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    SubjectRe: [v2 PATCH] mm: shmem: allow split THP when truncating THP partially
    On Wed, Feb 26, 2020 at 09:43:53AM -0800, Yang Shi wrote:
    > > No. The pagevec_lookup_entries() calls from mm/truncate.c prefer the
    > > new behavior - evicting the head from page cache removes all the tails
    > > along with it, so getting the tails a waste of time there too, just as
    > > it was in shmem_undo_range().
    >
    > TBH I'm not a fun of this hack. This would bring in other confusion or
    > complexity. Pagevec is supposed to count in the number of base page, now it
    > would treat THP as one page, and there might be mixed base page and THP in
    > one pagevec. But, I tend to agree avoiding getting those 14 extra pins at
    > the first place might be a better approach. All the complexity are used to
    > release those extra pins.

    My long-term goal is to eradicate tail pages entirely, so a pagevec will
    end up containing pages of different sizes. If you want to help move
    in this direction, I'd be awfully grateful. But I wouldn't say that's
    in any way a prerequisite for fixing this current problem.

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