rhashtable: Move future_tbl into struct bucket_table

This patch moves future_tbl to open up the possibility of having
multiple rehashes on the same table.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 16 deletions

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index ff4ea1704546..9d53a46dcca9 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -207,8 +207,9 @@ static bool rht_shrink_below_30(const struct rhashtable *ht,
 
 static int rhashtable_rehash_one(struct rhashtable *ht, unsigned old_hash)
 {
-        struct bucket_table *new_tbl = rht_dereference(ht->future_tbl, ht);
         struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
+        struct bucket_table *new_tbl =
+                rht_dereference(old_tbl->future_tbl, ht) ?: old_tbl;
         struct rhash_head __rcu **pprev = &old_tbl->buckets[old_hash];
         int err = -ENOENT;
         struct rhash_head *head, *next, *entry;
@@ -273,10 +274,8 @@ static void rhashtable_rehash(struct rhashtable *ht,
 
         /* Make insertions go into the new, empty table right away. Deletions
          * and lookups will be attempted in both tables until we synchronize.
-         * The synchronize_rcu() guarantees for the new table to be picked up
-         * so no new additions go into the old table while we relink.
          */
-        rcu_assign_pointer(ht->future_tbl, new_tbl);
+        rcu_assign_pointer(old_tbl->future_tbl, new_tbl);
 
         /* Ensure the new table is visible to readers. */
         smp_wmb();
@@ -400,7 +399,7 @@ static bool __rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj,
          * also grab the bucket lock in old_tbl because until the
          * rehash completes ht->tbl won't be changed.
          */
-        tbl = rht_dereference_rcu(ht->future_tbl, ht);
+        tbl = rht_dereference_rcu(old_tbl->future_tbl, ht) ?: old_tbl;
         if (tbl != old_tbl) {
                 hash = head_hashfn(ht, tbl, obj);
                 spin_lock_nested(bucket_lock(tbl, hash), SINGLE_DEPTH_NESTING);
@@ -525,7 +524,7 @@ bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *obj)
          * visible then that guarantees the entry to still be in
          * old_tbl if it exists.
          */
-        tbl = rht_dereference_rcu(ht->future_tbl, ht);
+        tbl = rht_dereference_rcu(old_tbl->future_tbl, ht) ?: old_tbl;
         if (!ret && old_tbl != tbl)
                 ret = __rhashtable_remove(ht, tbl, obj);
 
@@ -599,7 +598,7 @@ EXPORT_SYMBOL_GPL(rhashtable_lookup);
 void *rhashtable_lookup_compare(struct rhashtable *ht, const void *key,
                                 bool (*compare)(void *, void *), void *arg)
 {
-        const struct bucket_table *tbl, *old_tbl;
+        const struct bucket_table *tbl;
         struct rhash_head *he;
         u32 hash;
 
@@ -618,9 +617,8 @@ restart:
         /* Ensure we see any new tables. */
         smp_rmb();
 
-        old_tbl = tbl;
-        tbl = rht_dereference_rcu(ht->future_tbl, ht);
-        if (unlikely(tbl != old_tbl))
+        tbl = rht_dereference_rcu(tbl->future_tbl, ht);
+        if (unlikely(tbl))
                 goto restart;
         rcu_read_unlock();
 
@@ -830,14 +828,13 @@ next:
                 iter->skip = 0;
         }
 
-        iter->walker->tbl = rht_dereference_rcu(ht->future_tbl, ht);
-        if (iter->walker->tbl != tbl) {
+        iter->walker->tbl = rht_dereference_rcu(tbl->future_tbl, ht);
+        if (iter->walker->tbl) {
                 iter->slot = 0;
                 iter->skip = 0;
                 return ERR_PTR(-EAGAIN);
         }
 
-        iter->walker->tbl = NULL;
         iter->p = NULL;
 
 out:
@@ -865,8 +862,7 @@ void rhashtable_walk_stop(struct rhashtable_iter *iter)
         ht = iter->ht;
 
         mutex_lock(&ht->mutex);
-        if (rht_dereference(ht->tbl, ht) == tbl ||
-            rht_dereference(ht->future_tbl, ht) == tbl)
+        if (tbl->rehash < tbl->size)
                 list_add(&iter->walker->list, &tbl->walkers);
         else
                 iter->walker->tbl = NULL;
@@ -961,7 +957,6 @@ int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params)
         atomic_set(&ht->nelems, 0);
 
         RCU_INIT_POINTER(ht->tbl, tbl);
-        RCU_INIT_POINTER(ht->future_tbl, tbl);
 
         INIT_WORK(&ht->run_work, rht_deferred_worker);