On Tue, Aug 30, 2022 at 01:12:53PM -0700, John Hubbard wrote: > As long as we continue to sort-of-accidentally use atomic_add_unless(), > which returns a value, instead of atomic_add(), which does not. :) I should say I didn't have time to carefully check what put_page was doing, but IIRC it is an atomic_dec_return to decide if it should free the page. The conditional is pretty much inherent to the model, because 0 is special it always has to be checked. Not so accidental But you might make the case that these could be the relaxed versions of the atomic... > Likewise on the put_page() side: we are depending on the somewhat > accidental (from the perspective of memory barriers) use of > atomics that return values. > > Maybe it would be good to add a little note at each site, to that > effect? It would be fantastic if things that are required to be acquire/releases are documented as acquire/release :) It is incredibly subtle stuff and all carefully inlined for maximum performance. Jason
