Good catch! Thank you for the fix

Reviewed-by: Srinivas Eeda <srinivas.e...@oracle.com>

On 08/11/2016 04:12 PM, Ashish Samant wrote:
> If we do fallocate with punch hole option on a reflink, with start offset
> on a cluster boundary and end offset somewhere in another cluster, we
> dont COW the first cluster starting at the start offset. But in this
> case, we were wrongly passing this cluster to
> ocfs2_zero_range_for_truncate() to zero out.
>
> Fix this by skipping this cluster in such a scenario.
>
> Signed-off-by: Ashish Samant <ashish.sam...@oracle.com>
> ---
>   fs/ocfs2/file.c | 34 ++++++++++++++++++++++++----------
>   1 file changed, 24 insertions(+), 10 deletions(-)
>
> diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
> index 4a6e130..ab305aa 100644
> --- a/fs/ocfs2/file.c
> +++ b/fs/ocfs2/file.c
> @@ -1522,7 +1522,8 @@ static int ocfs2_zero_partial_clusters(struct inode 
> *inode,
>                                      u64 start, u64 len)
>   {
>       int ret = 0;
> -     u64 tmpend, end = start + len;
> +     u64 tmpend = 0;
> +     u64 end = start + len;
>       struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
>       unsigned int csize = osb->s_clustersize;
>       handle_t *handle;
> @@ -1554,18 +1555,31 @@ static int ocfs2_zero_partial_clusters(struct inode 
> *inode,
>       }
>   
>       /*
> -      * We want to get the byte offset of the end of the 1st cluster.
> +      * If start is on a cluster boundary and end is somewhere in another
> +      * cluster, we have not COWed the cluster starting at start, unless
> +      * end is also within the same cluster. So, in this case, we skip this
> +      * first call to ocfs2_zero_range_for_truncate() truncate and move on
> +      * to the next one.
>        */
> -     tmpend = (u64)osb->s_clustersize + (start & ~(osb->s_clustersize - 1));
> -     if (tmpend > end)
> -             tmpend = end;
> +     if ((start & (csize - 1)) != 0) {
> +             /*
> +              * We want to get the byte offset of the end of the 1st
> +              * cluster.
> +              */
> +             tmpend = (u64)osb->s_clustersize +
> +                     (start & ~(osb->s_clustersize - 1));
> +             if (tmpend > end)
> +                     tmpend = end;
>   
> -     trace_ocfs2_zero_partial_clusters_range1((unsigned long long)start,
> -                                              (unsigned long long)tmpend);
> +             trace_ocfs2_zero_partial_clusters_range1(
> +                     (unsigned long long)start,
> +                     (unsigned long long)tmpend);
>   
> -     ret = ocfs2_zero_range_for_truncate(inode, handle, start, tmpend);
> -     if (ret)
> -             mlog_errno(ret);
> +             ret = ocfs2_zero_range_for_truncate(inode, handle, start,
> +                                                 tmpend);
> +             if (ret)
> +                     mlog_errno(ret);
> +     }
>   
>       if (tmpend < end) {
>               /*


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