Re: [RFC PATCH v2 0/7] xfs: reflink & dedupe for fsdax (read/write path).

[Shiyang Ruan]

On 10/30/19 7:48 PM, Goldwyn Rodrigues wrote:
> On 12:13 30/10, Shiyang Ruan wrote:
> > This patchset aims to take care of this issue to make reflink and dedupe
> > work correctly (actually in read/write path, there still has some problems,
> > such as the page->mapping and page->index issue, in mmap path) in XFS under
> > fsdax mode.
>
> Have you managed to solve the problem of multi-mapped pages? I don't
> think we can include this until we solve that problem. This is the
> problem I faced when I was doing the btrfs dax support.

That problem still exists, didn't be solved in this patchset.  But I am 
also looking into it.  As you know, it's a bit difficult.

Since the iomap for cow is merged in for-next tree, I think it's time to 
update this in order to get some comments.

> Suppose there is an extent shared with multiple files. You map data for
> both files. Which inode should page->mapping->host (precisely
> page->mapping) point to? As Dave pointed out, this needs to be fixed at
> the mm level, and will not only benefit dax with CoW but other
> areas such as overlayfs and possibly containers.

Yes, I will try to figure out a solution.
>

--
Thanks,
Shiyang Ruan.