linux-kernel - Re: [Linux-nvdimm] [PATCH v2 10/20] pmem: use ida

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Date:	Wed, 29 Apr 2015 12:25:34 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	Dan Williams <dan.j.williams@...el.com>
Cc:	linux-nvdimm@...ts.01.org, Christoph Hellwig <hch@....de>,
	linux-kernel@...r.kernel.org
Subject: Re: [Linux-nvdimm] [PATCH v2 10/20] pmem: use ida

Hi Dan,

Thanks for the update.  This version of the patchset enumerates our NFIT
table properly. :-)

On Tue, 2015-04-28 at 14:25 -0400, Dan Williams wrote:
> In preparation for the pmem driver attaching to pmem-namespaces emitted
> by libnd, convert it to use an ida instead of an always increasing
> atomic index.  This provides a bit of stability to pmem device names in
> the presence of driver re-bind events.
  :
> @@ -122,20 +123,26 @@ static struct pmem_device *pmem_alloc(struct device *dev, struct resource *res)
>  {
>  	struct pmem_device *pmem;
>  	struct gendisk *disk;
> -	int idx, err;
> +	int err;
>  
>  	err = -ENOMEM;
>  	pmem = kzalloc(sizeof(*pmem), GFP_KERNEL);
>  	if (!pmem)
>  		goto out;
>  
> +	pmem->id = ida_simple_get(&pmem_ida, 0, 0, GFP_KERNEL);

nd_pmem_probe() is called asynchronously via async_schedule_domain
().  We have seen a case that the region#->pmem# binding becomes
inconsistent across a reboot when there are 8 NVDIMM cards (reported by
Robert Elliott).  This leads user to access a wrong device.

I think pmem id needs to be assigned before async_schedule_domain(), and
cascaded to nd_pmem_probe().

-Toshi




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