MDEV-37755 ilist::pop_back() removes sentinel

include/ilist.h

@@ -185,6 +185,9 @@ template <class T, class Tag= void> class ilist
     ListNode *prev= pos.node_->prev;
     ListNode *next= pos.node_->next;
 
+    DBUG_ASSERT(prev->next == pos.node_);
+    DBUG_ASSERT(next->prev == pos.node_);
+
     prev->next= next;
     next->prev= prev;
 
@@ -198,7 +201,7 @@ template <class T, class Tag= void> class ilist
   }
 
   void push_back(reference value) noexcept { insert(end(), value); }
-  void pop_back() noexcept { erase(end()); }
+  void pop_back() noexcept { erase(--end()); }
 
   void push_front(reference value) noexcept { insert(begin(), value); }
   void pop_front() noexcept { erase(begin()); }

storage/innobase/fil/fil0fil.cc

@@ -896,7 +896,7 @@ bool fil_space_free(ulint id, bool x_latched) noexcept
 		mysql_mutex_assert_owner(&log_sys.mutex);
 
 		if (space->max_lsn != 0) {
-			ut_d(space->max_lsn = 0);
+			space->max_lsn = 0;
 			fil_system.named_spaces.remove(*space);
 		}
 
@@ -1595,6 +1595,18 @@ fil_space_t *fil_space_t::drop(ulint id, pfs_os_file_t *detached_handle)
     *detached_handle = handle;
   else
     os_file_close(handle);
+
+  /* The above mnt.commit_file() call should remove the space from
+  fil_system.named_spaces, but some pending operations can push it back
+  to the container again. */
+  mysql_mutex_lock(&log_sys.mutex);
+  if (space->max_lsn != 0)
+  {
+    space->max_lsn= 0;
+    fil_system.named_spaces.remove(*space);
+  }
+  mysql_mutex_unlock(&log_sys.mutex);
+
   return space;
 }
 
@@ -1617,12 +1629,6 @@ void fil_close_tablespace(ulint id) noexcept
 	while (buf_flush_list_space(space));
 
 	space->x_unlock();
-	mysql_mutex_lock(&log_sys.mutex);
-	if (space->max_lsn != 0) {
-		ut_d(space->max_lsn = 0);
-		fil_system.named_spaces.remove(*space);
-	}
-	mysql_mutex_unlock(&log_sys.mutex);
 	fil_space_free_low(space);
 }
 
@@ -1631,7 +1637,7 @@ pfs_os_file_t fil_delete_tablespace(ulint id) noexcept
   ut_ad(!is_system_tablespace(id));
   pfs_os_file_t handle= OS_FILE_CLOSED;
   if (fil_space_t *space= fil_space_t::drop(id, &handle))
-    fil_space_free_low(space);
+      fil_space_free_low(space);
   return handle;
 }
 

storage/innobase/mtr/mtr0mtr.cc

@@ -375,7 +375,7 @@ bool mtr_t::commit_file(fil_space_t &space, const char *name)
 
   if (!name && space.max_lsn)
   {
-    ut_d(space.max_lsn= 0);
+    space.max_lsn= 0;
     fil_system.named_spaces.remove(space);
   }