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authorFlorian Westphal <fw@strlen.de>2017-04-16 03:55:09 +0300
committerDavid S. Miller <davem@davemloft.net>2017-04-18 20:49:14 +0300
commit5f8ddeab10ce45d3d3de8ae7ea8811512845c497 (patch)
tree41fe63ac1297c07eee1ea140ee4ddceae417e5d5 /include/linux/rhashtable.h
parent3a9ca1e2cba02365d93a8cf7bdda04c05a637f1b (diff)
downloadlinux-5f8ddeab10ce45d3d3de8ae7ea8811512845c497.tar.xz
rhashtable: remove insecure_elasticity
commit 83e7e4ce9e93c3 ("mac80211: Use rhltable instead of rhashtable") removed the last user that made use of 'insecure_elasticity' parameter, i.e. the default of 16 is used everywhere. Replace it with a constant. Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux/rhashtable.h')
-rw-r--r--include/linux/rhashtable.h21
1 files changed, 16 insertions, 5 deletions
diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h
index e507290cd2c7..ae87dcdf52d2 100644
--- a/include/linux/rhashtable.h
+++ b/include/linux/rhashtable.h
@@ -49,6 +49,21 @@
/* Base bits plus 1 bit for nulls marker */
#define RHT_HASH_RESERVED_SPACE (RHT_BASE_BITS + 1)
+/* Maximum chain length before rehash
+ *
+ * The maximum (not average) chain length grows with the size of the hash
+ * table, at a rate of (log N)/(log log N).
+ *
+ * The value of 16 is selected so that even if the hash table grew to
+ * 2^32 you would not expect the maximum chain length to exceed it
+ * unless we are under attack (or extremely unlucky).
+ *
+ * As this limit is only to detect attacks, we don't need to set it to a
+ * lower value as you'd need the chain length to vastly exceed 16 to have
+ * any real effect on the system.
+ */
+#define RHT_ELASTICITY 16u
+
struct rhash_head {
struct rhash_head __rcu *next;
};
@@ -114,7 +129,6 @@ struct rhashtable;
* @max_size: Maximum size while expanding
* @min_size: Minimum size while shrinking
* @nulls_base: Base value to generate nulls marker
- * @insecure_elasticity: Set to true to disable chain length checks
* @automatic_shrinking: Enable automatic shrinking of tables
* @locks_mul: Number of bucket locks to allocate per cpu (default: 128)
* @hashfn: Hash function (default: jhash2 if !(key_len % 4), or jhash)
@@ -130,7 +144,6 @@ struct rhashtable_params {
unsigned int max_size;
unsigned int min_size;
u32 nulls_base;
- bool insecure_elasticity;
bool automatic_shrinking;
size_t locks_mul;
rht_hashfn_t hashfn;
@@ -143,7 +156,6 @@ struct rhashtable_params {
* @tbl: Bucket table
* @nelems: Number of elements in table
* @key_len: Key length for hashfn
- * @elasticity: Maximum chain length before rehash
* @p: Configuration parameters
* @rhlist: True if this is an rhltable
* @run_work: Deferred worker to expand/shrink asynchronously
@@ -154,7 +166,6 @@ struct rhashtable {
struct bucket_table __rcu *tbl;
atomic_t nelems;
unsigned int key_len;
- unsigned int elasticity;
struct rhashtable_params p;
bool rhlist;
struct work_struct run_work;
@@ -726,7 +737,7 @@ slow_path:
return rhashtable_insert_slow(ht, key, obj);
}
- elasticity = ht->elasticity;
+ elasticity = RHT_ELASTICITY;
pprev = rht_bucket_insert(ht, tbl, hash);
data = ERR_PTR(-ENOMEM);
if (!pprev)