btrfs: remove clone_backref_node() from relocation

Since we no longer maintain backref cache across transactions, and this
is only called when we're creating the reloc root for a newly created
snapshot in the transaction critical section, we will end up doing a
bunch of work that will just get thrown away when we start the
transaction in the relocation loop.  Delete this code as it no longer
does anything for us.

Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 4cad2540e3ae38b8245c4a3aa867afc1e44cdfda..cb98ddd825d4b56771c8bab9624bd2c3ddafc93b 100644 (file)
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -469,92 +469,6 @@ out:
        return node;
 }
 
-/*
- * helper to add backref node for the newly created snapshot.
- * the backref node is created by cloning backref node that
- * corresponds to root of source tree
- */
-static int clone_backref_node(struct btrfs_trans_handle *trans,
-                             struct reloc_control *rc,
-                             const struct btrfs_root *src,
-                             struct btrfs_root *dest)
-{
-       struct btrfs_root *reloc_root = src->reloc_root;
-       struct btrfs_backref_cache *cache = &rc->backref_cache;
-       struct btrfs_backref_node *node = NULL;
-       struct btrfs_backref_node *new_node;
-       struct btrfs_backref_edge *edge;
-       struct btrfs_backref_edge *new_edge;
-       struct rb_node *rb_node;
-
-       rb_node = rb_simple_search(&cache->rb_root, src->commit_root->start);
-       if (rb_node) {
-               node = rb_entry(rb_node, struct btrfs_backref_node, rb_node);
-               if (node->detached)
-                       node = NULL;
-               else
-                       BUG_ON(node->new_bytenr != reloc_root->node->start);
-       }
-
-       if (!node) {
-               rb_node = rb_simple_search(&cache->rb_root,
-                                          reloc_root->commit_root->start);
-               if (rb_node) {
-                       node = rb_entry(rb_node, struct btrfs_backref_node,
-                                       rb_node);
-                       BUG_ON(node->detached);
-               }
-       }
-
-       if (!node)
-               return 0;
-
-       new_node = btrfs_backref_alloc_node(cache, dest->node->start,
-                                           node->level);
-       if (!new_node)
-               return -ENOMEM;
-
-       new_node->lowest = node->lowest;
-       new_node->checked = 1;
-       new_node->root = btrfs_grab_root(dest);
-       ASSERT(new_node->root);
-
-       if (!node->lowest) {
-               list_for_each_entry(edge, &node->lower, list[UPPER]) {
-                       new_edge = btrfs_backref_alloc_edge(cache);
-                       if (!new_edge)
-                               goto fail;
-
-                       btrfs_backref_link_edge(new_edge, edge->node[LOWER],
-                                               new_node, LINK_UPPER);
-               }
-       } else {
-               list_add_tail(&new_node->lower, &cache->leaves);
-       }
-
-       rb_node = rb_simple_insert(&cache->rb_root, new_node->bytenr,
-                                  &new_node->rb_node);
-       if (rb_node)
-               btrfs_backref_panic(trans->fs_info, new_node->bytenr, -EEXIST);
-
-       if (!new_node->lowest) {
-               list_for_each_entry(new_edge, &new_node->lower, list[UPPER]) {
-                       list_add_tail(&new_edge->list[LOWER],
-                                     &new_edge->node[LOWER]->upper);
-               }
-       }
-       return 0;
-fail:
-       while (!list_empty(&new_node->lower)) {
-               new_edge = list_entry(new_node->lower.next,
-                                     struct btrfs_backref_edge, list[UPPER]);
-               list_del(&new_edge->list[UPPER]);
-               btrfs_backref_free_edge(cache, new_edge);
-       }
-       btrfs_backref_free_node(cache, new_node);
-       return -ENOMEM;
-}
-
 /*
  * helper to add 'address of tree root -> reloc tree' mapping
  */
@@ -4485,10 +4399,7 @@ int btrfs_reloc_post_snapshot(struct btrfs_trans_handle *trans,
                return ret;
        }
        new_root->reloc_root = btrfs_grab_root(reloc_root);
-
-       if (rc->create_reloc_tree)
-               ret = clone_backref_node(trans, rc, root, reloc_root);
-       return ret;
+       return 0;
 }
 
 /*