osd/scrub: skip reserving replicas for high-priority scrubs

(The primary side of the required changes)

Signed-off-by: Ronen Friedman <rfriedma@redhat.com>

Author: ronen-fr

src/osd/scrubber/pg_scrubber.cc

@@ -800,7 +800,7 @@ void PgScrubber::cancel_callback(scrubber_callback_cancel_token_t token)
   m_osds->sleep_timer.cancel_event(token);
 }
 
-LogChannelRef &PgScrubber::get_clog() const
+LogChannelRef& PgScrubber::get_clog() const
 {
   return m_osds->clog;
 }
@@ -810,6 +810,11 @@ int PgScrubber::get_whoami() const
   return m_osds->whoami;
 }
 
+[[nodiscard]] bool PgScrubber::is_high_priority() const
+{
+  return m_flags.required;
+}
+
 /*
  * The selected range is set directly into 'm_start' and 'm_end'
  * setting:

src/osd/scrubber/pg_scrubber.h

@@ -402,6 +402,9 @@ class PgScrubber : public ScrubPgIF,
     return m_pg->recovery_state.is_primary();
   }
 
+  /// is this scrub more than just regular periodic scrub?
+  [[nodiscard]] bool is_high_priority() const final;
+
   void set_state_name(const char* name) final
   {
     m_fsm_state_name = name;

src/osd/scrubber/scrub_machine_lstnr.h

@@ -229,4 +229,7 @@ struct ScrubMachineListener {
   // temporary interface (to be discarded in a follow-up PR)
   /// set the 'resources_failure' flag in the scrub-job object
   virtual void flag_reservations_failure() = 0;
+
+  /// is this scrub more than just regular periodic scrub?
+  [[nodiscard]] virtual bool is_high_priority() const = 0;
 };

src/osd/scrubber/scrub_reservations.cc

@@ -49,12 +49,17 @@ ReplicaReservations::ReplicaReservations(ScrubMachineListener& scrbr)
       });
 
   m_next_to_request = m_sorted_secondaries.cbegin();
-  // send out the 1'st request (unless we have no replicas)
-  send_next_reservation_or_complete();
-
-  m_slow_response_warn_timeout =
-      m_scrubber.get_pg_cct()->_conf.get_val<milliseconds>(
-	  "osd_scrub_slow_reservation_response");
+  if (m_scrubber.is_high_priority()) {
+    // for high-priority scrubs (i.e. - user-initiated), no reservations are
+    // needed.
+    dout(10) << "high-priority scrub - no reservations needed" << dendl;
+  } else {
+    // send out the 1'st request (unless we have no replicas)
+    send_next_reservation_or_complete();
+    m_slow_response_warn_timeout =
+	m_scrubber.get_pg_cct()->_conf.get_val<milliseconds>(
+	    "osd_scrub_slow_reservation_response");
+  }
 }
 
 void ReplicaReservations::release_all()