linux-kernel - [RFC PATCH 1/3] fs/init: move creating the mount data_page into init

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Message-ID: <20260124003939.426931-2-hpa@zytor.com>
Date: Fri, 23 Jan 2026 16:39:34 -0800
From: "H. Peter Anvin" <hpa@...or.com>
To: Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
        Jonathan Corbet <corbet@....net>, "H. Peter Anvin" <hpa@...or.com>
Cc: linux-fsdevel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Lennart Poettering <lennart@...ttering.net>,
        systemd-devel@...ts.freedesktop.org
Subject: [RFC PATCH 1/3] fs/init: move creating the mount data_page into init_mount()

path_mount() wants the mount data if not NULL to be a whole
page. Expanding a string onto an allocated page was done in
do_mount_root(); move it instead into init_mount() so other users of
init_mount() can leverage this same code.

Signed-off-by: H. Peter Anvin (Intel) <hpa@...or.com>
---
 fs/init.c                     | 23 ++++++++++++++++++++---
 include/linux/init_syscalls.h |  3 ++-
 init/do_mounts.c              | 17 ++---------------
 3 files changed, 24 insertions(+), 19 deletions(-)

diff --git a/fs/init.c b/fs/init.c
index e0f5429c0a49..1253bcc73e26 100644
--- a/fs/init.c
+++ b/fs/init.c
@@ -14,16 +14,33 @@
 #include "internal.h"
 
 int __init init_mount(const char *dev_name, const char *dir_name,
-		const char *type_page, unsigned long flags, void *data_page)
+		      const char *type_page, unsigned long flags,
+		      const char *data_str)
 {
+	struct page *data_page = NULL;
+	char *data_buf = NULL;
 	struct path path;
 	int ret;
 
+	/* path_mount() wants a proper page for data */
+	if (data_str && data_str[0]) {
+		data_page = alloc_page(GFP_KERNEL);
+		if (!data_page)
+			return -ENOMEM;
+		data_buf = page_address(data_page);
+		strscpy_pad(data_buf, data_str, PAGE_SIZE);
+	}
+
 	ret = kern_path(dir_name, LOOKUP_FOLLOW, &path);
 	if (ret)
-		return ret;
-	ret = path_mount(dev_name, &path, type_page, flags, data_page);
+		goto out;
+
+	ret = path_mount(dev_name, &path, type_page, flags, data_buf);
 	path_put(&path);
+
+out:
+	if (data_page)
+		put_page(data_page);
 	return ret;
 }
 
diff --git a/include/linux/init_syscalls.h b/include/linux/init_syscalls.h
index 92045d18cbfc..804d3070ce73 100644
--- a/include/linux/init_syscalls.h
+++ b/include/linux/init_syscalls.h
@@ -1,7 +1,8 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 
 int __init init_mount(const char *dev_name, const char *dir_name,
-		const char *type_page, unsigned long flags, void *data_page);
+		      const char *type_page, unsigned long flags,
+		      const char *data_str);
 int __init init_umount(const char *name, int flags);
 int __init init_chdir(const char *filename);
 int __init init_chroot(const char *filename);
diff --git a/init/do_mounts.c b/init/do_mounts.c
index defbbf1d55f7..87cf110a48e6 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -147,23 +147,12 @@ static int __init split_fs_names(char *page, size_t size)
 }
 
 static int __init do_mount_root(const char *name, const char *fs,
-				 const int flags, const void *data)
+				 const int flags, const char *data)
 {
 	struct super_block *s;
-	struct page *p = NULL;
-	char *data_page = NULL;
 	int ret;
 
-	if (data) {
-		/* init_mount() requires a full page as fifth argument */
-		p = alloc_page(GFP_KERNEL);
-		if (!p)
-			return -ENOMEM;
-		data_page = page_address(p);
-		strscpy_pad(data_page, data, PAGE_SIZE);
-	}
-
-	ret = init_mount(name, "/root", fs, flags, data_page);
+	ret = init_mount(name, "/root", fs, flags, data);
 	if (ret)
 		goto out;
 
@@ -177,8 +166,6 @@ static int __init do_mount_root(const char *name, const char *fs,
 	       MAJOR(ROOT_DEV), MINOR(ROOT_DEV));
 
 out:
-	if (p)
-		put_page(p);
 	return ret;
 }
 
-- 
2.52.0