[Lustre-devel] rename in Changelog

[Alexey Lyashkov]

but it's introduce the race. different mdt thread my write a one or more llog record between rename records.
so it's isn't always two next records.

On Apr 25, 2012, at 23:36, Nathan Rutman wrote:

> it wasn't done that way in the first place because the record size in an llog is fixed,
> so any size increase is multiplied by the number of records, so fewer records
> can be stored.  Splitting the rename into two was the unfortunate casualty of that goal.
> 
> On Apr 25, 2012, at 2:05 AM, Lai Siyao wrote:
> 
>> Rename record in Changelog is different from other operations, it's split into
>> two records: RNMFRM and RNMTO. This makes Changelog analysis hard
>> because these two records may not be consecutive and several renames
>> may occur at the same time.
>> 
>> I'm not clear why it's designed to be so, except that RNMTO is needed
>> because for DNE (distributed namespace) the rename target may reside on
>> another MDS, and a separate RNMTO record is needed. But even with this
>> it's fine to store all information in a RENME record, but leave the information of
>> whether rename removes the last hardlink of the target file (if it exists) in
>> RNMTO record.
>> 
>> I tried to add a field spfid in struct changelog_rec to store source parent fid,
>> and pack both source (if has) and target names into record. Normally the
>> record size if sizeof(fid) larger than before, and it can be differentiated
>> according to version. The test result looks good, but I want to know whether
>> anyone oppose to this? If not, I'll make the change and make it changelog
>> version 2.
>> 
>> Cheers,
>> - Lai
>> 
>> 
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