[PATCHv13 10/11] nvme: register fdp parameters with the block layer

[Keith Busch]

On Wed, Dec 11, 2024 at 09:30:37AM +0000, John Garry wrote:
> On 10/12/2024 19:47, Keith Busch wrote:
> > +static int nvme_query_fdp_granularity(struct nvme_ctrl *ctrl,
> > +				      struct nvme_ns_info *info, u8 fdp_idx)
> > +{
> > +	struct nvme_fdp_config_log hdr, *h;
> > +	struct nvme_fdp_config_desc *desc;
> > +	size_t size = sizeof(hdr);
> > +	int i, n, ret;
> > +	void *log;
> > +
> > +	ret = nvme_get_log_lsi(ctrl, 0, NVME_LOG_FDP_CONFIGS, 0,
> > +			       NVME_CSI_NVM, &hdr, size, 0, info->endgid);
> > +	if (ret) {
> > +		dev_warn(ctrl->device,
> > +			 "FDP configs log header status:0x%x endgid:%x\n", ret,
> > +			 info->endgid);
> 
> About endgid, I guess that there is a good reason but sometimes "0x" is
> prefixed for hex prints and sometimes not. Maybe no prefix is used when we
> know that the variable is to hold a value from a HW register / memory
> structure - I don't know.

%d for endgid is probably a better choice.
 
> further nitpicking: And ret holds a kernel error code - the driver seems
> inconsistent for printing this. Sometimes it's %d and sometimes 0x%x.

It's either an -errno or an nvme status. "%x" is easier to decode if
it's an nvme status, which is probably the more interesting case to
debug.
 
> > +		return ret;
> > +	}
> > +
> > +	size = le32_to_cpu(hdr.sze);
> > +	h = kzalloc(size, GFP_KERNEL);
> > +	if (!h) {
> > +		dev_warn(ctrl->device,
> > +			 "failed to allocate %lu bytes for FDP config log\n",
> > +			 size);
> 
> do we normally print ENOMEM messages? I see that the bytes is printed, but I
> assume that this is a sane value (of little note).

I suppose not.

> > +		return -ENOMEM;
> > +	}
> > +
> > +	ret = nvme_get_log_lsi(ctrl, 0, NVME_LOG_FDP_CONFIGS, 0,
> > +			       NVME_CSI_NVM, h, size, 0, info->endgid);
> > +	if (ret) {
> > +		dev_warn(ctrl->device,
> > +			 "FDP configs log status:0x%x endgid:%x\n", ret,
> > +			 info->endgid);
> > +		goto out;
> > +	}
> > +
> > +	n = le16_to_cpu(h->numfdpc) + 1;
> > +	if (fdp_idx > n) {
> > +		dev_warn(ctrl->device, "FDP index:%d out of range:%d\n",
> > +			 fdp_idx, n);
> > +		/* Proceed without registering FDP streams */> +		ret = 0;
> 
> nit: maybe you want to be explicit, but logically ret is already 0

Yeah, we know its zero already, but there are static analyisis tools
that think returning without setting an error return code was a mistake,
and that we really meant to return something else like -EINVAL. We
definitely want to return 0 here, so this setting exists only to prevent
future "help".