LU-4801 ldlm: discard l_lock from struct ldlm_lock.

[fs/lustre-release.git] / lustre / ldlm / ldlm_lock.c

diff --git a/lustre/ldlm/ldlm_lock.c b/lustre/ldlm/ldlm_lock.c
index 8fbd76f..48906c5 100644 (file)
--- a/lustre/ldlm/ldlm_lock.c
+++ b/lustre/ldlm/ldlm_lock.c
@@ -469,8 +469,7 @@ static struct ldlm_lock *ldlm_lock_new(struct ldlm_resource *resource)
        if (lock == NULL)
                RETURN(NULL);
 
-       spin_lock_init(&lock->l_lock);
-       lock->l_resource = resource;
+       RCU_INIT_POINTER(lock->l_resource, resource);
        lu_ref_add(&resource->lr_reference, "lock", lock);
 
        refcount_set(&lock->l_handle.h_ref, 2);
@@ -487,24 +486,24 @@ static struct ldlm_lock *ldlm_lock_new(struct ldlm_resource *resource)
        INIT_HLIST_NODE(&lock->l_exp_hash);
        INIT_HLIST_NODE(&lock->l_exp_flock_hash);
 
-        lprocfs_counter_incr(ldlm_res_to_ns(resource)->ns_stats,
-                             LDLM_NSS_LOCKS);
+       lprocfs_counter_incr(ldlm_res_to_ns(resource)->ns_stats,
+                            LDLM_NSS_LOCKS);
        INIT_HLIST_NODE(&lock->l_handle.h_link);
        class_handle_hash(&lock->l_handle, lock_handle_owner);
 
-        lu_ref_init(&lock->l_reference);
-        lu_ref_add(&lock->l_reference, "hash", lock);
+       lu_ref_init(&lock->l_reference);
+       lu_ref_add(&lock->l_reference, "hash", lock);
        lock->l_callback_timestamp = 0;
        lock->l_activity = 0;
 
 #if LUSTRE_TRACKS_LOCK_EXP_REFS
        INIT_LIST_HEAD(&lock->l_exp_refs_link);
-        lock->l_exp_refs_nr = 0;
-        lock->l_exp_refs_target = NULL;
+       lock->l_exp_refs_nr = 0;
+       lock->l_exp_refs_target = NULL;
 #endif
        INIT_LIST_HEAD(&lock->l_exp_list);
 
-        RETURN(lock);
+       RETURN(lock);
 }
 
 /**
@@ -544,12 +543,13 @@ int ldlm_lock_change_resource(struct ldlm_namespace *ns, struct ldlm_lock *lock,
 
         lu_ref_add(&newres->lr_reference, "lock", lock);
         /*
-         * To flip the lock from the old to the new resource, lock, oldres and
-         * newres have to be locked. Resource spin-locks are nested within
-         * lock->l_lock, and are taken in the memory address order to avoid
-         * dead-locks.
+        * To flip the lock from the old to the new resource, oldres
+        * and newres have to be locked. Resource spin-locks are taken
+        * in the memory address order to avoid dead-locks.
+        * As this is the only circumstance where ->l_resource
+        * can change, and this cannot race with itself, it is safe
+        * to access lock->l_resource without being careful about locking.
          */
-       spin_lock(&lock->l_lock);
         oldres = lock->l_resource;
         if (oldres < newres) {
                 lock_res(oldres);
@@ -560,9 +560,9 @@ int ldlm_lock_change_resource(struct ldlm_namespace *ns, struct ldlm_lock *lock,
         }
         LASSERT(memcmp(new_resid, &oldres->lr_name,
                        sizeof oldres->lr_name) != 0);
-        lock->l_resource = newres;
+       rcu_assign_pointer(lock->l_resource, newres);
         unlock_res(oldres);
-        unlock_res_and_lock(lock);
+       unlock_res(newres);
 
         /* ...and the flowers are still standing! */
         lu_ref_del(&oldres->lr_reference, "lock", lock);
@@ -2764,15 +2764,11 @@ void _ldlm_lock_debug(struct ldlm_lock *lock,
        struct va_format vaf;
         char *nid = "local";
 
-       /* on server-side resource of lock doesn't change */
-       if ((lock->l_flags & LDLM_FL_NS_SRV) != 0) {
-               if (lock->l_resource != NULL)
-                       resource = ldlm_resource_getref(lock->l_resource);
-       } else if (spin_trylock(&lock->l_lock)) {
-               if (lock->l_resource != NULL)
-                       resource = ldlm_resource_getref(lock->l_resource);
-               spin_unlock(&lock->l_lock);
-       }
+       rcu_read_lock();
+       resource = rcu_dereference(lock->l_resource);
+       if (resource && !atomic_inc_not_zero(&resource->lr_refcount))
+               resource = NULL;
+       rcu_read_unlock();
 
         va_start(args, fmt);
        vaf.fmt = fmt;