Re: [PATCH v2] nvmet: handle rw's limited retry flag

Re: [PATCH v2] nvmet: handle rw's limited retry flag

[Guixin Liu]

cc linux nvme mailing list, sorry for my oversight.

Best Regards,

Guixin Liu

在 2024/11/25 15:12, Guixin Liu 写道:
> In some scenarios, some multipath software setup places the
> REQ_FAILFAST_DEV flag on I/O to prevent retries and immediately
> switch to other paths for issuing I/O commands. This will reflect
> on the NVMe read and write commands with the limited retry flag.
>
> However, the current NVMe target side does not handle the limited
> retry flag, and the target's underlying driver still retries the
> I/O. This will result in the I/O not being quickly switched to
> other paths, ultimately leading to increased I/O latency.
>
> When the nvme target receive an rw command with limited retry flag,
> handle it in block backend by setting the REQ_FAILFAST_DEV flag to
> bio.
>
> Signed-off-by: Guixin Liu <kanie@linux.alibaba.com>
> Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
> ---
> Changes from v1 to v2:
> - Add details to commit body(Christoph).
> - Add the rb tag from Chaitanya, thanks.
>
>   drivers/nvme/target/io-cmd-bdev.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/drivers/nvme/target/io-cmd-bdev.c b/drivers/nvme/target/io-cmd-bdev.c
> index 0bda83d0fc3e..6380b60fd490 100644
> --- a/drivers/nvme/target/io-cmd-bdev.c
> +++ b/drivers/nvme/target/io-cmd-bdev.c
> @@ -272,6 +272,9 @@ static void nvmet_bdev_execute_rw(struct nvmet_req *req)
>   		iter_flags = SG_MITER_FROM_SG;
>   	}
>   
> +	if (req->cmd->rw.control & NVME_RW_LR)
> +		opf |= REQ_FAILFAST_DEV;
> +
>   	if (is_pci_p2pdma_page(sg_page(req->sg)))
>   		opf |= REQ_NOMERGE;
>   

Re: [PATCH v2] nvmet: handle rw's limited retry flag

[Guixin Liu]

Hi Keith,

   Could you please apply this patch? thanks.

Best Regards,

Guixin Liu

在 2024/11/25 15:12, Guixin Liu 写道:
> In some scenarios, some multipath software setup places the
> REQ_FAILFAST_DEV flag on I/O to prevent retries and immediately
> switch to other paths for issuing I/O commands. This will reflect
> on the NVMe read and write commands with the limited retry flag.
>
> However, the current NVMe target side does not handle the limited
> retry flag, and the target's underlying driver still retries the
> I/O. This will result in the I/O not being quickly switched to
> other paths, ultimately leading to increased I/O latency.
>
> When the nvme target receive an rw command with limited retry flag,
> handle it in block backend by setting the REQ_FAILFAST_DEV flag to
> bio.
>
> Signed-off-by: Guixin Liu <kanie@linux.alibaba.com>
> Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
> ---
> Changes from v1 to v2:
> - Add details to commit body(Christoph).
> - Add the rb tag from Chaitanya, thanks.
>
>   drivers/nvme/target/io-cmd-bdev.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/drivers/nvme/target/io-cmd-bdev.c b/drivers/nvme/target/io-cmd-bdev.c
> index 0bda83d0fc3e..6380b60fd490 100644
> --- a/drivers/nvme/target/io-cmd-bdev.c
> +++ b/drivers/nvme/target/io-cmd-bdev.c
> @@ -272,6 +272,9 @@ static void nvmet_bdev_execute_rw(struct nvmet_req *req)
>   		iter_flags = SG_MITER_FROM_SG;
>   	}
>   
> +	if (req->cmd->rw.control & NVME_RW_LR)
> +		opf |= REQ_FAILFAST_DEV;
> +
>   	if (is_pci_p2pdma_page(sg_page(req->sg)))
>   		opf |= REQ_NOMERGE;
>