From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Ren <zren@suse.com>
Date: Tue, 30 Aug 2016 15:38:08 +0800
Subject: [Ocfs2-devel] [PATCH v2] ocfs2: Fix start offset to
 ocfs2_zero_range_for_truncate()
In-Reply-To: <57C50776.4050808@oracle.com>
References: <1472252646-29618-1-git-send-email-ashish.samant@oracle.com>
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Hi,

I'm on 4.8.0-rc3 kernel. Hope someone else can double-confirm this;-)

On 08/30/2016 12:11 PM, Ashish Samant wrote:
> Hmm, thats weird. I see this on 4.7 kernel without the patch:
>
> # xfs_io -c 'pwrite -b 4k 0 10M' -f 10MBfile
> wrote 10485760/10485760 bytes at offset 0
> 10 MiB, 2560 ops; 0.0000 sec (683.995 MiB/sec and 175102.5992 ops/sec)
> # reflink -f 10MBfile reflnktest
> # fallocate -p -o 0 -l 1048615 reflnktest
> # dd if=10MBfile iflag=direct bs=1048576 count=1 | hexdump -C
> 00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00 |................|
> *
> 1+0 records in
> 1+0 records out
> 1048576 bytes (1.0 MB) copied, 0.0321517 s, 32.6 MB/s
> 00100000
>
> and with patch
> ----
> # dd if=10MBfile iflag=direct bs=1M count=1 | hexdump -C
> 00000000  cd cd cd cd cd cd cd cd  cd cd cd cd cd cd cd cd |................|

I'm not familiar with this code.  So why is the output "cd ..."? because we didn't write 
anything
into "10MBfile". Is it a magic number when reading from a hole?

Eric

> *
> 1+0 records in
> 1+0 records out
> 00100000



>
> Thanks,
> Ashish
>
>
> On 08/29/2016 08:33 PM, Eric Ren wrote:
>> Hello,
>>
>> On 08/30/2016 03:23 AM, Ashish Samant wrote:
>>> 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! I have a try myself, but I'm not sure what is our expected output and if the test 
>> result meet
>> it:
>>
>> 1. After applying this patch:
>> ocfs2dev1:/mnt/ocfs2 # rm 10MBfile reflnktest
>> ocfs2dev1:/mnt/ocfs2 # xfs_io -c 'pwrite -b 4k 0 10M' -f 10MBfile
>> wrote 10485760/10485760 bytes at offset 0
>> 10 MiB, 2560 ops; 0.0000 sec (1.089 GiB/sec and 285427.5839 ops/sec)
>> ocfs2dev1:/mnt/ocfs2 # reflink -f 10MBfile reflnktest
>> ocfs2dev1:/mnt/ocfs2 # fallocate -p -o 0 -l 1048615 reflnktest
>> ocfs2dev1:/mnt/ocfs2 # dd if=10MBfile iflag=direct bs=1048576 count=1 | hexdump -C
>> 00000000  cd cd cd cd cd cd cd cd  cd cd cd cd cd cd cd cd |................|
>> *
>> 1+0 records in
>> 1+0 records out
>> 1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.0952464 s, 11.0 MB/s
>> 00100000
>>
>> 2. Before this patch:
>> ....
>> ocfs2dev1:/mnt/ocfs2 # dd if=10MBfile iflag=direct bs=1048576 count=1 | hexdump -C
>> 00000000  cd cd cd cd cd cd cd cd  cd cd cd cd cd cd cd cd |................|
>> *
>> 1+0 records in
>> 1+0 records out
>> 1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.0954648 s, 11.0 MB/s
>> 00100000
>>
>> 3. debugfs.ocfs2 -R stats /dev/sdb
>> ...
>> Block Size Bits: 12   Cluster Size Bits: 20
>> ...
>>
>> Eric
>>>
>>> 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.maoz@oracle.com>
>>>>> Signed-off-by: Ashish Samant <ashish.samant@oracle.com>
>>>>> Reviewed-by: Srinivas Eeda <srinivas.eeda@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) {
>>>>>           /*
>>>>
>>>>
>>>
>>
>
>