LU-4152 mdt: Don't enqueue two locks on the same resource

[fs/lustre-release.git] / lustre / mdt / mdt_open.c

diff --git a/lustre/mdt/mdt_open.c b/lustre/mdt/mdt_open.c
index a95cef8..4e4a2c3 100644 (file)
--- a/lustre/mdt/mdt_open.c
+++ b/lustre/mdt/mdt_open.c
@@ -1276,6 +1276,15 @@ static int mdt_object_open_lock(struct mdt_thread_info *info,
                        ", open_flags = "LPO64"\n",
                        PFID(mdt_object_fid(obj)), open_flags);
 
+               /* We cannot enqueue another lock for the same resource we
+                * already have a lock for, due to mechanics of waiting list
+                * iterating in ldlm, see LU-3601.
+                * As such we'll drop the open lock we just got above here,
+                * it's ok not to have this open lock as it's main purpose is to
+                * flush unused cached client open handles. */
+               if (lustre_handle_is_used(&lhc->mlh_reg_lh))
+                       mdt_object_unlock(info, obj, lhc, 1);
+
                LASSERT(!try_layout);
                mdt_lock_handle_init(ll);
                mdt_lock_reg_init(ll, LCK_EX);
@@ -1365,12 +1374,13 @@ static void mdt_object_open_unlock(struct mdt_thread_info *info,
                rc = 1;
        }
 
-       if (rc != 0) {
+       if (rc != 0 || !lustre_handle_is_used(&lhc->mlh_reg_lh)) {
                struct ldlm_reply       *ldlm_rep;
 
                ldlm_rep = req_capsule_server_get(info->mti_pill, &RMF_DLM_REP);
                mdt_clear_disposition(info, ldlm_rep, DISP_OPEN_LOCK);
-               mdt_object_unlock(info, obj, lhc, 1);
+               if (lustre_handle_is_used(&lhc->mlh_reg_lh))
+                       mdt_object_unlock(info, obj, lhc, 1);
        }
        RETURN_EXIT;
 }