On Sat, Feb 08, 2025 at 01:30:43AM +0000, Al Viro wrote: > HOWEVER, if you do not bother with doing that before ->d_unalias_trylock() > (and there's no reason to do that), the whole thing becomes much simpler - > you can do the check inside __d_move(), after all locks had been taken. > > After > spin_lock_nested(&dentry->d_lock, 2); > spin_lock_nested(&target->d_lock, 3); > you have everything stable. Just make the sucker return bool instead > of void, check that crap and have it return false if there's a problem. ... except that this requires telling __d_move() that it's an unalias - on normal move dentries will have been locked by the caller. Might make sense to turn that bool exchange argument into an enum... Let me play with that a bit and see what falls out...
