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Date: Fri, 18 Jan 2019 13:03:33 +0800
From: Wei Yang <richardw.yang@linux.intel.com>
Subject: Re: [PATCH] libnvdimm, pfn: not allocate nd_pfn->pfn_sb if already
 allocated
Message-ID: <20190118050333.GA4233@richard>
References: <20190118033544.3980-1-richardw.yang@linux.intel.com>
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To: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <zwisler@kernel.org>, linux-nvdimm <linux-nvdimm@lists.01.org>
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On Thu, Jan 17, 2019 at 08:31:56PM -0800, Dan Williams wrote:
>On Thu, Jan 17, 2019 at 7:36 PM Wei Yang <richardw.yang@linux.intel.com> wrote:
>>
>> In current implementation, we might re-allocate nd_pfn->pfn_sb.
>>
>> For example:
>>
>>     nd_dax_probe()
>>         nd_pfn->pfn_sb = devm_kzalloc()
>>
>>     dax_pmem_probe()
>>         nvdimm_setup_pfn()
>>             nd_pfn_init()
>>                 nd_pfn->pfn_sb = devm_kzalloc()
>>
>> This patch checks nd_pfn->pfn_sb before allocating it in nd_pfn_init().
>
>Ugh, this patch is unfortunately uncovering a deeper problem.
>nvdimm_setup_pfn() should not be calling nd_pfn_init(). This
>effectively is always re-initializing the info-block, benign but
>unnecessary. Instead it needs to be using nd_pfn_validate() followed
>by an __nvdimm_setup_pfn() in the dax_pmem_probe() path.
>
>Good find!

So we should fix this like:

dax_pmem_probe()
    nd_pfn_validate()
    __nvdimm_setup_pfn()

Is my understanding correct?

-- 
Wei Yang
Help you, Help me
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