[PATCH] io_uring: reduce one unnecessary io_sqring_entries() call

From: Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com>
To: io-uring@vger.kernel.org
Cc: axboe@kernel.dk, asml.silence@gmail.com, joseph.qi@linux.alibaba.com
Subject: [PATCH] io_uring: reduce one unnecessary io_sqring_entries() call
Date: Fri,  8 Jan 2021 16:36:23 +0800	[thread overview]
Message-ID: <20210108083623.26400-1-xiaoguang.wang@linux.alibaba.com> (raw)

In __io_sq_thread(), we have gotten the number of sqes to submit,
then in io_submit_sqes(), we can use this number directly, no need
to call io_sqring_entries() again in io_submit_sqes().

Signed-off-by: Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com>
---
 fs/io_uring.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index ca46f314640b..200a9eb72788 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6830,9 +6830,6 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr)
 			return -EBUSY;
 	}
 
-	/* make sure SQ entry isn't read before tail */
-	nr = min3(nr, ctx->sq_entries, io_sqring_entries(ctx));
-
 	if (!percpu_ref_tryget_many(&ctx->refs, nr))
 		return -EAGAIN;
 
@@ -9211,6 +9208,8 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
 		if (unlikely(ret))
 			goto out;
 		mutex_lock(&ctx->uring_lock);
+		/* make sure SQ entry isn't read before tail */
+		to_submit = min3(to_submit, ctx->sq_entries, io_sqring_entries(ctx));
 		submitted = io_submit_sqes(ctx, to_submit);
 		mutex_unlock(&ctx->uring_lock);
 
-- 
2.17.2

