From mboxrd@z Thu Jan  1 00:00:00 1970
From: Boaz Harrosh <boaz@plexistor.com>
Subject: Re: [PATCH v2] dax: fix NULL pointer in __dax_pmd_fault()
Date: Thu, 24 Sep 2015 11:50:00 +0300
Message-ID: <5603B938.1@plexistor.com>
References: <1442950582-10140-1-git-send-email-ross.zwisler@linux.intel.com> <20150922141333.c28e3c5d800267937ca7b29a@linux-foundation.org> <CAPcyv4gDccBX4eNDzUo=wK10_Zk7D2XNiuVykW6xnhB-iOub8A@mail.gmail.com> <20150922233016.GH3902@dastard> <CAPcyv4idkToQv_KLoA63EAzQgDKo+Q3k4xvaHJQ-qOsjohCAJA@mail.gmail.com> <20150923090459.GO19114@dastard>
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Cc: linux-nvdimm <linux-nvdimm@ml01.01.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
To: Dave Chinner <david@fromorbit.com>,
	Dan Williams <dan.j.williams@intel.com>
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <20150923090459.GO19114@dastard>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: linux-fsdevel.vger.kernel.org

On 09/23/2015 12:04 PM, Dave Chinner wrote:
> On Tue, Sep 22, 2015 at 08:00:29PM -0700, Dan Williams wrote:
<>
>> The kaddr is coming from the devm_memremap() in the pmem driver that
>> gets unmapped after the device is released by the driver.
> 
> Perhaps the better solution is to not tear down the block device
> until all active references have gone away? i.e. unbind puts the
> device into a persistent error state and forces all active mappings
> to refault. Hence all future accesses error out and then when the
> user unmounts the unhappy filesystem the last reference to the
> blockdev goes away and the mappings can be torn down safely...
> 

Me too

> Cheers,
> 
> Dave.
>