Re: [PATCH] RDMA/srp: Reserve send queue and CQ space for ib_drain_qp()

[sashiko-bot@kernel.org]

> srp_destroy_qp() calls ib_drain_qp(), which also drains the send queue.
> ib_drain_sq() requires the caller to "ensure there is room in the CQ and
> SQ for the drain work request and completion".
> 
> SRP reserves that room on the receive side, where the queue and CQ have
> queue_size + 1 entries. Commit 9294000d6d89 ("IB/srp: Drain the send
> queue before destroying a QP") switched from ib_drain_rq() to
> ib_drain_qp() but did not grow the send side. The send queue and send
> CQ hold exactly m * queue_size entries, which is the most work requests
> SRP can have outstanding. If the channel is torn down while the send
> queue is full, for example during error handling after a target stops
> responding, posting the drain work request can fail with "failed to
> drain send queue", or its completion can find the CQ full. The QP is
> then destroyed without the guarantee that ib_drain_qp() is meant to
> provide.
> 
> Add one entry to the send queue and the send CQ, as nvme-rdma and iser
> already do.
> 
> The missing reservation was found with an LLM-based tool that checks
> callers against the rules stated in kernel comments.
> 
> Fixes: 9294000d6d89 ("IB/srp: Drain the send queue before destroying a QP")
> Signed-off-by: Praneeth Balasubramanian <praneeth@ucsb.edu>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261110222421.205573-1-praneeth@ucsb.edu?part=1