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    SubjectRe: [patch 4/6] mm: merge populate and nopage into fault (fixes nonlinear)
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    > > If it doesn't look very impressive, it could be because it leaves all 
    > > the old crud around for backwards compatibility (the worst offenders
    > > are removed in patch 6/6).
    > >
    > > If you look at the patchset as a whole, it removes about 250 lines,
    > > mostly of (non trivial) duplicated code in filemap.c memory.c shmem.c
    > > fremap.c, that is nonlinear pages specific and doesn't get anywhere
    > > near the testing that the linear fault path does.
    > >
    > > A minimal fix for nonlinear pages would have required changing all
    > > ->populate handlers, which I simply thought was not very productive
    > > considering the testing and coverage issues, and that I was going to
    > > rewrite the nonlinear path anyway.
    > >
    > > If you like, you can consider patches 1,2,3 as the fix, and ignore
    > > nonlinear (hey, it doesn't even bother checking truncate_count
    > > today!).
    > >
    > > Then 4,5,6 is the fault/nonlinear rewrite, take it or leave it. I
    > > thought you would have liked the patches...
    >
    > btw., if we decide that nonlinear isnt worth the continuing maintainance
    > pain, we could internally implement/emulate sys_remap_file_pages() via a
    > call to mremap() and essentially deprecate it, without breaking the ABI
    > - and remove all the nonlinear code. (This would split fremap areas into
    > separate vmas)

    That would make sense. Dirty page accounting doesn't work either on
    non-linear mappings, and I can't see how that could be fixed in any
    other way.

    Miklos
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