Merging se_dev_entry and se_lun?
Hi Nic,
having done the patch to export 'write_protect' for demo-mode LUNs I've came across one puzzling item:
struct se_lun uses a list to refer to the underlying se_dev_entry structures. Which I found rather curious, as from my understanding 'se_lun' is the structure for the mapped LUN (ie the LUN visible to the initiator) and 'se_dev_entry' is the underlying physical device as visible to the LUN.
As such I would have expected a 1:1 relationship between both, ie a simple pointer from se_lun to se_dev_entry.
Having a list here implies that 'se_lun' can have _several_ se_dev_entry structure attached to it, which I found rather curious.
Can you give me an example where this might be the case? Or can we replace the list with a simple pointer or even merge both?
Reason I'm asking is the lun_access / dev_flags field; it really looks like it being a duplicate (I would judge 'write_protect' to be a property of the mapped LUN, and not of the underlying device), but in either case having it in both places requires a synchronisation between both, as for demo-mode LUNs we can only change it via se_lun, and for others we have to change it via the se_dev_entry.
Cheers,
Hannes
Signature · 5 lines
Dr. Hannes Reinecke zSeries & Storage [email protected] +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton HRB 21284 (AG Nürnberg)
Quoted 5 lines · Hannes Reinecke
Having a list here implies that '
se_lun' can have _several_se_dev_entrystructure attached to it, which I found rather curious.Can you give me an example where this might be the case? Or can we replace the list with a simple pointer or even merge both?
Each initiator has it's own dev entry.
What might make sense with the new list-based dev entry handling is to merge the se_lun_acl and se_dev_entry, but it would be a fair amount of work.
Quoted 9 lines · Christoph Hellwig
Quoted 5 lines · Hannes Reinecke
Having a list here implies that '
se_lun' can have _several_se_dev_entrystructure attached to it, which I found rather curious.Can you give me an example where this might be the case? Or can we replace the list with a simple pointer or even merge both?
Each initiator has it's own dev entry.
But isn't 'se_lun' per initiator, too?
Cheers,
Hannes
Signature · 5 lines
Dr. Hannes Reinecke zSeries & Storage [email protected] +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton HRB 21284 (AG Nürnberg)
Quoted 3 lines · Hannes Reinecke
Quoted 2 lines
Each initiator has it's own dev entry.
But isn't '
se_lun' per initiator, too?
No.
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