On Fri, Nov 15, 2019 at 8:44 PM Josef Bacik <josef@xxxxxxxxxxxxxx> wrote:
>
> Testing with the new fsstress support for subvolumes uncovered a pretty
> bad problem with rename exchange on subvolumes. We're modifying two
> different subvolumes, but we only start the transaction on one of them,
> so the other one is not added to the dirty root list. This is caught by
> btrfs_cow_block() with a warning because the root has not been updated,
> however if we do not modify this root again we'll end up pointing at an
> invalid root because the root item is never updated.
>
> Fix this by making sure we add the destination root to the trans list,
> the same as we do with normal renames. This fixes the corruption.
>
> Fixes: cdd1fedf8261 ("btrfs: add support for RENAME_EXCHANGE and RENAME_WHITEOUT")
> Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
Reviewed-by: Filipe Manana <fdmanana@xxxxxxxx>
Looks good, thanks.
> ---
> fs/btrfs/inode.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index f6fc47525a52..56032c518b26 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -9575,6 +9575,9 @@ static int btrfs_rename_exchange(struct inode *old_dir,
> goto out_notrans;
> }
>
> + if (dest != root)
> + btrfs_record_root_in_trans(trans, dest);
> +
> /*
> * We need to find a free sequence number both in the source and
> * in the destination directory for the exchange.
> --
> 2.23.0
>
--
Filipe David Manana,
“Whether you think you can, or you think you can't — you're right.”
