Add unlikely() and likely() to optimize main I/O process code.

Link: https://lore.kernel.org/r/1589982799-28728-4-git-send-email-liweihang@huawei.comSigned-off-by: NLang Cheng <chenglang@huawei.com>
Signed-off-by: NWeihang Li <liweihang@huawei.com>
Signed-off-by: NJason Gunthorpe <jgg@mellanox.com>