linux-kernel - Re: [PATCH 0/7] fsdax,xfs: Add reflink&dedupe support for fsdax

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Message-ID: <31e9aa48-7830-efe2-837f-e31cba2da491@cn.fujitsu.com>
Date:   Tue, 9 Feb 2021 09:50:58 +0800
From:   Ruan Shiyang <ruansy.fnst@...fujitsu.com>
To:     Jan Kara <jack@...e.cz>
CC:     <linux-kernel@...r.kernel.org>, <linux-xfs@...r.kernel.org>,
        <linux-nvdimm@...ts.01.org>, <linux-fsdevel@...r.kernel.org>,
        <darrick.wong@...cle.com>, <dan.j.williams@...el.com>,
        <willy@...radead.org>, <viro@...iv.linux.org.uk>,
        <linux-btrfs@...r.kernel.org>, <ocfs2-devel@....oracle.com>,
        <david@...morbit.com>, <hch@....de>, <rgoldwyn@...e.de>
Subject: Re: [PATCH 0/7] fsdax,xfs: Add reflink&dedupe support for fsdax



On 2021/2/8 下午11:39, Jan Kara wrote:
> On Mon 08-02-21 01:09:17, Shiyang Ruan wrote:
>> This patchset is attempt to add CoW support for fsdax, and take XFS,
>> which has both reflink and fsdax feature, as an example.
>>
>> One of the key mechanism need to be implemented in fsdax is CoW.  Copy
>> the data from srcmap before we actually write data to the destance
>> iomap.  And we just copy range in which data won't be changed.
>>
>> Another mechanism is range comparison .  In page cache case, readpage()
>> is used to load data on disk to page cache in order to be able to
>> compare data.  In fsdax case, readpage() does not work.  So, we need
>> another compare data with direct access support.
>>
>> With the two mechanism implemented in fsdax, we are able to make reflink
>> and fsdax work together in XFS.
>>
>> Some of the patches are picked up from Goldwyn's patchset.  I made some
>> changes to adapt to this patchset.
> 
> How do you deal with HWPoison code trying to reverse-map struct page back
> to inode-offset pair? This also needs to be fixed for reflink to work with
> DAX.
> 

I have posted v3 patchset to add reverse-map support for dax page 
yesterday.  Please take a look at this:

   https://lkml.org/lkml/2021/2/8/347


--
Thanks,
Ruan Shiyang.

> 								Honza
> 
>>
>> (Rebased on v5.10)
>> ==
>>
>> Shiyang Ruan (7):
>>    fsdax: Output address in dax_iomap_pfn() and rename it
>>    fsdax: Introduce dax_copy_edges() for CoW
>>    fsdax: Copy data before write
>>    fsdax: Replace mmap entry in case of CoW
>>    fsdax: Dedup file range to use a compare function
>>    fs/xfs: Handle CoW for fsdax write() path
>>    fs/xfs: Add dedupe support for fsdax
>>
>>   fs/btrfs/reflink.c     |   3 +-
>>   fs/dax.c               | 188 ++++++++++++++++++++++++++++++++++++++---
>>   fs/ocfs2/file.c        |   2 +-
>>   fs/remap_range.c       |  14 +--
>>   fs/xfs/xfs_bmap_util.c |   6 +-
>>   fs/xfs/xfs_file.c      |  30 ++++++-
>>   fs/xfs/xfs_inode.c     |   8 +-
>>   fs/xfs/xfs_inode.h     |   1 +
>>   fs/xfs/xfs_iomap.c     |   3 +-
>>   fs/xfs/xfs_iops.c      |  11 ++-
>>   fs/xfs/xfs_reflink.c   |  23 ++++-
>>   include/linux/dax.h    |   5 ++
>>   include/linux/fs.h     |   9 +-
>>   13 files changed, 270 insertions(+), 33 deletions(-)
>>
>> -- 
>> 2.30.0
>>
>>
>>