mainline inclusion
from mainline-5.6-rc1
commit ee7d46d9
category: feature
bugzilla: https://bugzilla.openeuler.org/show_bug.cgi?id=27
CVE: NA
---------------------------

A user may ask to submit more than there is in the ring, and then
io_uring will submit as much as it can. However, in the last iteration
it will allocate an io_kiocb and immediately free it. It could do
better and adjust @to_submit to what is in the ring.

And since the ring's head is already checked here, there is no need to
do it in the loop, spamming with smp_load_acquire()'s barriers
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
Signed-off-by: Nyangerkun <yangerkun@huawei.com>
Reviewed-by: Nzhangyi (F) <yi.zhang@huawei.com>
Signed-off-by: NCheng Jian <cj.chengjian@huawei.com>