Re: [RFC PATCH 05/20] nvdimm/region_label: Add region label updation routine

[Neeraj Kumar]

On 18/07/25 12:53AM, Fabio M. De Francesco wrote:
> On Tuesday, June 17, 2025 2:39:29 PM Central European Summer Time Neeraj Kumar wrote:
> > Added __pmem_region_label_update region label update routine to update
> > region label
> >
> > Signed-off-by: Neeraj Kumar <s.neeraj@xxxxxxxxxxx>
> > ---
> >  drivers/nvdimm/label.c          | 142 ++++++++++++++++++++++++++++++++
> >  drivers/nvdimm/label.h          |   2 +
> >  drivers/nvdimm/namespace_devs.c |  12 +++
> >  drivers/nvdimm/nd.h             |  20 +++++
> >  include/linux/libnvdimm.h       |   8 ++
> >  5 files changed, 184 insertions(+)
> >
> > diff --git a/drivers/nvdimm/label.c b/drivers/nvdimm/label.c
> > index d5cfaa99f976..7f33d14ce0ef 100644
> > --- a/drivers/nvdimm/label.c
> > +++ b/drivers/nvdimm/label.c
> > @@ -381,6 +381,16 @@ static void nsl_calculate_checksum(struct nvdimm_drvdata *ndd,
> >  	nsl_set_checksum(ndd, nd_label, sum);
> >  }
> >
> > +static void rgl_calculate_checksum(struct nvdimm_drvdata *ndd,
> > +				   struct cxl_region_label *rg_label)
> > +{
> > +	u64 sum;
> > +
> > +	rgl_set_checksum(rg_label, 0);
> > +	sum = nd_fletcher64(rg_label, sizeof_namespace_label(ndd), 1);
> > +	rgl_set_checksum(rg_label, sum);
> > +}
> > +
> >  static bool slot_valid(struct nvdimm_drvdata *ndd,
> >  		struct nd_lsa_label *nd_label, u32 slot)
> >  {
> > @@ -1117,6 +1127,138 @@ int nd_pmem_namespace_label_update(struct nd_region *nd_region,
> >  	return 0;
> >  }
> >
> > +static int __pmem_region_label_update(struct nd_region *nd_region,
> > +		struct nd_mapping *nd_mapping, int pos, unsigned long flags)
>
> Hi Neeraj,
>
> I've noticed that __pmem_region_label_update() shares many similarities
> with the existing __pmem_label_update().

Hi Fabio,

Yes these functions looks similar, as one is updating namespace label
and other (__pmem_region_label_update) is updating region label. But
they don't use much duplicated code.

May be I will try refactoring to avoid any duplicate code.

> > +{
> > +	struct nd_interleave_set *nd_set = nd_region->nd_set;
> > +	struct nvdimm_drvdata *ndd = to_ndd(nd_mapping);
> > +	struct nd_lsa_label *nd_label;
> > +	struct cxl_region_label *rg_label;
> > +	struct nd_namespace_index *nsindex;
> > +	struct nd_label_ent *label_ent;
> > +	unsigned long *free;
> > +	u32 nslot, slot;
> > +	size_t offset;
> > +	int rc;
> > +	uuid_t tmp;
> > +
> > +	if (!preamble_next(ndd, &nsindex, &free, &nslot))
> > +		return -ENXIO;
> > +
> > +	/* allocate and write the label to the staging (next) index */
> > +	slot = nd_label_alloc_slot(ndd);
> > +	if (slot == UINT_MAX)
> > +		return -ENXIO;
> > +	dev_dbg(ndd->dev, "allocated: %d\n", slot);
> > +
> > +	nd_label = to_label(ndd, slot);
> > +
> > +	memset(nd_label, 0, sizeof_namespace_label(ndd));
> > +	rg_label = &nd_label->rg_label;
> > +
> > +	/* Set Region Label Format identification UUID */
> > +	uuid_parse(CXL_REGION_UUID, &tmp);
> > +	export_uuid(nd_label->rg_label.type, &tmp);
> > +
> > +	/* Set Current Region Label UUID */
> > +	export_uuid(nd_label->rg_label.uuid, &nd_set->uuid);
> > +
> > +	rg_label->flags = __cpu_to_le32(flags);
> > +	rg_label->nlabel = __cpu_to_le16(nd_region->ndr_mappings);
> > +	rg_label->position = __cpu_to_le16(pos);
> > +	rg_label->dpa = __cpu_to_le64(nd_mapping->start);
> > +	rg_label->rawsize = __cpu_to_le64(nd_mapping->size);
> > +	rg_label->hpa = __cpu_to_le64(nd_set->res->start);
> > +	rg_label->slot = __cpu_to_le32(slot);
> > +	rg_label->ig = __cpu_to_le32(nd_set->interleave_granularity);
> > +	rg_label->align = __cpu_to_le16(0);
> > +
> > +	/* Update fletcher64 Checksum */
> > +	rgl_calculate_checksum(ndd, rg_label);
> > +
> > +	/* update label */
> > +	offset = nd_label_offset(ndd, nd_label);
> > +	rc = nvdimm_set_config_data(ndd, offset, nd_label,
> > +			sizeof_namespace_label(ndd));
> > +	if (rc < 0) {
> > +		nd_label_free_slot(ndd, slot);
> > +		return rc;
> > +	}
> > +
> > +	/* Garbage collect the previous label */
> > +	mutex_lock(&nd_mapping->lock);
> > +	list_for_each_entry(label_ent, &nd_mapping->labels, list) {
> > +		if (!label_ent->label)
> > +			continue;
> > +		if (rgl_uuid_equal(&label_ent->label->rg_label, &nd_set->uuid))
> > +			reap_victim(nd_mapping, label_ent);
> > +	}
> > +
> > +	/* update index */
> > +	rc = nd_label_write_index(ndd, ndd->ns_next,
> > +			nd_inc_seq(__le32_to_cpu(nsindex->seq)), 0);
> > +
> > +	if (rc == 0) {
> > +		list_for_each_entry(label_ent, &nd_mapping->labels, list)
> > +			if (!label_ent->label) {
> > +				label_ent->label = nd_label;
> > +				nd_label = NULL;
> > +				break;
> > +			}
> > +		dev_WARN_ONCE(&nd_region->dev, nd_label,
> > +				"failed to track label: %d\n",
> > +				to_slot(ndd, nd_label));
> > +		if (nd_label)
> > +			rc = -ENXIO;
> > +	}
> > +	mutex_unlock(&nd_mapping->lock);
> > +
> > +	return rc;
> > +}
> > +
> > +int nd_pmem_region_label_update(struct nd_region *nd_region)
>
> Same here. nd_pmem_region_label_update() is almost identical to the
> existing nd_pmem_namespace_label_update.

Sure, I will try refactoring these in next patch-set.

> Although I'm not familiar with drivers/nvdimm, it seems preferable to
> reuse and adapt the existing functions to reduce redundancy and simplify
> future maintenance, unless there are specific reasons for not doing so
> that I'm unaware of.
>
> Thanks,
>
> Fabio

Thanks Fabio for your feedback.

Regards,
Neeraj