linux-kernel - [PATCH 2/3] fork: use pidfd

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Message-Id: <20230327-pidfd-file-api-v1-2-5c0e9a3158e4@kernel.org>
Date:   Mon, 27 Mar 2023 20:22:52 +0200
From:   Christian Brauner <brauner@...nel.org>
To:     linux-fsdevel@...r.kernel.org
Cc:     Jan Kara <jack@...e.cz>, Amir Goldstein <amir73il@...il.com>,
        Matthew Bobrowski <repnop@...gle.com>,
        linux-kernel@...r.kernel.org,
        Christian Brauner <brauner@...nel.org>
Subject: [PATCH 2/3] fork: use pidfd_prepare()

Stop open-coding get_unused_fd_flags() and anon_inode_getfile(). That's
brittle just for keeping the flags between both calls in sync. Use the
dedicated helper.

Signed-off-by: Christian Brauner <brauner@...nel.org>
---
 kernel/fork.c | 12 +-----------
 1 file changed, 1 insertion(+), 11 deletions(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index c0257cbee093..1f5eb854ba3e 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2291,21 +2291,11 @@ static __latent_entropy struct task_struct *copy_process(
 	 * if the fd table isn't shared).
 	 */
 	if (clone_flags & CLONE_PIDFD) {
-		retval = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
+		retval = pidfd_prepare(pid, O_RDWR | O_CLOEXEC, &pidfile);
 		if (retval < 0)
 			goto bad_fork_free_pid;
-
 		pidfd = retval;
 
-		pidfile = anon_inode_getfile("[pidfd]", &pidfd_fops, pid,
-					      O_RDWR | O_CLOEXEC);
-		if (IS_ERR(pidfile)) {
-			put_unused_fd(pidfd);
-			retval = PTR_ERR(pidfile);
-			goto bad_fork_free_pid;
-		}
-		get_pid(pid);	/* held by pidfile now */
-
 		retval = put_user(pidfd, args->pidfd);
 		if (retval)
 			goto bad_fork_put_pidfd;

-- 
2.34.1