On Mon, Mar 02, 2015 at 12:46:55PM -0500, Josef Bacik wrote:
> Dave could hit this assert consistently running btrfs/078. This is because
> when we update the block groups we could truncate the free space, which would
> try to delete the csums for that range and dirty the csum root. For this to
> happen we have to have already written out the csum root so it's kind of hard to
> hit this case. This patch fixes this by changing the logic to only write the
> dirty block groups if the dirty_cowonly_roots list is empty. This will get us
> the same effect as before since we add the extent root last, and will cover the
> case that we dirty some other root again but not the extent root. Thanks,
Free space inode is NODATASUM, so its searching csum tree in
__btrfs_free_extent() is really unnecessary, by skipping that, csum tree
won't be inserted into dirty_cowonly_roots list again, so it also passed btrfs/078,
at least on my box.
Thanks,
-liubo
>
> Reported-by: David Sterba <dsterba@xxxxxxx>
> Signed-off-by: Josef Bacik <jbacik@xxxxxx>
> ---
> fs/btrfs/transaction.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
> index 038fcf6..a7a413f 100644
> --- a/fs/btrfs/transaction.c
> +++ b/fs/btrfs/transaction.c
> @@ -1023,16 +1023,22 @@ static int update_cowonly_root(struct btrfs_trans_handle *trans,
> u64 old_root_bytenr;
> u64 old_root_used;
> struct btrfs_root *tree_root = root->fs_info->tree_root;
> - bool extent_root = (root->objectid == BTRFS_EXTENT_TREE_OBJECTID);
> + struct btrfs_fs_info *fs_info = root->fs_info;
>
> 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);
> +
> + /*
> + * We can only break out if our root matches the root item and
> + * we either have more roots to process or we have no more roots
> + * to process and there are no empty bgs.
> + */
> if (old_root_bytenr == root->node->start &&
> old_root_used == btrfs_root_used(&root->root_item) &&
> - (!extent_root ||
> + (!list_empty(&fs_info->dirty_cowonly_roots) ||
> list_empty(&trans->transaction->dirty_bgs)))
> break;
>
> @@ -1044,7 +1050,7 @@ static int update_cowonly_root(struct btrfs_trans_handle *trans,
> return ret;
>
> old_root_used = btrfs_root_used(&root->root_item);
> - if (extent_root) {
> + if (list_empty(&fs_info->dirty_cowonly_roots)) {
> ret = btrfs_write_dirty_block_groups(trans, root);
> if (ret)
> return ret;
> --
> 1.8.3.1
>
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