Re: [PATCHv10 8/9] nvme: enable FDP support

[Chaitanya Kulkarni <chaitanyak@nvidia.com>]

On 10/29/24 08:19, Keith Busch wrote:
> From: Kanchan Joshi <joshi.k@samsung.com>
>
> Flexible Data Placement (FDP), as ratified in TP 4146a, allows the host
> to control the placement of logical blocks so as to reduce the SSD WAF.
> Userspace can send the write hint information using io_uring or fcntl.
>
> Fetch the placement-identifiers if the device supports FDP. The incoming
> write-hint is mapped to a placement-identifier, which in turn is set in
> the DSPEC field of the write command.
>
> Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
> Signed-off-by: Hui Qi <hui81.qi@samsung.com>
> Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
> Reviewed-by: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Keith Busch <kbusch@kernel.org>
> ---
>   drivers/nvme/host/core.c | 84 ++++++++++++++++++++++++++++++++++++++++
>   drivers/nvme/host/nvme.h |  5 +++
>   include/linux/nvme.h     | 19 +++++++++
>   3 files changed, 108 insertions(+)
>
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index 3de7555a7de74..bd7b89912ddb9 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -44,6 +44,20 @@ struct nvme_ns_info {
>   	bool is_removed;
>   };
>   
> +struct nvme_fdp_ruh_status_desc {
> +	u16 pid;
> +	u16 ruhid;
> +	u32 earutr;
> +	u64 ruamw;
> +	u8  rsvd16[16];
> +};
> +
> +struct nvme_fdp_ruh_status {
> +	u8  rsvd0[14];
> +	__le16 nruhsd;
> +	struct nvme_fdp_ruh_status_desc ruhsd[];
> +};
> +
>   unsigned int admin_timeout = 60;
>   module_param(admin_timeout, uint, 0644);
>   MODULE_PARM_DESC(admin_timeout, "timeout in seconds for admin commands");
> @@ -657,6 +671,7 @@ static void nvme_free_ns_head(struct kref *ref)
>   	ida_free(&head->subsys->ns_ida, head->instance);
>   	cleanup_srcu_struct(&head->srcu);
>   	nvme_put_subsystem(head->subsys);
> +	kfree(head->plids);
>   	kfree(head);
>   }
>   
> @@ -974,6 +989,13 @@ static inline blk_status_t nvme_setup_rw(struct nvme_ns *ns,
>   	if (req->cmd_flags & REQ_RAHEAD)
>   		dsmgmt |= NVME_RW_DSM_FREQ_PREFETCH;
>   
> +	if (req->write_hint && ns->head->nr_plids) {
> +		u16 hint = max(req->write_hint, ns->head->nr_plids);
> +
> +		dsmgmt |= ns->head->plids[hint - 1] << 16;
> +		control |= NVME_RW_DTYPE_DPLCMT;
> +	}
> +
>   	if (req->cmd_flags & REQ_ATOMIC && !nvme_valid_atomic_write(req))
>   		return BLK_STS_INVAL;
>   
> @@ -2105,6 +2127,52 @@ static int nvme_update_ns_info_generic(struct nvme_ns *ns,
>   	return ret;
>   }
>   
> +static int nvme_fetch_fdp_plids(struct nvme_ns *ns, u32 nsid)
> +{
> +	struct nvme_fdp_ruh_status_desc *ruhsd;
> +	struct nvme_ns_head *head = ns->head;
> +	struct nvme_fdp_ruh_status *ruhs;
> +	struct nvme_command c = {};
> +	int size, ret, i;
> +
> +	if (head->plids)
> +		return 0;
> +
> +	size = struct_size(ruhs, ruhsd, NVME_MAX_PLIDS);
> +	ruhs = kzalloc(size, GFP_KERNEL);
> +	if (!ruhs)
> +		return -ENOMEM;
> +
> +	c.imr.opcode = nvme_cmd_io_mgmt_recv;
> +	c.imr.nsid = cpu_to_le32(nsid);
> +	c.imr.mo = 0x1;

can we please add some comment where values are hardcoded ?

> +	c.imr.numd =  cpu_to_le32((size >> 2) - 1);
> +
> +	ret = nvme_submit_sync_cmd(ns->queue, &c, ruhs, size);
> +	if (ret)
> +		goto out;
> +
> +	i = le16_to_cpu(ruhs->nruhsd);

instead of i why can't we use local variable nr_plids ?



> +	if (!i)
> +		goto out;
> +
> +	ns->head->nr_plids = min_t(u16, i, NVME_MAX_PLIDS);
> +	head->plids = kcalloc(ns->head->nr_plids, sizeof(head->plids),
> +			      GFP_KERNEL);
> +	if (!head->plids) {
> +		ret = -ENOMEM;
> +		goto out;
> +	}
> +
> +	for (i = 0; i < ns->head->nr_plids; i++) {
> +		ruhsd = &ruhs->ruhsd[i];
> +		head->plids[i] = le16_to_cpu(ruhsd->pid);
> +	}
> +out:
> +	kfree(ruhs);
> +	return ret;
> +}
> +
>   static int nvme_update_ns_info_block(struct nvme_ns *ns,
>   		struct nvme_ns_info *info)
>   {
> @@ -2141,6 +2209,19 @@ static int nvme_update_ns_info_block(struct nvme_ns *ns,
>   			goto out;
>   	}
>   
> +	if (ns->ctrl->ctratt & NVME_CTRL_ATTR_FDPS) {
> +		ret = nvme_fetch_fdp_plids(ns, info->nsid);
> +		if (ret)
> +			dev_warn(ns->ctrl->device,
> +				"FDP failure status:0x%x\n", ret);
> +		if (ret < 0)
> +			goto out;
> +	} else {
> +		ns->head->nr_plids = 0;
> +		kfree(ns->head->plids);
> +		ns->head->plids = NULL;
> +	}
> +
>   	blk_mq_freeze_queue(ns->disk->queue);
>   	ns->head->lba_shift = id->lbaf[lbaf].ds;
>   	ns->head->nuse = le64_to_cpu(id->nuse);
> @@ -2171,6 +2252,9 @@ static int nvme_update_ns_info_block(struct nvme_ns *ns,
>   	if (!nvme_init_integrity(ns->head, &lim, info))
>   		capacity = 0;
>   
> +	lim.max_write_hints = ns->head->nr_plids;
> +	if (lim.max_write_hints)
> +		lim.features |= BLK_FEAT_PLACEMENT_HINTS;
>   	ret = queue_limits_commit_update(ns->disk->queue, &lim);
>   	if (ret) {
>   		blk_mq_unfreeze_queue(ns->disk->queue);
> diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
> index 093cb423f536b..cec8e5d96377b 100644
> --- a/drivers/nvme/host/nvme.h
> +++ b/drivers/nvme/host/nvme.h
> @@ -454,6 +454,8 @@ struct nvme_ns_ids {
>   	u8	csi;
>   };
>   
> +#define NVME_MAX_PLIDS   (NVME_CTRL_PAGE_SIZE / sizeof(16))

this calculates how many plids can fit into the ctrl page size ?

sorry but I didn't understand sizeof(16) here, since plids are u16

nvme_ns_head -> u16 *plidsshould this be sizeof(u16) ? -ck