[LU-12532] LNet Health: Resending optimized GET broken

Mon, 22 Jul 2019 18:31:21 +0000

The concept of an optimized GET allows data to be RDMAed directly into the buffer with no need for an explicit REPLY message. In order to achieve this the LND allocates a reply message when initially processing the GET send request. Then it calls LNet finalize on both the original GET and the "fake" REPLY message when the RDMA operation is complete.

This, however, presents a problem for resends. When an MD is allocated if it expects a response the threshold of the MD is set to 2. The threshold is decremented when the MD is attached to the GET message, and then decremented again when the MD is attached to the REPLY message.

When resending, the MD threshold is already 0, so when the LND allocates the REPLY message, it fails because the threshold is already 0.

We need to redesign the optimized GET processing to work with resends.

Whamcloud Community JIRA

[LU-12532] LNet Health: Resending optimized GET broken