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

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.