linux-kernel - RE: [PATCH v5 0/7] fsdax,xfs: Add reflink&dedupe support for fsdax

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Date:   Tue, 11 May 2021 05:53:51 +0000
From:   "ruansy.fnst@...itsu.com" <ruansy.fnst@...itsu.com>
To:     "Darrick J. Wong" <djwong@...nel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-xfs@...r.kernel.org" <linux-xfs@...r.kernel.org>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "darrick.wong@...cle.com" <darrick.wong@...cle.com>,
        "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "willy@...radead.org" <willy@...radead.org>,
        "viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>,
        "david@...morbit.com" <david@...morbit.com>,
        "hch@....de" <hch@....de>, "rgoldwyn@...e.de" <rgoldwyn@...e.de>
Subject: RE: [PATCH v5 0/7] fsdax,xfs: Add reflink&dedupe support for fsdax

> -----Original Message-----
> From: Darrick J. Wong <djwong@...nel.org>
> Sent: Tuesday, May 11, 2021 11:57 AM
> Subject: Re: [PATCH v5 0/7] fsdax,xfs: Add reflink&dedupe support for fsdax
> 
> On Tue, May 11, 2021 at 11:09:26AM +0800, 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.
> 
> Slightly off topic, but I noticed all my pmem disappeared once I rolled forward to
> 5.13-rc1.  Am I the only lucky one?  Qemu 4.2, with fake memory devices
> backed by tmpfs files -- info qtree says they're there, but the kernel doesn't show
> anything in /proc/iomem.

I have the same situation on 5.13-rc1 too. (Qemu 5.2.0, fake memory device backed by files)
I tested this code in v5.12-rc8 and then rebased it to v5.13-rc1...  It's my bad for not testing again.


--
Thanks,
Ruan Shiyang.
> 
> --D
> 
> > Changes from V4:
> >  - Fix the mistake of breaking dax layout for two inodes
> >  - Add CONFIG_FS_DAX judgement for fsdax code in remap_range.c
> >  - Fix other small problems and mistakes
> >
> > Changes from V3:
> >  - Take out the first 3 patches as a cleanup patchset[1], which has been
> >     sent yesterday.
> >  - Fix usage of code in dax_iomap_cow_copy()
> >  - Add comments for macro definitions
> >  - Fix other code style problems and mistakes
> >
> > 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 mechanisms 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.
> >
> >
> > (Rebased on v5.13-rc1 and patchset[1])
> > [1]: https://lkml.org/lkml/2021/4/22/575
> >
> > Shiyang Ruan (7):
> >   fsdax: Introduce dax_iomap_cow_copy()
> >   fsdax: Replace mmap entry in case of CoW
> >   fsdax: Add dax_iomap_cow_copy() for dax_iomap_zero
> >   iomap: Introduce iomap_apply2() for operations on two files
> >   fsdax: Dedup file range to use a compare function
> >   fs/xfs: Handle CoW for fsdax write() path
> >   fs/xfs: Add dax dedupe support
> >
> >  fs/dax.c               | 206
> +++++++++++++++++++++++++++++++++++------
> >  fs/iomap/apply.c       |  52 +++++++++++
> >  fs/iomap/buffered-io.c |   2 +-
> >  fs/remap_range.c       |  57 ++++++++++--
> >  fs/xfs/xfs_bmap_util.c |   3 +-
> >  fs/xfs/xfs_file.c      |  11 +--
> >  fs/xfs/xfs_inode.c     |  66 ++++++++++++-
> >  fs/xfs/xfs_inode.h     |   1 +
> >  fs/xfs/xfs_iomap.c     |  61 +++++++++++-
> >  fs/xfs/xfs_iomap.h     |   4 +
> >  fs/xfs/xfs_iops.c      |   7 +-
> >  fs/xfs/xfs_reflink.c   |  15 +--
> >  include/linux/dax.h    |   7 +-
> >  include/linux/fs.h     |  12 ++-
> >  include/linux/iomap.h  |   7 +-
> >  15 files changed, 449 insertions(+), 62 deletions(-)
> >
> > --
> > 2.31.1
> >
> >
> >