[Ocfs2-devel] [PATCH 2/2] Ocfs2: Fix punching hole codes to correctly do CoW during cluster zeroing.

[TaoMa <tao.ma@oracle.com>]

Hi Tristan,
Tristan Ye wrote:
> Based on the former patch of truncating optimization, bugfix for refcount on
> punching holes can be fairly easy and straightforward since most of work we
> should take into account for refcounting have been completed already in func
> ocfs2_remove_btree_range(), which is also being used by our truncating codes.
>
> The patch just did CoW for reflinks when a hole is being punched whose start
> and end offset were within one cluster, which means partial zeroing for a cluster
> will be performed soon.
>
> The patch has been tested fixing the following bug:
>
> http://oss.oracle.com/bugzilla/show_bug.cgi?id=1216
>
> Signed-off-by: Tristan Ye <tristan.ye@oracle.com>
> ---
>  fs/ocfs2/file.c |   21 +++++++++++++++++++++
>  1 files changed, 21 insertions(+), 0 deletions(-)
>
> diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
> index e0c9d1c..bb15a1e 100644
> --- a/fs/ocfs2/file.c
> +++ b/fs/ocfs2/file.c
> @@ -1458,6 +1458,27 @@ static int ocfs2_remove_inode_range(struct inode *inode,
>  		goto out;
>  	}
>  
> +	/*
> +	 * For reflinks, we may need to CoW 2 clusters which might be
> +	 * partially zero'd later, if hole's start and end offset were
> +	 * within one cluster(means is not exactly aligned to clustersize).
> +	 */
> +
> +	if (OCFS2_I(inode)->ip_dyn_features & OCFS2_HAS_REFCOUNT_FL) {
> +
> +		ret = ocfs2_cow_file_pos(inode, di_bh, byte_start);
> +		if (ret) {
> +			mlog_errno(ret);
> +			goto out;
> +		}
> +
> +		ret = ocfs2_cow_file_pos(inode, di_bh, byte_start + byte_len);
> +		if (ret) {
> +			mlog_errno(ret);
> +			goto out;
> +		}
> +	}
> +
>   
If the bytes_start and bytes_sart + byte_len are in alignment with 
cluster size, we don't need to do CoW.

Regards,
Tao