On Thu, Nov 09, 2023 at 06:20:49AM +0000, Al Viro wrote: > Instead of bumping it from 0 to 1, calling retain_dentry(), then > decrementing it back to 0 (with ->d_lock held all the way through), > just leave refcount at 0 through all of that. > > It will have a visible effect for ->d_delete() - now it can be > called with refcount 0 instead of 1 and it can no longer play > silly buggers with dropping/regaining ->d_lock. Not that any > in-tree instances tried to (it's pretty hard to get right). > > Any out-of-tree ones will have to adjust (assuming they need any > changes). > > Note that we do not need to extend rcu-critical area here - we have > verified that refcount is non-negative after having grabbed ->d_lock, > so nobody will be able to free dentry until they get into __dentry_kill(), > which won't happen until they manage to grab ->d_lock. > > Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx> > --- Looks good to me, Reviewed-by: Christian Brauner <brauner@xxxxxxxxxx>
