MDSMonitor: check for duplicated fs creation *before* multiple-fs creation

If we check for creating an FS with one already existing first, we will
reject (with EINVAL) duplicate attempts to create the same FS with
the same params. That makes it non-idempotent, which is bad!

Signed-off-by: Greg Farnum <gfarnum@redhat.com>

diff --git a/src/mon/MDSMonitor.cc b/src/mon/MDSMonitor.cc
index a680be73c71550f61dd0d1198f44ec482a6fe2bc..b41bc0115ae6725b6291c7bc57b165ae499f0e25 100644 (file)
--- a/src/mon/MDSMonitor.cc
+++ b/src/mon/MDSMonitor.cc
@@ -1568,14 +1568,6 @@ int MDSMonitor::management_command(
         return -EINVAL;
     }
 
-    if (pending_fsmap.any_filesystems()
-        && !pending_fsmap.get_enable_multiple()) {
-      ss << "Creation of multiple filesystems is disabled.  To enable "
-            "this experimental feature, use 'ceph fs flag set enable_multiple "
-            "true'";
-      return -EINVAL;
-    }
-
     if (pending_fsmap.get_filesystem(fs_name)) {
       auto fs = pending_fsmap.get_filesystem(fs_name);
       if (*(fs->mds_map.data_pools.begin()) == data
@@ -1589,6 +1581,14 @@ int MDSMonitor::management_command(
       }
     }
 
+    if (pending_fsmap.any_filesystems()
+        && !pending_fsmap.get_enable_multiple()) {
+      ss << "Creation of multiple filesystems is disabled.  To enable "
+            "this experimental feature, use 'ceph fs flag set enable_multiple "
+            "true'";
+      return -EINVAL;
+    }
+
     pg_pool_t const *data_pool = mon->osdmon()->osdmap.get_pg_pool(data);
     assert(data_pool != NULL);  // Checked it existed above
     pg_pool_t const *metadata_pool = mon->osdmon()->osdmap.get_pg_pool(metadata);