Hi Eric,
The easiest way to reproduce this is :
1. Create a random file of say 10 MB
xfs_io -c 'pwrite -b 4k 0 10M' -f 10MBfile
2. Reflink it
reflink -f 10MBfile reflnktest
3. Punch a hole at starting at cluster boundary with range greater that
1MB. You can also use a range that will put the end offset in another
extent.
fallocate -p -o 0 -l 1048615 reflnktest
4. sync
5. Check the first cluster in the source file. (It will be zeroed out).
dd if=10MBfile iflag=direct bs=<cluster size> count=1 | hexdump -C
Thanks,
Ashish
On 08/28/2016 10:39 PM, Eric Ren wrote:
> Hi,
>
> Thanks for this fix. I'd like to reproduce this issue locally and test
> this patch,
> could you elaborate the detailed steps of reproduction?
>
> Thanks,
> Eric
>
> On 08/27/2016 07:04 AM, Ashish Samant wrote:
>> If we punch a hole on a reflink such that following conditions are met:
>>
>> 1. start offset is on a cluster boundary
>> 2. end offset is not on a cluster boundary
>> 3. (end offset is somewhere in another extent) or
>> (hole range > MAX_CONTIG_BYTES(1MB)),
>>
>> 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. This will modify the
>> cluster
>> in place and zero it in the source too.
>>
>> Fix this by skipping this cluster in such a scenario.
>>
>> Reported-by: Saar Maoz <saar.m...@oracle.com>
>> Signed-off-by: Ashish Samant <ashish.sam...@oracle.com>
>> Reviewed-by: Srinivas Eeda <srinivas.e...@oracle.com>
>> ---
>> v1->v2:
>> -Changed the commit msg to include a better and generic description of
>> the problem, for all cluster sizes.
>> -Added Reported-by and Reviewed-by tags.
>> 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 4e7b0dc..0b055bf 100644
>> --- a/fs/ocfs2/file.c
>> +++ b/fs/ocfs2/file.c
>> @@ -1506,7 +1506,8 @@ 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;
>> @@ -1538,18 +1539,31 @@ 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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