On Fri, 31 Mar 2023 17:58:57 +0800 Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx> wrote: > In folio_batch_move_lru(), the folio_batch is not freshly > initialised, so it should call folio_batch_reinit() as > pagevec_lru_move_fn() did before. > > ... > > --- a/mm/swap.c > +++ b/mm/swap.c > @@ -222,7 +222,7 @@ static void folio_batch_move_lru(struct folio_batch *fbatch, move_fn_t move_fn) > if (lruvec) > unlock_page_lruvec_irqrestore(lruvec, flags); > folios_put(fbatch->folios, folio_batch_count(fbatch)); > - folio_batch_init(fbatch); > + folio_batch_reinit(fbatch); > } > > static void folio_batch_add_and_move(struct folio_batch *fbatch, Well... why? This could leave the kernel falsely thinking that the folio's pages have been drained from the per-cpu LRU addition magazines. Maybe that's desirable, maybe not, but I think this change needs much much more explanation describing why it is beneficial. folio_batch_reinit() seems to be a custom thing for the mlock code - perhaps it just shouldn't exist, and its operation should instead be open-coded in mlock_folio_batch(). The dynamics and rules around ->percpu_pvec_drained are a bit mysterious. A code comment which explains all of this would be useful.
