linux-kernel - Re: [RFC PATCH v2 0/6] fsdax: introduce fs query to support reflink

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Date:   Tue, 15 Dec 2020 11:05:07 -0800
From:   Jane Chu <jane.chu@...cle.com>
To:     Ruan Shiyang <ruansy.fnst@...fujitsu.com>,
        linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-mm@...ck.org
Cc:     linux-fsdevel@...r.kernel.org, linux-raid@...r.kernel.org,
        darrick.wong@...cle.com, dan.j.williams@...el.com,
        david@...morbit.com, hch@....de, song@...nel.org, rgoldwyn@...e.de,
        qi.fuli@...itsu.com, y-goto@...itsu.com
Subject: Re: [RFC PATCH v2 0/6] fsdax: introduce fs query to support reflink

On 12/15/2020 3:58 AM, Ruan Shiyang wrote:
> Hi Jane
> 
> On 2020/12/15 上午4:58, Jane Chu wrote:
>> Hi, Shiyang,
>>
>> On 11/22/2020 4:41 PM, Shiyang Ruan wrote:
>>> This patchset is a try to resolve the problem of tracking shared page
>>> for fsdax.
>>>
>>> Change from v1:
>>>    - Intorduce ->block_lost() for block device
>>>    - Support mapped device
>>>    - Add 'not available' warning for realtime device in XFS
>>>    - Rebased to v5.10-rc1
>>>
>>> This patchset moves owner tracking from dax_assocaite_entry() to pmem
>>> device, by introducing an interface ->memory_failure() of struct
>>> pagemap.  The interface is called by memory_failure() in mm, and
>>> implemented by pmem device.  Then pmem device calls its ->block_lost()
>>> to find the filesystem which the damaged page located in, and call
>>> ->storage_lost() to track files or metadata assocaited with this page.
>>> Finally we are able to try to fix the damaged data in filesystem and do
>>
>> Does that mean clearing poison? if so, would you mind to elaborate 
>> specifically which change does that?
> 
> Recovering data for filesystem (or pmem device) has not been done in 
> this patchset...  I just triggered the handler for the files sharing the 
> corrupted page here.

Thanks! That confirms my understanding.

With the framework provided by the patchset, how do you envision it to
ease/simplify poison recovery from the user's perspective?

And how does it help in dealing with page faults upon poisoned
dax page?

thanks!
-jane