rculfhash: merge duplicated code for bucket lookup

[ Edit by Mathieu Desnoyers: also remove unnecessary lookups that end up
  returning an already looked up node. Same behavior is guaranteed
  because the hash and size stay invariant across retry. ]

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/rculfhash.c b/rculfhash.c
index 2e338f132e66bb5c6a1271f9cdf2bc8730055aea..c7b9ea895cf6594d11a9ef8a56a461ba3bc2ae7d 100644 (file)
--- a/rculfhash.c
+++ b/rculfhash.c
@@ -716,6 +716,22 @@ unsigned long _uatomic_max(unsigned long *ptr, unsigned long v)
        return v;
 }
 
+static
+struct _cds_lfht_node *lookup_bucket(struct cds_lfht *ht, unsigned long size,
+               unsigned long hash)
+{
+       unsigned long index, order;
+
+       assert(size > 0);
+       index = hash & (size - 1);
+       order = get_count_order_ulong(index + 1);
+
+       dbg_printf("lookup hash %lu index %lu order %lu aridx %lu\n",
+                  hash, index, order, index & (!order ? 0 : ((1UL << (order - 1)) - 1)));
+
+       return &ht->t.tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order - 1)) - 1))];
+}
+
 /*
  * Remove all logically deleted nodes from a bucket up to a certain node key.
  */
@@ -772,7 +788,6 @@ int _cds_lfht_replace(struct cds_lfht *ht, unsigned long size,
        struct cds_lfht_node *dummy, *old_next;
        struct _cds_lfht_node *lookup;
        int flagged = 0;
-       unsigned long hash, index, order;
 
        if (!old_node)  /* Return -ENOENT if asked to replace NULL node */
                goto end;
@@ -817,11 +832,7 @@ int _cds_lfht_replace(struct cds_lfht *ht, unsigned long size,
         * lookup for the node, and remove it (along with any other
         * logically removed node) if found.
         */
-       hash = bit_reverse_ulong(old_node->p.reverse_hash);
-       assert(size > 0);
-       index = hash & (size - 1);
-       order = get_count_order_ulong(index + 1);
-       lookup = &ht->t.tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order - 1)) - 1))];
+       lookup = lookup_bucket(ht, size, bit_reverse_ulong(old_node->p.reverse_hash));
        dummy = (struct cds_lfht_node *) lookup;
        _cds_lfht_gc_bucket(dummy, new_node);
 end:
@@ -846,7 +857,6 @@ struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht,
        struct cds_lfht_node *iter_prev, *iter, *next, *new_node, *new_next,
                        *dummy_node, *return_node;
        struct _cds_lfht_node *lookup;
-       unsigned long hash, index, order;
 
        assert(!is_dummy(node));
        assert(!is_removed(node));
@@ -855,7 +865,7 @@ struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht,
                node->p.next = flag_dummy(get_end());
                return node;    /* Initial first add (head) */
        }
-       hash = bit_reverse_ulong(node->p.reverse_hash);
+       lookup = lookup_bucket(ht, size, bit_reverse_ulong(node->p.reverse_hash));
        for (;;) {
                uint32_t chain_len = 0;
 
@@ -863,9 +873,6 @@ struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht,
                 * iter_prev points to the non-removed node prior to the
                 * insert location.
                 */
-               index = hash & (size - 1);
-               order = get_count_order_ulong(index + 1);
-               lookup = &ht->t.tbl[order]->nodes[index & ((!order ? 0 : (1UL << (order - 1))) - 1)];
                iter_prev = (struct cds_lfht_node *) lookup;
                /* We can always skip the dummy node initially */
                iter = rcu_dereference(iter_prev->p.next);
@@ -941,9 +948,6 @@ struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht,
        }
 gc_end:
        /* Garbage collect logically removed nodes in the bucket */
-       index = hash & (size - 1);
-       order = get_count_order_ulong(index + 1);
-       lookup = &ht->t.tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order - 1)) - 1))];
        dummy_node = (struct cds_lfht_node *) lookup;
        _cds_lfht_gc_bucket(dummy_node, node);
 end:
@@ -958,7 +962,6 @@ int _cds_lfht_del(struct cds_lfht *ht, unsigned long size,
        struct cds_lfht_node *dummy, *next, *old;
        struct _cds_lfht_node *lookup;
        int flagged = 0;
-       unsigned long hash, index, order;
 
        if (!node)      /* Return -ENOENT if asked to delete NULL node */
                goto end;
@@ -989,11 +992,7 @@ int _cds_lfht_del(struct cds_lfht *ht, unsigned long size,
         * the node, and remove it (along with any other logically removed node)
         * if found.
         */
-       hash = bit_reverse_ulong(node->p.reverse_hash);
-       assert(size > 0);
-       index = hash & (size - 1);
-       order = get_count_order_ulong(index + 1);
-       lookup = &ht->t.tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order - 1)) - 1))];
+       lookup = lookup_bucket(ht, size, bit_reverse_ulong(node->p.reverse_hash));
        dummy = (struct cds_lfht_node *) lookup;
        _cds_lfht_gc_bucket(dummy, node);
 end:
@@ -1318,17 +1317,13 @@ void cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len,
 {
        struct cds_lfht_node *node, *next, *dummy_node;
        struct _cds_lfht_node *lookup;
-       unsigned long hash, reverse_hash, index, order, size;
+       unsigned long hash, reverse_hash, size;
 
        hash = ht->hash_fct(key, key_len, ht->hash_seed);
        reverse_hash = bit_reverse_ulong(hash);
 
        size = rcu_dereference(ht->t.size);
-       index = hash & (size - 1);
-       order = get_count_order_ulong(index + 1);
-       lookup = &ht->t.tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order - 1))) - 1)];
-       dbg_printf("lookup hash %lu index %lu order %lu aridx %lu\n",
-                  hash, index, order, index & (!order ? 0 : ((1UL << (order - 1)) - 1)));
+       lookup = lookup_bucket(ht, size, hash);
        dummy_node = (struct cds_lfht_node *) lookup;
        /* We can always skip the dummy node initially */
        node = rcu_dereference(dummy_node->p.next);