[Lustre-devel] OSD iterator interface

[di wang <di.wang@sun.com>]

Hello,

In new MDS stack, osd suppose do not understand Directory (IMHO), and it 
only provides
index API. MDD  will  use  the index API  to fill the dir entries.

The filldir in current EA index API is just for compatible with old version
of  MDS.  Maybe we need bulk index API for readdir ?  But Alex should 
know more.

Thanks
WangDi

Oleg Drokin wrote:
> Hello!
>
>     While inspecting patches in bug 17560 it struck me as odd that we  
> are fetching the data one entry at a time from the filesystem, so I  
> asked a many-entries at a time
>     approach to be implemented. Now the patch in the bug just fills  
> the osd buffer with entries (after parsing them) and then actual user  
> (e.g. __mdd_readpage)
>     reparses the osd buffer and copies data to its own. This is a lot  
> of wasted processing, copies and then some extra memory usage.
>     So in my opinion the iterator interface should be reworked to  
> accept an iterator and a buffer and then __mdd_readdir will pass in  
> its own
>     parsing of the data (with possible generalized preparsing from osd  
> so that we are fs-neutral) and will directly fill its own buffer to  
> the amount it actually needs,
>     kind of like any kernel filldir functions already work right now.
>
>     Am I missing something stupid? Are there any objections, would  
> this break anything?
>
> Bye,
>      Oleg
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