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Date: Tue, 28 Jul 2020 18:34:01 +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 08/23] init: add an init_mount helper
Like do_mount, but takes a kernel pointer for the destination path.
Switch over the mounts in the init code and devtmpfs to it, which
just happen to work due to the implicit set_fs(KERNEL_DS) during early
init right now.
Signed-off-by: Christoph Hellwig <hch@....de>
---
drivers/base/devtmpfs.c | 5 +++--
fs/Makefile | 2 +-
fs/init.c | 25 +++++++++++++++++++++++++
fs/internal.h | 4 ++++
fs/namespace.c | 2 +-
include/linux/init_syscalls.h | 4 ++++
init/do_mounts.c | 8 ++++----
init/do_mounts.h | 1 +
init/do_mounts_initrd.c | 6 +++---
9 files changed, 46 insertions(+), 11 deletions(-)
create mode 100644 fs/init.c
create mode 100644 include/linux/init_syscalls.h
diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index d697634bc0d48c..32af6cb987b428 100644
--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c
@@ -25,6 +25,7 @@
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/kthread.h>
+#include <linux/init_syscalls.h>
#include <uapi/linux/mount.h>
#include "base.h"
@@ -359,7 +360,7 @@ int __init devtmpfs_mount(void)
if (!thread)
return 0;
- err = do_mount("devtmpfs", "dev", "devtmpfs", MS_SILENT, NULL);
+ err = init_mount("devtmpfs", "dev", "devtmpfs", MS_SILENT, NULL);
if (err)
printk(KERN_INFO "devtmpfs: error mounting %i\n", err);
else
@@ -408,7 +409,7 @@ static int __init devtmpfs_setup(void *p)
err = ksys_unshare(CLONE_NEWNS);
if (err)
goto out;
- err = do_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, NULL);
+ err = init_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, NULL);
if (err)
goto out;
ksys_chdir("/.."); /* will traverse into overmounted root */
diff --git a/fs/Makefile b/fs/Makefile
index 2ce5112b02c867..1c7b0e3f6daa11 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -13,7 +13,7 @@ obj-y := open.o read_write.o file_table.o super.o \
seq_file.o xattr.o libfs.o fs-writeback.o \
pnode.o splice.o sync.o utimes.o d_path.o \
stack.o fs_struct.o statfs.o fs_pin.o nsfs.o \
- fs_types.o fs_context.o fs_parser.o fsopen.o
+ fs_types.o fs_context.o fs_parser.o fsopen.o init.o
ifeq ($(CONFIG_BLOCK),y)
obj-y += buffer.o block_dev.o direct-io.o mpage.o
diff --git a/fs/init.c b/fs/init.c
new file mode 100644
index 00000000000000..c6eb724e1c7b22
--- /dev/null
+++ b/fs/init.c
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Routines that mimic syscalls, but don't use the user address space or file
+ * descriptors. Only for init/ and related early init code.
+ */
+#include <linux/init.h>
+#include <linux/mount.h>
+#include <linux/namei.h>
+#include <linux/fs.h>
+#include <linux/init_syscalls.h>
+#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)
+{
+ struct path path;
+ int ret;
+
+ ret = kern_path(dir_name, LOOKUP_FOLLOW, &path);
+ if (ret)
+ return ret;
+ ret = path_mount(dev_name, &path, type_page, flags, data_page);
+ path_put(&path);
+ return ret;
+}
diff --git a/fs/internal.h b/fs/internal.h
index e903d5aae139a2..72ea0b6f7435a4 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -89,6 +89,10 @@ extern int __mnt_want_write_file(struct file *);
extern void __mnt_drop_write_file(struct file *);
extern void dissolve_on_fput(struct vfsmount *);
+
+int path_mount(const char *dev_name, struct path *path,
+ const char *type_page, unsigned long flags, void *data_page);
+
/*
* fs_struct.c
*/
diff --git a/fs/namespace.c b/fs/namespace.c
index 43834b59eff6c3..2c4d7592097485 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3111,7 +3111,7 @@ char *copy_mount_string(const void __user *data)
* Therefore, if this magic number is present, it carries no information
* and must be discarded.
*/
-static int path_mount(const char *dev_name, struct path *path,
+int path_mount(const char *dev_name, struct path *path,
const char *type_page, unsigned long flags, void *data_page)
{
unsigned int mnt_flags = 0, sb_flags;
diff --git a/include/linux/init_syscalls.h b/include/linux/init_syscalls.h
new file mode 100644
index 00000000000000..af9ea88a60e0bd
--- /dev/null
+++ b/include/linux/init_syscalls.h
@@ -0,0 +1,4 @@
+/* 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);
diff --git a/init/do_mounts.c b/init/do_mounts.c
index a7f22cf58c7efd..83db87b6e5d1e0 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -395,16 +395,16 @@ static int __init do_mount_root(const char *name, const char *fs,
int ret;
if (data) {
- /* do_mount() requires a full page as fifth argument */
+ /* init_mount() requires a full page as fifth argument */
p = alloc_page(GFP_KERNEL);
if (!p)
return -ENOMEM;
data_page = page_address(p);
- /* zero-pad. do_mount() will make sure it's terminated */
+ /* zero-pad. init_mount() will make sure it's terminated */
strncpy(data_page, data, PAGE_SIZE);
}
- ret = do_mount(name, "/root", fs, flags, data_page);
+ ret = init_mount(name, "/root", fs, flags, data_page);
if (ret)
goto out;
@@ -628,7 +628,7 @@ void __init prepare_namespace(void)
mount_root();
out:
devtmpfs_mount();
- do_mount(".", "/", NULL, MS_MOVE, NULL);
+ init_mount(".", "/", NULL, MS_MOVE, NULL);
ksys_chroot(".");
}
diff --git a/init/do_mounts.h b/init/do_mounts.h
index 021e2f60223e25..20e7fec8cb499e 100644
--- a/init/do_mounts.h
+++ b/init/do_mounts.h
@@ -8,6 +8,7 @@
#include <linux/mount.h>
#include <linux/major.h>
#include <linux/root_dev.h>
+#include <linux/init_syscalls.h>
void mount_block_root(char *name, int flags);
void mount_root(void);
diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c
index e08669187d63be..1f9336209ad9cc 100644
--- a/init/do_mounts_initrd.c
+++ b/init/do_mounts_initrd.c
@@ -62,7 +62,7 @@ static int __init init_linuxrc(struct subprocess_info *info, struct cred *new)
console_on_rootfs();
/* move initrd over / and chdir/chroot in initrd root */
ksys_chdir("/root");
- do_mount(".", "/", NULL, MS_MOVE, NULL);
+ init_mount(".", "/", NULL, MS_MOVE, NULL);
ksys_chroot(".");
ksys_setsid();
return 0;
@@ -99,7 +99,7 @@ static void __init handle_initrd(void)
current->flags &= ~PF_FREEZER_SKIP;
/* move initrd to rootfs' /old */
- do_mount("..", ".", NULL, MS_MOVE, NULL);
+ init_mount("..", ".", NULL, MS_MOVE, NULL);
/* switch root and cwd back to / of rootfs */
ksys_chroot("..");
@@ -113,7 +113,7 @@ static void __init handle_initrd(void)
mount_root();
printk(KERN_NOTICE "Trying to move old root to /initrd ... ");
- error = do_mount("/old", "/root/initrd", NULL, MS_MOVE, NULL);
+ error = init_mount("/old", "/root/initrd", NULL, MS_MOVE, NULL);
if (!error)
printk("okay\n");
else {
--
2.27.0
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