rhashtable: remove indirection for grow/shrink decision functions

Currently, all real users of rhashtable default their grow and shrink
decision functions to rht_grow_above_75() and rht_shrink_below_30(),
so that there's currently no need to have this explicitly selectable.

It can/should be generic and private inside rhashtable until a real
use case pops up. Since we can make this private, we'll save us this
additional indirection layer and can improve insertion/deletion time
as well.

Reference: http://patchwork.ozlabs.org/patch/443040/
Suggested-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 18 insertions, 39 deletions

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index bcf119bfdef4..090641db4c0d 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -247,26 +247,24 @@ static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
  * @ht:         hash table
  * @new_size:   new table size
  */
-bool rht_grow_above_75(const struct rhashtable *ht, size_t new_size)
+static bool rht_grow_above_75(const struct rhashtable *ht, size_t new_size)
 {
         /* Expand table when exceeding 75% load */
         return atomic_read(&ht->nelems) > (new_size / 4 * 3) &&
                (!ht->p.max_shift || atomic_read(&ht->shift) < ht->p.max_shift);
 }
-EXPORT_SYMBOL_GPL(rht_grow_above_75);
 
 /**
  * rht_shrink_below_30 - returns true if nelems < 0.3 * table-size
  * @ht:         hash table
  * @new_size:   new table size
  */
-bool rht_shrink_below_30(const struct rhashtable *ht, size_t new_size)
+static bool rht_shrink_below_30(const struct rhashtable *ht, size_t new_size)
 {
         /* Shrink table beneath 30% load */
         return atomic_read(&ht->nelems) < (new_size * 3 / 10) &&
                (atomic_read(&ht->shift) > ht->p.min_shift);
 }
-EXPORT_SYMBOL_GPL(rht_shrink_below_30);
 
 static void lock_buckets(struct bucket_table *new_tbl,
                          struct bucket_table *old_tbl, unsigned int hash)
@@ -528,40 +526,19 @@ static void rht_deferred_worker(struct work_struct *work)
         list_for_each_entry(walker, &ht->walkers, list)
                 walker->resize = true;
 
-        if (ht->p.grow_decision && ht->p.grow_decision(ht, tbl->size))
+        if (rht_grow_above_75(ht, tbl->size))
                 rhashtable_expand(ht);
-        else if (ht->p.shrink_decision && ht->p.shrink_decision(ht, tbl->size))
+        else if (rht_shrink_below_30(ht, tbl->size))
                 rhashtable_shrink(ht);
-
 unlock:
         mutex_unlock(&ht->mutex);
 }
 
-static void rhashtable_probe_expand(struct rhashtable *ht)
-{
-        const struct bucket_table *new_tbl = rht_dereference_rcu(ht->future_tbl, ht);
-        const struct bucket_table *tbl = rht_dereference_rcu(ht->tbl, ht);
-
-        /* Only adjust the table if no resizing is currently in progress. */
-        if (tbl == new_tbl && ht->p.grow_decision &&
-            ht->p.grow_decision(ht, tbl->size))
-                schedule_work(&ht->run_work);
-}
-
-static void rhashtable_probe_shrink(struct rhashtable *ht)
-{
-        const struct bucket_table *new_tbl = rht_dereference_rcu(ht->future_tbl, ht);
-        const struct bucket_table *tbl = rht_dereference_rcu(ht->tbl, ht);
-
-        /* Only adjust the table if no resizing is currently in progress. */
-        if (tbl == new_tbl && ht->p.shrink_decision &&
-            ht->p.shrink_decision(ht, tbl->size))
-                schedule_work(&ht->run_work);
-}
-
 static void __rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj,
-                                struct bucket_table *tbl, u32 hash)
+                                struct bucket_table *tbl,
+                                const struct bucket_table *old_tbl, u32 hash)
 {
+        bool no_resize_running = tbl == old_tbl;
         struct rhash_head *head;
 
         hash = rht_bucket_index(tbl, hash);
@@ -577,8 +554,8 @@ static void __rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj,
         rcu_assign_pointer(tbl->buckets[hash], obj);
 
         atomic_inc(&ht->nelems);
-
-        rhashtable_probe_expand(ht);
+        if (no_resize_running && rht_grow_above_75(ht, tbl->size))
+                schedule_work(&ht->run_work);
 }
 
 /**
@@ -608,7 +585,7 @@ void rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj)
         hash = obj_raw_hashfn(ht, rht_obj(ht, obj));
 
         lock_buckets(tbl, old_tbl, hash);
-        __rhashtable_insert(ht, obj, tbl, hash);
+        __rhashtable_insert(ht, obj, tbl, old_tbl, hash);
         unlock_buckets(tbl, old_tbl, hash);
 
         rcu_read_unlock();
@@ -690,8 +667,11 @@ found:
         unlock_buckets(new_tbl, old_tbl, new_hash);
 
         if (ret) {
+                bool no_resize_running = new_tbl == old_tbl;
+
                 atomic_dec(&ht->nelems);
-                rhashtable_probe_shrink(ht);
+                if (no_resize_running && rht_shrink_below_30(ht, new_tbl->size))
+                        schedule_work(&ht->run_work);
         }
 
         rcu_read_unlock();
@@ -861,7 +841,7 @@ bool rhashtable_lookup_compare_insert(struct rhashtable *ht,
                 goto exit;
         }
 
-        __rhashtable_insert(ht, obj, new_tbl, new_hash);
+        __rhashtable_insert(ht, obj, new_tbl, old_tbl, new_hash);
 
 exit:
         unlock_buckets(new_tbl, old_tbl, new_hash);
@@ -1123,8 +1103,7 @@ int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params)
         if (!ht->p.hash_rnd)
                 get_random_bytes(&ht->p.hash_rnd, sizeof(ht->p.hash_rnd));
 
-        if (ht->p.grow_decision || ht->p.shrink_decision)
-                INIT_WORK(&ht->run_work, rht_deferred_worker);
+        INIT_WORK(&ht->run_work, rht_deferred_worker);
 
         return 0;
 }
@@ -1142,8 +1121,7 @@ void rhashtable_destroy(struct rhashtable *ht)
 {
         ht->being_destroyed = true;
 
-        if (ht->p.grow_decision || ht->p.shrink_decision)
-                cancel_work_sync(&ht->run_work);
+        cancel_work_sync(&ht->run_work);
 
         mutex_lock(&ht->mutex);
         bucket_table_free(rht_dereference(ht->tbl, ht));
diff --git a/lib/test_rhashtable.c b/lib/test_rhashtable.c
index f9e9d734446a..67c7593d1dd6 100644
--- a/lib/test_rhashtable.c
+++ b/lib/test_rhashtable.c
@@ -201,6 +201,7 @@ static int __init test_rht_init(void)
                 .key_offset = offsetof(struct test_obj, value),
                 .key_len = sizeof(int),
                 .hashfn = jhash,
+                .max_shift = 1, /* we expand/shrink manually here */
                 .nulls_base = (3U << RHT_BASE_SHIFT),
         };
         int err;