Re: [PATCH v1 3/5] svcrdma: fix a page leak in backchannel sends

[sashiko-bot@kernel.org]

> svc_rdma_bc_sendto() takes an extra reference on the page that
> holds the backchannel Call message, so that the page is not
> returned to the allocator while the Send that reads it is still
> posted. Send completion once dropped that reference, back when the
> page sat in the send context's page array. Commit 99722fe4d5a6
> ("svcrdma: Persistently allocate and DMA-map Send buffers")
> switched the backchannel to svc_rdma_map_reply_msg(), which
> DMA-maps the buffer and records no pages. Send completion no
> longer touches the page, but the get_page() stayed.
> 
> xprt_rdma_bc_free() drops the allocation reference and nothing
> drops the extra one, so every backchannel Call sent over RPC/RDMA
> leaks its send buffer page.
> 
> The extra reference is still needed. A Call at or above
> RPCRDMA_PULLUP_THRESH is DMA-mapped in place. The RPC client frees
> rq_buffer when the callback task times out or is killed, whether
> or not the Send has completed. Record the page in the send
> context's page array so that svc_rdma_send_ctxt_release() drops
> the reference after Send completion.
> 
> Fixes: 99722fe4d5a6 ("svcrdma: Persistently allocate and DMA-map Send buffers")
> Signed-off-by: Chuck Lever <cel@kernel.org>

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

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Sashiko AI review · https://sashiko.dev/#/patchset/20260922015128.240977-1-cel@kernel.org?part=3