Quoting Seth Forshee ([email protected]): > Starting with 4.1 the tracing subsystem has its own filesystem > which is automounted in the tracing subdirectory of debugfs. > Prior to this debugfs could be bind mounted in a cloned mount > namespace, but if tracefs has been mounted under debugfs this > now fails because there is a locked child mount. This creates > a regression for container software which bind mounts debugfs > to satisfy the assumption of some userspace software. > > In other pseudo filesystems such as proc and sysfs we're already > creating mountpoints like this in such a way that no dirents can > be created in the directories, allowing them to be exceptions to > some MNT_LOCKED tests. In fact we're already do this for the > tracefs mountpoint in sysfs. > > Do the same in debugfs_create_automount(), since the intention > here is clearly to create a mountpoint. This fixes the regression, > as locked child mounts on permanently empty directories do not > cause a bind mount to fail. > > Cc: [email protected] # v4.1+ > Signed-off-by: Seth Forshee <[email protected]>
Acked-by: Serge Hallyn <[email protected]> > --- > fs/debugfs/inode.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c > index bece948b363d..8580831ed237 100644 > --- a/fs/debugfs/inode.c > +++ b/fs/debugfs/inode.c > @@ -457,7 +457,7 @@ struct dentry *debugfs_create_automount(const char *name, > if (unlikely(!inode)) > return failed_creating(dentry); > > - inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO; > + make_empty_dir_inode(inode); > inode->i_flags |= S_AUTOMOUNT; > inode->i_private = data; > dentry->d_fsdata = (void *)f; > -- > 1.9.1
