[Ocfs2-devel] The last part of the file is zeroed out when write N random bytes

[Gang He]

On 2021/9/27 15:49, Joseph Qi wrote:
> 
> Last week, Andrey Markov reported a similar issue, but unfortunately not
> on mail list.
> 
> And Junxiao has resolved a similar issue recently. So can you reproduce
> the bug in latest kernel?
Yes, I can reproduce this issue with the latest code.
The cluster size must be greater than 4K(e.g. 8K, 1M), this is the key 
to the problem.

Thanks
Gang

> 
> Thanks,
> Joseph
> 
> On 9/27/21 3:16 PM, Gang He wrote:
>> Hi List,
>>
>> I'd like to report a data loss bug when write N random bytes, since I saw there were some related commits in the past weeks.
>> I can reproduce this bug stably with the latest ocfs2 kernel module code as below,
>> 1) Create a three node(e.g. ghe-tw-nd1, ghe-tw-nd2, ghe-tw-nd3) ocfs2 cluster, attach a shared disk(e.g. /dev/vdb).
>> 2) Format the disk with the command "mkfs.ocfs2 -N 4 -b 4096 -C 1048576 /dev/vdb", and mount the disk to /mnt/shared on each node. The cluster size must be greater than 4K, this is the key to the problem.
>> 3) Copy the file write/test scripts to /mnt/shared directory, then run test script on node1 to reproduce this bug.
>>      file write script ocfs2_fallocate_bug_plain_write.py: https://pastebin.com/QsXcD8rq
>>      file test script ocfs2_loop.sh: https://pastebin.com/eTUe2hkW
>> 4) Then, you can meet this bug, the file md5sum is different between from node1 and from node2.
>>      In fact, the last part of the file is zeroed out from node2.
>>      e.g.
>>      file dump from node1: https://pastebin.com/HB92TVS0
>>      file dump from node2: https://pastebin.com/jBG7HdSz
>>
>> More information,
>> this bug does not exist on some old kernels( e.g. linux-4.12.14-120), but it will happen on some new kernels, I feel this bug is probably NOT caused by ocfs2 commits, since I used old ocfs2 kernel module code on the new kernels, the problem also happened.
>> Anyway, if you have any comments, please reply this mail.
>>   
>> Thanks
>> Gang
>>
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>