[PATCH] btrfs: fix node balancing condition in balance_level()

[Sun YangKai <sunk67188@gmail.com>]

Commit cfbb9308463f ("Btrfs: balance btree more often") intended to
trigger node balancing when node utilization drops below 50% (capacity/2)
by modifying the condition in setup_nodes_for_search(). However, an
undetected early return condition in balance_level() prevented this
behavior from taking effect.

The early return condition:
    if (btrfs_header_nritems(mid) > BTRFS_NODEPTRS_PER_BLOCK(fs_info) / 4)
        return 0;

caused balance_level() to abort when nodes were still more than 25% full,
effectively maintaining the original 25% threshold. This unintended
behavior persisted for over a decade. Since setup_nodes_for_search() is
the sole caller of balance_level(), remove the obsolete early return
condition to:

1. Align with the original intent of commit cfbb9308463f ("Btrfs: balance btree more often")
2. Allow proper node balancing at the 50% utilization threshold
3. Improve btree performance by more frequent node compaction

Fixes: cfbb9308463f ("Btrfs: balance btree more often")
Signed-off-by: Sun YangKai <sunk67188@gmail.com>
---
 fs/btrfs/ctree.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index acd85e317564..8cc52c8b38f3 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -939,9 +939,6 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
 		}
 		return 0;
 	}
-	if (btrfs_header_nritems(mid) >
-	    BTRFS_NODEPTRS_PER_BLOCK(fs_info) / 4)
-		return 0;
 
 	if (pslot) {
 		left = btrfs_read_node_slot(parent, pslot - 1);
-- 
2.50.1