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    SubjectRe: [patch 2/3] splice: implement default splice_read method
    On Thu, May 14 2009, Miklos Szeredi wrote:
    > On Thu, 14 May 2009, Jens Axboe wrote:
    >
    > > > The bigger problem is that the default_file_splice_write()
    > > > implementation in the other patch does the same (it calls
    > > > buf->ops->map() on all buffers).
    > >
    > > Yep that's even worse, as that should go BUG() pretty much immediately
    > > when the KM_USER0 slot is reused!
    >
    > No, ->map() calls plain kmap() if "atomic" argument is zero.
    > Nevertheless the deadlock due to multiple kmaps is still possible.

    It's buggy either way, didn't check whether you used atomic maps or not.

    > > > Hmm. Simple solution would be to do a write() for each buffer. But
    > > > this only affects HIGHMEM kernels, so it's a bit pointless to do that
    > > > on all archs. Sigh...
    > >
    > > It is unfortunate, we are going to be stuck with that for some time
    > > still...
    >
    > I'm going to be offline till next monday, I'll post a fix after that.

    Until monday, or the monday after? I'm tempted to revert the
    readv/writev part until this is settled, we cannot ship it as-is.

    --
    Jens Axboe



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