extent-tree.c:5328

5321                         if (offset) {
5322                                 /* we have a block, we're done */
5323                                 spin_unlock(&last_ptr->refill_lock);
5324                                 goto checks;
5325                         }
5326
5327 refill_cluster:
5328                         BUG_ON(used_block_group != block_group);
5329
5330                         /* If we are on LOOP_NO_EMPTY_SIZE, we can't
5331                          * set up a new clusters, so lets just skip it
5332                          * and let the allocator find whatever block
5333                          * it can find.  If we reach this point, we
5334                          * will have tried the cluster allocator
5335                          * plenty of times and not have found
5336                          * anything, so we are likely way too
5337                          * fragmented for the clustering stuff to find
5338                          * anything.
5339                          *
5340                          * However, if the cluster is taken from the
5341                          * current block group, release the cluster
5342                          * first, so that we stand a better chance of
5343                          * succeeding in the unclustered
5344                          * allocation.  */
5345                         if (loop >= LOOP_NO_EMPTY_SIZE &&
5346                             last_ptr->block_group != block_group) {
5347                                 spin_unlock(&last_ptr->refill_lock);
5348                                 goto unclustered_alloc;
5349                         }