io_uring: clamp to_submit in io_submit_sqes()

mainline inclusion
from mainline-5.6-rc1
commit 9ef4f124
category: feature
bugzilla: https://bugzilla.openeuler.org/show_bug.cgi?id=27
CVE: NA
---------------------------

Make io_submit_sqes() to clamp @to_submit itself. It removes duplicated
code and prepares for following changes.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Conflicts
	fs/io_uring.c
[conflicts with 73e08e71(Revert "io_uring: only allow submit
 from owning task")]
Signed-off-by: Nyangerkun <yangerkun@huawei.com>
Signed-off-by: Nyangerkun <yangerkun@huawei.com>
Reviewed-by: Nzhangyi (F) <yi.zhang@huawei.com>
Signed-off-by: NCheng Jian <cj.chengjian@huawei.com>

fs/io_uring.c

@@ -4574,6 +4574,8 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr,
 			return -EBUSY;
 	}
 
+	nr = min(nr, ctx->sq_entries);
+
 	if (!percpu_ref_tryget_many(&ctx->refs, nr))
 		return -EAGAIN;
 
@@ -4748,7 +4750,6 @@ static int io_sq_thread(void *data)
 			ctx->rings->sq_flags &= ~IORING_SQ_NEED_WAKEUP;
 		}
 
-		to_submit = min(to_submit, ctx->sq_entries);
 		mutex_lock(&ctx->uring_lock);
 		ret = io_submit_sqes(ctx, to_submit, NULL, -1, &cur_mm, true);
 		mutex_unlock(&ctx->uring_lock);
@@ -6088,7 +6089,6 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
 	} else if (to_submit) {
 		struct mm_struct *cur_mm;
 
-		to_submit = min(to_submit, ctx->sq_entries);
 		mutex_lock(&ctx->uring_lock);
 		/* already have mm, so io_submit_sqes() won't try to grab it */
 		cur_mm = ctx->sqo_mm;