On Sun, Jun 18, 2023 at 9:29 PM Huang, Ying <ying.huang@xxxxxxxxx> wrote: > > Yosry Ahmed <yosryahmed@xxxxxxxxxx> writes: > > > On Sun, Jun 18, 2023 at 7:00 PM Huang, Ying <ying.huang@xxxxxxxxx> wrote: > >> > >> Hi, Yosry, > >> > >> Yosry Ahmed <yosryahmed@xxxxxxxxxx> writes: > >> > >> > This reverts commit c3096e6782b733158bf34f6bbb4567808d4e0740. > >> > > >> > That commit made sure we immediately add the new page to the LRU before > >> > remove_migration_ptes() is called in migrate_move_folio() (used to be > >> > __unmap_and_move() back then), such that the rmap walk will rebuild the > >> > correct mlock_count for the page again. This was needed because the > >> > mlock_count was lost when the page is isolated. This is no longer the > >> > case since mlock_count no longer overlays page->lru. > >> > > >> > Revert the commit (the code was foliated afterward the commit, so the > >> > revert is updated as such). > >> > > >> > Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx> > >> > --- > >> > mm/migrate.c | 24 +++++++++--------------- > >> > 1 file changed, 9 insertions(+), 15 deletions(-) > >> > > >> > diff --git a/mm/migrate.c b/mm/migrate.c > >> > index 01cac26a3127..68f693731865 100644 > >> > --- a/mm/migrate.c > >> > +++ b/mm/migrate.c > >> > @@ -1279,19 +1279,6 @@ static int migrate_folio_move(free_page_t put_new_page, unsigned long private, > >> > if (unlikely(!is_lru)) > >> > goto out_unlock_both; > >> > >> The patch itself looks good to me! Thanks! > >> > >> Reviewed-by: "Huang, Ying" <ying.huang@xxxxxxxxx> > > > > Thanks for taking a look! > > > >> > >> And, it seems that we can remove the above 2 lines and "out_unlock_both" > >> label now. That can make the code simpler a little. Right? > > > > I am not familiar with this code. If we remove the above condition > > then pages that have is_lru == 0 (i.e __PageMovable(src) is true) and > > page_was_mapped == 1 will call remove_migration_ptes(). This wouldn't > > happen without removing the above 2 lines. If this combination is > > impossible (is_lru == 0 && page_was_mapped == 1), then yeah we can > > remove the above condition. > > > > It looks like __SetPageMovable() is only called by zsmalloc, z3fold, > > and balloon_page_insert(). The former 2 will never have those pages > > mapped into userspace. I am not familiar with balloon_page_insert(), > > but my gut feeling is that those are pages used by the driver and are > > also not mapped into userspace. > > You can take a look at migrate_folio_unmap(), where "page_was_mapped" > will not be set to 1 if !is_lru. Oh I was looking in the wrong place huh, thanks. Will remove it when I respin! > > Best Regards, > Huang, Ying > > > So I guess we can just remove the condition, but a confirmation for > > the above would be reassuring :) > > > >> > >> Best Regards, > >> Huang, Ying > >> > >> > - /* > >> > - * When successful, push dst to LRU immediately: so that if it > >> > - * turns out to be an mlocked page, remove_migration_ptes() will > >> > - * automatically build up the correct dst->mlock_count for it. > >> > - * > >> > - * We would like to do something similar for the old page, when > >> > - * unsuccessful, and other cases when a page has been temporarily > >> > - * isolated from the unevictable LRU: but this case is the easiest. > >> > - */ > >> > - folio_add_lru(dst); > >> > - if (page_was_mapped) > >> > - lru_add_drain(); > >> > - > >> > if (page_was_mapped) > >> > remove_migration_ptes(src, dst, false); > >> > > >> > @@ -1301,9 +1288,16 @@ static int migrate_folio_move(free_page_t put_new_page, unsigned long private, > >> > /* > >> > * If migration is successful, decrease refcount of dst, > >> > * which will not free the page because new page owner increased > >> > - * refcounter. > >> > + * refcounter. As well, if it is LRU folio, add the folio to LRU > >> > + * list in here. Use the old state of the isolated source folio to > >> > + * determine if we migrated a LRU folio. dst was already unlocked > >> > + * and possibly modified by its owner - don't rely on the folio > >> > + * state. > >> > */ > >> > - folio_put(dst); > >> > + if (unlikely(!is_lru)) > >> > + folio_put(dst); > >> > + else > >> > + folio_putback_lru(dst); > >> > > >> > /* > >> > * A folio that has been migrated has all references removed > >> >
