[LU-14660] Fix destination NID for discovery PUSH

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.15.0
• Severity: 3
• Assignee: Chris Horn
• Reporter: Chris Horn

Description

If we're sending a discovery PUSH after receiving a discovery
REPLY then we want to send via the same NID that the reply was
sent to. This introduces a challenge in selecting an appropriate
destination NID for the PUSH because lnet_select_pathway() will not
run the MR selection algorithm for choosing a peer NI if the source
NI has been specified.

It is reasonable to assume that the NID used by the message
originator in sending the REPLY is a suitable destination for the
discovery PUSH. Thus, we record this NID in the same location we
currently record the lp_disc_src_nid, and use it when sending the
PUSH. With this change, the only other user of lnet_peer_select_nid()
is lnet_peer_send_ping(). In the ping case we do not set a source NID,
so lnet_select_pathway() is free to choose any peer NI. So this change
allows us to get rid of lnet_peer_select_nid() altogether.

Alternatively, we would need to reproduce a lot of the path selection
algorithm inside lnet_peer_select_nid() in order to avoid sending to
unhealthy NIDs. It seems undesirable and unnecessary to duplicate that
logic.

Comments

[Peter Jones]

Landed for 2.15

[Gerrit Updater]

Oleg Drokin ([e-mail]) merged in patch https://review.whamcloud.com/43507/
Subject: LU-14660 lnet: Fix destination NID for discovery PUSH
Project: fs/lustre-release
Branch: master
Current Patch Set:
Commit: dce2f7d1987711dfdced903b13e67091cffe9628

[Gerrit Updater]

Chris Horn ([e-mail]) uploaded a new patch: https://review.whamcloud.com/43507
Subject: LU-14660 lnet: Fix destination NID for discovery PUSH
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: 61cd56a6d0abf99b995fd5877fb0146771f14f6f