Lockdep reports recursive locking warnings in `incfs_setattr` and
`iterate_dir`. Because IncFS is a stacked filesystem, these operations
re-enter VFS on the backing (lower) directory or file, calling
VFS helpers or locking the lower inode directly.
Since VFS acquires the upper inode's `i_rwsem` with subclass 0, the
unannotated re-entry into the lower inode (which also uses subclass 0)
falsely triggers lockdep's recursive lock detection.
Fix this by annotating the lower inode acquisitions with the
`I_MUTEX_PARENT` subclass:
1. In `incfs_setattr`, use `inode_lock_nested(..., I_MUTEX_PARENT)`
consistently with all other directory operations in this file.
2. In `iterate_incfs_dir`, temporarily set the backing inode's
lock class subclass to `I_MUTEX_PARENT` around the `iterate_dir()`
VFS helper call, and restore it to 0 immediately afterwards.
Bug: 419203261
Bug: 419264069
Change-Id: I0447aa79f91576b67290eadf143acfb87d8cb9b4
Signed-off-by: Howard Chen <howardsoc@google.com>
Howard Chen
59b735704e