Illumos #3129, #3130

[zfs.git] / module / zfs / dsl_dir.c

diff --git a/module/zfs/dsl_dir.c b/module/zfs/dsl_dir.c
index d615832..97b38d2 100644 (file)
--- a/module/zfs/dsl_dir.c
+++ b/module/zfs/dsl_dir.c
@@ -460,12 +460,14 @@ dsl_dir_destroy_check(void *arg1, void *arg2, dmu_tx_t *tx)
        /*
         * There should be exactly two holds, both from
         * dsl_dataset_destroy: one on the dd directory, and one on its
-        * head ds.  Otherwise, someone is trying to lookup something
-        * inside this dir while we want to destroy it.  The
-        * config_rwlock ensures that nobody else opens it after we
-        * check.
+        * head ds.  If there are more holds, then a concurrent thread is
+        * performing a lookup inside this dir while we're trying to destroy
+        * it.  To minimize this possibility, we perform this check only
+        * in syncing context and fail the operation if we encounter
+        * additional holds.  The dp_config_rwlock ensures that nobody else
+        * opens it after we check.
         */
-       if (dmu_buf_refcount(dd->dd_dbuf) > 2)
+       if (dmu_tx_is_syncing(tx) && dmu_buf_refcount(dd->dd_dbuf) > 2)
                return (EBUSY);
 
        err = zap_count(mos, dd->dd_phys->dd_child_dir_zapobj, &count);