@@ -3473,7 +3473,7 @@ static noinline int split_node(struct btrfs_trans_handle *trans,
btrfs_node_key(c, &disk_key, mid);
split = alloc_tree_block_no_bg_flush(trans, root, 0, &disk_key, level,
- c->start, 0, BTRFS_NESTING_NORMAL);
+ c->start, 0, BTRFS_NESTING_SPLIT);
if (IS_ERR(split))
return PTR_ERR(split);
@@ -4250,7 +4250,7 @@ static noinline int split_leaf(struct btrfs_trans_handle *trans,
btrfs_item_key(l, &disk_key, mid);
right = alloc_tree_block_no_bg_flush(trans, root, 0, &disk_key, 0,
- l->start, 0, BTRFS_NESTING_NORMAL);
+ l->start, 0, BTRFS_NESTING_SPLIT);
if (IS_ERR(right))
return PTR_ERR(right);
@@ -47,6 +47,15 @@ enum btrfs_lock_nesting {
BTRFS_NESTING_LEFT_COW,
BTRFS_NESTING_RIGHT_COW,
+ /*
+ * When splitting we may push nodes to the left or right, but still use
+ * the subsequent nodes in our path, keeping our locks on those adjacent
+ * blocks. Thus when we go to allocate a new split block we've already
+ * used up all of our available subclasses, so this subclass exists to
+ * handle this case where we need to allocate a new split block.
+ */
+ BTRFS_NESTING_SPLIT,
+
/*
* We are limited to MAX_LOCKDEP_SUBLCLASSES number of subclasses, so
* add this in here and add a static_assert to keep us from going over
If we are splitting a leaf/node, we could do something like the following lock(leaf) BTRFS_NESTING_NORMAL lock(left) BTRFS_NESTING_LEFT + BTRFS_NESTING_COW push from leaf -> left reset path to point to left split left allocate new block, lock block BTRFS_NESTING_SPLIT at the new block point we need to have a different nesting level, because we have already used either BTRFS_NESTING_LEFT or BTRFS_NESTING_RIGHT when pushing items from the original leaf into the adjacent leaves. Signed-off-by: Josef Bacik <josef@toxicpanda.com> --- fs/btrfs/ctree.c | 4 ++-- fs/btrfs/locking.h | 9 +++++++++ 2 files changed, 11 insertions(+), 2 deletions(-)