Btrfs: Fix per root used space accounting

The bytes_used field in root item was originally planned to
trace the amount of used data and tree blocks. But it never
worked right since we can't trace freeing of data accurately.
This patch changes it to only trace the amount of tree blocks.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 75b31caade29..b2acc79f1b34 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -501,13 +501,16 @@ static int update_cowonly_root(struct btrfs_trans_handle *trans,
 {
         int ret;
         u64 old_root_bytenr;
+        u64 old_root_used;
         struct btrfs_root *tree_root = root->fs_info->tree_root;
 
+        old_root_used = btrfs_root_used(&root->root_item);
         btrfs_write_dirty_block_groups(trans, root);
 
         while (1) {
                 old_root_bytenr = btrfs_root_bytenr(&root->root_item);
-                if (old_root_bytenr == root->node->start)
+                if (old_root_bytenr == root->node->start &&
+                    old_root_used == btrfs_root_used(&root->root_item))
                         break;
 
                 btrfs_set_root_node(&root->root_item, root->node);
@@ -516,6 +519,7 @@ static int update_cowonly_root(struct btrfs_trans_handle *trans,
                                         &root->root_item);
                 BUG_ON(ret);
 
+                old_root_used = btrfs_root_used(&root->root_item);
                 ret = btrfs_write_dirty_block_groups(trans, root);
                 BUG_ON(ret);
         }