Re: [PATCH RFC 3/3] RDMA/rtrs: Post client read requests inline

[sashiko-bot@kernel.org]

> The RTRS client sends a read request as an RDMA Write with Immediate of
> a small message: the user message, the RTRS header and one memory
> descriptor, about 60 bytes for RNBD. The message is posted by reference
> and the QP asks for no inline data, so the HCA has to DMA-read it from
> host memory before sending. That read is on the latency path of every
> read.
> 
> Let rtrs_cq_qp_create() take the amount of inline data to ask for.
> The client asks for RTRS_CLT_MAX_INLINE_DATA, enough for a read
> request with one descriptor and up to 64 bytes of user message, and
> the server asks for none. If the device refuses, the QP is created
> without inline data. The client posts a read request with
> IB_SEND_INLINE when it fits in the inline size the device granted.
> Write requests, whose message travels behind the data in the same
> WR, are not changed.
> 
> Providers copy inline data from sg_list[].addr as a kernel virtual
> address, so the inline path puts req->iu->buf in the on-stack SGE.
> 
> Assisted-by: LLM
> Signed-off-by: Andrei-Alexandru Bleortu <me@andrei-z.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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