From: Miklos Szeredi <mszeredi@xxxxxxx>
Overlayfs needs a private clone of the mount, so create a function for
this and export to modules.
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
---
fs/namespace.c | 27 +++++++++++++++++++++++++++
include/linux/mount.h | 3 +++
2 files changed, 30 insertions(+)
diff --git a/fs/namespace.c b/fs/namespace.c
index 182bc41cd887..9ad57948f527 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1550,6 +1550,33 @@ void drop_collected_mounts(struct vfsmount *mnt)
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)
{
diff --git a/include/linux/mount.h b/include/linux/mount.h
index 839bac270904..31617fcfac8c 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -74,6 +74,9 @@ 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,
--
1.8.1.4
--
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