From 8271242be97498b40f49ece9202bf392df21ac29 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Thu, 30 Aug 2012 16:13:49 +0200 Subject: [PATCH 03/13] vfs: introduce clone_private_mount() Patch-mainline: not yet Overlayfs needs a private clone of the mount, so create a function for this and export to modules. Signed-off-by: Miklos Szeredi --- fs/namespace.c | 27 +++++++++++++++++++++++++++ include/linux/mount.h | 3 +++ 2 files changed, 30 insertions(+) --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1442,6 +1442,33 @@ void drop_collected_mounts(struct vfsmou namespace_unlock(); } +/** + * clone_private_mount - create a private clone of a path + * + * This creates a new vfsmount, which will be the clone of @path. The new will + * not be attached anywhere in the namespace and will be private (i.e. changes + * to the originating mount won't be propagated into this). + * + * Release with mntput(). + */ +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 (IS_ERR(new_mnt)) + return ERR_CAST(new_mnt); + + return &new_mnt->mnt; +} +EXPORT_SYMBOL_GPL(clone_private_mount); + int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg, struct vfsmount *root) { --- a/include/linux/mount.h +++ b/include/linux/mount.h @@ -68,6 +68,9 @@ 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,