io_uring: don't keep looping for more events if we can't flush overflow

mainline inclusion
from mainline-v5.12-rc1
commit ca0a2651
category: bugfix
bugzilla: 186454,https://gitee.com/openeuler/kernel/issues/I5026G
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ca0a26511c679a797f86589894a4523db36d833e



--------------------------------

It doesn't make sense to wait for more events to come in, if we can't
even flush the overflow we already have to the ring. Return -EBUSY for
that condition, just like we do for attempts to submit with overflow
pending.

Cc: stable@vger.kernel.org # 5.11
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Conflicts:
        fs/io_uring.c
Signed-off-by: Guo Xuenan <guoxuenan@huawei.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>