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Date: Wed, 7 Jan 2015 13:41:54 +0800
From: Ying Xue <ying.xue@...driver.com>
To: <tgraf@...g.ch>
CC: <davem@...emloft.net>, <jon.maloy@...csson.com>,
<Paul.Gortmaker@...driver.com>, <erik.hugne@...csson.com>,
<netdev@...r.kernel.org>, <tipc-discussion@...ts.sourceforge.net>
Subject: [PATCH net-next v2 3/7] rhashtable: involve rhashtable_lookup_insert routine
Involve a new function called rhashtable_lookup_insert() which makes
lookup and insertion atomic under bucket lock protection, helping us
avoid to introduce an extra lock when we search and insert an object
into hash table.
Signed-off-by: Ying Xue <ying.xue@...driver.com>
Signed-off-by: Thomas Graf <tgraf@...g.ch>
Acked-by: Thomas Graf <tgraf@...g.ch>
---
include/linux/rhashtable.h | 1 +
lib/rhashtable.c | 97 +++++++++++++++++++++++++++++++++++++-------
2 files changed, 83 insertions(+), 15 deletions(-)
diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h
index de1459c7..73c913f 100644
--- a/include/linux/rhashtable.h
+++ b/include/linux/rhashtable.h
@@ -168,6 +168,7 @@ int rhashtable_shrink(struct rhashtable *ht);
void *rhashtable_lookup(struct rhashtable *ht, const void *key);
void *rhashtable_lookup_compare(struct rhashtable *ht, const void *key,
bool (*compare)(void *, void *), void *arg);
+bool rhashtable_lookup_insert(struct rhashtable *ht, struct rhash_head *obj);
void rhashtable_destroy(struct rhashtable *ht);
diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 2000685..4430233 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -505,8 +505,26 @@ static void rhashtable_wakeup_worker(struct rhashtable *ht)
schedule_delayed_work(&ht->run_work, 0);
}
+static void __rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj,
+ struct bucket_table *tbl, u32 hash)
+{
+ struct rhash_head *head = rht_dereference_bucket(tbl->buckets[hash],
+ tbl, hash);
+
+ if (rht_is_a_nulls(head))
+ INIT_RHT_NULLS_HEAD(obj->next, ht, hash);
+ else
+ RCU_INIT_POINTER(obj->next, head);
+
+ rcu_assign_pointer(tbl->buckets[hash], obj);
+
+ atomic_inc(&ht->nelems);
+
+ rhashtable_wakeup_worker(ht);
+}
+
/**
- * rhashtable_insert - insert object into hash hash table
+ * rhashtable_insert - insert object into hash table
* @ht: hash table
* @obj: pointer to hash head inside object
*
@@ -523,7 +541,6 @@ static void rhashtable_wakeup_worker(struct rhashtable *ht)
void rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj)
{
struct bucket_table *tbl;
- struct rhash_head *head;
spinlock_t *lock;
unsigned hash;
@@ -534,19 +551,9 @@ void rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj)
lock = bucket_lock(tbl, hash);
spin_lock_bh(lock);
- head = rht_dereference_bucket(tbl->buckets[hash], tbl, hash);
- if (rht_is_a_nulls(head))
- INIT_RHT_NULLS_HEAD(obj->next, ht, hash);
- else
- RCU_INIT_POINTER(obj->next, head);
-
- rcu_assign_pointer(tbl->buckets[hash], obj);
+ __rhashtable_insert(ht, obj, tbl, hash);
spin_unlock_bh(lock);
- atomic_inc(&ht->nelems);
-
- rhashtable_wakeup_worker(ht);
-
rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(rhashtable_insert);
@@ -560,7 +567,7 @@ EXPORT_SYMBOL_GPL(rhashtable_insert);
* walk the bucket chain upon removal. The removal operation is thus
* considerable slow if the hash table is not correctly sized.
*
- * Will automatically shrink the table via rhashtable_expand() if the the
+ * Will automatically shrink the table via rhashtable_expand() if the
* shrink_decision function specified at rhashtable_init() returns true.
*
* The caller must ensure that no concurrent table mutations occur. It is
@@ -641,7 +648,7 @@ static bool rhashtable_compare(void *ptr, void *arg)
* for a entry with an identical key. The first matching entry is returned.
*
* This lookup function may only be used for fixed key hash table (key_len
- * paramter set). It will BUG() if used inappropriately.
+ * parameter set). It will BUG() if used inappropriately.
*
* Lookups may occur in parallel with hashtable mutations and resizing.
*/
@@ -702,6 +709,66 @@ restart:
}
EXPORT_SYMBOL_GPL(rhashtable_lookup_compare);
+/**
+ * rhashtable_lookup_insert - lookup and insert object into hash table
+ * @ht: hash table
+ * @obj: pointer to hash head inside object
+ *
+ * Locks down the bucket chain in both the old and new table if a resize
+ * is in progress to ensure that writers can't remove from the old table
+ * and can't insert to the new table during the atomic operation of search
+ * and insertion. Searches for duplicates in both the old and new table if
+ * a resize is in progress.
+ *
+ * This lookup function may only be used for fixed key hash table (key_len
+ * parameter set). It will BUG() if used inappropriately.
+ *
+ * It is safe to call this function from atomic context.
+ *
+ * Will trigger an automatic deferred table resizing if the size grows
+ * beyond the watermark indicated by grow_decision() which can be passed
+ * to rhashtable_init().
+ */
+bool rhashtable_lookup_insert(struct rhashtable *ht, struct rhash_head *obj)
+{
+ struct bucket_table *new_tbl, *old_tbl;
+ spinlock_t *new_bucket_lock, *old_bucket_lock;
+ u32 new_hash, old_hash;
+ bool success = true;
+
+ BUG_ON(!ht->p.key_len);
+
+ rcu_read_lock();
+
+ old_tbl = rht_dereference_rcu(ht->tbl, ht);
+ old_hash = head_hashfn(ht, old_tbl, obj);
+ old_bucket_lock = bucket_lock(old_tbl, old_hash);
+ spin_lock_bh(old_bucket_lock);
+
+ new_tbl = rht_dereference_rcu(ht->future_tbl, ht);
+ new_hash = head_hashfn(ht, new_tbl, obj);
+ new_bucket_lock = bucket_lock(new_tbl, new_hash);
+ if (unlikely(old_tbl != new_tbl))
+ spin_lock_bh_nested(new_bucket_lock, RHT_LOCK_NESTED);
+
+ if (rhashtable_lookup(ht, rht_obj(ht, obj) + ht->p.key_offset)) {
+ success = false;
+ goto exit;
+ }
+
+ __rhashtable_insert(ht, obj, new_tbl, new_hash);
+
+exit:
+ if (unlikely(old_tbl != new_tbl))
+ spin_unlock_bh(new_bucket_lock);
+ spin_unlock_bh(old_bucket_lock);
+
+ rcu_read_unlock();
+
+ return success;
+}
+EXPORT_SYMBOL_GPL(rhashtable_lookup_insert);
+
static size_t rounded_hashtable_size(struct rhashtable_params *params)
{
return max(roundup_pow_of_two(params->nelem_hint * 4 / 3),
--
1.7.9.5
--
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