mon,cephfs: require confirmation when changing max_mds on unhealthy cluster

User must pass the confirmation flag (--yes-i-really-mean-it) to change
the value of CephFS setting variable "max_mds" when the Ceph cluster is
unhealthy.

This measure was decided upon to prevent users from changing "max_mds"
as a measure of troubleshotoing unhealthy cluster.

Fixes: https://tracker.ceph.com/issues/66301
Signed-off-by: Rishabh Dave <[email protected]>

Author: rishabh-d-dave

src/mon/FSCommands.cc

@@ -385,6 +385,17 @@ class SetHandler : public FileSystemCommandHandler
       return -EINVAL;
     }
 
+  bool confirm = false;
+  cmd_getval(cmdmap, "yes_i_really_mean_it", confirm);
+  if (var == "max_mds" && !confirm && mon->mdsmon()->has_any_health_warning()) {
+    ss << "One or more file system health warnings are present. Modifying "
+       << "the file system setting variable \"max_mds\" may not help "
+       << "troubleshoot or recover from these warnings and may further "
+       << "destabilize the system. If you really wish to proceed, run "
+       << "again with --yes-i-really-mean-it";
+    return -EPERM;
+  }
+
     return set_val(mon, fsmap, op, cmdmap, ss, fsp->get_fscid(), var, val);
   }
 };

src/mon/MDSMonitor.cc

@@ -1557,6 +1557,13 @@ bool MDSMonitor::has_health_warnings(vector<mds_metric_t> warnings)
   return false;
 }
 
+bool MDSMonitor::has_any_health_warning()
+{
+  return std::any_of(
+    pending_daemon_health.begin(), pending_daemon_health.end(),
+    [](auto& it) { return !it.second.metrics.empty() ? true : false; });
+}
+
 int MDSMonitor::filesystem_command(
     FSMap &fsmap,
     MonOpRequestRef op,

src/mon/MDSMonitor.h

@@ -53,6 +53,7 @@ class MDSMonitor : public PaxosService, public PaxosFSMap, protected CommandHand
   bool prepare_update(MonOpRequestRef op) override;
   bool should_propose(double& delay) override;
   bool has_health_warnings(std::vector<mds_metric_t> warnings);
+  bool has_any_health_warning();
 
   bool should_print_status() const {
     auto& fs = get_fsmap();