[PATCH] Always update root items for fs trees at commit time

[PATCH] Always update root items for fs trees at commit time

[Yan Zheng]

commit_fs_roots skips updating root items for fs trees that aren't modified.
This is unsafe since relocation code modifies root item's last_snapshot field
without modifying corresponding fs tree.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>

---
diff -urp 1/fs/btrfs/transaction.c 2/fs/btrfs/transaction.c
--- 1/fs/btrfs/transaction.c	2009-06-12 21:32:39.812512710 +0800
+++ 2/fs/btrfs/transaction.c	2009-06-15 13:33:56.000000000 +0800
@@ -543,13 +543,13 @@ static noinline int commit_fs_roots(stru
 			btrfs_free_log(trans, root);
 			btrfs_update_reloc_root(trans, root);
 
-			if (root->commit_root == root->node)
-				continue;
+			if (root->commit_root != root->node) {
+				free_extent_buffer(root->commit_root);
+				root->commit_root = btrfs_root_node(root);
+				btrfs_set_root_node(&root->root_item,
+						    root->node);
+			}
 
-			free_extent_buffer(root->commit_root);
-			root->commit_root = btrfs_root_node(root);
-
-			btrfs_set_root_node(&root->root_item, root->node);
 			err = btrfs_update_root(trans, fs_info->tree_root,
 						&root->root_key,
 						&root->root_item);

Re: [PATCH] Always update root items for fs trees at commit time

[Chris Mason]

On Mon, Jun 15, 2009 at 09:22:31PM +0800, Yan Zheng wrote:
> commit_fs_roots skips updating root items for fs trees that aren't modified.
> This is unsafe since relocation code modifies root item's last_snapshot field
> without modifying corresponding fs tree.

Thanks for working on these patches.

This could make commit pretty expensive when there are many snapshots in
place that don't get modified.  Could you please change the balance code
to mark the root to force writeout?

-chris