b=17511

r=johann,adilger

- removes deadlock possibility by disabling rehash in hash_del() operations and moving hash_add()
  out of spin_locks when calling. Hash table has own mechanisms for protecting its structures and it
  also has hash_add_unique() method for using in concurrent run contexts;

  - fixed missed lh_put() in hash_add_unique() which led to extra refs in some cases (extra ref to
  export) and inability to cleanup;

  - fixed __lustre_hash_set_theta() which set @max theta into ->lh_min_theta;

  - in lustre_hash_rehash_size() disable rehash also for the case when new and old hash sizes equal
  in corner cases (max_size or min_size). Before this fix it could be possible to do needless
  rehashes when size is actually did not change but we do this expensive operation;

  - disable rehash in hash_add_unique() if no actual add happened since entry with the same key is
  already found in the table;

  - some cleanups in hash table code;

diff --git a/lustre/lov/lov_pool.c b/lustre/lov/lov_pool.c
index eb3f0d4..19361a8 100644 (file)
--- a/lustre/lov/lov_pool.c
+++ b/lustre/lov/lov_pool.c
@@ -400,18 +400,16 @@ int lov_pool_new(struct obd_device *obd, char *poolname)
                 GOTO(out_err, rc);
         }
 
-        spin_lock(&obd->obd_dev_lock);
-        /* check if pool already exists */
-        if (lustre_hash_lookup(lov->lov_pools_hash_body, poolname) != NULL) {
-                spin_unlock(&obd->obd_dev_lock);
+        INIT_HLIST_NODE(&new_pool->pool_hash);
+        rc = lustre_hash_add_unique(lov->lov_pools_hash_body, poolname,
+                                    &new_pool->pool_hash);
+        if (rc) {
                 lov_ost_pool_free(&new_pool->pool_rr.lqr_pool);
                 lov_ost_pool_free(&new_pool->pool_obds);
                 GOTO(out_err, rc = -EEXIST);
         }
 
-        INIT_HLIST_NODE(&new_pool->pool_hash);
-        lustre_hash_add_unique(lov->lov_pools_hash_body, poolname,
-                               &new_pool->pool_hash);
+        spin_lock(&obd->obd_dev_lock);
         list_add_tail(&new_pool->pool_list, &lov->lov_pool_list);
         lov->lov_pool_count++;
         spin_unlock(&obd->obd_dev_lock);