linux-kernel - Re: [PATCH] nvmet: pci-epf: Do not complete commands twice if nvmet_req

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Message-ID: <CAAEEuhrtDcKfFF9NuME89tziuqYz4Y5fwepKE0kjSQD_6fzb2g@mail.gmail.com>
Date: Tue, 15 Jul 2025 11:25:04 +0200
From: Rick Wertenbroek <rick.wertenbroek@...il.com>
Cc: rick.wertenbroek@...g-vd.ch, dlemoal@...nel.org, 
	alberto.dassatti@...g-vd.ch, Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>, 
	Chaitanya Kulkarni <kch@...dia.com>, linux-nvme@...ts.infradead.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nvmet: pci-epf: Do not complete commands twice if
 nvmet_req_init() fails

On Tue, Jul 15, 2025 at 11:18 AM Rick Wertenbroek
<rick.wertenbroek@...il.com> wrote:
>
> Have nvmet_req_init() and req->execute() complete failed commands.
>
> Description of the problem:
> nvmet_req_init() calls __nvmet_req_complete() internally upon failure,
> e.g., unsupported opcode, which calls the "queue_response" callback,
> this results in nvmet_pci_epf_queue_response() being called, which will
> call nvmet_pci_epf_complete_iod() if data_len is 0 or if dma_dir is
> different than DMA_TO_DEVICE. This results in a double completion as
> nvmet_pci_epf_exec_iod_work() also calls nvmet_pci_epf_complete_iod()
> when nvmet_req_init() fails.
>
> Steps to reproduce:
> On the host send a command with an unsupported opcode with nvme-cli,
> For example the admin command "security receive"
> $ sudo nvme security-recv /dev/nvme0n1 -n1 -x4096
>
> This triggers a double completion as nvmet_req_init() fails and
> nvmet_pci_epf_queue_response() is called, here iod->dma_dir is still
> in the default state of "DMA_NONE" as set by default in
> nvmet_pci_epf_alloc_iod(), so nvmet_pci_epf_complete_iod() is called.
> Because nvmet_req_init() failed nvmet_pci_epf_complete_iod() is also
> called in nvmet_pci_epf_exec_iod_work() leading to a doubple completion.
>

s/doubple/double/

> This patch lets nvmet_req_init() and req->execute() complete all failed
> commands, and removes the double completion case in
> nvmet_pci_epf_exec_iod_work() therefore fixing the edge cases where
> double completions occurred.
>
> Signed-off-by: Rick Wertenbroek <rick.wertenbroek@...il.com>
> ---
>  drivers/nvme/target/pci-epf.c | 18 ++++++++++++------
>  1 file changed, 12 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/nvme/target/pci-epf.c b/drivers/nvme/target/pci-epf.c
> index a4295a5b8d28..aad828eb72d6 100644
> --- a/drivers/nvme/target/pci-epf.c
> +++ b/drivers/nvme/target/pci-epf.c
> @@ -1243,7 +1243,7 @@ static void nvmet_pci_epf_queue_response(struct nvmet_req *req)
>         iod->status = le16_to_cpu(req->cqe->status) >> 1;
>
>         /* If we have no data to transfer, directly complete the command. */
> -       if (!iod->data_len || iod->dma_dir != DMA_TO_DEVICE) {
> +       if (iod->status || !iod->data_len || iod->dma_dir != DMA_TO_DEVICE) {
>                 nvmet_pci_epf_complete_iod(iod);
>                 return;
>         }
> @@ -1604,8 +1604,13 @@ static void nvmet_pci_epf_exec_iod_work(struct work_struct *work)
>                 goto complete;
>         }
>
> +       /*
> +        * If nvmet_req_init() fails (e.g., unsupported opcode) it will call
> +        * __nvmet_req_complete() internally which will call
> +        * nvmet_pci_epf_queue_response() and will complete the command directly.
> +        */
>         if (!nvmet_req_init(req, &iod->sq->nvme_sq, &nvmet_pci_epf_fabrics_ops))
> -               goto complete;
> +               return;
>
>         iod->data_len = nvmet_req_transfer_len(req);
>         if (iod->data_len) {
> @@ -1643,10 +1648,11 @@ static void nvmet_pci_epf_exec_iod_work(struct work_struct *work)
>
>         wait_for_completion(&iod->done);
>
> -       if (iod->status == NVME_SC_SUCCESS) {
> -               WARN_ON_ONCE(!iod->data_len || iod->dma_dir != DMA_TO_DEVICE);
> -               nvmet_pci_epf_transfer_iod_data(iod);
> -       }
> +       if (iod->status != NVME_SC_SUCCESS)
> +               return;
> +
> +       WARN_ON_ONCE(!iod->data_len || iod->dma_dir != DMA_TO_DEVICE);
> +       nvmet_pci_epf_transfer_iod_data(iod);
>
>  complete:
>         nvmet_pci_epf_complete_iod(iod);
> --
> 2.25.1
>