b1eaa950f7
An overlayfs instance can be the lower layer of another overlayfs instance. This setup triggers a lockdep splat of possible recursive locking of sb->s_type->i_mutex_key in iterate_dir(). Trimmed snip: [ INFO: possible recursive locking detected ] bash/2468 is trying to acquire lock: &sb->s_type->i_mutex_key#14, at: iterate_dir+0x7d/0x15c but task is already holding lock: &sb->s_type->i_mutex_key#14, at: iterate_dir+0x7d/0x15c One problem observed with this splat is that ovl_new_inode() does not call lockdep_annotate_inode_mutex_key() to annotate the dir inode lock as &sb->s_type->i_mutex_dir_key like other fs do. The other problem is that the 2 nested levels of overlayfs inode lock are annotated using the same key, which is the cause of the false positive lockdep warning. Fix this by annotating overlayfs inode lock in ovl_fill_inode() according to stack level of the super block instance and use different key for dir vs. non-dir like other fs do. Here is an edited snip from /proc/lockdep_chains after iterate_dir() of nested overlayfs: [...] &ovl_i_mutex_dir_key[depth] (stack_depth=2) [...] &ovl_i_mutex_dir_key[depth]#2 (stack_depth=1) [...] &type->i_mutex_dir_key (stack_depth=0) Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.