linux-kernel - [PATCH v1] fs/io_uring: Prioritise checking faster conditions first in io

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Date:   Sat, 16 Oct 2021 20:32:29 -0500
From:   Noah Goldstein <goldstein.w.n@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     goldstein.w.n@...il.com, axboe@...nel.dk, asml.silence@...il.com,
        io-uring@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1] fs/io_uring: Prioritise checking faster conditions first in io_write

This commit reorders the conditions in a branch in io_write. The
reorder to check 'ret2 == -EAGAIN' first as checking
'(req->ctx->flags & IORING_SETUP_IOPOLL)' will likely be more
expensive due to 2x memory derefences.

Signed-off-by: Noah Goldstein <goldstein.w.n@...il.com>
---
 fs/io_uring.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 6b9e70208782..321de7ddf2cf 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3660,7 +3660,7 @@ static int io_write(struct io_kiocb *req, unsigned int issue_flags)
 		goto done;
 	if (!force_nonblock || ret2 != -EAGAIN) {
 		/* IOPOLL retry should happen for io-wq threads */
-		if ((req->ctx->flags & IORING_SETUP_IOPOLL) && ret2 == -EAGAIN)
+		if (ret2 == -EAGAIN && (req->ctx->flags & IORING_SETUP_IOPOLL))
 			goto copy_iov;
 done:
 		kiocb_done(kiocb, ret2, issue_flags);
-- 
2.25.1