rhashtable: Prevent spurious EBUSY errors on insertion

[linux-2.6-block.git] / lib / rhashtable.c

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index a54ff8949f9116184631414086a9fa2d956c8031..2ff7ed91663ae4fd105c24ad98454a51c329cf86 100644 (file)
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -389,33 +389,31 @@ static bool rhashtable_check_elasticity(struct rhashtable *ht,
        return false;
 }
 
-int rhashtable_insert_rehash(struct rhashtable *ht)
+int rhashtable_insert_rehash(struct rhashtable *ht,
+                            struct bucket_table *tbl)
 {
        struct bucket_table *old_tbl;
        struct bucket_table *new_tbl;
-       struct bucket_table *tbl;
        unsigned int size;
        int err;
 
        old_tbl = rht_dereference_rcu(ht->tbl, ht);
-       tbl = rhashtable_last_table(ht, old_tbl);
 
        size = tbl->size;
 
+       err = -EBUSY;
+
        if (rht_grow_above_75(ht, tbl))
                size *= 2;
        /* Do not schedule more than one rehash */
        else if (old_tbl != tbl)
-               return -EBUSY;
+               goto fail;
+
+       err = -ENOMEM;
 
        new_tbl = bucket_table_alloc(ht, size, GFP_ATOMIC);
-       if (new_tbl == NULL) {
-               /* Schedule async resize/rehash to try allocation
-                * non-atomic context.
-                */
-               schedule_work(&ht->run_work);
-               return -ENOMEM;
-       }
+       if (new_tbl == NULL)
+               goto fail;
 
        err = rhashtable_rehash_attach(ht, tbl, new_tbl);
        if (err) {
@@ -426,12 +424,24 @@ int rhashtable_insert_rehash(struct rhashtable *ht)
                schedule_work(&ht->run_work);
 
        return err;
+
+fail:
+       /* Do not fail the insert if someone else did a rehash. */
+       if (likely(rcu_dereference_raw(tbl->future_tbl)))
+               return 0;
+
+       /* Schedule async rehash to retry allocation in process context. */
+       if (err == -ENOMEM)
+               schedule_work(&ht->run_work);
+
+       return err;
 }
 EXPORT_SYMBOL_GPL(rhashtable_insert_rehash);
 
-int rhashtable_insert_slow(struct rhashtable *ht, const void *key,
-                          struct rhash_head *obj,
-                          struct bucket_table *tbl)
+struct bucket_table *rhashtable_insert_slow(struct rhashtable *ht,
+                                           const void *key,
+                                           struct rhash_head *obj,
+                                           struct bucket_table *tbl)
 {
        struct rhash_head *head;
        unsigned int hash;
@@ -467,7 +477,12 @@ int rhashtable_insert_slow(struct rhashtable *ht, const void *key,
 exit:
        spin_unlock(rht_bucket_lock(tbl, hash));
 
-       return err;
+       if (err == 0)
+               return NULL;
+       else if (err == -EAGAIN)
+               return tbl;
+       else
+               return ERR_PTR(err);
 }
 EXPORT_SYMBOL_GPL(rhashtable_insert_slow);