2 files changed, 127 insertions, 0 deletions

diff --git a/fs/btrfs/delayed-ref.c b/fs/btrfs/delayed-ref.c
index bd9b63b..2f41580 100644
--- a/fs/btrfs/delayed-ref.c
+++ b/fs/btrfs/delayed-ref.c
@@ -197,6 +197,119 @@ static inline void drop_delayed_ref(struct btrfs_trans_handle *trans,
 		trans->delayed_ref_updates--;
 }
 
+static bool merge_ref(struct btrfs_trans_handle *trans,
+		      struct btrfs_delayed_ref_root *delayed_refs,
+		      struct btrfs_delayed_ref_head *head,
+		      struct btrfs_delayed_ref_node *ref,
+		      u64 seq)
+{
+	struct btrfs_delayed_ref_node *next;
+	bool done = false;
+
+	next = list_first_entry(&head->ref_list, struct btrfs_delayed_ref_node,
+				list);
+	while (!done && &next->list != &head->ref_list) {
+		int mod;
+		struct btrfs_delayed_ref_node *next2;
+
+		next2 = list_next_entry(next, list);
+
+		if (next == ref)
+			goto next;
+
+		if (seq && next->seq >= seq)
+			goto next;
+
+		if (next->type != ref->type || next->no_quota != ref->no_quota)
+			goto next;
+
+		if ((ref->type == BTRFS_TREE_BLOCK_REF_KEY ||
+		     ref->type == BTRFS_SHARED_BLOCK_REF_KEY) &&
+		    comp_tree_refs(btrfs_delayed_node_to_tree_ref(ref),
+				   btrfs_delayed_node_to_tree_ref(next),
+				   ref->type))
+			goto next;
+		if ((ref->type == BTRFS_EXTENT_DATA_REF_KEY ||
+		     ref->type == BTRFS_SHARED_DATA_REF_KEY) &&
+		    comp_data_refs(btrfs_delayed_node_to_data_ref(ref),
+				   btrfs_delayed_node_to_data_ref(next)))
+			goto next;
+
+		if (ref->action == next->action) {
+			mod = next->ref_mod;
+		} else {
+			if (ref->ref_mod < next->ref_mod) {
+				swap(ref, next);
+				done = true;
+			}
+			mod = -next->ref_mod;
+		}
+
+		drop_delayed_ref(trans, delayed_refs, head, next);
+		ref->ref_mod += mod;
+		if (ref->ref_mod == 0) {
+			drop_delayed_ref(trans, delayed_refs, head, ref);
+			done = true;
+		} else {
+			/*
+			 * Can't have multiples of the same ref on a tree block.
+			 */
+			WARN_ON(ref->type == BTRFS_TREE_BLOCK_REF_KEY ||
+				ref->type == BTRFS_SHARED_BLOCK_REF_KEY);
+		}
+next:
+		next = next2;
+	}
+
+	return done;
+}
+
+void btrfs_merge_delayed_refs(struct btrfs_trans_handle *trans,
+			      struct btrfs_fs_info *fs_info,
+			      struct btrfs_delayed_ref_root *delayed_refs,
+			      struct btrfs_delayed_ref_head *head)
+{
+	struct btrfs_delayed_ref_node *ref;
+	u64 seq = 0;
+
+	assert_spin_locked(&head->lock);
+
+	if (list_empty(&head->ref_list))
+		return;
+
+	/* We don't have too many refs to merge for data. */
+	if (head->is_data)
+		return;
+
+	spin_lock(&fs_info->tree_mod_seq_lock);
+	if (!list_empty(&fs_info->tree_mod_seq_list)) {
+		struct seq_list *elem;
+
+		elem = list_first_entry(&fs_info->tree_mod_seq_list,
+					struct seq_list, list);
+		seq = elem->seq;
+	}
+	spin_unlock(&fs_info->tree_mod_seq_lock);
+
+	ref = list_first_entry(&head->ref_list, struct btrfs_delayed_ref_node,
+			       list);
+	while (&ref->list != &head->ref_list) {
+		if (seq && ref->seq >= seq)
+			goto next;
+
+		if (merge_ref(trans, delayed_refs, head, ref, seq)) {
+			if (list_empty(&head->ref_list))
+				break;
+			ref = list_first_entry(&head->ref_list,
+					       struct btrfs_delayed_ref_node,
+					       list);
+			continue;
+		}
+next:
+		ref = list_next_entry(ref, list);
+	}
+}
+
 int btrfs_check_delayed_seq(struct btrfs_fs_info *fs_info,
 			    struct btrfs_delayed_ref_root *delayed_refs,
 			    u64 seq)
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 92fdbc6..c0f30f5 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2502,7 +2502,21 @@ static noinline int __btrfs_run_delayed_refs(struct btrfs_trans_handle *trans,
 			}
 		}
 
+		/*
+		 * We need to try and merge add/drops of the same ref since we
+		 * can run into issues with relocate dropping the implicit ref
+		 * and then it being added back again before the drop can
+		 * finish.  If we merged anything we need to re-loop so we can
+		 * get a good ref.
+		 * Or we can get node references of the same type that weren't
+		 * merged when created due to bumps in the tree mod seq, and
+		 * we need to merge them to prevent adding an inline extent
+		 * backref before dropping it (triggering a BUG_ON at
+		 * insert_inline_extent_backref()).
+		 */
 		spin_lock(&locked_ref->lock);
+		btrfs_merge_delayed_refs(trans, fs_info, delayed_refs,
+					 locked_ref);
 
 		/*
 		 * locked_ref is the head node, so we have to go one