linux-kernel - Re: [PATCH v10 7/8] xfs: support CoW in fsdax mode

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Date:   Thu, 14 Oct 2021 10:50:00 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     "Darrick J. Wong" <djwong@...nel.org>
Cc:     Shiyang Ruan <ruansy.fnst@...itsu.com>,
        Christoph Hellwig <hch@....de>,
        linux-xfs <linux-xfs@...r.kernel.org>,
        david <david@...morbit.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux NVDIMM <nvdimm@...ts.linux.dev>,
        Goldwyn Rodrigues <rgoldwyn@...e.de>,
        Al Viro <viro@...iv.linux.org.uk>,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH v10 7/8] xfs: support CoW in fsdax mode

On Thu, Oct 14, 2021 at 10:38 AM Darrick J. Wong <djwong@...nel.org> wrote:
>
> On Tue, Sep 28, 2021 at 02:23:10PM +0800, Shiyang Ruan wrote:
> > In fsdax mode, WRITE and ZERO on a shared extent need CoW performed.
> > After that, new allocated extents needs to be remapped to the file.
> > So, add a CoW identification in ->iomap_begin(), and implement
> > ->iomap_end() to do the remapping work.
> >
> > Signed-off-by: Shiyang Ruan <ruansy.fnst@...itsu.com>
>
> I think this patch looks good, so:
> Reviewed-by: Darrick J. Wong <djwong@...nel.org>
>
> A big thank you to Shiyang for persisting in getting this series
> finished! :)
>
> Judging from the conversation Christoph and I had the last time this
> patchset was submitted, I gather the last big remaining issue is the use
> of page->mapping for hw poison.  So I'll go take a look at "fsdax:
> introduce FS query interface to support reflink" now.

The other blocker was enabling mounting dax filesystems on a
dax-device rather than a block device. I'm actively refactoring the
nvdimm subsystem side of that equation, but could use help with the
conversion of the xfs mount path. Christoph, might you have that in
your queue?