Re: [RFC PATCH 0/8] fsdax: introduce FS query interface to support reflink

[Ruan Shiyang]

On 2020/8/7 下午9:38, Matthew Wilcox wrote:
> On Fri, Aug 07, 2020 at 09:13:28PM +0800, Shiyang Ruan wrote:
> > This patchset is a try to resolve the problem of tracking shared page
> > for fsdax.
> >
> > Instead of per-page tracking method, this patchset introduces a query
> > interface: get_shared_files(), which is implemented by each FS, to
> > obtain the owners of a shared page.  It returns an owner list of this
> > shared page.  Then, the memory-failure() iterates the list to be able
> > to notify each process using files that sharing this page.
> >
> > The design of the tracking method is as follow:
> > 1. dax_assocaite_entry() associates the owner's info to this page
>
> I think that's the first problem with this design.  dax_associate_entry is
> a horrendous idea which needs to be ripped out, not made more important.
> It's all part of the general problem of trying to do something on a
> per-page basis instead of per-extent basis.

The memory-failure needs to track owners info from a dax page, so I 
should associate the owner with this page.  In this version, I associate 
the block device to the dax page, so that the memory-failure is able to 
iterate the owners by the query interface provided by filesystem.


--
Thanks,
Ruan Shiyang.
>