Re: [PATCH v6 4/7] libcxl: Add extent functionality to DC regions

[Dave Jiang]

On 5/23/26 2:50 AM, Anisa Su wrote:
> From: Ira Weiny <ira.weiny@xxxxxxxxx>
> 
> DCD regions have 0 or more extents.  The ability to list those and their
> properties is useful to end users.
> 
> Add extent scanning and reporting functionality to libcxl.
> 
> Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>

Missing Anisa sign-off


> 
> ---
> Changes:
> [alison: s/tag/uuid/ for extents]
> ---
>  Documentation/cxl/lib/libcxl.txt |  27 ++++++
>  cxl/lib/libcxl.c                 | 138 +++++++++++++++++++++++++++++++
>  cxl/lib/libcxl.sym               |   5 ++
>  cxl/lib/private.h                |  11 +++
>  cxl/libcxl.h                     |  11 +++
>  5 files changed, 192 insertions(+)
> 
> diff --git a/Documentation/cxl/lib/libcxl.txt b/Documentation/cxl/lib/libcxl.txt
> index 9921ac1..0ad294c 100644
> --- a/Documentation/cxl/lib/libcxl.txt
> +++ b/Documentation/cxl/lib/libcxl.txt
> @@ -635,6 +635,33 @@ where its properties can be interrogated by daxctl. The helper
>  cxl_region_get_daxctl_region() returns an 'struct daxctl_region *' that
>  can be used with other libdaxctl APIs.
>  
> +EXTENTS
> +-------
> +
> +=== EXTENT: Enumeration
> +----
> +struct cxl_region_extent;
> +struct cxl_region_extent *cxl_extent_get_first(struct cxl_region *region);
> +struct cxl_region_extent *cxl_extent_get_next(struct cxl_region_extent *extent);
> +#define cxl_extent_foreach(region, extent) \
> +        for (extent = cxl_extent_get_first(region); \
> +             extent != NULL; \
> +             extent = cxl_extent_get_next(extent))
> +
> +----
> +
> +=== EXTENT: Attributes
> +----
> +unsigned long long cxl_extent_get_offset(struct cxl_region_extent *extent);
> +unsigned long long cxl_extent_get_length(struct cxl_region_extent *extent);
> +void cxl_extent_get_uuid(struct cxl_region_extent *extent, uuid_t uuid);
> +----
> +
> +Extents represent available memory within a dynamic capacity region.  Extent
> +objects are available for informational purposes to aid in allocation of
> +memory.
> +
> +
>  include::../../copyright.txt[]
>  
>  SEE ALSO
> diff --git a/cxl/lib/libcxl.c b/cxl/lib/libcxl.c
> index be0bc03..c096666 100644
> --- a/cxl/lib/libcxl.c
> +++ b/cxl/lib/libcxl.c
> @@ -635,6 +635,7 @@ static void *add_cxl_region(void *parent, int id, const char *cxlregion_base)
>  	region->ctx = ctx;
>  	region->decoder = decoder;
>  	list_head_init(&region->mappings);
> +	list_head_init(&region->extents);
>  
>  	region->dev_path = strdup(cxlregion_base);
>  	if (!region->dev_path)
> @@ -1257,6 +1258,143 @@ cxl_mapping_get_next(struct cxl_memdev_mapping *mapping)
>  	return list_next(&region->mappings, mapping, list);
>  }
>  
> +static void cxl_extents_init(struct cxl_region *region)
> +{
> +	const char *devname = cxl_region_get_devname(region);
> +	struct cxl_ctx *ctx = cxl_region_get_ctx(region);
> +	char *extent_path, *dax_region_path;
> +	struct dirent *de;
> +	DIR *dir = NULL;
> +
> +	if (region->extents_init)
> +		return;
> +	region->extents_init = 1;
> +
> +	dax_region_path = calloc(1, strlen(region->dev_path) + 64);
> +	if (!dax_region_path) {
> +		err(ctx, "%s: allocation failure\n", devname);
> +		return;
> +	}
> +
> +	extent_path = calloc(1, strlen(region->dev_path) + 100);
> +	if (!extent_path) {
> +		err(ctx, "%s: allocation failure\n", devname);
> +		free(dax_region_path);
> +		return;
> +	}
> +
> +	sprintf(dax_region_path, "%s/dax_region%d",
> +		region->dev_path, region->id);
> +	dir = opendir(dax_region_path);
> +	if (!dir) {
> +		err(ctx, "no extents found (%s): %s\n",
> +			strerror(errno), dax_region_path);
> +		free(extent_path);
> +		free(dax_region_path);
> +		return;
> +	}
> +
> +	while ((de = readdir(dir)) != NULL) {
> +		struct cxl_region_extent *extent;
> +		char buf[SYSFS_ATTR_SIZE];
> +		u64 offset, length;
> +		int id, region_id;
> +
> +		if (sscanf(de->d_name, "extent%d.%d", &region_id, &id) != 2)
> +			continue;
> +
> +		sprintf(extent_path, "%s/extent%d.%d/offset",
> +			dax_region_path, region_id, id);
> +		if (sysfs_read_attr(ctx, extent_path, buf) < 0) {
> +			err(ctx, "%s: failed to read extent%d.%d/offset\n",
> +				devname, region_id, id);
> +			continue;
> +		}
> +
> +		offset = strtoull(buf, NULL, 0);
> +		if (offset == ULLONG_MAX) {
> +			err(ctx, "%s extent%d.%d: failed to read offset\n",
> +				devname, region_id, id);
> +			continue;
> +		}
> +
> +		sprintf(extent_path, "%s/extent%d.%d/length",
> +			dax_region_path, region_id, id);
> +		if (sysfs_read_attr(ctx, extent_path, buf) < 0) {
> +			err(ctx, "%s: failed to read extent%d.%d/length\n",
> +				devname, region_id, id);
> +			continue;
> +		}
> +
> +		length = strtoull(buf, NULL, 0);
> +		if (length == ULLONG_MAX) {
> +			err(ctx, "%s extent%d.%d: failed to read length\n",
> +				devname, region_id, id);
> +			continue;
> +		}
> +
> +		sprintf(extent_path, "%s/extent%d.%d/tag",
> +			dax_region_path, region_id, id);
> +		buf[0] = '\0';
> +		if (sysfs_read_attr(ctx, extent_path, buf) != 0)
> +			dbg(ctx, "%s extent%d.%d: failed to read uuid\n",
> +				devname, region_id, id);
> +
> +		extent = calloc(1, sizeof(*extent));
> +		if (!extent) {
> +			err(ctx, "%s extent%d.%d: allocation failure\n",
> +				devname, region_id, id);
> +			continue;
> +		}
> +		if (strlen(buf) && uuid_parse(buf, extent->uuid) < 0)
> +			err(ctx, "%s:%s\n", extent_path, buf);
> +		extent->region = region;
> +		extent->offset = offset;
> +		extent->length = length;
> +
> +		list_node_init(&extent->list);
> +		list_add(&region->extents, &extent->list);

free_region() never frees any of the extents allocated and added here and thus leak the memory when region is freed.


> +		dbg(ctx, "%s added extent%d.%d\n", devname, region_id, id);
> +	}
> +	free(dax_region_path);
> +	free(extent_path);
> +	closedir(dir);
> +}
> +
> +CXL_EXPORT struct cxl_region_extent *
> +cxl_extent_get_first(struct cxl_region *region)
> +{
> +	cxl_extents_init(region);
> +
> +	return list_top(&region->extents, struct cxl_region_extent, list);
> +}
> +
> +CXL_EXPORT struct cxl_region_extent *
> +cxl_extent_get_next(struct cxl_region_extent *extent)
> +{
> +	struct cxl_region *region = extent->region;
> +
> +	return list_next(&region->extents, extent, list);
> +}
> +
> +CXL_EXPORT unsigned long long
> +cxl_extent_get_offset(struct cxl_region_extent *extent)
> +{
> +	return extent->offset;
> +}
> +
> +CXL_EXPORT unsigned long long
> +cxl_extent_get_length(struct cxl_region_extent *extent)
> +{
> +	return extent->length;
> +}
> +
> +CXL_EXPORT void
> +cxl_extent_get_uuid(struct cxl_region_extent *extent, uuid_t uuid)
> +{
> +	memcpy(uuid, extent->uuid, sizeof(uuid_t));
> +}
> +
>  CXL_EXPORT struct cxl_decoder *
>  cxl_mapping_get_decoder(struct cxl_memdev_mapping *mapping)
>  {
> diff --git a/cxl/lib/libcxl.sym b/cxl/lib/libcxl.sym
> index 258bdd3..dcfe242 100644
> --- a/cxl/lib/libcxl.sym
> +++ b/cxl/lib/libcxl.sym
> @@ -298,6 +298,11 @@ global:
>  	cxl_memdev_get_dynamic_ram_a_qos_class;
>  	cxl_decoder_is_dynamic_ram_a_capable;
>  	cxl_decoder_create_dynamic_ram_a_region;
> +	cxl_extent_get_first;
> +	cxl_extent_get_next;
> +	cxl_extent_get_offset;
> +	cxl_extent_get_length;
> +	cxl_extent_get_uuid;
>  } LIBECXL_8;
>  
>  LIBCXL_10 {
> diff --git a/cxl/lib/private.h b/cxl/lib/private.h
> index 37b7b06..c5f3bed 100644
> --- a/cxl/lib/private.h
> +++ b/cxl/lib/private.h
> @@ -183,6 +183,7 @@ struct cxl_region {
>  	struct cxl_decoder *decoder;
>  	struct list_node list;
>  	int mappings_init;
> +	int extents_init;
>  	struct cxl_ctx *ctx;
>  	void *dev_buf;
>  	size_t buf_len;
> @@ -200,6 +201,7 @@ struct cxl_region {
>  	struct daxctl_region *dax_region;
>  	struct kmod_module *module;
>  	struct list_head mappings;
> +	struct list_head extents;
>  };
>  
>  struct cxl_memdev_mapping {
> @@ -209,6 +211,15 @@ struct cxl_memdev_mapping {
>  	struct list_node list;
>  };
>  
> +#define CXL_REGION_EXTENT_TAG 0x10

defined but never used

DJ

> +struct cxl_region_extent {
> +	struct cxl_region *region;
> +	u64 offset;
> +	u64 length;
> +	uuid_t uuid;
> +	struct list_node list;
> +};
> +
>  enum cxl_cmd_query_status {
>  	CXL_CMD_QUERY_NOT_RUN = 0,
>  	CXL_CMD_QUERY_OK,
> diff --git a/cxl/libcxl.h b/cxl/libcxl.h
> index fd41122..a60509f 100644
> --- a/cxl/libcxl.h
> +++ b/cxl/libcxl.h
> @@ -394,6 +394,17 @@ unsigned int cxl_mapping_get_position(struct cxl_memdev_mapping *mapping);
>               mapping != NULL; \
>               mapping = cxl_mapping_get_next(mapping))
>  
> +struct cxl_region_extent;
> +struct cxl_region_extent *cxl_extent_get_first(struct cxl_region *region);
> +struct cxl_region_extent *cxl_extent_get_next(struct cxl_region_extent *extent);
> +#define cxl_extent_foreach(region, extent) \
> +        for (extent = cxl_extent_get_first(region); \
> +             extent != NULL; \
> +             extent = cxl_extent_get_next(extent))
> +unsigned long long cxl_extent_get_offset(struct cxl_region_extent *extent);
> +unsigned long long cxl_extent_get_length(struct cxl_region_extent *extent);
> +void cxl_extent_get_uuid(struct cxl_region_extent *extent, uuid_t uuid);
> +
>  struct cxl_cmd;
>  const char *cxl_cmd_get_devname(struct cxl_cmd *cmd);
>  struct cxl_cmd *cxl_cmd_new_raw(struct cxl_memdev *memdev, int opcode);