On Sun, Mar 10, 2024 at 11:01:06AM +0000, Ryan Roberts wrote: > > So after my patch, instead of calling (in order): > > > > page_cache_release(folio); > > folio_undo_large_rmappable(folio); > > mem_cgroup_uncharge(folio); > > free_unref_page() > > > > it calls: > > > > __page_cache_release(folio, &lruvec, &flags); > > mem_cgroup_uncharge_folios() > > folio_undo_large_rmappable(folio); > > I was just looking at this again, and something pops out... > > You have swapped the order of folio_undo_large_rmappable() and > mem_cgroup_uncharge(). But folio_undo_large_rmappable() calls > get_deferred_split_queue() which tries to get the split queue from > folio_memcg(folio) first and falls back to pgdat otherwise. If you are now > calling mem_cgroup_uncharge_folios() first, will that remove the folio from the > cgroup? Then we are operating on the wrong list? (just a guess based on the name > of the function...) Oh my. You've got it. This explains everything. Thank you!
