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62fe99cef9
Support pread()/pwrite() on ublk char device for reading/writing request io buffer, so data copy between io request buffer and userspace buffer can be moved to ublk server from ublk driver. Then UBLK_F_NEED_GET_DATA becomes not necessary, so ublk server can allocate buffer without one extra round uring command communication for userspace to provide buffer. IO buffer can be located by iocb->ki_pos which encodes buffer offset, io tag and queue id info, and type of iocb->ki_pos is u64, so it is big enough for holding reasonable queue depth, nr_queues and max io buffer size. Signed-off-by: Ming Lei <ming.lei@redhat.com> Link: https://lore.kernel.org/r/20230519065030.351216-7-ming.lei@redhat.com Signed-off-by: Jens Axboe <axboe@kernel.dk>