Btrfs: Don't empty the middle buffer in push_nodes_for_insert

Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index ac999f0..319f9f9 100644 (file)
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -29,7 +29,7 @@ static int split_leaf(struct btrfs_trans_handle *trans, struct btrfs_root
                      struct btrfs_path *path, int data_size, int extend);
 static int push_node_left(struct btrfs_trans_handle *trans,
                          struct btrfs_root *root, struct extent_buffer *dst,
-                         struct extent_buffer *src);
+                         struct extent_buffer *src, int empty);
 static int balance_node_right(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root,
                              struct extent_buffer *dst_buf,
@@ -789,7 +789,7 @@ static int balance_level(struct btrfs_trans_handle *trans,
        /* first, try to make some room in the middle buffer */
        if (left) {
                orig_slot += btrfs_header_nritems(left);
-               wret = push_node_left(trans, root, left, mid);
+               wret = push_node_left(trans, root, left, mid, 0);
                if (wret < 0)
                        ret = wret;
                if (btrfs_header_nritems(mid) < 2)
@@ -800,7 +800,7 @@ static int balance_level(struct btrfs_trans_handle *trans,
         * then try to empty the right most buffer into the middle
         */
        if (right) {
-               wret = push_node_left(trans, root, mid, right);
+               wret = push_node_left(trans, root, mid, right, 1);
                if (wret < 0 && wret != -ENOSPC)
                        ret = wret;
                if (btrfs_header_nritems(right) == 0) {
@@ -941,7 +941,7 @@ static int noinline push_nodes_for_insert(struct btrfs_trans_handle *trans,
                                wret = 1;
                        else {
                                wret = push_node_left(trans, root,
-                                                     left, mid);
+                                                     left, mid, 0);
                        }
                }
                if (wret < 0)
@@ -1239,7 +1239,7 @@ static int fixup_low_keys(struct btrfs_trans_handle *trans,
  */
 static int push_node_left(struct btrfs_trans_handle *trans,
                          struct btrfs_root *root, struct extent_buffer *dst,
-                         struct extent_buffer *src)
+                         struct extent_buffer *src, int empty)
 {
        int push_items = 0;
        int src_nritems;
@@ -1252,12 +1252,17 @@ static int push_node_left(struct btrfs_trans_handle *trans,
        WARN_ON(btrfs_header_generation(src) != trans->transid);
        WARN_ON(btrfs_header_generation(dst) != trans->transid);
 
+       if (!empty && src_nritems <= 2)
+               return 1;
+
        if (push_items <= 0) {
                return 1;
        }
 
-       if (src_nritems < push_items)
-               push_items = src_nritems;
+       if (empty)
+               push_items = min(src_nritems, push_items);
+       else
+               push_items = min(src_nritems - 2, push_items);
 
        copy_extent_buffer(dst, src,
                           btrfs_node_key_ptr_offset(dst_nritems),