linux-kernel - [PATCH] fs: tidy up do_sys_openat2() with likely/unlikely

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Message-ID: <20250320092331.1921700-1-mjguzik@gmail.com>
Date: Thu, 20 Mar 2025 10:23:31 +0100
From: Mateusz Guzik <mjguzik@...il.com>
To: brauner@...nel.org
Cc: viro@...iv.linux.org.uk,
	jack@...e.cz,
	linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	Mateusz Guzik <mjguzik@...il.com>
Subject: [PATCH] fs: tidy up do_sys_openat2() with likely/unlikely

Otherwise gcc 13 generates conditional forward jumps (aka branch
mispredict by default) for build_open_flags() being succesfull.

Signed-off-by: Mateusz Guzik <mjguzik@...il.com>
---

maybe i'll get around to do it a full pass instead of sending byte-sized
patchen. someone(tm) should definitely do it.

 fs/open.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/fs/open.c b/fs/open.c
index bdbf03f799a1..a9063cca9911 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -1413,18 +1413,19 @@ static int do_sys_openat2(int dfd, const char __user *filename,
 			  struct open_how *how)
 {
 	struct open_flags op;
-	int fd = build_open_flags(how, &op);
 	struct filename *tmp;
+	int err, fd;
 
-	if (fd)
-		return fd;
+	err = build_open_flags(how, &op);
+	if (unlikely(err))
+		return err;
 
 	tmp = getname(filename);
 	if (IS_ERR(tmp))
 		return PTR_ERR(tmp);
 
 	fd = get_unused_fd_flags(how->flags);
-	if (fd >= 0) {
+	if (likely(fd >= 0)) {
 		struct file *f = do_filp_open(dfd, tmp, &op);
 		if (IS_ERR(f)) {
 			put_unused_fd(fd);
-- 
2.43.0