Re: [PATCH v9 10/10] fsdax: set a CoW flag when associate reflink mappings

[Shiyang Ruan]

在 2022/1/21 15:16, Christoph Hellwig 写道:
> On Fri, Jan 21, 2022 at 10:33:58AM +0800, Shiyang Ruan wrote:
> > > But different question, how does this not conflict with:
> > >
> > > #define PAGE_MAPPING_ANON       0x1
> > >
> > > in page-flags.h?
> >
> > Now we are treating dax pages, so I think its flags should be different from
> > normal page.  In another word, PAGE_MAPPING_ANON is a flag of rmap mechanism
> > for normal page, it doesn't work for dax page.  And now, we have dax rmap
> > for dax page.  So, I think this two kinds of flags are supposed to be used
> > in different mechanisms and won't conflect.
>
> It just needs someone to use folio_test_anon in a place where a DAX
> folio can be passed.  This probably should not happen, but we need to
> clearly document that.
>
> > > Either way I think this flag should move to page-flags.h and be
> > > integrated with the PAGE_MAPPING_FLAGS infrastucture.
> >
> > And that's why I keep them in this dax.c file.
>
> But that does not integrate it with the infrastructure.  For people
> to debug things it needs to be next to PAGE_MAPPING_ANON and have
> documentation explaining why they are exclusive.

Ok, understood.


--
Thanks,
Ruan.