[stgt] [PATCH] ISCSI: Honour MaxRecvDataSegmentLength for NORMAL sessions

[FUJITA Tomonori]

On Sat, 18 Aug 2012 18:56:09 +1000
ronnie sahlberg <ronniesahlberg at gmail.com> wrote:

> The bug is that IF the initiator does state it can handle larger
> DATA-IN PDUs than 8kb,   like open-iscsi does, and all other iniators
> also does.

btw, I've seen initiators that don't send
MaxRecvDataSegmentLength long ago. I can't recall what.


> The b\ug in tgtd in processing the login is that tgtd ONLY parses this
> "lets use bigger than 8kb pdu" IFF the session is a discovery session,
> but not for NORMAL sessions.

Can you recall why we handle discovery and normal sessions differently?


> For all normal sessions tgtd will be clamped down to maximum 8kb  per
> data-in pdu due to this bug.
> 
> 
> Please compare open-iscsi to  lio vs open-iscsi vs stgt.
> With stgt any large read will be split in a train of 8kb data-in pdus.
> 
> 
> A network trace comparing open-iscsi reading from lio vs stgt will
> make the problem easy to spot. This hurts if the initiator/application
> tried to read >8k at a time.
> 
> 
> 
> regards
> ronnie sahlberg
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