Re: [PATCH 17/26] dax/region: Create extent resources on DAX region driver load

Jonathan Cameron
2024-04-04T16:36:31Z

On Sun, 24 Mar 2024 16:18:20 -0700
ira.weiny@intel.com wrote:

> From: Navneet Singh <navneet.singh@intel.com>
>
> DAX regions mapping dynamic capacity partitions introduce a requirement
> for the memory backing the region to come and go as required. This
> results in a DAX region with sparse areas of memory backing. To track
> the sparseness of the region, DAX extent objects need to track
> sub-resource information as a new layer between the DAX region resource
> and DAX device range resources.
>
> Recall that DCD extents may be accepted when a region is first created.
> Extend this support on region driver load. Scan existing extents and
> create DAX extent resources as a first step to DAX extent realization.
>
> The lifetime of a DAX extent is tricky to manage because the extent life
> may end in one of two ways. First, the device may request the extent be
> released. Second, the region may release the extent when it is
> destroyed without hardware involvement. Support extent release without
> hardware involvement first. Subsequent patches will provide for
> hardware to request extent removal.
>
> Signed-off-by: Navneet Singh <navneet.singh@intel.com>
> Co-developed-by: Ira Weiny <ira.weiny@intel.com>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
LGTM though I'm far from an expert on DAX..

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

>
> ---
> Changes for v1
> [iweiny: remove xarrays]
> [iweiny: remove as much of extra reference stuff as possible]
> [iweiny: Move extent resource handling to core DAX code]
> ---
> drivers/dax/bus.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++
> drivers/dax/cxl.c | 43 ++++++++++++++++++++++++++++++++++--
> drivers/dax/dax-private.h | 12 +++++++++++
> 3 files changed, 108 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
> index 903566aff5eb..4d5ed7ab6537 100644
> --- a/drivers/dax/bus.c
> +++ b/drivers/dax/bus.c
> @@ -186,6 +186,61 @@ static bool is_sparse(struct dax_region *dax_region)
> return (dax_region->res.flags & IORESOURCE_DAX_SPARSE_CAP) != 0;
> }
>
> +static int dax_region_add_resource(struct dax_region *dax_region,
> + struct dax_extent *dax_ext,
> + resource_size_t start,
> + resource_size_t length)
> +{
> + struct resource *ext_res;
> +
> + dev_dbg(dax_region->dev, "DAX region resource %pr\n", &dax_region->res);
> + ext_res = __request_region(&dax_region->res, start, length, "extent", 0);
> + if (!ext_res) {
> + dev_err(dax_region->dev, "Failed to add region s:%pa l:%pa\n",
> + &start, &length);
> + return -ENOSPC;
> + }
> +
> + dax_ext->region = dax_region;
> + dax_ext->res = ext_res;
> + dev_dbg(dax_region->dev, "Extent add resource %pr\n", ext_res);
> +
> + return 0;
> +}