[PATCH 03/13] vfs: introduce clone_private_mount()

Miklos Szeredi
2012-08-15T15:50:28Z

From: Miklos Szeredi <mszeredi@suse.cz>

Overlayfs needs a private clone of the mount, so create a function for
this and export to modules.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---
fs/namespace.c | 18 ++++++++++++++++++
include/linux/mount.h | 3 +++
2 files changed, 21 insertions(+), 0 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index 4d31f73..b4712ea 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1387,6 +1387,24 @@ void drop_collected_mounts(struct vfsmount *mnt)
release_mounts(&umount_list);
}

+struct vfsmount *clone_private_mount(struct path *path)
+{
+ struct mount *old_mnt = real_mount(path->mnt);
+ struct mount *new_mnt;
+
+ if (IS_MNT_UNBINDABLE(old_mnt))
+ return ERR_PTR(-EINVAL);
+
+ down_read(&namespace_sem);
+ new_mnt = clone_mnt(old_mnt, path->dentry, CL_PRIVATE);
+ up_read(&namespace_sem);
+ if (!new_mnt)
+ return ERR_PTR(-ENOMEM);
+
+ return &new_mnt->mnt;
+}
+EXPORT_SYMBOL_GPL(clone_private_mount);
+
int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
struct vfsmount *root)
{
diff --git a/include/linux/mount.h b/include/linux/mount.h
index d7029f4..344a262 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -66,6 +66,9 @@ extern void mnt_pin(struct vfsmount *mnt);
extern void mnt_unpin(struct vfsmount *mnt);
extern int __mnt_is_readonly(struct vfsmount *mnt);

+struct path;
+extern struct vfsmount *clone_private_mount(struct path *path);
+
struct file_system_type;
extern struct vfsmount *vfs_kern_mount(struct file_system_type *type,
int flags, const char *name,
--
1.7.7