On Fri, Sep 27, 2024 at 08:48:14AM GMT, Herbert Xu wrote: > On Tue, Sep 24, 2024 at 10:48:07PM -0400, Kent Overstreet wrote: > > > > I've been noticing rhashtable resize is surprisingly heavy (the default > > parameters don't ever shrink the table, which is why it's not seen as > > much). > > Most rhashtable users enable automatic shrinking. > > > And, when I was torture testing that code I tripped over what appeared > > to be an infinite loop in rht_bucket() when a rehsah is in progress, > > which I worked around in > > > > a592cdf5164d bcachefs: don't use rht_bucket() in btree_key_cache_scan() > > You must not walk the rhashtable internal data structures by hand. > If you need to iterate through the whole table, use the provided > walking mechanism. I was just doing rht_for_each_entry_rcu() (open coded because you don't provide a safe version). > However, as rhashtable is dynamic, walking it during a resize may > cause you to see some elements twice. If you want to avoid that, > set up your own linked list of all elements for a completely stable > walk. Yeah that's fine, but like I said, I was seeing an infinite loop inside rht_bucket(). That would be an rhashtable bug...
