From 4dff97e69005ea90266f3e3dda295264e854c15d Mon Sep 17 00:00:00 2001 From: Josef Bacik Date: Thu, 20 Aug 2020 11:46:06 -0400 Subject: [PATCH] btrfs: introduce BTRFS_NESTING_SPLIT for split blocks 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 Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/ctree.c | 4 ++-- fs/btrfs/locking.h | 9 +++++++++ 2 files changed, 11 insertions(+), 2 deletions(-) diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index ecf8bf240d73..884c8b5a0e62 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -3537,7 +3537,7 @@ 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); @@ -4324,7 +4324,7 @@ again: 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); diff --git a/fs/btrfs/locking.h b/fs/btrfs/locking.h index 16563bc486c7..a6b59808e046 100644 --- a/fs/btrfs/locking.h +++ b/fs/btrfs/locking.h @@ -52,6 +52,15 @@ 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