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    SubjectRe: [PATCH] zap_pte_range should not mark non-uptodate pages dirty
    Andrew Morton <akpm@osdl.org> wrote:
    >
    > I don't get it. invalidate has the pageframe. All it need to do is to
    > lock the page, examine mapcount and if it's non-zero, do the shootdown.

    unmap_mapping_range() will do that - can call it one page at a time, or
    batch up runs of pages. It's not fast, but presumably not frequent either.

    The bigger problem is shooting down the buffer_heads. It's certainly the
    case that mpage_readpage() will call block_read_full_page() which will then
    bring the page uptodate without performing any I/O.

    And invalidating the buffer_heads in invalidate_inode_pages2() is tricky -
    we need to enter the filesystem and I'm not sure that either
    ->invalidatepage() or ->releasepage() are quite suitable. For a start,
    they're best-effort and may fail. If we just go and mark the buffers not
    uptodate we'll probably give ext3 a heart attack, so careful work would be
    needed there.

    Let's go back to why we needed all of this. Was it just for the NFS
    something-changed-on-the-server code? If so, would it be sufficient to add
    a new invalidate_inode_pages3() just for NFS, which clears the uptodate
    bit? Or something along those lines?

    -
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