diff options
| -rw-r--r-- | include/linux/rhashtable.h | 5 | ||||
| -rw-r--r-- | lib/rhashtable.c | 27 |
2 files changed, 14 insertions, 18 deletions
diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h index ed7562ad4ca0..1695378b3c5b 100644 --- a/include/linux/rhashtable.h +++ b/include/linux/rhashtable.h @@ -56,6 +56,7 @@ struct rhash_head { * @locks: Array of spinlocks protecting individual buckets * @walkers: List of active walkers * @rcu: RCU structure for freeing the table + * @future_tbl: Table under construction during rehashing * @buckets: size * hash buckets */ struct bucket_table { @@ -68,6 +69,8 @@ struct bucket_table { struct list_head walkers; struct rcu_head rcu; + struct bucket_table __rcu *future_tbl; + struct rhash_head __rcu *buckets[] ____cacheline_aligned_in_smp; }; @@ -105,7 +108,6 @@ struct rhashtable_params { /** * struct rhashtable - Hash table handle * @tbl: Bucket table - * @future_tbl: Table under construction during expansion/shrinking * @nelems: Number of elements in table * @p: Configuration parameters * @run_work: Deferred worker to expand/shrink asynchronously @@ -114,7 +116,6 @@ struct rhashtable_params { */ struct rhashtable { struct bucket_table __rcu *tbl; - struct bucket_table __rcu *future_tbl; atomic_t nelems; bool being_destroyed; struct rhashtable_params p; 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); |