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    SubjectRe: [PATCH 22/23] fs: default to generic_file_splice_read for files having ->read_iter
    On Tue, Jul 07, 2020 at 07:48:00PM +0200, Christoph Hellwig wrote:
    > If a file implements the ->read_iter method, the iter based splice read
    > works and is always preferred over the ->read based one. Use it by
    > default in do_splice_to and remove all the direct assignment of
    > generic_file_splice_read to file_operations.

    The worst problem here is the assumption that all ->read_iter() instances
    will take pipe-backed destination; that's _not_ automatically true.
    In particular, it's almost certainly false for tap_read_iter() (as
    well as tun_chr_read_iter() in IFF_VNET_HDR case).

    Other potentially interesting cases: cuse and hugetlbfs.

    But in any case, that blind assertion ("iter based splice read works")
    really needs to be backed by something.

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