From 276e680d192a67d222fcea51af37b056feffb665 Mon Sep 17 00:00:00 2001 From: Yan Zheng Date: Thu, 30 Jul 2009 09:40:40 -0400 Subject: Btrfs: preserve commit_root for async caching The async block group caching code uses the commit_root pointer to get a stable version of the extent allocation tree for scanning. This copy of the tree root isn't going to change and it significantly reduces the complexity of the scanning code. During a commit, we have a loop where we update the extent allocation tree root. We need to loop because updating the root pointer in the tree of tree roots may allocate blocks which may change the extent allocation tree. Right now the commit_root pointer is changed inside this loop. It is more correct to change the commit_root pointer only after all the looping is done. Signed-off-by: Yan Zheng Signed-off-by: Chris Mason --- fs/btrfs/transaction.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) (limited to 'fs/btrfs/transaction.c') diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c index e51d2bc532f8..de48e4ec808c 100644 --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -42,10 +42,8 @@ static noinline void put_transaction(struct btrfs_transaction *transaction) static noinline void switch_commit_root(struct btrfs_root *root) { - down_write(&root->commit_root_sem); free_extent_buffer(root->commit_root); root->commit_root = btrfs_root_node(root); - up_write(&root->commit_root_sem); } /* @@ -466,7 +464,10 @@ static int update_cowonly_root(struct btrfs_trans_handle *trans, ret = btrfs_write_dirty_block_groups(trans, root); BUG_ON(ret); } - switch_commit_root(root); + + if (root != root->fs_info->extent_root) + switch_commit_root(root); + return 0; } @@ -499,6 +500,11 @@ static noinline int commit_cowonly_roots(struct btrfs_trans_handle *trans, update_cowonly_root(trans, root); } + + down_write(&fs_info->extent_commit_sem); + switch_commit_root(fs_info->extent_root); + up_write(&fs_info->extent_commit_sem); + return 0; } -- cgit v1.2.2