From: Al Viro Date: Thu, 3 Jul 2025 02:30:32 +0000 (-0400) Subject: better lockdep annotations for simple_recursive_removal() X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2a8061ee5e41034eb14170ec4517b5583dbeff9f;p=thirdparty%2Fkernel%2Fstable.git better lockdep annotations for simple_recursive_removal() We want a class that nests outside of I_MUTEX_NORMAL (for the sake of callbacks that might want to lock the victim) and inside I_MUTEX_PARENT (so that a variant of that could be used with parent of the victim held locked by the caller). In reality, simple_recursive_removal() * never holds two locks at once * holds the lock on parent of dentry passed to callback * is used only on the trees with fixed topology, so the depths are not changing. So the locking order is actually fine. AFAICS, the best solution is to assign I_MUTEX_CHILD to the locks grabbed by that thing. Reported-by: syzbot+169de184e9defe7fe709@syzkaller.appspotmail.com Signed-off-by: Al Viro --- diff --git a/fs/libfs.c b/fs/libfs.c index 42e226af6095a..20b05a6db7701 100644 --- a/fs/libfs.c +++ b/fs/libfs.c @@ -613,7 +613,7 @@ void simple_recursive_removal(struct dentry *dentry, struct dentry *victim = NULL, *child; struct inode *inode = this->d_inode; - inode_lock(inode); + inode_lock_nested(inode, I_MUTEX_CHILD); if (d_is_dir(this)) inode->i_flags |= S_DEAD; while ((child = find_next_child(this, victim)) == NULL) { @@ -625,7 +625,7 @@ void simple_recursive_removal(struct dentry *dentry, victim = this; this = this->d_parent; inode = this->d_inode; - inode_lock(inode); + inode_lock_nested(inode, I_MUTEX_CHILD); if (simple_positive(victim)) { d_invalidate(victim); // avoid lost mounts if (callback)