for the key and traverses the bucket chain looking
- * for a entry with an identical key. The first matching entry is returned.
- *
- * Returns the first entry on which the compare function returned true.
- */
-static inline void *rhashtable_lookup_fast(
+/* Internal function, do not use. */
+static inline struct rhash_head *__rhashtable_lookup(
struct rhashtable *ht, const void *key,
const struct rhashtable_params params)
{
@@ -538,8 +528,6 @@ static inline void *rhashtable_lookup_fa
struct rhash_head *he;
unsigned int hash;
- rcu_read_lock();
-
tbl = rht_dereference_rcu(ht->tbl, ht);
restart:
hash = rht_key_hashfn(ht, tbl, key, params);
@@ -548,8 +536,7 @@ restart:
params.obj_cmpfn(&arg, rht_obj(ht, he)) :
rhashtable_compare(&arg, rht_obj(ht, he)))
continue;
- rcu_read_unlock();
- return rht_obj(ht, he);
+ return he;
}
/* Ensure we see any new tables. */
@@ -558,11 +545,59 @@ restart:
tbl = rht_dereference_rcu(tbl->future_tbl, ht);
if (unlikely(tbl))
goto restart;
- rcu_read_unlock();
return NULL;
}
+/**
+ * rhashtable_lookup - search hash table
+ * @ht: hash table
+ * @key: the pointer to the key
+ * @params: hash table parameters
+ *
+ * Computes the hash value for the key and traverses the bucket chain looking
+ * for a entry with an identical key. The first matching entry is returned.
+ *
+ * This must only be called under the RCU read lock.
+ *
+ * Returns the first entry on which the compare function returned true.
+ */
+static inline void *rhashtable_lookup(
+ struct rhashtable *ht, const void *key,
+ const struct rhashtable_params params)
+{
+ struct rhash_head *he = __rhashtable_lookup(ht, key, params);
+
+ return he ? rht_obj(ht, he) : NULL;
+}
+
+/**
+ * rhashtable_lookup_fast - search hash table, without RCU read lock
+ * @ht: hash table
+ * @key: the pointer to the key
+ * @params: hash table parameters
+ *
+ * Computes the hash value for the key and traverses the bucket chain looking
+ * for a entry with an identical key. The first matching entry is returned.
+ *
+ * Only use this function when you have other mechanisms guaranteeing
+ * that the object won't go away after the RCU read lock is released.
+ *
+ * Returns the first entry on which the compare function returned true.
+ */
+static inline void *rhashtable_lookup_fast(
+ struct rhashtable *ht, const void *key,
+ const struct rhashtable_params params)
+{
+ void *obj;
+
+ rcu_read_lock();
+ obj = rhashtable_lookup(ht, key, params);
+ rcu_read_unlock();
+
+ return obj;
+}
+
/* Internal function, please use rhashtable_insert_fast() instead. This
* function returns the existing element already in hashes in there is a clash,
* otherwise it returns an error via ERR_PTR().
