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

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