Re: [PATCH 1/5] xfs: cancel COW blocks before swapext

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Thu, Sep 20, 2018 at 04:42:16PM +0200, Christoph Hellwig wrote:
> We need to make sure we have no outstanding COW blocks before we swap
> extents, as there is nothing preventing us from having COW preallocations
> on an inode that swapext is called on.  That case can easily be
> reproduced by the upcoming always_cow mode.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Seems reasonable to me,
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

> ---
>  fs/xfs/xfs_bmap_util.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> index 414dbc31139c..e0e9cbc98ccd 100644
> --- a/fs/xfs/xfs_bmap_util.c
> +++ b/fs/xfs/xfs_bmap_util.c
> @@ -1515,6 +1515,12 @@ xfs_swap_extent_flush(
>  		return error;
>  	truncate_pagecache_range(VFS_I(ip), 0, -1);
>  
> +	if (xfs_inode_has_cow_data(ip)) {
> +		error = xfs_reflink_cancel_cow_range(ip, 0, NULLFILEOFF, true);
> +		if (error)
> +			return error;
> +	}
> +
>  	/* Verify O_DIRECT for ftmp */
>  	if (VFS_I(ip)->i_mapping->nrpages)
>  		return -EINVAL;
> -- 
> 2.18.0
>