linux-kernel - [PATCH 23/23] init: add an init

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Date:   Tue, 28 Jul 2020 18:34:16 +0200
From:   Christoph Hellwig <hch@....de>
To:     Al Viro <viro@...iv.linux.org.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-api@...r.kernel.org
Subject: [PATCH 23/23] init: add an init_dup helper

Add a simple helper to grab a reference to a file and install it at
the next available fd, and switch the early init code over to it.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 fs/init.c                     | 12 ++++++++++++
 include/linux/init_syscalls.h |  1 +
 init/main.c                   |  7 +++----
 3 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/fs/init.c b/fs/init.c
index db5c48a85644fa..730e05acda2392 100644
--- a/fs/init.c
+++ b/fs/init.c
@@ -8,6 +8,7 @@
 #include <linux/namei.h>
 #include <linux/fs.h>
 #include <linux/fs_struct.h>
+#include <linux/file.h>
 #include <linux/init_syscalls.h>
 #include <linux/security.h>
 #include "internal.h"
@@ -251,3 +252,14 @@ int __init init_utimes(char *filename, struct timespec64 *ts)
 	path_put(&path);
 	return error;
 }
+
+int __init init_dup(struct file *file)
+{
+	int fd;
+
+	fd = get_unused_fd_flags(0);
+	if (fd < 0)
+		return fd;
+	fd_install(get_unused_fd_flags(0), get_file(file));
+	return 0;
+}
diff --git a/include/linux/init_syscalls.h b/include/linux/init_syscalls.h
index 3654b525ac0b17..92045d18cbfc99 100644
--- a/include/linux/init_syscalls.h
+++ b/include/linux/init_syscalls.h
@@ -16,3 +16,4 @@ int __init init_unlink(const char *pathname);
 int __init init_mkdir(const char *pathname, umode_t mode);
 int __init init_rmdir(const char *pathname);
 int __init init_utimes(char *filename, struct timespec64 *ts);
+int __init init_dup(struct file *file);
diff --git a/init/main.c b/init/main.c
index 1c710d3e1d461a..089e21504b1fc1 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1467,10 +1467,9 @@ void __init console_on_rootfs(void)
 		pr_err("Warning: unable to open an initial console.\n");
 		return;
 	}
-	get_file_rcu_many(file, 2);
-	fd_install(get_unused_fd_flags(0), file);
-	fd_install(get_unused_fd_flags(0), file);
-	fd_install(get_unused_fd_flags(0), file);
+	init_dup(file);
+	init_dup(file);
+	init_dup(file);
 }
 
 static noinline void __init kernel_init_freeable(void)
-- 
2.27.0