Re: [PATCH V10 4/8] nvmet: add ZBD over ZNS backend support

[Christoph Hellwig <hch@lst.de>]

On Mon, Mar 08, 2021 at 08:58:19PM -0800, Chaitanya Kulkarni wrote:
> NVMe TP 4053 – Zoned Namespaces (ZNS) allows host software to
> communicate with a non-volatile memory subsystem using zones for
> NVMe protocol based controllers. NVMeOF already support the ZNS NVMe
> Protocol compliant devices on the target in the passthru mode. There
> are Generic zoned block devices like  Shingled Magnetic Recording (SMR)
> HDDs that are not based on the NVMe protocol.
> 
> This patch adds ZNS backend to support the ZBDs for NVMeOF target.
> 
> This support includes implementing the new command set NVME_CSI_ZNS,
> adding different command handlers for ZNS command set such as
> NVMe Identify Controller, NVMe Identify Namespace, NVMe Zone Append,
> NVMe Zone Management Send and NVMe Zone Management Receive.
> 
> With new command set identifier we also update the target command effects
> logs to reflect the ZNS compliant commands.
> 
> Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
> ---
>  drivers/nvme/target/Makefile      |   1 +
>  drivers/nvme/target/admin-cmd.c   |   8 +
>  drivers/nvme/target/io-cmd-bdev.c |  33 +++-
>  drivers/nvme/target/nvmet.h       |  38 ++++
>  drivers/nvme/target/zns.c         | 308 ++++++++++++++++++++++++++++++
>  5 files changed, 380 insertions(+), 8 deletions(-)
>  create mode 100644 drivers/nvme/target/zns.c
> 
> diff --git a/drivers/nvme/target/Makefile b/drivers/nvme/target/Makefile
> index ebf91fc4c72e..9837e580fa7e 100644
> --- a/drivers/nvme/target/Makefile
> +++ b/drivers/nvme/target/Makefile
> @@ -12,6 +12,7 @@ obj-$(CONFIG_NVME_TARGET_TCP)		+= nvmet-tcp.o
>  nvmet-y		+= core.o configfs.o admin-cmd.o fabrics-cmd.o \
>  			discovery.o io-cmd-file.o io-cmd-bdev.o
>  nvmet-$(CONFIG_NVME_TARGET_PASSTHRU)	+= passthru.o
> +nvmet-$(CONFIG_BLK_DEV_ZONED)		+= zns.o
>  nvme-loop-y	+= loop.o
>  nvmet-rdma-y	+= rdma.o
>  nvmet-fc-y	+= fc.o
> diff --git a/drivers/nvme/target/admin-cmd.c b/drivers/nvme/target/admin-cmd.c
> index 76d9fc0f48c2..05ef362d70b7 100644
> --- a/drivers/nvme/target/admin-cmd.c
> +++ b/drivers/nvme/target/admin-cmd.c
> @@ -719,8 +719,16 @@ static void nvmet_execute_identify(struct nvmet_req *req)
>  	switch (req->cmd->identify.cns) {
>  	case NVME_ID_CNS_NS:
>  		return nvmet_execute_identify_ns(req);
> +	case NVME_ID_CNS_CS_NS:
> +		if (req->cmd->identify.csi == NVME_CSI_ZNS)
> +			return nvmet_execute_identify_cns_cs_ns(req);
> +		break;
>  	case NVME_ID_CNS_CTRL:
>  		return nvmet_execute_identify_ctrl(req);
> +	case NVME_ID_CNS_CS_CTRL:
> +		if (req->cmd->identify.csi == NVME_CSI_ZNS)
> +			return nvmet_execute_identify_cns_cs_ctrl(req);
> +		break;

I still find the way how this mixes the CNS and CSI fields in a single
switch weird.  I'd expect an outer switch for CNS and an inner one for
the CSI value.

> +static u16 nvmet_bdev_zns_checks(struct nvmet_req *req)
> +{
> +	if (!bdev_is_zoned(req->ns->bdev))
> +		return NVME_SC_INVALID_NS | NVME_SC_DNR;
> +
> +	if (req->cmd->zmr.zra != NVME_ZRA_ZONE_REPORT)
> +		return NVME_SC_INVALID_FIELD;
> +
> +	if (req->cmd->zmr.zrasf != NVME_ZRASF_ZONE_REPORT_ALL)
> +		return NVME_SC_INVALID_FIELD;
> +
> +	if (req->cmd->zmr.pr != NVME_REPORT_ZONE_PARTIAL)
> +		return NVME_SC_INVALID_FIELD;

error_loc information would be useful here.

> +static inline bool nvmet_zns_update_zasl(struct nvmet_ns *ns)
> +{
> +	struct request_queue *q = ns->bdev->bd_disk->queue;
> +	u8 zasl = nvmet_zasl(queue_max_zone_append_sectors(q));
> +
> +	if (ns->subsys->zasl)
> +		return ns->subsys->zasl < zasl ? false : true;

No need for the tenary expression here, the comparism will autoconvert to
bool.

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