[btrfs-devel][patch]fix get_bh and brelse issues when drop snapshot

[Yan Zheng]

Hello,

When drop_progress isn't zero, the root->node's usage count is
increased in btrfs_search_slot. Therefore, the get_bh in the body of
while loop is redundant in most cases. (this change is in accordance
with btrfs_defrag_leaves).

The second change is decrease root->node's usage count when drop a snapshot.

Regards
YZ

diff -r 29b8cc7794ac extent-tree.c
--- a/extent-tree.c	Thu Sep 20 14:14:42 2007 -0400
+++ b/extent-tree.c	Sun Sep 23 12:35:00 2007 +0800
@@ -1483,6 +1483,7 @@ int btrfs_drop_snapshot(struct btrfs_tra
 	level = btrfs_header_level(btrfs_buffer_header(root->node));
 	orig_level = level;
 	if (btrfs_disk_key_objectid(&root_item->drop_progress) == 0) {
+		get_bh(root->node);
 		path->nodes[level] = root->node;
 		path->slots[level] = 0;
 	} else {
@@ -1516,7 +1517,6 @@ int btrfs_drop_snapshot(struct btrfs_tra
 		if (wret < 0)
 			ret = wret;
 		ret = -EAGAIN;
-		get_bh(root->node);
 		break;
 	}
 	for (i = 0; i <= orig_level; i++) {
diff -r 29b8cc7794ac transaction.c
--- a/transaction.c	Thu Sep 20 14:14:42 2007 -0400
+++ b/transaction.c	Sun Sep 23 12:35:00 2007 +0800
@@ -457,6 +457,7 @@ static int drop_dirty_roots(struct btrfs
 		ret = btrfs_end_transaction(trans, tree_root);
 		BUG_ON(ret);

+		btrfs_block_release(dirty->root, dirty->root->node);
 		kfree(dirty->root);
 		kfree(dirty);
 		mutex_unlock(&tree_root->fs_info->fs_mutex);