Re: [RFC PATCH 2/3] dax/cxl: add existing dc extents when probing dax region

[Ira Weiny <ira.weiny@intel.com>]

anisa.su887@ wrote:
> From: Fan Ni <fan.ni@samsung.com>
> 
> Add existing dc extents on the device before probing dax region will
> cause the creation of the dax device fail as resource cannot present
> when driver is bound to the device as shown in really_probe().

It's been a while since I've looked at this but the above explanation is
not clear to me.

There can't be dax devices on a region before region devices.  So how is a
dax device driver preventing the creation of a resource while the region
is being probed?

> 
> We delay the processing of existing dc extents to cxl region driver

NIT: Don't use 'we'.  Just say:

"Delay the processing..."

> probe.
> 
> Question: the guard() in cxlr_notify_extent() will cause lock issue,
> removed it. Not sure whether it will cause issue or not although no
> issue is observed during test.
> 
> Signed-off-by: Fan Ni <nifan.cxl@gmail.com>
> Tested-by: Anisa Su <anisa.su@samsung.com>
> Tested-by: Dongjoo Seo <dongjoo.seo1@samsung.com>
> ---
>  drivers/cxl/core/extent.c |  2 +-
>  drivers/cxl/core/region.c |  8 ++------
>  drivers/cxl/cxl.h         |  5 +++++
>  drivers/dax/cxl.c         | 24 +++++++-----------------
>  4 files changed, 15 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/cxl/core/extent.c b/drivers/cxl/core/extent.c
> index 3e7295d3e5e2..3b0e4d72d4ac 100644
> --- a/drivers/cxl/core/extent.c
> +++ b/drivers/cxl/core/extent.c
> @@ -285,7 +285,7 @@ static int cxlr_notify_extent(struct cxl_region *cxlr, enum dc_event event,
>  	dev_dbg(dev, "Trying notify: type %d HPA %pra\n", event,
>  		&region_extent->hpa_range);
>  
> -	guard(device)(dev);
> +	// guard(device)(dev);

This must remain to check for the driver notify callback.

I'm totally willing to admit there might be issues with this code but I'm
not clear what problem this patch is fixing.  Perhaps some more details?

Ira

[snip]