[LU-12339] LNet Health: selecting loopback interface for sending

• Type: Technical task
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: Lustre 2.13.0, Lustre 2.12.3
• Assignee: Amir Shehata
• Reporter: Amir Shehata

Description

In the following scenario

Lustre->LNetPrimaryNID with 0@lo
Discover is initiated on 0@lo
The peer is created with 0@lo and <addr>@<net>
The interface health of the peer's <addr>@<net> is decremented
LNetPut() to self
selection algorithm selects 0@lo to send to

This exposes an issue where we try and go through the peer credit management algorithm, but because there are no credits associated with 0@lo we end up indefinitely queuing the message. ptlrpc will then get stuck waiting for send completion on the message.

This was exposed via conf-sanity 32