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

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Message-ID: <20250623100520.00003f34@huawei.com>
Date: Mon, 23 Jun 2025 10:05:20 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Neeraj Kumar <s.neeraj@...sung.com>
CC: <dan.j.williams@...el.com>, <dave@...olabs.net>, <dave.jiang@...el.com>,
	<alison.schofield@...el.com>, <vishal.l.verma@...el.com>,
	<ira.weiny@...el.com>, <a.manzanares@...sung.com>, <nifan.cxl@...il.com>,
	<anisa.su@...sung.com>, <vishak.g@...sung.com>, <krish.reddy@...sung.com>,
	<arun.george@...sung.com>, <alok.rathore@...sung.com>,
	<neeraj.kernel@...il.com>, <linux-kernel@...r.kernel.org>,
	<linux-cxl@...r.kernel.org>, <nvdimm@...ts.linux.dev>,
	<gost.dev@...sung.com>, <cpgs@...sung.com>
Subject: Re: [RFC PATCH 05/20] nvdimm/region_label: Add region label
 updation routine

On Tue, 17 Jun 2025 18:09:29 +0530
Neeraj Kumar <s.neeraj@...sung.com> wrote:

Add region label update routine


> Added __pmem_region_label_update region label update routine to update
> region label
> 
> Signed-off-by: Neeraj Kumar <s.neeraj@...sung.com>
A few trivial comments inline. 

Jonathan

> ---
>  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)
> +{
> +	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);

Perhaps use

	guard(mutex)(&nd_mapping->lock);

so you can directly return in the error path below and simplify the flow
a tiny bit.

> +	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);
> +
With guard this can be 
	if (rc)
		return rec;

	list_for_each...

> +	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;
> +}