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IO split is usually bad in io_uring world, since -EAGAIN is caused and IO handling may have to fallback to io-wq, this way does hurt performance. ublk starts to support zero copy recently, for avoiding unnecessary IO split, ublk driver's segment limit should be aligned with backend device's segment limit. Another reason is that io_buffer_register_bvec() needs to allocate bvecs, which number is aligned with ublk request segment number, so that big memory allocation can be avoided by setting reasonable max_segments limit. So add segment parameter for providing ublk server chance to align segment limit with backend, and keep it reasonable from implementation viewpoint. Signed-off-by: Ming Lei <ming.lei@redhat.com> Link: https://lore.kernel.org/r/20250327095123.179113-7-ming.lei@redhat.com Signed-off-by: Jens Axboe <axboe@kernel.dk>