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    Block driver using virtio. · e467cde2
    Rusty Russell 提交于
    The block driver uses scatter-gather lists with sg[0] being the
    request information (struct virtio_blk_outhdr) with the type, sector
    and inbuf id.  The next N sg entries are the bio itself, then the last
    sg is the status byte.  Whether the N entries are in or out depends on
    whether it's a read or a write.
    
    We accept the normal (SCSI) ioctls: they get handed through to the other
    side which can then handle it or reply that it's unsupported.  It's
    not clear that this actually works in general, since I don't know
    if blk_pc_request() requests have an accurate rq_data_dir().
    
    Although we try to reply -ENOTTY on unsupported commands, ioctl(fd,
    CDROMEJECT) returns success to userspace.  This needs a separate
    patch.
    Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>
    Cc: Jens Axboe <jens.axboe@oracle.com>
    e467cde2
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